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VETERINARY VIEWS
BEAT
THE
HEAT
by Nancy S. Loving, DVM
It is a glorious summer day, the stillness of the day punctuated by an occasional puff of wind ruffling the leaves in the trees. Your
horse’s neck is soaked, your reins slippery and lathered. Suddenly, the more effort you ask of your horse, the more lethargic he seems. It’s as if his legs are suddenly mired in deep footing, the ground holding him down. In fact, your horse has run out of steam, or more correctly speaking, his body is boiling over with too much heat, potentially nearing a dangerous state of exhaustion. You pull him up yet his
muscles remain quivering, his breaths come quickly, his nostrils are flared. Could you have foreseen this development? Could you have prevented your horse from pushing the red line into the hot zone?
THE BUILD-UP OF HEAT
Heat and humidity, and especially if coupled with taxing exertions like speed sports, may push a horse beyond a threshold of compensation. As a horse’s muscles push him forward, each muscle group contracts and
strains with the effort of each stride. Over half the energy that is used for muscular activity
and locomotion in a horse is converted to heat. At high ambient temperatures, muscles (and
all body tissue) demand more oxygen. If left unchecked, heat continues to build in muscles, stimulating a decline towards exhaustion. As metabolic demands are not met, muscles fatigue. Loss of muscular control and strength can lead to accidents; a tired horse may stumble and fall, placing both horse and rider in jeopardy.
High-intensity exercise, even for short periods, can tax the ability of a horse to move heat out of the body as quickly as necessary. Without mechanisms to dissipate this heat, it could accumulate to dangerous levels. Sweat pulls heat from the interior
in a process known as evaporative cooling. Around 70% of the heat of locomotion is normally dissipated from the body using this evaporative cooling process.
During a short or moderate sprint, a sweating horse loses some body water and some small degree of electrolytes, but then the exertion is quickly over. In a short
time, he easily replenishes what was lost. Recognition of when it is time to stop exercising is important to your horse’s health.
HEART AND RESPIRATORY RATES
Horses deserve to develop the benefits
of a strategic conditioning program with a tailored approach to your equestrian pursuits. Training often concentrates on skills essential to an intended discipline. Yet, another
Sweat pulls heat from the interior in a process known as evaporative cooling. Around 70% of the heat of locomotion is normally dissipated from the body using this evaporative cooling process.
92 SPEEDHORSE August 2023
Over half the energy that is used for muscular activity and locomotion in a horse is converted to heat.
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