高精料日粮饲喂诱导泌乳奶牛发生乳脂抑制的机制  

The Mechanism of High Concentrate Diet Fed Induced Milk Fat Depression in Lactating Dairy Cows(Bos taurus)

作　　者：曹洋[1] 李林[1] 谢正露[1] 艾阳[1] 张源淑[1] 

机构地区：[1]南京农业大学农业部动物生理生化重点开放实验室,南京210095

出　　处：《农业生物技术学报》2016年第11期1718-1725,共8页Journal of Agricultural Biotechnology

基　　金：国家重点基础研究发展计划(973)项目(No.2011CB100802)

摘　　要：高精料饲喂导致奶牛乳脂率降低的相关机制目前还不清楚。本研究通过探究高精料饲喂对肝脏内乳脂前体代谢的影响,揭示奶牛（Bos taurus）发生乳脂抑制的相关机制,将10头泌乳期（25±5）d荷斯坦奶牛随机分为2组,分别饲喂精粗比4∶6（对照组）和6∶4（实验组）日粮。饲喂20周后实施肝脏血管瘘手术,护理4周,进行如下实验：1）统计奶牛产奶量,每周测定乳成分;2）采集空腹进出肝脏血液,检测甘油三酯（triglyceride,TAG）和游离脂肪酸（free fatty acid,FFA）的含量;3）活体穿刺取肝脏组织,q RT-PCR检测肝脏中脂代谢相关基因的表达。结果表明,高精料饲喂6~18周可提高产奶量,18周后乳脂率显著降低（P〈0.05）。高精料组奶牛肝脏TAG和FFA的净输出含量显著（P〈0.05）或极显著降低（P〈0.01）;肝脏中参与脂肪酸合成代谢的固醇调节元件结合蛋白-1c基因（sterol regulating element binding protein-1 c,SREBP-1c）、乙酰辅酶A羧化酶基因（acetyl-coa carboxylase,ACC）和脂肪酸合成酶基因（fatty acid synthetase,FAS）表达显著（P〈0.05）或极显著（P〈0.01）下调;参与脂肪酸分解代谢的过氧化物酶体增殖物激活受体α基因（peroxisome proliferators-activated receptorα,PPARα）和肉毒碱棕榈酰转移酶-1基因（carnitine palmitoyl transterase-1,CPT-1）表达显著上调（P〈0.05）。高精料饲喂导致奶牛肝脏脂肪酸合成代谢减弱而分解代谢增强,肝脏内乳脂前体物发生重分配,乳脂前体物输出减少,影响了乳脂合成。本研究揭示了高精料饲喂导致奶牛乳脂率降低的机制,为改善奶牛乳脂率提供了理论基础。The mechanism of high concentrate diet which induces milk fat depression in lactating dairy cows （Bos taurus） has not been well explained. The purpose of this study is to investigate the changes of metabolism of milk fat precursors in liver by high concentrate diet fed, and to reveal the mechanism of milk fat depression （MFD） in lactating dairy cows. Ten Holstein cows （25 ＋ 5 days in milk） were divided into two groups and assigned to 2 dietary treatments： Control group （forage-to-concentrate ratio： 4：6） or a high concentrate group （forage-to-concentrate ratio： 6：4）. The liver vascular cannula was performed after 20 weeks feeding followed by convalescence for 4 weeks. The following experiments were carried out： 1） Milk production was recorded, and milk fat content was tested once a week; 2） Fasting blood from portal and hepatic vein was collected to test the concentration of triglyceride （TAG） and flee fatty acid （FFA）; 3） Live biopsy samples were collected to detect mRNA expression of fatty acid metabolism related genes. Results showed that milk yield of high concentrate group was increased during 6-18 week, while milk fat content was significantly decreased after 18 weeks （P〈0.05） compared with control group. Net content outputs of TAG and FFA in high concentrate group were significantly （P〈 0.05） or extremely significantly （P〈0.01） decreased compared with control group. The mRNA expression of sterol regulatingelement bindingprotein-lc （SREBP-lc）, acetyl-coacarboxylase （ACC）, fattyacidsynthetase （FAS） in liver of high concentrate group were significantly （P 〈 0.05） or extremely significantly （P〈 0.01） decreased, while the mRNA expressions of peroxisome proliferators-activated receptor a （PPARo~） and camitinepalmitoyl transterase-1 （CPT-1） were significantly increased （P〈0.05） compared with control group. High concentrate diets decreased fatty acid synthesis but enhanced fatty acid catabolism, which led to the

关 键 词：高精料日粮 泌乳奶牛 肝脏 脂代谢 乳脂抑制 

分 类 号：S852.2[农业科学—基础兽医学]