Clinic for Swine, University of Veterinary Medicine Vienna, A-1210 Vienna, Austria.
J Anim Sci. 2013 Sep;91(9):4256-66. doi: 10.2527/jas.2012-5570. Epub 2013 Jul 3.
Emerging evidence at the mRNA level indicates that feeding high-grain diets to ruminants leads to coordinated changes in the molecular response of the rumen epithelium. Yet, epithelial adaptation of the hindgut to increasing dietary grain levels has not been established in ruminants. Therefore, the objective of this study was to characterize alterations in mRNA expression associated with nutrient transport and electrochemical gradients in rumen and colon epithelium, and rumen morphology in growing goats fed different grain levels. Goats (n = 6) were fed diets with increasing levels of 0, 30, or 60% barley grain for 6 wk. Goats were euthanized 2 h after their last feeding, and digesta and tissue samples of the cranial part of the ventral rumen and proximal colon were collected. Goats fed the 60% grain diet exhibited a lower ruminal and colonic pH (P < 0.01) and a greater colonic total VFA concentration (P < 0.05) compared with those fed the 0 and 30% grain diets. As response to the decreased ruminal pH, goats fed the 60% grain diet had a greater (P < 0.05) keratinization and thicker stratum corneum of the rumen epithelium than goats fed the 0 and 30% grain diets. The 60% grain diet upregulated (P < 0.05) MCT1 expression by 45% and downregulated (P < 0.05) the expression of MCT4 and SGLT1 by 28 and 50%, respectively, in rumen epithelium compared with the 0 and 30% grain diets. Accordingly, goats fed the 60% grain diet had a greater (P < 0.05) expression of MCT1 and ATP1A1 in colon epithelium than goats fed the 0 and 30% grain diets. Regression analyses showed negative relationships (R(2) = 0.35 to 0.87, P < 0.05) of MCT1 and ATP1A1 expression in rumen and colon epithelium and thickening of ruminal stratum corneum to decreasing luminal pH values, suggesting greater mRNA expression at lower pH. In contrast, MCT4 expression in rumen epithelium positively correlated to luminal pH (R(2) = 0.95, P < 0.01). In conclusion, results of this model study indicated that with the greatest grain level rumen and colon molecular epithelial responses may have been related to counteract the consequences of luminal acidification on intracellular homeostasis in epithelial cells and concomitantly to increase systemic absorption of VFA.
越来越多的证据表明，在 mRNA 水平上，给反刍动物喂食高谷物日粮会导致瘤胃上皮的分子反应发生协调变化。然而，反刍动物后肠对日粮中谷物水平增加的上皮适应性尚未得到证实。因此，本研究的目的是描述与瘤胃和结肠上皮的营养物质转运和电化学梯度以及生长山羊瘤胃形态相关的 mRNA 表达变化，这些山羊分别喂食不同谷物水平的日粮。将 6 只山羊（n = 6）喂食含有 0、30 或 60%大麦谷物水平逐渐增加的日粮 6 周。山羊在最后一次喂食后 2 小时被安乐死，采集颅腹侧瘤胃和近端结肠的食糜和组织样本。与喂食 0 和 30%谷物日粮的山羊相比，喂食 60%谷物日粮的山羊的瘤胃和结肠 pH 值较低（P < 0.01），结肠总 VFA 浓度较高（P < 0.05）。为了应对瘤胃 pH 值降低，与喂食 0 和 30%谷物日粮的山羊相比，喂食 60%谷物日粮的山羊瘤胃上皮的角化和角质层变厚（P < 0.05）。与 0 和 30%谷物日粮相比，60%谷物日粮分别上调（P < 0.05）MCT1 表达 45%，下调（P < 0.05）MCT4 和 SGLT1 表达 28%和 50%。因此，与喂食 0 和 30%谷物日粮的山羊相比，喂食 60%谷物日粮的山羊结肠上皮的 MCT1 和 ATP1A1 表达（P < 0.05）更高。回归分析显示，瘤胃和结肠上皮 MCT1 和 ATP1A1 表达以及瘤胃角质层变厚与腔内腔 pH 值降低呈负相关（R² = 0.35 至 0.87，P < 0.05），提示在较低 pH 值时，mRNA 表达更高。相反，瘤胃上皮 MCT4 表达与腔内腔 pH 值呈正相关（R² = 0.95，P < 0.01）。总之，本模型研究结果表明，在最大谷物水平下，瘤胃和结肠的分子上皮反应可能与抵消腔内酸化对上皮细胞细胞内稳态的影响有关，同时增加 VFA 的全身吸收有关。
