Photoperiod and melatonin treatments for controlling sperm parameters, testicular and accessory sex glands size in male Iberian ibex: A model for captive mountain ruminants

This study examines whether photoperiod and/or melatonin treatments can improve sperm variables outside the breeding season in the Iberian ibex–a model species for wild mountain ruminants–thus helping in the collection of high quality sperm beyond the normal breeding season for depositing in genetic resource banks. Adult Iberian ibex males (n = 17) were divided into four treatment groups: (1) controls under the natural photoperiod (control group; n = 4), (2) treatment with melatonin implants on December 22nd, February 22nd and April 22nd (group WS-M; n = 5), (3) treatment with short photoperiod cycles, i.e., 2 months of long days followed by melatonin implants (to emulate 2 months of short days) throughout the year (group PHPld + M; n = 4), and (4) treatment with melatonin implants on June 22nd and August 22nd (group SS-M; n = 4). The interaction treatment x season had a strong influence on testis size (P < 0.05), the size of the seminal vesicles (P < 0.001), the percentage of abnormal sperms (P < 0.05), and percentage non-progressive (P < 0.05) and progressive (P < 0.001) sperm motility. In groups WS-M and PHPld + M, the normal springtime physiological reductions in testis size, non-progressive sperm motility and acrosome integrity were prevented. The values for the studied sperm variables were, however, reduced in the natural breeding season at the end of the experimental period in group PHPld + M, although not in group WS-M. The pattern of melatonin administration in group SS-M conferred no advantages on reproductive functionality. These results suggest that lengthening the short day period after the winter solstice (the WS-M treatment) extends reproductive activity in this species, allowing good quality sperm to be recovered for conservation purposes during the non-breeding season.