Equine Embryo Transfer


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.



  • ·   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

1.    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 recommend collecting and packing the embryo and sending to a reproduction centre that has an extremely large recipient herd.

2.    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.

3.    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 medium ready for sending.

     If clients want to use their own recipients it is possible if at least five mares are available. The more mares the greater the chance of getting a suitable recipient.

4.    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 60%. A survival rate of 60 % of good quality embryos recovered typically occurs following transfer.  This gives a 40% success rate per cycle and therefore it is recommended that you are prepared for at least 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.




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