Nutritional value of extracted soybean, full fat soya and maize gluten meal proteins in comparison to a fish meal based reference diet for fingerling tilapia (Oreochromis mossambicus)

A two-month investigation evaluated potential selected plant protein sources compared to fish meal protein in scientifically formulated diets for fingerling tilapia ( Oreochromis mossambicus ). Six nutritionally balanced diets: one reference (control) diet (fish-meal-based diet), three selected plant proteins (solvent extracted soybean, full fat soybean, and maize gluten) were substituted in the LT (Low Temperature dried) fish-meal-based control diet protein at 50% respectively, and the remaining diets were replaced with 75% inclusion of solvent extracted soybean and maize gluten meals. Results showed that SESB50, FFSB50 and MG50 fed tilapia did not appreciably differ in their growthperformance (final mean weights of 12.07, 10.75 and 9.18% respectively) with a final mean weight of 14.95g being significantly superior for the fish meal control (CO) group. Substitution of fish meal diet with solvent-extracted soybean and maize gluten at levels of 75% gave the poorest growth performance and Feed Efficiency (FE) (7.01g final weight, 51% FE). However, the MG50 diet also showed some inferior feed utilisation performance. However, tilapia fed on a full fat soybean diet (FFSB50) did not vary significantly from the control (CON) diet in terms of Apparent Net Protein Utilisation (ANPU) at 34.20 and 37.53% respectively. Whilst this preliminary study concluded that limitations on the use of the selected plant proteins in diets for tilapia are apparent, several approaches that could result in the future improvement of the nutritional value of soybean and maize gluten products for use in fish diets are also stated. Highlights A scientifically formulated reference diet using a Low Temperature dried (LT) fish meal produced superior growth performance for fingerling tilapia compared to selected oilseed (soybean) and grain (maize gluten) derived protein concentrates. Soybean and full fat soybean meals were effective in contributing to 50% inclusion in experimental diets, but 75% of soybean and maize gluten meal was not able to support similar growth of tilapia over eight weeks. Feed utilisation parameters such as Protein Efficiency Ratio (PER), Apparent Net Protein Utilisation (ANPU), Net Energy Utilisation (NEU) and Feed Efficiency (FE) gave supporting evidence and conclusions for optimal threshold inclusions of the test plant ingredients for tilapia.