Man 张 ^* Yan Li ^* Yumin Li ^* Chenxu Cheng ^* Shatuo Chai ^* Yingkui Yang ^* Xun Wang ^* Shuxiang Wang ^*

• Qinghai University, Xining, China

There are few studies on the effect of rumen fluid transplantation on the fecal flora of yaks. Yak fecal flora is closely related to health. This study aimed to evaluate the effect of rumen fluid transplantation on growth performance and fecal flora indicators.Methods: Twenty 6-month healthy male yaks (weight: 57.20 ± 7.80 kg) were selected from grazing yaks in an alpine meadow pasture at an altitude of approximately 3400 m, They were then transferred to the farm and randomly divided into a control group (CON; n = 10) and a rumen fluid transplantation group (RT; n = 10). Separate single-pen rearing was performed in two pens using same rearing environment and feeding method and all yaks were earmarked for identification. In addition, ten yaks that had been adapted to stall fattening feed in one month were selected as the rumen fluid donor group to provide fresh rumen fluid. Ruminal fluid transplantation trials were conducted on 1 st ,3 rd , and 5 th . Overall, 1L of ruminal fluid was transplanted to each yak in the RT and CON group. The formal trial then began with both groups fed same diet. After this, yak feed intake was recorded daily, yaks were weighed on days 1, 30 and 60 of the formal trial, and yak fecal were collected directly from the ground on days 1, 4, 7, 14, 30 and 60 to compare the microbial composition of the fecal using 16s rRNA sequencing data. In conclusion, our findings suggest that rumen fluid transplantation improved the stability of the intestinal tract of yaks, improved the immunity of yaks; rumen fluid transplantation remodeled the structure of the intestinal flora, shorten the time of remodeling the intestinal flora of yaks during the transition period, and accelerating yak adaptation to digest housed rations, while reduced the DMI. The findings of this study provide new insights into yak microbial community transplantation and a reference for improving feed efficiency in the yak industry.