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SPRING 2014 ISSUE
EQUINE MATTERS
6
THE PROB L EM MARE
Prior to covering/insemination:
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swabs and smears to identify venereal
disease and endometritis;
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ultrasound to detect free fluid in the
uterus (treated with prostaglandin
and/or oxytocin injections);
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bacterial contamination additionally
requires lavage of the uterus with saline
or antibiotic solution.
Prolonged spring transition
Most mares' ovaries become dormant for
a variable period of 3-8 months during the
winter, and early in the stud season may
not have commenced normal cyclical
activity. The change from non-cycling to
cycling ovaries is called the transition
phase and during this time mares typically
have prolonged but weak signs of being
in season and these seasons are often not
associated with the release of eggs.
The use of artificial lighting, a rising plane
of nutrition and the use of hormone
treatment can hasten the onset of cycling.
Ovarian tumour
An ovarian tumour called a granulosa
cell tumour can prevent normal cycling. In
some cases mares show persistent oestrus
(in season) or stallion-like behaviour but do
not ovulate or become pregnant. These
can be suspected on rectal ultrasound scan
examination and confirmed with a blood
sample for hormone analysis. Following
the surgical removal of the affected ovary,
the mare will usually resume normal
cycling on the remaining ovary.
At covering/insemination:
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single correctly timed mating or
preferably AI;
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repeated examinations and the use
of an injection to stimulate ovulation
at a fixed time will assist with the
correct timing;
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AI reduces the quantity of fluid and
bacteria introduced to the uterus.
Susceptible mares should
be treated as follows:
Following covering/insemination:
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ultrasound scans to detect the presence
of fluid in the uterus and assess
response to treatment;
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treatment with antibiotics, lavage and
repeated oxytocin injections.
Fertilisation takes place in the oviduct and
the fertilised embryo does not descend
into the uterus until day four to six. There
is therefore a four day window following
ovulation in which the uterus can be
treated in order to optimise the conditions
for the development of the pregnancy.
Older mares that have had foals previously
often develop cysts in the lining of the
uterus, these can sometimes be confused
with an early pregnancy so it is important
that they are charted and measured and
monitored closely. In large numbers,
cysts may affect fertility by impeding the
movement of the early pregnancy and
reducing the area for attachment of the
placenta. Large cysts can be treated using
laser surgery.
Chronic or repeated endometritis can
lead to degenerative changes in the uterine
lining known as endometriosis. Diagnosis
is made using a uterine biopsy and the
prognosis for future breeding is poor.
Endometrial cysts
Abnormal cycling
Chromosomal abnormalities
Rarely some mares never develop functional
ovaries due to genetic/chromosomal
abnormalities.
Other causes of
fertility problems
Venereal disease screening (involving the
collection and testing of swabs and blood
samples) of mares and stallions should
always be performed prior to any breeding
activities. This will rule out important and
highly infectious causes of infertility. Most
reputable studs will have a strict policy in
place and this is encouraged by the
veterinary profession.
Venereal disease
Investigation of problem
mares include:
l
examination of vulva, vagina and
cervix (with aid of a speculum);
Optimise fertility:
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arrange a pre-breeding examination
including swabs and blood tests to
detect any potential problems and rule
out infectious disease;
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arrange for an ultrasound examination
of the uterus following service/
insemination to allow detection and
treatment of endometritis.
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correct any conformational abnormalities
e.g. using Caslick's sutures;
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begin in April or May with mare in lean
body condition on good grass;
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use a single carefully timed service or
preferably artificial insemination;
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manual and ultrasound evaluation of
reproductive tract;
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biopsy of endometrium;
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endoscopic examination of uterus;
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blood sampling for hormone profiling.
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avoid the foal heat;
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culture and cytology of endometrial
swabs for bacteria/fungi and
inflammatory cells;
A speculum allows a visual assessment of
the cervix - an important seal that protects
the uterus
Rectal ultrasound examination is a vital part
of investigation and management of the
problem mare