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What Are Electrolytes and Why Are They Important?By Kentucky Equine Research Staff · February 24, 2011
Every horseperson has seen and felt the white grit that remains on a horse's coat long after he's dried from sweating. But do you know what that is?
The grit is residual electrolytes that have left the body with the sweat and dried on the coat. It's easy to see that the more the horse sweats, the more electrolytes end up outside the body on the coat. In fact, horse sweat is more concentrated in electrolytes than blood, which is the opposite of humans, so there is potential for extreme losses of electrolytes in exercising horses.
The major electrolytes in sweat are sodium, chloride, and potassium. Minor amounts of calcium and magnesium are also present, as are miniscule quantities of other trace minerals. Electrolytes are responsible for maintenance of acid-base balance and osmotic regulation of body fluids. Without electrolytes, the body is not capable of maintaining the right amount of fluid in and around cells. Although body fluid regulation is complex and involves enzymes, hormones, and proteins as well as electrolytes, the basic concept revolves around cell hydration. If cells lose too much water, they die. It is therefore important for the body to have an adequate supply of electrolytes, which means there could be times when supplemental electrolytes should be added to the diet of the horse.
A normal diet of forage will provide some electrolytes to the horse. By feeding a commercial feed (usually containing salt) and giving access to a salt block (or loose salt), all of a horse's electrolyte requirements will be met under normal circumstances. In fact, the ingesta found in the large intestine acts as a reservoir of electrolytes for the horse to draw upon when needed. However, once the horse starts sweating a lot, whether it is with exercise or exposure to high heat, the reservoir may not be adequate in supplying sufficient electrolytes and, in this case, the horse will benefit from supplemental electrolytes. The quantity of electrolyte needed depends on how much the horse is sweating and for how long. Horses undergoing prolonged exercise like endurance or event horses may particularly benefit from electrolyte supplementation.
Electrolyte loss can result in dehydration. Testing for dehydration is simple: pinch a fold of skin over the shoulder and observe how slowly it returns into place. If the skin does not snap back quickly, measures should be taken to rehydrate the horse. Signs of more severe dehydration are unsteady gait, uncoordinated muscle contractions, trembling, and muscle weakness. The horse may lose interest in drinking even when dehydrated, because when both water and electrolytes are lost, the thirst response (the physiological trigger that tells a horse when to drink) malfunctions.
How do you dose a horse with electrolytes? First and foremost, salt should always be available to the horse. If salt is offered free choice, a horse has a good sense of how much salt its body needs. Be sure that the block is not contaminated with urine or feces as this may discourage intake.
Electrolytes are only part of the picture of fluid balance. Water is necessary and should not be overlooked when offering salt or electrolyte supplements.
When the horse is losing significant amounts of sweat, supplemental electrolytes should be given. A well-formulated electrolyte supplement should be mostly sodium chloride (salt). Other ingredients may be potassium chloride, calcium, and magnesium. Typically a little sugar is added to improve the absorption of sodium and improve the palatability, but sugar should not constitute more than 20% of the mixture. Most electrolytes can be mixed into a horse's feed or added to the water. If added to water, provide a bucket of plain water in case the horse does not drink the electrolyte-laden water. If a horse will not eat electrolytes in the feed or drink them in the water, they can be given in a concentrated solution in a syringe. When giving either concentrated electrolytes or electrolytes in the feed, it is extremely important to have free-choice access to water so that the horse has something to drink when the electrolytes make it thirsty.
