Heat Stress, Exhaustion and Heat Stroke in Horses

Oct 24, 2011
Chris Thomas

Excessive Fast Work in the Heat can Affect Horses - C. Thomas

Heat stress and exhaustion can greatly affect a horse's performing capabilities as well as negatively impact its health. Heat stroke can lead to death.

When it comes to working horses in hot and humid conditions, an awareness of the devastating affects of heat is important. Because a horse releases up to 80% of its energy as heat, being able to recognise when a horse is showing signs of being overheated is a necessary skill.

Heat Stress and Exhaustion in the Equine

Whether it be due to work, hot temperatures, high humidity or a combination of all three, the horse’s body will display signs when stressed by heat. Heavy sweating indicates the body’s response to trying to cool itself down.

This may be coupled with an elevated temperature and heart rate. A non compliant horse with regards to the continuation of exercise can also be a sign of heat stress. Other indications may include:

Quick, shallow breathing
A lack of energy or a seemingly depressed horse

It should be noted that the horse affected by heat stress won’t always show signs of thirst, even if sweating excessively and therefore losing a lot of fluid. Heat exhaustion like heat stress can be indicated by the above signs. On top of this, the affected horse may show signs of obvious dehydration and pale mucous membranes, as well as muscle cramps, disorientation and even diarrhoea.

It is important to recognise any of the above signs as possible cause for concern and in environments where heat stress is likely to occur, to consider how to rapidly cool down and rehydrate the horse. A vet may be required, especially if the number of signs indicating heat stress or exhaustion are many.

Heat Stroke in the Horse and Factors Affecting

Heat stroke is recognised as the severest form of hyperthermia and is an emergency in which veterinary attention should be immediately sought. The rectal temperature may be in excess of 42 degrees Celsius, with the horse’s heart rate being 80 – 100 beats per minute. The affected equine may have lost the ability to cool itself down by sweating, become confused and agitated.

There are certain factors that may assist in predisposing the equine to heat stress. These include horses that are fat and/or unfit for the task that is being asked of them. A long coat, lack of hydration prior to work and excessive warm ups or exercise bouts can also predispose the horse to being negatively affected by heat.

Being aware of factors that may lead to heat stress can help riders and owners to consider what they ask of their horse prior to working it. If signs do arise when working with horses, prompt treatment and vet attention is the best solution.