Whether it’s summer or winter, your horse’s major source of electrolytes/minerals is his basic diet. For example, the daily potassium requirement of a 1,000-lb. horse doing intense work is about 40 grams per day. Most hays contain a minimum of 1% potassium, so 10 lbs. of hay a day will meet or exceed the potassium needs of a horse at work and 5 lbs. of hay will keep a horse at mainetance (1 lb. of hay provides 4.5 grams of potassium).
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.
Salt: the Major Concern
At baseline, the horse needs to take in approximately 1 oz. of salt a day to stay optimally hydrated. Sodium is the major mineral controlling how much water is in the horse’s body. Because it’s 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. This loss of water in the tissues is what makes a dehydrated horse’s skin stay tented up away from his body if you pinch it (see sidebar, p. 5).
Horses that have not had access to salt can maintain their circulating blood volume well, 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, heat stress and serious electrolyte abnormalities 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 begin to meet the baseline requirements. Horses still need salt.
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. Horses with stomach ulcers may avoid electrolytes, too. 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 doesn’t drink enough plain water.
The first step in making sure your horse has an adequate intake of electrolytes is to feed him a mineral-adequate diet with 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 form (e.g., table salt with/without iodine), will usually be consumed more readily than salt in licks or bricks.
Make sure that the horse consumes at least 1 oz. of salt per day in cool weather, when inactive. That’s a pound of salt every 16 days. With hard work (sweating) and warm or hot weather, the horse’s 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’re sure the horse’s baseline requirements for minerals in the diet and plain salt have been met. It can’t be stressed often enough that failure to provide the horse with a balanced diet and to meet his minimum-salt requirement of at least 1 oz. per day, whether working or not, will get you into trouble that electrolyte supplements can’t fix.
Prolonged exercise (e.g., endurance rides) or shorter periods of intense exercise (racing) 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 (and during, for horses that work all day). This can be done if your base diet is adequate, including adding more salt to make up for sweat losses, but it can take a day or two for heavy water and electrolyte losses to re-equilibrate.
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, 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 80% as much potassium as sodium and twice as much chloride as sodium. The quantity of electrolytes the horse needs depends on how much sweat he loses. Sweat losses during exercise vary, from about two quarts to over 10 qts./hour. In terms of sodium lost, this amounts to anywhere from 5 to 25 grams/hour.
Unfortunately, most electrolyte supplements don’t come close to making up for the losses the horse has in a one-hour period. Our pick for concentration of electrolytes/oz, price and correct balances is Peak Performance’s Natural Balance Electrolite.
Mobile Milling’s Exer Lyte noses out Gateway’s Su-Per Lyte for Best Buy, requiring just a bit more potassium for ideal balance to match sweat, primarily a consideration for horses working for prolonged periods in high heat.