occurs when loss of fluid from the body, via feces, urine, sweat and water vapor
in exhaled air, exceeds fluid intake from food and water. As dehydration occurs,
fluid is lost from the blood, which becomes more concentrated. When the fluid
lost from the blood is not replaced, the volume of blood in the body decreases.
Blood carries oxygen and nutrients to the body, and removes waste products. If
there is less blood, it is unable to circulate to all of the tissues as
frequently as normal. Consequently, the heart beats faster in an attempt to
circulate the blood around the body more quickly, attempting to compensate for
the decreased blood volume.
Dehydration may occur as a consequence of colic, diarrhea, choke, excessive
sweating, poor appetite (insufficient amount of food – malnutrition) or blood
loss. The commonest causes of dehydration in the horse are diarrhea, sweating,
colic and performance on drugs like lasix.
average adult horse (15.2 h) produces approximately 125 litters of saliva and
digestive juices each day. These usually pass through the small intestine as it
digests food, and are then reabsorbed in the large intestine. In surgical colic
cases where the intestines are blocked, fluid is continually produced in saliva
and digestive juices but is prevented from reaching the large intestine by the
blockage and so cannot be re-absorbed. Instead it sits in the small intestine
causing dehydration and pain as it stretches the intestinal wall. In cases of
diarrhea, inflammation off the large intestine reduces its ability to re-absorb
fluid, and so the horse passes out very loose, watery feces (diarrhea).
or extreme exercise (work), such as in endurance rides, long days at shows
combined with a long trip, racing (especially on lasix), may cause excessive
amounts of fluid to be lost in sweat, particularly if the weather is very hot.
This will cause dehydration, if not replaced. In addition, whenever large
amounts of blood are lost, the amount of fluid in the body is markedly depleted
and dehydration and shock follow.
appetite will cause dehydration through the failure to take in fluid. This also
occurs in choke, where fluid is also lost in saliva, which cannot be swallowed.
As dehydration develops, affected animals will become progressively duller and
more shocked. The amount of urine produced will decrease as the body tries to
conserve fluid, and urine will also become more concentrated. Animals will have
tacky or dry mouth, and their lower limbs and ears will become cold.
“water management" in the individual horse care can prevent the dehydration
caused by fluids lost due to sweating.