Embryo Transfer

Pioneering work and diligent attention to detail for more than 30 years has resulted in the recognition of our embryo transfer program at Equine Medical Services as one of the largest and most successful in the country. Several thousand foals from approximately 30 breeds have been produced as a result of EMS embryo transfers. With a recipient herd exceeding 800 mares, Equine Medical Services generally has several recipient mares ready to receive an embryo on any given day.

What is embryo transfer?

Embryo transfer is the process of recovering an embryo from a donor mare approximately seven days after conception and transferring it to another mare, the recipient. The recipient mare then becomes pregnant and carries the foal to term. Embryo transfer has proven to be incredibly useful to horse breeders in a variety of capacities. Common uses include obtaining multiple foals per year from top producing mares, producing foals from mares in training or showing and producing foals in mares with fertility problems.

What to expect from the embryo transfer process

During the breeding process, mares are examined daily to accurately determine their days of ovulation. Approximately one week after ovulation, the donor mare’s uterus is flushed with an electrolyte- and nutrient-rich solution via a catheter insertion. This solution is filtered and the embryo, which is typically 300-500 microns (0.3-0.5mm in diameter), is recovered microscopically for evaluation.

After recovery and evaluation, the embryo is carefully washed to remove contaminants and placed in a nutrient media for transfer through the cervix into the uterus of a specially prepared recipient mare. The first pregnancy checks typically occur four and seven days after transfer, or 11 and 14 days past ovulation.

Successful rates for embryo transfer are measured on two facets of the procedure: embryo recovery from the donor mare and establishment of pregnancy in the recipient mare. In equine embryo transfer, embryo recovery is generally the rate-limiting step as recovery rates vary with individual mares’ fertility―younger mares can have rates as high as 80% per cycle, while older mares with histories of infertility may have average rates closer to 30%.

Once the embryo is recovered, the expected rate of pregnancy success is approximately 80% at 14 days with an estimated loss of 10% after that time.

Success for In-Clinic (On-Site) Transfers, 1998-2023

Success for Transported Transfers, 1998-2022

Overall Transfer Success, 1998-2023: 6,498/7,865 OR 82.6%

Recipient mares are provided by Equine Medical Services and are leased to the owner at 30 days in foal, and are to be returned to us within 6 months of foaling. We provide a live foal guarantee after the recipient mare is 30 days pregnant, providing the owner a $2,000 credit toward future embryo transfer services in the event of a pregnancy loss. Owners can use their own recipient mares with some limitations.

A non-transferable and non-refundable annual enrollment fee is required for each donor mare. If foals from a donor mare will belong to different owners, we recommend handling them through one account for maximum cost effectiveness. However, if billing to different owners is desired, each owner will be required to complete a contract and pay a nomination fee.

Standard In-House Transfer Program

2024 annual enrollment fee: $1,350

This fee is designed to cover the cost of ultrasound examination, artificial insemination and the expense of procuring, housing and preparing the recipient mare. Stallion fees, transportation of semen, registration, blood typing and other such processes are the responsibility of the owner. Board fees for the donor mare vary with accommodations. Paddock board with 3-4 other horses or stall board are each $27.00 per day, while mare and foal board is $29.00 per day.

When the recipient mare reaches 30 days gestation with a viable pregnancy, the owner leases her for $4,350. Board and care for the recipient mare are the responsibility of the owner, who is encouraged to pick her up at this time. Board for the recipient mare at 30 days is $21.00 per day, from 60-90 days $23.00 per day and $25.00 per day past 90 days.