Exploration of the effects of altitude change on bacteria and fungi in the rumen of yak (Bos grunniens).

The yak (Bos grunniens) is a ruminant animal with strong regional adaptability. However, little is known about the adaptation of the rumen microbial community of yaks at different altitudes and the adaptation mechanism of the host and intestinal microorganisms to the habitat. We investigated the adaptability of the rumen microorganisms of yaks at high and low altitudes. We also compared and analyzed the abundance and diversity of core microorganisms and those that varied between different animals. The aim was to compare the rumen bacterial and fungal communities of grazing yak living at two elevations. Bacteroidetes, Firmicutes, Ascomycota, and Chytridiomycota were the dominant bacteria in the plateau and low-altitude regions. Significant differences between the dominant microorganisms in the rumen of yaks were evident in the two regions. The proportion of fiber-degrading bacteria was significantly different between yaks dwelling at high-altitude and low-altitude regions. The abundance of starch-degrading bacteria was not significantly different with altitude. Species clustering similarity analysis showed that the rumen microorganisms in the two areas were obviously isolated and clustered into branches. Functional prediction showed significant differences in rumen microbial methane metabolism, starch and sucrose metabolism, ion-coupled transporter and bacterial secretion system at different altitudes. Overall, the results of this study improved our understanding of the abundance and composition of microorganisms in the rumen of yak at different altitudes.