Comparative Analysis of Rumen Fermentation and Microbial Communities in Yaks of Different Ages

Background: This study investigates the differences in rumen fermentation parameters and microbial communities in yaks aged 3 (MarG), 4 (AprG) and 5 months (MayG). As crucial livestock on the Qinghai-Tibet Plateau, optimizing yak health and productivity relies on understanding their rumen microbial structure and fermentation efficiency. These findings provide insights into their adaptation to the plateau environment and support strategies for improving livestock management. Methods: The study analyzed rumen fermentation parameters (NH3-N, acetate, propionate, isobutyrate, butyrate, valerate) and microbial composition in three age groups of yak calves. Microbial richness and composition were assessed, with network and correlation analyses identifying key microbial phyla associated with fermentation. Functional predictions explored gene abundances related to transcription, viral infection, cancer types and the immune system across the groups. Result: NH3-N and acetate levels were significantly higher in the MarG group compared to AprG and MayG (p less than 0.05), while MayG showed elevated propionate, isobutyrate, butyrate and valerate levels (p less than 0.05). Microbial composition varied, with Firmicutes and Actinobacteriota dominating MarG, Christensenellaceae and Oscillospiraceae in AprG and Desulfobacterota in MayG. Network analysis identified Proteobacteria as central in MarG, Firmicutes in AprG and both in MayG, forming the most complex network. UCG-005 showed strong positive correlations with all fermentation parameters. Functional predictions indicated higher cell motility in MarG and more immune-related genes in MayG.