Dr. Chris Berezowski
DVM, DACT
Equine Embryo Transfer
What is Embryo Transfer (ET)?
Embryo transfer is a reproductive technique that involves the collection of an embryo
from a donor mare when the embryo is seven to eight days old. The embryo is then
transferred into a recipient (surrogate) mare where a pregnancy can be established
and carried to term.
What are the benefits of embryo transfer? One of the main benefits of embryo transfer is that it allows performance mares to have a foal while still
remaining in training/competition. Depending on the breed registry, multiple foals
from a single mare in a season is possible. Mares that are unable to carry a pregnancy
on their own due to physical or reproductive abnormalities can benefit as well.
Embryo transfer can maximize the number of foals produced from genetically superior
mares during their reproductive lifetime.
How is Embryo Transfer performed? Embryo transfer involves the use of a donor and recipient mares who must be synchronized
in their estrous (heat) cycles. Ideally, three recipient mares are needed for every
donor mare. This ensures that one of the recipient mares will match the donor mares
stage of the heat cycle. Both mares should be healthy, reproductively sound and
cycling regularly. The donor mare is bred normally (AI, live cover) with special
attention given to the time of ovulation and to ensure an excellent uterine environment.
Seven or eight days after the donor mare has ovulated her uterus is flushed to recover
the embryo. Several liters of flush media are warmed and infused into the uterus
through a catheter. The uterus is flushed three or four times and drained through
a filtered collection bottle. The collected embryo is washed to remove any contaminants
and evaluated for viability based on the size, grade, morphology and developmental
stage.
The second stage involves transferring the embryo to the recipient mare.
It is important that the recipient mare has ovulated no more than one day before
or two days after the donor mare. The embryo is placed in an insemination gun and
transferred into the uterus aided by rectal palpation. The initial pregnancy exam
of the recipient mare will be conducted 4 days after the transfer. What makes a
good recipient mare?
An ideal recipient mare should be less then 9 years old, be
of good physical/reproductive health and temperament. Moore and Company will have
a herd of high quality recipient mares available for your donor mare’s embryo or
you can provide your own suitable recipient mare.
What are the success rates? To maximize the success of embryo transfer it is important to use high quality semen
from fertile stallions. If the donor mare is pregnant, the embryo will be recovered
in over 95% of cases. Once an embryo is recovered, the transfer success rate is
dependent on the quality of the embryo. High quality embryos will result in pregnancy
in 70 to 80% of cases. Donor mares can also be flushed at a distant veterinary facility
with the embryo then shipped and transferred into one of our recipient mares with
only a slight reduction in pregnancy rates.
Embryo transfer is not a viable option
for all mares and we would be happy to discuss the best breeding options for your
mare. If you do decide to use this reproductive method, Moore and Company would
be happy to assist you in achieving your goal.
2006 Embryo Transfer Results
We are
proud to report that a pregnancy resulted from 84.6% of the embryos transferred
in 2006! |
