Effect of exogenous melatonin administration on levels of sex hormones in West African Dwarf (WAD) sheep in the dry season

摘要

The effect of exogenous melatonin administration on levels of sex hormones in West African Dwarf (WAD) sheep in the dry season were investigated in an experiment with twenty WAD sheeps (10 ewes and 10 rams) aged 1-1.5 years, which were allotted to two treatments. Levels of the reproductive hormones of the twenty WAD sheep before experiment were determined. Melatonin was administered at 0 mg (T1) and 5 mg (T2) to each treatment, containing 5 ewes and 5 rams for 10 consecutive days. Blood sample (5mL) was collected from the sheep to determine luteinizing hormone (LH, mIU/mL), follicle stimulating hormone (FSH, mIU/mL), estrogen (estradiol) and testosterone. Before treatment in ewes, estradiol ranged between 201 and 1107 pg/mL, LH ranged between 5.70 and 14.80 Miu/mL, and FSH ranged between 0.60 and 8.20 Miu/mL. In rams, testosterone ranged between 0.10 and 2.80 ng/mL, LH level ranged between 2.80 and 5.30 Miu/mL and FSH ranged between 0.30 and 5.30 Miu/mL. Testosterone (0.40±0.14ng/mL), LH (5.94±0.74Miu/mL) and FSH (0.64±0.08Miu/mL) of the control group (0mg) fell within the ranges of the endogenous sex hormones before treatment. In rams, at 5mg melatonin administration the testosterone was not significantly different across the treatment groups. LH and FSH were significantly (P<0.05) higher (10.68 Miu/mL and 4.86 Miu/mL, respectively) than the control group (5.99Miu/mL and 0.64Miu/mL, respectively). In the ewes estradiol (1127.00±298.50pg/mL), LH (5.66±2.99Miu/mL) and FSH (6.80±1.20Miu/mL) of the control group (0mg) fell within the ranges of the endogenous sex hormones before treatment.The LH and FSH were significantly (P<0.05) higher (24.22 Miu/mL and 18.06 Miu/mL, respectively) than the control group (5.66 Miu/mL and 6.80 Miu/mL, respectively). In conclusion exogenous melatonin influenced the level of FSH an LH capable of enhancing reproduction during this season.