Embryo Transfer

 

Embryo Transfer is the process of removing an embryo (a fertilized egg) from a broodmare and placing it in a surrogate mare where it develops into a foal.

Because of technology and a different standard of breeding rules, AQHA registered mares can sometimes pull double-duty in the breeding shed and on the racetrack. Embryo Transfer is not approved by the Jockey Club in registering Thoroughbreds. American Quarter Horse mares and Thoroughbred mares booked to a Quarter Horse stallion however, can be bred and returned to the racetrack to continue training and racing following the successful transfer of her embryo to a surrogate mare.

The Embryo Transfer begins with breeding the donor mare (the mare "donating" the embryo) at Vessels Stallion Farm. Bred as usual, she is monitored with daily ultrasounds to establish the exact ovulation date, the date her egg is released.

On a synchronized schedule, Royal Vista Equine also monitors by ultrasound the recipient mares (the mares potentially "receiving" the embryo) looking for one mare whose reproductive cycle matches the donor mare's. It is very important that the estrus cycles be at the same point for a successful transfer to take place. Estrus detection is crucial to the process.

Seven days after the ovulation date, the donor mare's uterus is flushed. The fluid from her uterus is run through a special filter cup designed to catch the embryo. A transferable embryo is between the ages of 6 and 8 days old. At 5 days old, the embryo has not yet entered the mare's uterus and cannot be flushed. At 9 days old, the embryo is too large and fragile to handle. Flushing on day seven maximizes the chance of recovering an embryo of ideal transfer age.

The flushed fluid is thoroughly searched for an embryo under a microscope. A 7-day-old embryo is approximately ¼ to ¾ millimeters in size. It is visible to the naked eye if you know where it is. Precise care and preparation of embryo transfer equipment and media is crucial to the success of any embryo transfer program.

An embryo flushed at Vessels Stallion Farm's Reproduction Center is packaged and shipped via same-day delivery to Royal Vista Equine in Fort Collins, Colorado. Upon its arrival, the embryo is immediately transferred into a waiting recipient mare.

Genetically intact at recovery, the embryo contains all the genetic material it needs for its own development as well as for the placenta's development. The recipient mare provides nutrition with no direct blood transfer.

After the transfer, the recipients' new pregnancy can be seen by ultrasound within one week. Her uterus carries the donor mare's embryo naturally. Royal Vista Equine has recorded the pregnancy rates for shipped-in and on-site embryo transfers as the same.

The surrogate mare can later be shipped to the farm of the owner's choice. When she foals the following year, she raises the genetically unrelated foal as her own.