Hot weather gets many people reaching for an electrolyte supplement for their horse, but often they have little understanding about electrolytes or what they do. This is scary because, used improperly, electrolytes can make the risk of dehydration or electrolyte-related performance problems worse.
Electrolytes are nothing more than minerals dissolved in the horse’s blood stream. The horse must take in electrolytes/minerals year round to replace those lost in urine, saliva, bile, tears, intestinal tract secretions. Electrolytes are also lost in sweat, but in most cases the sweat losses are only part of the horse’s total daily needs.
The major electrolytes in blood are sodium and chloride, which together make salt. Inside cells, potassium substitutes for sodium. Other important electrolytes (minerals in free/dissolved form) include calcium, magnesium, and phosphorus and the trace minerals zinc, iron, copper and manganese.
Whether it’s summer or winter, your horse’s major source of electrolytes/minerals is his diet. The daily potassium requirement of a 1,000-lb. horse doing intense work is about 40 grams per day, but most hays contain a minimum of 1% potassium, meaning just 10 lbs. of hay a day will meet or exceed the potassium needs of a horse at work (1 lb. of hay provides 4.5 grams of potassium).
Potassium is included in large amounts in all electrolyte supplements, but the fact of the matter is the diet already contains plenty. Of all the important electrolytes/minerals, the only ones that aren’t present in adequate amounts in the diet are sodium and chloride — that’s plain old salt.
At baseline, the horse needs to take in approximately 1 oz. of salt a day to stay hydrated. Sodium is the major mineral controlling how much water is in the horse’s body. Because it is in such short supply in their diets, horses have evolved to have a strong hunger for salt, and their bodies will also save sodium at the expense of losing other minerals if they have to.
When sodium is in short supply, horses adjust by secreting less sodium in the urine (substituting potassium instead), producing more concentrated urine, and “robbing” the tissues surrounding the cells of water to preserve the volume of their circulating blood.
Horses that have not had access to salt can do well with these adjustments, but they’re always somewhat dehydrated. If they never get stressed or exercised they’ll probably be OK, but they quickly get into trouble with overheating and heat stress if temperatures climb or they’re worked.
The major error that people make when using electrolyte supplements is to ignore the horse’s basic salt requirement and think the electrolyte supplement is all their horse needs. This simply is not the case. Most supplements contain far too little sodium to even meet baseline requirements.
Another common mistake is to add them to the horse’s drinking water without also providing plain water. Some horses don’t like the taste of electrolyte products or have mouth sores/ulcers/abrasions that are irritated by the electrolyte-spiked water. The horse will also stop drinking supplemented waters once their sodium hunger has been filled. The result of any of these things can be that the horse does not drink enough plain water.
The first step in making sure your horse has adequate intake of electrolytes is to feed him a mineral-adequate diet with at least 10 lbs. of hay/day.
The next step is to provide free-choice salt or add salt directly to feeds. If you provide salt free-choice, monitor how much the horse actually eats. Loose salt, either in granular or fine (e.g. table salt) form, will usually be consumed more readily than salt in licks or bricks.
Make sure that the horse consumes at least 1 oz. of salt in cool weather, when inactive. With hard work and warm or hot weather, the horse’s basic salt needs will increase to 3 to 4 oz./day for an average-size horse.
There’s a place for electrolyte supplements, but it comes after you are sure the horse’s baseline requirements for minerals in the diet and plain salt have been met. Prolonged exercise (e.g. endurance rides) or shorter periods of intense exercise (racing, eventing) can result in large losses of sodium, potassium and chloride in the horse’s sweat.
Since it’s really not possible to “preload” the horse with extra electrolytes before the exercise starts, he’ll have to make up those losses after exercise. This can be done if your base diet is adequate, including salt content, but it can take a day or two.
To prevent losses piling up in horses being worked regularly and to avoid performance effects from losses during exercise happening faster than the horse can replenish them from what’s available in the gut from his diet, electrolyte supplements are useful.
To replace losses accurately, the supplement should have the major electrolytes sodium, potassium and chloride present in proportions that mimic those of sweat.
Sweat contains approximately twice as much sodium as potassium and twice as much chloride as sodium. This means the correct ratio is 1:2:4 for potassium:sodium:chloride. The quantity of electrolytes the horse needs depends on how much sweat he loses. Sweat losses during exercise vary, from about 2 quarts to over 10 quarts/hour. In terms of sodium lost, this amounts to anywhere from 5 to 25 grams/hour, which is a tremendous amount.
Unfortunately, most electrolyte supplements don’t come close to making up for the losses the horse has in a one-hour period. We find that some of the best choices, in terms of both concentration of electrolytes and their ratios, are Kentucky Equine Research’s Summer Games, KER’s Endura-Max (www.ker.com, 859-873-1988), and Peak Performance Natural Balance Electrolite (www.peakperformancenutrients.com, 800-944-1984). Mobile Milling’s Exer-Lyte (www.mobilemilling.com, 800-217-4076) is another excellent choice, although it’s just a little bit short on potassium but most equine diets can easily fill this gap. Supplement at a rate of 1 to 3 oz. per hour of exercise.