Electrolytes are minerals dissolved in the blood and tissues of the body, which carry a positive or negative charge and can bind with another ion to make a 'salt'. They help to preserve the correct balance of fluids in the body's cells and are involved in muscle function and the processing of wastes. Deficiencies cause dehydration, impaired performance and may exacerbate clinical problems such as azoturia.
Electrolytes are lost daily through sweating, in urine and faeces. These losses can normally be replaced in the diet. The horse relies on sweating to control body temperature during exercise and it is generally accepted that 90% of a horse's weight loss after exercise is due to sweating. It is important that this weight loss is monitored and the fluid and electrolyte losses replaced, otherwise poor performance will result.
During periods of exertion such as competition and training, electrolyte losses can be considerable, particularly during hot weather. Even under normal exercise conditions, a 500kg horse could lose 10 litres of sweat during two hours of exercise. This sweat would contain 60g of Chloride, which represents 10% of the total Chloride in the body. Through increased sweating there is a loss of important nutrients including electrolytes and trace elements. This can lead to a decrease in performance level, increased agitation, and muscle tension and spasms if not compensated quickly.