Effect of energy diet on the expression of PC and PEPCK mRNA in the liver of periparturient cows

chinois. 本研究目的在于观测干奶期不同能量摄入对围产期健康奶牛肝糖异生关键酶――丙酮酸羧化酶(PC)和磷酸烯醇式丙酮酸羧激酶（PEPCK）基因表达的影响。将健康围产期奶牛30头随机分为3组，于产前第28天分别饲喂奶牛标准日粮（能量摄入100%组）、标准日粮增加20%日粮（能量摄入120%组）和标准日粮减少20%日粮（能量摄入80%组），产后各组奶牛均饲喂标准的产奶日粮，至产后第56天结束。使用定量PCR方法检测分别于-28 d、-14 d、+1 d、+14 d、+28 d、+56 d采集的奶牛肝脏活体样品中PC和PEPCK mRNA表达水平。试验结果显示，PC mRNA丰度在产前28 d～产后56 d，低能组奶牛最高；PEPCK mRNA丰度在产后1 d～14 d低能组奶牛降低，产前28 d～14 d和产后28 d～56 d低能组奶牛最高。说明干奶期低能饲喂奶牛，可以增强围产期奶牛的肝糖异生能力。

anglais. The objective of the present study was to investigate the effect of energy intake during the dry period on the expression of Pyruvate carboxylase (PC) and Phosphoenolpyrevate carboxykinase (PEPCK) mRNA in the liver of periparturient diary cows. Thirty healthy multiparous Holstein cows were randomly allocated into three groups and fed on 100% energy diet (standard diets), 120% energy diet and 80% energy diet，respectively, beginning at the 28th day before parturition. After calving, all the cows were offered the lactation ration ad libitum until the 56th day postpartum. Quantitative PCR analysis of RNA from liver biopsy samples obtained on days -28、-14、+1、+14、+28、and +56 relative to calving indicated that PC and PEPCK mRNA expression were responsive to diet. Abundance of PC mRNA was the highest in the 80% energy diet cows during experimental period. Liver PEPCK mRNA abundance increased after parturition in the low energy diet group of cows compared with the other groups of cows except a period of the first 14d postpartum. The results demonstrate that the low energy diet during the dry period could improve the liver glyconeogenesis in the periparturient diary cows.