effect of dietary supplement on rumen bacterial composition of yak.

This study aimed to explore shift in the rumen bacterial community of yak in response to dietary supplements during the cold season. In addition, the rumen fermentation patterns were also analyzed. Twenty-one female domestic yaks were randomly divided into three groups i.e., pure grazing (GG) group, grazing plus oats hay supplement (OG) group, and grazing plus concentrate supplement group (CG). Rumen contents were collected after 90 days to assess rumen fermentation parameters and bacterial community. The increased concentrations of ammonia nitrogen (P<0.001), total volatile fatty acids (TVFA) (P<0.001), and decreased rumen pH (P<0.001) were recorded in the CG group compared to other groups. The higher proportions of propionate and butyrate, while lower A/P ratio was recorded in the CG group. Shannon, Chao1, and ACE values were significantly lower in the OG group compared to GG and CG groups. Principal coordinate analysis indicated significant differences in rumen bacterial community among the three groups as confirmed by anosim analysis The Bacteroidetes, Proteobacteria, and Firmicutes were three dominant phyla in all groups. Only one phylum Tenericutes was significantly higher in the GG group compared to OG and CG groups. At the genus level, Prevotella was the most abundant in all groups. The genera Oscillospira (P=0.024), Ruminococcus (P=0.02), Clostridium (P=0.007), Corynebacterium (P=0.033), and Selenomonas (P=0.008) were affected by dietary supplements. The genera Oscillospira was highly abundant in GG and OG groups. The higher relative abundance of Ruminococcus and Clostridium was observed in the GG group, while Corynebacterium and Selenomonas were more abundant in the CG group. These findings will help in improving our understanding of rumen bacteria in yaks in response to changes in diet.