Season does not influence embryo recovery rate and conceptus size until day 14 after ovulation in the horse.

The researchers conducted a retrospective study that showed embryo recovery rates and the size of the conceptus in horses didn’t vary with seasons.

Research Background

• The paper addresses the seasonal breeding nature of horses and the hypothesis that horse embryo growth could be slower during the non-breeding season.
• Since smaller embryo sizes are beneficial for cryopreservation, collecting embryos outside the breeding season could be productive for freezing horse embryos.

Methodology

• The research was conducted on 30 mares over different seasons of the year.
• The size of the conceptus diameter was determined after collection using a microscopic scale (day 7-10 after ovulation) or through transrectal ultrasound before collection (day 11-14 after ovulation).
• In total, 352 embryo collections were performed and analysed.

Findings

• The study found that a total of 63% of the mares cycled throughout the year, regardless of the season.
• The mean recovery rate of embryos was 64.2%, and it was not influenced by the season.
• The size of the conceptus also didn’t change with seasons, however, it significantly increased with each day of pregnancy.

Conclusion

• Overall, the study concludes that it’s possible to successfully collect horse embryos all year round in spontaneously cyclic mares.
• Additionally, the study dispels the hypothesis of slower embryo growth in the non-breeding season, finding that neither collection rates nor embryo growth appeared to be affected by the season.