不同能量摄入水平对围产期奶牛肝MTP mRNA丰度的影响

将年龄、胎次相同，年产奶量大于7000kg的围产期荷斯坦奶牛30头随机分为3组，每组10头，低能量组（Ⅰ组）按中国奶牛营养标准2000年版减少20％日粮（能量摄入80％），高能量组（Ⅱ组）则按此标准增加20％日粮（能量摄入120％），对照组（Ⅲ组）按标准日粮（能量摄入100％）饲喂，试验从产前28d到产后56d结束，分娩后各组均按标准配制相同的泌乳日粮。分别于产前28、14d及产后1、14、28、56d采取肝活体组织。应用内对照RT—PCR方法检测肝脏组织MTPmRNA丰度。结果显示，各组奶牛肝MTPmRNA丰度均呈现先升高后降低的趋势。产后均高于产前，且产后1～28d差异显著（P〈0．01或P〈0．05），而后回降，至56d趋于平稳（P〉0．05）；Ⅲ组肝MTP mRNA丰度在产后1d达到峰值，而Ⅰ组和Ⅱ组在产后14d达到最大值（P〈0．01）；Ⅱ组产后1～28d显著高于I组。产后14d显著高于Ⅲ组（P〈0．01）；Ⅲ组产后1d和28d显著高于Ⅰ组（P〈0．01或P〈0．05）。这些结果表明，围产期奶牛能量摄入水平对肝MTP mRNA丰度有显著影响。

Effects of different energy intakes on abundance of MTP mRNA in liver of periparturient dairy cows

The objective was to determine a correlation between energy intakes and abundance of MTP mRNA in liver of periparturient dairy cows by method of interior comparison RT-PCR. On day 28 before parturition,thirty health multiparous periparturient Hostein cows were allocated randomly into three groups, which were fed with 80% energy diet(China Dairy Cow Raise Standard 2000 Diet),100% energy diet and 120% energy diet, respectively. After parturition,all the cows were offered with the criteria diet. The result showed that the relative abundance of MTP mRNA in liver from all the treated cows tended to a gradual increasing during last two weeks gestation, reached a peak from 1 d to 14 d after parturition, and then fell after a raise. Abundance of MTP mRNA in liver of the cows fed with 120% energy diet was significantly higher than that of the cows fed with 80% energy diet during day 1 to 56 postpartum, and than that of the cows fed with 100% energy diet at day 14 postpartum(P<0.01). Abundance of MTP mRNA in liver of the cows fed with 100% energy diets was significantly higher than that of the cows fed with 80% energy diet at day 1 and 28 postpartum(P<0.01 or P<0.05).It was concluded that dietary energy density during dry milk could impact the abundance of MTP mRNA in liver of early lactation cows.