Embryo Transfer Expands Potential
To date, Weihegold has produced at least 12 foals via embryo transfer/ surrogacy and her babies are by such superstar stallions as Jazz, Totilas and Sir Donnerhall I.
As founder and owner of Palm Beach Equine Clinic, Dr. Scott Swerdlin oversees embryo transfers for multiple performance mares each year. His team of 26 veterinarians includes specialists in surgery, internal medicine, radiology, reproduction and fertility.
According to Dr. Swerdlin, “Embryo transfer is non-invasive and very safe.” He says the “trickiest part” of the procedure is getting the mare impregnated, so Dr. Swerdlin often brings mares to the clinic for a few days for insemination, which allows them to have an ultrasound every two hours. Frozen semen can then be deposited when and how the mare is most likely to take. Seven to eight days later, the embryo is flushed from the donor mare’s uterus and transferred to the recipient mare. The embryo collection itself is a procedure so simple it can take place in a field at the mare’s home stable. At Dr. Swerdlin’s home-base in Florida, where the weather is warm year-round, a mare may have 10 heat cycles per year and one could potentially furnish an embryo at each cycle.
The implication of this procedure for sporthorse breeding is immense. It implies that high-level sport mares like Weihegold can continue to compete while simultaneously having a prolific influence as a broodmare. According to Dr. Swerdlin, “It’s often somewhere around 11 or 12 years of age that you’ll know you have a really top mare—she’s hitting her performance peak. That’s the time to collect. If you’re not ready for the foal for whatever reason, you can freeze the embryo. A mare’s reproduction potential starts to decline at age 13 or 14, so these years can be so important in terms of collection. Formerly, we’d have about a 30 percent success rate with frozen embryos, but with the new procedure that we’re using [cell wall collapse] and specially trained technicians, we’re getting a 70 percent success rate.”
An important implication of the procedure is that top-performing mares can now be bred more frequently to diverse top-performing stallions to see which pairing yields the most impressive foal crops. For example, consider that 13-year-old Weihegold is still actively performing at the FEI level, but in past generations, she may not yet have had one foal and breeders certainly would not have had the opportunity to test her match with multiple influential stallions. Therefore, a mare’s progeny record today could conceivably be 10 times as great as it would have been if she’d carried the foals herself. Her influence on the breed may also be greater, as there’s more room to play with specific crosses and her performance record can be solidified over a lifetime, as opposed to lasting just a few years.