If you’ve been checking the daily forecasted highs and letting out a sigh of frustration this summer, you’re not alone. Many of us are constantly on the lookout for the best ways to support our horses if we need to train or compete in warm weather.  

Oral electrolyte pastes and powders are a popular tool to help horses replenish minerals they may lose while exercising or due to certain medical conditions. 

Horses can produce several gallons of sweat in the course of a workout, depending upon air temperature, humidity, work intensity, and fitness. Contained in that sweat are minerals like sodium, chloride, and potassium, but also calcium and magnesium in smaller amounts. Having depleted levels of those minerals can, in extreme cases, have an impact on body system function.  

Dr. Bryan Waldridge is a former practicing veterinarian who is now an associate clinical professor in the Mississippi State University College of Veterinary Medicine.  

“It’s rare, but it will happen with eventers or endurance horses when it’s hot, they’ll lose calcium in their sweat and what will happen is the calcium level in their blood will drop,” explained Waldridge.  

This, combined with the horse’s increased respiration rate during exercise, can impact a nerve that controls the contraction of the horse’s diaphragm. When calcium is in low supply, the phrenic nerve can become overstimulated, causing diaphragm contractions that look like hiccups and are commonly called “thumps.” The nerve runs over the right atrium of a horse’s heart, so the contractions often become synched with the horse’s heart rate. Although thumps (known more formally as synchronous diaphragmatic flutter) aren’t harmful by themselves, they do signal that something is off. 

Even horses who don’t experience this kind of electrolyte loss can benefit from a supplement. Waldridge likes to see electrolytes provided to horses with PPID and other endocrine disorders that may make them sweat more than average, or even to those who don’t consistently sweat enough as a means of preparing them for the rare, more intense sweating episodes that can sometimes strike.  

For Waldridge, the jury’s out on whether giving a horse an electrolyte supplement will significantly change their hydration levels, though they probably will get a horse to drink more water in the short term.  

“If you give them a paste electrolyte, part of the reason they’re going to drink, and really the main reason we drink as humans, is that the back of our throat gets dry,” he said. “How much that’s truly going to stimulate drinking is debatable. The body is really good at keeping sodium levels consistent.”  

Horses, like humans, are designed to maintain a certain level of salinity in their bodies. That means if they take on a lot of salt, they’ll drink a lot of water, but probably only to the point of restoring that balance. Once the electrolyte gets to the horse’s small intestine, it will cause the intestine to pull in more water from the body to offset the saltiness, but the large intestine will pull that water right back out as part of its normal process. A horse who takes on a lot of salt and then drinks water to offset it will also urinate more to help flush out any excess of minerals. 

Waldridge encourages owners to look at the label of an oral electrolyte supplement before feeding it to a horse or pony.  

“You want to look at the ingredients, and you want the first thing to be sodium chloride. You don’t want to see ‘glucose,’” said Waldridge. “It can be flavored, but you don’t want the very first thing on the label to be sugar.” 

Follow label instructions on the amount of oral electrolyte to give to your horse. Most products suggest feeding one to two ounces once or twice per day, which Waldridge said is appropriate. It is possible to give too much of an electrolyte, although Waldridge said this is rare. Keep in mind that some horses will have strong preferences about taste and texture; Waldridge has known a few who prefer their electrolyte mixed in with water (though if you do this, you should have fresh water readily available at the same time). And, most importantly, check with your veterinarian if you have concerns about whether your horse could benefit from an electrolyte or how much to feed.