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Heat Exhaustion in Horses:

ArticleHeat Exhaustion in Horses: | Midwest Veterinary Supply

Heat Exhaustion in Horses:

Horse Owners Should Take Precautions During Heat of Summer

Meg Green, DVM, is a member of the Merial Veterinary Professional Services Team. Dr. Green is certified in Equine Acupuncture and has an interest in Equine internal medicine. She has expertise in ambulatory medicine working with broodmares, foals, performance horses and racehorses. Dr. Green has practiced in Alabama and Kentucky, and continues to practice in Georgia and Tennessee when time allows. Dr. Green earned her doctor of veterinary medicine degree from Tuskegee University School of Veterinary Medicine. Below, she answers a question about heat exhaustion.

Q. I exercise my horse throughout the summer. Do I need to be worried about heat stroke?

A. Heat stroke, also known as hyperthermia, can be a great risk to horses, especially when it is hot and humid. A horse can also over heat, or suffer from heat stress, without the extreme clinical signs that a horse suffering from heat stroke will exhibit. But if left untreated, a horse suffering from heat stress can rapidly deteriorate to heat stroke or hyperthermia, and the repercussions can be fatal.

To help you understand how to avoid the dangers of an overheated horse, you have to start by understanding how the horse regulates its body temperature. Under normal conditions, the horse's body maintains its normal temperature by moving heat through the muscles and out via the skin.¹ This sweating mechanism allows the horse to keep cool. It's important to understand that "normal conditions" are a combination of temperature plus relative humidity that equals 130 or less. For example, a temperature of 80 degrees Fahrenheit and 50 percent relative humidity would be "normal."

As that sum increases, the horse's ability to manage its body temperature decreases. When the sum exceeds 150 (90 degrees Fahrenheit and 60 percent relative humidity), the horse's ability to sweat is severely compromised. In cases where the sum is greater than 180, the horse is virtually incapable of keeping its body cool.¹

It's important to address overheating as soon as you suspect it has occurred to avoid the progression to heat stroke or hyperthermia, which can have serious complications. Here are some of the clinical signs:

  • Temperature as high as 105- 107 Fahrenheit
  • Dry skin, especially when the horse should be sweating
  • Dehydration (you can determine this by pressing your thumb into the horse's gum, which should be moist and slimy to the touch under normal circumstances)
  • Rapid pulse and respiration
  • Muscles quivering
  • Depression
  • Refusal to work
  • Stumbling
  • Disorientation

If you suspect your horse has overheated, you should contact your veterinarian immediately. He or she will help you determine the severity of the situation and may recommend any or all of the following while you wait:

  • Guide the horse to a cool area, in the shade outdoors or under a fan in the barn
  • Cool the horse by spraying cool (not excessively cold or warm) water, beginning with the major blood vessels on the inside f the leg
  • Ice packs on the horse's head where the brain signals cooling to the rest of the body.
  • Dry skin, especially when the horse should be sweating

Avoiding overheating - - and the possibility of it leading to heat stroke - - is essential and should be part of every horse owner's protocol during the summertime. Here are some tips to avoid getting into a heat- related health situation:

  • Be aware of the sum of the ambient temperature and relative humidity so you understand the potential risks.
  • Minimize exercise time when the sum of the ambient temperature and relative humidity exceed 130.
  • Exercise horses early in the morning or late in the evening when temperatures are lower.
  • Provide cool, fresh water continuously.
  • Avoid leaving your horse in a parked trailer. Think of your automobile and how quickly it heats up. Although a trailer has windows, it is much the same situation.
  • If your barn has poor circulation, add fans in strategic areas.
  • Supplement your horse's diet with electrolytes.
  • After exercise, or even during a hot summer day, spray your horse with cool water.

As always, consult your veterinarian to determine the type of program that will work best for your horse.

©2013 Merial Limited. Duluth, GA. EQUILGN1336 (08/13)

¹Haugen S. Heat stroke. American Association of Equine Practitioners.
Available at: www.aaep.org/info/horse-health?publication=783 Accessed July 29, 2013.

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