Horses and Heat Stress - Important Facts to Know

Much of the country is experiencing extreme heat this summer.  Humans tend to retreat to either an air conditioned place or they head to places such as the pool or beach for relief.  Horses, unfortunately, do not have those choices.  

What is meant by "heat index"?

Heat index is the sum of the temperature plus the humidity.  Here is an example: Let's say the temperature is 80 degrees Fahrenheit and the humidity is 20%.  The heat index then is 100 (80+20+100).

When is it too hot to ride my horse?

A horse's body produces heat when it works.  Horses have several mechanisms that will cool them.  

Evaporation is the most important mechanism,  Most of the heat is generated from the horse's large mass of muscle.  The heart and blood vessels move the heat from the organs and muscles to the skin.  As the horse works, sweat is produced in the glands in its skin.  Sweat is composed of water, sodium, chloride, potassium and calcium.  The sweat evaporates, cooling the horse by dissipating large amounts of heat.

If the heat index is less than 120, it is okay to ride.  As the heat index rises above 120, begin watching it.  The horse's cooling system will not work effectively once it reaches 150.  If it reaches 180 or more, the horse will be unable to sweat in order to cool off.  This may lead to heat stroke.

What are the signs of heatstroke in the horse?

The signs of heatstroke in horses are:

-  The respiratory rate is higher than 30, which does not return to normal after several minutes of cooling off.

-  The heart rate is higher than 80, which does not return to normal after several minutes of cooling off.

-  Excessive sweating or no sweating at all!

-  The body temperature is 103 degrees F or more, which does not decrease after several minutes of cooling off.

-  Depression or lethargy

-  A condition called "thumps".  This is a flutter of the diaphragm due to loss of calcium.  Basically, the stomach area will be seen as twitching.

What to do if the horse has heatstroke?

If any of the above mentioned problems are seen, cool the horse with plenty of cold water, either with hosing or sponging the body.  Allow the horse to drink if it wants to.  Call the veterinarian, IMMEDIATELY!!  The veterinarian will decide if IV fluids and electrolytes will be needed.

Horses that have experienced heat stroke will require rest for about 10 days.  When the horse is brought back to work, it should start out gradually, starting with a light workout and building up to it's regular work schedule.  

One thing to keep in mind is that horses that have experienced overheating, may be prone to do so again.  Therefore, it is best to take steps to prevent it from occurring.