高精粗日粮对泌乳山羊肝脏蛋白质代谢与生长轴功能的影响
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摘 要：8只健康的泌乳中期山羊（Capra hircus），随机分为两组，日粮精粗比分别为4∶6（低精料组）和6∶4（高精料组），采用2×2拉丁方设计，2次重复取乳样，测定产奶量和乳中蛋白质含量.肝脏活体穿刺取样，二维凝胶电泳结合MAIDI-TOF-TOF质谱的方法分析肝脏内蛋白质代谢相关蛋白/酶表达的差异.结果：与低精料组相比，高精料组山羊日平均产奶量显著增高（P0.05）.肝脏蛋白组学结果表明，当精料比例提高时，肝脏参与蛋白质代谢的延长因子-Tu、谷氨酸脱氢酶、腺苷高半胱氨酸酶上调；而26S蛋白酶体调节亚基7和血清前白蛋白下调，即肝脏本身合成血清前白蛋白和小肽能力下降；同时氨基酸分解代谢和抗氧化应激作用加强.高精料饲喂泌乳期山羊，其肝脏中氨基酸消耗增多，同时小肽合成减少，竞争消耗了乳蛋白合成的原料，可能不利于乳蛋白的合成.。对高精料饲喂对内源性GH催乳效应和乳产量的影响及其机制初步探讨结果发现：与低精料组相比，高精料组泌奶山羊血液中GH、IGF-1含量均降低，乳中乳糖、乳产量下降，乳腺中IGF-1R mRNA表达下调。证明，长期饲喂高精料日粮，可导致内源性GH含量下降，IGF-1生成减少，乳产量下降。GH-IGF-1-IGF-1R轴活性抑制使其机制之一。
关键词：精粗比 氨基酸 肝脏 奶山羊 内源性生长激素
Effect of High Concentrate Diet on Hepatic Protein Metabolism and Function of Growth Axis in Lactation Goats
Ye Pingsheng Zhang Yuanshu
（Nanjing Agricultural University）
Abstract：Eight healthy mid- lactation goats were randomly divided into two groups， using 2×2 Latin square design with two replications. Dietary concentrate to forage ratios were 4∶6 and 6∶4. Milk samples were taken to measure milk yield and milk protein levels， and liver samples were collected by living donor liver biopsy. The differential expression proteins in the goat liver were extracted and separated by two- dimensional electrophoresis （2-DE） and MAIDI-TOF-TOF. The daily milk yield of high-concentrate group（6∶4 group）was significantly higher than that of the low-concentrate group （4∶6 group， P0.05）. The results of proteomics showed that in high-concentrate group（6∶4 group）， elongation factor Tu and glutamate dehydrogenase and adenosine homocysteine enzyme involved in protein metabolism had higher expression ， while 26S proteasome regulatory subunit 7 and serum prealbumin involved in protein metabolism had low expression. The ability to synthesize small peptide and lactalbumin was decreased in the liver， while the catabolism of amino acids and the role of oxidative stress were enhanced. The liver metabolism had an important influence to milk protein synthesis and metabolism. It was not conducive to synthesis milk protein for lactation goats fed high-concentrate diets because the consumption of amino acids increased and the synthesis of small peptide decreased. So he raw material for milk protein synthetic was consumed too much and its mechanism will be worth further study. The results of this study provided a clue to research the liver impact of milk protein synthesis. To evaluate the effects of endogenous GH-IGF-1 axis on lactating goats fed with high-concentrate diets. The main results showed that compared with the control group， the content of plasma GH and IGF-1 were decreased in the high-concentrate group， and the percentage of lactose and milk yield were also decreased. Meantime， the mRNA expression of IGF-1R in mammary gland was down-regulated in the high-concentrate group. Our results indicated that feeding with high-concentrate diets for 9 weeks would decrease the contents of endogenous GH and IGF-1， and eventually lead to the decreased milk yield. One of the mechanisms is that the activity of GH-IGF-1-IGF-1R axis is inhibited.
Key Words：Concentrate to forage ratio； Amino acid； liver； Dairy goats； Endogenous growth hormone
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