Winter Dehydration in Horses
It's a little known fact that horses can actually be thirstier in the winter
than they are in the summer.
"During cold weather, especially if the humidity is high, a horse's thirst
mechanism does not always function as efficiently as it does in the
summer," said Ken Gallagher, a Michigan State University College of
Veterinary Medicine Extension equine veterinarian.
Some water is lost from a horse's body every day through the urine, feces and
moisture in breath exhaled from the lungs. If the horse is performing during
cold weather, significant water can also be lost from sweating.
Dehydration occurs if a horse loses too much water from its body and does not
replenish it, or if a horse just is not consuming enough water every day to meet
its bodily needs. A three to four percent loss of body water will cause mild
dehydration.
Some horses will only drink five to six gallons of water per day, eat normally
and remain healthy. "These horses are the exception; their kidneys have the
ability to concentrate urine and recycle more of the water back into the
body," said Gallagher.
Most horses are not capable of this kind of kidney function and should be
provided adequate, good quality water. Most adult horses weighing 1,000 lbs
require a minimum of 10 to 12 gallons of water each day for their basic
physiological needs.
Good quality water must be free of harmful germs, foreign material, excessive
minerals, environmental pollutants and unusual flavors.
Occasionally, horses will eat snow if it is available and cut back on drinking
water somewhat. "Horse owners should not depend on snow as a water source
and should provide an adequate water supply," he said.
Regardless of season and weather conditions, horses should have water every day
in plentiful supply.
It is the most important nutrient, because it is needed for almost every bodily
function: it helps to maintain appetite and proper moisture level in feed and
feces, maintains normal blood volume and aids in the normal function of sweat
glands.
There are two common complications resulting from inadequate water consumption
during cold weather.
The first is decreased feed intake. "Even if good quality feed is offered,
the horse will cut back on consumption if it is not drinking sufficient
water," said Gallagher.
One reason for this is the lack of saliva to mix with the feed as it is being
chewed. A normal adult horse in a state of good hydration will secrete up to 10
gallons of saliva per day to help soften the food mass as it is chewed and
swallowed.
If the appetite is affected and less feed is consumed, the horse might not
receive enough energy to tolerate the cold weather, he said.
The second, and potentially more harmful complication, is impaction colic or
constipation. Both the feed material during digestion and the fecal contents
after digestion must maintain adequate moisture levels or they can cause a
blockage in the intestinal tract.
A horse will not become impacted in one day from decreased water consumption.
The process usually happens over several days to several weeks. "If the
horse becomes chronically dehydrated over a period of time, the body reserves
are lowered and a blockage can occur," said Gallagher.
The usual signs of an impending impaction colic are depression, decreased
appetite and decreased
production of manure that is drier than normal. If these signs are observed, a
veterinarian should be called. Early detection usually means the colic can often
be resolved without requiring surgery.
Always provide adequate, good quality water, preferably on a free choice basis.
If horses are given access to a tank or automatic waterer, consumption cannot be
determined accurately.
Owners should watch for signs that these horses are not eating well or becoming
lethargic. If horses are watered from pails, either by hand or in a stall, be
aware the stomach capacity of a 1,000pound adult horse is only five to six
gallons, so it is difficult for them to drink more than that amount at one time.
Two waterings per day will provide only the minimum amount of water needed.
Under those conditions, a horse should have an opportunity to drink more
frequently, especially if the horse is performing.
Previously, it was thought the best water temperature for horses was from 45 to
65 degrees, and if the water got colder, many horses would decrease consumption.
This was especially true of horses 12 years of age or older whose teeth are
sometimes more sensitive to cold water.
A recent study of water consumption by ponies during cold weather indicated
warming the water well above freezing temperature resulted in approximately 40
percent more water consumed per day.
It probably is not necessary to increase the water temperature a great deal for
every horse, Gallagher said, but it would be worthwhile if consumption is below
normal or if a horse has a tendency to get impacted.
Increasing salt intake might also stimulate a horse to drink more. The idle,
adult 1,000 pound horse should be consuming about two ounces of salt per day. If
salt has been added in a commercial grain mix, an owner can offer the horse an
additional handful of loose salt in the grain box or provide a salt block.
Dr. Hal Schott, DVM, PhD
Department of Large Animal Clinical Sciences
D202 Veterinary Medical Center
Michigan State University
East Lansing, MI 48824-1314