Electrolytes are compounds that conduct electricity when in solution. In horses the most abundant and important electrolytes include sodium, potassium, chloride, calcium and magnesium. These electrolytes are involved in a variety of basic cell functions, including muscle contraction and nerve impulse transmission. Loss of electrolytes and electrolyte imbalances have far-reaching consequences, impacting virtually every equine body system.

The average horse needs to drink 27-30 liters of water per day. In hot climates or during strenuous exercise, as many as 10-12 liters of water can be lost per hour through sweat alone. Loss of water during exercise and sweating is hypothesized to increase the osmolality of the blood, making horses want to drink to replenish lost fluids.