中文摘要：

为研究正常情况下经产荷斯坦奶牛24h内血液中褪黑素浓度的变化情况,探索不同外源褪黑素处理方式对荷斯坦奶牛血液褪黑素浓度的影响,本研究采用颈静脉注射、颈部皮下注射、颈部皮下埋植和口腔灌服外源褪黑素等方式处理经产荷斯坦奶牛,观察血液中褪黑素浓度的变化情况并分析褪黑素在体内的分泌规律及代谢速率。结果显示,在24h内,经产荷斯坦奶牛血液中褪黑素浓度变化明显,04∶00浓度最高,为8.30ng/mL,16∶00浓度最低,为2.08ng/mL。皮下埋植和口腔灌服外源褪黑素以后,血液中褪黑素浓度升高幅度较小;皮下注射46.4、4.64和0.464mg褪黑素后,血液中褪黑素浓度迅速升高,1h后达到峰值,分别为561.94、487.03、92.89ng/mL,极显著高于注射前（P〈0.01）;静脉注射46.4、4.64和0.464mg褪黑素后,血液中褪黑素浓度迅速升高,0.5h之后达到峰值,分别为767.68、639.19、110.56ng/mL,极显著高于注射前（P〈0.01）,高水平褪黑素可稳定持续48h。本研究证明了荷斯坦奶牛体内褪黑素分泌有明显的昼夜节律性,静脉或皮下注射外源褪黑素可以迅速提高血液中褪黑素的浓度,且血液中褪黑素的代谢速度与褪黑素的浓度高度相关,随着血液中褪黑素浓度的增加,褪黑素的代谢速度明显加快。

英文摘要：

In order to exploring the change pattern of melatonin in blood under the normal condi-tions of the multiparous Holstein cows within 24 h,the change of melatonin in blood of Holstein cows after the intravenous injection,subcutaneous implantation in neck,neck subcutaneous injection and drench were studied and the melatonin secretion rule and its metabolic rate were analyzed.The results showed that melatonin secretion changes obviously in the blood within 24 h,the concentration peak appeared at 04∶00（8.30ng/mL）,lowest at 16∶00（2.08ng/mL）.After subcutaneous implantation and drench,the concentration of melatonin in the blood rose relatively flat compared to other groups.Subcutaneous injection of 46.4,4.64 and 0.464 mg melatonin,the concentration in the blood rose rapidly,the peak appeared at 1hafter the injection,which were561.94,487.03,92.89ng/mL,respectively,extremely significantly higher than pre-injection（P〈0.01）.Intravenous injection of 46.4,4.64 and 0.464 mg melatonin,the concentration in the blood also rose rapidly,the peak appeared at 0.5hafter the injection,which were 767.68,639.19,110.56ng/mL,respectively,extremely higher than pre-injection（P〈0.01）.This study proved that the secretion of melatonin in the Holstein cows had obvious circadian rhythm,intravenous or subcutaneous injection of melatonin could improve the concentration of melatonin rapidly and there was a high correlation between the melatonin metabolic rate and the melatonin concentration in the blood,with the increase of the concentration of melatonin,the metabolism velocity was accelerated obviously.