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WHAT CAN I DO TO
REDUCE THE LIKELIHOOD
OF MY MARE ABORTING?
R E P R O D U C T I O N
SPRING 2011 ISSUE
EQUINE MATTERS
4
EMBRYONIC OR FOETAL LOSS
Unfortunately, loss of a developing foal is not
uncommon, especially at the early stages of
pregnancy. If the embryo dies before 80
days of age, it will probably be resorbed
by the uterus (womb) of the mare, and no
outward signs of abortion will be present.
After 80 days, the foetus and placenta will
usually be expelled via the vagina. There
may or may not be any traces of the abortion
having taken place, depending on the
amount of blood or discharge present and
the management of the mare. It is, therefore,
relatively common for a vet to be called
to examine a mare which is overdue for
foaling, only to discover that she is no
longer pregnant despite a positive scan the
previous spring.
An aborting foal can be dangerous for a
mare, especially in the last few months of
pregnancy, as the foal may not present in the
normal position. It is also very common for
the placenta not to be passed as normal,
resulting in Retained Foetal Membranes
(RFM), which can quickly lead to toxaemia
and laminitis.
Causes of embryonic or foetal loss include:
l
Abnormal genetics
- the womb of a mare
may ‘recognise’ abnormal chromosomes
in a young embryo and terminate the
pregnancy.
l
A poor uterine environment
- multiple
large endometrial cysts, uterine infection
or scarring prevent a 17 day old embryo
from successfully implanting into the wall
of the womb.
l
Fixation in the wrong part of the
uterus
- such as in the horn tips or in
the uterine body.
l
Severe stress, trauma or malnutrition
-
fairly uncommon causes in reality -
although often blamed.
l
Pyrexia (fever) in the mare due to an
unrelated infection
- such as influenza
or strangles.
l
Insufficient amounts of progesterone
-
there is little evidence to suggest that poor
production of this hormone by the ovaries
is a common cause of miscarriage, but
oral supplementation with a synthetic
equivalent is sometimes recommended,
especially if a blood sample has shown
low progesterone levels.
l
Placentitis
- bacterial infection of the
placenta usually develops due to infection
creeping up through the cervix from the
vagina, especially in the later stages
of pregnancy.
l
Twins
- a mare’s uterus has evolved to
carry only one foal to term, and less than
5% of twin pregnancies will result in two
live foals. Of the other 95%, many will
safely lose one embryo very early on in
the pregnancy, but about a third of mares
will abort both foals in the last trimester.
This is distressing for all concerned, as
well as being dangerous for the mare,
as difficult births and RFM are common.
l
Equine Herpes Virus (EHV-1)
- this virus
causes respiratory disease and is often
referred to as ‘the cold’ in equine circles,
but also causes abortion in the second
half of pregnancy in mares.
l
Equine Viral Arteritis (EVA)
- this virus
is not normally present in the UK but is
occasionally found in imported mares or
stallions and is notifiable. A vaccine is
available for use in stallions but must be
obtained under licence.
l
Arrange a pre-breeding check from
your vet to pick up abnormalities that
can be addressed before conception
l
Two ultrasonographic scans before
35 days gestation to detect twins
l
Provide good quality nutrition but
avoid too much weight gain
l
Encourage regular but not excessive
exercise
l
Ensure she has a relatively stress-free
and hygienic environment
l
Keep brood mares separate from
horses that are regularly travelling to
competitions/riding club
l
Vaccinate for EHV-1 at 5, 7 & 9
months of pregnancy
If you do suspect that your mare has lost
a foal, it is highly recommended that
your vet examines the mare for her own
safety. If you do find the foal and/or
afterbirth, keep them so that your vet
can examine them too - it may be
possible to make a diagnosis as to the
cause of the abortion, or they may be
sent to a laboratory for further tests. This
is especially important if there are other
pregnant mares on the premises.
Depending on the cause of the loss,
your vet may be able to advise you
as to whether it would be wise to
attempt to breed the mare again on
another occasion.
IF YOU SUSPECT THAT
YOUR MARE HAS LOST
A FOAL...
Ultrasound of a 40 day pregnancy