Spring is an exciting time of year with all the new
foals, warmer weather, and more daylight. It’s also the time of year
we breed our mares for next year’s foal crop.
Have you ever wondered why we breed mares in the
springtime? As many of us know, mares are classified as seasonal
breeders. Most of us have heard that mares need the increasing
period of daylight, (longer photoperiod) associated with spring
before they will come into heat known as estrous. As the length of
daylight increases, it stimulates the pineal gland within the brain.
This stimulation results in a decreased production of melatonin
which allows for the secretion of hormones that lead to estrous.
The photoperiod is a primary factor initiating
estrous in the mare and consequently it gains most of the focus.
Also very important in influencing estrous in mares is nutrition and
climate. In my experience, conception rates are always highest in
those mares with a Body Condition Score (BCS) of 5 or 6 on a scale
of 1-10. This means the ribs are invisible, but readily palpable.
Also noted, conception rates are lower when there are cold spring
storms throughout the breeding season. Working in the Northern
climate, this is also seen when using artificial lights to
manipulate or “trick” the endocrine system of the mare in order to
stimulate estrous. Increasing the photoperiod on a mare that is too
thin or too heavy may or may not stimulate estrous. Inconsistent
results also occur without the use of heated barns or blankets in
the colder northern climates. However, if I am able to increase the
photoperiod in a climate controlled barn with mares having a BCS of
5 or 6, I consistently produce estrous behavior greater than 90% of
Breeding horses is not cheap; do your homework, have
your mare in shape, and invest in a quality Breeding Soundness Exam
performed by a qualified veterinarian. This will allow for a true
assessment of your mare’s reproductive potential. Ensuring a
reproductively healthy mare, choosing a fertile stallion, and a
little help from Mother Nature will produce the horse of your
This tip was brought to you by Dr. John Smart,
Belgrade, MT (406-209-6907) and KAM Animal Services, home of KAM’s
“Equine Learning Circle” FREE webinars, which take place monthly.
These webinars are an expansion of KAM’s weekly tips. Go to
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each time a new tip is posted. The FREE webinars will conclude with
a question and answer session, so be ready with your nutrition