Page 103 - July 2022

VETERINARY VIEWS
“An essential training ingredient important to the success and well-being of any athletic horse is fitness of the cardiovascular system.”
ANHIDROSIS
As mentioned, the metabolic conversion
of food into energy drives locomotion of an actively exercising horse. Energy production
is only 20% efficient while the remaining 80% is generated as heat. The equine body has developed mechanisms for efficient heat dissipation to avoid “boiling to death.” One such mechanism is through sweat, also known as evaporative cooling – this contributes to 65% of cooling. The lungs may blow off as much as 25% of internal heat, noticeable as a hot horse stands blowing or panting.
A horse moved to a hot, humid climate,
or in hard training in rigorous temperatures, may need a period of acclimatization to
form adaptive, heat-dissipating mechanisms. During the initial 5–10 days in an adverse climate, some adaptive changes occur, reaching a plateau by 3 weeks. Yet, in some cases, a horse doesn’t adapt well to heat and humidity – heat exhaustion results when the horse doesn’t sweat sufficiently to rid his body of heat created by working muscles. This syndrome is called anhidrosis, derived from the Greek, meaning “without sweat.”
The first things you might see in a horse suffering from anhidrosis is hair loss on
the face and an abnormal sweat pattern,
with sweat retained beneath the mane and saddle, in the armpits and flanks, but absent elsewhere. The horse’s skin feels dry and hot to the touch rather than being coated with sweat. He is likely to perform poorly, loose his appetite and thirst, and appear lethargic and tired. You should contact your veterinarian
Sweat is a combination of body fluids and electrolytes.
promptly – they can test for anhidrosis and then offer appropriate recommendations.
Fitness is critical to enable a horse to perform as efficiently as possible. While acclimatization may be possible, it is important to monitor fluid intake and recovery times of heart rate and respiration. Avoid exercise in thermally stressful periods – cooler mornings are best for riding; if there is unusually high heat and humidity, don’t ride at all.
Dietary strategies are helpful, too. To provide ‘cool fuel’ for horses engaged in aerobic-type exercise, offer grass hay (protein of 8–12%). Supplement with fat (rice bran or vegetable oil) as necessary to maintain body weight – dietary fat has the lowest metabolic heat increment. Restrict concentrates to less than 0.5% of body weight (< 5 pounds grain or concentrate per 1000# horse) at each meal.
Provide free choice, granulated table salt and make sure that your horse has access to ample, clean water at all times.
If basic management changes are ineffective, then it is necessary to either substantially reduce the level of performance or to relocate the anhidrotic horse to a cooler climate.
To provide ‘cool fuel’ for horses engaged in aerobic-type exercise, offer grass hay with 8-12 % protein, supplemented with fat such as rice bran or vegetable oil to maintain body weight, free choice salt, and ample water.
“Heat exhaustion results when the hor doesn’t sweat sufficiently to rid his body o
created by working muscles.”
SPEEDHORSE July 2022 101
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f heat
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