Page 8 - Equine Matters - Spring 2014

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7
EQUINE MATTERS
What is embryo transfer?
Embryo transfer is the procedure by which an
embryo is removed from the uterus of a donor
mare and placed into the uterus of a recipient
mare. The recipient mare then carries the
pregnancy through to foaling.
What does the procedure
involve?
The procedure for embryo transfer starts with
insemination of the donor mare; this can be
done by natural covering or with chilled or
frozen semen via artificial insemination. On
day 7 or 8 after insemination the embryo is
flushed out of the donor mare’s uterus and
transferred to the recipient mare. This 'flushing'
involves the introduction of a catheter through
the cervix and concurrent manipulation of the
uterus rectally. The transfer into the recipient
mare can be carried out surgically or
non-surgically. Non-surgical transfer involves
the placement of the embryo into the recipient
mare through the cervix into the uterine body.
Surgical transfer is carried out standing under
sedation and an incision made into the
abdomen via the flank; one horn of the uterus
is located and a small puncture made to
allow insertion of the embryo; the incisions
are closed and box rest for 5-7 days is
often instigated to monitor general health
and the incision site. In the past, higher
success rates with surgical transfer had
been reported but this is no longer the case
and non-surgical transfer has the advantages
of reduced expense and less post-transfer
complications.
How successful is embryo
transfer?
Reports are variable and there are a number
of factors affecting the success rate of embryo
transfer; these include the fertility of the donor
and recipient mare, the stallion used and
the experience of the personnel involved.
Reported embryo recovery rates vary between
50 - 70% and pregnancy rates between
60 - 80%. Pregnancy rates will fall if the
fertility of the donor/recipient/stallion is poor,
the staff involved are inexperienced and the
ovulation is not timed well between the donor
and recipient.
EMBRYO TRANSFER
Lee Pritchard BVSc MRCVS
Calweton Veterinary Group
Embryo transfer
Embryo transfer, although first reported in mares as early as the
1970's has only become routine over the past decade as its
popularity has increased. It is now widely accepted by a number
of studbooks in the UK (with the exception of Weatherby's).
l
The first
is for those mares that are
competing at a high level, providing
a means of breeding foals from these
elite mares without affecting their
competitive careers or starting their
reproductive career at a later age
when fertility is generally reduced.
l
The second
is for those mares that
have a medical condition that would
put the mare, the foal or both at risk
by carrying a foal to term. In some
cases it can allow mares to produce
more than one foal in a season.
Embryo transfer is most often
used for two reasons:
Embryo transfer is continuing to grow
in popularity in the UK and has the
potential to improve reproductive
performance in mares.
For more information on this or other
reproductive techniques contact your
XLVets Equine practice for more details.
Conclusion
Veterinary Surgeon
Lee Pritchard
XLVets Equine Practice
Calweton Veterinary
Group