Age-dependent variations in rumen bacterial community of Mongolian cattle from weaning to adulthood

Rumen microbes play an important role in ruminant energy supply and animal performance. Previous studies showed that rumen microbiome of Mongolian cattle has more enzymes involved in the degradation of rough forage to provide sufficient energy to tolerate the harsh desert ecological conditions. However, little is known about the succession of rumen microbes in different developmental stages of post-weaning Mongolian cattle. Here, we examined the succession of the rumen microbial composition and structure of 15 post-weaning Mongolian cattle at three developmental stages i.e., 5 months (RM05), 18 months (RM18) and, 36 months (RM36). The diversity of rumen bacterial community was lower in RM05 group, which reached to stability with age. Bacteroidetes, and Firmicutes were the two dominant phyla among all age groups. Phylum Actinobacteria was significantly higher in RM05 group, phyla Proteobacteria and Epsilonbacteraeota were enriched in RM36 group and phyla Spirochaetes, and Tenericutes were highly abundant in RM18. Genera Prevotella_1, Bacteroides, and Bifidobacterium were abundant in RM05 group. Energy generating bacteria Rikenellaceae_RC9_gut_group showed high abundance in RM18 group and fiber degrading genus Alloprevotella was highly abundant in RM36 group. In particular, the genera uncultured_rumen_bacterium, Ruminococcaceae_UCG.010 and Christensenellaceae_R.7_group had the top interactions values in intra-group interaction network. This study provides some theoretical evidences about the structure and composition of rumen microbiota of Mongolian cattle at different developmental stages and emphasizing the importance of functional specific rumen bacteria in different age groups. Further studies are needed to determine their actual roles and interactions with the host.