As you’re riding on a hot, windless day, it feels great to canter and get a cool breeze blowing on your face. But the increased effort also causes your horse’s body to heat up. As sweat lathers his sides, he loses electrolytes—substances essential to a variety of body functions, including transporting energy into cells and removing waste products. Without adequate electrolytes, your hardworking horse isn’t able to sustain his performance. Eventually, you’ll feel him begin to flag.
Comprising salts and minerals—including sodium, chloride, potassium and calcium—electrolytes control practically every major biochemical reaction in the body. They are especially important for maintaining fluid balance, generating energy and contracting muscle. Supplied in the diet, they are expelled primarily through urine, manure and sweat. They need to be replenished on a regular basis. Electrolyte levels that are out of balance for a prolonged period can cause serious problems. Understanding how these vital substances affect equine health and performance can help you gauge whether your horse needs a supplement.
Most horses get all the electrolytes they need from what they eat. An individual who is fed a normal diet and has access at all times to fresh, clean drinking water and a salt block generally is able to meet his “resting” electrolyte requirements. If, however, he works hard enough that he loses more electrolytes through sweating than he can regain by eating, he’s a candidate for supplementation. Eventing horses at Preliminary level and above almost always require more electrolytes than their diet supplies.
Because horses’ needs vary, there is no “one supplement fits all” regimen in terms of timing and dosage. A number of factors play a role: Your horse’s fitness level, performance demands, hair coat and body weight all influence the amount of fluid and electrolytes he loses through sweat. Environmental conditions are a consideration, too. For instance, humidity interferes with how quickly sweat evaporates. So on a muggy day a horse is likely to sweat more to get cool—losing increased electrolytes in the process.
With regard to supplementation: More is not necessarily better. Excess electrolytes can have an adverse effect. For instance, oversupplementing sodium can potentially elevate its level in the blood so that a horse exhibits neurologic signs—changes in behavior, loss of coordination, even seizures—especially if sufficient water isn’t available or he isn’t drinking enough. (A word of caution: Never add electrolytes to your horse’s water without also providing a bucket of plain water for him to drink.)
Because there are so many variables to bear in mind, it’s best to call your veterinarian to determine whether electrolyte supplementation is necessary for your horse. Together you’ll discuss your horse’s diet and exercise routine, then decide how to keep his body’s essential salts and minerals in balance to maintain his well-being and maximize his performance.
This article was originally published in the July 2014 issue of Practical Horseman.