The use of Gn-RH for controlling the oestrous cycle of the mare (preliminary report).

This research article explores the effectiveness of synthetic gonadotrophin-releasing hormone (Gn-RH) in inducing ovulation in mares, during the breeding seasons of 1973 and 1974. The study found that Gn-RH could successfully stimulate ovulation in mares with inactive and sub-normally active ovaries and to a lesser extent, those with cystic ovaries.

Objective and Methodology

• The main aim of the study was to investigate the usefulness of synthetic gonadotrophin-releasing hormone (Hoechst) in controlling the oestrous cycle of the mare.
• The study was conducted over the breeding seasons of 1973 and 1974.
• A total of 128 mares were used in the study. These were injected with 1-0 to 4-0 mg of Hoechst intramuscularly.
• The mares were divided into five categories based on their ovarian condition – this categorization was determined by clinical evidence.

Findings

• The research found some success in inducing ovulation in mares with inactive and sub-normally active ovaries. This implies that the synthetic hormone was able to stimulate ovulation to some degree in these categories of mares.
• In a smaller group of mares with cystic ovaries, the hormone was also able to induce ovulation albeit with lower success rate.
• However, for mares with a mature follicle, a large proportion responded within 48 hours of synthetic hormone injection.
• On the contrary, mares with atretic follicles did not respond to the hormone.

Discussion and Conclusion

• The varying degree of success in ovulation induction among the different groups of mares provides a useful basis for further exploration of the efficacy of Gn-RH in equine reproduction. The less successful response in mares with cystic and atretic follicles suggests that other factors may be influencing their ability to ovulate even with the administration of Gn-RH.
• Overall, the research indicates that Gn-RH may hold promise for controlling the oestrous cycle of the mare, particularly for those with inactive or sub-normally active ovaries and those with mature follicles. However, for mares with atretic or cystic follicles, more investigation is needed to ascertain its effectiveness.