Metagenomic analysis reveals rumen microbiota alteration of the yak at different stages of growth

Abstract The Yak (Bos grunniens) is a unique ruminant species that is crucially important to agriculture in the Tibetan plateau. Variation of microorganism communities in the yak rumen is of great interest because of possible links to environmentally and economically important traits. In this study, we performed histological and microbial analyses of the yak rumen at 5 stages of growth: 1 day, 20 days, 60 days, 15 months, and 5 years of age. Tissue slices and metagenomics sequencing were used. The rumen index increased gradually from 1 day to 5 years of age. These were significant differences in rumen index between the 60d, 15m, and 5y group (p < 0.05). Compared with other time points, the thickness of muscularis along with length and width of rumen papillae at 60 d,15 m, and 5 years of age increased and differed (p < 0.05), respectively. At the phylum level, Bacteroidetes and Firmicutes were the phyla with the highest abundance in all the age groups. A total of 115,401 genes were annotated on the CAZy database. Glycoside Hydrolase (GH) had the highest relative abundance, followed by Glycosyl Transferase (GT), and Carbohydrate-binding Modules (CBM). There were significant variations for the microbial species and CAZys within the five groups. Taken together, the morphology and microbiota in the yak rumen changed at various stages of growth and likely played a significant role in the absorption of nutrients. This study provides new insights into the function of yak rumen microbiota and physiologic adaptations in plateau animals.