Equine Embryo Transfer

By: Margaret Ross

Adapted from: Embryo Transfer in Mares. Fred M. Hopkins, Professor, Large Animal Clinical Sciences, College of Veterinary Medicine and Animal Science; Doyle G. Meadows, Professor, Animal Science

Embryo transfer, also known as ET, is a reproductive technology that has various uses in the equine reproductive industry. These uses include:

·      Mares under 2 years old can have offspring

·      Show mares can have offspring without being removed from the show ring

·      Mares that are less fertile can have offspring

Embryo transfer has lots of advantages and well as disadvantages, including that it is a technical and time-consuming procedure that doesn’t always have a very high success rate. To add, some breed registries have restrictions for ET use. Each registry has different rules and registrations regarding embryo transfer.

When selecting a donor mare, one should look for a successful reproductive history and the mare should be gaining weight with a moderate body condition score. They should also be experiencing normal heat cycles and have a physical examination conducted to be sure they are in good health.

Recipient mares should be les than 10 years old and also be in good physical condition. They should also be prepared for the transfer dependent upon if they are intact or if they have had their ovaries removed. Intact mares can either be teased to determine heat cycle stage or they have their estrous cycle manipulated by giving hormones to synchronize their cycles. Mares without their ovaries have a different protocol that includes administering hormones. See the full article for more information.

Seven days after ovulation, the donor mare is collected. Only 1-2 embryos are typically collected, since horses cannot be superovulated like cows. Usually in healthy mares, an embryo is actually found in 50 to 80 percent of attempts.

Surgical implantation or nonsurgical methods are options for placing the embryos in the recipient mare. Most horse embryos are transferred by the nonsurgical option using an embryo transfer gun. The rates for recipient mares implanted with embryos determined to be of good quality range from 40 to 70 percent.

See full article here.