中文摘要：

本试验旨在研究高谷物日粮对山羊瘤胃上皮形态结构及单羧酸转运蛋白（monocarboxylate transporter,MCT）和钠钾ATP酶mRNA表达的影响。将10头装有永久性瘤胃瘘管的健康阉割公山羊随机分为饲喂全粗料日粮的对照组（Hay,0%谷物,n=5）和饲喂高谷物日粮的处理组（HG,65%谷物,n=5）,试验期为7周。试验开始后,于每周晨饲后的0、2、3、4、6、8和12h连续采集瘤胃液监测瘤胃pH值的变化,收集其中第0、3、6和12h的瘤胃液待测挥发性脂肪酸（volatile fatty acid,VFA）浓度。试验的第50天,屠宰采集瘤胃上皮用于形态学及基因定量分析。研究结果显示：与全粗料组山羊相比,高谷物组山羊瘤胃pH值、乙酸浓度及乙丙比都显著下降（P〈0.001）,而瘤胃丙酸浓度、丁酸浓度及其他VFA浓度都显著升高（P〈0.001）;高谷物日粮组的瘤胃乳头长度显著高于对照组（P=0.001）,瘤胃乳头宽度显著低于对照组（P〈0.001）,但是两组间的瘤胃乳头表面积并无显著差异;透射电镜结果显示,长期饲喂高谷物日粮导致瘤胃上皮细胞线粒体发生降解;实时定量PCR结果表明,与对照组相比,高谷物日粮显著升高了MCT1（P〈0.001）和钠钾ATP酶（P=0.001）的mRNA表达量,显著降低了MCT4的mRNA表达量（P=0.041）,但对MCT2的表达没有显著影响（P=0.305）;进一步分析这些基因的mRNA表达量与pH值和VFA浓度之间的相关性,结果显示,MCT1和钠钾ATP酶的mRNA表达量与瘤胃pH值和乙酸浓度呈显著负相关,与总VFA、丙酸、丁酸的含量呈显著正相关,而MCT4的mRNA表达量与pH值呈显著正相关,与总VFA、丙酸、丁酸的含量呈显著负相关。以上结果提示：高精料引起的瘤胃pH值下降和VFA的变化可能与瘤胃上皮MCT和钠钾ATP酶表达量的变化相关。研究结果对深入认识高谷物饲喂引发的瘤胃功能紊乱具有重要意义。

英文摘要：

The objective of this study was to investigate the effect of a high-grain（HG）diet on the ruminal epithelial structure and the transcript levels of genes encoding monocarboxylate transporters（MCTs）and a Na~＋/K~＋-ATPase in goats.Ten ruminally fistulated,castrated male goats were randomly assigned to either a hay diet（Hay,0% grain,n=5）or a HG diet（HG,65% grain,n=5）with continuous feeding for 7 weeks.Each week,at 0,2,3,4,6,8and 12 hafter morning feeding,rumen fluid was collected to monitor the changes in ruminal pH.The rumen fluid collected at 0,3,6,and 12 hafter morning feeding was used to determine the volatile fatty acid（VFA）concentration.The results showed that,compared with the control,the HG diet significantly reduced rumen pH,acetate concentration,and the acetate-propionate ratio（P0.001）,and significantly increased the concentrations of ruminal propionate,butyrate,and other VFAs（P0.001）.The HG diet significantly increased the length but decreased the width of rumen papillae.The surface of the rumen papillae did not differ significantly between the two groups.The HG diet caused substantial damage to ruminal epithelial cell mitochondria.Compared with the hay-fed group,the HG-fed group showed increased transcript levels of genes encoding MCT1（P0.001）and the Na~＋/K~＋-ATPase（P=0.001）,but decreased transcript levels of the gene encoding MCT4（P=0.041）.There was no significant difference in the transcript levels of MCT2 between the hay-fed and HG-fed groups（P=0.305）.Correlation analyses revealed that the transcript levels of the genes encoding MCT1 and Na~＋/K~＋-ATPase were negatively correlated with ruminal pH and acetate concentration,but positively correlated with total VFA,propionate,and butyrate concentrations.The MCT4 mRNA level was positively correlated with pH,but negatively correlated with total VFA,propionate,and butyrate concentrations.These results suggested that the changes in ruminal pH and VFA concentrations were associated with the changes in the e