Long Days, Short Coats
the natural photoperiod with artificial lighting can "trick"
the horse's body into believing it is spring.
By Cindy A. McCall, Ph.D.
Extension Horse Specialist, Auburn University
horse owners who want their horse's haircoat short and shiny
all year, and owners who would like to breed their mares before
the horse's natural breeding season, can use an extended photoperiod
to accomplish these goals. Extending the natural photoperiod
(daylight hours) with artificial lighting can "trick"
the horse's body into believing it is spring. Most horses
will begin to shed their winter haircoat after 30 to 60 days
on an extended photoperiod and most open broodmares will begin
to show signs of heat and ovulate after 60 to 90 days.
there be Light
To extend the photoperiod, horse owners should put broodmares
and show horses under lights during mid November and keep them
under lights throughout the winter. The majority of horses exposed
to this program will shed their winter coat by February, and
broodmares should have a fertile heat cycle before March. Broodmares
foaling early in the year (January through March) may enter
their normal winter anestrus (the time when they are not having
heat cycles) after foaling. If early rebreeding is desired,
these mares should be
kept under lights through foaling and rebreeding.
keep a horse’s coat in top condition many trainers use
artificial lighting, in combination with blankets, to simulate
the longer, and warmer, days of summer.
in the horse's stall or in an outdoor holding pen should
be turned on from approximately 5:00 p.m. to 10:00 p.m.
daily. This gives the horse a total photoperiod of 15 to
16 hours of light which is the same amount the horse would
receive from daylight during the summer. Leaving lights
on continuously at night is not as effective as a 16 hour
daylength, so a light timer is useful in a lighting program.
Two footcandles of light provide enough illumination for
an artificial lighting program. In a 10 by 10 foot stall,
one 200 watt incandescent bulb or two 40 watt florescent
bulbs will provide enough light. A general rule is to provide
enough illumination to easily read a newspaper in the most
dimly lit area of the pen or stall.
Horse owners should remember that horses under an extended
photoperiod have little protection against cold weather
because they will shed their winter coats. To help these
horses stay warm (especially broodmares kept outside), owners
should make sure horses have windbreaks, shelters where
they can stay dry, and plenty of hay or pasture to help
them generate body heat. Under severe cold weather conditions,
horses may have to be blanketed to help them maintain their
McCall is a professor at Auburn University Department
of Animal Sciences where she teaches their equine science
courses and serves as extension horse specialist for