What is embryo transfer? Embryo transfer (ET) is a procedure that is becoming more and more popular in the equine world for obtaining foals. This technique involves recovering embryos from bred (donor) mares and placing them in a recipient mare that, in turn, carries the foal. There are several reasons for the use of this procedure. Multiple foals can be produced from one mare (possibly genetically superior) in a breeding season. It can be used to produce foals from mares that cannot take time off from racing or showing. Embryo transfer can also be used to produce foals from subfertile mares that are unable to successfully carry a foal to term. Young fillies that can produce viable embryos but are not yet able to carry them may be used as donor mares. Older mares no longer capable of carrying a foal also may make good candidates for embryo transfer.

How is embryo transfer performed? Embryo transfer involves the use of a donor and recipient mares who must be synchronized in their estrous cycles. Both mares should be healthy, reproductively sound and cycling regularly. During the breeding process the mares are examined daily to accurately determine the day of ovulation. Seven days after the donor mare is bred her uterus can be flushed to recover the embryo. Several liters of flush media are warmed and infused into the uterus through a catheter. The uterus is flushed several times and drained into a filtered collection bottle. The collected embryo(s) is washed to remove any contaminants and evaluated for viability based on their size, grade, morphology and developmental stage. It is placed into a nutrient media. Non-surgical embryo transfer is the method most commonly used in private practice, but does have a slightly lower success rate than surgical transfer. When transferring the embryo to the recipient mare, it is important that she had ovulated no more than one day before and two days after the donor mare. The embryo is placed in a straw attached to an insemination gun. The gun is placed in transcervically into one uterine horn aided by rectal palpation. The embryo is deposited and the gun is removed and checked to make sure no embryo remains in the straw. Only the most valuable embryos are used for transfer in order to maximize the use of the recipient mare and not waste her time on poor quality embryos. The first pregnancy checks are usually 5 and 7 days after transfer, which would be days 12 and 14 after ovulation.

What is the success of Embryo Transfer? Success rates for embryo transfer can be measured for two facets of the procedure:

1. Embryo recovery from the donor mare;
2. Establishment of pregnancy in the recipient mare.

Embryo recovery is usually the rate-limiting step in equine embryo transfer. Recovery rates will vary with the individual mare's fertility; young mares can have very high rates, typically around 80% per cycle. Older mares with history of infertility, as a group, will have recovery rates around 30% per cycle. Individuals within these groups will have higher or lower recovery rates. Once the embryo is recovered, one can expect a pregnancy success rate of approximately 75% at 14 days, with about a 10% rate of pregnancy loss following that time. Pregnancy rates for transported embryos are approximately 5-10% lower than for on-site transfer.

• Advanced Reproductive Services
• Mare Cycle Management
• Embryo Recovery and Embryo Transfer
• Commercial Embryo Transfer Station
• Embryo Shipments via Courier and Airline Delivery from Major Airport with Excellent Schedules
• Coordination with Recipient Mare Herd Facility and Contract Management
• Breed Registration Rule Compliance