Judging by the catalogs I get in the mail, there are a lot of people feeding their horses electrolytes in the summer months.
The premise is good: they help prevent your horse from becoming dehydrated. But are they essential to your horse’s health?
According to this article on http://www.horsetalk.co.nz, Pass the Salt: electrolyte replacement for Horses:
When exercised intensely in hot, humid weather, a horse may lose up to four gallons of sweat per hour. In that four gallons, a total of 30 teaspoons of body salts are lost. Horse sweat contains primarily sodium, chloride, and potassium, but other electrolytes, including magnesiumand calcium, are also present in smaller amounts.
The concentration of electrolytes in the bloodstream and sweat is not identical. Horse sweat is considered hypertonic, which means a greater concentration of electrolytes exists in sweat than in fluids circulating within the body.
Some people seem to feed/dose with electrolytes to replace those that are lost through exercise; others feed electrolytes as part of the horse’s daily rations. Some people think having a salt block available free choice is enough; and others add salt to their horse’s feed. The probable answer is that most of these are an okay solution.
Keep in mind that most commercial horse feeds contain salt, potassium and magnesium, so at least some these minerals are being replaced every time your horse eats. However, in extremely hot weather, when your horse is sweating even without activity, or after a hard workout in the heat, I can see the need to replace those lost electrolytes. It also probably does no harm to feed them on an ongoing basis in limited quantities. Ironically, over supplementing with electrolytes can cause dehydration. The most important ingredient to keeping your horse hydrated is, of course, water. So it is important to always have clean, fresh water available.
There are a lot of commercial electrolyte mixtures available, but you should read the labels before purchasing. Many commercial mixtures contain a lot of sugar (dextrose). You should look for one where the first ingredient is salt and which has the correct ratio of potassium:sodium:chloride (1:2:4).
You can also make your own electrolytes easily enough by mixing regular table salt with lite salt at a ratio of 3:1. You can feed 2-5 oz per day depending on the heat and activity level of your horse.
While I often do supplement with table salt and also have a salt block available, I’ve never fed electrolytes. But I don’t generally ask Freedom to work all that hard in the summer and I make sure he’s hydrated by feeding him well soaked beet pulp with every meal. If I were eventing or doing an endurance ride, I’m sure I would consider adding electrolytes to his diet. And I might just pick up some of the lite salt so I can mix my own electrolyte for those really hot summer days.