Page 96 - August_2023

VETERINARY VIEWS
Your horse’s external signs of heat stress may range from subtle to obvious and may include
oxygen debt breathe slowly but with deep breaths, whereas others with rapid respirations may, in fact, be somewhat more efficient in cooling by transferring heat circulated from the blood to the lungs as hot air.
Heat stress generally develops due to overexertion leading to overheating, rather than to external heating by the sun’s rays. A bright, sunny day contributes to high ambient temperatures. Warm air temperature and high humidity prevent a horse from adequately dissipating internal heat from the body. All horses need some assistance with cooling in summer months even if the respiratory rate is not inverted or elevated.
Help your horse cool down by copiously bathing his head, neck, and legs with cool water. Large blood vessels in these locations flush heat to the skin surface. Rapid evaporative cooling is achieved by continual sponging these areas. The head acts as a radiator because the brain must remain cooler than the inner core temperature of the body; increased heat to the brain contributes to central or mental fatigue. Large blood vessels, like the jugular veins and carotid arteries, facilitate movement of heat
out of the central body core as you sponge and soak these areas. Large blood vessels in the armpit, and lower legs should also be sponged repeatedly. Continuously apply and scrape water away until the horse’s skin feels cool to touch. The respiratory rate should settle down as internal body temperature returns to normal range. Continue to monitor rectal temperature and muscle tone as you cool out your horse. Once rectal temperature reaches 101 degrees Fahrenheit, you can stop and see if he stabilizes without further cooling assistance.
For an overheated horse, find an area of shade and decent air circulation, preferably with a light breeze. An enclosed space with stagnant air adds to heat retention. Fans are helpful for convective cooling – as air flows across a horse’s body, it pulls heat off the skin. Periodic, short walks help muscles pump heat out of deeper tissues. A dangerously overheated horse may need to be soaked entirely by hose or with buckets of water.
In some circumstances, cooling down a horse too rapidly could cause him to chill or to tie-up (myositis). A humid climate makes it difficult for a horse to dissipate heat out of the muscle depths with sweating and circulation;
Anxious expression
him immediately. If he still does not seem to recover, call your veterinarian immediately.
• General condition: Flagging body posture
(tail held high); lethargy; seems weak and/ or uncoordinated; stride flattens out; poor impulsion or stumbling; sagging or deflated posture when pulled to a stop.
• Mood: Irritable disposition when handled and/or when asked to perform; lack of alertness or interest; depression.
• Facial signs: Dull or glazed eyes; wrinkled lips; ears at half-mast; anxious expression.
• Body processes: Waning or absence of appetite; lack of thirst; reduced or absence of urine; reduced or absence of manure.
• Heat-related conditions: Myositis (tying-up syndrome); thumps (a rhythmic contraction of the diaphragm).
COOLING TECHNIQUES
There are simple strategies to assist in cooling out a horse. As you finish a work out, bring your horse immediately to a walk. Hop
Moodiness
off and spend a minute or two walking him
so blood flow continues to flush metabolic waste products and heat from his muscles. If
an overheated horse abruptly ceases working, blood pools in the muscles and compromises the circulating blood volume, contributing
to relative dehydration. Bringing a horse to a sudden and complete standstill after moderate to strenuous exercise is often counterproductive to efficient cooling. A fatigued horse may be reluctant to move. Provided he is not tied-up with muscle spasms, you can assist circulation in the muscles by massaging major muscle groups in rhythm with the heartbeat.
Both respiratory rate and heart rate should return more towards resting rates within 10 minutes of stopping exercise, and within 30 minutes after sprint efforts. If the heart rate returns to 60 bpm or below within 10 minutes, but the respiratory rate remains elevated, such an inversion does not necessarily imply a horse is in trouble. It means he needs help in ridding his body of the extra heat. Some horses in extreme
Lethargy
Heat stress generally develops due to overexertion leading to overheating, rather than to external heating by the sun’s rays.
94 SPEEDHORSE August 2023
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