Extended day length in late winter/early spring, with a return to natural day length of shorter duration, increased plasma testosterone and sexual performance in rams with or without melatonin implants

• Published in: Reproduction in domestic animals 2017-10, Vol.52 (5), p.851-856
• Main Authors: Abecia, JA, Chemineau, P, Keller, M, Delgadillo, JA
• Format: Article
• Language: English
• Subjects: Androgens; Animal behavior; Animal reproduction; Animals; Drug Implants; Estrus; Exposure; Female; Goats; Hormones; Implants; Life Sciences; Male; Mating; Melatonin; Melatonin - administration & dosage; Melatonin - pharmacology; Other; Photoperiod; Plasmas (physics); Rams; Reproductive Biology; Reproductive strategy; Seasons; Sexual Behavior, Animal - drug effects; Sexual Behavior, Animal - physiology; Sheep, Domestic - physiology; Spring; Testosterone; Testosterone - blood; Time Factors; Winter
• ISSN: 0936-6768; 1439-0531
• DOI: 10.1111/rda.12988

Contents Sixteen rams were used to quantify the effects of long days, imposed during late winter/early spring, with or without exogenous melatonin, on plasma testosterone concentrations and ram serving capacity. Rams were assigned to two groups: photoperiod‐treated rams (Artificial Photoperiod, AP; n = 8), exposed to 2 months of long days (16 hr of light/day) between 22 December and 22 February, and control rams (Natural Photoperiod, NP; n = 8). At the end of the long‐day period, AP rams were returned to the natural photoperiod, and each ram in the two groups either did (+M) or did not (‐M) receive three subcutaneous melatonin implants. Four groups were created as follows: AP+M (n = 4), AP‐M (n = 4), NP+M (n = 4) and NP‐M (n = 4). Thirty days after of the onset of photoperiodic treatment, AP rams (13.5 ± 2.8 ng/ml) had significantly (p