I had been breeding Oldenburgs and Hanoverians for five years with fresh and frozen semen when, in 2007, I decided to try an equine embryo transfer (ET) with my dressage horse. I felt I was doing equine embryo transfer for all the right reasons: My mare was an upper-level competition dressage horse, and I didn’t want to interrupt her training schedule or stretch out her abdominal muscles. My dressage horse was dear to me, and there is always some risk to the dam during labor. She was one of only a handful of mares in the United States by Day Dream, a German Grand Prix dressage competitor who had had relatively few offspring.
All of my breeding work is done by theriogenologists (veterinarians who are board certified specialists in reproduction). It was because of the experience of my theriogenologist, Bill Ley, DVM, that I was willing to undergo the expense of an equine embryo transfer. Here is the basic ET drill:
• The donor mare is inseminated with a stallion’s fresh chilled or frozen semen around the time of ovulation to create an embryo.
• At 8 days old, the embryo is flushed out of the donor mare’s uterus and placed into a suitable surrogate mare that carries the pregnancy to full term.
The first time I tried ET, I opted to use my own surrogate mare. I found a sweet Shire who was in the ideal age range (5 to 10), in good health, had had at least one baby, was bigger than my donor mare and had a good personality.