Horse embryo transfer (ET) mare breeding

Equine embryo transfer (ET) explained.

Horse embryo transfer (ET) is the process of flushing an embryo from the uterus of a genetically superior donor mare and transferring it to a healthy recipient mare. Some of the advantages of equine embryo transfer (ET) are:

  • Donor mares can carry on competing - the genetic mother does not have to take time out from her competition career to have a foal. Embryos can be flushed while the mare is in the process of competing; this can also give a reduced generation gap, as mares can start an embryo transfer program at the age of two, before starting to compete.
  • More than one foal per year can be produced by the same mare - hence giving the opportunity to try different stallions, and also maximizing the breeding potential of an extremely talented horse.
  • Allows breeding of mares when reproduction would not be possible otherwise - for example those who suffer from repeated early embryonic loss, or have a broken pelvis, or for some other reason are unable to carry a foal to term - embryo transfer is the obvious way in which they can continue to reproduce.

What is the process of embryo transfer (ET)?

Initially, the donor mare is inseminated and conceives an embryo. At the same time, several recipient mares are synchronized, so that their cycles closely mirror that of the donor mare.

At eight days post ovulation the donor mare is flushed and the embryo retrieved ready for transfer. Relatively simple and unobtrusive, the flush involves a lavage of the uterus with a specially designed fluid. The fluid is allowed to flow out over a filter, on which the embryo comes to rest.

The embryo is carefully examined and transferred to a holding fluid which is used to transfer the embryo in to the uterus of a recipient mare, which is subsequently scanned approximately a week later for pregnancy.


Likely results from embryo transfer:

Results of embryo transfers vary depending on many factors - the age of the mare, the fertility of the stallion, the management of the recipients etc., but generally we have an embryo transfer success rate above 88%.

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