The production of sweat by the horse is his main mechanism for cooling the body down when it becomes hot. When the horse is working 80% of the energy produced by the muscles is released as heat, this heat, unless it is released would cause the body to overheat fairly quickly. The heat is carried to the skin by the circulatory system where it is carried away by the evaporation of sweat,
Did you know that a horse can lose 10-15 litres of sweat per hour when working? This can be become a problem because of the way in which the horse's sweat is made up. Unlike human sweat, which is mostly water, the horse's sweat is a fairly equal balance of water and electrolytes, this means that although the horse is becoming dehydrated his body does not tell him to drink. In fact, a horse can become up to 25% dehydrated before his body will tell him to drink.
Loss of the electrolytes in sweat, sodium, potassium, magnesium and chloride, causes the horse to fatigue quicker and his muscles to become weaker. In fact, it has been suggested that Exertional Rhabdomolysis or Tying up is actually related to electrolyte imbalances within the muscles and as such can be prevented by supplying the horse with sufficient electrolytes. Electrolytes will also help the horse to recover from exercise quicker. It is also important to note that should an electrolyte imbalance occur it can take the horse many months to completely rebalance his body.
We can, therefore suggest that electrolyte supplementation is essential for working horses all year around as no matter what the weather, if the horse is working, he will be sweating.
It is essential, however, that the horse is given an electrolyte supplement that is balanced to provide him with the correct balance of minerals that his body requires. Also unlike human electrolyte supplements, it is important that the electrolytes used should not be sugar based, although small amounts of sugar improve mineral absorption from the small intestines. For many leisure horses a quality forage diet and a mineral salt lick may be all that is required, but for horses in work and especially those that sweat a lot or get 'stressy', a more focussed supplementation regime may be required.