CEPS/Veterinary Extension
2938 Vet. Med. Basic Sciences Bldg.
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907

By Linda March
Information Specialist
University of Illinois
College of Veterinary Medicine

Your cutting mare is putting you in the money every time out and you would like to breed her to the top stallion in the country, but you still want her to perform. What do you do?

One option is embryo transfer. According to Dr. Ted Lock, an equine veterinarian at the University of Illinois College of Veterinary Medicine in Urbana, "Embryo transfer is the process of moving an embryo (the fertilized egg) from the donor mare to a recipient mare. One reason to use embryo transfer is to keep the performance mare on the circuit and let her reproduce at the same time."

Other advantages of embryo transfer are obtaining more offspring from a mare who has outstanding genetics, producing foals from a two-year-old mare, and obtaining foals from mares who can conceive, but not carry the pregnancy to term.

The donor mares are bred either by natural service or artificial insemination. On the seventh day after ovulation the embryo is collected from the donor mare by flushing her uterus with a specially prepared solution. That solution is then filtered and examined for embryos. The embryo is then either transferred to a recipient mare on the same site, stored for up to 36 hours at about 5 degrees Centigrade, or stored at -196 degrees Centigrade, for an extended period of time. Once a living embryo is recovered, it is implanted into the recipient mare. "The best results are usually obtained from surgical implantation of the embryo into the uterine horn," Dr. Lock notes.

The recipient mare's estrous cycle must synchronize with the donor mare's cycle for a successful transfer to occur.

"Recipient mares should be young, and reproductively sound," Dr. Lock says. The stallion needs no special care other than general good management. The donor and recipient mares may be treated with hormones to synchronize their reproductive cycles.

As a rule, embryo transfer is done by a veterinarian, reproductive physiologist, or reproduction specialist. The procedure is still limited, however, and cost may be prohibitive. Some breed registries do not allow embryo transfer horses.

If you have any questions about embryo transfer ask your veterinarian or your breed's registry for more information.