Effects of dietary supplementation with Enterococcus faecalis JM263 on growth performance, antioxidant status, rumen microbiota and metabolism in yaks.

backgroundYaks are vital to the ecology and economy of the Qinghai-Xizang Plateau. The unique environmental conditions of this high-altitude region have shaped yaks, leading to significant differences in their evolution from other cattle species. From yak gut contents, we isolated Enterococcus faecalis JM263, a novel probiotic with strong fiber-degrading ability. To investigate the effects of E. faecalis JM263 on the growth performance, antioxidant capacity, rumen microbiome, and metabolites of captive yaks, we randomly allocated 32-day-old yak calves weighing 84.5 ± 3.1 kg into three distinct groups: the control group (CK) fed a basal diet, Experimental Group 1 (CYL) received a test diet supplemented with 1 mL of E. faecalis JM263 (7.0 × 10⁸ CFU/mL) in the basal diet, and Experimental Group 2 (CYH) received a test diet supplemented with 1 mL of E. faecalis JM263 (14.0 × 10⁸ CFU/mL) in the basal diet. The experimental period lasted 60 days.

resultsCompared with the CK group, the CYL group showed significantly higher final weight and average daily gain (ADG) (P < 0.05), while the CYH group exhibited no significant changes (P > 0.05). Total Antioxidant Capacity (T-AOC) in both CYL and CYH groups was significantly higher than that in the CK group (P < 0.05). while GSH-Px levels in the CYL group were significantly higher than both CK and CYH groups (P < 0.05). 16 S rRNA sequencing analysis revealed that supplementation with E. faecalis JM263 significantly altered rumen microbial communities in yaks. 16 S rRNA results indicated significantly increased relative abundances of Saccharofermentans, Succiniclasticum, Methanobrevibacter, NK4A214_group, and Christensenellaceae_R-7_group (P < 0.05), while relative abundances of Butyrivibrio and F082 significantly decreased (P < 0.05). Metabolomics analysis revealed significant upregulation (P < 0.05) of metabolites including, S(-)-Cathinone, Anisomycin, (+)-Muscarine cation, and Deoxyadenosine, in both CYL and CYH groups compared to the CK group, indicating enhanced microbial activity. The CYH group also exhibited significant upregulation of S(-)-Cathinone and (-)-Epinephrine (P < 0.05). Correlation analysis between rumen microorganisms and metabolites revealed that 2'-deoxyadenosine, phosphorylcholine, and choline cation were significantly positively correlated with bacterial taxa such as Saccharofermentans. In contrast, hypoxanthine was significantly negatively correlated with Succiniclasticum, Methanobrevibacter, Christensenellaceae_R-7_group, NK4A214_group, and Saccharofermentans.

conclusionSupplementation with E. faecalis JM263 not only improved the growth performance and antioxidant capacity of yaks, but also reshaped the rumen metabolic profile while maintaining microbial community stability, and promoted microbe-metabolite interactions, thereby jointly contributing to the regulation of rumen homeostasis.