GnRH Administration Increases Synchronisation of Ovulation in Mares

Area of Science:

• Veterinary Medicine
• Reproductive Biology
• Animal Science

Background:

• Estrus synchronization in mares is crucial for efficient artificial insemination programs.
• The spring transitional period presents challenges for reproductive management due to acyclicity.
• Optimizing ovulation timing is key to improving conception rates in mares.

Purpose of the Study:

• To evaluate the impact of exogenous gonadotropin-releasing hormone (GnRH) administration on estrus synchronization in mares during the spring transition.
• To assess the effects of GnRH on ovulation induction and insemination timing.
• To determine if GnRH administration influences pregnancy rates in synchronized mares.

Main Methods:

• Estrus synchronization using a progesterone-releasing intravaginal device (PRID) and cloprostenol.
• Administration of GnRH agonist (triptorelin) or saline placebo at PRID insertion.
• Ovulation induction with human chorionic gonadotropin (hCG) based on dominant follicle size.
• Insemination every 12 hours until ovulation, confirmed by transrectal palpation and ultrasound.

Main Results:

• GnRH administration significantly accelerated and concentrated the timing of ovulation induction and insemination compared to the control group.
• The dispersion of ovulation and insemination days was reduced in the GnRH-treated group.
• No significant difference in pregnancy rates was observed between the GnRH and control groups.

Conclusions:

• GnRH administration at the beginning of estrus synchronization protocols effectively enhances ovulation synchrony in mares.
• While improving ovulation timing, GnRH did not lead to a higher pregnancy rate in this study.
• Further research may be needed to optimize GnRH use for improved fertility outcomes in equine reproduction.