Electrolytes: Who Needs ‘Em?

By: Dr. Lydia Gray

See the horse in the picture? That’s Newman, my five-year-old Trakehner gelding. He’s just started showing in dressage and as his mom/vet, I closely monitor every aspect of his health while he’s away from home and in a strange environment. That’s why I became very concerned when he wouldn’t drink at his last show and even seemed a little “colicky". All of his vital signs were normal however, so the only action I took was to give an electrolyte paste by mouth about four hours before his class that day, so it would have time to stimulate him to drink.

 He put in a beautiful test and appeared fine the rest of the day, but it got me thinking: should I give him electrolytes the day before we show, the morning of the show, and/or after we get home? Should I put electrolytes in his grain or water on a daily basis? Should I offer him another salt block? Hopefully you can benefit from the "desk research" I did to answer these questions for my own horse.

First, what exactly are electrolytes? Medline says “electrolytes are minerals in your blood and other body fluids that carry an electric charge." Electrolytes affect hydration, blood pH, and play an important role in many of the body’s processes including muscle contraction and nerve conduction. There are a number of electrolytes, but the ones of greatest concern to horse owners (especially during the summer) are sodium, potassium and chloride because these are the major ones lost in sweat.

The only way horses can replace these nutrients is through their diet, but according to Dr. Ray Geor, in the April 1998 edition of The Veterinary Clinics of North America, Equine Practice,

"The quantity of sodium present in many feed stuffs is minimal, therefore, it is often necessary to supplement even a well-balanced ration with an additional source of this ion. Although access to a salt block can be beneficial, there is evidence that horses do not consume sufficient salt to meet daily requirements when a salt block is the sole source of supplementary sodium."

(It turns out that salt blocks were originally designed for cattle who have much rougher tongues so some horses won’t lick long enough to meet their sodium and chloride needs.)

Since supplying a salt block is not the answer for the horse doing more than standing in a pasture, what are some other options? Unfortunately, it’s not possible to store electrolytes in the body, so trying to “preload" a horse with doses of electrolyte paste several days before an athletic event or long-distance transport isn’t the answer. And putting electrolytes in the horse’s water may backfire, causing him to drink less and become dehydrated.

Research has shown that daily electrolyte supplementation in the grain is a safe way to make sure losses caused by exercise, hot weather and shipping are replaced. As a guideline, experts recommended providing 50-75 grams of loose salt to a horse’s diet each day, divided between two feedings. By “topdressing" these vital nutrients, you ensure your horse has what he needs when he needs it while any extra is simply eliminated as waste.