The reticulorumen, as the main fermentation site of ruminants, delivers energy in the form of short-chain fatty acids (SCFA) for both the animal as well as the ruminal wall. By absorbing these SCFA, the ruminal epithelium plays a major role in the maintenance of intraruminal and intraepithelial acid–base homoeostasis as well as the balance of osmolarity. It takes up SCFA via several pathways which additionally lead to either a reduction of protons in the ruminal lumen or the secretion of bicarbonate, ultimately buffering the ruminal content effectively. Nutrition of the epithelium itself is achieved by catabolism of the SCFA, especially butyrate. Catabolism of SCFA also helps to maintain a concentration gradient across the epithelium to ensure efficient SCFA uptake and stability of the epithelial osmolarity. Furthermore, the ruminal epithelium forms a tight barrier against pathogens, endotoxins or biogenic amines, which may emerge from ruminal microorganisms and feed. Under physiological conditions, it reduces toxin uptake to a minimum. Moreover, the epithelium seems to have the ability to degrade biogenic amines like histamine. Nonetheless, in high performance production animals like dairy cattle, the reticulorumen is confronted with large amounts of rapidly fermentable carbohydrates. This may push the epithelium to its limits, even though it possesses a great capacity to adapt to varying feeding conditions. If the epithelial limit is exceeded, increasing amounts of SCFA lead to an acidotic imbalance that provokes epithelial damage and thereby elevates the entrance of pathogens and other potentially harmful substances into the animal's body. Hence, the ruminal epithelium lays the foundation for the animal's health, and in order to ensure longevity and high performance of ruminant farm animals, it should never be overburdened.

中文翻译：

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瘤胃上皮：牛健康的检查点

网状瘤作为反刍动物的主要发酵场所，以短链脂肪酸 (SCFA) 的形式为动物和瘤胃壁提供能量。通过吸收这些 SCFA，瘤胃上皮在维持瘤胃内和上皮内酸碱平衡以及渗透压平衡中起主要作用。它占用了 SCFA通过几种途径额外导致瘤胃腔内质子减少或碳酸氢盐分泌，最终有效缓冲瘤胃内容物。上皮本身的营养是通过 SCFA，尤其是丁酸盐的分解代谢来实现的。SCFA 的分解代谢还有助于维持整个上皮细胞的浓度梯度，以确保 SCFA 的有效摄取和上皮渗透压的稳定性。此外，瘤胃上皮对病原体、内毒素或生物胺形成了紧密的屏障，这些病原体可能来自瘤胃微生物和饲料。在生理条件下，它将毒素吸收降至最低。此外，上皮似乎具有降解生物胺如组胺的能力。尽管如此，在奶牛等高性能生产动物中，网状细胞面临大量可快速发酵的碳水化合物。这可能会将上皮细胞推向极限，即使它具有适应不同喂养条件的强大能力。如果超过上皮限制，SCFA 量的增加会导致酸中毒失衡，从而引起上皮损伤，从而增加病原体和其他潜在有害物质进入动物体内的速度。因此，瘤胃上皮细胞为动物的健康奠定了基础，为了确保反刍家畜的长寿和高性能，绝不能过度负担。如果超过上皮限制，SCFA 量的增加会导致酸中毒失衡，从而引起上皮损伤，从而增加病原体和其他潜在有害物质进入动物体内的速度。因此，瘤胃上皮细胞为动物的健康奠定了基础，为了确保反刍家畜的长寿和高性能，绝不能过度负担。如果超过上皮限制，SCFA 量的增加会导致酸中毒失衡，从而引起上皮损伤，从而增加病原体和其他潜在有害物质进入动物体内的速度。因此，瘤胃上皮细胞为动物的健康奠定了基础，为了确保反刍家畜的长寿和高性能，绝不能过度负担。