Horse Illness Can Be Prevented With Electrolyte Supplementation During Hot Weather Exertion

Electrolytes can be an important horse health additive during hot temperatures of summer.

A horse that sweats during competition might lose some body water and salts, but these losses are usually replenished upon eating hay, drinking, or visiting the salt block.

However, there are other situations, involving horses in barrel racing, roping and distance events when electrolyte supplementation is important to the horse’s safekeeping and welfare.

‘Electrolytes are salts, notably potassium, chloride, sodium, calcium, and magnesium, and are essential to proper body horse function,” according to Dr. Hal Schott, professor at the Michigan State University College of Veterinary Medicine, East Lansing, Michigan.

For muscles to obtain energy, food must be converted into fuel. In the horse, approximately 70-80 percent of this conversion to energy is liberated as heat.

In the best situation, heat is dissipated from the inner recesses of the horse’s body as sweat, which cools by evaporation of “water” from the skin. Even with moderate exertion during hot weather, a horse sweats.

“High humidity conditions make it hard for sweat to evaporate and cool the horse, so to compensate, the horse sweats more and for a longer time,” Schott said.

The longer a horse works, the hotter and more humid the climate, the less fit the horse, or the harder the effort, the more he sweats. “More sweat means more body salts or electrolytes are lost along with evaporated fluid,” Schott said.

Hot weather increases sweating which reduces sodium, chloride, and potassium in horses. Electrolyte supplementation can help prevent illness.

In every case, it is important that a horse engaged in exercise has access to as much water as he wishes to drink at any time.

Of course, there is the old adage and irritating truth, “You can take a horse to water, but you can’t make him drink.”

Some horses won’t drink at every opportunity because they might be finicky about the taste, nervous, or don’t have the need.

“While electrolytes won’t necessarily enhance performance, they will improve water intake, especially by maintaining sodium levels,” Schott said.

A horse that is not drinking might be best served by electrolytes. “A bucket of salt water made by adding five ounces of salt to a five-gallon bucket of water can also be offered in addition to plain water,” Schott explained. Horses drink the most when it is about 68 degrees.

The amount and frequency of electrolytes required are dependent on several factors, including weather conditions, horse fitness and competition demands.

“There are no hard and fast rules on the amount of electrolytes to administer, as each horse is an individual,” Schott said.

Over supplementation of electrolytes can irritate the intestinal tract. The hotter the temperature and the higher the humidity, the more electrolytes will be needed.

“It takes at least an hour or two for electrolytes to be absorbed, then equilibrate in fluid compartments after administration,” Schott said.


Electrolytes can increase water intake and prevent problems with horses used heavily on hot, humid days.

Objective in supplementing a sweating horse with electrolytes is to replenish at least 30 percent of sodium and potassium losses.


A horse that drinks plain water without any electrolyte supplementation further dilutes the concentration and balance of salts in the various tissue compartments.

Sodium is essential to drive the thirst reflex, so a dehydrated horse that has lost excess sodium in the sweat or has diluted it by drinking plain water might not make the necessary effort to replenish his fluid losses.

“Electrolytes” is a vague term. According to Schott, losses of calcium and magnesium are 100-fold less than sodium, chloride, and potassium losses.

He stressed that replacing the “essential three” improves the horse’s acid-base status and facilitates better availability of calcium in its ionized form.

Many commercial formulations are available, but some consist mostly of sugar. “The objective is to supplement salt, not sugar,” Schott said. “An alternative homemade recipe delivers 100 percent of the essential three and is inexpensive to make by combining an equal mixture of table salt and lite salt.”

Some horses are acutely sensitive to oral electrolytes developing an irritable stomach, excess salivation, and/or mouth ulcers. It can be helpful to buffer an electrolyte mixture with an antacid.

Electrolytes can cause gastric ulcers. Best course of action is to have a veterinarian examine the horse’s stomach and retire him from training and competition until treatment results in healing.

“Depletion and disproportionate blood and tissue levels of salts, coupled with dehydration could lead to metabolic illnesses, heat stress, exhaustion, colic, or laminitis,” Schott warned.

“Electrolyte supplementation has a valuable role in safeguarding horses, but it is not the primary ingredient for performance success,” Schott explained.

“Rather, it is an adjunctive tool to conditioning and competition. Knowing if and when to supplement with electrolytes requires constant vigilance as to how well a horse is coping with the demands of the day,” the veterinarian summarized.