We investigated changes in rumen fermentation, the fluid bacterial community, and predicted functional pathway profiles in Holstein cows with and those without subacute ruminal acidosis (SARA) during the periparturient period. Eighteen multiparous Holstein cows categorized in the SARA (n = 9) or non-SARA (n = 9) groups depending on whether they developed SARA during the 2 wk after parturition. Reticulo-ruminal pH was measured continuously throughout the study. Rumen fluid and blood samples were collected 3 wk before and 2 and 6 wk after parturition, with an additional blood sample collected during the 0 and 4 wk after parturition. The 7-d mean reticulo-ruminal pH was significantly decreased in both groups postpartum compared with prepartum, with a greater and longer lasting change in the SARA group. The postpartum total volatile fatty acid concentration was significantly higher in the non-SARA than in SARA cows. Rumen bacterial richness and diversity were not affected by the periparturient period, but the non-SARA group had a significantly higher Simpson diversity index postpartum. No significant change was observed in the composition of major bacterial phyla or genera during the periparturient period. Among 17 operational taxonomic units (OTU) shared by all cows, the relative abundances of OTU36 (genus Pseudobutyrivibrio) in the SARA group and OTU4 (genus Prevotella) in the non-SARA group decreased significantly during the postpartum period compared with prepartum. In contrast, non-SARA cows had more diverse core bacterial OTU community including 23 additional OTU than those with SARA including 3 additional OTU (40 vs. 20 OTU). The OTU36 was significantly correlated with the proportion of iso-valeric acid (r = -0.353), and OTU4 was significantly correlated with the 7-d mean reticulo-ruminal pH (r = 0.432) and the proportions of acetic acid (r = 0.353) and propionic acid (r = -0.380). Prepartum, OTU2 (genus Prevotella) was the only OTU that differed significantly between the 2 groups. Changes in predicted functional pathway were primarily identified during the postpartum period, with 2 pathways upregulated at 3 wk prepartum and 24 upregulated and 34 downregulated at 6 wk postpartum in the SARA group. Our results suggest that SARA incidence is not strictly related to changes in rumen fermentation or fluid bacterial community structure, but the predicted functional pathways of bacterial communities showed late responses to a postpartum decrease in reticulo-ruminal pH. Therefore, postpartum predicted functional pathway analysis may indicate the underlying mechanisms causing SARA in Holstein cows during the periparturient period.

中文翻译：

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围产期荷斯坦奶牛有和没有亚急性瘤胃酸中毒的瘤胃发酵、细菌群落和预测功能通路的变化。

我们调查了围产期荷斯坦奶牛和没有亚急性瘤胃酸中毒 (SARA) 的荷斯坦奶牛瘤胃发酵、液体细菌群落和预测的功能途径谱的变化。18 头经产荷斯坦奶牛分为 SARA（n = 9）或非 SARA（n = 9）组，具体取决于它们是否在分娩后 2 周内发生 SARA。在整个研究过程中连续测量网状瘤胃 pH 值。产前 3 周和产后 2 周和 6 周采集瘤胃液和血样，产后 0 周和 4 周采集额外的血样。与产前相比，两组产后7天平均网状瘤胃pH均显着降低，SARA组变化更大且持续时间更长。非 SARA 奶牛的产后总挥发性脂肪酸浓度显着高于 SARA 奶牛。瘤胃细菌丰富度和多样性不受围产期影响，但非 SARA 组产后 Simpson 多样性指数显着升高。围产期主要细菌门或属的组成没有明显变化。在所有奶牛共有的 17 个操作分类单位（OTU）中，与产前相比，SARA 组中 OTU36（Pseudobutyrivibrio 属）和非 SARA 组中 OTU4（普氏菌属）的相对丰度显着降低。相比之下，非 SARA 奶牛的核心细菌 OTU 群落更多样化，包括 23 个额外的 OTU，而不是那些有 SARA 的奶牛，包括 3 个额外的 OTU（40 对 20 个 OTU）。OTU36与异戊酸比例显着相关（r = -0.353），OTU4与7天平均网状瘤胃pH（r = 0.432）和乙酸比例（r = 0.353）显着相关) 和丙酸 (r = -0.380)。产前，OTU2（普氏菌属）是唯一在两组之间有显着差异的 OTU。预测功能通路的变化主要在产后期间确定，在 SARA 组中，产前 3 周时有 2 条通路上调，产后 6 周时有 24 条上调和 34 条下调。我们的研究结果表明，SARA 的发生率与瘤胃发酵或流体细菌群落结构的变化并不严格相关，但细菌群落的预测功能途径显示出对产后网状瘤胃 pH 值降低的晚期反应。