Effect of deslorelin acetate on gonadotropin secretion and ovarian follicle development in cycling mares.

This study examines the impact of deslorelin acetate on hormone secretion and ovarian function in mares. The researchers found that use of the drug led to a reduction in some hormones and a longer interval between ovulations, suggesting it may affect the rate of follicular development and the estrous cycle in mares.

Objective of the Study

The primary aim of this research was to investigate how the administration of deslorelin acetate, a drug used to induce ovulation, affects the secretion of gonadotropins (hormones that influence growth and function of the ovaries) and the development of ovarian follicles in female horses with normal estrous cycles.

Methodology

• The research utilized a randomized controlled trial method, involving 16 healthy mares (female horses) with regular estrous cycles.
• Eight mares were assigned to a control group and were allowed to ovulate naturally, while the other 8 in the study group received deslorelin when an ovarian follicle larger than 35 mm in diameter was detected.
• The development of follicles and the daily serum concentrations of gonadotropins were closely monitored during one full estrous cycle.
• The responsiveness of the pituitary gland to the administration of gonadotropin-releasing hormone (GnRH) was evaluated ten days after the initial ovulation.

Results

• The interval between ovulations (interovulatory intervals) in mares treated with deslorelin (average 25.6 days) was longer compared to the control mares (average 22.9 days).
• The largest follicle’s diameter was notably smaller in deslorelin-treated mares during the two days of the diestrous period after ovulation, in contrast to the control mares.
• The concentrations of follicle-stimulating hormone (FSH) in deslorelin-treated mares were lower from the 5th to the 14th day, compared to the control mares. However, no noticeable difference was seen in luteinizing hormone levels between the two groups throughout most of the cycle.
• The gonadotropin release following the administration of GnRH was lower in mares that received deslorelin acetate compared to those in the control group.

Conclusions

• The study concluded that administering deslorelin was linked with a decrease in circulating concentrations of FSH, and in the gonadotropin response upon the administration of GnRH. This reduction in FSH levels in treated mares may result in delayed follicular development and a longer interval between ovulations.