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R E P R O D U C T I O N
W
hy is it that some mares appear to fall pregnant very easily and
others don’t
?
How is it possible that your mare is pregnant at her
21 day scan but not a week later
?
What causes a mare to abort at 8
months despite being apparently healthy on the outside
?
This article aims
to give a few answers to these questions, although, unfortunately, the
reproductive science of horses is not an exact one.
Veterinary Surgeon
Louise Cornish
Binscarth Farms
IN MARES
INFERTILITY
Mares fail to become pregnant for many
reasons, some of the most common being:
l
Poor timing of breeding
- either too early
or too late.
l
Poor quality of semen
- especially if
chilled or frozen for artificial insemination.
l
Age of the mare
- older eggs are of
poorer quality, and the uterine lining can
become scarred with age, even in a
maiden mare.
l
Malnutrition or obesity
- mares should be
lean and receiving good quality feeding.
l
Endometritis
- inflammation within the
lining of the womb, which may be either
present long-term due to infection or
brought on by semen irritating the
endometrium after breeding.
l
Infectious disease,
such as Contagious
Equine Metritis (CEM) or Equine Viral
Arteritis (EVA).
It is important to remember the pregnancy
rates which exist, even when conditions for
breeding are ideal. Approximately 60% of
young, healthy mares which are provided
with fresh good quality semen conceive on
their first service or covering. So, say you start
with 100 mares, 40 are left empty. At the
next attempt, 60% of these 40 are likely to
conceive, leaving 16 not in foal. If a third
attempt is made, statistically 6 mares are
likely not to be pregnant. By this time, there
should be strong suspicions that something is
going wrong with the stallion, mare or
covering/insemination regime, but you may
simply be unlucky enough to have one of
the 6 mares in our scenario which have
happened not to conceive!
XLVets Practice
Clyde Veterinary Group,
Lanarkshire
INFERTILITY
&
ABORTION
Louise Cornish BVMS, CertEP, MRCVS
Clyde Veterinary Group
3
EQUINE MATTERS
POSSIBLE VETERINARY
INVESTIGATIONS:
l
Vaginal examination
l
Clitoral or uterine swabbing
l
Ultrasonographic examination
l
Endoscopic examination
l
Uterine biopsy
l
Blood sampling
Ultrasound of a 15 day pregnancy