Essential Understanding on Electrolytes for Horses

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.

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.

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:

• 105 grams of chloride
• 60 grams of sodium
• 30 grams of potassium
• 4.5 grams of calcium
• 1.5 grams of magnesium

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

Common signs of electrolyte imbalances in horses can include:

1. Dehydration: This can be detected through tests like the skin pinch, where the skin stays tented for a few seconds after being pinched and released.
2. Soil licking or eating: Many horses know they are missing something in the diet, so they will search by eating or licking soil. Sometimes they might lick metal or chew wood.
3. Excessive use of a salt block: All horses should have access to a salt block, but where they are constantly licking, chewing or biting at this block, it is likely to be indicating an insufficiency in the total diet.
4. Reduced Performance: The horse may show signs of fatigue, lethargy, depression, reduced speed, and endurance.
5. Muscle Cramping: The horse may exhibit signs of discomfort or pain, and there may be visible muscle tremors.
6. Colic or Poor Gut Sounds: Changes in gut motility can lead to discomfort and changes in eating habits.
7. Weakness: The horse may appear lethargic or have difficulty standing or moving.
8. “Thumps”: This is a contraction of the diaphragm with each heartbeat, which can be seen or felt on the horse’s flank.
9. Heart Arrhythmias: Irregular heart rhythms can be detected by a veterinarian through a physical examination.
10. Changes in Drinking and Urination: The horse may drink excessively or not enough, and there may be changes in the volume or frequency of urination.
11. “Hitting the Wall”: This is a term used to describe a state of sudden fatigue and loss of energy, which can occur in severe cases of electrolyte imbalance.
12. Risk of Heat Stroke: Exercising a horse with suboptimal salt and water levels greatly increases the risk of heat stroke.
13. Neurological Signs: In severe cases, electrolyte imbalances can lead to neurological signs such as disorientation, decreased spinal reflexes, seizures, and even coma.

It’s important to note that these signs can vary depending on the specific electrolyte that is imbalanced and the severity of the imbalance. 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.

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.

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.

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 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.

Summary

In summary, preventing electrolyte imbalances in horses involves a combination of proper diet, hydration, and supplementation. To ensure you supply the necessary electrolytes for horses, for optimal health and performance, consider the following key points:

• Understand the Importance of Electrolytes: Sodium, chloride, and potassium are essential for hydration, muscle function, and nerve conduction.
• Focus on Sodium: Sodium is critical for water balance and cellular functions. UK forage often lacks sufficient sodium, leading to potential dehydration and performance issues. This is the electrolyte mineral most likely to be deficient.
• Adequate Salt Intake: Ensure your horse has a baseline salt requirement met. If you need help, contact Forageplus for free advice.
• Balanced Diet: Feed your horse a mineral adequate diet with at least 1.5% bodyweight of hay per day (if not grazing). This helps ensure the necessary nutrients are available as electrolytes for horses from their food.
• Conduct Forage Analysis: Regularly analyse your horse’s forage to identify mineral deficiencies and avoid guesswork in supplementation.
• Supplement Appropriately: For horses in heavy work, supplement with salt post-exercise to replace sweat losses, ensuring proper hydration and electrolyte balance.
• Monitor Hydration: Use methods like the skin pinch test to check for dehydration, and ensure ample drinking water is always available.
• Timed Hydration: Always let your horse drink freely and as much as they want during exercise lasting longer than 2 hours, and also immediately after stopping work. Research has shown that horses who have their access to water restricted while cooling off do not drink as much in total as horses with unrestricted water access.
• Consider a Mineral Balancer: If forage analysis isn’t feasible, use a forage-focused mineral balancer to provide essential electrolytes for horses and maintain health.
• Avoid Reliance on Salt Licks Alone: Supplement salt directly into the feed to ensure your horse meets its sodium and chloride needs. However you feed salt, it is vital to monitor how much the horse actually eats.
• Avoid Over-Supplementation: Over-supplementation can be pointless or even potentially harmful. When water is in short supply in the body from sweat losses, throwing electrolytes at it may only make things worse.

Remember, each horse is unique and may have different requirements depending on the levels of electrolyte minerals available in forage. By following these guidelines, you can maintain your horse’s health and high performance across various disciplines.

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