Effect of Melatonin on Buffalo Bull Sperm Freezability, Ultrastructure Changes and Fertilizing Potentials

Cryopreservation induces sublethal damage to the spermatozoa, which leads to reduce their fertile life. The objective of the present study was to investigate the effect of melatonin on freezability, ultrastructure and fertilizing potentials of the buffalo spermatozoa. Buffalo spermatozoa were cryopresreved with Tris egg yolk extender containing 7% glycerol supplemented with (0.100, 0.250, 0.500, 0.750 and 1 mM melatonin) or Tris-based extender only (control). Cryopresreved spermatozoa were assessed for post-thawing sperm motility, viability and acrosomal integrity, ultrastructure changes and fertilizing potentials. The current results clearly indicated that adding 0.1 mM melatonin to Tris extender significantly improved (P<0.05) post-thawing sperm motility and viability index following cryopreservation (60.00±2.9% and 157.5±11.8, respectively) compared with the control spermatozoa (45.00±2.90% and 97.00±9.09, respectively). The current results illustrated that addition of 0.1mM melatonin protected the plasma membrane, acrosomal region and mitochondria and maintained the ultrastructure integrity of the cryopresreved spermatozoa compared with the control spermatozoa. The present data indicated that addition of melatonin at a dose of 0.1 and 0.25 mM to the semen extender significant increased (P< 0.05) the positive HOST percent (83.66 and 81.33%, respectively) compared with the control semen (43.33 %). Additionally, the current results revealed that addition of 0.1 mM and 0.25 mM melatonin to the semen extender highly significant increased (P< 0.01) the pregnancy rate (66.67 and 60.43%, respectively) compared with the control semen (45.65%). Therefore, the present results revealed that addition of melatonin to the freezing extender might improve semen quality and reduce cryodamage of the buffalo bull spermatozoa.