The effect of oxytocin and prostaglandin hormones added to semen on stallion sperm quality

Prostaglandin F-2 alpha (PGF(2 alpha)) and oxytocin have been used to improve reproductive performance in many mammalian species, including humans. The aim of the present study was to determine their effects on sperm quality when extended stallion semen was enriched with PGF(2 alpha) or oxytocin. In this study, 16 healthy adult stallions, each 15-22 years old, were used. Five ejaculates from each stallion were collected with an artificial vagina during breeding season. Thereafter, gel-free semen was divided into 7 aliquots and diluted with an INRA96 semen extender. The following different treatments were evaluated: 3 with only PGF(2 alpha) (10, 20, and 40 mu g/mL) and 3 with only oxytocin (2, 3, and 4 IU/mL). Sperm quality was evaluated before and after applying the different treatments. In vitro addition of oxytocin to semen did not show improvement in any of the sperm quality parameters measured. However, sperm supplementation with 40 mu g of PGF(2 alpha) caused a significant increase (P < 0.05) in diluted semen motility. We concluded that the addition of PGF(2 alpha) to elder stallions' semen may help maintain sperm motility. Future research might assess the effects of PGF(2 alpha) on fertility. Our results were based on in vitro evaluations, and thus further fertility trials are required.