中文摘要：

本试验旨在研究饲粮补充异丁酸对断奶前后犊牛瘤胃及小肠发育相关基因表达的影响。选取平均体重（40.0±0.2）kg、发育正常、30日龄的中国荷斯坦公犊牛36头,随机分为4组,对照组饲喂基础饲粮,试验组分别在基础饲粮的基础上添加异丁酸3、6和9 g/d。分别于45、60（断奶）、90日龄每组屠宰3头并采集瘤胃及小肠黏膜组织样品,通过实时荧光定量PCR技术检测生长激素受体（GHR）、胰岛素受体（INSR）、3-羟基-3-甲基戊二酰辅酶A合成酶1（HMGCS1）和钠-葡萄糖共转运载体1（SGLT1）的mRNA表达量。结果表明：犊牛体重和GHR、INSR、HMGCS1 mRNA的表达量均随着犊牛日龄的增长而出现显著增长（P〈0.05）,而SGLT1mRNA的表达量在断奶前后随着日龄的增长先下降后增长,变化显著（P〈0.05）。45和60日龄时,犊牛体重在9 g/d异丁酸组显著高于对照组（P〈0.05）,但与6 g/d异丁酸组差异不显著（P〉0.05）。各日龄6和9 g/d异丁酸组瘤胃和小肠各部位GHR、INSR、HMGCS1 mRNA的表达量均高于对照组,且这2组之间差异不显著（P〉0.05）。添加异丁酸对45日龄和90日龄犊牛小肠各部位SGLT1 mRNA的表达量没有显著影响（P〉0.05）;60日龄6和9 g/d异丁酸组十二指肠SGLT1 mRNA表达量显著高于对照组和3 g/d异丁酸组（P〈0.05）,9 g/d异丁酸组空肠近端、空肠远端和回肠SGLT1 mRNA表达量显著高于对照组（P〈0.05）,但与6 g/d异丁酸组差异不显著（P〉0.05）。综合以上结果,饲粮中补充异丁酸能够促进犊牛生长和瘤胃及小肠黏膜的发育,本试验条件下其适宜添加量为6 g/d。

英文摘要：

This study was conducted to examine the effects of dietary isobutyrate supplementation on gene expressions related to rumen and small intestine development of pre-weaning and post-weaning calves.Thirty-six30-day-old Chinese Hostein dairy calves with similar body weight [（40.0 ± 0.2） kg] were divided into four groups at random.Isobutyrate was added to a basal diet with 0（control）,3,6 and 9 g/d,respectively.Three calves from each group were slaughtered at the age of 45,60（weaning age） and 90 days,samples of ruminal and small intestinal mucosa were collected to detect the mRNA expression levels of growth hormone receptor（GHR）,insulin receptor（INSR）,3-hydroxy-3-methylglutaryl-Co A synthase 1（HMGCS1） and sodium-glucose cotransporter 1（SGLT1） by the real-time quantitative PCR.The results showed that body weight and mRNA expression levels of G HR,INSR and HMG CS1 increased significantly with age（P〈0.05）,but SG LT1 mRNA expression level firstly decreased then increased before and after weaning,and the changes were significant（P〈0.05）.At the age of 45 and 60 days,body weight in 9 g/d isobutyrate group was significantly higher than that in control group（P〈0.05）,but was not significant different from that in 6 g/d isobutyrate group（P〈0.05）.At all days of age and all parts of rumen and small intestine,the mRNA expression levels of G HR,INSR and HMG CS1 in 6 and 9 g/d isobutyrate groups were higher than those in control group,and there were no significant differences between the two groups（P〈0.05）.At all parts of small intestine,the supplementation of isobutyrate did not affect the mRNA expression level of SG LT1 of 45-day-old and 90-day-old calves（P〈0.05）.At the age of 60 days,mRNA expression level of SG LT1 of duodenum in 6 and 9 g/d isobutyrate groups was significantly higher than that in control group and 3 g/d isobutyrate group,while mRNA expression level of SG LT1 of proximal jejunum,distal jejunum and ileum in 9 g/d isobutyrate group was significantly hig