Heat and the Exercising Horse

Oct 24, 2011
Chris Thomas

Physical Exercise of the Horse Releases Heat - C. Thomas

When the horse is worked, only 20% of energy from the diet is utilised for muscular work. The remaining 80% is released as heat.

Because such a large amount of heat is generated when the horse exercises, it is worth being aware of factors in the environment that contribute to or can alleviate heat in the horse. Heat exchange between the horse and the environment can occur via four different means. These are:

Conduction
Convection
Radiation
Evaporation

Conduction and Convection and the Working Horse

Conduction is the direct transfer of heat between two surfaces that come into contact with each other. It occurs over a temperature gradient, where the heat is passed from the hotter item or animal, to the cooler surface. Consider walking barefoot on a footpath that has had the sun shining on it all afternoon, and the heat being passed from the footpath to one’s feet.

Convection involves the movement of heat within a liquid. This occurs in the horse at the surface of the skin, where heat is transferred between the horse and the air around it. It is possible to utilise convection in the form of cool water on the horse’s skin to assist in cooling down the equine after work. Whether via conduction or convection, heat in the horse can be acquired by or passed to the external environment.

Radiation and Evaporation as Forms of Heat Exchange

Radiation involves heat being passed between objects that aren’t physically touching. This can occur whilst riding out in a field or paddock with the sun shining. As well as producing heat on account of working, the horse’s temperature may increase on account of the heat put forth by the sun.

Evaporation is the horse’s most utilised method for getting rid of heat. This is carried out by panting and more so by the act of sweating. It should be noted by those exercising horses that the above factors can be to the detriment of the horse by increasing heat problems and therefore limiting performance.

For a horse that isn't well hydrated prior to work and has been worked for a lengthened time in hot conditions, the sweating capabilities of that horse may greatly decrease. This is known as anhidrosis and can be to the detriment of the horse's cooling capabilities.

It is also possible to use the above factors to assist in cooling down of the horse. Having an awareness of things in the environment that may add to the potential for heat stress or exhaustion can assist the rider in determining appropriate methods to avoid such problems (such as not working in the heat of the day) and to aid in the cooling down of the horse after work. Environmental factors that will increase the likelihood of horses suffering from the heat include temperatures of over 30 degrees Celsius, minimal or no breeze, clear skies and humidity levels of 70 – 90%.