Supplementation of Lycium barbarum residue improves the animal performance through the interaction of rumen microbiota and metabolome of Tan sheep

Background: Lycium barbarum residue (LBR), a by-product of Lycium barbarum processing, contains bioactive components which can be used as a plant-derived feed additive in animal husbandry. This study aimed to investigate the effects of LBR on the rumen fermentation parameters, ruminal microbes and metabolites, and growth performance of Tan sheep. Methods Sixteen Tan sheep were fed with a basal diet (CON; n  = 8) or a basal diet supplemented with 5% of LBR (LBR; n  = 8). The experiment lasted for 70 d, with 10 d adaptation period and 60 d treatment period. After slaughter, rumen fluid samples were collected and analyzed by 16S rRNA sequencing and untargeted metabolomics to elucidate the alternations of rumen microbial community and rumen metabolites. Results Data showed that LBR enhanced the average daily feed intake, average daily gain, and total volatile fatty acids ( P  < 0.01) but decreased ammonia-nitrogen concentration ( P  < 0.01) and rumen pH ( P  < 0.05). Additionally, LBR supplementation improved the relative abundances of Prevotella , Succiniclasticum , Ruminococcus , Coprococcus , Selenomonas , and Butyrivibrio ( P  < 0.05) and reduced the abundances of Oscillospira and Succinivibrio ( P  < 0.05). Metabolomics analysis revealed that the LBR altered the ruminal metabolome ( P  < 0.01) by increasing the abundances of ruminal metabolites involved in amino acids (e.g., L-proline, L-phenylalanine, L-lysine, and L-tyrosine), pyrimidine metabolism (e.g., uridine, uracil, and thymidine), and microbial protein synthesis (e.g., xanthine and hypoxanthine). Correlation analysis provided potential relationships between major microbiota and metabolites in the rumen. Conclusions In conclusion, supplementation of LBR affects rumen fermentation by altering the rumen microbiome and metabolome, thereby improving the growth performance of Tan sheep.