Refers to the transfer of embryos from a donor mare to a recipient mare, which can allow for more foals.

The donor mare refers to the mare that will be providing the eggs. The recipient mare refers to the mare that will carry the pregnancy but not be genetically related to the foal.

Embryo transfer usually involves the donor mare being impregnated and then the embryo being removed and implanted in a recipient mare who will carry the pregnancy to term. The embryo recovery rate is usually around 70% and the removal procedure is well-tolerated and minimally invasive.

The procedure is called a transcervical uterine lavage. A Y-tubing connects a uterine lavage catheter to a bag of special flush medium and a cup containing an embryo filter. The flush medium is then passed through the cervix and the embryo is removed and caught in the filter. The embryo is then collected and placed in the recipient mare.

Choosing a Recipient Mare

The recipient mare should be similar proportionally to the donor mare, about the same height and weight and be well-socialised. This ensures that the foal is not cramped in the womb or left with too much room causing developmental problems. The recipient mare should be well-socialised as she will be raising the foal from its early days and the foal will pick up on her manners and behaviours.

The most important aspect is that the donor mare and the recipient mare and cycling at the same or a very similar time. In the case of embryo transfer, it is recommended to have multiple options for recipient mares in order to ensure that they are cycling as close as possible in order to increase the viability of the pregnancy.

In terms of finding a recipient mare, there are studs that offer that service, and once the mare is confirmed pregnant, you oversee her care and the birth. If you have your own recipient mare that you wish to impregnate, you would have to ensure that both mares are cycling at the same time and that the recipient mare is a suitable candidate for carrying the foal from the donor mare.

Alternatives

Usually the mare is impregnated and then the fertilised egg (embryo) is collected and implanted in the recipient mare. Sometimes the mare can be super ovulated, using hormones to stimulate multiple follicles and cause her to release multiple eggs. This can increase the chance of embryo collection and fertilisation.

If either the mare or stallion has a history of low fertility, ICSI (Intracytoplasmic Sperm Injection) can be used. It is a specialised form of IVF (In-Vitro Fertilisation) that involves the injection of one singular sperm into the egg. Once the egg is confirmed to be fertilised, it can implanted into the recipient mare.

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