Transcervical embryo transfer in horses: an application in an equestrian teaching center.

This research explored the use of embryo transfer in horses at an equestrian teaching center. The aim was to maximize the number of offspring from favored mares in a single breeding season, while minimally disrupting their use in competition and teaching.

Methodology

• Five donor mares were selected for the experiment.
• Embryo collection was attempted on 25 occasions, roughly 6.5 days after each mare’s ovulation.
• Collection was done using uterine lavage, a method of flushing the uterus to collect the embryos.
• 64% of these attempts yielded a total of 17 blastocysts (early stage embryos).

Embryo Transfer and Results

• Of the collected embryos, 13 were immediately transferred into recipient mares via transcervical procedures.
• The recipient mares had ovulated within two days of the donor mares to ensure a compatible environment for the embryos to grow.
• Three embryos were frozen for future use, and one was lost.
• 61% of the freshly transferred embryos successfully developed and were detected via ultrasonography on the 11.5th day after the procedure.

Outcome of Transfer and Future Trends

• Five of these developing embryos continued to grow normally and eventually became healthy foals, translating to a 38% success rate in terms of live births.
• However, three embryos were lost at various stages of gestation, specifically at 14.5, 22.5 and 24.5 days.
• The two frozen embryos, when thawed the following year, were still viable. One of them yielded an additional pregnancy after being transferred transcervically.
• In conclusion, the five donor mares yielded five foals and a sixth healthy foal was born during the publishing of this paper. This was achieved with only a three-month interruption to the mares’ competition and teaching engagements.