Embryo Transfer - Westvets Veterinary Practice

Embryo Transfer (ET)

Embryo Transfer (ET)

Embryo transfer is the process by which a very young embryo (7-8 days old) is flushed from the uterus of a valuable donor mare and recovered via filtration. The embryo is then transferred into the uterus of a recipient mare to complete development. The resultant foal will be the genetic offspring of the donor mare and stallion of your choice. The recipient mare will give birth to and raise the foal.

Advantages

Allows a valuable mare (donor) to continue a performance career while the recipient mare carries the foal
More than one pregnancy per year can be achieved from superior mares
Foals can be obtained from mares that cannot carry embryos beyond 15 days of pregnancy
Younger mares of 2 & 3 years of age can produce offspring
Obtain foals from mares foaling late in the breeding season thus enabling them to conceive early the following year

The ET Procedure

The first step of the program is to synchronize the reproductive cycles of the donor and recipient mares. It is important that the recipient mare is at a similar stage in her cycle as the donor mare to ensure that the uterus is ready to accept the embryo. We have a number of recipient mares to choose from which is ideal for this process.
The donor mare (your mare) is bred using semen of your choice. This can be fresh, chilled or frozen semen. It is necessary for the cycle of the mare to be followed closely using ultrasound examination and the breeding timed according to these findings. It is important that the time of ovulation is known.
7 or 8 days following the detection of ovulation, a sterile catheter is placed in the uterus of the donor mare and the embryo removed by flushing a special fluid into the uterus. The recovered fluid passes through a filter allowing the microscopic embryo to be retrieved. The embryo is then assessed and graded according to its appearance and is placed in a catheter ready to be transferred.
A pregnancy scan is performed on the recipient mare 6-7 days following the transfer of the embryo.

Success Rates

The most important factors that affect the recovery rate of embryos are the timing of the insemination and the fertility of the donor mare and stallion. Stallion fertility is further influenced by semen dose, quality, and method of preservation. In young, healthy mares with no history of reproductive problems inseminated with fresh semen from fertile stallions, typical embryo recovery rates near 80%. A survival rate of 75-80 % of good quality embryos recovered typically occurs following transfer. This gives a 60-65% success rate per cycle and therefore it is recommended that you are prepared for 2 cycles per pregnancy from young fertile mares inseminated with fertile fresh semen. A reduced embryo recovery rate occurs when aged mares (greater than 14 years), or those with a history of subfertility are used as donors, or when chilled, or in particular, frozen semen is used.

Transported Embryos

We can manage your mare from insemination to transfer – or you can manage your own breeding with your vet and send either your mare to us for the flush and transfer procedure or the chilled embryo for transfer into one of our recipient mares. This requires very close communication between all parties involved.