Effects of timing of induced luteolysis in embryo donor mares on reproductive performance and pregnancy rate in recipient mares.

This research aimed to explore the impact of administering prostaglandin F₂(α) (PGF) to horse mares 48 hours before embryo collection on their reproductive performance. The findings indicate that this approach reduces the average interovulatory interval without having negative effects on the number and quality of embryos recovered, or on the successful pregnancy rate in receiving mares.

Research Methodology

• The study, conducted from September 2004 to February 2005 in Brazil, involved 10 mares for a total of 20 estrous cycles. The mares varied in age from 2.5 to 10 years and weighed between 400 to 500 kg.
• The mares were randomly assigned in a cross-over design study. In a Treated cycle, each mare received 7.5 mg of PGF 48 h prior to embryo collection. In a Control cycle, the mares received the PGF at the time of embryo collection.

Findings

• In the Treated cycles, the researchers noted a significant reduction in serum progesterone concentrations between the day of administering PGF and the day of embryo collection.
• The interovulatory interval was found to be shorter in the Treated cycles compared to the Control cycles. However, there was no significant variation observed in the interval from PGF administration to ovulation.
• There was no significant difference witnessed in the embryo recovery rate (average, 75%), embryo quality, uterine protein concentration, or the pregnancy rate in recipient mares (average, 87% at 15 days post-ovulation).

Conclusion

• According to the results, giving mares PGF 48 hours prior to embryo collection helped in reducing the average interovulatory period by approximately 2.5 days.
• This change potentially increases the number of embryos that can be collected in a breeding season.
• Moreover, this timing didn’t cause any negative effects on the embryo recovery rate, the quality of the embryos, or the pregnancy rate in the recipient mares.