高精粗日糧對泌乳山羊肝臟蛋白質代謝與生長軸功能的影響

葉平生 張源淑

摘 要：8只健康的泌乳中期山羊（Capra hircus），隨機分為兩組，日糧精粗比分別為4∶6（低精料組）和6∶4（高精料組），采用2×2拉丁方設計，2次重復取乳樣，測定產奶量和乳中蛋白質含量.肝臟活體穿刺取樣，二維凝膠電泳結合MAIDI-TOF-TOF質譜的方法分析肝臟內蛋白質代謝相關蛋白/酶表達的差異.結果：與低精料組相比，高精料組山羊日平均產奶量顯著增高（P<0.05），而乳中蛋白質含量無顯著差異（P>0.05）.肝臟蛋白組學結果表明，當精料比例提高時，肝臟參與蛋白質代謝的延長因子-Tu、谷氨酸脫氫酶、腺苷高半胱氨酸酶上調；而26S蛋白酶體調節亞基7和血清前白蛋白下調，即肝臟本身合成血清前白蛋白和小肽能力下降；同時氨基酸分解代謝和抗氧化應激作用加強.高精料飼喂泌乳期山羊，其肝臟中氨基酸消耗增多，同時小肽合成減少，競爭消耗了乳蛋白合成的原料，可能不利于乳蛋白的合成.。對高精料飼喂對內源性GH催乳效應和乳產量的影響及其機制初步探討結果發現：與低精料組相比，高精料組泌奶山羊血液中GH、IGF-1含量均降低，乳中乳糖、乳產量下降，乳腺中IGF-1R mRNA表達下調。證明，長期飼喂高精料日糧，可導致內源性GH含量下降，IGF-1生成減少，乳產量下降。GH-IGF-1-IGF-1R軸活性抑制使其機制之一。

關鍵詞：精粗比 氨基酸 肝臟 奶山羊 內源性生長激素

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， P<0.05）， but milk protein content was no significant difference between two groups （P>0.05）. 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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