cleaning the closet

karen Clanin (
Mon, 17 Nov 1997 06:55:31 -0800 (PST)

Found this in old files ('95) and thought it might be of interest.

Maintaining Fluid Balance
In Exercising Horses

More than big jumps and fierce dressage competition will
confront the horses and riders at the Olympics in 1996. The
combination of Georgia's high temperature and humidity in late
July and early August is expected to challenge both equine and
human athletes. While temperatures above 80oF can be expected to
stress all horses, the three-day eventers will be at highest risk
for heat related problems.
The second day of the three-day event comprises four phases
of endurance. Phases A-C include roads and tracks and a 2-3 km
steeplechase. Phase D, cross-country, is the most rigorous, and
is likely to result in heat stress if the environmental
temperature and humidity are high.
Three-day event horses have been reported to lose up to five
gallons of water, mostly in sweat, during the endurance test in
normal conditions. Greater losses could be expected when the
temperature is high. Sweating horses also lose significant
amounts of electrolytes. Ironically, some horses experiencing
large sweat losses will have a depressed thirst response, which
impairs their ability to replace their fluid losses during or
after exercise. If sweat losses are large and are not replaced,
horses may be affected by heat exhaustion. Problems that can
result from exercise in the heat include: weakened pulse and
prolonged capillary refill time, elevated rectal temperature,
cardiac irregularities, elevated heart rate, muscle cramps and
To assist horses in regaining or maintaining an appropriate
hydration state, researchers at the University of Kentucky have
been investigating the effect of dietary fiber on water balance
during exercise. Although diets containing more dry feed increase
a horse's water intake, it was unknown whether differences in
diet would be of any use to the horse during exercise.
In a recent study, horses given 15.62 lb of feed in the
evening meal drank 4.3 gal of water before their exercise the
next morning, while horses that ate 9.9 lb of feed drank only 2.9
gal of water. The higher intake diet contained a large amount of
hay, whereas the lower intake diet provided less hay and more
grain, but about the same amount of calories. It was hypothesized
that the higher fiber diet would hold water in the
gastrointestinal tract and provide a water reservoir during
When the horses receiving the test diets were exercised,
total sweat losses were similar in both treatments (about 5.28
gal/horse) but the horses receiving the hay diet had lower plasma
total protein concentrations. The lower total protein
concentrations were interpreted to mean that the high hay diet
did allow the horses to maintain a better hydration status. This
suggests diets utilizing large amounts of good quality hay will
assist horses in maintaining fluid balance during exercise.
Diets that encourage water intake and help the horse
maintain a fluid reservoir in the gut may also be useful when
horses are shipped long distances.

Dr. Laurie Lawrence, (606) 257-7509
Department of Animal Sciences, University of Kentucky