By definition, electrolytes are mineral salts which become electrically charged particles called ions when dissolved in water. Whilst scientifically accurate, this explanation offers little help to horse owners when it comes assessing their horse’s need for electrolytes.
When horses sweat they lose electrolytes, the main ones being sodium, potassium and chloride. Calcium and magnesium are also lost although in much smaller amounts.
Electrolytes control the movement of water in the body and play an important role in many cell functions, including muscle contractions and the transmission of nerve impulses. As a result, an imbalance of electrolytes can may lead to conditions such as heat stress, fatigue, synchronous diaphragmatic flutter (also known as thumps) and tying up. The body also needs electrolytes to retain water which is why it can be difficult to rehydrate by drinking water alone.
Having said this, the amount of electrolytes lost is directly proportionate to the amount the horse sweats and consequently, free access to a salt lick and plenty of forage is more than sufficient for the majority of leisure horses and those in light work. In fact, most losses would gradually be replaced over time, simply by the horse eating and drinking normally.
For horses sweating heavily on a regular basis, table salt and in some cases a combination of table salt (sodium chloride) and Lo-salt (sodium chloride and potassium chloride) provides an effective and economical alternative to commercially prepared electrolyte supplements. Whilst it’s not possible to ‘preload’ electrolytes, maintaining hydration and electrolyte balance prior to exercise or competition is an important precaution, helping to reduce the risk of conditions such as tying up.