Electrolytes are simply minerals that are dissolved in body fluid (blood and cell fluids). They are vital to a wide range of normal body functions, including the regulation of all body fluid levels, nerve impulse transmission, muscle contraction, and many essential metabolic processes such as pumping of the heart, movement of food and water through the gut, and the filtering of wastes through the kidney and liver.
Exercise generates a great deal of heat that must either be dissipated from the body or stored. The dissipation of heat is very important, because if a large amount of heat is stored, body temperature will rise to dangerous levels. In the horse, the processes that contribute to the dissipation of heat during exercise include radiation, convection, conduction and evaporation. Of these, evaporation may be the most important; particularly when horses are exercised in warm conditions. To facilitate evaporative cooling, horses sweat. Sweating is certainly desirable as a means to maintain body temperature, but high sweating rates result in high rates of water and electrolyte loss. The cooling effect of sweating is significantly reduced in humid conditions, as evaporation from the skin is very inefficient in high humidity.A horse sweats even more when it is not fully fit or conditioned, in hot or humid weather, or when it is nervous, excited or agitated. In hot, humid conditions a horse can lose up to 15 litres of sweat in one hour. Electrolytes are lost in the sweat. Excessive sweat losses can cause an electrolyte imbalance, which rapidly leads to premature muscle fatigue, reduced stamina, muscle cramps and poor post exercise recovery, if not corrected. Horses lose about 3 times more sodium and up to 10 times more potassium in sweat than humans, so the composition of sweat in horses contains much more electrolytes than in humans.
Electrolyte availability can become a problem when the rate of loss exceeds the rate of replacement. Normal salt does not replace the other essential electrolytes, nor will it help buffer the acidosis caused during hard work. Studies have shown that some horses fail to take in even the minimal requirements if they are simply given a salt block.During an eventing competition or when a horse is worked very hard several days in a row, intake of electrolytes from a salt block and the regular diet will not be able to match the losses in sweat. Thus, in these situations, a horse will benefit from electrolyte supplementation.
Tips for ensuring adequate hydration
- Give electrolytes before the horse gets dehydrated.
- Make sure water is available and encourage the horse to drink. If possible, keep track of about how much water the horse is consuming.
- Like water, electrolytes can be retained in and then absorbed from the large intestine, so adding electrolytes to the diet just prior to the event will be helpful.
- Once the event is over, monitor the horse carefully. Although it is not always convenient, it may be best to wait several hours after finishing a long ride or event before transporting the horse home. Transportation can be a dehydrating experience on its own, and transporting an already dehydrated horse may increase the potential for more serious problems such as colic.
- If your horse is exercising in hot, humid weather, he may need 2-4 times the amount of water that he usually drinks.
- Make sure that your horse has continual access to water!
- One wet-down flake of hay can absorb 1-2 gallons of water. If you feed your horse well-soaked hay, you can make a real impact on his fluid consumption. Event riders take advantage of this by feeding their horses soaked hay before events.
- Don't give your horse dry hay after competition - it will soak up water that the horse needs elsewhere in the body.
- The horse's stomach empties very rapidly in response to a water ingestion, so you really needn't be concerned about colic, or a stomach that is too full of water when you exercise
- Horses that have done long, moderate exercise should be allowed to drink water immediately after competition. It is a fallacy that horses have to be cooled down first.
It is widely accepted as essential to supplement electrolytes daily in the diet of performance horses, and the rate of supplementation will vary with the degree of fitness, work levels required, and the environmental conditions.
Electrolyte losses can be significant even in cooler months, and it is recommended that daily supplementation continue during all training and competition stages.