The Department of Animal Science, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
J Dairy Sci. 2012 Jul;95(7):3977-86. doi: 10.3168/jds.2011-5089.
Ruminal wall metabolism was studied in nonlactating heifers by altering the carbohydrate (CHO) digestion site between rumen and intestine. The CHO digestion site was estimated from in situ and total-tract digestibility of control (CONT) diets and diets supplemented with corn (CRN), barley (BARL), or soy hulls (SOYH). Ruminal epithelial metabolism regulating gene expression, morphology, and nutrient delivery was assessed from a combination of rumen volatile fatty acid (VFA) concentration, biopsies for papilla morphology, and expression of putative metabolic regulatory genes encoding enzymes that facilitate VFA utilization. Digestible dry matter and CHO intake were 25 and 45% higher, respectively, in the supplemented diets than in CONT diets. Fiber supplementation increased the intestinal and decreased ruminal CHO digestion. Ruminal nonfiber CHO digestibility was 10% lower in CRN than with the high rumen-degradable supplement. The CONT heifers had lowest total ruminal VFA and highest acetate concentration relative to the other treatments. Total VFA concentration in BARL and CRN diets tended to be higher than in SOYH. The SOYH diet tended to reduce papilla dimension relative to CRN and BARL. The CRN diet tended to increase papilla surface area relative to BARL and SOYH. Gene expression of propionyl-coenzyme A carboxylase was higher in CRN and BARL than in SOYH diets, and tended to be higher in CRN than in BARL and SOYH diets. Lactate dehydrogenase and butyryl coenzyme A synthase gene transcripts tended to be higher in CONT than in the supplemented treatments. Thus, rumen epithelial expression of genes involved in VFA metabolism and ruminal wall-structure development are influenced by other regulatory mechanism that is not directly affected by local signals. The in situ methods used are a useful tool for differentiating ruminal from extraruminal nutrient supply.
通过改变瘤胃和肠道之间碳水化合物 (CHO) 的消化部位，研究了非泌乳奶牛的瘤胃壁代谢。CHO 消化部位是通过对照 (CONT) 饮食和补充玉米 (CRN)、大麦 (BARL) 或大豆皮 (SOYH) 的饮食的原位和全肠道消化率来估计的。通过瘤胃液挥发性脂肪酸 (VFA) 浓度、乳头形态活检和促进 VFA 利用的酶的代谢调节基因表达的测定，评估了瘤胃上皮代谢调节基因表达、形态和营养供应。与 CONT 饮食相比，补充饮食的可消化干物质和 CHO 摄入量分别提高了 25%和 45%。纤维补充增加了肠道和减少了瘤胃 CHO 消化。与高瘤胃可降解补充剂相比，CRN 中的非纤维 CHO 消化率低 10%。CONT 奶牛相对于其他处理的总瘤胃 VFA 浓度最低，乙酸浓度最高。BARL 和 CRN 饮食中的总 VFA 浓度趋于高于 SOYH。与 CRN 和 BARL 相比，SOYH 饮食趋于降低乳头尺寸。CRN 饮食趋于增加乳头表面积相对于 BARL 和 SOYH。CRN 和 BARL 饮食中的丙酰辅酶 A 羧化酶基因表达高于 SOYH 饮食，CRN 饮食中的基因表达高于 BARL 和 SOYH 饮食。乳酸脱氢酶和丁酰辅酶 A 合酶基因转录物趋于 CONT 高于补充处理。因此，参与 VFA 代谢和瘤胃壁结构发育的瘤胃上皮基因表达受到其他调节机制的影响，而不受局部信号的直接影响。所使用的原位方法是区分瘤胃内和瘤胃外营养素供应的有用工具。
