Embryo transfer is exactly that: the transfer of an embryo from one mare to another. For this, the mare to be bred (the recipient) is required, as is a donor mare. This process allows mares who cannot carry a foal, or who are competing to produce progeny.
- Allows the mare to produce progeny while continuoing work
- Allows mares who cannot carry a foal to term (‘subfertile’) to produce progeny
- More than one foal can be produced during the breeding season
- Some studbooks (such as the thoroughbred industry) does not recognize embryo-transfer foals
- The procedure is expensive
The mares must be at the same stage in the oestrus cycle. This is achieved with ovulation inducing, and inhibiting drugs. Once the cycles are within an acceptable frame, the donor mare is artificially inseminated/ covered and scanned to ensure she is in foal. The embryo is harvested from the donor mare at the age of 7 days, and implanted into the recipient mare. During the process, both mares will (probably) be sedated, as excessive movement during the process could have a detrimental effect on the results. At this point, the embryo is at the blastocyst stage, with a diameter of only ¼ mm! The process of implantation is not easy, the donor must be flushed, and the fluid examined to find the embryo, which is then transplanted into the recipient. Not all flushes yield an embryo, this may be because the mare has lost the pregnancy, or the fluid did not flush the uterus properly.