This study investigated changes in rumen protozoal and methanogenic communities, along with the correlations among microbial taxa and methane (CH4) production of six Belmont Red Composite beef steers fed tea seed saponins (TSS). Animals were fed in three consecutive feeding periods, a high-grain basal diet for 14 d (BD period) then a period of progressive addition of TSS to the basal diet up to 30 g/d for 20 d (TSS period), followed by the basal diet for 13 d without TSS (BDP post-control period). The study found that TSS supplementation decreased the amount of the protozoal genus Entodinium and increased Polyplastron and Eudiplodinium genera. During BDP period, the protozoa community of steers did not return to the protozoal profiles observed in BD period, with higher proportions of Metadinium and Eudiplodinium and lower Isotricha. The addition of TSS was found to change the structure of methanogen community at the sub-genus level by decreasing the abundance of methanogens in the SGMT clade and increasing the abundance of methanogens in the RO clade. The correlation analysis indicated that the abundance of SGMT clade methanogens were positively correlated with Isotricha, and Isotricha genus and SGMT clade methanogens were positively correlated with CH4 production. While RO clade were positively correlated with the proportion of Metadinium genus, which was negatively correlated with CH4 emission. These results suggest that different genera of rumen protozoa ciliates appear to be selectively inhibited by TSS, and the change in methanogen community at the subgenus level may be due to the mutualistic relationships between methanogens and rumen ciliates.

中文翻译：

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肉牛日粮中添加茶籽皂苷后瘤胃原生动物和产甲烷菌的群落结构和微生物联系。

本研究调查了饲喂茶籽皂苷 (TSS) 的 6 头贝尔蒙特红复合牛肉的瘤胃原生动物和产甲烷群落的变化，以及微生物类群和甲烷 (CH4) 产量之间的相关性。动物在三个连续的喂养期喂食，高谷物基础日粮 14 天（BD 期），然后在基础日粮中逐步添加 TSS 至 30 克/天，持续 20 天（TSS 期），然后是基础日粮 13 天无 TSS（BDP 后控制期）。研究发现，TSS 补充剂减少了原生动物 Entodinium 属的数量，并增加了 Polyplastron 和 Eudiplodinium 属。在BDP期间，阉牛的原生动物群落没有恢复到BD期间观察到的原生动物分布，Metadinium和Eudiplodinium的比例较高，而Isotricha的比例较低。发现添加 TSS 通过降低 SGMT 进化枝中产甲烷菌的丰度和增加 RO 进化枝中产甲烷菌的丰度来改变亚属水平的产甲烷菌群落结构。相关性分析表明，SGMT进化枝产甲烷菌丰度与等毛菌呈正相关，等毛菌属和SGMT进化枝产甲烷菌与CH4产量呈正相关。RO进化枝与Metadinium属的比例呈正相关，与CH4排放呈负相关。这些结果表明，不同属的瘤胃原生动物纤毛虫似乎受到TSS的选择性抑制，亚属水平的产甲烷菌群落变化可能是由于产甲烷菌和瘤胃纤毛虫之间的共生关系。