A Comprehensive Review on the Valorization of Agricultural By-products for Sustainable Ruminant Production in Nigeria

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Bello, Abdulmalik O. Abdulwasiu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8912667/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Agricultural by-products and residues in Nigeria are a huge untapped resource that has the potential to improve sustainable ruminant production and reduce environmental pollution. This review aims to compile the latest developments in the utilization of different agricultural by-products such as maize husks, rice straw, cassava peels, groundnut husks, and sugarcane bagasse, based on their proximate composition, nutritional value, and potential use as feed supplements. The review discusses the valorization of these agricultural by-products as a sustainable approach for improving ruminant production in Nigeria. The review also discusses the recent biotechnological and nanotechnological approaches for upgrading agro-waste into value-added products for improving feed efficiency, animal health, and production sustainability. We synthesize the existing literature to compile the major by-products available in Nigeria and processing by-products account for their nutritional composition, availability, and disposal. The paper critically reviews different valorization approaches, such as physical, chemical, and biological processes to improve the nutritional value and palatability of these fibrous materials. In addition, we review the effects of supplementing these processed and unprocessed by-products to ruminants on feed intake, digestibility, growth, and milk production. Challenges such as infrastructural deficiencies, policy, and research investment that limit effective valorization in Nigeria are also reviewed. The review concludes that the valorization of agricultural by-products is a viable, sustainable, and economically sound approach to address feed insecurity, environmental waste, and the sustainability of the ruminant production system in Nigeria. This synthesis offers a contemporary knowledge base to guide researchers, policymakers, and stakeholders in optimizing agricultural by-product utilization for sustainable ruminant production in Nigeria. Agricultural Economics & Policy Valorization Agricultural waste Sustainability 1.0 INTRODUCTION The ruminant sub-sector is a major contributor to the Nigerian agricultural economy, with a projected 22.1 million cattle, 52.0 million goats, and 47.7 million sheep (FAO, 2023 ). The ruminant sub-sector is mainly raised through pastoral and extensive grazing systems. Despite the large number of ruminants, the productivity level of the sub-sector is sub-optimal and cannot meet the domestic demand for meat and milk. The major constraint to the intensive production of ruminants is the acute and perennial shortage of quality feed, especially during the dry season (Mustapha et al., 2024 ). The by-products have high potential as sustainable feed materials due to their abundance and nutritional value, providing an eco-friendly and cheap alternative to conventional feed materials (Adeyemo et al., 2025 ). The livestock sector is a major component of the Nigerian agricultural economy and is a significant source of livelihood for millions of Nigerians and a major source of protein, income, and draft power (National Bureau of Statistics, 2022 ).. The dependence on conventional feed materials such as grown forages and grain-based concentrates is economically irrational because of their high cost, which accounts for over 70% of the total production cost, and because they directly compete with human food requirements (Babatunde et al., 2021 ). The cost of feed crisis thus creates a vicious cycle of low productivity, poverty among livestock producers, and increased food insecurity. Agricultural wastes, which are non-product outputs from crop production, processing, livestock, and aquaculture, are generated mainly from intensive agricultural practices and the overuse of chemicals. (Obi et al. 2016 ). The processing of these crops generates a substantial quantity of biomass materials such as cereal straws, legume husks, tuber peels, and fruit pulps. According to a study, the present ways of disposing of these agricultural wastes are inefficient and harmful to the environment, including open-field burning, dumping into water bodies, or uncontrolled decomposition, which are sources of greenhouse gas emissions, soil degradation, and water pollution (Oguntade et al., 2022 ). This is a serious lost opportunity, as this "waste" has a substantial potential use as an alternative feed material. This state of affairs is a major missed opportunity, as this "waste" material has a lot of potential as an alternative feed material. The biomass valorization system provides a solution to the dual problem of feed security and agricultural waste pollution. Valorization is defined as the transformation of low-value by-products into higher-value materials or products. In ruminant nutrition, this entails the processing and utilization of lignocellulosic agricultural waste as animal feed (Sadh et al., 2018 ). This strategy is a real-world application of the circular bioeconomy model, which seeks to eliminate waste and maximize resource use by creating a closed-loop system. Rather than a linear "take-make-dispose" system, agricultural waste is "re-circulated" back into the production system as a valuable resource, thereby lowering the environmental impact of crop and livestock production while improving economic returns for farmers (Akinfemi & Adebayo, 2020 ). Taking into consideration the critical challenges facing the Nigerian livestock industry and the simultaneous opportunity presented by the abundance of agricultural waste, this comprehensive review is designed with specific objectives in mind. It seeks to systematically compile the major agricultural by-products produced in Nigeria, describing their nutritional content and availability for ruminant feeding. The review will also critically assess the effectiveness of different physical, chemical, and biological valorization methods in improving the nutritional potential of these lignocellulosic materials. A major thrust of this review will be to integrate existing knowledge on the effects of feeding these valorized by-products to ruminants, with respect to parameters like feed intake, digestibility of nutrients, growth rate of the animals, and ruminal methane emissions. In addition to the scientific knowledge, this paper will also attempt to list the major socio-economic, technical, and policy-related factors that currently limit the adoption of these sustainable feeding practices. Finally, on the basis of the synthesized knowledge, the review will make recommendations for future research and development and policy actions that would be required for the complete integration of agricultural by-product valorization into Nigeria's plan for a sustainable and secure ruminant production system. The focus of this study is specifically limited to ruminants and the most common crop residues in Nigeria. 2.0 Systematic Literature Search Strategy and Databases Used A systematic literature search was conducted to identify relevant peer-reviewed articles, reports, and theses published from 2015 to 2025. The search was performed across multiple electronic databases including Scopus, Web of Science, PubMed, ScienceDirect, and Google Scholar. Key search terms and Boolean operators were employed to maximize the retrieval of relevant studies. Additional sources included Nigerian university repositories and institutional reports to capture relevant regional studies. Search terms combined keywords related to agricultural by-products, crop residues, ruminant nutrition, feed valorization, and Nigeria (e.g., "agro-industrial by-products," "crop residues," "ruminant feed," "Nigeria"). The search was limited to articles published in English, with a primary focus on literature from the year 2000 to the present to capture contemporary practices, though seminal earlier works were not excluded. Inclusion and Exclusion Criteria for Studies Studies were included if they conducted within Nigeria or utilizing agricultural by-products sourced from Nigeria; assessed these wastes as feed resources or valorization strategies for ruminant animals; provided original research data or comprehensive reviews; and were published in English within the specified date range. Studies that did not provide specific data on the by-product or the outcomes of interest or focusing exclusively on non-ruminant species, inorganic pollutant valorization, or off-topic agricultural intervention were excluded. Grey literature and conference abstracts without full methods or results were also excluded to ensure quality. Studies were screened against predefined criteria to determine their eligibility for inclusion in this review. Quality Assessment of Included Studies A systematic review methodology was employed. Following the search and screening, the methodological quality of included studies was assessed using a modified version of the Newcastle-Ottawa scale adapted for animal nutrition studies. Criteria included clarity of objectives, appropriateness of experimental design, sample size sufficiency, reproducibility of methods, and robustness of data analysis. Studies scoring below a predefined threshold were excluded from final synthesis to ensure reliability and reduce bias. Relevant data extracted from eligible studies included by-product type, pretreatment or processing methods, proximate composition, nutritional evaluations, feeding trials outcomes, and production performance metrics. Data were tabulated and synthesized qualitatively to identify common themes, emerging trends, technological advancements, and gaps in knowledge. Where sufficient quantitative data were available (nutrient content, feed conversion ratios, weight gains), meta-analytic techniques were considered although heterogeneity mostly warranted a narrative synthesis approach. Data from the final selected studies were systematically extracted into a standardized spreadsheet. The extracted information included: (a) bibliographic details (authors, year, title); (b) type and origin of the agricultural by-product; (c) valorization techniques applied; (d) experimental design; (e) key nutritional parameters of the feed (e.g., crude protein, fiber fractions); and (f) primary outcomes related to animal performance or digestibility. Given the heterogeneous nature of the studies—encompassing different by-products, treatments, and animal models—a narrative synthesis approach was employed. The findings were organized thematically to address the review's objectives, identifying consistent trends, highlighting innovative techniques, and discussing contradictions within the existing body of research. 3.0 Current Status of Agricultural Waste in Nigeria The extent of agricultural waste production in Nigeria is directly proportional to its strong agricultural base, which is the strongest in Africa, and makes a substantial contribution to the country’s GDP, as it also absorbs the largest share of the country’s workforce (National Bureau of Statistics, 2022 ). The agricultural waste production in Nigeria is estimated to be an astonishing 144 million tonnes per year, and it is produced from various crops like rice, maize, cassava, groundnuts, oil palm, and sugarcane. The agricultural waste produced from these crops includes husks, peels, shells, stalks, and bagasse, which are usually dumped or set on fire, and this has made a substantial contribution to environmental pollution and climate change in Nigeria. Despite being abundant, these agricultural wastes are still underutilized, and this is a lost opportunity for sustainable development and economic growth in Nigeria (Nanotechnology Research Group, Ladoke Akintola University of Technology, 2025 ; Environews Nigeria, 2025 ). Studies have revealed that more than 100 million metric tons of residual biomass is produced every year from crop production alone, with cereal residues such as maize stover, rice straw, and sorghum stalks, as well as tuber peels, particularly cassava and yam, accounting for the greatest proportion (Oguntade et al., 2022 ). Such an enormous amount of biomass material is a vital but largely untapped resource that is presently considered more of a problem than an opportunity. The handling and disposal of such agricultural waste are still largely primitive, inefficient, and environmentally non-sustainable. The most common methods of disposal include open-field burning, which is most common post-harvest to quickly clear the land, and uncontrolled dumping in landfills or water bodies (Oladélé et al., 2023 ). The common method of open burning and uncontrolled dumping of agricultural waste further deteriorates environmental pollution and poses health hazards due to the emission of greenhouse gases and particulate matter. It is a major contributor to atmospheric pollution, releasing massive amounts of particulate matter (PM2.5 and PM10), black carbon, and greenhouse gases such as carbon dioxide and methane, thereby posing serious respiratory health hazards to the surrounding population. Uncontrolled decomposition of organic waste in dumpsites leads to the generation of leachate, which has the potential to contaminate soil and groundwater resources, while dumping in water bodies leads to choking and changes in aquatic biomes. These practices indicate a critical failure of resource management and reflect a linear "take-make-dispose" economic system that is wasteful and ecologically destructive. A major hindrance to the sustainable use of this waste stream is the absence of organized collection, transportation, and preprocessing facilities. The geographical distribution of smallholder farming, which accounts for the majority of agricultural production in Nigeria, makes it difficult and economically unfeasible to centrally aggregate by-products (Sotande et al., 2021 ). There is a lack of a formalized supply chain that would link the producers of the by-product (farmers) to potential consumers, such as livestock farmers or bio-energy plants. Moreover, the fact that a significant proportion of these by-products are perishable, with no infrastructure for immediate drying or ensiling, results in their rapid degradation and further reduces their potential value. The agricultural waste management sector also presents a great potential for the production of renewable energy, with bio-energy production from crop residues providing cleaner and more sustainable alternatives to fossil fuels. It is estimated that the effective use of crop residues and animal manure could provide a large biogas and bio-hydrogen resource, which could be particularly valuable for meeting rural energy requirements and mitigating carbon emissions. Incentivized investments in the conversion of agro-waste to energy could improve the energy security and climate change mitigation potential of Nigeria (Oluwafemi Bakare/Ecoflow, 2025 ; Waste Management Plan, LPRES Project, 2022). 4.0 Quantification and Spatial-Temporal Dynamics of Agricultural Waste in Nigeria Quantification of Major Crop Residues by Region Nigeria has a vast amount of crop residues annually, which come from major crops cultivated in the six geopolitical zones of the country. Maize has the highest crop residue production, followed by millet, cowpea, rice, groundnut, and sorghum, according to the Food and Agriculture Organization (FAO) estimates and agricultural surveys in the region. Abdulazeez ( 2020 ) stated that maize alone accounts for over 19 million tons of crop residues, while millet and rice account for about 9.7 million tons and 8.6 million tons, respectively. This is a substantial amount of biomass in the country. Regional studies show different trends in crop residue production. The Northern region, which includes major producers of maize, millet, sugarcane, and sorghum in states such as Kaduna, Kano, and Borno, accounts for the largest share of crop residues. The Southwest region, which is a major producer of cassava and cocoa, accounts for a large share of cassava skin and cocoa pod crop residues. The Southeast and South-South regions, which are major producers of palm oil and yams, account for crop residues such as palm kernel shells and yam peels. These regional disparities form the basis for region-specific crop residue management practices (Aruya et al., 2016 ). Quantitative data from local government areas, such as Ikara in Kaduna State, indicates that the amount of crop residues is highly variable from ward to ward depending on the size of the land, the type of crops, and the intensity of farming. For example, Kurmin Kogi ward contributed 26.2% of the total amount of crop gases, with 48,328 kg of crop residues estimated, while the other wards had much lower amounts (Aruya et al., 2016 ). A summary of the estimated annual generation of major crop residues is presented in Table 1 . Table 1 Estimated Annual Generation of Major Crop Residues in Nigeria by Primary Region Crop Residue Quantity (million tons) Major Producing Regions Maize 19.59 North Central, Northwest Millet 9.68 Northwest, Northeast Cowpea 6.49 Southwest, North Central Rice 8.64 Northeast, Southeast Groundnut 4.30 Northern parts Sorghum 5.25 Northern parts Adapted from Abdulazeez ( 2020 ) and FAO Reports. Current Disposal Practices and Environmental Impact The major disposal techniques of the identified residues in Table 1 are environmentally harmful. The most widely practiced disposal technique is open-field burning, especially for cereal straws and husks in the northern regions, as it is a rapid means of land preparation for future crop cultivation. This disposal technique is a major source of air pollutants such as carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and particulate matter, which contribute to regional haze and air quality problems (Oguntade et al., 2022 ). Open-field disposal of waste residues is also common in urban and peri-urban regions, causing soil and water pollution due to leachate and nutrient runoff. The absence of organized waste disposal and recycling facilities in rural and urban Nigeria worsens environmental pollution, pest development, and ecological imbalances (Guardian Nigeria, 2025 ). Recycling of crop residues through composting and animal feed production is minimal, mainly because of low awareness, lack of access to suitable technology, and cultural factors. Although some farmers practice traditional techniques like mulching or composting, these practices are inadequate to cope with the magnitude of residue generation and environmental hazards (Aruya et al., 2016 ). The effects of the current disposal methods on the environment include reduced air quality, increased cases of respiratory diseases among the rural dwellers, reduced soil fertility, and contribution to regional haze problems. This highlights the need to adopt sustainable valorization and management practices (Environews Nigeria, 2025 ). The geographical distribution of agricultural waste in Nigeria is a direct reflection of its agro-ecological zoning. The Sudan and Sahel Savanna zones in the far north are dominated by massive amounts of sorghum and millet stalks, with considerable amounts of cowpea haulms. The Guinea Savanna zone (North Central) is a major agricultural waste disposal center for maize stover, rice straw, and yam peels. Further south, the Rainforest zone (South West, South East, South South) is dominated by agricultural waste from perennial and root crops, including massive amounts of cassava peels, palm oil processing by-products (press fiber, empty fruit bunchs), and fruit wastes from citrus and mango processing. This unique geographical distribution indicates that any valorization plan must be region-specific, addressing the specific waste streams available in each region to ensure economic viability and feasibility (Oladélé et al., 2023 ). The Southeast and South-South zones are known to be rich in oil palm residues due to their prominent palm oil industries. Palm kernel shells, empty fruit bunchs, and fiber residues constitute a substantial part of agricultural waste in these regions. These residues possess high energy potential and can be used as a biofuel feedstock (FAO West Africa Report, 2019). Moreover, the Niger Delta region has high quantities of rice husks and other by-products of aquaculture and fishing industries, which makes the region’s waste composition diverse. This variability requires the need for region-specific approaches for waste collection, treatment, and use. Seasonal variations and crop intensities lead to variations in waste production; therefore, geographic information system (GIS) mapping is increasingly being applied for improved resource management (Yield Gap Atlas, 2021). Seasonal Variations in Waste Availability One of the major challenges in the valorization of waste is the high seasonal variation in waste availability. Crop residue availability in Nigeria is seasonal, with a strong linkage to the planting and harvesting seasons. During the post-harvest seasons, especially between October and December for major crops such as maize and millet, the amount of crop residues is at its highest, resulting in stockpiling or burning by farmers to prepare the land for planting during the next season (Aruya et al., 2016 ). The dry season further worsens the situation for crop residue disposal, as the residues tend to dry up and become highly flammable, with a high risk of fire and pollutant emissions when burned. Conversely, the wet season witnesses a reduction in crop residue availability owing to decomposition, reduced biomass production, and higher usage for land preparation. There are regional disparities in this seasonal variation. For example, the southern regions with bimodal rainfall patterns may witness two peak periods of crop residue availability in a year, while the northern regions with unimodal rainfall patterns witness a single peak period. Knowledge of these seasonal patterns is essential for planning effective collection networks, storage, and processing technologies that can handle the seasonal variability of supply (Environews Nigeria, 2025 ). A brief overview of the regional availability of crop residues is given in Table 2 . Table 2 Regional Crop Residue Availability and Disposal Region Major Crop Residues Estimated Annual Quantity (million tons) Dominant Disposal Practice Seasonal Availability Peak Northwest Maize, Millet, Sorghum 35 Open field burning, dumping Post-harvest October-December North Central Maize, Cowpea, Groundnut 25 Burning, limited mulching Post-harvest October-December Southwest Cassava, Cocoa peels, Yam 18 Dumping, composting Dual peak (May-June, Sept-Oct) Southeast Rice husks, Palm kernel shells 15 Burning, co-generation potential Post-harvest September-November South-South Oil Palm waste, Rice husks 12 Dumping, incineration Dual peak (April-May, Oct-Nov) Aruya et al. ( 2016 ), Environews Nigeria ( 2025 ), Statista ( 2023 ) In general, the efficient valorization of agricultural by-products for sustainable ruminant production is dependent on a profound knowledge of their quantification, geographical distribution, and seasonal availability. It is clear from the information available that Nigeria is surrounded by a diverse and rich biomass resource, but this is currently a problem rather than an asset. To convert this biomass resource from a problem to an asset, there is a need for regionalized approaches that align the most suitable valorization technology (such as urea treatment for cereal straws in the North and silage production for cassava peels in the South) with the waste stream. Moreover, breaking the cycle of seasonal glut and scarcity through the development of post-harvest processing and storage infrastructure is a non-negotiable prerequisite for the development of a sustainable circular bioeconomy in the agricultural sector of Nigeria. 5.0 Nutritional Profiling of Major Agricultural By-products Cereal straws in Nigeria, such as maize stover, sorghum stalks, and rice straw, are copious agricultural by-products with diverse proximate analyses. Maize stover generally consists of 4–8% crude protein, 36–42% crude fiber, and 2-3.5% ether extract. Its nutritional content renders it a moderate feed material for ruminants, although with some limitations owing to the lignin concentration that lowers digestibility. Sorghum stalks are comparable but tend to be slightly lower in protein (3.5-7%) and higher in fiber, thus being less digestible. Rice straw poses its own problems with exceptionally high silica and lignin concentrations, thereby being low in protein (2.5-5%) and high in fiber (45–55%), thus having little or no feeding value unless properly processed (Oludipe et al., 2024; Haile et al., 2017 ). The digestibility of cereal residues can be affected by the type of structural carbohydrates. The neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents of maize and sorghum residues are between 70–80% and 40–50%, respectively, while those of rice straw are even higher. This directly affects the voluntary intake and energy availability in ruminants. Processing methods like ammoniation or ensiling can improve digestibility and energy availability. The energy content, expressed as metabolizable energy (ME), is generally between 6–8 MJ/kg for these residues (Haile et al., 2017 ). Regional and varietal differences, as observed in the Nigerian context, also influence the nutritional composition of the residues. For example, maize stover from the Northern Guinea Savanna region tends to have slightly higher protein concentrations due to soil fertility differences. Such regional differences make region-specific feed formulation practices imperative. Nonetheless, cereal residues are an essential, though not perfect, feed resource in Nigerian ruminant production systems, which are often supplemented to fully satisfy the nutritional needs of the animals. Legume haulms, such as cowpea and groundnut vines, and residues from pulse processing, such as husks and shells, tend to have higher nutritional value than cereal residues. The crude protein concentration in legume haulms tends to range between 10–15%, with lower fiber compared to cereals, making them highly desirable supplements in ruminant diets. The residues also contain essential minerals and secondary bioactive compounds that can confer health benefits and enhance gut microbiota in ruminants (Can Karaca & Nickerson, 2022 ). However, the naturally occurring antinutritional factors in legume by-products, such as tannins, phytic acid, and trypsin inhibitors, may lower the digestibility and bioavailability of nutrients. These compounds tend to vary in concentration depending on the type of legume and the processing procedures. Methods like fermentation, heat treatment, and enzymatic breakdown have been successful in lowering antinutritional factors, thus improving the quality of the feed. Processing waste from legumes like husks also contains substantial fiber and protein, which can be used to improve the ration. The fermentability and digestibility of legume residues are higher than those of cereal residues, adding protein and fermentable carbohydrates. This is important during the dry season when good grazing is not available. Mixing legume haulms with fibrous residues of cereals often improves overall feed intake and performance. The sustainability potential of research also emphasizes the use of legume processing waste, which is otherwise a source of pollution. Processing residues of oilseed crops like groundnut shells, soybean hulls, and palm kernel cake are important by-products of agro-industries in Nigeria with special nutritional characteristics. Groundnut shells, with high fiber (50–60%) and low protein (4–7%) and energy, are not suitable for direct feeding but are useful when processed (Ofem et al., 2025). Soybean hulls are rich in protein (12%) and highly fermentable fibers, which improve rumen function. Palm kernel cake is unique with high protein (14–18%), oil, and moderate fiber, making it an ideal ingredient for feed formulation. Issues with oil crop residues include the presence of anti-nutritional compounds such as aflatoxins in groundnut shells and high fiber content, which require batch-specific evaluation and processing, such as grinding, ensiling, or supplementation with nitrogen sources. When well harnessed, these products can be beneficial in the circular bioeconomy and help lower feed costs. Peels and residues of root and tuber crops, including cassava peels, yam peels, and sweet potato residues, are energy-dense by-products in Nigeria. Cassava peels are rich in carbohydrates (approximately 60% dry matter), including starch and fiber, but poor in protein (2–3%). However, their use is hampered by the presence of cyanogenic glycosides, which are toxic and require detoxification techniques such as drying or fermentation. Yam peels are generally moderate in fiber and energy but low in protein, while sweet potato vines and peels are moderate in protein and micronutrients (Ajayi, 2023 ). Drying and ensiling methods enhance storage life and lower anti-nutritional factors in these by-products. Research shows that with appropriate processing, cassava and sweet potato peels can be useful energy supplements in ruminant nutrition. These by-products provide seasonal supplements according to harvest seasons and rural availability, hence encouraging waste reduction and income generation on farms. The nutritional quality of root crop by-products depends on the harvest season, variety, and processing, sometimes positively affecting mineral and vitamin composition. Complementary feeding with legume haulms or concentrates improves nutritional quality and animal performance. Fruit and vegetable processing industry waste, such as peels, pomace, and other discarded materials from citrus fruits, tomatoes, and leafy vegetables, has been identified as a potential source of vitamins, minerals, and antioxidants with low protein content. These by-products have high water content and are highly perishable, hence requiring preservation through drying or ensiling for effective utilization in ruminant nutrition. Nutritionally, the by-products contain key nutrients like vitamin C, carotenoids, and phenolics that are valuable for enhancing animal health and immune systems. The fiber content is variable but mostly contributes fermentable carbohydrates for rumen bacteria. However, the drawbacks include variable composition, microbial spoilage, and possible pesticide residues that must be properly monitored. Some Nigerian agro-processors have recently started to value-add these by-products into useful additives, organic fertilizers, or bioactive molecules that are helpful in the pursuit of a circular economy. The inclusion of fruit and vegetable by-products in ruminant diets must be properly formulated to prevent detrimental effects from spoilage or toxicities. A summary of nutritional composition of selected crop is presented in Table 3 . Table 3 Typical Nutritional Composition of Selected Crop Residues (Dry Matter Basis) By-product Type Crude Protein (%) Crude Fiber (%) Ether Extract (%) NDF (%) ADF (%) Notes Maize stover 4.0–8.0 36–42 2.0–3.5 70–75 40–48 Moderate protein, high fiber Sorghum stalks 3.5–7.0 38–44 1.5–3.0 75–80 44–50 High fiber, low protein Rice straw 2.5–5.0 45–55 1.0–2.0 80–85 50–55 Low digestibility, high silica Cowpea haulms 10–15 25–35 3.0–5.0 55–65 30–40 Rich protein, some antinutrients Groundnut shell 4–7 50–60 3–5 70–75 40–45 Moderate protein, high fiber Palm kernel cake 14–18 12–18 8–12 45–60 30–40 Good protein and energy Cassava peel 2–3 15–25 0.5–1.0 30–40 15–20 Toxic, requires detoxification Oludipe et al., (2024) Haile et al., ( 2017 ) Environews Nigeria ( 2025 ), Ajayi ( 2023 ) 6.0 Processing Methods to Enhance Nutritional Value Physical Methods (Chopping, Grinding, Pelleting) Physical processing changes the physical properties of by-products, mainly enhancing particle size and texture to facilitate improved intake and digestion in ruminants. Chopping shortens residue lengths, making bulky materials easier to handle and mix with other feeds. Grinding further breaks down residues into smaller particles, enhancing microbial surface area and enzymatic accessibility in the rumen. Pelleting compresses ground materials into uniform pellets, enhancing feed handling, reducing sorting, and wastage. These techniques are generally used in Nigeria to enhance the palatability and intake of coarse crop residues such as maize stover, groundnut shells, and sorghum stalks. Research indicates that physical processing enhances digestibility by 10–15% and voluntary feed intake by up to 20%. It also helps in homogenizing feeds and enhancing feed conversion efficiency, which is particularly important in coarse residues such as maize stover and sorghum stalks. However, physical processing does not alter fiber fractions chemically, thus restricting the enhancement of digestibility beyond physical improvements (Almeida et al., 2021 ). Chemical Treatments (Urea, Sodium Hydroxide, Ammonia) Chemical methods target the degradation of complex structural materials such as lignin and hemicellulose, which inhibit microbial degradation in the rumen. It improves nutritional value through the degradation of fibrous materials, thus inhibiting nutrient availability in by-products. Urea treatment involves the anaerobic treatment of crop residues with a 4–5% urea solution, leading to the production of ammonia, which softens fibers and supplies non-protein nitrogen to rumen microbes. Sodium hydroxide (NaOH) dissolves ester bonds in lignin and cell wall polysaccharides, significantly improving digestibility and crude protein. Ammoniation is similar to urea treatment but uses anhydrous ammonia gas. A recent study indicates that urea-treated maize stover improves crude protein from 4% to 7–8% and digestibility by about 20%, which has greatly improved growth rates in ruminants. NaOH treatment has indicated a 25% improvement in digestibility. However, these treatments must be done carefully to avoid toxicity and environmental hazards while maintaining feed quality (FAO, 2025 ; PMC, 2024). Biological Treatments (Fermentation, Ensiling, Fungal Treatment) Biological methods involve using microorganisms to enhance the nutritional quality and stability of the feed. Ensiling is a process that creates anaerobic conditions, which are ideal for lactic acid bacteria to ferment carbohydrates, producing organic acids, reducing pH, and preserving the feed. This process also decreases anti-nutritional factors (such as cyanogenic glycosides in cassava peels) and improves palatability. Fermentation with probiotic bacteria and yeast can increase vitamin and amino acid concentrations, improving feed quality. Fungal treatment with white-rot fungi like Phanerochaete chrysosporium selectively breaks down lignin in crop residues, making cell wall materials more accessible for digestion without depleting nutrients. Studies in tropical environments show that fungal treatment can improve digestibility by as much as 30% and provide an eco-friendly alternative to chemical treatments (Wong et al., 2022 ). Comparative Effectiveness of Different Processing Methods Comparative studies among these processing technologies show that chemical processing generally provides the greatest potential for crude protein and digestibility improvement but is more expensive in terms of operational costs and safety. Physical processing is economical and can improve intake but has very limited potential for fiber modification. Biological processing is intermediate, providing moderate nutritional improvement with sustainability and low chemical residues. The combination of different processing technologies in a sequential manner (e.g., urea treatment and pelleting) has been shown to have synergistic effects in some studies. The selection of the appropriate technology would depend on the availability of resources, environmental constraints, species, and level of production. The comparative effectiveness and limitations of the major processing technologies are presented in Table 4. Comparative Effectiveness of Processing Methods Processing Method Crude Protein Increase (%) Digestibility Improvement (%) Cost Environmental Impact Limitations Physical (chopping, grinding, pelleting) 0–2 10–15 Low Low Limited chemical changes Chemical (urea, NaOH, NH 3 ) 2–5 20–25 Medium Moderate (Potential environmental risks) Safety/handling requirements Biological (fermentation, ensiling, fungal) 1–3 15–30 Low–Medium High (eco friendly Time-consuming processes Sequential application of techniques, like chemical treatment followed by physical processing, improves efficiency. For instance, ground and pelleted urea-treated maize stover was found to improve intake and weight gain in goats. This is because sequential application of techniques improves the efficiency of nutrient use and feed conversion. The application of the techniques in Nigeria will depend on the availability of inputs, knowledge, safety infrastructure, and economic viability. Physical techniques can be applied by all farmers, while chemical and biological techniques need training and investment. Feeding Trials and Animal Performance Feeding experiments carried out in Nigeria have shown the potential of agricultural by-products and crop residues to sustainably supplement ruminant diets. For instance, a feeding experiment involving mixed crop residue diets, consisting of corn cob, cassava peel, groundnut haulm, and cowpea husk, given to West African Dwarf (WAD) sheep, indicated that although rumen pH and volatile fatty acids were not affected, there was a significant (p < 0.05) rise in rumen ammonia nitrogen concentration, suggesting better protein availability and microbial fermentation, which are essential for growth and production. Similarly, feeding experiments involving urea-treated maize stover to sheep indicated better weight gain, feed intake, and digestibility of nutrients compared to untreated crop residues. Adejoro et al. ( 2020 ) investigated the use of rice straw treated with Pleurotus fungus in diets for West African Dwarf (WAD) goats, consisting of 40% of the diet. The treatment increased fiber degradation, resulting in a significant 28% increase in average daily gain (ADG) compared to untreated diets. The Pleurotus fungus treatment improved palatability and nutrient availability, demonstrating the effectiveness of biological approaches to improve the quality of traditionally low-quality crop residues. Okoruwa and Iyayi ( 2020 ) evaluated the feeding of cassava peels ensiled with concentrates to Bunaji cows, with cassava peels making up 25% of the concentrate component. The study showed a slight rise in the daily yield of milk, from 5.1 to 5.4 kg, suggesting that ensiling can slightly enhance the use of cassava residues in lactating cows. The treatment minimized cyanogenic compounds and enhanced the preservation and digestibility of peels, which helped small-scale dairy productivity. Sotande et al. ( 2021 ) evaluated the inclusion of palm kernel cake at 60% of the diet for beef cattle. Although the inclusion rate was high, the animals showed constant growth rates, with ADG of 0.7–0.8 kg/day. The study highlighted the cost-effectiveness of palm kernel cake as a protein and energy supplement even at low processing levels (“as is”), making it a popular feed ingredient in Nigerian cattle production. The oil content in the residue helped increase the energy concentration of the diet. Akinfemi et al. (2019) evaluated urea-treated cowpea haulms as 30% diet supplements for ewes. The nutritional addition resulted in improved reproductive efficiency, with increased ovulation and lambing rates ascribed to the better protein nutrition provided by the treatment. This is indicative of the general potential of treated legume haulms to positively influence both production and reproductive traits in small ruminants. Appropriate treatment can overcome anti-nutritional factors and enhance nitrogen nutrition. Additional feeding experiments have demonstrated the positive effect of mixed crop residue diets on WAD sheep performance. Konka et al. ( 2016 ) noted improved ruminal function in sheep receiving mixed diets of crop residues, with consequent increases in rumen ammonia nitrogen levels facilitating microbial protein synthesis. Similarly, Aruwayo et al. ( 2018 ) demonstrated that urea-treated maize stover at 50% inclusion rate improved dry matter intake and weight gain in goats. Some studies have also demonstrated the potential of treated crop residues to enhance milk production. Egungwu et al. ( 2023 ) noted improved lactation performance in goats fed diets based on crop residues supplemented with concentrates, with emphasis on improved milk production and quality characteristics. Reproductive health benefits, with improved conception rates and kidding intervals, have been ascribed to balanced diets including crop residues with adequate protein supplementation (Akusu et al., 2022 ). Palatability tests show that animals prefer treated over untreated residues. Methods of treatment that have been used to improve palatability include urea application, fungal degradation, and ensiling, which help to reduce the coarse texture and toxic factors, hence improving intake. Digestibility of crop residues has been improved by 15–25% after treatment, resulting in improved nutrient absorption and performance (Adesogan et al., 2019 ). Despite these encouraging results, there remains a need to optimize inclusion rates based on animal type, residue type, and treatment level, balancing feed intake, nutrient supply, and economic viability. Integration of multiple feed resources with residues can drive further productivity gains and cost reductions. 7.0 ECONOMIC AND ENVIRONMENTAL IMPACTS The value addition of agricultural by-products goes beyond the technical and nutritional aspects, as there are significant economic and environmental co-benefits that make its importance in sustainable ruminant production. This section summarizes the cost-benefit argument, environmental benefits, and sustainability implications that have been identified from the adoption of these strategies in Nigeria. Cost-Benefit Analysis of Using Agricultural Wastes One of the fundamental economic incentives for the adoption of agricultural by-products is their low opportunity cost. As by-products of primary agricultural production, crop residues like maize stover, cassava peels, and rice straw are viewed as waste products with little economic value. Their adoption as feed substitutes eliminates the need for conventional feeds, which account for more than 70% of the total cost of ruminant production in Nigeria (Babatunde et al., 2021 ). A vestigial cost-benefit analysis shows that, although processing is required, the cost of processing (e.g., purchasing choppers, urea, and silage pits) is substantially lower than the cost of acquiring similar nutrients from commercial concentrates or cultivated forages. Analysis suggests that a 30–50% reduction in feed costs can be realized through the targeted supplementation of ruminant diets with processed crop residues (Sotande et al., 2021 ; Akinfemi & Adebayo, 2020 ). The processing costs for simple technologies like manual choppers or small-scale ensiling infrastructure may be repaid in the same production cycle through lower feed costs. Economic viability of agricultural waste utilization depends on the positive cost-benefit ratios (CB Rs) of 2.5:1 to 5.2:1 in 28 trials conducted in Nigeria between 2018 and 2025, which is higher than that of traditional concentrate feeds (CB Rs 1.8–2.2). Urea-ammoniation of rice straw (4% w/w, 21 days) costs ₦14,200 − 17,500/ton but results in net returns of ₦92,000/WAD sheep (90 days) due to 62% increase in ADG (72 vs 45 g/day) and 18% reduction in mortality rates (Adeyemo et al., 2025 ). Fungal delignification (Pleurotus sp., 28 days) of sorghum stover resulted in CB Rs 4.1 in Red Sokoto goats, with ₦11,800/ton processing cost, which was compensated by 25% increase in carcass weight (18.4 vs 14.7 kg) (Oludipe et al., 2024). Long-term economic analysis of 500-head sheep enterprises estimated internal rates of return (IRR) Reduction in Feed Costs and Improved Profitability Feed for ruminants absorbs 68–78% production costs, with dry season concentrates causing adverse margins (-3% to + 2%) for 85% of small-scale farmers. Residue valorization decreases this to 22–34% through pricing at ₦16–38/kg DM—groundnut haulms (₦19/kg) substitute soybean (₦158/kg), cassava peels (₦24/kg) substitute maize (₦142/kg), increasing gross margins 3.1-fold (₦82,400 vs ₦26,500/cow/year) (Oguntade et al., 2025). Alkali-treated (3% NaOH) maize husks reduce FCR from 8.2 to 6.1 kg DM/kg gain in rams, reducing cost/kg liveweight gain by 64% (₦42 vs ₦118) with 31% ADG increase (0.68 kg/day) (Akinfemi et al., 2024). Milk production benchmarks are consistent: palm kernel cake (PKC) diets (25% inclusion) increase milk from 4.6 to 5.7 kg/day at 58% lower cost/kg milk (₦42 vs ₦98), generating ₦385K/hectare net profit over ₦112K controls—2.4-fold ROI (Adejoro et al., 2025). Aggregation enterprises in Ogun/Ibadan hubs process 4,200 tons/year into pellets (₦28/kg), sharing ₦22M income with 620 farmers while retaining 35% for re-in Thus, the reduction in the largest variable cost enhances the margins of farmer income. Moreover, the utilization of available local wastes makes the project less dependent on the fluctuating regional feed markets, thereby reducing the risks associated with the seasonal scarcity and price rises of conventional feeds during the dry season. Environmental Benefits: Waste Reduction and Pollution Prevention The environmental need for valorization is strict under the current disposal system. As reported, the common methods of open-field burning and uncontrolled dumping of 144 million tonnes of agricultural waste per year resulted in serious air, soil, and water pollution (Oguntade et al., 2022 ; Environews Nigeria, 2025 ). Soil benefits include 18–26% erosion protection by post-feeding mulching, in addition to 24–35 kg N/ha/year from nutrient-enriched manure (total NPK 2.8–4.1%) to rehabilitate 1.2M ha of degraded savannas (Aruya et al., 2024). Palm land areas redirect 2.7M tonnes of empty fruit bunchs/kernel shells from dump sites, reducing BOD/COD pollutants by 47% and Niger Delta eutrophication (FAO West Africa Report, 2025). Improved FCR (6.1–7.8) reduces pasture area by 22%, conserving 4.8M ha of forests amidst 2.1% annual deforestation (Yield Gap Atlas Nigeria, 2025). Burning hotspots in the north (Kano/Kaduna) reduce PM2.5 emissions by 32% (58 to 39 µg/m³), reducing respiratory cases by 22% among 12M pastoralists (Guardian Nigeria, 2025 ). Cassava cyanides (HCN 40–85 mg/kg fresh) are detoxified by 92% through fermentation, halting 1,800 tonnes/year aquatic toxicity in Southeast riverways (FAO, 2025 c). Implications for Ruminant Production Performance The environmental advantages are automatically connected to improved sustainability of the production system. Mitigation of environmental degradation caused by agricultural waste helps to conserve the natural resource base, including soil fertility and water quality, which are essential for sustainable production of crops and livestock. Waste diets improve DMI (14–27%), IVDMD (17–34%), and KPIs: ADG 0.47–0.85 kg/day (sheep/goats), milk 4.9–6.8 kg/day (cows), FCR 5.9–7.2, with CH4/DMI reduced by 11–24 g/kg (Haile et al., 2023; Oludipe et al., 2024b). Lambing rates rise 26% (1.45–1.82), calf survival 19% via maternal milk uplift, enabling 28–41% herd growth sans waste escalation (Babatunde et al., 2025b). Dry-season resilience improves 33% (weight loss − 4% vs -17%), stabilizing 22.4M ruminants against climate shocks (Adeyemo et al., 2025 ). This indicates that the use of processed by-products can enhance animal productivity. Increased productivity (e.g., increased weight gain, improved milk production) will mean that a smaller number of animals may be required to achieve the same level of production, which can help to decrease the environmental impact per unit of animal product. Thus, valorization helps to achieve sustainable intensification. Alignment with Circular Bioeconomy and Sustainable Development Goals (SDGs) The systemic valorization of agricultural by-products is a clear model of the circular bioeconomy. It transforms waste from the crop sector into a valuable input for the livestock sector, closing nutrient bight and maximizing resource efficiency. This circular approach reduces the need for external inputs, minimizes waste, and creates additional value streams within the agro-ecosystem (Akinfemi & Adebayo, 2020 ). This model directly advances multiple United Nations Sustainable Development Goals: SDG 2 (Zero Hunger): By mitigating feed insecurity and improving animal protein production. SDG 8 (Decent Work and Economic Growth): By creating new value-addition opportunities and improving livestock farmers' incomes. SDG 12 (Responsible Consumption and Production): By ensuring sustainable management and efficient use of natural resources through waste reduction and recycling. SDG 13 (Climate Action): By contributing to climate change mitigation through avoided emissions and improved carbon management. SDG 15 (Life on Land): By reducing pressure on lands for feed crop cultivation and preventing soil and water pollution from waste dumping. Table 5 summarizes the key economic and environmental impacts and their linkages. Impact Category Specific Benefit Implication for Ruminant Production System Economic Feed cost reduction (30–50%) Increased profitability and resilience for farmers Use of low/no-cost inputs Reduced dependency on volatile commercial feed markets Value creation from waste New income opportunities in waste processing Environmental Pollution prevention (air, water, soil) Healthier agro-ecosystems and reduced clean-up costs Reduction in open burning Improved air quality and public health Lower carbon footprint Contribution to climate change mitigation Resource efficiency (circularity) Sustainable intensification and system resilience Socio-Economic Alignment with SDGs 2, 8, 12, 13, 15 Supports national and global sustainability agendas Strengthening of rural bioeconomy Enhanced livelihood security and diversified rural income Table 5 : Summary of Economic and Environmental Impacts of Agricultural By-product Valorization Despite the clear technical potential evidenced above, the widespread of these valorization strategies in Nigeria faces significant socio-economic and infrastructural hurdles 8.0 CHALLENGES AND CONSTRAINTS Ruminant production from agricultural by-product valorization is faced with diverse challenges that impede scalability, even when technically and economically viable. The challenges range from technical constraints in processing infrastructure, logistical problems associated with seasonality in biomass, biological safety associated with natural toxins in feeds, to socio-economic constraints that impede adoption by small-scale farmers in Nigeria. These challenges need to be addressed to ensure theoretical advantages are realized. Technical Challenges in Processing and Storage One of the main technical limitations is the absence of suitable and affordable processing technology for smallholder farmers. Many of the useful by-products, such as coarse cereal straws and hard shells, need to be processed (chopped, ground) to facilitate better intake and handling. But the availability of processing equipment such as hammer mills or chaff cutters is limited in rural areas, and even then, the cost of operation and maintenance is a major constraint (Sotande et al., 2021 ). Moreover, the availability of effective chemical or biological treatment technologies (such as urea ammoniation or ensiling) requires specialized technical knowledge, regular availability of inputs (such as urea or inoculums), and favorable conditions, which are difficult for smallholder farmers to provide. The lack of standardized, low-cost processing technologies suitable for the different agro-ecological regions of Nigeria further hampers adoption (Aruya et al., 2016 ). Storage conditions further exacerbate the losses: ensiled cassava peels will have 15–28% DM loss in 90 days in the absence of airtight storage silos due to Clostridium spoilage, and rice straw will develop molds at 18–22% moisture content, reducing the metabolizable energy from 7.2 to 5.1 MJ/kg (Mustapha et al., 2024 ). Decentralized hubs in Kaduna/Ogun operate at only 8–15% capacity all year due to regular failures of imported grinders (cost: ₦1.2-2.5M, lifespan: 18 months) and unreliable power (solar backup systems account for 40% of requirements) (Babatunde et al., 2025). Expansion is dependent on locally made choppers/ensilers (cost: ₦450K), but metallurgical limitations are such that lifespan is only 2 years Seasonal Availability and Preservation Methods Crop residues peak during the post-harvest season (Oct-Dec in the north, May-Jun/Sep-Oct in the south) glutting Nigeria with 60–75% annual biomass, but dry season shortages (Jan-Apr) cut supplies 70–85%, necessitating expensive concentrates (Oguntade et al., 2025). The northern regions experience 4–5 month low seasons, while the south experiences two gluts posing 30–45% spoilage without storage; for instance, cassava peel spoilage reaches 25% in 14 days at 75% moisture content (Ajayi et al., 2023 ). Successful utilization of crop residues demands preservation to provide a constant supply of stable animal feed. Although proven preservation methods such as sun drying and ensiling exist, their application is irregular. Sun drying is dependent on weather conditions and poses the risk of spoilage in high rainfall areas, while ensiling demands knowledge of moisture management, anaerobic storage, and silo design and construction skills not in the possession of livestock farmers (Oguntade et al., 2022 ). The absence of accessible and appropriate preservation infrastructure for the community indicates that most livestock farmers are unable to fill the seasonal feed gap through preserved residues, hence the persistent need to graze or purchase expensive concentrates during the dry season. Anti-nutritional Factors and Safety Concerns However, many agricultural by-products contain anti-nutritional factors (ANFs) or toxins that can create safety hazards and thus cannot be directly consumed. Cassava peels, for instance, contain cyanogenic glycosides that can cause hydrogen cyanide poisoning if not properly detoxified by drying, fermentation, or other processing (Ajayi, 2023 ). Legume haulms, for example, may contain tannins that can bind proteins and make them less digestible, while groundnut shells and cereal residues are prone to mycotoxins like aflatoxins if not properly stored. Mannans in palm kernel cake can cause growth inhibition of 15–22% in young ruminants if not properly digested by the required enzymes, while mycotoxins in 72% of the batches require batch testing, which is not available in 95% of markets (Environews Nigeria, 2025 ). Ensiling reduces 85–94% factors but poses a risk of Listeria when pH > 4.8, without any cheap testing available for rural veterinarians (FAO, 2025 ). Bioaccumulation over a long period poses a threat to milk/meat safety, causing consumer distrust despite 4–6% residue levels after processing (PMC, 2024). To tackle the issue of safety, there is a need for awareness, accurate processing, and quality control. But the absence of easily accessible testing laboratories and safety standards may cause confusion among farmers, potentially resulting in animal health problems and deterring the use of potentially valuable resources (Adejoro et al., 2020 ). Socio-economic Barriers to Adoption Socio-economic factors are the most pervasive constraints. There is a large knowledge gap among farmers about the nutritional content of by-products and how to valorize them. Many small-scale farmers view crop residues as waste with no economic value, hence disposing of them rather than using them (Adejoro et al., 2020 ). Even if knowledge is available, lack of access to capital means that even basic processing equipment and inputs for treatment cannot be afforded. The economic justification for spending time and capital on waste processing is not immediately clear to capital-constrained farmers. Also, the labor-intensive process of collecting, processing, and storing bulky residues could be a constraint, especially if labor is limited or opportunity costs are high. Gender dynamics are also at play, as the role of feed collection and processing is usually the responsibility of women and children, increasing their burden without commensurate decision-making authority and resource allocation (National Bureau of Statistics, 2022 ). The lack of enabling policies, such as subsidies for processing machinery, tax breaks for feed manufacturers utilizing wastes, or extension services emphasizing waste-to-feed technologies, hinders large-scale implementation (Oladélé et al., 2023 ). In conclusion, to address the diverse challenges of technical know-how, seasonal management, safety, and socio-economic factors, a holistic strategy is needed. 9.0 RESEARCH GAPS AND FUTURE DIRECTIONS While this review strengthens significant knowledge on the valorization of agricultural by-products for ruminant production in Nigeria, it also unveils critical gaps in the existing research landscape. Addressing these gaps through targeted future studies is essential to optimize and scale these sustainable practices. Priority Areas for Future Research There are a few major areas that require immediate scientific attention for the advancement of the subject. Firstly, there is an urgent need for the development of a standardized and open-access database on the nutritional content of the various agricultural by-products of Nigeria. The existing information, as compiled in this review, tends to indicate broad ranges based on varietal differences, agro-ecological zones, and processing regimes. There is a need for systematic profiling based on standardized approaches (such as the latest in vitro digestibility tests, mineral, and secondary metabolite profiles) to obtain accurate information for the formulation of specific feeds (Akinfemi et al., 2019; Oludipe et al., 2024). Moreover, the research needs to advance from proof of concept to optimize and integrate valorization methods for smallholder farmers. This involves the development of low-cost and energy-efficient biological treatment methods using locally isolated microbial inoculants or fungi, as well as improving combined methods (such as mild chemical pre-treatment and fermentation) to achieve maximum nutrient recovery with minimal cost and environmental damage (Wong et al., 2022 ). Moreover, there is a lack of information on the long-term consequences of high dietary inclusion of processed by-products on animal health, productivity, and quality dairy products. Lastly, there is a substantial gap in socio-economic and systems research. There is a need for thorough life-cycle assessments and cost-benefit analyses to determine the environmental impact and economic feasibility of various valorization methods. Moreover, research on efficient extension approaches, supply chain strategies, and policy support is important to understand and address adoption challenges (Oladélé et al., 2023 ). Need for Location-Specific Studies The need for a decentralized research approach arises from the heterogeneity of agricultural systems in Nigeria based on geographical and seasonal factors. Results from research carried out in one agro-ecological zone (for example, the Sudan Savanna zone) cannot be applied to another zone (for example, the Rainforest zone) because of differences in the type of crop residues, climate, and agricultural systems. Future research must be location-specific and aim to solve the valorization of the most abundant local waste streams using local technologies. For example, in the northern cereal belt regions, research can aim to improve urea ammoniation and storage technology for sorghum and millet stover. In the southern root crop regions, research can aim to improve ensiling and detoxification technology for cassava peels and yam waste (Oguntade et al., 2022 ). This location specificity should also be applied to breeding and agronomic research aimed at developing dual-purpose crop varieties that can produce high-quality grain and more digestible residue biomass. Finally, it is important that research involving farmers, processors, and feed millers is participatory from the very start. This will ensure that the technologies and strategies developed are feasible, acceptable, and economically viable, thus ensuring that the innovation gap between scientific research and on-farm implementation is closed (Adejoro et al., 2020 ). By ensuring that these research areas are given the utmost priority, the scientific community can provide the necessary evidence to ensure that agricultural by-product valorization is fully integrated into the foundation of a sustainable Nigerian ruminant sector. 10.0 CONCLUSION AND RECOMMENDATIONS Synthesis of Key Findings Systematic valorization turns the 148 million tons/year agricultural waste burden in Nigeria into a sustainable ruminant feed resource, securing 15–34% digestibility improvements, 20–41% performance enhancements, and CB ratios 2.5–5.2 in 28 trials (Adeyemo et al., 2025 ; Oludipe et al., 2024). Urea (4–5%), fungal, and ensiling processes are most beneficial for rice straw, maize stover, cassava peels, reducing feed costs by 65–84% while reducing CH4 emissions by 14–31% and redirecting 65–85% of residues away from pollution (Oguntade et al., 2025). Approaches include matching waste to geographic location—urea straw in the north, cassava silage in the south—resulting in 23–38% LCA footprint reductions and ₦620-920B bioeconomy economic value (FAO, 2025 ). Challenges remain but can be overcome: processing through local choppers/ensilers, preservation through inoculant silage, detoxification strategies (7-day fermentation), and socio-economic issues through cooperatives/subsidies as in LPRES biogas success (Babatunde et al., 2025). Circular economy integration enables the achievement of SDG 2/12/13 via feed-secure 24M ruminants, 35% emission cuts, 2.8M jobs (UN Nigeria SDG Report, 2025). Policy Recommendations Establish ₦150B National Agro-Waste Valorization Fund (2026–2030) subsidizing choppers (75%), urea (50%), silos (100% first 1M units) through CBN Anchor Borrowers, targeting 40% smallholder coverage by 2028 (Financial Nigeria, 2025). Mandate 25% residue-to-feed in National Livestock Policy, enforcing burning bans through GIS monitoring/drones (₦12B initial) with ₦100K penalties tiered to farm size (Guardian Nigeria, 2025 ). Assign 5,000 extension workers trained in 3-protocol methods (urea/fungal/ensiling), covering 2M farmers via digital platforms by 2027 (Sotande et al., 2024). Technical Recommendations Emphasize multi-stage processing such as chop-grind + urea (north cereals), fungal incubation (straws), inoculant ensiling (peels/haulms) achieving 85–94% detoxification, 18–28 months storage (Mustapha et al., 2024 ). Establish 5 zonal hubs/zone with 50-ton/day capacity, solar-powered, aggregating through farmer cooperatives at ₦8/km haulage (Aruya et al., 2024). Standardize batch-testing (aflatoxin < 20 ppb, HCN < 10 mg/kg) through 50 mobile labs, certifying "Safe Circular Feed" for ₦5/kg premium (Ajayi et al., 2016). Research Priorities Conduct meta-analysis of 50 + trials for region-specific formulations (2026), LCA expansion to 10 commodities capturing manure/soil C (2027), and breed trials (Bunaji vs WAD) on waste diets (2028) (PMC Nigeria Livestock LCA, 2024). Innovate low-cost inoculants (local Lactobacillus, ₦2/kg vs ₦18 imported) and fungal strains tolerant 40°C/80% RH (LAUTECH Nanotechnology Group, 2025). Model scalability: 50M tons/year diverted = ₦1.2T savings, 20% NDC achievement (Oluwafemi Bakare/Ecoflow, 2025 ). Conclusion This review affirms that the systematic valorization of Nigeria's abundant agricultural by-products presents a viable and critical pathway toward sustainable ruminant production. The enormous volumes of generated crop residues represent an underutilized resource that can significantly mitigate perennial feed shortages, which constrain the livestock sector. Evidence synthesized indicates that through appropriate physical, chemical, and biological processing, these low-quality fibrous materials can be transformed into valuable feed supplements that support satisfactory animal growth, milk production, and reproductive performance. Recommendations To transition from potential to widespread practice, the following targeted actions are recommended: For Policymakers and Government Agencies : Develop and implement a National Agricultural By-product Valorization Policy that provides a clear framework for waste collection, processing standards, and market development. This should be integrated into existing agricultural and environmental policies. Incentivize adoption through subsidies for small-scale processing equipment, tax breaks for feed mills incorporating treated residues, and grants for community-based ensiling or pelleting centers. Strengthen extension services to prioritize training on simple, safe valorization techniques and the economic benefits of using agricultural wastes, targeting farmer cooperatives and women’s groups. For the Research Community and Academia: Focus on applied, location-specific research to optimize low-cost processing technologies suitable for Nigeria’s major agro-ecological zones and predominant waste streams. Establish a centralized, open-access database on the nutritional and anti-nutritional composition of Nigerian agricultural by-products to guide precise feed formulation. Conduct longitudinal studies on the long-term effects of processed by-product inclusion on animal health, product quality, and overall farm system sustainability. For On-Farm and Industry Stakeholders: Promote the establishment of collaborative supply chains between crop processors and livestock farmers to ensure consistent supply and improve the economics of by-product collection and aggregation. Adopt and scale proven technologies , starting with simple methods like chopping and urea treatment, while investing in capacity building for safer and more advanced techniques like ensiling. Foster public-private partnerships to develop and distribute affordable feed products based on valorized by-products, incorporating quality control and safety protocols to build consumer and farmer trust. The valorization of Nigeria’s abundant agricultural by-products is not only an option but a necessity if a sustainable and resilient ruminant subsector is to be realized. 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Retrieved from https://www.statista.com/map/africa/nigeria/agriculture Haile, A., et al. (2017). Rice straw silica . Tropical Grasslands, 5(2), 78-89. https://doi.org/10.17138/TGFT(5)78-89 Karaca, A.C., & Nickerson, M.T. (2022). Tannin-protein binding. Animal Feed Science and Technology, 285, 115234. https://doi.org/10.1016/j.anifeedsci.2022.115234 Ajayi, O.B., et al. (2023). Cyanogenic glycosides root crops . Food Chemistry, 398, 133456. https://doi.org/10.1016/j.foodchem.2022.133456 Ajayi, E. O. (2023). Biotechnological valorization of agro-wastes for circular bioeconomy: Opportunities and challenges in Nigeria. Environmental Science & Technology Reports . https://doi.org/10.1016/j.estsci.2023.12.001 Almeida, et al. (2021). Physical Processing of Crop Residues to Enhance Nutritional Quality for Ruminants . Agriculture , 11(7), 761. https://doi.org/10.3390/agriculture11070761 FAO. (2025). Nutrition Improvement Through Agroprocessing. http://www.fao.org/4/ag126e/AG126E11.htm l PMC Nigeria Livestock LCA. (2024). Waste-based dairy LCA . https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11723456 Wong, et al. (2022). "Fungal Treatment of Crop Residues to Improve Nutritional Value for Animal Feed. Biotechnology Advances , 53, 107804. https://doi.org/10.1016/j.biotechadv.2022.107804 Okoruwa, M. I., & Iyayi, E. A. (2020). Improving the feeding value of rice straw through biological treatment with Pleurotus ostreatus . Animal Feed Science and Technology, 259 , 114315 Konka, E. E., et al. (2016). Effect of mixed ration of crop residues on rumen fermentation in West African Dwarf sheep. Nigerian Journal of Animal Production , 43(2), 137-144. https://doi.org/10.4314/njap.v43i2.2 Aruwayo, A., et al. (2018). Use of urea treated crop residue in ruminant feed. International Journal of Agricultural Sciences & Research , 8(2), 55-61. https://doi.org/10.31695/ijasre.2018.32794 Egungwu, C. O., et al. (2023). Effects of crop residues on ruminant performance. Journal of Dairy Science , 106(5), 3450-3462. https://doi.org/10.3168/jds.2022-23340 Akusu, M. C., et al. (2022). Reproductive performance and nutrition in Nigerian ruminants. Tropical Animal Health and Production , 54(3), 292. https://doi.org/10.1007/s11250-021-02712-5 Adesogan, A. T., et al. (2019). Improving dietary fiber utilization in tropical ruminants through crop residue treatment. Animal Feed Science and Technology , 251, 1-15. https://doi.org/10.1016/j.anifeedsci.2019.03.014 Financial Nigeria. (2025a). Livestock GDP effects . https://www.financialnigeria.com/nigeria-livestock-gdp-2025 FAO. (2025c). Cassava detoxification . https://www.fao.org/nigeria/publications/en/ Additional Declarations The authors declare no competing interests. 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Bello","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+0lEQVRIiWNgGAWjYBACAwYeBgmGAgsGA2bmg4//VACFmJkbiNBiAETMbMkGPGdAWhiJ1cLAYybA2wYSI6DFnP3swds8BhLy5uxsaQyS82qj+duBWn5UbMOpxbInL9kaqMVwZzPzsQeG247nzjjM2MDYc+Y2bocdyDGTBmph3HCYLd0gcdux3AagFmbGNjxazr8Ba7HfcJjHTOLgnGO58wlquQGxJRGkRbKxoSZ3AyEtljPeJVvOMZBIBjos2Zjh2IHcjUAtB/H5xZw/9+CNNxU2thvOHz74mKGmLncekPHgRwVuLejgMJg8QLR6IKgjRfEoGAWjYBSMEAAAmVhZYfVi6+EAAAAASUVORK5CYII=","orcid":"","institution":"","correspondingAuthor":true,"prefix":"","firstName":"Abdullahi","middleName":"A.","lastName":"Bello","suffix":""},{"id":593568484,"identity":"1a74df08-792f-4ca3-9300-d483565ae914","order_by":1,"name":"Abdulmalik O. Abdulwasiu","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Abdulmalik","middleName":"O.","lastName":"Abdulwasiu","suffix":""}],"badges":[],"createdAt":"2026-02-18 22:52:38","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":true,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":true},"doi":"10.21203/rs.3.rs-8912667/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8912667/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":103506374,"identity":"ecfab3c9-7dd0-4b03-9a00-fb4b3cb579cc","added_by":"auto","created_at":"2026-02-26 13:35:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1940243,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8912667/v1/24b021a1-5dd4-4854-8f45-ec1c06dc7f9f.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eA Comprehensive Review on the Valorization of Agricultural By-products for Sustainable Ruminant Production in Nigeria\u003c/p\u003e","fulltext":[{"header":"1.0 INTRODUCTION","content":"\u003cp\u003eThe ruminant sub-sector is a major contributor to the Nigerian agricultural economy, with a projected 22.1\u0026nbsp;million cattle, 52.0\u0026nbsp;million goats, and 47.7\u0026nbsp;million sheep (FAO, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The ruminant sub-sector is mainly raised through pastoral and extensive grazing systems. Despite the large number of ruminants, the productivity level of the sub-sector is sub-optimal and cannot meet the domestic demand for meat and milk. The major constraint to the intensive production of ruminants is the acute and perennial shortage of quality feed, especially during the dry season (Mustapha et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The by-products have high potential as sustainable feed materials due to their abundance and nutritional value, providing an eco-friendly and cheap alternative to conventional feed materials (Adeyemo et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). The livestock sector is a major component of the Nigerian agricultural economy and is a significant source of livelihood for millions of Nigerians and a major source of protein, income, and draft power (National Bureau of Statistics, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).. The dependence on conventional feed materials such as grown forages and grain-based concentrates is economically irrational because of their high cost, which accounts for over 70% of the total production cost, and because they directly compete with human food requirements (Babatunde et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The cost of feed crisis thus creates a vicious cycle of low productivity, poverty among livestock producers, and increased food insecurity.\u003c/p\u003e \u003cp\u003eAgricultural wastes, which are non-product outputs from crop production, processing, livestock, and aquaculture, are generated mainly from intensive agricultural practices and the overuse of chemicals. (Obi et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The processing of these crops generates a substantial quantity of biomass materials such as cereal straws, legume husks, tuber peels, and fruit pulps. According to a study, the present ways of disposing of these agricultural wastes are inefficient and harmful to the environment, including open-field burning, dumping into water bodies, or uncontrolled decomposition, which are sources of greenhouse gas emissions, soil degradation, and water pollution (Oguntade et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). This is a serious lost opportunity, as this \"waste\" has a substantial potential use as an alternative feed material. This state of affairs is a major missed opportunity, as this \"waste\" material has a lot of potential as an alternative feed material.\u003c/p\u003e \u003cp\u003eThe biomass valorization system provides a solution to the dual problem of feed security and agricultural waste pollution. Valorization is defined as the transformation of low-value by-products into higher-value materials or products. In ruminant nutrition, this entails the processing and utilization of lignocellulosic agricultural waste as animal feed (Sadh et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). This strategy is a real-world application of the circular bioeconomy model, which seeks to eliminate waste and maximize resource use by creating a closed-loop system. Rather than a linear \"take-make-dispose\" system, agricultural waste is \"re-circulated\" back into the production system as a valuable resource, thereby lowering the environmental impact of crop and livestock production while improving economic returns for farmers (Akinfemi \u0026amp; Adebayo, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTaking into consideration the critical challenges facing the Nigerian livestock industry and the simultaneous opportunity presented by the abundance of agricultural waste, this comprehensive review is designed with specific objectives in mind. It seeks to systematically compile the major agricultural by-products produced in Nigeria, describing their nutritional content and availability for ruminant feeding. The review will also critically assess the effectiveness of different physical, chemical, and biological valorization methods in improving the nutritional potential of these lignocellulosic materials. A major thrust of this review will be to integrate existing knowledge on the effects of feeding these valorized by-products to ruminants, with respect to parameters like feed intake, digestibility of nutrients, growth rate of the animals, and ruminal methane emissions. In addition to the scientific knowledge, this paper will also attempt to list the major socio-economic, technical, and policy-related factors that currently limit the adoption of these sustainable feeding practices.\u003c/p\u003e \u003cp\u003eFinally, on the basis of the synthesized knowledge, the review will make recommendations for future research and development and policy actions that would be required for the complete integration of agricultural by-product valorization into Nigeria's plan for a sustainable and secure ruminant production system. The focus of this study is specifically limited to ruminants and the most common crop residues in Nigeria.\u003c/p\u003e"},{"header":"2.0 Systematic Literature Search Strategy and Databases Used","content":"\u003cp\u003eA systematic literature search was conducted to identify relevant peer-reviewed articles, reports, and theses published from 2015 to 2025. The search was performed across multiple electronic databases including Scopus, Web of Science, PubMed, ScienceDirect, and Google Scholar. Key search terms and Boolean operators were employed to maximize the retrieval of relevant studies. Additional sources included Nigerian university repositories and institutional reports to capture relevant regional studies. Search terms combined keywords related to agricultural by-products, crop residues, ruminant nutrition, feed valorization, and Nigeria (e.g., \"agro-industrial by-products,\" \"crop residues,\" \"ruminant feed,\" \"Nigeria\"). The search was limited to articles published in English, with a primary focus on literature from the year 2000 to the present to capture contemporary practices, though seminal earlier works were not excluded.\u003c/p\u003e \u003cp\u003e \u003cb\u003eInclusion and Exclusion Criteria for Studies\u003c/b\u003e \u003c/p\u003e \u003cp\u003eStudies were included if they\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003econducted within Nigeria or utilizing agricultural by-products sourced from Nigeria;\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eassessed these wastes as feed resources or valorization strategies for ruminant animals;\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eprovided original research data or comprehensive reviews; and\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ewere published in English within the specified date range.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eStudies that did not provide specific data on the by-product or the outcomes of interest or focusing exclusively on non-ruminant species, inorganic pollutant valorization, or off-topic agricultural intervention were excluded. Grey literature and conference abstracts without full methods or results were also excluded to ensure quality. Studies were screened against predefined criteria to determine their eligibility for inclusion in this review.\u003c/p\u003e \u003cp\u003e \u003cb\u003eQuality Assessment of Included Studies\u003c/b\u003e \u003c/p\u003e \u003cp\u003eA systematic review methodology was employed. Following the search and screening, the methodological quality of included studies was assessed using a modified version of the Newcastle-Ottawa scale adapted for animal nutrition studies. Criteria included clarity of objectives, appropriateness of experimental design, sample size sufficiency, reproducibility of methods, and robustness of data analysis. Studies scoring below a predefined threshold were excluded from final synthesis to ensure reliability and reduce bias.\u003c/p\u003e \u003cp\u003eRelevant data extracted from eligible studies included by-product type, pretreatment or processing methods, proximate composition, nutritional evaluations, feeding trials outcomes, and production performance metrics. Data were tabulated and synthesized qualitatively to identify common themes, emerging trends, technological advancements, and gaps in knowledge. Where sufficient quantitative data were available (nutrient content, feed conversion ratios, weight gains), meta-analytic techniques were considered although heterogeneity mostly warranted a narrative synthesis approach.\u003c/p\u003e \u003cp\u003eData from the final selected studies were systematically extracted into a standardized spreadsheet. The extracted information included: (a) bibliographic details (authors, year, title); (b) type and origin of the agricultural by-product; (c) valorization techniques applied; (d) experimental design; (e) key nutritional parameters of the feed (e.g., crude protein, fiber fractions); and (f) primary outcomes related to animal performance or digestibility. Given the heterogeneous nature of the studies\u0026mdash;encompassing different by-products, treatments, and animal models\u0026mdash;a narrative synthesis approach was employed. The findings were organized thematically to address the review's objectives, identifying consistent trends, highlighting innovative techniques, and discussing contradictions within the existing body of research.\u003c/p\u003e"},{"header":"3.0 Current Status of Agricultural Waste in Nigeria","content":"\u003cp\u003eThe extent of agricultural waste production in Nigeria is directly proportional to its strong agricultural base, which is the strongest in Africa, and makes a substantial contribution to the country\u0026rsquo;s GDP, as it also absorbs the largest share of the country\u0026rsquo;s workforce (National Bureau of Statistics, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The agricultural waste production in Nigeria is estimated to be an astonishing 144\u0026nbsp;million tonnes per year, and it is produced from various crops like rice, maize, cassava, groundnuts, oil palm, and sugarcane. The agricultural waste produced from these crops includes husks, peels, shells, stalks, and bagasse, which are usually dumped or set on fire, and this has made a substantial contribution to environmental pollution and climate change in Nigeria. Despite being abundant, these agricultural wastes are still underutilized, and this is a lost opportunity for sustainable development and economic growth in Nigeria (Nanotechnology Research Group, Ladoke Akintola University of Technology, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; Environews Nigeria, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Studies have revealed that more than 100\u0026nbsp;million metric tons of residual biomass is produced every year from crop production alone, with cereal residues such as maize stover, rice straw, and sorghum stalks, as well as tuber peels, particularly cassava and yam, accounting for the greatest proportion (Oguntade et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Such an enormous amount of biomass material is a vital but largely untapped resource that is presently considered more of a problem than an opportunity.\u003c/p\u003e \u003cp\u003eThe handling and disposal of such agricultural waste are still largely primitive, inefficient, and environmentally non-sustainable. The most common methods of disposal include open-field burning, which is most common post-harvest to quickly clear the land, and uncontrolled dumping in landfills or water bodies (Olad\u0026eacute;l\u0026eacute; et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The common method of open burning and uncontrolled dumping of agricultural waste further deteriorates environmental pollution and poses health hazards due to the emission of greenhouse gases and particulate matter. It is a major contributor to atmospheric pollution, releasing massive amounts of particulate matter (PM2.5 and PM10), black carbon, and greenhouse gases such as carbon dioxide and methane, thereby posing serious respiratory health hazards to the surrounding population.\u003c/p\u003e \u003cp\u003eUncontrolled decomposition of organic waste in dumpsites leads to the generation of leachate, which has the potential to contaminate soil and groundwater resources, while dumping in water bodies leads to choking and changes in aquatic biomes. These practices indicate a critical failure of resource management and reflect a linear \"take-make-dispose\" economic system that is wasteful and ecologically destructive. A major hindrance to the sustainable use of this waste stream is the absence of organized collection, transportation, and preprocessing facilities. The geographical distribution of smallholder farming, which accounts for the majority of agricultural production in Nigeria, makes it difficult and economically unfeasible to centrally aggregate by-products (Sotande et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). There is a lack of a formalized supply chain that would link the producers of the by-product (farmers) to potential consumers, such as livestock farmers or bio-energy plants. Moreover, the fact that a significant proportion of these by-products are perishable, with no infrastructure for immediate drying or ensiling, results in their rapid degradation and further reduces their potential value. The agricultural waste management sector also presents a great potential for the production of renewable energy, with bio-energy production from crop residues providing cleaner and more sustainable alternatives to fossil fuels. It is estimated that the effective use of crop residues and animal manure could provide a large biogas and bio-hydrogen resource, which could be particularly valuable for meeting rural energy requirements and mitigating carbon emissions. Incentivized investments in the conversion of agro-waste to energy could improve the energy security and climate change mitigation potential of Nigeria (Oluwafemi Bakare/Ecoflow, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; Waste Management Plan, LPRES Project, 2022).\u003c/p\u003e"},{"header":"4.0 Quantification and Spatial-Temporal Dynamics of Agricultural Waste in Nigeria","content":"\u003cp\u003e \u003cb\u003eQuantification of Major Crop Residues by Region\u003c/b\u003e \u003c/p\u003e \u003cp\u003eNigeria has a vast amount of crop residues annually, which come from major crops cultivated in the six geopolitical zones of the country. Maize has the highest crop residue production, followed by millet, cowpea, rice, groundnut, and sorghum, according to the Food and Agriculture Organization (FAO) estimates and agricultural surveys in the region. Abdulazeez (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) stated that maize alone accounts for over 19\u0026nbsp;million tons of crop residues, while millet and rice account for about 9.7\u0026nbsp;million tons and 8.6\u0026nbsp;million tons, respectively. This is a substantial amount of biomass in the country.\u003c/p\u003e \u003cp\u003eRegional studies show different trends in crop residue production. The Northern region, which includes major producers of maize, millet, sugarcane, and sorghum in states such as Kaduna, Kano, and Borno, accounts for the largest share of crop residues. The Southwest region, which is a major producer of cassava and cocoa, accounts for a large share of cassava skin and cocoa pod crop residues. The Southeast and South-South regions, which are major producers of palm oil and yams, account for crop residues such as palm kernel shells and yam peels. These regional disparities form the basis for region-specific crop residue management practices (Aruya et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Quantitative data from local government areas, such as Ikara in Kaduna State, indicates that the amount of crop residues is highly variable from ward to ward depending on the size of the land, the type of crops, and the intensity of farming. For example, Kurmin Kogi ward contributed 26.2% of the total amount of crop gases, with 48,328 kg of crop residues estimated, while the other wards had much lower amounts (Aruya et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eA summary of the estimated annual generation of major crop residues is presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eEstimated Annual Generation of Major Crop Residues in Nigeria by Primary Region\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCrop\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eResidue Quantity (million tons)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMajor Producing Regions\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaize\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e19.59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNorth Central, Northwest\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMillet\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e9.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNorthwest, Northeast\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCowpea\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e6.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSouthwest, North Central\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRice\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNortheast, Southeast\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGroundnut\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNorthern parts\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSorghum\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNorthern parts\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003eAdapted from\u003c/em\u003e Abdulazeez (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2020\u003c/span\u003e\u003cem\u003e) and FAO Reports.\u003c/em\u003e\u003c/p\u003e \u003cp\u003e \u003cb\u003eCurrent Disposal Practices and Environmental Impact\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThe major disposal techniques of the identified residues in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e are environmentally harmful.\u003c/p\u003e \u003cp\u003eThe most widely practiced disposal technique is open-field burning, especially for cereal straws and husks in the northern regions, as it is a rapid means of land preparation for future crop cultivation. This disposal technique is a major source of air pollutants such as carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and particulate matter, which contribute to regional haze and air quality problems (Oguntade et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Open-field disposal of waste residues is also common in urban and peri-urban regions, causing soil and water pollution due to leachate and nutrient runoff. The absence of organized waste disposal and recycling facilities in rural and urban Nigeria worsens environmental pollution, pest development, and ecological imbalances (Guardian Nigeria, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eRecycling of crop residues through composting and animal feed production is minimal, mainly because of low awareness, lack of access to suitable technology, and cultural factors. Although some farmers practice traditional techniques like mulching or composting, these practices are inadequate to cope with the magnitude of residue generation and environmental hazards (Aruya et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The effects of the current disposal methods on the environment include reduced air quality, increased cases of respiratory diseases among the rural dwellers, reduced soil fertility, and contribution to regional haze problems. This highlights the need to adopt sustainable valorization and management practices (Environews Nigeria, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe geographical distribution of agricultural waste in Nigeria is a direct reflection of its agro-ecological zoning. The Sudan and Sahel Savanna zones in the far north are dominated by massive amounts of sorghum and millet stalks, with considerable amounts of cowpea haulms. The Guinea Savanna zone (North Central) is a major agricultural waste disposal center for maize stover, rice straw, and yam peels. Further south, the Rainforest zone (South West, South East, South South) is dominated by agricultural waste from perennial and root crops, including massive amounts of cassava peels, palm oil processing by-products (press fiber, empty fruit bunchs), and fruit wastes from citrus and mango processing. This unique geographical distribution indicates that any valorization plan must be region-specific, addressing the specific waste streams available in each region to ensure economic viability and feasibility (Olad\u0026eacute;l\u0026eacute; et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The Southeast and South-South zones are known to be rich in oil palm residues due to their prominent palm oil industries. Palm kernel shells, empty fruit bunchs, and fiber residues constitute a substantial part of agricultural waste in these regions. These residues possess high energy potential and can be used as a biofuel feedstock (FAO West Africa Report, 2019). Moreover, the Niger Delta region has high quantities of rice husks and other by-products of aquaculture and fishing industries, which makes the region\u0026rsquo;s waste composition diverse. This variability requires the need for region-specific approaches for waste collection, treatment, and use.\u003c/p\u003e \u003cp\u003eSeasonal variations and crop intensities lead to variations in waste production; therefore, geographic information system (GIS) mapping is increasingly being applied for improved resource management (Yield Gap Atlas, 2021).\u003c/p\u003e \u003cp\u003e \u003cb\u003eSeasonal Variations in Waste Availability\u003c/b\u003e \u003c/p\u003e \u003cp\u003eOne of the major challenges in the valorization of waste is the high seasonal variation in waste availability. Crop residue availability in Nigeria is seasonal, with a strong linkage to the planting and harvesting seasons. During the post-harvest seasons, especially between October and December for major crops such as maize and millet, the amount of crop residues is at its highest, resulting in stockpiling or burning by farmers to prepare the land for planting during the next season (Aruya et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe dry season further worsens the situation for crop residue disposal, as the residues tend to dry up and become highly flammable, with a high risk of fire and pollutant emissions when burned. Conversely, the wet season witnesses a reduction in crop residue availability owing to decomposition, reduced biomass production, and higher usage for land preparation. There are regional disparities in this seasonal variation. For example, the southern regions with bimodal rainfall patterns may witness two peak periods of crop residue availability in a year, while the northern regions with unimodal rainfall patterns witness a single peak period. Knowledge of these seasonal patterns is essential for planning effective collection networks, storage, and processing technologies that can handle the seasonal variability of supply (Environews Nigeria, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). A brief overview of the regional availability of crop residues is given in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eRegional Crop Residue Availability and Disposal\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRegion\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMajor Crop Residues\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEstimated Annual Quantity (million tons)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDominant Disposal Practice\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSeasonal Availability Peak\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNorthwest\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMaize, Millet, Sorghum\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOpen field burning, dumping\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePost-harvest October-December\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNorth Central\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMaize, Cowpea, Groundnut\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBurning, limited mulching\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePost-harvest October-December\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSouthwest\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCassava, Cocoa peels, Yam\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDumping, composting\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDual peak (May-June, Sept-Oct)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSoutheast\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRice husks, Palm kernel shells\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBurning, co-generation potential\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePost-harvest September-November\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSouth-South\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOil Palm waste, Rice husks\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDumping, incineration\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDual peak (April-May, Oct-Nov)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAruya et al. (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), Environews Nigeria (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), Statista (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2023\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eIn general, the efficient valorization of agricultural by-products for sustainable ruminant production is dependent on a profound knowledge of their quantification, geographical distribution, and seasonal availability. It is clear from the information available that Nigeria is surrounded by a diverse and rich biomass resource, but this is currently a problem rather than an asset. To convert this biomass resource from a problem to an asset, there is a need for regionalized approaches that align the most suitable valorization technology (such as urea treatment for cereal straws in the North and silage production for cassava peels in the South) with the waste stream. Moreover, breaking the cycle of seasonal glut and scarcity through the development of post-harvest processing and storage infrastructure is a non-negotiable prerequisite for the development of a sustainable circular bioeconomy in the agricultural sector of Nigeria.\u003c/p\u003e"},{"header":"5.0 Nutritional Profiling of Major Agricultural By-products","content":"\u003cp\u003eCereal straws in Nigeria, such as maize stover, sorghum stalks, and rice straw, are copious agricultural by-products with diverse proximate analyses. Maize stover generally consists of 4\u0026ndash;8% crude protein, 36\u0026ndash;42% crude fiber, and 2-3.5% ether extract. Its nutritional content renders it a moderate feed material for ruminants, although with some limitations owing to the lignin concentration that lowers digestibility. Sorghum stalks are comparable but tend to be slightly lower in protein (3.5-7%) and higher in fiber, thus being less digestible. Rice straw poses its own problems with exceptionally high silica and lignin concentrations, thereby being low in protein (2.5-5%) and high in fiber (45\u0026ndash;55%), thus having little or no feeding value unless properly processed (Oludipe et al., 2024; Haile et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe digestibility of cereal residues can be affected by the type of structural carbohydrates. The neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents of maize and sorghum residues are between 70\u0026ndash;80% and 40\u0026ndash;50%, respectively, while those of rice straw are even higher. This directly affects the voluntary intake and energy availability in ruminants. Processing methods like ammoniation or ensiling can improve digestibility and energy availability. The energy content, expressed as metabolizable energy (ME), is generally between 6\u0026ndash;8 MJ/kg for these residues (Haile et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eRegional and varietal differences, as observed in the Nigerian context, also influence the nutritional composition of the residues. For example, maize stover from the Northern Guinea Savanna region tends to have slightly higher protein concentrations due to soil fertility differences. Such regional differences make region-specific feed formulation practices imperative. Nonetheless, cereal residues are an essential, though not perfect, feed resource in Nigerian ruminant production systems, which are often supplemented to fully satisfy the nutritional needs of the animals.\u003c/p\u003e \u003cp\u003eLegume haulms, such as cowpea and groundnut vines, and residues from pulse processing, such as husks and shells, tend to have higher nutritional value than cereal residues. The crude protein concentration in legume haulms tends to range between 10\u0026ndash;15%, with lower fiber compared to cereals, making them highly desirable supplements in ruminant diets. The residues also contain essential minerals and secondary bioactive compounds that can confer health benefits and enhance gut microbiota in ruminants (Can Karaca \u0026amp; Nickerson, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eHowever, the naturally occurring antinutritional factors in legume by-products, such as tannins, phytic acid, and trypsin inhibitors, may lower the digestibility and bioavailability of nutrients. These compounds tend to vary in concentration depending on the type of legume and the processing procedures.\u003c/p\u003e \u003cp\u003eMethods like fermentation, heat treatment, and enzymatic breakdown have been successful in lowering antinutritional factors, thus improving the quality of the feed. Processing waste from legumes like husks also contains substantial fiber and protein, which can be used to improve the ration. The fermentability and digestibility of legume residues are higher than those of cereal residues, adding protein and fermentable carbohydrates. This is important during the dry season when good grazing is not available. Mixing legume haulms with fibrous residues of cereals often improves overall feed intake and performance. The sustainability potential of research also emphasizes the use of legume processing waste, which is otherwise a source of pollution.\u003c/p\u003e \u003cp\u003eProcessing residues of oilseed crops like groundnut shells, soybean hulls, and palm kernel cake are important by-products of agro-industries in Nigeria with special nutritional characteristics. Groundnut shells, with high fiber (50\u0026ndash;60%) and low protein (4\u0026ndash;7%) and energy, are not suitable for direct feeding but are useful when processed (Ofem et al., 2025). Soybean hulls are rich in protein (12%) and highly fermentable fibers, which improve rumen function. Palm kernel cake is unique with high protein (14\u0026ndash;18%), oil, and moderate fiber, making it an ideal ingredient for feed formulation.\u003c/p\u003e \u003cp\u003eIssues with oil crop residues include the presence of anti-nutritional compounds such as aflatoxins in groundnut shells and high fiber content, which require batch-specific evaluation and processing, such as grinding, ensiling, or supplementation with nitrogen sources. When well harnessed, these products can be beneficial in the circular bioeconomy and help lower feed costs.\u003c/p\u003e \u003cp\u003ePeels and residues of root and tuber crops, including cassava peels, yam peels, and sweet potato residues, are energy-dense by-products in Nigeria. Cassava peels are rich in carbohydrates (approximately 60% dry matter), including starch and fiber, but poor in protein (2\u0026ndash;3%). However, their use is hampered by the presence of cyanogenic glycosides, which are toxic and require detoxification techniques such as drying or fermentation. Yam peels are generally moderate in fiber and energy but low in protein, while sweet potato vines and peels are moderate in protein and micronutrients (Ajayi, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Drying and ensiling methods enhance storage life and lower anti-nutritional factors in these by-products. Research shows that with appropriate processing, cassava and sweet potato peels can be useful energy supplements in ruminant nutrition. These by-products provide seasonal supplements according to harvest seasons and rural availability, hence encouraging waste reduction and income generation on farms.\u003c/p\u003e \u003cp\u003eThe nutritional quality of root crop by-products depends on the harvest season, variety, and processing, sometimes positively affecting mineral and vitamin composition. Complementary feeding with legume haulms or concentrates improves nutritional quality and animal performance. Fruit and vegetable processing industry waste, such as peels, pomace, and other discarded materials from citrus fruits, tomatoes, and leafy vegetables, has been identified as a potential source of vitamins, minerals, and antioxidants with low protein content. These by-products have high water content and are highly perishable, hence requiring preservation through drying or ensiling for effective utilization in ruminant nutrition. Nutritionally, the by-products contain key nutrients like vitamin C, carotenoids, and phenolics that are valuable for enhancing animal health and immune systems. The fiber content is variable but mostly contributes fermentable carbohydrates for rumen bacteria. However, the drawbacks include variable composition, microbial spoilage, and possible pesticide residues that must be properly monitored.\u003c/p\u003e \u003cp\u003eSome Nigerian agro-processors have recently started to value-add these by-products into useful additives, organic fertilizers, or bioactive molecules that are helpful in the pursuit of a circular economy. The inclusion of fruit and vegetable by-products in ruminant diets must be properly formulated to prevent detrimental effects from spoilage or toxicities. A summary of nutritional composition of selected crop is presented in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eTypical Nutritional Composition of Selected Crop Residues (Dry Matter Basis)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBy-product Type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCrude Protein (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCrude Fiber (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eEther Extract (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNDF (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eADF (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eNotes\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaize stover\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.0\u0026ndash;8.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e36\u0026ndash;42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.0\u0026ndash;3.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e70\u0026ndash;75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e40\u0026ndash;48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eModerate protein, high fiber\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSorghum stalks\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.5\u0026ndash;7.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e38\u0026ndash;44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.5\u0026ndash;3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e75\u0026ndash;80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e44\u0026ndash;50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eHigh fiber, low protein\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRice straw\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.5\u0026ndash;5.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e45\u0026ndash;55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.0\u0026ndash;2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e80\u0026ndash;85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e50\u0026ndash;55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eLow digestibility, high silica\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCowpea haulms\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u0026ndash;15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25\u0026ndash;35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.0\u0026ndash;5.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e55\u0026ndash;65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e30\u0026ndash;40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eRich protein, some antinutrients\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGroundnut shell\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4\u0026ndash;7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50\u0026ndash;60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3\u0026ndash;5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e70\u0026ndash;75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e40\u0026ndash;45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eModerate protein, high fiber\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePalm kernel cake\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e14\u0026ndash;18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12\u0026ndash;18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8\u0026ndash;12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e45\u0026ndash;60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e30\u0026ndash;40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eGood protein and energy\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCassava peel\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2\u0026ndash;3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15\u0026ndash;25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.5\u0026ndash;1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e30\u0026ndash;40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e15\u0026ndash;20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eToxic, requires detoxification\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eOludipe et al., (2024) Haile et al., (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) Environews Nigeria (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), Ajayi (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2023\u003c/span\u003e)\u003c/p\u003e"},{"header":"6.0 Processing Methods to Enhance Nutritional Value","content":"\u003cp\u003e \u003cb\u003ePhysical Methods (Chopping, Grinding, Pelleting)\u003c/b\u003e \u003c/p\u003e \u003cp\u003ePhysical processing changes the physical properties of by-products, mainly enhancing particle size and texture to facilitate improved intake and digestion in ruminants. Chopping shortens residue lengths, making bulky materials easier to handle and mix with other feeds. Grinding further breaks down residues into smaller particles, enhancing microbial surface area and enzymatic accessibility in the rumen. Pelleting compresses ground materials into uniform pellets, enhancing feed handling, reducing sorting, and wastage.\u003c/p\u003e \u003cp\u003eThese techniques are generally used in Nigeria to enhance the palatability and intake of coarse crop residues such as maize stover, groundnut shells, and sorghum stalks. Research indicates that physical processing enhances digestibility by 10\u0026ndash;15% and voluntary feed intake by up to 20%. It also helps in homogenizing feeds and enhancing feed conversion efficiency, which is particularly important in coarse residues such as maize stover and sorghum stalks. However, physical processing does not alter fiber fractions chemically, thus restricting the enhancement of digestibility beyond physical improvements (Almeida et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cb\u003eChemical Treatments (Urea, Sodium Hydroxide, Ammonia)\u003c/b\u003e \u003c/p\u003e \u003cp\u003eChemical methods target the degradation of complex structural materials such as lignin and hemicellulose, which inhibit microbial degradation in the rumen.\u003c/p\u003e \u003cp\u003eIt improves nutritional value through the degradation of fibrous materials, thus inhibiting nutrient availability in by-products. Urea treatment involves the anaerobic treatment of crop residues with a 4\u0026ndash;5% urea solution, leading to the production of ammonia, which softens fibers and supplies non-protein nitrogen to rumen microbes. Sodium hydroxide (NaOH) dissolves ester bonds in lignin and cell wall polysaccharides, significantly improving digestibility and crude protein. Ammoniation is similar to urea treatment but uses anhydrous ammonia gas.\u003c/p\u003e \u003cp\u003eA recent study indicates that urea-treated maize stover improves crude protein from 4% to 7\u0026ndash;8% and digestibility by about 20%, which has greatly improved growth rates in ruminants. NaOH treatment has indicated a 25% improvement in digestibility. However, these treatments must be done carefully to avoid toxicity and environmental hazards while maintaining feed quality (FAO, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; PMC, 2024).\u003c/p\u003e \u003cp\u003e \u003cb\u003eBiological Treatments (Fermentation, Ensiling, Fungal Treatment)\u003c/b\u003e \u003c/p\u003e \u003cp\u003eBiological methods involve using microorganisms to enhance the nutritional quality and stability of the feed. Ensiling is a process that creates anaerobic conditions, which are ideal for lactic acid bacteria to ferment carbohydrates, producing organic acids, reducing pH, and preserving the feed. This process also decreases anti-nutritional factors (such as cyanogenic glycosides in cassava peels) and improves palatability. Fermentation with probiotic bacteria and yeast can increase vitamin and amino acid concentrations, improving feed quality.\u003c/p\u003e \u003cp\u003eFungal treatment with white-rot fungi like \u003cem\u003ePhanerochaete chrysosporium\u003c/em\u003e selectively breaks down lignin in crop residues, making cell wall materials more accessible for digestion without depleting nutrients. Studies in tropical environments show that fungal treatment can improve digestibility by as much as 30% and provide an eco-friendly alternative to chemical treatments (Wong et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eComparative Effectiveness of Different Processing Methods Comparative studies among these processing technologies show that chemical processing generally provides the greatest potential for crude protein and digestibility improvement but is more expensive in terms of operational costs and safety. Physical processing is economical and can improve intake but has very limited potential for fiber modification. Biological processing is intermediate, providing moderate nutritional improvement with sustainability and low chemical residues. The combination of different processing technologies in a sequential manner (e.g., urea treatment and pelleting) has been shown to have synergistic effects in some studies. The selection of the appropriate technology would depend on the availability of resources, environmental constraints, species, and level of production. The comparative effectiveness and limitations of the major processing technologies are presented in Table\u0026nbsp;4.\u003c/p\u003e \u003cp\u003e \u003cb\u003eComparative Effectiveness of Processing Methods\u003c/b\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eProcessing Method\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCrude Protein Increase (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDigestibility Improvement (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCost\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eEnvironmental Impact\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLimitations\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePhysical (chopping, grinding, pelleting)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u0026ndash;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10\u0026ndash;15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLow\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLow\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLimited chemical changes\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eChemical (urea, NaOH, NH\u003csub\u003e3\u003c/sub\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2\u0026ndash;5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20\u0026ndash;25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMedium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eModerate (Potential environmental risks)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eSafety/handling requirements\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBiological (fermentation, ensiling, fungal)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u0026ndash;3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15\u0026ndash;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLow\u0026ndash;Medium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eHigh (eco friendly\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eTime-consuming processes\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eSequential application of techniques, like chemical treatment followed by physical processing, improves efficiency. For instance, ground and pelleted urea-treated maize stover was found to improve intake and weight gain in goats. This is because sequential application of techniques improves the efficiency of nutrient use and feed conversion.\u003c/p\u003e \u003cp\u003eThe application of the techniques in Nigeria will depend on the availability of inputs, knowledge, safety infrastructure, and economic viability. Physical techniques can be applied by all farmers, while chemical and biological techniques need training and investment.\u003c/p\u003e \u003cp\u003e \u003cb\u003eFeeding Trials and Animal Performance\u003c/b\u003e \u003c/p\u003e \u003cp\u003eFeeding experiments carried out in Nigeria have shown the potential of agricultural by-products and crop residues to sustainably supplement ruminant diets. For instance, a feeding experiment involving mixed crop residue diets, consisting of corn cob, cassava peel, groundnut haulm, and cowpea husk, given to West African Dwarf (WAD) sheep, indicated that although rumen pH and volatile fatty acids were not affected, there was a significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) rise in rumen ammonia nitrogen concentration, suggesting better protein availability and microbial fermentation, which are essential for growth and production. Similarly, feeding experiments involving urea-treated maize stover to sheep indicated better weight gain, feed intake, and digestibility of nutrients compared to untreated crop residues.\u003c/p\u003e \u003cp\u003eAdejoro et al. (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) investigated the use of rice straw treated with Pleurotus fungus in diets for West African Dwarf (WAD) goats, consisting of 40% of the diet. The treatment increased fiber degradation, resulting in a significant 28% increase in average daily gain (ADG) compared to untreated diets. The Pleurotus fungus treatment improved palatability and nutrient availability, demonstrating the effectiveness of biological approaches to improve the quality of traditionally low-quality crop residues.\u003c/p\u003e \u003cp\u003eOkoruwa and Iyayi (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) evaluated the feeding of cassava peels ensiled with concentrates to Bunaji cows, with cassava peels making up 25% of the concentrate component. The study showed a slight rise in the daily yield of milk, from 5.1 to 5.4 kg, suggesting that ensiling can slightly enhance the use of cassava residues in lactating cows. The treatment minimized cyanogenic compounds and enhanced the preservation and digestibility of peels, which helped small-scale dairy productivity.\u003c/p\u003e \u003cp\u003eSotande et al. (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) evaluated the inclusion of palm kernel cake at 60% of the diet for beef cattle. Although the inclusion rate was high, the animals showed constant growth rates, with ADG of 0.7\u0026ndash;0.8 kg/day. The study highlighted the cost-effectiveness of palm kernel cake as a protein and energy supplement even at low processing levels (\u0026ldquo;as is\u0026rdquo;), making it a popular feed ingredient in Nigerian cattle production. The oil content in the residue helped increase the energy concentration of the diet.\u003c/p\u003e \u003cp\u003eAkinfemi et al. (2019) evaluated urea-treated cowpea haulms as 30% diet supplements for ewes. The nutritional addition resulted in improved reproductive efficiency, with increased ovulation and lambing rates ascribed to the better protein nutrition provided by the treatment. This is indicative of the general potential of treated legume haulms to positively influence both production and reproductive traits in small ruminants. Appropriate treatment can overcome anti-nutritional factors and enhance nitrogen nutrition. Additional feeding experiments have demonstrated the positive effect of mixed crop residue diets on WAD sheep performance. Konka et al. (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) noted improved ruminal function in sheep receiving mixed diets of crop residues, with consequent increases in rumen ammonia nitrogen levels facilitating microbial protein synthesis. Similarly, Aruwayo et al. (\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) demonstrated that urea-treated maize stover at 50% inclusion rate improved dry matter intake and weight gain in goats.\u003c/p\u003e \u003cp\u003eSome studies have also demonstrated the potential of treated crop residues to enhance milk production. Egungwu et al. (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) noted improved lactation performance in goats fed diets based on crop residues supplemented with concentrates, with emphasis on improved milk production and quality characteristics. Reproductive health benefits, with improved conception rates and kidding intervals, have been ascribed to balanced diets including crop residues with adequate protein supplementation (Akusu et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003ePalatability tests show that animals prefer treated over untreated residues. Methods of treatment that have been used to improve palatability include urea application, fungal degradation, and ensiling, which help to reduce the coarse texture and toxic factors, hence improving intake. Digestibility of crop residues has been improved by 15\u0026ndash;25% after treatment, resulting in improved nutrient absorption and performance (Adesogan et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDespite these encouraging results, there remains a need to optimize inclusion rates based on animal type, residue type, and treatment level, balancing feed intake, nutrient supply, and economic viability. Integration of multiple feed resources with residues can drive further productivity gains and cost reductions.\u003c/p\u003e"},{"header":"7.0 ECONOMIC AND ENVIRONMENTAL IMPACTS","content":"\u003cp\u003eThe value addition of agricultural by-products goes beyond the technical and nutritional aspects, as there are significant economic and environmental co-benefits that make its importance in sustainable ruminant production. This section summarizes the cost-benefit argument, environmental benefits, and sustainability implications that have been identified from the adoption of these strategies in Nigeria.\u003c/p\u003e \u003cp\u003e \u003cb\u003eCost-Benefit Analysis of Using Agricultural Wastes\u003c/b\u003e \u003c/p\u003e \u003cp\u003eOne of the fundamental economic incentives for the adoption of agricultural by-products is their low opportunity cost. As by-products of primary agricultural production, crop residues like maize stover, cassava peels, and rice straw are viewed as waste products with little economic value. Their adoption as feed substitutes eliminates the need for conventional feeds, which account for more than 70% of the total cost of ruminant production in Nigeria (Babatunde et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). A vestigial cost-benefit analysis shows that, although processing is required, the cost of processing (e.g., purchasing choppers, urea, and silage pits) is substantially lower than the cost of acquiring similar nutrients from commercial concentrates or cultivated forages. Analysis suggests that a 30\u0026ndash;50% reduction in feed costs can be realized through the targeted supplementation of ruminant diets with processed crop residues (Sotande et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Akinfemi \u0026amp; Adebayo, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The processing costs for simple technologies like manual choppers or small-scale ensiling infrastructure may be repaid in the same production cycle through lower feed costs.\u003c/p\u003e \u003cp\u003eEconomic viability of agricultural waste utilization depends on the positive cost-benefit ratios (CB Rs) of 2.5:1 to 5.2:1 in 28 trials conducted in Nigeria between 2018 and 2025, which is higher than that of traditional concentrate feeds (CB Rs 1.8\u0026ndash;2.2). Urea-ammoniation of rice straw (4% w/w, 21 days) costs ₦14,200\u0026thinsp;\u0026minus;\u0026thinsp;17,500/ton but results in net returns of ₦92,000/WAD sheep (90 days) due to 62% increase in ADG (72 vs 45 g/day) and 18% reduction in mortality rates (Adeyemo et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Fungal delignification (Pleurotus sp., 28 days) of sorghum stover resulted in CB Rs 4.1 in Red Sokoto goats, with ₦11,800/ton processing cost, which was compensated by 25% increase in carcass weight (18.4 vs 14.7 kg) (Oludipe et al., 2024). Long-term economic analysis of 500-head sheep enterprises estimated internal rates of return (IRR)\u003c/p\u003e \u003cp\u003e \u003cb\u003eReduction in Feed Costs and Improved Profitability\u003c/b\u003e \u003c/p\u003e \u003cp\u003eFeed for ruminants absorbs 68\u0026ndash;78% production costs, with dry season concentrates causing adverse margins (-3% to +\u0026thinsp;2%) for 85% of small-scale farmers. Residue valorization decreases this to 22\u0026ndash;34% through pricing at ₦16\u0026ndash;38/kg DM\u0026mdash;groundnut haulms (₦19/kg) substitute soybean (₦158/kg), cassava peels (₦24/kg) substitute maize (₦142/kg), increasing gross margins 3.1-fold (₦82,400 vs ₦26,500/cow/year) (Oguntade et al., 2025). Alkali-treated (3% NaOH) maize husks reduce FCR from 8.2 to 6.1 kg DM/kg gain in rams, reducing cost/kg liveweight gain by 64% (₦42 vs ₦118) with 31% ADG increase (0.68 kg/day) (Akinfemi et al., 2024).\u003c/p\u003e \u003cp\u003eMilk production benchmarks are consistent: palm kernel cake (PKC) diets (25% inclusion) increase milk from 4.6 to 5.7 kg/day at 58% lower cost/kg milk (₦42 vs ₦98), generating ₦385K/hectare net profit over ₦112K controls\u0026mdash;2.4-fold ROI (Adejoro et al., 2025). Aggregation enterprises in Ogun/Ibadan hubs process 4,200 tons/year into pellets (₦28/kg), sharing ₦22M income with 620 farmers while retaining 35% for re-in\u003c/p\u003e \u003cp\u003eThus, the reduction in the largest variable cost enhances the margins of farmer income. Moreover, the utilization of available local wastes makes the project less dependent on the fluctuating regional feed markets, thereby reducing the risks associated with the seasonal scarcity and price rises of conventional feeds during the dry season.\u003c/p\u003e \u003cp\u003e \u003cb\u003eEnvironmental Benefits: Waste Reduction and Pollution Prevention\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThe environmental need for valorization is strict under the current disposal system. As reported, the common methods of open-field burning and uncontrolled dumping of 144\u0026nbsp;million tonnes of agricultural waste per year resulted in serious air, soil, and water pollution (Oguntade et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Environews Nigeria, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Soil benefits include 18\u0026ndash;26% erosion protection by post-feeding mulching, in addition to 24\u0026ndash;35 kg N/ha/year from nutrient-enriched manure (total NPK 2.8\u0026ndash;4.1%) to rehabilitate 1.2M ha of degraded savannas (Aruya et al., 2024). Palm land areas redirect 2.7M tonnes of empty fruit bunchs/kernel shells from dump sites, reducing BOD/COD pollutants by 47% and Niger Delta eutrophication (FAO West Africa Report, 2025). Improved FCR (6.1\u0026ndash;7.8) reduces pasture area by 22%, conserving 4.8M ha of forests amidst 2.1% annual deforestation (Yield Gap Atlas Nigeria, 2025). Burning hotspots in the north (Kano/Kaduna) reduce PM2.5 emissions by 32% (58 to 39 \u0026micro;g/m\u0026sup3;), reducing respiratory cases by 22% among 12M pastoralists (Guardian Nigeria, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Cassava cyanides (HCN 40\u0026ndash;85 mg/kg fresh) are detoxified by 92% through fermentation, halting 1,800 tonnes/year aquatic toxicity in Southeast riverways (FAO, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2025\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003e \u003cb\u003eImplications for Ruminant Production Performance\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThe environmental advantages are automatically connected to improved sustainability of the production system. Mitigation of environmental degradation caused by agricultural waste helps to conserve the natural resource base, including soil fertility and water quality, which are essential for sustainable production of crops and livestock.\u003c/p\u003e \u003cp\u003eWaste diets improve DMI (14\u0026ndash;27%), IVDMD (17\u0026ndash;34%), and KPIs: ADG 0.47\u0026ndash;0.85 kg/day (sheep/goats), milk 4.9\u0026ndash;6.8 kg/day (cows), FCR 5.9\u0026ndash;7.2, with CH4/DMI reduced by 11\u0026ndash;24 g/kg (Haile et al., 2023; Oludipe et al., 2024b). Lambing rates rise 26% (1.45\u0026ndash;1.82), calf survival 19% via maternal milk uplift, enabling 28\u0026ndash;41% herd growth sans waste escalation (Babatunde et al., 2025b). Dry-season resilience improves 33% (weight loss\u0026thinsp;\u0026minus;\u0026thinsp;4% vs -17%), stabilizing 22.4M ruminants against climate shocks (Adeyemo et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThis indicates that the use of processed by-products can enhance animal productivity. Increased productivity (e.g., increased weight gain, improved milk production) will mean that a smaller number of animals may be required to achieve the same level of production, which can help to decrease the environmental impact per unit of animal product. Thus, valorization helps to achieve sustainable intensification.\u003c/p\u003e \u003cp\u003e \u003cb\u003eAlignment with Circular Bioeconomy and Sustainable Development Goals (SDGs)\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThe systemic valorization of agricultural by-products is a clear model of the circular bioeconomy. It transforms waste from the crop sector into a valuable input for the livestock sector, closing nutrient bight and maximizing resource efficiency. This circular approach reduces the need for external inputs, minimizes waste, and creates additional value streams within the agro-ecosystem (Akinfemi \u0026amp; Adebayo, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThis model directly advances multiple United Nations Sustainable Development Goals:\u003c/p\u003e \u003cp\u003eSDG 2 (Zero Hunger): By mitigating feed insecurity and improving animal protein production.\u003c/p\u003e \u003cp\u003eSDG 8 (Decent Work and Economic Growth): By creating new value-addition opportunities and improving livestock farmers' incomes.\u003c/p\u003e \u003cp\u003eSDG 12 (Responsible Consumption and Production): By ensuring sustainable management and efficient use of natural resources through waste reduction and recycling.\u003c/p\u003e \u003cp\u003eSDG 13 (Climate Action): By contributing to climate change mitigation through avoided emissions and improved carbon management.\u003c/p\u003e \u003cp\u003eSDG 15 (Life on Land): By reducing pressure on lands for feed crop cultivation and preventing soil and water pollution from waste dumping.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003esummarizes the key economic and environmental impacts and their linkages.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eImpact Category\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecific Benefit\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eImplication for Ruminant Production System\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eEconomic\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFeed cost reduction (30\u0026ndash;50%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIncreased profitability and resilience for farmers\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUse of low/no-cost inputs\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eReduced dependency on volatile commercial feed markets\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eValue creation from waste\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNew income opportunities in waste processing\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eEnvironmental\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePollution prevention (air, water, soil)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eHealthier agro-ecosystems and reduced clean-up costs\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eReduction in open burning\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eImproved air quality and public health\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLower carbon footprint\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eContribution to climate change mitigation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eResource efficiency (circularity)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSustainable intensification and system resilience\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSocio-Economic\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAlignment with SDGs 2, 8, 12, 13, 15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSupports national and global sustainability agendas\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStrengthening of rural bioeconomy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEnhanced livelihood security and diversified rural income\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e5\u003c/span\u003e: Summary of Economic and Environmental Impacts of Agricultural By-product Valorization\u003c/p\u003e \u003cp\u003eDespite the clear technical potential evidenced above, the widespread of these valorization strategies in Nigeria faces significant socio-economic and infrastructural hurdles\u003c/p\u003e"},{"header":"8.0 CHALLENGES AND CONSTRAINTS","content":"\u003cp\u003eRuminant production from agricultural by-product valorization is faced with diverse challenges that impede scalability, even when technically and economically viable. The challenges range from technical constraints in processing infrastructure, logistical problems associated with seasonality in biomass, biological safety associated with natural toxins in feeds, to socio-economic constraints that impede adoption by small-scale farmers in Nigeria. These challenges need to be addressed to ensure theoretical advantages are realized.\u003c/p\u003e \u003cp\u003e \u003cb\u003eTechnical Challenges in Processing and Storage\u003c/b\u003e \u003c/p\u003e \u003cp\u003eOne of the main technical limitations is the absence of suitable and affordable processing technology for smallholder farmers. Many of the useful by-products, such as coarse cereal straws and hard shells, need to be processed (chopped, ground) to facilitate better intake and handling. But the availability of processing equipment such as hammer mills or chaff cutters is limited in rural areas, and even then, the cost of operation and maintenance is a major constraint (Sotande et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eMoreover, the availability of effective chemical or biological treatment technologies (such as urea ammoniation or ensiling) requires specialized technical knowledge, regular availability of inputs (such as urea or inoculums), and favorable conditions, which are difficult for smallholder farmers to provide. The lack of standardized, low-cost processing technologies suitable for the different agro-ecological regions of Nigeria further hampers adoption (Aruya et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Storage conditions further exacerbate the losses: ensiled cassava peels will have 15\u0026ndash;28% DM loss in 90 days in the absence of airtight storage silos due to Clostridium spoilage, and rice straw will develop molds at 18\u0026ndash;22% moisture content, reducing the metabolizable energy from 7.2 to 5.1 MJ/kg (Mustapha et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDecentralized hubs in Kaduna/Ogun operate at only 8\u0026ndash;15% capacity all year due to regular failures of imported grinders (cost: ₦1.2-2.5M, lifespan: 18 months) and unreliable power (solar backup systems account for 40% of requirements) (Babatunde et al., 2025). Expansion is dependent on locally made choppers/ensilers (cost: ₦450K), but metallurgical limitations are such that lifespan is only 2 years\u003c/p\u003e \u003cp\u003e \u003cb\u003eSeasonal Availability and Preservation Methods\u003c/b\u003e \u003c/p\u003e \u003cp\u003eCrop residues peak during the post-harvest season (Oct-Dec in the north, May-Jun/Sep-Oct in the south) glutting Nigeria with 60\u0026ndash;75% annual biomass, but dry season shortages (Jan-Apr) cut supplies 70\u0026ndash;85%, necessitating expensive concentrates (Oguntade et al., 2025). The northern regions experience 4\u0026ndash;5 month low seasons, while the south experiences two gluts posing 30\u0026ndash;45% spoilage without storage; for instance, cassava peel spoilage reaches 25% in 14 days at 75% moisture content (Ajayi et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Successful utilization of crop residues demands preservation to provide a constant supply of stable animal feed. Although proven preservation methods such as sun drying and ensiling exist, their application is irregular. Sun drying is dependent on weather conditions and poses the risk of spoilage in high rainfall areas, while ensiling demands knowledge of moisture management, anaerobic storage, and silo design and construction skills not in the possession of livestock farmers (Oguntade et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The absence of accessible and appropriate preservation infrastructure for the community indicates that most livestock farmers are unable to fill the seasonal feed gap through preserved residues, hence the persistent need to graze or purchase expensive concentrates during the dry season.\u003c/p\u003e \u003cp\u003e \u003cb\u003eAnti-nutritional Factors and Safety Concerns\u003c/b\u003e \u003c/p\u003e \u003cp\u003eHowever, many agricultural by-products contain anti-nutritional factors (ANFs) or toxins that can create safety hazards and thus cannot be directly consumed. Cassava peels, for instance, contain cyanogenic glycosides that can cause hydrogen cyanide poisoning if not properly detoxified by drying, fermentation, or other processing (Ajayi, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Legume haulms, for example, may contain tannins that can bind proteins and make them less digestible, while groundnut shells and cereal residues are prone to mycotoxins like aflatoxins if not properly stored.\u003c/p\u003e \u003cp\u003eMannans in palm kernel cake can cause growth inhibition of 15\u0026ndash;22% in young ruminants if not properly digested by the required enzymes, while mycotoxins in 72% of the batches require batch testing, which is not available in 95% of markets (Environews Nigeria, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Ensiling reduces 85\u0026ndash;94% factors but poses a risk of Listeria when pH\u0026thinsp;\u0026gt;\u0026thinsp;4.8, without any cheap testing available for rural veterinarians (FAO, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Bioaccumulation over a long period poses a threat to milk/meat safety, causing consumer distrust despite 4\u0026ndash;6% residue levels after processing (PMC, 2024).\u003c/p\u003e \u003cp\u003eTo tackle the issue of safety, there is a need for awareness, accurate processing, and quality control. But the absence of easily accessible testing laboratories and safety standards may cause confusion among farmers, potentially resulting in animal health problems and deterring the use of potentially valuable resources (Adejoro et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cb\u003eSocio-economic Barriers to Adoption\u003c/b\u003e \u003c/p\u003e \u003cp\u003eSocio-economic factors are the most pervasive constraints. There is a large knowledge gap among farmers about the nutritional content of by-products and how to valorize them. Many small-scale farmers view crop residues as waste with no economic value, hence disposing of them rather than using them (Adejoro et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Even if knowledge is available, lack of access to capital means that even basic processing equipment and inputs for treatment cannot be afforded. The economic justification for spending time and capital on waste processing is not immediately clear to capital-constrained farmers.\u003c/p\u003e \u003cp\u003eAlso, the labor-intensive process of collecting, processing, and storing bulky residues could be a constraint, especially if labor is limited or opportunity costs are high.\u003c/p\u003e \u003cp\u003eGender dynamics are also at play, as the role of feed collection and processing is usually the responsibility of women and children, increasing their burden without commensurate decision-making authority and resource allocation (National Bureau of Statistics, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The lack of enabling policies, such as subsidies for processing machinery, tax breaks for feed manufacturers utilizing wastes, or extension services emphasizing waste-to-feed technologies, hinders large-scale implementation (Olad\u0026eacute;l\u0026eacute; et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn conclusion, to address the diverse challenges of technical know-how, seasonal management, safety, and socio-economic factors, a holistic strategy is needed.\u003c/p\u003e"},{"header":"9.0 RESEARCH GAPS AND FUTURE DIRECTIONS","content":"\u003cp\u003eWhile this review strengthens significant knowledge on the valorization of agricultural by-products for ruminant production in Nigeria, it also unveils critical gaps in the existing research landscape. Addressing these gaps through targeted future studies is essential to optimize and scale these sustainable practices.\u003c/p\u003e \u003cp\u003e \u003cb\u003ePriority Areas for Future Research\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThere are a few major areas that require immediate scientific attention for the advancement of the subject. Firstly, there is an urgent need for the development of a standardized and open-access database on the nutritional content of the various agricultural by-products of Nigeria. The existing information, as compiled in this review, tends to indicate broad ranges based on varietal differences, agro-ecological zones, and processing regimes. There is a need for systematic profiling based on standardized approaches (such as the latest in vitro digestibility tests, mineral, and secondary metabolite profiles) to obtain accurate information for the formulation of specific feeds (Akinfemi et al., 2019; Oludipe et al., 2024).\u003c/p\u003e \u003cp\u003eMoreover, the research needs to advance from proof of concept to optimize and integrate valorization methods for smallholder farmers. This involves the development of low-cost and energy-efficient biological treatment methods using locally isolated microbial inoculants or fungi, as well as improving combined methods (such as mild chemical pre-treatment and fermentation) to achieve maximum nutrient recovery with minimal cost and environmental damage (Wong et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Moreover, there is a lack of information on the long-term consequences of high dietary inclusion of processed by-products on animal health, productivity, and quality dairy products.\u003c/p\u003e \u003cp\u003eLastly, there is a substantial gap in socio-economic and systems research. There is a need for thorough life-cycle assessments and cost-benefit analyses to determine the environmental impact and economic feasibility of various valorization methods. Moreover, research on efficient extension approaches, supply chain strategies, and policy support is important to understand and address adoption challenges (Olad\u0026eacute;l\u0026eacute; et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cb\u003eNeed for Location-Specific Studies\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThe need for a decentralized research approach arises from the heterogeneity of agricultural systems in Nigeria based on geographical and seasonal factors. Results from research carried out in one agro-ecological zone (for example, the Sudan Savanna zone) cannot be applied to another zone (for example, the Rainforest zone) because of differences in the type of crop residues, climate, and agricultural systems. Future research must be location-specific and aim to solve the valorization of the most abundant local waste streams using local technologies.\u003c/p\u003e \u003cp\u003eFor example, in the northern cereal belt regions, research can aim to improve urea ammoniation and storage technology for sorghum and millet stover. In the southern root crop regions, research can aim to improve ensiling and detoxification technology for cassava peels and yam waste (Oguntade et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). This location specificity should also be applied to breeding and agronomic research aimed at developing dual-purpose crop varieties that can produce high-quality grain and more digestible residue biomass.\u003c/p\u003e \u003cp\u003eFinally, it is important that research involving farmers, processors, and feed millers is participatory from the very start. This will ensure that the technologies and strategies developed are feasible, acceptable, and economically viable, thus ensuring that the innovation gap between scientific research and on-farm implementation is closed (Adejoro et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). By ensuring that these research areas are given the utmost priority, the scientific community can provide the necessary evidence to ensure that agricultural by-product valorization is fully integrated into the foundation of a sustainable Nigerian ruminant sector.\u003c/p\u003e"},{"header":"10.0 CONCLUSION AND RECOMMENDATIONS","content":"\u003cp\u003e \u003cb\u003eSynthesis of Key Findings\u003c/b\u003e \u003c/p\u003e \u003cp\u003eSystematic valorization turns the 148\u0026nbsp;million tons/year agricultural waste burden in Nigeria into a sustainable ruminant feed resource, securing 15\u0026ndash;34% digestibility improvements, 20\u0026ndash;41% performance enhancements, and CB ratios 2.5\u0026ndash;5.2 in 28 trials (Adeyemo et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; Oludipe et al., 2024). Urea (4\u0026ndash;5%), fungal, and ensiling processes are most beneficial for rice straw, maize stover, cassava peels, reducing feed costs by 65\u0026ndash;84% while reducing CH4 emissions by 14\u0026ndash;31% and redirecting 65\u0026ndash;85% of residues away from pollution (Oguntade et al., 2025).\u003c/p\u003e \u003cp\u003eApproaches include matching waste to geographic location\u0026mdash;urea straw in the north, cassava silage in the south\u0026mdash;resulting in 23\u0026ndash;38% LCA footprint reductions and ₦620-920B bioeconomy economic value (FAO, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eChallenges remain but can be overcome: processing through local choppers/ensilers, preservation through inoculant silage, detoxification strategies (7-day fermentation), and socio-economic issues through cooperatives/subsidies as in LPRES biogas success (Babatunde et al., 2025). Circular economy integration enables the achievement of SDG 2/12/13 via feed-secure 24M ruminants, 35% emission cuts, 2.8M \u003cb\u003ejobs (UN Nigeria SDG Report, 2025).\u003c/b\u003e\u003c/p\u003e \u003cp\u003e \u003cb\u003ePolicy Recommendations\u003c/b\u003e \u003c/p\u003e \u003cp\u003eEstablish ₦150B National Agro-Waste Valorization Fund (2026\u0026ndash;2030) subsidizing choppers (75%), urea (50%), silos (100% first 1M units) through CBN Anchor Borrowers, targeting 40% smallholder coverage by 2028 (Financial Nigeria, 2025). Mandate 25% residue-to-feed in National Livestock Policy, enforcing burning bans through GIS monitoring/drones (₦12B initial) with ₦100K penalties tiered to farm size (Guardian Nigeria, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Assign 5,000 extension workers trained in 3-protocol methods (urea/fungal/ensiling), covering 2M farmers via digital platforms by 2027 (Sotande et al., 2024).\u003c/p\u003e \u003cp\u003e \u003cb\u003eTechnical Recommendations\u003c/b\u003e \u003c/p\u003e \u003cp\u003eEmphasize multi-stage processing such as chop-grind\u0026thinsp;+\u0026thinsp;urea (north cereals), fungal incubation (straws), inoculant ensiling (peels/haulms) achieving 85\u0026ndash;94% detoxification, 18\u0026ndash;28 months storage (Mustapha et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Establish 5 zonal hubs/zone with 50-ton/day capacity, solar-powered, aggregating through farmer cooperatives at ₦8/km haulage (Aruya et al., 2024). Standardize batch-testing (aflatoxin\u0026thinsp;\u0026lt;\u0026thinsp;20 ppb, HCN\u0026thinsp;\u0026lt;\u0026thinsp;10 mg/kg) through 50 mobile labs, certifying \"Safe Circular Feed\" for ₦5/kg premium (Ajayi et al., 2016).\u003c/p\u003e \u003cp\u003e \u003cb\u003eResearch Priorities\u003c/b\u003e \u003c/p\u003e \u003cp\u003eConduct meta-analysis of 50\u0026thinsp;+\u0026thinsp;trials for region-specific formulations (2026), LCA expansion to 10 commodities capturing manure/soil C (2027), and breed trials (Bunaji vs WAD) on waste diets (2028) (PMC Nigeria Livestock LCA, 2024). Innovate low-cost inoculants (local Lactobacillus, ₦2/kg vs ₦18 imported) and fungal strains tolerant 40\u0026deg;C/80% RH (LAUTECH Nanotechnology Group, 2025). Model scalability: 50M tons/year diverted = ₦1.2T savings, 20% NDC achievement (Oluwafemi Bakare/Ecoflow, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis review affirms that the systematic valorization of Nigeria's abundant agricultural by-products presents a viable and critical pathway toward sustainable ruminant production. The enormous volumes of generated crop residues represent an underutilized resource that can significantly mitigate perennial feed shortages, which constrain the livestock sector. Evidence synthesized indicates that through appropriate physical, chemical, and biological processing, these low-quality fibrous materials can be transformed into valuable feed supplements that support satisfactory animal growth, milk production, and reproductive performance.\u003c/p\u003e"},{"header":"Recommendations","content":"\u003cp\u003eTo transition from potential to widespread practice, the following targeted actions are recommended:\u003c/p\u003e \u003cp\u003e \u003cb\u003eFor Policymakers and Government Agencies\u003c/b\u003e:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eDevelop and implement a \u003cb\u003eNational Agricultural By-product Valorization Policy\u003c/b\u003e that provides a clear framework for waste collection, processing standards, and market development. This should be integrated into existing agricultural and environmental policies.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eIncentivize adoption\u003c/b\u003e through subsidies for small-scale processing equipment, tax breaks for feed mills incorporating treated residues, and grants for community-based ensiling or pelleting centers.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eStrengthen extension services\u003c/b\u003e to prioritize training on simple, safe valorization techniques and the economic benefits of using agricultural wastes, targeting farmer cooperatives and women\u0026rsquo;s groups.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e\n\u003ch3\u003eFor the Research Community and Academia:\u003c/h3\u003e\n\u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eFocus on \u003cb\u003eapplied, location-specific research\u003c/b\u003e to optimize low-cost processing technologies suitable for Nigeria\u0026rsquo;s major agro-ecological zones and predominant waste streams.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eEstablish a \u003cb\u003ecentralized, open-access database\u003c/b\u003e on the nutritional and anti-nutritional composition of Nigerian agricultural by-products to guide precise feed formulation.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eConduct longitudinal studies on the \u003cb\u003elong-term effects\u003c/b\u003e of processed by-product inclusion on animal health, product quality, and overall farm system sustainability.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e\n\u003ch3\u003eFor On-Farm and Industry Stakeholders:\u003c/h3\u003e\n\u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003ePromote the establishment of \u003cb\u003ecollaborative supply chains\u003c/b\u003e between crop processors and livestock farmers to ensure consistent supply and improve the economics of by-product collection and aggregation.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eAdopt and scale proven technologies\u003c/b\u003e, starting with simple methods like chopping and urea treatment, while investing in capacity building for safer and more advanced techniques like ensiling.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eFoster \u003cb\u003epublic-private partnerships\u003c/b\u003e to develop and distribute affordable feed products based on valorized by-products, incorporating quality control and safety protocols to build consumer and farmer trust.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e \u003cp\u003eThe valorization of Nigeria\u0026rsquo;s abundant agricultural by-products is not only an option but a necessity if a sustainable and resilient ruminant subsector is to be realized. Through the transformation of these by-products into valuable feed resources, Nigeria can overcome its feed insecurity while at the same time improving the livelihood of farmers. This can only be achieved through a multi-stakeholder approach.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMustapha, A.I., et al. (2024). \u003cem\u003eCassava peel silage economics in dairy cows\u003c/em\u003e. Journal of Animal Physiology, 98(6), 1456-1468.\u003c/li\u003e\n\u003cli\u003eAdeyemo, A. O., Olajide, O. S., \u0026amp; Suleiman, R. (2025). Utilization of agro-industrial by-products in ruminant nutrition: a sustainable approach to livestock farming. \u003cem\u003eSustainable Agricultural Reviews\u003c/em\u003e, 39, 45-64. https://doi.org/10.1016/j.sar.2025.04.007\u003c/li\u003e\n\u003cli\u003eNational Bureau of Statistics. 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(2025c). \u003cem\u003eCassava detoxification\u003c/em\u003e. https://www.fao.org/nigeria/publications/en/\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Valorization, Agricultural waste, Sustainability","lastPublishedDoi":"10.21203/rs.3.rs-8912667/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8912667/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAgricultural by-products and residues in Nigeria are a huge untapped resource that has the potential to improve sustainable ruminant production and reduce environmental pollution. This review aims to compile the latest developments in the utilization of different agricultural by-products such as maize husks, rice straw, cassava peels, groundnut husks, and sugarcane bagasse, based on their proximate composition, nutritional value, and potential use as feed supplements. The review discusses the valorization of these agricultural by-products as a sustainable approach for improving ruminant production in Nigeria. The review also discusses the recent biotechnological and nanotechnological approaches for upgrading agro-waste into value-added products for improving feed efficiency, animal health, and production sustainability. We synthesize the existing literature to compile the major by-products available in Nigeria and processing by-products account for their nutritional composition, availability, and disposal. The paper critically reviews different valorization approaches, such as physical, chemical, and biological processes to improve the nutritional value and palatability of these fibrous materials. In addition, we review the effects of supplementing these processed and unprocessed by-products to ruminants on feed intake, digestibility, growth, and milk production. Challenges such as infrastructural deficiencies, policy, and research investment that limit effective valorization in Nigeria are also reviewed. The review concludes that the valorization of agricultural by-products is a viable, sustainable, and economically sound approach to address feed insecurity, environmental waste, and the sustainability of the ruminant production system in Nigeria. This synthesis offers a contemporary knowledge base to guide researchers, policymakers, and stakeholders in optimizing agricultural by-product utilization for sustainable ruminant production in Nigeria.\u003c/p\u003e","manuscriptTitle":"A Comprehensive Review on the Valorization of Agricultural By-products for Sustainable Ruminant Production in Nigeria","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-24 06:51:36","doi":"10.21203/rs.3.rs-8912667/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"577dd8ad-e477-43de-b4f1-84590cb0a56b","owner":[],"postedDate":"February 24th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":63162385,"name":"Agricultural Economics \u0026 Policy"}],"tags":[],"updatedAt":"2026-02-24T06:51:36+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-24 06:51:36","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8912667","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8912667","identity":"rs-8912667","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}