Cryosurvival of goat spermatozoa in tris-egg yolk extender supplemented with melatonin
The effect of melatonin supplementation in semen extenders on cryosurvival of spermatozoa obtained from West African Dwarf (WAD) goat bucks was studied. Tris-egg yolk extenders supplemented with different levels of melatonin (0, 2, 4, 6 and 8 mM) were diluted with semen samples. The diluted semen samples were cryopreserved for 30 days and thereafter evaluated for sperm quality characteristics. Following cryopreservation, acrosome reaction and capacitation of spermatozoa were induced in vitro. The results showed higher (P<0.05) sperm motility, acrosome integrity and membrane integrity in extenders supplemented with melatonin compared to the control and these parameters were optimal at 6 mM and 8 mM of melatonin (P<0.05). Extender supplemented with melatonin at 8 mM consistently improved acrosome reaction and capacitation of spermatozoa (P<0.05). The results showed reduced (P<0.05) sperm abnormality and malondialdehyde concentrations in extenders supplemented with melatonin compared to the control and these parameters were lower at 6 mM and 8 mM respectively. The findings revealed that 8 mM of melatonin supplementation in tris-egg yolk extender was consistently effective for improving viability of spermatozoa of WAD goat bucks during cryopreservation.