EMBRYO TRANSFER

Prep Work: 

Preparing for ET involves synchronizing a donor mare (the mare you want a foal from) with a recipient “recip” mare (the mare that is going to carry the foal). Oftentimes artificial means are used such as lighting and hormonal drugs to synchronize the mare’s heat cycles. For the ET to be timed correctly, the recipient mare must ovulate within a day or two of the donor mare. This requires frequent ultrasounds and very close monitoring of both mares. 

Embryo Transfer Process: 

This process is usually done on day 7-8 post ovulation of the donor mare. It consists of flushing the donor mare’s uterus into a filter that catches the embryo. If an embryo is found, it will be examined under a microscope, processed and washed clean of the donor mare cells, and implanted into a recipient mare. Under protocol, the recipient mare will receive a combination of drugs that will encourage her body not to reject the new “foreign” object we have put into her uterus. After day 8, the transfer success rate drops dramatically due to the embryo becoming large and fragile and the recipient mare’s uterus beginning to produce hormones to restart her heat cycle. 

Post ET: 

If the transfer is successful and you would like to breed the donor mare again, either for another ET or to have her carry a foal, she can be given shot that will help bring her back into heat in the next 5-7 days, or let her come back in naturally, which can take 2+ weeks. You will also be checking the recipient mare day 14 after ovulation (day 6-7 post transfer) to see if there is a viable pregnancy. It is recommended to put the recipient mare on Regumate (artificial progesterone) until at least 2 months. Pregnancy loss rates are higher <50 days. 

If the transfer is unsuccessful and you do not recover an embryo you have two options: First, you can short cycle both mares (donor & recipient) and try again, or you can wait another 6-7 days and check your donor mare to see if she is pregnant. Sometimes, the embryo remains in the uterus of the donor mare no matter how many times it is flushed. This is a viable option for donor mares able to carry. 

As always we recommend you make decisions while working closely with your vet. We will assist as much as we can!