Subacute rumen acidosis (SARA) is a common problem in dairy cattle. High‐concentrate rations lead to an accumulation of short‐chain fatty acids (SCFA) in the rumen and a subsequent decrease in ruminal pH. As SARA impairs animal welfare and productivity, numerous in vivo studies are focusing on evaluation of prevention strategies. In vitro models can support this research and reduce animal numbers and experimental costs. We used different diets and buffer compositions to induce SARA in the rumen simulation technique (Rusitec) and investigated the recovery process. The experiment consisted of an equilibration period (7 days), a first control period, a SARA period and a second control period (5 days each). During the SARA period, SARA was induced by infusing SARA1 or SARA2 buffer with reduced bicarbonate (20 mmol/L and 25 mmol/L) and phosphate (both 10 mmol/L) contents compared to a modified McDougall's buffer (bicarbonate 97.9 mmol/L, phosphates 20 mmol/L). Additionally, we compared three feeding strategies, which differed in the concentrate‐to‐roughage ratio (30:70, 70:30, changing ratio: 30% concentrate in control periods and 70% concentrate in SARA period). During the SARA period, the pH decreased to a constant value below the SARA thresholds of pH 5.8 and 5.6, whereas lactate concentrations remained low. The total SCFA production rate declined 3 days after SARA induction, and the molar proportion of acetate decreased. The decrease in pH and SCFA production was more pronounced for SARA1 buffer. The high‐concentrate diet reduced the molar proportion of acetate and increased NH₃‐N concentrations. During the second control period, most parameters recovered. In conclusion, SARA conditions were successfully induced in the Rusitec. However, we observed a higher influence of buffer composition than of concentrate proportions on most biochemical parameters. Nearly all changes were reversible. This model can be applied to test acidosis prevention strategies prior to animal experiments.

中文翻译：

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在瘤胃模拟技术中诱导亚急性瘤胃酸中毒期间和之后发酵参数的变化。

亚急性瘤胃酸中毒 (SARA) 是奶牛的常见问题。高浓度日粮导致瘤胃中短链脂肪酸 (SCFA) 的积累和随后瘤胃 pH 值的降低。由于 SARA 损害动物福利和生产力，许多体内研究都集中在评估预防策略上。体外模型可以支持这项研究并减少动物数量和实验成本。我们使用不同的饮食和缓冲液成分在瘤胃模拟技术 (Rusitec) 中诱导 SARA 并研究恢复过程。实验由平衡期（7天）、第一控制期、SARA期和第二控制期（各5天）组成。在SARA期间，与改良的 McDougall 缓冲液（碳酸氢盐 97.9 mmol/L，磷酸盐 20 mmol/L）相比，SARA 是通过注入具有减少的碳酸氢盐（20 mmol/L 和 25 mmol/L）和磷酸盐（均为 10 mmol/L）含量的 SARA1 或 SARA2 缓冲液来诱导的。 L)。此外，我们比较了三种饲喂策略，它们在精粗比上有所不同（30:70、70:30，变化比例：对照期精料为 30%，SARA 期为 70%）。在 SARA 期间，pH 值下降到低于 SARA 阈值 5.8 和 5.6 的恒定值，而乳酸浓度仍然很低。SARA 诱导后 3 天，总 SCFA 产生率下降，乙酸盐的摩尔比例下降。对于 SARA1 缓冲液，pH 值和 SCFA 产量的降低更为明显。_3- N 浓度。在第二个控制期，大部分参数恢复。总之，在 Rusitec 中成功诱导了 SARA 条件。然而，我们观察到缓冲液成分比浓缩物比例对大多数生化参数的影响更大。几乎所有的变化都是可逆的。该模型可用于在动物实验之前测试酸中毒预防策略。