Supplementation of Lycium barbarum residue increases the growth rate of Tan sheep by enhancing their feed intake and regulating their rumen microbiome and metabolome

Lycium barbarum residue (LBR), a by-product of Lycium barbarum processing, is packed with bioactive components and can be potentially utilized as a feed additive in animal husbandry. However, the fundamental understanding of its effectiveness on livestock animals is still lacking, particularly in ruminants. To explore the effects of LBR on the growth performance, rumen fermentation parameters, ruminal microbes and metabolites of Tan sheep, sixteen fattening rams (aged 4 months) were fed a basal diet (CON; n=8) or a basal diet supplemented with 5% LBR (LBR; n=8). The experiment lasted for 70 days, with 10 d adaptation period and 60 d treatment period. The results showed that the LBR enhanced the average daily feed intake, average daily gain (P<0.05), and ruminal total volatile fatty acids (P<0.01) while decreasing ammonia-nitrogen concentration and rumen pH value (P<0.05). Additionally, the LBR improved the relative abundances of Prevotella, Succiniclasticum, Ruminococcus, Coprococcus, Selenomonas, and Butyrivibrio (P<0.05) and reduced the relative abundances of Oscillospira and Succinivibrio (P<0.05). 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). In conclusion, LBR had positive effects on the growth rate of Tan sheep as well as on rumen fermentation parameters, rumen microbiome and rumen metabolome.