The first ovulation of the breeding season in the mare: the effect of progesterone priming on pregnancy rate and breeding management (hCG response rate and number of services per cycle and mare).

This research paper investigates the impact of progesterone priming on the pregnancy rate and breeding management of mares during their first ovulation of the season. The study found that, while progesterone priming did not significantly affect pregnancy rates, its use improved the breeding management by enhancing hCG response and reducing the number of services per cycle.

Objective of the Study

• The study aimed to compare mares’ pregnancy rates during the first ovulation of the year with that of mares undergoing their second or subsequent ovulations, and mares with progesterone-primed first ovulations.

Methodology of the Study

• Researchers observed 136 thoroughbred mares, subsequently categorized into four groups based on the stage at which they were mated: the first ovulation of the year, the first ovulation of the year after removing a previously inserted progesterone device, the second or further ovulations after inducing estrus with prostaglandin, and spontaneous return to estrus.

Key Findings

• The study found no significant difference in pregnancy rates among all four groups, signaling that the first ovulation of the year, progesterone-priming, or later ovulations do not have a clear advantage in terms of leading to pregnancies.
• However, it was noted that mares mated during the first ovulation of the year displayed the lowest response to hCG treatment, implying a higher number of services per cycle.

Conclusion

• The use of progesterone priming, while does not directly boost pregnancy rates, helps streamline the breeding management of mares in their transitional phase. It leads to a greater hCG response rate, thus limiting the number of necessary services per cycle.