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Embryo Transfer

Embryo Transfer is an assisted reproductive technique that involves breeding a donor mare

For the last 20 years, embryo transfer (ET) has become a popular breeding method for breeders of high-quality sport horses’, since the mares often spend their best breeding years competing.

Embryo Transfer is an assisted reproductive technique that involves breeding a donor mare. Instead of the mare carrying her own pregnancy, she undergoes a flush of the uterus 7 – 8 days post-ovulation to collect the embryo, which is transferred to a synchronized recipient (a surrogate mare) who will carry it to term. It is a simple, non-surgical, and well tolerated procedure.

 

Advantages:

  • Minimal disruption of the competition schedule.
  • Production of multiple offspring from one mare during one year (pregnancy length in horses is very long, average of 342 days (= 11 months).
  • Shortening of the generation interval by potentially obtaining embryos from 2-and 3-year-old fillies

 

What does influence the embryo recovery rate?

Even though it is a widely done procedure, the recovery rates expected are still 1 embryo per 3 flushes. This is mare-dependable and the factors that can influence are:

  • Donor mare age and fertility.
  • Donor mare reproductive history.
  • Number of ovulations.
  • Time of the flush.
  • Quality of the semen.

 

How to choose a recipient mare?

The synchronisation of the recipient mare with the donor mare plays a large part in the success rate. The recipient and donor mares must be synchronised and ideally a minimum of two recipients are required to ensure that if an embryo is retrieved from the donor mare, a suitable recipient mare is available. Ideally the recipient mare will ovulate 2 days after the donor.

The recipient mare is as important as the donor and stallion choice.

An ideal recipient:

  • Young (3 to 10 years old).
  • With good temperament and in good general health.
  • Cycling normally and show no obvious signs of reproductive pathology.

Q. What are the expected pregnancy rates after embryo transfer?

85-90% of the embryos transferred should result into a pregnancy.

Q. If my mare does not have good results with Embryo Transfer, what are my options?

Fortunately, new techniques have been developed and widely spread by the equine industry in order to overcome some of the ET limitations. Ovum Pick-Up (OPU) and Intracytoplasmatic Sperm Injection (ICSI) has acquired a good level of efficacy, and it is a flexible technique.

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