Over the last two decades, embryo transfer has grown in acceptance and is now performed in many horse breeds. The majority
of embryo transfers in the United States each year are performed on Arabian and Quarter horses. The American Quarter Horse
Association allows multiple foal registrations per year, and the high-dollar Quarter horses are boosting the embryo transfer
industry. The embryo transfer technique has not undergone significant innovations for the past few years, but there has been
an increasing trend to have embryos shipped to a reproductive facility that manages a large recipient herd. This trend has
been supported by encouraging pregnancy rates following embryo transfers from shipped embryos.
Choosing a mare
Choosing a recipient mare is critical to any embryo transfer program. The availability of a reliable reproductive facility
is helpful in the selection process, considering that most of these facilities have more than 250 mares available each year.
The mares used are usually cycling mares; however, ovariectomized and progesterone-treated mares also can be used. The recipient
mare must be 100 percent reproductively sound and preferably be young (younger than 10 years old). When using cycling mares,
the recipient should ovulate a day prior, the same day or up to three days after the donor mare.
Table 1 Recipient mare fees
Ovulation timing is just the first step in the selection process. The recipient mare must meet some criteria prior to the
transfer. The cervical tone and uterine tone determined just prior to the transfer of the embryo is very important to ensure
a high pregnancy rate (Carnevale et al, 2000). The presence of a good corpus luteum and the absence of fluid and endometrial
folds are additional factors to be evaluated. If the recipient mare fails to meet all of the criteria, she will be omitted
for that particular cycle and another mare will be selected for the transfer.
Keeping a small recipient herd on hand to serve a small number of clients can be costly and time consuming — not to mention
the stress of not having the right recipient mare when needed.
Table 2 25-day pregnancy rate comparisons
One of the deciding cost factors is that for each donor mare it is necessary to have two or more recipient mares available.
Handling the recipient mare herd daily with constant checkups means spending valuable time during the already busy breeding
The recipient mares not used that year will require some upkeep until the following year. The mare maintenance can be translated
into a few extra dollars if the location is in a cold climate where supplemental feeding becomes necessary throughout the
It is not uncommon for clients to believe that any mare, such as an older riding horse, is suitable as a recipient mare. One
should never choose a recipient mare based solely on sentimental value. All mares have to be screened in-depth before they
are included in a recipient program, to ensure the success of the transfer and to eliminate wasting time. Using a large recipient
mare herd from a reproductive facility will provide peace of mind since good recipient mares will always be available. Clients
should be instructed in the importance of the recipient mare selection as well as the reasons for the price. As a result,
your embryo transfer program can become successful.