Forageplus discusses how to understand what levels of electrolytes/minerals you need to feed to horses. Electrolytes for horses are important when a horse sweats or eats forage that is short of electrolyte minerals. Poor levels and imbalance of electrolytes for horses can cause a range of issues, which can be detrimental to health and performance.
So, how is it best to support your horse with the electrolyte minerals it needs? What are electrolytes for horses? Do you need an electrolyte supplement for your horse, and why pay attention to the amounts in your forage?
What are Electrolytes for Horses?
Electrolytes for horses are essential minerals that play a key role in various bodily functions. Electrolytes are minerals that exist in the body in their free, ionised form, carrying an electrical charge. They include cations like calcium, magnesium, potassium, and sodium, and anions like chloride, bicarbonate, and sulfate. These electrolytes are crucial for various bodily functions such as muscle contraction, nerve firing, and heart beating.
Quick Summary
- Sodium is the electrolyte most likely to be deficient in UK forage.
- Electrolyte imbalance can reduce hydration, recovery and performance, even in lightly worked horses.
- Most horses already receive sufficient potassium from forage and do not require high potassium supplementation.
- Salt is often the most important electrolyte supplement for horses that sweat.
- Forage analysis removes guesswork and allows electrolyte supplementation to be matched accurately to the horse’s diet.
- Many commercial electrolyte supplements contain unnecessary ingredients when simple salt replacement may be more appropriate.
How do electrolytes affect the horse’s body?
If the sodium concentration in the blood increases in relation to water, the brain will send out the message to drink. However, if sodium content in the body is not what it should be to begin with, blood concentration will not increase enough to trigger drinking even if there is a significant reduction in body water (dehydration).
Electrolyte imbalances can lead to dehydration. Since sodium lost in the sweat is needed to hold water in the body tissues, drinking water alone is not enough to correct the dehydration. Even mild dehydration has a major impact on the ability to perform.
In the body, negatively charged chloride and bicarbonate normally balance out positive charges. When chloride becomes too low, more bicarbonate is produced. The bicarbonate then binds up “free”/charged calcium and magnesium ions, which in turn disrupts muscle and nerve activity.
Sodium is the major electrolyte for horses that holds water in the body and is read by the horse’s brain to determine whether to drink more water. Sodium is vital for many cellular processes, including muscle contraction. This mineral is involved in the movement of glucose into cells. Glucose is then metabolised in the mitochondria, which are the powerhouse of the cell, to produce energy.
When your horse is low in sodium, this mineral is drawn into the bloodstream to maintain concentration and balance. This means that less glucose can be transported into the cell, and this is when you might see lethargy and tiredness in your horse. As sodium commonly shows up as being low in UK forage, then this electrolyte can have a high impact on the performance of a horse in even light work.
Low blood potassium is more common than low sodium. This is because the body can pull sodium from the tissues surrounding the body’s cells to keep blood levels up. The kidney also conserves sodium by reducing sodium in the urine and replacing it with potassium. Low blood potassium interferes with the normal contraction of intestinal muscles, skeletal muscles, and the heart. The loss of chloride also worsens these changes.
Given the importance of electrolytes for horses, it’s crucial to ensure that horses have a balanced intake of all the electrolytes, as matched to forage, especially when they are being worked regularly or in hot weather. If you suspect your horse has an electrolyte imbalance, it’s advisable to analyse the grass and hay your horse eats so you can determine the amount of deficiency you need to correct.
Sodium and Horse Dehydration
Where a shortfall of sodium occurs at low levels of work or even at maintenance, then the body will always be playing catch-up. Sodium is the major controller of water balance in tissues, so low levels in the horse’s diet are likely to lead to the horse drinking less water and becoming dehydrated.
Some horses can effectively be dehydrated for years due to low levels of sodium in the main forage portion of their diet. You may see this as wrinkling of the skin, especially over the hindquarter area, as they walk. A pinch test can also be used in the neck area to check the elasticity of the skin and see how quickly it rebounds after it is pinched.
Sodium is what the brain ‘reads’ in determining when to trigger thirst and when to regulate the amount of sodium and water the body excretes in the urine, this is why a shortage of sodium is likely to lead to less drinking of water as the body tries to balance the amount of sodium needed to maintain homeostasis in the blood.
The pinch test seen used in endurance competitions is where the vets are essentially looking for a sodium deficiency. Dr Eleanor Kellon VMD, a leader in equine nutrition, reports that as little as 2 to 3% dehydration can lead to a 10% drop in performance.
The interesting thing is to ponder how many endurance or eventing competitors have analysed their forage to see what levels of sodium are contained in that which is the greatest proportion of their horse’s diet. Most competitors leave this vital part of the performance jigsaw to chance, guessing on the amounts of sodium and other electrolytes for horses and how much will be needed to maintain levels during periods of extreme performance.
Perhaps feeding a proprietary electrolyte supplement may or may not hit the right amounts. Where sodium levels are adequate then guessing the amount may well avoid the dreaded drip at the end of an endurance race, but for the horses which run low on sodium, we suggest that low levels in forage are the culprit and that simple analysis of that forage could support and maintain healthy levels of electrolytes for horses by leaving nothing to chance or guesswork.
Chloride: an electrolyte for horses
Chloride is a critically important electrolyte for horses. It plays a key role in various bodily functions, including maintaining acid-base balance and orchestrating various reactions in the body. Chloride is also lost in the highest amounts in sweat, especially for horses that are working several hours in hot conditions, whether endurance racing or just trail riding.
Forage seems either to be very well supplied with chloride or very poorly supplied. Where your horse’s forage is in the poorly supplied category, guessing how much your horse needs may well lead to a reduction in performance when your horse starts to sweat due to heavy work. Horses lose around 21 grams of chloride per hour even at low levels of sweating.
Potassium: an electrolyte for horses
Potassium is another vital electrolyte for horses, playing a crucial role in various bodily functions such as nerve impulse transmission, muscle contraction, and maintaining the body’s fluid balance.
Potassium is the major electrolyte inside a cell, but is very well supplied in grass, hay and haylage. Normally, it is so well supplied that unless your horse is competing in lengthy endurance rides, extra supplementation is not required.
Important Practical Insight
Most UK hay and grass already supply large amounts of potassium. For many horses, additional potassium supplementation is unnecessary unless prolonged heavy sweating is occurring.
The forage our horses eat, for example, supplies enough potassium for 5 hours of constant heavy sweating, so we have never had to supplement extra, as we have never exceeded this 5-hour point. However, it is always wise, if you are demanding high levels of continued exertion from your horse, to analyse the forage eaten so you take the guesswork out of supplementation.
The difference in sodium and potassium concentrations outside and inside cells is responsible for the excitability of muscle and nerve tissue, so getting the ratio between these two minerals correct by feeding adequate sodium is important. If potassium is deficient (which is very rare in a horse on a forage-based diet), symptoms can include fatigue, heart rhythm irregularities, muscle weakness or tying up (Rhabdomyolysis) and nerve irritability, also known as ‘Thumps’.
Sweating and Electrolytes for Horses
Horses primarily regulate their body temperature through sweating, losing a significant amount of water and electrolytes in the process.
During moderate exercise, horses can produce up to 15 litres of sweat per hour. The volume and composition of their sweat depend on exercise intensity, ambient temperature, humidity, diet, and their adaptive response to the environment.
According to one study, an hour of sweating, at a rate of 15 litres per hour, results in the following electrolyte losses:
| Electrolyte Lost Per Hour of Heavy Sweating | Approximate Loss |
|---|---|
| Chloride | 105g |
| Sodium | 60g |
| Potassium | 30g |
| Calcium | 4.5g |
| Magnesium | 1.5g |
These losses can occur in just one hour of moderate to heavy sweating.
Excessive sweating can lead to heat exhaustion and dehydration, causing fatigue and diminished performance. In severe cases, dehydration can be life-threatening.
What are the Common Signs of Electrolyte Imbalance in Horses?
Electrolyte imbalances can affect hydration, performance, muscle function and behaviour. Common signs may include:
Hydration Signs
- Dehydration — skin may remain tented after a pinch test.
- Changes in drinking or urination — drinking excessively, drinking too little, or altered urination patterns.
- Increased risk of heat stress — especially during exercise in warm weather.
Performance Signs
- Reduced performance — fatigue, lethargy, reduced stamina or poor recovery.
- Weakness — difficulty maintaining normal energy levels or exercise tolerance.
- “Hitting the wall” — sudden loss of energy during work or competition.
Muscle & Nerve Signs
- Muscle cramping or tremors — signs of discomfort, tightness or twitching.
- “Thumps” — rhythmic contractions of the diaphragm linked to electrolyte disturbance.
- Heart arrhythmias — abnormal heart rhythm detected by a veterinarian.
- Neurological signs — severe imbalance may lead to disorientation, weakness or seizures.
Behaviour & Digestive Signs
- Soil licking or chewing wood — horses may seek minerals instinctively.
- Excessive salt block use — persistent licking or chewing may suggest deficiency.
- Colic or reduced gut sounds — electrolyte imbalance can affect gut motility.
Important: These signs can vary depending on which electrolyte is imbalanced and how severe the deficiency is. If you notice persistent symptoms, consult your veterinarian and consider analysing the forage your horse consumes to identify potential deficiencies more accurately.
If you notice any of these signs in your horse, it’s advisable to consult with a veterinarian for an accurate diagnosis and appropriate treatment plan.
What electrolyte levels does my horse need?
The National Research Council (NRC), in the current 6th revised edition of Nutrient Requirements of Horses (2007), gives the following calculations to determine maintenance requirements based on body weight (BW) for electrolytes for horses:
Sodium; 0.02 x BW
Chloride: 0.08 x BW.
Using the above figures, a 450 kg horse requires 9 grams of elemental sodium and 36 grams of elemental chloride per day for maintenance. Note that these are minimum levels and do not take into account sweat losses on a hot day or through exercise.
Are there enough electrolytes for horses in forage?
Our statistical analysis of forage has shown that, on average, horses often obtain far less than 9 grams of sodium per day through the forage they eat. Sodium is the electrolyte mineral which is most likely to impact horses, although chloride can also be low in some samples of grass and hay.
Half the samples we test at Forageplus have levels of sodium which are too low to support maintenance levels. This is an important fact to know and recognise as a horse rider exercising horses which sweat.
A forage analysis, like the one shown above, will allow you to balance the diet to the common mineral deficiencies found in the forage eaten, covering all minerals and, of course, the electrolytes for horses.
Over 80% of the forage we sample shows levels of potassium and chloride which will cover maintenance needs. Statistically, potassium is always at a level to expect electrolyte losses from 4 hours of constant sweating to be covered. Levels of sodium, however, are likely to be low and often fail to cover a 450 kg horse’s maintenance needs of 9 grams of sodium per day.
The particular analysis shown will be low in both sodium and chloride for maintenance levels, supplying a 450 kg horse just 7.9 grams of elemental sodium and 30.2 grams of elemental chloride when fed at 2% of body weight per day.
Forage Analysis vs Guesswork
When it comes to electrolytes for horses, guessing can easily lead to under-supplementation, over-supplementation, or unnecessary products. Forage analysis helps you understand what your horse’s diet is actually supplying.
| Guesswork Feeding | Forage Analysis Feeding |
|---|---|
| Generic electrolyte supplementation | Targeted supplementation based on measured forage levels |
| Unknown sodium and chloride intake | Known sodium and chloride supply from hay, haylage or grass |
| Risk of not replacing sweat losses accurately | Salt levels can be matched to maintenance and work requirements |
| Possible unnecessary potassium supplementation | Potassium can be assessed before adding more |
| Performance and hydration left to chance | Evidence-based feeding for hydration, recovery and performance |
Key takeaway: Forage analysis removes the guesswork and shows whether your horse needs extra salt, broader electrolyte support, or no additional electrolyte product beyond a balanced diet.
What is the best form of electrolyte supplement for horses?
Once this horse begins to sweat, then a shortfall will occur, which needs to be supplemented to maintain optimum health and performance. This hay would require 10 grams of salt to be added each day to the bucket feed, and if one hour of constant sweating occurred, 49 grams of salt in addition to the 10 grams of salt for maintenance to cover the losses of sodium and chloride. Plain table salt, or rock or sea salt, can be used and just bought cheaply from the supermarket.
Potassium is still well supplied for maintenance and unlikely to be too low in the diet for the levels of sweating that are common here in the UK. According to the NRC (National Research Council), the maintenance requirement for potassium is 0.065 grams per kilogram of body weight. This hay will supply 4.2 times the level of potassium needed for maintenance.
For a horse doing intense work, the requirement increases. For example, a 450 kg horse doing intense work would require about 40 grams of potassium per day. As 2% bodyweight of this hay supplies 96.2 grams of potassium, then the hay supplies all the potassium the horse needs at this level of sweating.
It is important to understand that most UK and European hays contain a minimum of 1% potassium (most are significantly more than this), which means just 1 kg provides 10 grams, and as little as 4 kg of hay will meet or exceed the potassium needs of a horse at work. Therefore, a horse’s diet usually provides sufficient potassium, and supplementation is not usually necessary.
How much salt do I need to cover electrolytes for horses?
To cover electrolytes for horses lost through sweat, a good guide is feeding 30-50 grams of salt per hour of heavy sweating. This would be a wise guide if you are unable to test the electrolyte mineral levels of the hay, haylage or grass your horse eats. You can supplement salt easily with a small amount of feed after the horse has drunk.
Adding a small amount of a high-oil feed, such as micronised linseed or copra, to the bucket feed will help to protect the stomach if a high level of salt is needed. A level 25 ml scoop of salt contains approximately 9 grams of sodium and 14 grams of chloride.
If you cannot carry out a forage analysis, then feeding a forage-focused mineral balancer is wise. The balancer should target only those minerals which are commonly deficient, as matched to ratios. This means that your horse will have access to the right amounts of minerals to maintain health without excess minerals acting to block uptake.
Some people might prefer to feed rock or sea salt to avoid the flow enhancers added to table salt. In the UK, 5 grams of salt is a low statistical average (taken from our thousands of forage analyses) to add to horses’ feed to cover maintenance electrolyte requirements if you cannot test the forage. This is the amount in 100 grams of our balancers; we double this amount to 10 grams in the Performance Balancer.
Any excess of sodium and chloride, if your forage is well supplemented with sodium (uncommon) or chloride (more common), is easily and efficiently excreted from the kidneys. Of course, ample drinking water should always be provided at all times so that horses can hydrate themselves sufficiently.
Is an electrolyte salt lick enough?
You should provide a salt lick in addition to supplementation of salt each day. However, do not rely solely on a salt lick to provide electrolytes for horses. A measured amount is needed either for maintenance or replenishment of those lost through sweating.
There are two good reasons for this. One, it is guesswork as to how much a horse can lick from a salt lick, and two, some horses won’t touch salt licks even though they may be short in electrolytes for horses.
Adding salt to a feed will ensure you know your horse has sodium and chloride needs covered. Use forage and mineral balancing to check potassium, calcium and magnesium levels or feed a forage-focused balancer.
Pay close attention to salt levels to get the best horse performance.
Real-World Example: Hydration & Endurance Performance
A few years ago, we had an interesting experience on the importance of getting electrolyte balance right, as matched to the forage eaten, with our Arab, CSA Mahrice, who was competing in his first year of endurance with EGB. We were feeding minerals balanced to our forage and had calculated electrolyte losses as matched to the sweat losses for moderate work.
As the season progressed, Moo gained grade one after grade one. However, at one ride he gained a grade of 2 and took half an hour to start drinking after the race, he also got a dehydration score of 1. Fairly normal, you might think if you are an endurance rider, but we weren’t happy as something was wrong if he wasn’t drinking.
The problem: After checking the calculations again, it became clear that sodium replacement had been too low for the actual level of work and sweating.
After going back to our calculations and checking them, it was apparent that we had not been accurate enough and that the replacement of sodium, in particular, had been too low. Dr Kellon advised us to load with sodium for two weeks at 100 grams of salt per day to replenish the low levels, which had occurred due to insufficient replenishment after sweating.
The result: At the next ride, Moo passed urine twice during the 42 km ride, drank during the ride, drank immediately after finishing, gained a grade 1 again and had no dehydration score.
The next ride we competed in was two weeks later, and he not only passed urine 2 times during the 42 km ride (an indication of good hydration and something he hadn’t done before) but he also drank during the ride from streams and troughs and immediately on finishing the race. He got a grade of 1 again and no dehydration score.
For the rest of the season, we paid close attention to mineral and electrolyte levels at the correct work level of heavy and had no further dehydration scores and grade 1 levels. We didn’t use anything fancy as an electrolyte supplement, just plain old table salt you can buy from the supermarket, fed at levels matched to minerals in our forage and heavy sweat losses.
Our Forageplus top tip is to know, not guess, what electrolytes for horses you need and supplement the appropriate level of salt to maintain health and high performance no matter what your horses’ discipline.
Need Help Balancing Electrolytes For Your Horse?
Every horse, forage source and workload is different. The most effective electrolyte strategy is one based on understanding what your horse’s forage already supplies and where genuine deficiencies may exist.
At Forageplus, we use forage analysis and scientifically formulated mineral balancing to help horse owners build more accurate, forage-focused feeding plans tailored to the individual horse.
Summary: Key Takeaways on Electrolytes for Horses
Maintaining correct electrolyte balance is essential for hydration, muscle function, recovery and long-term performance. The key is understanding what your horse’s forage already supplies and supplementing appropriately rather than relying on guesswork.
Understand The Key Electrolytes
Sodium, chloride and potassium are essential for hydration, nerve function, muscle contraction and recovery.
Focus On Sodium
Sodium is the electrolyte most likely to be deficient in UK forage and plays a major role in thirst response and hydration.
Most Horses Already Get Enough Potassium
Forage usually supplies ample potassium, meaning additional supplementation is often unnecessary outside prolonged heavy sweating.
Salt Matters More Than Most Realise
Simple salt is often the most important electrolyte supplement for horses in work or sweating heavily.
Analyse The Forage
Forage analysis removes guesswork and allows electrolyte supplementation to be matched accurately to the horse’s diet.
Avoid Over-Supplementation
Adding unnecessary electrolyte products can be wasteful and may disrupt balance if the horse’s actual requirements are unknown.
Forageplus Top Tip: Know, don’t guess. The most effective electrolyte strategy is one matched to the forage your horse actually eats.
Need Help Balancing Your Horse’s Diet?
Our equine nutritionists can help you understand your forage analysis and build a forage-focused feeding plan tailored to your horse.
By following these guidelines, you can maintain your horse’s health and high performance across various disciplines.
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