Comparison of the effects of two GnRH antagonists on LH and FSH secretion, follicular growth and ovulation in the mare.

The research studies the impact of two GnRH antagonists, Antarelix and Cetrorelix, on delaying or synchronising ovulation in mares. It showed that the use of Antarelix resulted in stronger suppression of LH concentrations and more successful delay in ovulation compared to Cetrorelix.

Objectives of the research

• The primary objective of this research was to study and compare the impact of two Gonadotropin-Releasing Hormones (GnRH) antagonists – Antarelix and Cetrorelix – on Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH) secretion, follicular growth and ovulation in mares.
• The goal was to find out if the usage of either antagonist could effectively delay and/or synchronize ovulation in mares. This can potentially aid in reproduction control strategies in equine species.

Methods used in the research

• The study was performed on 15 mares, divided into three groups. Five mares received Antarelix, another five received Cetrorelix and the last group served as the control group and received only the vehicle (a substance in which the drug is dissolved).
• All interventions were administered intravenously, twice daily, for 8 consecutive days once the mares’ largest follicle reached a size of 22 mm. The size of the follicle was tracked post prostaglandin administration.

Findings of the research

• Administration of Antarelix successfully postponed ovulation in all the mares, delaying it to approximately 19 days after the commencement of the treatment.
• Cetrorelix managed to delay ovulation in two out of five mares, to roughly 20 days after the initiation of the treatment.
• On comparing with the control group that ovulated around 6 days after begin of treatment, both antagonists have been successful in delaying ovulation.
• The concentration of LH was strongly suppressed in both the Antarelix and Cetrorelix mares, as compared to the control group. However, the suppression was higher in the mares treated with Antarelix.
• The concentration of FSH remained unaffected in both treated groups vis-à-vis the control group.

Conclusion of the research

• Based on the results, Antarelix appears to be more effective than Cetrorelix in terms of postponing ovulation in mares.
• It can be affirmatively concluded from the study that LH plays a significant role in antral follicular development leading up to the preovulatory stage.