Exercising horses produce a tremendous amount of heat and sweat, especially inhigh heat and humidity. This sweat is important as it allows the horse’s body to dissipate the heat produced by evaporation. Dr. Ken Marcella indicates 65% of the heat produced by a horse is dissipated by evaporation of sweat, and the horse has a lot of wasted heat to get rid of as only about 25% of the fuel taken in is used for work. To put this amount of heat in perspective, Dr. Kerry Ridgeway indicates that a horse racing at 28 miles per hour for just 2 minutes produces enough heat to bring 2 gallons of water to a boil. An endurance horse at speed loses over 3 gallons of sweat in 1 hour.
While human sweat contains few electrolytes, equine sweat contains large amounts of sodium, chloride, magnesium, and potassium. Dr. Marcella indicates that although conditioning helps humans lose less electrolytes by conserving sodium, fit horses still lose about the same amount of electrolytes as unfit horses. It has been shown that some endurance horses can lose up to 75 pounds in the first 15 miles of a race. Dr. Harold Schott indicates that because horses lose a large amount of electrolytes in sweat, they do not receive adequate signals to drink after exercise even though they are dehydrated. Research has shown that offering salty water can increase water consumption after exercise. Although many commercial electrolyte replacements are available, a more effective mixture can be made with common ingredients. For electrolyte replacement, horses can be offered 1 to 2 ounces per day of a mixture of 1 pound table salt, 20 ounces lite salt, and 2 tablespoons Epson salts.