Association of melatonin administration with testicular function, testicular artery hemodynamics, and spermatologic parameters in rams in the out-of-season

Off-season estrous behaviors must be induced in ewes, and reproductive activities take place in the spring to maintain the balance of production throughout the year. The study aimed to investigate the correlation between exogenous melatonin administration in non-breeding season rams and its effects on testicular morphometric measurements, spermatological parameters, and testicular hemodynamics. Additionally, the study aimed to elucidate the relationship between melatonin and the KISS1 gene, which is believed to play a role in the functional mechanism of melatonin, and to explore the clarity of metabolic mechanisms associated with this gene. For this purpose, 10 sexually mature with equal body condition score Bafra rams were randomly assigned to the control group (n=5) and the melatonin group (n=5). A melatonin implant (RegulinÒ 16 mg melatonin) was administered twice to the melatonin group. Measurements and analyses were performed six times: once in the week before, once during, and once three weeks after melatonin implantation (W -3, W 0, W 3, W 6, W 9 ve W 12). Testicular morphometric changes and testicular hemodynamics were monitored by color Doppler ultrasonography during this period. Spermatologic parameters, morphology, and plasma membrane integrity were evaluated. The ELISA method determined blood plasma hormone profiles, total antioxidant, and total oxidant measurements. Total RNA isolation, cDNA extraction, and Real-time polymerase chain reaction (qRT-PCR) analysis were performed on semen samples. qRT-PCR results revealed the presence of KISS1Rs in spermatozoa. Melatonin treatment of rams did not affect semen volume or semen concentration during any of the sample collection periods (p>0,05). In the melatonin group, testicular volume significantly increased, and this increase was statistically significant at 6, 9, and 12 weeks after melatonin injection (p<0,05). The melatonin group showed lower resistance and pulsatility indexes than another group at Weeks 3 to 9, with statistically significant differences (p<0,05). However, there were no significant differences (p>0,05) between the two groups in most semen quality parameters. Differences in KISS1R gene expression levels between the control and melatonin groups were categorized by weeks, and a statistically non-significant increase was observed in the melatonin group (p>0,05). In conclusion, melatonin administration significantly altered testicular blood flow and testis volume, and increased total antioxidant concentrations in out-of-season rams.