Taking into account that a horse may live about three weeks without food but could die within a week without water, horse owners and handlers should pay particular attention to the quality of water available to their stock and the volume consumed.
A dehydrated horse will loose skin elasticity, have sunken eyes and present as “ tucked up “. Water deprivation can lead to digestive disturbances such as colic. A 500 kg horse can be expected to require 30 to 40 litres daily. The exact amount will vary according to environmental temperature, body temperature, activity and amount eaten. There exists a direct correlation between feed intake and water requirements such that a horse at 18 deg. C. will drink 2 litres of water for every 1kg of dry feed. At 38 deg. C. this can increase to 8 lt/kg.
Dehydration through sweating results in not just water loss but also loss of electrolytes. Sodium and chloride are the 2 main electrolytes in horse sweat. Potassium is also lost. Protein losses are generally high at the beginning of sweating but decline during prolonged work sessions. Providing energy levels are maintained protein losses in extended exercise tend not to be a problem.
In most situations adequate water, a balanced diet and inclusion of mineralised salt should provide all necessary fluid and electrolyte requirements. Where horses are involved in extended exercise causing heavy fluid loss oral electrolyte supplementation may be necessary.