Effects of condensed tannin content in Alpine plants on rumen microorganisms of yak in vitro fermentation. 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 s1howed 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.

植物中的缩合单宁（condensed tannin）可有效降低反刍动物瘤胃发酵过程中的甲烷生成量。本研究选取青藏高原两种优势灌木——西藏沙棘（Hippophae tibetica，HTB）与杯腺柳（Salix Cupularis，SCP）作为目标植物，通过体外发酵试验，探究了二者所含缩合单宁对甲烷生成、发酵指标及微生物群落的影响。随叶片成熟进程，缩合单宁（CT）与粗蛋白（crude protein，CP）的含量显著降低，而酸性洗涤纤维（acid detergent fiber，ADF）与中性洗涤纤维（neutral detergent fiber，NDF）的含量则显著升高。高缩合单宁含量的叶片可抑制体外发酵的产气与甲烷（CH4）生成，降低干物质消化率（dry matter digestibility，DMD）、氮消化率（ND）、挥发性脂肪酸及乙酸含量，同时提升丙酸浓度。16S测序结果显示，植物来源的缩合单宁会降低瘤胃液的细菌多样性，且可显著降低古菌的多样性与丰度。主坐标分析表明，不同缩合单宁浓度组的瘤胃细菌与古菌群落各自形成独立聚类簇。甲烷球形菌属（Methanosphaera）的相对丰度在各组间存在显著差异。综上，植物中的缩合单宁可显著降低瘤胃甲烷排放，其作用机制可能为减少养分供应并降低古菌的丰度。