动物机体内的褪黑素具有广泛的生物学作用。适当提高动物机体褪黑素的含量具有重要的实践价值。通过日粮营养调控的手段来调节动物体内褪黑素的合成是一种具有重要实践价值的方法之一。研究表明，给绵羊腹腔注射褪黑素的前体物质5-羟基色氨酸可提高绵羊白天、夜间血液中的褪黑素含量，而腹腔注射色氨酸则无作用。在绵羊等反刍动物，色氨酸、5-羟基色氨酸等褪黑素前体物质经胃肠方式处理后能否提高动物肠道组织、血液中褪黑素的含量？对绵羊肠道组织中褪黑素合成的调节机制（如对褪黑素合成关键酶活力、表达）是什么？本项目以绵羊为试验动物模型，探究色氨酸、5-羟基色氨酸等褪黑素前体物质以胃肠方式处理后能否提高动物机体肠道组织、血液中褪黑素的含量，及对绵羊肠道组织中褪黑素合成关键限速酶活力、表达量的影响，丰富反刍动物的褪黑素相关生物学理论和研究，为通过日粮调控反刍动物机体褪黑素合成量的技术方法提供科学理论基础。

Melatonin has extensive biological effects in the animal. Appropriate increase of melatonin level in animal has an important practical value. For livestock production, regulating the synthesis of melatonin in animals through the diet nutrient is one of important practical methods. Early research showed that serum melatonin levels at daytime and nighttime in sheep was significantly elevated when 5-hydroxy-tryptophan(5-HTP) was injected intraperitoneally, but nor did intraperitoneal injections of tryptophan. In ruminants such as sheep, can melatonin precursors (tryptophan, 5-HTP) absorbed by intestinal tissue and then improve the melatonin level in the blood ? How tryptophan, 5-HTP to regulate melatonin synthesis in sheep intestinal tissue? Sheep were used as the animal model in this project. The effects of the precursors of melatonin (tryptophan and 5-HTP) will be studied on blood melatonin levels, and on enzyme activity, gene expression of melatonin synthesis of key enzymes administrated with diet feeding. The study of this project will rich melatonin biological theory and related research in ruminants, and provide scientific theoretical basis for regulation of melatonin level in the ruminants by supplementation with the precursors (such as tryptophan, 5-HTP) .