In the Merino ram, it is unclear whether cryopreserved sperm function and fertility is compromised when collected during the non-breeding season, when Merino ewes are seasonally anestrus. It was therefore investigated whether treatment with melatonin could improve sperm function or fertility when semen was collected during the period Merino ewes were seasonally anestrus. There were 16 Merino rams treated or not treated with melatonin implants during the non-breeding season of ewes (September). Ejaculates were collected before melatonin treatment (Week 0), during the period of melatonin release (Week 7) and subsequent breeding season (Week 23). In vitro sperm function was assessed before freezing, and at 0- and 3 -hs post-thaw. Fertility was determined through intrauterine insemination of ewes (n = 966) with frozen-thawed samples, during the breeding season. Compared to Week 0 values, spermatozoa from melatonin-treated rams had greater progressive motility at Week 7 (P = 0.019) and less DNA fragmentation (P = 0.003) at Weeks 7 and 23, whilst spermatozoa from non-treated rams were unchanged during these time-periods. There were no other treatment effects on sperm function or fertility (P > 0.05). In ejaculates collected during Week 23, there were no effects of treatment either before freezing or post-thawing. Sperm from ejaculates collected at Week 23, however, had lesser pre-freezing/post-thawing total motility and resulted in lower pregnancy rates (P < 0.05). It is concluded there are no effects of season on sperm quality or fertility of Merino rams and that melatonin treatment subtly improves quality of spermatozoa following cryopreservation.

在美利奴公羊中，当美利奴母羊季节性无情时，在非繁殖季节收集冷冻保存的精子功能和生育能力是否会受到影响尚不清楚。因此，当在美利奴母羊季节性无情期收集精液时，研究褪黑激素治疗是否可以改善精子功能或生育能力。在母羊的非繁殖季节（9 月），有 16 只美利奴公羊接受或未接受褪黑激素植入治疗。在褪黑激素处理之前（第 0 周）、褪黑激素释放期间（第 7 周）和随后的繁殖季节（第 23 周）收集精液。在冷冻前和解冻后 0 小时和 3 小时评估体外精子功能。通过对母羊进行宫内人工授精来确定生育能力 ( n = 966) 冻融样品，在繁殖季节。与第 0 周的值相比，来自褪黑激素处理的公羊的精子在第 7 周具有更大的进行性运动（P = 0.019），在第 7 周和第 23 周具有更少的 DNA 断裂（P = 0.003），而来自未处理公羊的精子在这些期间没有变化时间段。对精子功能或生育能力无其他治疗影响（P  > 0.05）。在第 23 周收集的精液中，冷冻前或解冻后都没有治疗效果。然而，在第 23 周收集的精液中的精子在冷冻前/解冻后的总活力较低，导致妊娠率较低（P < 0.05)。结论是季节对美利奴公羊的精子质量或生育力没有影响，褪黑激素处理巧妙地提高了冷冻保存后精子的质量。