Feedlot diets improve yak meat quality by altering rumen microbiota and metabolic pathways

Over the past two decades, the effects of feeding systems on ruminant meat quality have been widely recognized, yet the mechanisms linking diet, rumen microbiota, metabolites, and muscle composition remain insufficiently understood. This study compared feedlot feeding (FDL) and traditional grazing (GRZ) systems in yaks ( Bos grunniens ) to identify microbial and metabolic features associated with improved meat quality traits. Twelve yaks with similar initial body weight were evaluated for growth performance, carcass traits, longissimus dorsi (LD) muscle characteristics, rumen bacterial composition, and metabolomic profiles. Compared with GRZ yaks, FDL yaks showed greater average daily gain, carcass weight, net meat weight, eye muscle area, essential amino acid (EAA) content, and n-6:n-3 polyunsaturated fatty acid (PUFA) ratio by 63.5%, 37.3%, 8.3%, 21.8%, 37.3%, and 30.6%, respectively. FDL also improved meat tenderness while altering fatty acid balance. Firmicutes and Bacteroidota were the dominant bacterial phyla in both groups. At the genus level, Christensenellaceae_R-7 , Ruminococcus , and Lachnospiraceae_NK3A20 were more characteristic of FDL yaks, whereas Prevotellaceae_UCG-003 and Rikenellaceae_RC9 were more abundant in GRZ yaks. Correlation analysis showed that rumen bacterial taxa were associated with fat deposition, meat color, EAA content, and fiber degradation-related traits.Metabolomic analysis showed that lysoPC(24:1(15Z)), crocin, and related lipid metabolites were enriched in FDL yaks, whereas carotenoid and chlorophyll derivatives were greater in GRZ than FDL yaks. Kyoto encyclopedia of genes and genomes pathway (KEGG pathway) analysis indicated enrichment of lipid metabolism pathways in feedlot yaks. This study identifies microbial taxa and metabolites as potential targets for nutritional interventions, providing mechanistic insights and practical strategies to optimize yak feeding systems and improve the industrial and nutritional value of high-altitude yak meat.