16S sequencing during in vitro rumen fermentation of Yaks with different alpine plants. Dietary supplement

Condensed tannin in plants can effectively reduce methane production during rumen fermentation in ruminants. Two dominant shrubs of the Tibetan Plateau, Hippophae tibetica (HTB) and Salix Cupularis (SCP), were selected as target plants. In this study, the effects of condensed tannins in HTB and SCP on methane production, fermentation indices and microbial community were investigated during in vitro fermentation. The concentration of CT and CP decreased significantly, while the content of ADF and NDF increased significantly with the ripening of leaves. Leaves with high CT concentration inhibited gas production and CH4 in vitro, and decreased DMD, ND, volatile fatty acids, and acetic acid, while increased propionic acid concentration. The results of 16S sequencing showed that the condensed tannin content in plants decreased the bacterial diversity in rumen liquid, and the condensed tannin significantly reduced the diversity and abundance of archaea. Principal coordinate analysis showed that rumen bacterial and archaeal communities of different tannin concentration groups were separately clustered. The relative abundance of the archaeal genus Methanosphaera was significantly different among different groups. In conclusion, condensed tannins in plants can significantly reduce methane emissions in the rumen, possibly by reducing the nutrient supply and abundance of archaea.