The Effects of Exogenous Melatonin on Sperm Characteristics of West African Dwarf Goat Bucks

Abstract

Twelve West African Dwarf Goat (WADG) bucks (12-15months aged) were randomly allotted to four groups and were caged, individually. In the melatonin treated groups (M), bucks were orally administrated 3 mg, 6 mg and 9 mg of melatonin per animal per day between 9.00 and 10.00 a.m. The control received no melatonin. During the experimental period of 60 days, duration of hot hours measured (≥32 ºC) per day, ranged between 6 to 10 hrs with an average of 8 hrs. Bodyweight and scrotal circumference were measured weekly; blood sera collected weekly for hormonal assay and semen was collected at 7, 14, 21 and 28 days after administration of the hormone to evaluate sperm quality. Melatonin administration improved bodyweight, significantly increased the overall sperm characteristics such as mass activity, mass motility, sperm concentration, percentages of normal live sperm (P<0.05) and decreased unripe, abnormal and dead sperm percentages (P<0.05). However, numerical increase in testosterone of Melatonin treated bucks was statistically significant (p<0.05). As a result, melatonin had a positive effect on reproductive status of WADG as shown by significant higher testicular development, testosterone and sperm quality. However the effect of melatonin was more pronounced in the 9 mg group than the 3 mg and 6mg in all the parameters considered. Higher scrotal circumferences and testosterone and sperm quality of bucks from melatonin-treated groups might be indicative of the positive effect of melatonin on growth. However this needs further investigation.

Keywords: West African Dwarf Goat; bucks; melatonin; sperm characteristics; sperm quality