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.
The main electrolytes are:
- Sodium (Na)
- Chloride (Cl)
- Potassium (K)
- Magnesium (Mg)
- Calcium (Ca)
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.
Signs of electrolyte deficiency include:
- Dull coat
- Sunken eyes
- Poor performance
- Dark urine
Providing electrolytes for horses
The horse’s body cannot retain water without the presence of electrolytes, so simply offering water after exercise will not rehydrate your horse. Electrolytes should be added to either the water or the feed.
Adding electrolytes to water to form an isotonic solution (a solution that contain the same electrolyte concentrations as that of the body fluids) will ensure that both fluid and electrolyte losses are replenished and the horse becomes quickly rehydrated. However, after prolonged sweating it will take several days of electrolyte supplementation to completely replenish losses.
Alternatively, if your horse is a poor drinker or there is no opportunity to replace fluid losses during the competition, electrolytes may be fed alongside a small amount of concentrate feed. Electrolyte pastes are also available. However, a large single dose can cause the horse to absorb water from the blood vessels surrounding the gut and actually worsen the effects of dehydration in the short term.
Sodium chloride (salt) should be available for the horse ad lib in the form of a salt block and intake should be monitored, particularly in hot weather. Alternatively feeding a tablespoon of table salt daily will ensure you horse receives sufficient sodium chloride.
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Giving electrolytes to competition horses
The electrolytes most commonly used in supplements – sodium chloride, calcium carbonate and potassium chloride – are not included in the FEI clean sport prohibited substances list. Neither are other common ingredients, such as sodium bicarbonate or glucose. Simple electrolyte supplements should, therefore, be safe for use in competition horses. However, it is advisable to check the label of any supplement or ask the manufacturer. For the full list of banned substances visit
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