Testicular function and semen characteristics of Awassi rams treated with melatonin out of the breeding season

Abstract

The objective of this study was to evaluate the effect of long-term melatonin treatment applied during the non-breeding season on semen characteristics, endocrine function of testicles and baseline level of insulin-like growth factor-I (IGF-I) in Awassi rams kept in the temperate continental zone of Europe and used as semen donors in an artificial insemination (AI) programme. On 23 February (day 0), slow-release melatonin implants were inserted subcutaneously into rams (n = 8). Control animals (n = 8) received no treatment. In both groups, basic semen parameters (concentration, total motility, fast and slow forward motility, morphology), GnRH-induced testosterone response and basal IGF-I concentration were evaluated on days 0, 47 and 71. No differences were found in concentration of spermatozoa, total motility, and numbers of spermatozoa with fast and slow progressive motility and normal/abnormal morphology between the melatonintreated and the control group. However, in melatonin-treated animals, basal and GnRH-induced testosterone levels were slightly elevated on day 47 and became significantly higher on day 71 (P < 0.05) as compared to controls. There was no difference in plasma IGF-I levels between the groups. In conclusion, slow-release melatonin applied during the non-breeding season improves testicular testosterone production but does not influence the semen characteristics and the IGF-I level of semen donor Awassi rams used in an AI programme and kept in the temperate continental zone of Europe.

Comparison of sexual performance and testicular characteristics of melatonin treated Kivircik and Charollais rams during the non-breeding season

“…Rosa et al (2012) reported the same trend for SC in Charollais and Texel rams without any significant difference. In agreement with our findings, others (Faigl et al, 2009;Palacin et al, 2008) found that the testicular weight of the implanted animals increased 2-3 weeks after the onset of melatonin treatment and reached its maximum 5 weeks later. Palacin et al (2008) reported that melatonin treatments during the non-breeding period can increase testicular growth.…”

“…Sperm production is correlated to testicular measurements. Scrotal circumference will vary with season and body weight, but should be at its maximum peak during the fall breeding season (Egerszegi et al, 2014;Faigl et al, 2009;Palacin et al, 2008).…”

“…Melatonin can be used alone, or combined with other hormonal treatments, after an artificial light treatment. Treatment with melatonin during non-breeding season can revert the 'long-day effect' over the ram (Faigl et al, 2009;Rosa et al, 2012;Zuniga et al, 2002). In mature rams, the insertion of melatonin implants facilitated testicular growth with an elevated testicular size, sexual behaviour and improved semen characteristics in different breeds (Casao et al, 2010;Chemineau et al, 1996;Egerszegi et al, 2014).…”

Melatonin modifies scrotal circumference but not plasma testosterone concentrations and semen quality of rams during the seasonal anestrus at 43°S

“…It is likely that melatonin administration initiated in spring, without a priming period of long days preceding the treatment, is not sufficient stimulus to increase sperm production, as has been described by Rosa et al (2012). Moreover, in a study carried out in Hungary (Faigl et al, 2009) no differences were found in concentration of spermatozoa, total motility, and number of spermatozoa with fast and slow progressive motility and normal/abnormal morphology between the melatonin-treated rams and control group, although, in melatonin-treated animals, basal and GnRH-induced testosterone levels were slightly elevated on day 47 and became significantly higher on day 71 as compared to controls. Bravo and Roy (2003), who used melatonin implants in Ile de France, Merino Precoce and Fleischschaf rams, found no statistical differences on ejaculate volume, only sperm concentration for those animals implanted with melatonin was statistically significant.…”