Page 107 - Speedhorse August 2018

Anhidrosis is a decreased ability to sweat in response to increased body temperature. In the horse, between 65-70% of body heat is lost via the evaporation of sweat.
ANHIDROSIS
A horse that is sweating in a
normal manner can dissipate approxi- mately 80% of the body heat generated during exercise or in high ambient temperatures. If a horse is unable to sweat properly, the ability to thermos- regulate can be dangerously compro- mised. Researchers don’t know how or why anhidrosis occurs in some horses, but theories such as hormonal and electrolyte imbalances, specifically low chloride, have been proposed. There
is also evidence that inability to sweat may be inherited.
The first clinical sign you might notice in a horse suffering from anhidrosis is minimal or no sweat production during times sweat would be expected. Additional signs are high respiratory rate and high rectal tem- perature which don’t resolve within ap- proximately 30 minutes’ post exercise. Lethargy and poor performance may also be noted during summer months.
These clinical signs are the result of the inability to dissipate heat from the body into the environment, resulting in mild to severe hyperthermia. Rectal temperature will be above normal.
the droplets aren’t small enough. You need to spray the water under pressure and put it through very fine nozzles. Then, it creates a fine mist. This mist, as it moves out with the fan pushing it, flash evaporates and cools the air,” he explains.
“In the less humid southwest, this is the rationale behind swamp coolers. They do the same thing, and as the colder air mass with moisture in it moves out, it evaporates and the temperature drops in that cold air mass. But, if you try that in Virginia in the summer where the humidity is already high and the air is saturated, it won’t work as well as it does in a low-humidity area. But, it is still better than nothing,” says Allen.
“When moving to an extremely hot climate, ideally, you’d have an air conditioned stall. However, they are very expensive. Your other option is simply fans. The air movement makes the heat more tolerable for the horse. The middle ground would be the use of mist- ing fans. Often, the compromise is fans in the stall and keeping the horse out of the direct sun unless he’s outside working in the cooler parts of the day.”
AVOID HEAT STRESS WHEN TRAVELING
Transporting horses in hot weather can put them at risk. “I knew of one case in California some years back, when a horse owner hauled two horses to the vet on a hot
day in an air-tight trailer and the horses died in the trailer on the way,” says Foss. “Most people would be amazed to know how much warmer it is in a trailer compared to outside. In hot weather, you need good ventilation and air flow. It is best if you don’t travel dur- ing the heat of the day, especially out across hot desert country. Trailers can be like an oven,” he says.
“Put a thermometer in your trailer so you have a better idea how hot it actually gets in there. This can be eye-opening to realize what your horse must deal with for all those miles,” says Foss. “Heat radiating off the asphalt makes the interior of the trailer hotter.”
Inside a car, temperatures can get up
to 130 to 140 degrees quickly without air conditioning. “I have a thermometer in
my truck, and it gets up to 130 or higher
just sitting in my vet truck here in Oregon, where we generally don’t think the weather is very hot. We routinely see cases where dogs are left in cars and become overheated, some- times fatally,” he says.
“Some horse vans and trailers have air conditioning. If they don’t, they need lots of air flow. When traveling with horses, try to
do it during the night or early morning when it’s cooler, and stop and check them regu- larly. Don’t stop too long, since during your leisurely lunch in an air-conditioned building, the horses are in the ‘oven’.”
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EQUINE HEALTH
Laura Patterson Rosa Photography