Shaopeng Chen Changze Cui ^* Youpeng Qi ^* Baohong Mi ^* Meixian Zhang ^* Chenyue Jiao Chune Zhu ^* Xiangyan Wang Hu Jiang ^* Bingang Shi ^* Ma Xueming ^* Zhidong Zhao Xiaolan Zhang ^*

• Gansu Agricultural University, Lanzhou, China

The gut microbiota significantly influences the host's production performance and hea lth status, with different gastrointestinal tissues exhibiting functional diversity reflecte d in their microbial diversity. In this study, five adult male Tianzhu white yaks (4.5 ye ars old) were selected and fed under the same nutritional conditions. After the feeding experiment, the yaks were slaughtered, and chyme samples were collected from the r umen, abomasum, jejunum, and colon for 16S rRNA full-length sequencing and volati le fatty acid analysis. The results showed that the microbial composition and diversity of the rumen and abomasum were similar, with close genetic distances and functional projections. In contrast, the jejunum and colon had distinct microbial compositions an d diversity compared to the rumen and abomasum. At the phylum level, the dominant phyla in the rumen, abomasum, and colon were Firmicutes and Bacteroidetes, while i n the jejunum, the dominant phyla were Firmicutes and Proteobacteria. The abundanc e of Firmicutes differed significantly between the jejunum (87.24%) and the rumen (5 4.67%), abomasum (67.70%), and colon (65.77%). Similarly, Bacteroidetes showed si gnificant differences between the jejunum (2.21%) and the rumen (36.54%), abomasu m (23.81%), and colon (28.12%). At the genus level, Rikenellaceae_RC9_gut_group and Christensenellaceae_R-7_group were dominant in both the rumen and abomasum.In the jejunum, Romboutsia and Paeniclostridium were dominant, while Rikenellacea e_RC9_gut_group and UCG-005 were the dominant genera in the colon. At the specie s level, rumen_bacterium_g__Rikenellaceae_RC9_gut_group and rumen_bacterium_ g__Christensenellaceae_R-7_group were dominant in both the rumen and abomasum, while Clostridium_sp._g__Romboutsia and bacterium_g__Paeniclostridium were uni que to the jejunum. Ruminococcaceae_bacterium_g__UCG-005 and bacterium_g__Ri kenellaceae_RC9_gut_group were unique to the colon. KEGG functional prediction o f the microbiota indicated that the dominant functions in the rumen, abomasum, colon, and jejunum were amino acid metabolism, glycan biosynthesis and metabolism, carb ohydrate metabolism, and membrane transport, respectively, reflecting the digestive f unctions of these organs. Volatile fatty acid analysis showed that the concentrations of acetic acid, propionic acid, and butyric acid in the rumen were significantly higher th an those in the abomasum, jejunum, and colon (p < 0.05).