Antioxidant effect of Melatonin on the buffalo sperm parameters after freeze thawing process

This study was carried out to evaluate the potential impact of melatonin on the frozen–thawed semen quality of buffalo. Ejaculated semen was extended in a Tris–citrate egg yolk and bioexcell extenders containing various concentrations of melatonin (0, 1.0, 50 and 100 μM). After cooling at 5ºC, semen samples were frozen in liquid nitrogen vapor and plunged into liquid nitrogen for storage. Straws from each treatment were thawed at 37 °C water bath for 45 s to assess the semen quality in terms of sperm motility, viability, plasma membrane integrity and acrosomal integrity at 0 and 6 h after thawing. Post-thawed sperm motility was determined using a phase-contrast microscope. Viability, plasma membrane integrity and acrosomal integrity were evaluated by the supravital staining, hypo-osmotic swelling test and normal acrosomal reaction, respectively.Adding melatonin in two extenders conferred better cryopreserving ability to spermatozoa compared to control groups. The highest (P < 0.05) value was achieved by addition of 100 μM melatonin upon and 6 h after thawing.