Effect of melatonin implantation to sperm donor rams on post-thaw viability and acrosomal integrity of sperm cells in the breeding and non-breeding season

The influence of melatonin administration to sperm donors on the freezabili ty of ram semen and enzyme leakage through sperm cells during different ste ps of the cryopreservation process were evaluated in the breeding and non-b reeding season. Melatonin implantation to rams in the breeding season impro ved post-thaw sperm viability and intact acrosome rates without influencing the motility rate (p < 0.05). Likewise, the post-thaw alkaline phosphatase release through sperm cells was significantly lower in the melatonin-treat ed group in comparison with untreated controls (p < 0.05). In the non-breed ing season, melatonin administration enhanced intact acrosome rates (p < 0. 05) and reduced aspartate aminotransferase activity (p < 0.05) postthaw in the offseason ejaculates. Melatonin implantation twice in the breeding and non-breeding season did not produce any further improvement in the post-tha w sperm parameters in the non-breeding season ejaculates. It was concluded that melatonin administration to sperm donors improved freezability of ram semen collected from these rams and reduced enzyme leakage through sperm ce lls during cryopreservation.