Exercise and stress: impact on adaptive processes involving water and electrolytes

The horse has a regulatory system which responds in a complex manner to stress, such as exercise. It supplies the fuel and ensures thermoregulation, resulting in the production of sweat. Cutaneous water and electrolyte losses are controlled by thermoregulation, independent of hydration status and/or electrolyte homeostasis. The negative balance for water Na, K and Cl may be a factor in limiting performance and impairing recovery. The strategy in caring for a horse before, during and after exercise involves improving hydration and electrolyte status and the use of NaCl as a feed or in a watery solution (iso- or hypotonic). The voluntary intake of saline is not safe for any horse. If salt is supplemented in a feed, it is essential that water be made available ad libitum. It is also important that, after salt intake, sufficient time is allowed to give the horse the opportunity to drink an adequate quantity of water. Application of K prior to exercise is not recommended. During exercise, NaCl solutions can be administered, while salty supplements are less suitable as regard the time required to stimulate water intake. After exercise, K can be added to supplements or solutions to balance the K deficit.