Cooperative Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Morioka, Iwate 020-8550, Japan.
Cooperative Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Morioka, Iwate 020-8550, Japan; United Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan.
J Dairy Sci. 2018 May;101(5):4424-4436. doi: 10.3168/jds.2017-13859. Epub 2018 Feb 22.
We investigated the effect of repeated subacute ruminal acidosis (SARA) challenges on the pH, fermentative function, and bacterial community in the rumen. Four rumen-cannulated Holstein bulls were fed a high-forage diet for 7 d (HF period) followed by a high-grain diet for 7 d (HG period). Four SARA challenges were carried out consecutively (first, second, third, and fourth challenges). The ruminal pH was measured continuously during the experiment, and rumen fluid samples during the first to fourth challenges were collected at 0800, 1400, and 2000 h on the last days of each feeding period for analysis; volatile fatty acid components, NH-N, and lactic acid concentrations were measured. Bacterial community structure was analyzed at 0800 h during the first and fourth challenges on the last days of each period. The 24-h mean ruminal pH was decreased during the transition from high-forage to high-grain diet and tended to differ between the HF and HG periods. During the HG period, ruminal pH <5.6 was maintained for a longer period in the first and second challenges (350 and 405 min/d, respectively) than in the third and fourth challenges (both 120 min/d). A marked increase in total volatile fatty acid and NH-N concentrations during the HG period was observed in the later challenges. In addition, lower and higher proportions of acetic and butyric acids, respectively, were observed during the HG period than during the HF period. A total of 37 core bacterial genera were found in all samples; however, the relative abundance of several genera differed significantly between the HF and HG periods (Prevotella, Ruminococcus, Eubacterium, and Oscillibacter) and between the first and fourth challenges (Eubacterium and unclassified Clostridiaceae). During the HG period, lower relative abundances of Prevotella, Eubacterium, and Oscillibacter and higher relative abundance of Ruminococcus were detected compared with during the HF period. The relative abundances of Eubacterium and unclassified Clostridiaceae were lower in the first challenge than in the fourth challenge. Bacterial diversity was greater during the HF period than during the HG period and was greater during the fourth challenge than during the first challenge. Interestingly, diversity indices during the HG period of the fourth challenge were higher than those during the HF period of the first challenge. These results suggested that rumen fermentation in Holstein cattle can adapt to repeated SARA challenges by minimizing the adverse changes in ruminal pH. Moreover, the composition and diversity of the ruminal bacterial community may be affected by ruminal pH and vice versa.
我们研究了重复亚急性瘤胃酸中毒（SARA）挑战对瘤胃 pH 值、发酵功能和细菌群落的影响。4 头荷斯坦奶牛在高纤维日粮（HF 期）下进行了 7 d 的适应期，然后进行 7 d 的高谷物日粮（HG 期）。连续进行了 4 次 SARA 挑战（第 1、2、3 和 4 次挑战）。在实验过程中连续测量瘤胃 pH 值，在每个喂养期的最后一天的 0800、1400 和 2000 h 收集第 1 到第 4 次挑战期间的瘤胃液样本进行分析；测量挥发性脂肪酸成分、NH-N 和乳酸浓度。在每个时期的最后一天的第 1 和第 4 次挑战期间的 0800 h 分析细菌群落结构。从高纤维日粮向高谷物日粮过渡期间，24 h 平均瘤胃 pH 值降低，HF 期和 HG 期之间有差异。在 HG 期，第 1 和第 2 次挑战（分别为 350 和 405 min/d）中瘤胃 pH 值低于 5.6 的时间比第 3 和第 4 次挑战（均为 120 min/d）更长。HG 期，总挥发性脂肪酸和 NH-N 浓度明显增加，在后期挑战中观察到更高的浓度。此外，HG 期乙酸和丁酸的比例分别低于 HF 期。在所有样本中发现了 37 个核心细菌属；然而，HF 期和 HG 期之间（普雷沃氏菌、瘤胃球菌、真杆菌和 Oscillibacter）以及第 1 次和第 4 次挑战之间（真杆菌和未分类梭菌科）几个属的相对丰度差异显著。与 HF 期相比，HG 期的 Prevotella、Eubacterium 和 Oscillibacter 相对丰度降低，Ruminococcus 的相对丰度增加。与第 4 次挑战相比，第 1 次挑战中真杆菌和未分类梭菌科的相对丰度较低。HF 期的细菌多样性大于 HG 期，第 4 次挑战的细菌多样性大于第 1 次挑战。有趣的是，HG 期第 4 次挑战的多样性指数高于 HF 期第 1 次挑战。这些结果表明，荷斯坦奶牛的瘤胃发酵可以通过最小化瘤胃 pH 值的不利变化来适应重复的 SARA 挑战。此外，瘤胃细菌群落的组成和多样性可能受到瘤胃 pH 值的影响，反之亦然。
