Institute of Veterinary Physiology, University of Leipzig, Leipzig, Germany.
Unit of Physiology, Pathophysiology and Experimental Endocrinology, Department of Biomedical Sciences, University of Veterinary Medicine Vienna, Vienna, Austria.
J Anim Physiol Anim Nutr (Berl). 2023 Jan;107(1):53-61. doi: 10.1111/jpn.13697. Epub 2022 Mar 2.
An optimal fermentation process in the forestomach is pivotal for the wellbeing and performance of ruminants. Complex carbohydrates are broken down into short-chain fatty acids (SCFA) which form the major energy source for the animal. A strong interrelationship of this process with intraruminal pH and redox potential (Eh) exists. These parameters can be measured with intraruminal sensors, but the interpretation of the measurements, especially of Eh, and their meaning for intraruminal homeostasis is not completely clear. In this study, factors influencing intraruminal Eh were elucidated. We hypothesised that intraruminal Eh is influenced by the fermentation process as such, but not by its end products SCFA. We measured Eh and pH in ruminal fluid from fasting cannulated sheep after the addition of 0.06 m Na-acetate, -propionate, -butyrate or glucose in vitro. Furthermore, we assessed the interrelation of pH and Eh. Basal Eh and pH values were -120 ± 41 mV and 7.0 ± 0.3, respectively, in native ruminal fluid in vitro. While the addition of SCFA did not induce any changes, glucose addition caused a significant decrease in both pH and Eh compared to the values before the addition (paired Student's t-test, p < 0.05). We attribute the decrease in Eh to an increased production of H in the process of generating SCFA, predominantly acetate. By titrating both native and particle-free ruminal fluid to more acidic and basic pH values (4.5-8.5), we found a non-linear inverse correlation of pH and Eh, counteracting the H -driven decrease of Eh during fermentation. Thus, the intraruminal Eh is influenced by pH and H output during SCFA formation. The opposed character of these factors stabilises the intraruminal homeostasis which might help maintain symbiotic microbiota in the rumen. Understanding, monitoring, and supporting this system will be an essential part of modern cattle production.
瘤胃中的最佳发酵过程对反刍动物的健康和性能至关重要。复杂的碳水化合物分解为短链脂肪酸 (SCFA)，这些脂肪酸构成动物的主要能量来源。这个过程与瘤胃内 pH 值和氧化还原电位 (Eh) 之间存在着强烈的相互关系。这些参数可以通过瘤胃内传感器进行测量，但对这些测量值的解释，尤其是 Eh 的解释，以及它们对瘤胃内稳态的意义尚不完全清楚。在这项研究中，我们阐明了影响瘤胃内 Eh 的因素。我们假设，瘤胃内 Eh 受到发酵过程的影响，但不受其终产物 SCFA 的影响。我们在体外向空腹绵羊的瘤胃液中添加 0.06m 的 Na-乙酸盐、-丙酸盐、-丁酸盐或葡萄糖后，测量了 Eh 和 pH 值。此外，我们评估了 pH 值和 Eh 值之间的相互关系。在体外，天然瘤胃液的基础 Eh 和 pH 值分别为-120±41mV 和 7.0±0.3。虽然添加 SCFA 不会引起任何变化，但与添加前相比，添加葡萄糖会导致 pH 值和 Eh 值显著下降（配对学生 t 检验，p<0.05）。我们将 Eh 值的下降归因于在生成 SCFA（主要是乙酸盐）的过程中 H 的产生增加。通过将天然和无颗粒的瘤胃液滴定到更酸性和碱性的 pH 值（4.5-8.5），我们发现 pH 值和 Eh 值呈非线性反比关系，这抵消了发酵过程中 Eh 值因 H 驱动而下降的趋势。因此，瘤胃内 Eh 值受 SCFA 形成过程中 pH 值和 H 输出的影响。这些因素的相反性质稳定了瘤胃内的稳态，这可能有助于维持瘤胃中的共生微生物群。了解、监测和支持这个系统将是现代牛生产的一个重要组成部分。
