Electrolytes and the Performance Horse

Electrolytes are substances that play an important role in maintaining osmotic pressure, fluid balance, and nerve and muscle activity. These substances are important because without the proper electrolyte levels, performance horses are slowed by fatigue and muscle weakness.

In the exercising horse, sodium, potassium, chloride, and magnesium are lost in sweat and urine. Owners need to have some idea of the magnitude of loss of electrolytes during exercise before a feeding program can be developed to replace these losses. Since most of the electrolyte loss in the horse occurs through sweating, one method of calculating electrolyte requirements can be based on amounts of sweat loss. Body weight loss during exercise is a good way to estimate the amount of fluid lost, where 1 kg (2.2 lb) of body weight loss equals 1 liter of fluid.

The amount of fluid loss will depend on a number of factors such as duration and intensity of exercise, temperature, and humidity. Therefore, the best way to determine this loss is to weigh the horse before and after exercise. This after-exercise weight should be taken before the horse is allowed to drink. During a routine workout, sweat loss in a racehorse amounts to between 5 and 10 liters. Losses of 25 liters might occur during a normal endurance ride, and 40 liters of fluid loss would probably only be seen in an exhausted, dehydrated endurance horse in serious danger of dying.

When researchers from the University of Tennessee and University of Georgia measured weight loss, water loss, and electrolyte balance in horses competing in a three-day event in New Jersey, they found that the 48 horses measured in this study lost an average of 18.4 liters of body water during the cross country phase of the three-day event. This occurred even though the environmental conditions during this event were fairly mild.

A major source of potassium for horses is forage. Hays typically contain from 10 to 20 grams of potassium per kg. When fed in adequate amounts, hay provides a great deal of a performance horse’s potassium requirement. Besides providing large quantities of potassium, forage helps maintain water balance in exercised horses.

German research has shown that horses fed adequate forage maintained water and potassium balance better during exercise than horses fed a high-concentrate diet. Unfortunately, forage is very low in sodium and marginal in chloride. Therefore, supplemental sodium and chloride are required by the performance horse. A portion of the sodium and chloride required by the performance horse can be provided by a salt lick. Research at Cornell University has shown that horses at rest will voluntarily consume about 50 grams per day from a salt block.

Although it is theoretically possible to fulfill an exercising horse’s electrolyte needs with plenty of good-quality forage and free-choice salt licks, many equine practitioners have reported that supplemental electrolytes are important and beneficial for maximum performance. Besides aiding in the prevention of tying-up, electrolytes help horses rebound from hard work sooner, return to feed quicker, and begin the necessary rebuilding phase that occurs after exertion.

While electrolytes are essential to the performance horse, electrolyte preparations must be properly formulated to meet the horse’s needs. Equine electrolyte replacements should not be largely sugar, but instead should be formulated to replace what is actually lost from the horse during exercise. In summary, electrolytes are essential nutrients for the performance horse. Because horses lose large quantities of electrolytes in sweat, requirements increase with exercise intensity and sweat loss.

Adequate intakes of good quality forage and a free-choice salt lick will help meet much of the electrolyte requirements of the performance horse. In addition, a commercial electrolyte supplement can help prevent electrolyte depletion. Kentucky Equine Research recommends the use of Restore SR (Restore in Australia), which contains the latest technology in electrolyte therapy, a proprietary slow-release mechanism that allows sodium to be released gradually into the gastrointestinal tract for sustained absorption. See the entire range of research-proven electrolytes offered by Kentucky Equine Research.