Embryo Transfer ( ET )

What is this ?

                              Equine Embryo Transfer Technology

Embryo transfer is a technique where a 6-8 day old embryo is flushed from the uterus of a donor mare and is then transferred into a recipient mare or frozen to be transferred at a later date. The production of foals using embryo transfer (ET) is commonplace  but is limited to a very small number of horses, creating little or no impact or genetic gain. One factor limiting the wide-spread use of ET in horses is cost. Another is the lack of commercially available embryos for sale. In cattle, ET is used extensively and creates significant economic and genetic gain for the industry. The acceptance of ET in cattle came about after embryos could be frozen, and more importantly when the evolving technology became simpler, more reliable and inexpensive, allowing technicians and farmers to transfer these embryos successfully into recipient cows.
 

Advantages of ET:

ET enables the embryo donor mare to continue her competition career while the recipient mare carries the pregnancy to term.
It is possible to obtain more than one pregnancy per year from a mare. You may choose to inseminate your mare with the same stallion each time or use different sires for each estrous cycle. We usually recommend that you aim for 1 – 3 pregnancies from each donor mare each season.
If you have a mare with an old, sub-fertile uterus who is prone to losing pregnancies after 15 days then it is beneficial to transfer her embryo into a healthy uterus of a younger mare.
The fertility of an embryo transfer programme is similar to a normal breeding programme.
The whole procedure is non-surgical
There is no increased risk of embryo loss or birth defects from ET foals than from foals in the normal population.
New embryo freezing technologies enable the achievement of satisfactory pregnancy rates from frozen-thawed embryos.

Cost of Producing a Foal :

Breeding a mare can be an expensive proposition. The cost of producing a foal depends on the initial value of the donor mare, and therefore her yearly depreciation. Additional costs are the cost of maintaining the mare, veterinary costs, semen costs, etc. By using embryo transfer (ET), the costs of maintaining recipient mares must be added; the fertility of the stallion, the success to obtain the embryo and achieve a pregnancy  influence the final cost.
The main cost of producing a foal comes from the depreciation of the dam. Embryo transfer allows a mare to produce more foals per year and therefore reduces the per-foal depreciation cost. The second most important cost of producing pregnancies using ET comes from the maintenance of suitable recipient mares before transfer. At least three recipient mares have to be available per donor mare, so at the time of transfer one will be in good reproductive synchrony with the donor mare. New technology has enabled the freezing of horse embryos so now one need to have fewer recipient mares, reducing the overall cost. The cost of semen, is low in comparison to all the other expenses. This shows that only the best stallions must be used, even if they are more expensive.
 

Although foals born after embryo transfer are eligible for registration in the majority of horse breeds, application of embryo transfer is still rare. This is mainly due to the lack of a possibility for super-ovulation. Uterine stage embryos can be recovered by a non-surgical flushing technique. Transfer can be accomplished by non-surgical as well as surgical methods. In contrast to the situation in cattle, most related technologies are scarcely available. Methods of cryo-preservation as well as bisection of embryos are hampered by the fact that suitable embryos (morula) can be collected from the uterus only during a very short period. In vitro production of embryos by in vitro maturation, fertilization and embryo culture is currently under investigation. Progress has been made to establish ultrasound-guided trans-vaginal ocyte aspiration. These techniques will provide an important stimulus for application of embryo transfer in equine species and enhance ones knowledge about reproductive biology in the mare.

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