Electrolytes are the salts that dissolve in body fluids, including sodium, chloride, potassium, calcium and magnesium. They help regulate hydration, nerve and muscle function, and they are lost in sweat. This guide explains how much a horse can lose, how everyday salt differs from an electrolyte supplement, when electrolytes are used and the cautions that apply.
How horses lose electrolytes
Horses cool themselves mainly by sweating, and their sweat is far saltier than ours. A 2022 review by Lindinger in Veterinary Sciences describes horse sweat as having much higher electrolyte concentrations than human sweat, with chloride the main ion lost, followed by sodium, potassium, magnesium and calcium. The review cites sweating rates of 10 to 15 litres an hour during hard work, with sweating continuing for some time after exercise, and notes that travel on a warm day can produce similar losses because transport is itself a form of moderate exercise.
The British Horse Society points out that hot weather and exercise increase sweating, which leads to the loss of both fluid and electrolytes. Those losses are not replaced by water alone, which is why salt and electrolytes matter for horses in regular work. The author of the Lindinger review has designed commercial electrolyte products, a conflict of interest the paper discloses, but its description of sweat physiology is consistent with other sources.
Salt first
For most horses, the starting point is plain salt. Salt supplies sodium and chloride, the two ions lost in the greatest quantities in sweat, and it is the simplest way to cover everyday needs. British Equestrian's hot weather advice suggests adding the recommended amount of salt or electrolytes to the diet and providing a salt lick in the stable.
- Salt licks. Useful as a constant source, but intake varies a great deal between horses, and some barely use them.
- Salt in feed. Adding a measured amount of plain salt to a daily feed gives a more predictable intake. Introduce it gradually and keep water available.
- Everyday balancers and feeds. BETA notes that sodium is usually declared under analytical constituents, so you can work out how much your horse receives at the amount you actually feed.
Our guide to vitamins and minerals explains how salt fits into a balanced ration.
When electrolytes are used
An electrolyte supplement provides a blend of salts in proportions intended to resemble sweat, usually with chloride, sodium and potassium as the main ingredients. The BHS notes that electrolytes may help before hard exercise, competitions or long travel where a horse sweats heavily. Typical situations include:
- hard or prolonged work, such as eventing, endurance or hunting;
- competition days, especially in warm weather, covered in our travel and competition section;
- long journeys, particularly in summer;
- hot, humid spells when a horse sweats even at rest or in light work.
Timing
The Lindinger review suggests giving electrolytes about an hour before exercise or transport, to start replacing losses as they occur, with further doses during long events and after work. It also recommends that rehydration after exercise or travel happens before the horse is given dry feed. Your vet or nutritionist can help you plan a routine for your horse's workload, and our page on performance horses covers wider management.
Water intake
Water and electrolytes work together. The Lindinger review explains that electrolytes need to be given with enough water: excess electrolytes given with adequate water are excreted by the kidneys, but without enough water they stay concentrated in the gut and can draw water from the body, worsening dehydration. Equally, large volumes of plain water without salts can dilute body fluids.
The BHS and British Equestrian give practical advice for keeping horses drinking:
- provide constant access to clean, fresh water that horses want to drink;
- monitor intake, because many horses drink less away from home;
- on long journeys, plan rest stops every three to four hours to offer water;
- carry plenty of water when travelling in case of delays;
- soaked hay or feed can add water, but should not be relied on as the main source.
Recognising dehydration
The BHS lists early signs as reduced or darker urine, drier or fewer droppings and mild lethargy. Later signs include a raised heart rate, a dry mouth with thick saliva, dull or sunken eyes, slow capillary refill and darker or reddened gums. Several signs together make dehydration more likely.
Forms of electrolyte
| Form | How it is used | Points to consider |
|---|---|---|
| Powder in feed | Mixed into a damp feed | Simple, but the Lindinger review notes top-dressing is not an effective way to correct significant dehydration |
| Powder in water | Dissolved at the stated concentration | Some horses refuse it; always offer plain water too |
| Oral paste or syringe | Given directly by mouth | Quick to give, but concentrated; the horse should drink soon after |
| Liquid concentrate | Added to water or feed | Check the dilution carefully |
Cautions
- Never without water. Only give electrolytes when the horse has access to water, and follow the manufacturer's directions on dilution and dose.
- Concentrated pastes. The Lindinger review warns that highly concentrated pastes given without enough water slow stomach emptying, may irritate the stomach lining and may contribute to gastric lesions. This matters for horses prone to ulcers, discussed in our guide to gastric supplements.
- Not too strong. The BHS advises that solutions should have the right balance and should not be too concentrated, and that horses must find them palatable enough to drink.
- Health conditions. Horses with kidney, heart or other medical conditions should only receive electrolytes on veterinary advice.
- Competition rules. If you compete, check whether the manufacturer is accredited under the BETA NOPS scheme and check your governing body's rules.
Reading an electrolyte label
Electrolyte products vary widely, and the front of the tub rarely tells you much. The useful information is on the back.
Ingredients and proportions
The Lindinger review argues that an electrolyte should broadly match the proportions of ions lost in sweat, with chloride, sodium and potassium as the main components, and that purified ingredients make this easier to achieve. It notes that natural salts such as Himalayan, Dead Sea or sea salt fall well short of sweat composition. The same review suggests that a proportion of dextrose, a simple sugar, can help absorption and palatability, so sugar in an electrolyte is not automatically a fault.
Analysis and feed type
BETA explains that a product with more than 40% ash, which is effectively its mineral content, is classed as a mineral feed, and that sodium is usually declared under analytical constituents. Use those figures and the daily dose to work out how much sodium your horse actually receives, and compare that across products.
When comparing products, look at the sodium, chloride and potassium supplied per daily dose rather than the price per tub, and read our guide on how to choose a horse supplement. Our desk reviews summarise published information on individual products.