Effectiveness of exposure to longday followed by melatonin treatment on semen characteristics of Damascus male goats during breeding and non-breeding seasons

Eight mature Damascus male goats were randomly divided into two equal groups. The first group served as control and the second group was used to study the effect of exposure to longday (16L/8D) followed by melatonin treatment (2 mg/(animal/day)) on semen characteristics and blood hormonal levels during breeding and non-breeding seasons. During breeding season, longday exposure followed by melatonin treatments resulted in significant increases (P < 0.01) in means of sperm motility, ejaculate volume, sperm concentration, total sperm output, total functional sperm fraction and blood testosterone concentration, while means of reaction time, dead sperm, abnormal sperm and blood triiodothyronine (T-3) concentration were significantly decreased (P < 0.01). During non-breeding season, longday exposure followed by melatonin treatment exhibited improvements in some reproductive parameters by reducing (P < 0.05) reaction time and percentage of dead sperm (P < 0.01) and increasing (P < 0.05) total functional sperm fraction. Furthermore, longday exposure followed by melatonin treatment resulted in significant increases (P < 0.01) in both of blood testosterone and T-3 Concentrations. It is concluded that longday exposure followed by melatonin treatment successfully improve semen characteristics of Damascus male goats during breeding and non-breeding seasons. However, the beneficial effects were more pronounced during the breeding season. (C) 2009 Elsevier Inc. All fights reserved.