Duration of oestrus and time of ovulation in mares treated with synthetic Gn-RH (AY-24,031).

The researchers investigated the impact of a synthetic hormone called Gn-RH on the estrus cycle and ovulation timing in mares. They found that administration of this synthetic hormone during estrus leads to shorter estrus periods and might potentially also influence the timing of ovulation.

Examination of Synthetic Gn-RH

• The research team experimented with synthetic Gonadotropin-Releasing Hormone (Gn-RH, AY-24,031) on mares in their estrus cycle. The Gn-RH is a type of hormone that provokes the pituitary gland to release Luteinizing Hormone (LH), which in turn stimulates ovulation and reproduction in females.
• The primary goal of the study was to examine the effects of this synthetic Gn-RH on the duration of estrus and the timing of ovulation in the mares.

Experimentation and Results

• Mares were administered 1 mg of this synthetic Gn-RH on Day 2 of their estrus cycle. The researchers identified a significant reduction in the estrus period for these treated mares.
• The study also witnessed a similar impact on the timing of ovulation, though the effects were less pronounced than that on estrus duration.
• To further explore the effects of this synthetic Gn-RH, the team administered an increased dose of 2 mg but observed no additional changes in the duration of estrus or ovulation timing.
• However, they noted that consistent daily injections from the second day of the estrus cycle until ovulation resulted in significant reductions in both the duration of estrus and the time to ovulation.

LH Profiles and the Link to Ovulation

• The study also monitored the LH profiles in the mares during the experiment. They found that these profiles vary from one mare to another.
• Despite these differences, a common trend was found across all mares, whether treated with synthetic Gn-RH or not. An increase in LH was detected close to the time of ovulation in all cases.
• This suggests a crucial link between LH levels and ovulation timing, reiterating the role of LH in triggering ovulation.