British Breeder Magazine May 2020

Article - VET INSIGHT
The donor mare is inseminated and just
over a week later her uterus is flushed
with an embryo flushing media. The
fluid is searched for an embryo in a
pre-prepared laboratory. Hygiene
and embryo preservation are the most
important considerations. The embryo is
then frozen or transferred into a suitable,
pre-synchronised recipient mare.
The recipient may be located where
the donor is flushed or the embryo
can be chilled and transported to a
recipient herd elsewhere. It is possible to
synchronise only one recipient per donor
ovulation, but it is strongly advisable
to synchronise 2-3 recipient mares per
possible embryo, as the synchrony
process is not failsafe. Sometimes it is
not possible to synchronise a recipient
for a particular donor cycle due to the
following:
• Timing/asymmetric response to
drugs given.
• Recipient having an undesirable
uterus on the day of transfer,
therefore a second recipient is
needed.
Successful synchronisation requires
skilled veterinary expertise, regular
scanning of both donor and recipients
and a high level of communication
between the vets scanning the donor
& recipients. The synchrony process
should start as soon as the donor is first
scanned - drugs such as prostaglandins/
ovulation induction agents should never
be given to the donor before checking
that the recipient synchrony is on track.
It is a wasted investment producing an
embryo without a suitable recipient’s
uterus to transfer to. The perfect recipient
requires:
• Manageable temperament
• Similar size to donor
• Healthy – including up to date
vaccinations and worming
• Reproductively sound
On going care of the recipient is
essential throughout the pregnancy and
nursing as with any broodmare. Regular
scanning of the pregnancy ensures all is
progressing to plan and no veterinary
intervention is required.
The risks of AI and ET are mainly with
the known risk of a potentially fatal
rectal tear during rectal examination
and scanning. This risk is minimised
by competent reproduction vets and
their use of sedative drugs and rectal
relaxant drugs if necessary as well as
ensuring rectal examinations are carried
out in stocks. Whilst ET is successful in
many candidates, some mares are more
complex and may require a different
approach to secure a pregnancy. Other
methods can include:
Ovum Pick Up (OPU) &
Intra-Cytoplasmic Sperm Injection
(ICSI): In a natural pregnancy the
oocyte (released from the ovary during
ovulation) is fertilised by a sperm in
the oviduct, then the resultant embryo
drops into the uterus. In mares who
suffer with chronic uterus problems or
an oviduct abnormality, OPU/ICSI is
a good option. OPU is done at a clinic
were the mare is sedated and involves
oocytes being retrieved directly from the
ovaries. The oocytes are then sent to an
ICSI lab where they undergo a specialist
IVF procedure involving a single sperm
being injected into the oocyte followed
by a period of embryo development. The
embryo can be frozen for transfer at a
later date, or transferred directly into a
recipient.
The donor is scanned prior to OPU to
ensure she has at least 15 follicles across
both ovaries. The procedure involves a
trans-vaginal scanning method to access
the ovaries and aspirate each viable
follicle to recover an oocyte. The oocyte
recovery rate per follicle is around 50-
60% and usually requires 6-8 oocytes
to successfully produce an embryo using
ICSI. It may not be possible to secure
an an embryo from each OPU session,
it is important to factor in around 2 OPU
sessions (repeatable at 2 week intervals)
for each embryo you want to achieve.
OPU doesn’t require multiple scanning
sessions or AI & Uterine Flushings, but
instead a quick day-case procedure.
Many deceased stallions with limited
stores of frozen semen are now only
available for ICSI produced breedings.
OPU/ICSI can also be performed on
a mare immediately post mortem - if
a valuable mare dies unexpectedly
and the owner wishes to preserve her
bloodlines, then provided the oocytes
are retrieved immediately, it is possible to
produce embryos in the lab.
Cloning is becoming a much more
viable option in terms of success rates,
availability and cost. To clone a horse,
stem cells need to be harvested from the
donor using a simple, minimally invasive
procedure under sedation. These stem
cells are processed in a specialist lab to
produce viable cell lines suitable for use
in the cloning process. These cell lines
can be frozen for use at a later date or
sent immediately to a cloning laboratory
to undergo the cloning process to
produce an embryo. This embryo is then
transferred to a recipient.
Cost is always an important
consideration. It is difficult to accurately
quote since the breeding process for
each horse is different. However it is
useful to assess different sections:
pre-breeding testing, stallion costs,
embryo production, pregnancy
production, pregnancy maintenance,
and foaling. Pre-Breeding testing
costs can vary depending on the stud
requirements and also whether export
testing is needed. As an estimated figure
expect to pay £100 - £300. Stallion
costs and terms vary hugely between
industries, individual stallions and semen
type. Costs need to be established with
the stallion owner/agent. There are also
mare (NC) & semen (AI) transport cost
considerations. A cost guide:
Embryo production
• NC £175 - £250
• AI £200 - £400
Depending on semen type. Treatments
and uterine lavages are usually charged
in addition.
• OPU £750 - £1000 per session
Drugs and oocyte shipping costs
charged in addition
• ICSI £400 - £800 per session
• Cloning £60,000 - £120,000
Priced based on a live guaranteed foal
& includes recipient hire. Price depends
on lab used.
Pregnancy production
• Broodmare NC/AI – no additional
costs
• Embryo Transfer (ET, OPU & ICSI)
£1800 – 3600
Includes Transfer of the Embryo,
Recipient Synchrony & Hire. Shipping &
Health Certification is extra.
Pregnancy maintenance & foaling
• Prices are the same for all
reproduction methods. Cost
varies depending on pregnancy
complications necessitating
treatment and whether the mare is
kept at home with the owner or at
a stud.
Emma Tomlinson MA VetMB MRCVS
Copyright @TomlinsonEquineVets2020
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