- What
is a problem mare ?
- How
do we treat the problem mare ?
- When
should I examine my mare for pregnancy ?
- At
what age can I breed my colt ?
- Do
I need to culture my mare prior to breeding ?
- What
happens if my mare has twins ?
- If
I freeze semen, how long will it keep ?
- I
have a 10 year old maiden mare that can not get pregnant.
If she is a maiden why is she having difficulty?
A mare should be regarded as a potential problem if
she fails to conceive to a fertile stallion on a well
managed breeding farm on three or more cycles in one season. There are
many reasons mares may become problems. For example,
mares failing to exhibit oestrus in the breeding season
may have a granulosa theca cell tumour, gonadal dysgenesis,
pituitary adenoma, or they may be pseudopregnant, unknowingly
pregnant, or in anoestrus. However, by far the most
common type of problem mare presented are mares with
persistent, unidentified or inappropriately treated
uterine infections. Examination of a problem mare should
include most of the following:
History-The
prognosis for mares barren 3 years or more is always
guarded provided they come from well managed breeding
farms. Regardless of the number of years barren, we
have more success in mares less than 18 years old.
Physical
Condition-Body condition is related to timing and recrudescence to cyclicity,
while disease and chronic pain affect the ability of
mares to maintain a pregnancy.
Mare
with a right front broken leg. Due to her genetic merit
this mare was bred but lost 4 pregnancies in one year
possible due to chronic pain. This mare was used as an embryo
donor.
External
Perineal Conformation-Height of pelvis relative to anal slope of vaginal lips,
abnormalities of perineal body, clitoris or labia, presence
or need to modify a Caslick, and propensity to aspirate
air or pool urine are all noted with suggestions for
methods of improvement and necessity.
Age
as well as multiple pregnancies result in the loss of
muscle tone in the perineum. These mares become prone
to fecal contamination in the reproductive tract.
Rectal Examination-The main purpose
of rectal examination is assessment of structure, tone
and form. It is not possible to routinely determine the
presence of uterine fluid with rectal palpation. Ovarian
examination gives important information on cyclicity and
ovarian abnormalities. Ultrasonographic Examination-Quantity and quality
of uterine fluid are related to degree of inflammation.
Uterine cysts are related to age and chronic endometritis.
Abnormalities detected and undetected by rectal examination
are visualized.
Ultrasound of a the
uterus of a normal mare showing signs of heat. The white
line demarks
an individual Endometrial fold. On the right a 42 mm
follicle.
Ultrasound
of the uterus of a mare showings signs of uterine inflammation
due to a possible infection.
Vaginal
Examination-Manual examination is recommended. The vestibular sphincter
and cervix are assessed for efficacy as barriers to
infection. Cervical defects and adhesions are not uncommon.
Some cervical defects are best recognized during diestrus
Culture-Guarded
culture techniques from mares in heat are recommended
Samples are cultured aerobically for 72 hours. Fungal
culture techniques are used when indicated Culture of
uterine biopsy specimens may be necessary on occasion
to detect causative agents of deep, chronic endometritis.
Cytology-Results
of uterine culture are best interpreted in relation
to numbers of neutrophils detected from the endometrium
by exfoliative cytology.
Cytological
evaluation of the uterus of a mare showing predominantly
white blood cells (neutrophils) indicative of an inflammatory
reaction.
Uterine Biopsy-A sample from
the corpus cornual junction (site of embryonic fixation)
is one of the most accurate determinants of inflammatory
conditions and cellular infiltrates. The biopsy interpretation
is one of the most important determinants of subsequent
foaling rates. In our clinic we use the uterine biopsy
to give mare owners a prognosis of the chances of conception
and an estimate of the cost involved. 
A uterine biopsy from a young normal mare with
very good chances (over 80%) of conceiving and carrying
a foal to term.
Uterine
biopsy from an 11 year old mare with a history of chronic
infections and severe scarring in the uterus reducing her chances of conceiving and delivering
a foal to around 30% without proper management.
Other
Procedures-Examination for cytogenetic abnormalities and endoscopy for
visualisation of pathological changes are performed
as indicated.
Many
mare owners would gladly ask a specialist to look after
these mares at the end of the season, but few think it
necessary at the beginning.
Adherence to scientific
principals and dedication are the key factors in managing
a problem mare. Multiple factors acan contribute to
the problem. So elimination of the predisposing factors
(usually with surgery) as well as elimination of the
causing agent (usually bacteria) are important in developing
a treatment plan. Mares can be treated for uterine infections
locally by infusing the uterus with a proper antibiotic
or disinfectant, or by treating her systemically (muscle
or vein). The route depends on the type of antibiotic
that will be used as well as the individual mare’s response
to uterine treatment. Daily antibiotic therapy, ultrasound
examinations, uterine lavages, as well as drugs that
cause uterine contractility are used for a minimum of
3 days while the mare is in heat. Since mares often
do not develop systemic signs of uterine infections,
such as fever, the only way to monitor progress and
response to treatment is by daily ultrasonographic exams.
Unfortunately therapy itself is usually not enough to
achieve pregnancy. Careful management of the breeding
cycle is imperative. Breeding only once in the cycle
and reducing the inflammatory response after breeding
are critical components of this process. An accurate
diagnosis of the problem by an experienced veterinarian
is critical to establish an appropriate treatment plan.
Mares should be examined for
pregnancy at 14-16 days after the last breeding. By
performing and ultrasonographic exam at this time the
veterinarian still has time either to program another
breeding or perform diagnostic if the mare happened
to not be pregnant. Ideally the ovulation day should
be known in order to be able to detect twin pregnancies
as early as possible. If the mare is examined pregnant
at 14 days it is still possible that she could have
a smaller embryo superimposed or hidden behind a bigger
one. Therefore it is important to visualize the presence
of a single embryo and a single heart beat around 28-32
days. At day 45 there are some major hormonal changes
that happen in the mare so a check between 45 and 60
days is recommended. Mares are often vaccinated to prevent
abortion starting at 5 months. This is a good time to
do a final check so that you do not vaccinate an open
mare and can start preparing for an early breeding the
following year.
Normal 30 day single
pregnancy with a heart beat.
Puberty that should not be confused with sexual maturity occurs during the
second spring of life of a colts. Between that age (1 year) and the age
of 4-5 there is an increase in testicular size and sperm
production. There is no significant detrimental effect
on collecting or breeding a horse as soon as he has
gone through puberty. However the number of sperm that
can be harvested could be very small but quality should
not be affected. With proper handling there should not
be any negative consequences on the physical or mental
well being of the colt.
As a general rule, NO. However if mares are not going to be cultured, they
should be examined at least twice by an experienced
veterinarian with ultrasound while the mare is in heat.
1- A young (less than 6
years old) virgin mare should not have anything introduced
into her uterus except semen unless she has evidence
of fluid accumulation in the reproductive tract. 2- Mares that have histories of not conceiving, loosing
a pregnancy or have fluid in the uterus regardless of
age should always be cultured. 3- Mares that have a foal at foot but have poor reproductive
histories or were difficult to impregnate the previous
year should be cultured. Unless there is a very heavy
purulent discharge at the first heat after foaling (7-10
days) mares should not be cultured during that first
heat. Always culture mares when in heat and take a cytology
to avoid the possibility of false negative results.
Mares cultured when not in heat most of the times will
have a negative culture result but if the infection
is sub-clinical (mild) there is an increase chance that
the mare might only show the signs of infection at the
first breeding. 4- Always culture a mare that
did not conceive if she was bred at the right time and
with good semen
Cultures are only good for the cycle being breed
and not for 1,3 or 6 months later.
In the hands of an experienced veterinarian reducing a twin pregnancy to
a singke in the first 14-16 days has a greater than
90% successs rate. Reduction of twin pregnancies can
be done after 30 days by transvaginal aspiration. Rupturing
of one vesicle at this stage will release too much fluid
that will detach the remaining embryo/fetus resulting
in the death of both. This procedure can be done upto
60 days but it is preferable to do it by day 45. The
last resort is the injection of potassium chloride directly
into the heart of one fetus after day 100. This procedure
has about a 50% success rate.
Frozen semen that is maintained in liquid nitrogen will stay in the same
condition for hundreds of years. The reduction in fertility
is done during freezing and during thawing. However
during storage there is no real change in the quality
of the semen. Always keep in mind that freezing semen
can be done by many and preserving the fertility of
sperm through freezing is only done by few.
In general maiden mares have
very high fertility. However it is important to realize
that age has a tremendous effect on fertility. SO a
4 year old maiden and an 8+ maiden are completely different
animals even though they are both maiden.
Sport
or warmblood horse will start their training by the
age of 3 or 4 years and will start competing at the
age of 5 or 6. Most horses will not have an opportunity
to prove their full athletic potential until they are
6 or 7 years old. If the horse is considered a good
prospect it will continue in competition for a few more
years. As a consequence the great majority of warmblood
horses do not start their breeding career until the
age of 6 or 7. However there are a significant number
of horses, particularly mares that will not be bred
until they are eight years of age or older. It is not
uncommon to find mares presented to be bred for the
first time when they are in their early teens.
Most
of the old maiden mares, i.e. mares older than 8 years,
have some common characteristics which would resemble
a syndrome. First of all they are maiden and the response
to teasing is often erratic. Even when the mare is in
good standing heat visual inspection of the cervix reveals
a tight or poorly relaxed cervix and at palpation these
cervixes are seldom more than 2 -2.5 cm in diameter.
In fact most of the times the cervix will resemble that
of a pregnant mare even though these mares have a good
size follicle (>35 mm) and no circulating progesterone.
Vaginal palpation often shows a cervix that is either
completely closed or will barely fit one finger.
Histological evaluation of the endometrium shows a glandular
layer with wide spread dilatation resembling uterine
cysts. These dilated glands are most likely a consequence
of poor lymphatic circulation in the uterus due to its
long quiescence.
Ovarian
activity in these mares is mostly normal with some of
them developing large anovulatory follicles. One common
feature in these mares is that they will start to accumulate
uterine fluid during their estrus period. More than
likely this fluid is the result of endometrial edema
that due to the poor lymphatic drainage of the uterus
is not reabsorbed like a normal mare would, when she
approaches ovulation. Endometrial culture and cytology
very often will be negative. It is not uncommon to go
through 2-3 breeding cycles before these mares will
have a positive culture. Once the mare is bred the fluid
accumulation will be exacerbated due to poor lymphatic
drainage compounded by the tight cervix. The amount
of intrauterine fluid will vary in individual mares
ranging from a few cc to a liter in extreme cases. Conception
rate in these mares is often less than 50% per cycle.
To maximize the fertility
of these mares it is important that veterinarians be aware
of the possibility of this type of uterine and cervical
pathology. These mares will need closer monitoring of
their heat period by rectal palpation and ultrasonography,
and should be artificially inseminated only once close
to ovulation. The use of hCG or Ovuplant is strongly recommended
to reduce the number of inseminations. Furthermore these
mares should be reexamined between 4 and 12 hrs after
breeding and any excess fluid should be removed by performing
a uterine lavage with sterile isotonic saline or lactated
ringers. Administration of 10 IU of oxytocin or colprostenol
is also recommended to aide the uterine contractility.
Failure to do this will very often result in an infected
mare. Pregnancy and delivery seems to be normal on these
mares and once foaling has occurred the cervical problems
appeared to be diminished considerably. Perhaps the most
important aspect of breeding the old maiden mare is to
make the owner aware that even though this mare is maiden
there is a high possibility that she will be a problem.
Dr. Juan Camilo Samper.
Copyright © 2003 Veterinary Reproductive Services.
All rights reserved.
Revised:
January 20, 2004
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