Dietary energy densities regulated the rumen microflora and specific bacteria related to energy harvest of yaks

The yaks (Bos grunniens) are important livestock for the local nomadic pastoralists on the Qinghai-Tibet Plateau. Yaks are also considered as the unique cattle which can healthily live in the highland environment. Recent studies found that for adaption to the atrocious plateau environment, the rumen microflora of yaks had more efficient energy-harvesting abilities than that of the cattle living at low altitude. However, the study on nutritional factors such as dietary energy regulating the rumen microflora of yaks is still scarce. On the other hand, yaks always gain weight in the short warm season and have extreme body weight reduction during the long cold season because of the forage scarcity and low temperature (average temperature -10 ℃). The nutritional supplementing is an effective way to increase survival and facilitate body weight gain of yaks in the long cold season. Our previous study found that supplementing energy feeds was more efficient than supplementing protein feeds to improve growth performance of yaks in the cold season, However, the effects of dietary energy densities on the rumen microflora and the dominant bacteria related to energy harvest in the rumen ecosystem of yaks are still unclear. Therefore, this study was conducted to investigate the effects of dietary energy densities on the rumen microflora of yaks by using 16S rDNA sequencing and reveal the specific bacteria related to energy harvest by using association analysis between ruminal bacteria and serum energy metabolites. This study also provided useful experimental data for the nutritional supplementing technology of yaks in the cold season.