Embryo Transfer in Mares

February 15, 2010 (published)

Today on Texas Vet News I am going to talk about embryo transfer in mares.  Many of you may have mares from which you would like a foal but the mare has been unable to carry a pregnancy to term.  Or maybe the mare has severe arthritis, or maybe even has foundered and cannot carry a foal.  These mares can still have a foal by using embryo transfer.  In embryo transfer, the mare is bred and in about 7 to 8 days, the resultant embryo is flushed from the mare’s uterus and placed into another mare to carry the pregnancy.  The original mare is called the donor mare because she donates the embryo, and the mare that receives and carries the foal is called the recipient mare. 

Probably the most common reason for embryo transfer is mares that have chronic infections and thus cannot maintain a pregnancy to term.  If they can just get pregnant and keep the embryo alive in their uterus for 7 to 8 days, the embryo can be flushed out and placed in the recipient mare.  It is possible to recover embryos from mares with these chronic infections but it does require some work.  The goal is to improve the environment in the uterus for just a few days until the embryo can be transferred. The most important part of this is flushing the uterus with large volumes of sterile fluids.  Flushing the mare both before breeding and after removes infectious material and gives the embryo a better chance of survival.  Sometimes antibiotics and antifungal agents may also need to be used before breeding these mares.  If none of these techniques are effective, it is even possible to take an ova or egg from a donor mare and place it in recipient mare and then she is bred.

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