Success rates when attempting to nonsurgically collect equine embryos at 144, 156 or 168 hours after ovulation.

The research article presents a study assessing the exact time when an equine embryo arrives at the uterus. Through non-surgical methods, these examinations were done at various time intervals post-ovulation to determine a timeline and correlation between ovulation and embryo development.

Research Methods

• The test sample consisted of 101 horses subjected to an ovulation induction procedure. The process was monitored through frequent ultrasound examinations starting from 32 hours after the administration of specific hormones.
• The hormones used for inducing ovulation were crude equine pituitary gonadotrophin, human chorionic gonadotrophin, or buserelin, administered in four injections. The exact timing of ovulation was critical for the success of the study.
• Non-surgical uterine flushings, a method for collecting embryos, were conducted at three time intervals: 144 hours (Day 6), 156 hours (Day 6.5), and 168 hours (Day 7) following ovulation.

Research Findings

• Out of the 101 mares that underwent the ovulation induction treatment, 61 mares (approximately 60.4%) ovulated between 32-44 hours post-injection.
• A total of 60 embryo collections were undertaken, yielding different results at different time intervals. No embryos were collected at 144 hours, but 9 out of 17 embryos (53%) were recovered at 156 hours and 12 out of 23 embryos (52%) were recovered at 168 hours.
• Further, the study revealed that the diameter of the embryo on Day 7 (244 +/- 15 microm) was noticeably larger than on Day 6.5 (186 +/- 9.1 microm), highlighting that the size of the embryos varied within the same mare, post-natural multiple simultaneous ovulations.

Research Conclusion

• The study concluded that horse embryos enter the uterus between 144 and 156 hours after ovulation.
• An important insight from the study was that there isn’t a consistent time interval between ovulation and fertilization in mares. That points to the possibility that the rate of embryonic development may differ between individual embryos.

The above conclusions could significantly impact the understanding and practices of equine reproduction. The knowledge gained may contribute to more successful breeding strategies in the future.