Subacute ruminal acidosis (SARA) is a common metabolic disorder of high yielding dairy cows, and it is associated with dysbiosis of the rumen and gut microbiome and host inflammation. This study evaluated the impact of two postbiotics from Saccharomyces cerevisiae fermentation products (SCFP) on rumen liquid associated microbiota of lactating dairy cows subjected to repeated grain-based SARA challenges. A total of 32 rumen cannulated cows were randomly assigned to 4 treatments from 4 weeks before until 12 weeks after parturition. Treatment groups included a Control diet or diets supplemented with postbiotics (SCFPa, 14 g/d Original XPC; SCFPb-1X, 19 g/d NutriTek; SCFPb-2X, 38 g/d NutriTek, Diamond V, Cedar Rapids, IA, USA). Grain-based SARA challenges were conducted during week 5 (SARA1) and week 8 (SARA2) after parturition by replacing 20% DM of the base total mixed ration (TMR) with pellets containing 50% ground barley and 50% ground wheat. Total DNA from rumen liquid samples was subjected to V3–V4 16S rRNA gene amplicon sequencing. Characteristics of rumen microbiota were compared among treatments and SARA stages. Both SARA challenges reduced the diversity and richness of rumen liquid microbiota, altered the overall composition (β-diversity), and its predicted functionality including carbohydrates and amino acids metabolic pathways. The SARA challenges also reduced the number of significant associations among different taxa, number of hub taxa and their composition in the microbial co-occurrence networks. Supplementation with SCFP postbiotics, in particular SCFPb-2X, enhanced the robustness of the rumen microbiota. The SCFP supplemented cows had less fluctuation in relative abundances of community members when exposed to SARA challenges. The SCFP supplementation promoted the populations of lactate utilizing and fibrolytic bacteria, including members of Ruminococcaceae and Lachnospiraceae, and also increased the numbers of hub taxa during non-SARA and SARA stages. Supplementation with SCFPb-2X prevented the fluctuations in the abundances of hub taxa that were positively correlated with the acetate concentration, and α- and β-diversity metrics in rumen liquid digesta. Induction of SARA challenges reduced microbiota richness and diversity and caused fluctuations in major bacterial phyla in rumen liquid microbiota in lactating dairy cows. Supplementation of SCFP postbiotics could attenuate adverse effects of SARA on rumen liquid microbiota.

中文翻译：

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来自酿酒酵母发酵的后生元可稳定泌乳奶牛基于谷物的亚急性瘤胃酸中毒 (SARA) 期间瘤胃液体食糜中的微生物群


亚急性瘤胃酸中毒（SARA）是高产奶牛常见的代谢性疾病，与瘤胃和肠道微生物菌群失调以及宿主炎症有关。本研究评估了来自酿酒酵母发酵产品 (SCFP) 的两种后生元对反复进行谷物 SARA 挑战的泌乳奶牛瘤胃液相关微生物群的影响。总共 32 头瘤胃插管奶牛从产前 4 周到产后 12 周被随机分配到 4 个治疗组。治疗组包括对照饮食或补充后生元的饮食（SCFPa，14 g/d Original XPC；SCFPb-1X，19 g/d NutriTek；SCFPb-2X，38 g/d NutriTek，Diamond V，锡达拉皮兹，爱荷华州，美国）。在产后第 5 周 (SARA1) 和第 8 周 (SARA2) 进行基于谷物的 SARA 挑战，将基础总混合日粮 (TMR) 的 20% DM 替换为含有 50% 磨碎大麦和 50% 磨碎小麦的颗粒。对来自瘤胃液体样品的总 DNA 进行 V3–V4 16S rRNA 基因扩增子测序。比较各处理和 SARA 阶段的瘤胃微生物群特征。这两项 SARA 挑战都降低了瘤胃液体微生物群的多样性和丰富度，改变了整体组成（β-多样性）及其预测的功能，包括碳水化合物和氨基酸代谢途径。 SARA 挑战还减少了不同类群之间的重要关联数量、中心类群的数量及其在微生物共现网络中的组成。补充 SCFP 后生元，特别是 SCFPb-2X，增强了瘤胃微生物群的稳健性。补充 SCFP 的奶牛在面临 SARA 挑战时，群落成员相对丰度的波动较小。 SCFP 补充剂促进了乳酸利用和纤维溶解细菌的数量，包括瘤胃球菌科和毛螺菌科的成员，并且还增加了非 SARA 和 SARA 阶段的中心分类单元的数量。补充 SCFPb-2X 可防止中心类群丰度的波动，这些波动与瘤胃液体食糜中的醋酸盐浓度以及 α 和 β 多样性指标呈正相关。 SARA 挑战的诱导降低了泌乳奶牛微生物群的丰富度和多样性，并导致瘤胃液体微生物群中主要细菌门的波动。补充 SCFP 后生元可以减轻 SARA 对瘤胃液体微生物群的不利影响。