When and how to supplement
Few topics in equine nutrition generate as much confusion and conflicting advice as electrolyte supplementation. Walk into any tack shop, and you’ll find shelves stocked with electrolyte products in every conceivable form: powders, pastes, pellets, liquids. Ask ten different horse owners when and how to use them, and you’ll likely get ten different answers. Some swear by year-round daily supplementation, others use them only after intense work, and still others question whether they’re necessary at all. Here at HQ, we’ve long shared in that confusion, but with our ‘new year, new you’ mindset still fresh, we thought we’d dive into a topic that has long struck fear into the HQ editorial team.
The truth about electrolytes, as research reveals, lies somewhere in the nuanced middle ground of all the advice you’re likely to hear. Electrolyte supplementation can be genuinely beneficial, even crucial, for horses in certain circumstances. But it’s not always necessary, and inappropriate use can actually cause more problems than it solves. Understanding what electrolytes are, how horses lose and replace them, and when supplementation is truly warranted allows you to make evidence-based decisions for your horse’s welfare.
This article (which has taken us many hours to research and produce!) examines the science behind electrolyte supplementation, acknowledging both where research provides clear answers and where significant questions remain. Because this is an area where evidence is sometimes conflicting and recommendations have evolved, all major claims are referenced to their research sources.
Understanding electrolytes: the basics
Electrolytes are minerals that, when dissolved in body fluids, carry an electrical charge. The primary equine electrolytes are sodium, chloride, potassium, calcium, and magnesium. These charged minerals are essential for virtually every physiological process: maintaining fluid balance, enabling nerve impulse transmission, facilitating muscle contraction and relaxation, and regulating pH balance (Lindinger, 2022).
Unlike many nutrients, electrolytes cannot be stored in the body beyond what’s dissolved in body fluids and contained within cells. They’re constantly being lost through urine, faeces, and, most significantly for athletic horses, sweat. This means electrolytes must be continuously replenished through diet (Lindinger, 2022).
The unique nature of horse sweat
What makes horses particularly vulnerable to electrolyte depletion is the composition of their sweat. Horse sweat is hypertonic, meaning it contains a higher concentration of electrolytes than the blood itself (McCutcheon & Geor, 1996). This contrasts dramatically with human sweat, which is hypotonic, meaning it contains a lower concentration of electrolytes than blood. This means that when a horse sweats, he loses proportionally more electrolytes relative to water than a human does.
The visible evidence is obvious: the characteristic white foam and salt crystals on a horse’s coat or between the hind legs after work. This is visual proof of massive electrolyte loss. Research shows that horses can lose up to 10 to 15 litres of sweat per hour during intense exercise, with each litre containing approximately 3.5 grams of sodium, 6 grams of chloride, 1.2 grams of potassium, plus smaller amounts of calcium and magnesium (Lindinger, 2022).
“A horse performing prolonged moderate to intense exercise can lose 30 to 40 grams of sodium in a single session, which is more than 20 times their daily maintenance requirement.”
Importantly, horses lose substantial amounts of electrolytes even when sweat isn’t visibly dripping. In hot, dry conditions, sweat evaporates almost as soon as it reaches the skin surface, meaning the horse still loses the electrolytes, but owners don’t see the wetness and may underestimate losses (Lindinger, 2022). This is particularly relevant in South African summers, where low humidity facilitates rapid evaporation.
Do horses need supplementation?
This is where the controversy begins, as the answer depends entirely on the individual horse’s circumstances, and research provides both clear guidance and remaining uncertainties.
Horses that don’t need supplementation
Horses at maintenance or in light work generally receive adequate electrolytes from a forage-based diet, with one critical exception: sodium. Forages provide ample potassium but are notoriously deficient in sodium and chloride. However, this deficiency is easily addressed with free-choice access to salt, either as a block or loose granulated salt (Mad Barn, 2022).
For horses doing light work (gentle hacking, light schooling sessions under an hour) in moderate temperatures, a balanced diet plus salt is typically sufficient. These horses aren’t sweating heavily enough to deplete electrolytes beyond what normal dietary intake and salt consumption can replace. Adding electrolyte supplements in these circumstances isn’t harmful if adequate water is provided, but it’s probably unnecessary (Hartog, 2024).
When supplementation becomes important
The evidence strongly supports electrolyte supplementation for horses engaged in prolonged moderate-to-intense exercise, particularly in hot or humid conditions. Multiple studies demonstrate measurable benefits:
Research by Waller and Lindinger (2021) showed that horses given electrolyte supplementation before exercise maintained better hydration status, lost less fluid from muscle tissue, and could work significantly longer than horses given water alone. The pre-exercise electrolyte loading helped protect muscle cell electrolyte content despite ongoing sweat losses.
Studies of endurance horses found that those receiving electrolyte supplementation drank more water voluntarily, lost less body weight, and maintained higher blood sodium and chloride levels compared to unsupplemented horses (Zeyner et al., 2017, as cited in Kentucky Equine Research, 2025).
The practical implication is clear: horses sweating heavily for extended periods – endurance horses, event horses, racehorses in training, horses competing in hot weather – benefit measurably from electrolyte supplementation. The supplement helps maintain hydration, supports continued performance, and aids recovery (Lindinger, 2022).
The grey zone: moderate work
Where guidance becomes less clear is for horses in moderate work, i.e. a typical riding horse doing an hour of schooling that produces visible sweat but not profuse sweating. Here, the research doesn’t provide definitive answers, and expert opinions vary.
Some nutritionists argue that these horses can adequately replenish electrolytes through their normal diet plus salt over the course of 24 hours, making immediate supplementation unnecessary. Others suggest that supplementation aids faster recovery, which matters if the horse will work again the next day (Integrity Horse Feed, 2025).
A practical guideline suggested by some researchers is to consider the combined effect of temperature and humidity: if the temperature in Fahrenheit plus relative humidity percentage exceeds 150, conditions warrant electrolyte supplementation even for moderate work (Integrity Horse Feed, 2025). In South African summers, this threshold is frequently exceeded.
What makes an effective electrolyte supplement?
Not all electrolyte products are created equal, and research provides clear guidance on what constitutes an effective supplement.
Proper electrolyte ratios
An effective supplement should replace electrolytes in proportions similar to what’s lost in sweat. Research by Lindinger (2022) emphasises that proportion matters more than absolute concentration. The supplement should provide sodium, chloride, potassium, magnesium, and calcium in ratios that mirror sweat composition.
As a general guide, a good electrolyte supplement should contain approximately equal amounts of sodium plus potassium as chloride. Many commercial products meet this standard, though careful label reading is required (GAIN Equine, 2024).
The sugar controversy
Many electrolyte supplements contain significant amounts of dextrose or glucose. Manufacturers often claim that this enhances absorption, citing human sports drink research. However, research specific to horses tells a different story.
A study by Lindinger and Ecker (2013) found that adding dextrose to equine electrolyte supplements did not increase the rate of electrolyte absorption in horses. This suggests that supplements with high sugar concentrations offer no absorption advantage and simply add unnecessary calories. For horses with metabolic concerns or those prone to gastric ulceration, high-sugar electrolytes may be contraindicated (Kentucky Equine Research, 2025).
The evidence supports choosing electrolyte supplements with minimal added sugars and avoiding those that list glucose or dextrose as primary ingredients (GAIN Equine, 2024).
Osmolality matters
For effective absorption, electrolyte solutions should be slightly hypotonic, i.e. less concentrated than body fluids. Although horse sweat itself is hypertonic, research in both humans and horses shows that hypotonic electrolyte solutions are absorbed more efficiently from the gastrointestinal tract (Lindinger, 2022).
This means concentrated electrolyte pastes or powders given without adequate water can actually slow gastric emptying and delay absorption. The practical implication: electrolytes must always be given with plenty of water.
How to supplement: timing and delivery
Research provides increasingly clear guidance on optimal timing and methods for electrolyte supplementation, though some controversy remains.
The case for pre-exercise loading
Recent research strongly supports giving electrolytes before exercise rather than waiting until afterwards. Waller and Lindinger’s (2021) study on pre-exercise electrolyte loading showed that horses given a large volume electrolyte solution approximately one to two hours before exercise maintained better fluid and electrolyte balance throughout work and recovery.
The mechanism makes physiological sense: the stomach and small intestine act as a reservoir for water and electrolytes. When horses consume electrolytes before work, the ions are rapidly absorbed in the small intestine and transported to muscles and skin, where they’re immediately available to replace sweat losses as they occur (Lindinger, 2022).
Practical application: for planned exercise or competition, offer electrolytes mixed in feed or dissolved in water one to two hours beforehand. This pre-loading strategy appears more effective than post-exercise supplementation alone.
During exercise
For prolonged exercise lasting several hours (such as endurance rides), offering electrolytes during work helps maintain balance. However, this requires horses to drink the electrolyte solution voluntarily, which raises an important consideration: palatability and training.
Many horses initially refuse water with added electrolytes due to taste. Research by Lindinger (2022) emphasises that horses can be trained to accept and even prefer electrolyte solutions, but this training must occur gradually during low-stress periods. Start with very dilute solutions and slowly increase concentration over weeks. By competition day, the horse should readily drink electrolyte water.
Post-exercise supplementation
Despite emphasis on pre-exercise loading, post-exercise supplementation remains valuable, particularly after prolonged intense work. Research shows that horses don’t fully replace electrolyte losses during exercise; continued supplementation for one to three days after intense work supports complete recovery (Integrity Horse Feed, 2025).
However, timing matters. Allow horses to drink plain water first after work, as they’re thirsty and will drink more readily without the taste of electrolytes. Once initial thirst is quenched (typically after 10 to 15 minutes), offer electrolytes in feed or as a separate supplement (Lindinger, 2022).
Delivery methods
Electrolytes are available as powders, pastes, and pellets. Each has advantages:
Powders: Most economical and flexible. Can be mixed in feed or dissolved in water. Allows precise dosing. The preferred form for routine supplementation.
Pastes: Convenient for competition when feed isn’t available or accepted. Ensures the full dose is consumed. However, pastes must be followed immediately by water as giving a concentrated paste without water can cause gastric irritation (Kentucky Equine Research, 2025).
Pellets: Easy to feed in measured amounts. Some horses prefer these to powder. Generally more expensive per dose.
Avoid adding electrolytes to the only available water source, as some horses will refuse to drink adequately, worsening dehydration rather than helping (Mad Barn, 2022). Always provide plain water alongside any electrolyte-supplemented water.
When supplementation can cause issues
While appropriate electrolyte use is beneficial, inappropriate supplementation can cause genuine harm. Understanding the risks allows you to avoid them.
The critical importance of water
Giving electrolytes without adequate water access is potentially dangerous. Electrolytes increase blood osmolality, triggering thirst. If a horse cannot drink, they experience uncomfortable thirst without the ability to satisfy it. More seriously, concentrated electrolytes without water were seen in some studies to draw fluid from the gut into the bloodstream, potentially contributing to impaction colic.
A study examining powder electrolyte supplementation during a multi-day trail ride found an increased risk of colic in supplemented horses, likely due to limited water access during riding (Walker et al., 2005). The research concluded that oral powder electrolytes should be used with caution when water isn’t freely available.
The absolute rule: never give electrolytes, in any form, unless the horse has free access to fresh water immediately before, during, and after supplementation.
Gastric ulcer concerns
Research by Holbrook et al. (2005) examined whether repeated administration of hypertonic electrolyte solutions could damage gastric mucosa. The study found evidence that concentrated electrolyte pastes given repeatedly without adequate buffering or dilution might contribute to gastric irritation in susceptible horses.
For horses with known or suspected gastric ulcers, electrolytes should be given mixed in feed or dissolved in water rather than as concentrated pastes. Some manufacturers now offer buffered electrolyte formulations specifically designed to minimise gastric irritation (Redmond Equine, 2024).
The risk of over-supplementation
While the horse’s body can excrete excess electrolytes through urine when adequate water is available, over-supplementation still carries risks. Excessive potassium, in particular, can cause cardiac arrhythmias in severe cases. High salt intake without corresponding water intake can lead to hypernatremia (elevated blood sodium), causing neurological signs (Horse and Rider, 2025).
Practically, this means following product feeding guidelines and not doubling doses ‘just to be safe.’ More is not better. If you’re unsure whether your horse needs supplementation, err on the side of providing salt and allowing the horse to self-regulate rather than force-feeding large amounts of electrolytes.
Loading before travel or competition
Despite marketing claims about ‘loading’ horses with electrolytes days before competition, this practice lacks scientific support and may cause problems. Chronic over-supplementation doesn’t create an electrolyte reserve; it simply forces the body to excrete the excess, potentially affecting fluid balance negatively (GAIN Equine, 2024).
Additionally, some sources advise against giving electrolytes 24 hours before travel when water availability might be limited, as this could contribute to dehydration if the horse can’t drink adequately during transport (Horse and Rider, 2025).
Practical guidelines for our conditions
Applying research findings to practical management in Southern Africa requires considering our specific conditions: intense summer heat, often low humidity, and varying levels of work.
Summer management
South African summers create conditions where even moderate work can produce significant sweating. During December through March, when temperatures regularly exceed 30°C, consider:
- Providing free-choice salt year-round, with particular attention to ensuring adequate intake during hot months.
- Supplementing electrolytes for any horse working more than 45 minutes in temperatures above 25°C.
- Offering electrolyte water alongside plain water after work to let the horse choose.
- Training horses during cooler months to accept electrolyte solutions, so they’ll drink them readily when needed.
Competition days
For competition, a science-based approach based on current research would include:
- One to two hours before competition, offer electrolytes in feed or dissolved in water (pre-loading).
- Ensure the horse drinks plain water freely before the pre-load electrolytes.
- Offer plain water immediately after competition.
- Provide electrolytes in evening feed after competition.
- Continue electrolyte supplementation for 24 to 48 hours after intense competition.
Individual variation
Remember that horses vary significantly in their sweat rates and electrolyte losses. Some horses are visibly drenched after moderate work; others barely show moisture. Heavy sweaters likely need more aggressive supplementation. Learn to recognise your individual horse’s patterns and adjust accordingly.
Signs of electrolyte imbalance
Recognising when your horse might be experiencing electrolyte depletion helps you respond appropriately. Warning signs include:
- Reduced performance or unusual fatigue during work.
- Decreased appetite, particularly for concentrate feed.
- Muscle cramps or tremors.
- Synchronous diaphragmatic flutter (thumps) – a sign of severe calcium and magnesium depletion.
- Reduced water intake despite work or heat.
- Decreased skin elasticity (though this indicates dehydration generally, not just electrolyte loss).
- Prolonged elevated heart rate during recovery.
If you observe these signs, provide electrolytes and water immediately and consult your veterinarian if signs don’t resolve quickly or worsen.
When to consult your vet
While routine electrolyte supplementation for horses in work can be managed by owners following evidence-based guidelines, certain situations warrant veterinary involvement:
- Horses showing signs of severe dehydration or electrolyte imbalance (thumps, severe muscle cramping, cardiovascular compromise).
- Horses with ongoing diarrhoea, as the electrolyte losses through diarrhoea can be massive and require veterinary assessment.
- Horses with known conditions that affect electrolyte balance (kidney disease, certain endocrine disorders).
- Uncertainty about whether your horse requires supplementation, as your vet can assess work level, sweat losses, and diet to provide tailored advice.
- Horses competing at high levels like endurance horses, three-day event horses, and racehorses benefit from veterinary oversight of their electrolyte management protocols.
The bottom line: evidence-based recommendations
Synthesising current research into practical guidance leads to these evidence-based recommendations:
- Most horses don’t need routine supplementation. Horses at maintenance or in light work get adequate electrolytes from forage plus free-choice salt. Don’t supplement ‘just in case’ – it’s unnecessary and potentially counterproductive.
- Horses in moderate to intense work benefit measurably from supplementation. If your horse sweats noticeably during work, particularly in hot weather or during work lasting over an hour, electrolyte supplementation supports performance and recovery.
- Pre-exercise loading appears more effective than post-exercise supplementation alone. Give electrolytes one to two hours before planned work, not just afterwards.
- Choose supplements with appropriate ratios and minimal sugar. Look for products that mirror the composition of sweat, avoiding those with high dextrose content.
- Water access is non-negotiable.Never give electrolytes without ensuring free access to fresh water. This is an absolute requirement, not a suggestion.
- Train acceptance gradually. Horses can learn to drink electrolyte water, but training takes time. Start well before you need them to drink it at a competition.
- More is not better. Follow product guidelines and don’t overdose. Excessive supplementation causes problems rather than preventing them.
Final thoughts
Electrolyte supplementation isn’t a one-size-fits-all proposition. While research provides valuable guidance on general principles, your horse’s individual circumstances – work level, sweat rate, climate, diet – determine whether and how much supplementation they need.
The evolution of research in this area demonstrates the value of updating practices as evidence accumulates. Pre-exercise loading, for example, is a relatively recent recommendation based on studies from the past few years. As our understanding continues to develop, recommendations may evolve further.
What remains constant is the fundamental principle: support your horse’s physiological needs based on their actual work and environmental demands, not on marketing claims or tradition. Observe your horse closely, understand the evidence behind supplementation, provide plain salt year-round, and supplement strategically when work intensity and environmental conditions warrant it.
In summary, when done thoughtfully and appropriately, based on science rather than guesswork, electrolyte supplementation is a valuable tool for supporting equine athletes.
References
GAIN Equine Nutrition. (2024). What are electrolytes and when should I supplement? https://www.gainanimalnutrition.com/equine/what-are-electrolytes-when-should-i-supplement/
Hartog Lucerne. (2024). Electrolytes for horses: when should you supplement? https://hartog.eu/en/articles/electrolytes-for-horses-when-do-you-supplement/
Holbrook, T.C., Simmons, R.D., Payton, M.E., & MacAllister, C.G. (2005). Effect of repeated oral administration of hypertonic electrolyte solution on equine gastric mucosa. Equine Veterinary Journal, 37(6), 501-504.
Horse and Rider. (2025). Electrolyte Supplementation. https://horseandrider.com/horse-health-care/electrolyte-supplementation/
Integrity Horse Feed. (2025). Electrolytes for horses: when and how to supplement. https://integrityhorsefeed.com/bray-electrolyte-supplementation-horses/
Kentucky Equine Research. (2025). Electrolytes and muscle function in horses: essentially linked. https://ker.com/equinews/electrolytes-and-muscle-function-in-horses-essentially-linked/
Lindinger, M.I. (2022). Oral electrolyte and water supplementation in horses. Veterinary Sciences, 9(11), 626. https://doi.org/10.3390/vetsci9110626
Lindinger, M.I., & Ecker, G.L. (2013). Gastric emptying, intestinal absorption of electrolytes and exercise performance in electrolyte-supplemented horses. Experimental Physiology, 98(1), 193-206.
Mad Barn. (2022). Best electrolyte supplements for horses: a how-to guide. https://madbarn.com/electrolytes-for-horses/
McCutcheon, J.L., & Geor, R.J. (1996). Sweat fluid and ion losses in horses during training and competition in cool vs. hot ambient conditions: Implications for ion supplementation. Equine Veterinary Journal, 28, 54-62.
Redmond Equine. (2024). Salt vs. electrolytes for horses: when to feed each and why. https://blog.redmondequine.com/should-i-give-my-horse-salt-or-electrolytes
Walker, W., Callan, R.J., Hill, A.E., & Tisher, C. (2005). Effects of oral powder electrolyte administration on packed cell volume, plasma chemistry parameters, and incidence of colic in horses participating in a 6-day 162-km trail ride. Canadian Veterinary Journal, 46(12), 1077-1082.
Waller, A.P., & Lindinger, M.I. (2021). Preloading large volume oral electrolytes: tracing fluid and ion fluxes in horses during rest, exercise and recovery. Journal of Physiology, 599(16), 3879-3896.
Zeyner, A., et al. (2017). [As cited in Kentucky Equine Research, 2025]