Developing the Sport Horse: The Importance of Hydration

As we move through the height of our summer competition season, it is not uncommon to have multiple days of severe heat and humidity - the days when you sweat while standing still.

Heat and humidity can be harder on your horse than they are on you. Most of us have worked to motivate a sluggish horse through the final jump-off or day three of a competition, but why does it happen? Was our training off the mark? Perhaps the horse needs a different energy source in his feed. Or was it caused by that energy-zapping heat and humidity? Let’s take a close look at the role sweating plays in the horses' ability to cool, and how extreme heat and humidity can affect their ability to perform.

What happens to horses while exercising in the heat?

As the horse begins to work, heat is produced as a by-product of muscle contraction at a 4:1 ratio. As the body temperature climbs and adrenaline levels increase, sweat glands respond by producing a hypertonic (highly concentrated) salt solution that coats the hair. Under normal circumstances horses cool by evaporative cooling and convection. The movement of air over their body is paramount to both of these mechanisms.

Evaporative cooling: The sweat coats the hairs and as air flows over them it pulls the moisture and the heat off the horse.
 
Convection: Blood vessels near the skin dilate and allow the transfer of heat from the blood into the air.

During intense exercise, horses can lose up to 10-15 litres per hour in sweat alone. Once their body temperature reaches greater than 42 degrees C, the respiratory system kicks in to help “blow off” some of the extra body heat (approximately 15 percent of the body heat can be dissipated via respiration).