| Abstract: | In order to exploring the change pattern of melatonin in blood under the normal conditions 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 (8.30 ng/mL),lowest at 16:00 (2.08 ng/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 1 h after the injection,which were 561.94,487.03,92.89 ng/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 0.5 h after the injection,which were 767.68,639.19,110.56 ng/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. |
