Data_Sheet_1_Characteristics of rumen microbiota and Prevotella isolates found in high propionate and low methane-producing dairy cows.docx

Ruminal methane production is the main sink for metabolic hydrogen generated during rumen fermentation, and is a major contributor to greenhouse gas (GHG) emission. Individual ruminants exhibit varying methane production efficiency; therefore, understanding the microbial characteristics of low-methane-emitting animals could offer opportunities for mitigating enteric methane. Here, we investigated the association between rumen fermentation and rumen microbiota, focusing on methane production, and elucidated the physiological characteristics of bacteria found in low methane-producing cows. Thirteen Holstein cows in the late lactation stage were fed a corn silage-based total mixed ration (TMR), and feed digestion, milk production, rumen fermentation products, methane production, and rumen microbial composition were examined. Cows were classified into two ruminal fermentation groups using Principal component analysis: low and high methane-producing cows (36.9 vs. 43.2 L/DMI digested) with different ruminal short chain fatty acid ratio [(C2+C4)/C3] (3.54 vs. 5.03) and dry matter (DM) digestibility (67.7% vs. 65.3%). However, there were no significant differences in dry matter intake (DMI) and milk production between both groups. Additionally, there were differences in the abundance of OTUs assigned to uncultured Prevotella sp., Succinivibrio, and other 12 bacterial phylotypes between both groups. Specifically, a previously uncultured novel Prevotella sp. with lactate-producing phenotype was detected, with higher abundance in low methane-producing cows. These findings provide evidence that Prevotella may be associated with low methane and high propionate production. However, further research is required to improve the understanding of microbial relationships and metabolic processes involved in the mitigation of enteric methane.

瘤胃甲烷生成是瘤胃发酵过程中产生的代谢氢的主要归宿，同时也是温室气体（greenhouse gas, GHG）排放的主要来源。不同反刍动物个体的甲烷生成效率存在显著差异，因此解析低甲烷排放动物的微生物特征，可为缓解反刍动物肠道甲烷排放提供可行策略。本研究聚焦甲烷生成，探究了瘤胃发酵与瘤胃微生物组之间的关联，并阐明了低甲烷产奶牛体内细菌的生理特性。
本研究选取13头处于泌乳后期的荷斯坦奶牛（Holstein cows），饲喂以玉米青贮为基础的全混合日粮（total mixed ration, TMR），并对饲料消化率、产奶量、瘤胃发酵产物、甲烷生成量以及瘤胃微生物组成进行了系统测定。通过主成分分析（Principal component analysis, PCA）将奶牛划分为两组瘤胃发酵表型：低甲烷产奶牛与高甲烷产奶牛，二者的甲烷生成量分别为36.9与43.2 L/(kg 消化干物质)，瘤胃短链脂肪酸比例[(C2+C4)/C3]分别为3.54与5.03，干物质（dry matter, DM）消化率分别为67.7%与65.3%。但两组的干物质采食量（dry matter intake, DMI）与产奶量无显著差异。
此外，两组间隶属于未培养普雷沃氏菌属（Prevotella sp.）、琥珀酸弧菌属（Succinivibrio）以及其余12个细菌系统发育型的操作分类单元（operational taxonomic unit, OTU）丰度存在显著差异。具体而言，本研究检测到一株此前未被培养的具有产乳酸表型的新型普雷沃氏菌属菌株，其在低甲烷产奶牛体内的丰度显著更高。
本研究结果证实，普雷沃氏菌属可能与低甲烷生成以及高丙酸生成存在密切关联。不过仍需开展进一步研究，以深入解析参与缓解反刍动物肠道甲烷排放的微生物互作关系与代谢过程。