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The major electrolytes include sodium, potassium, chloride, calcium and magnesium. Even when your horse is resting, they lose electrolytes through faeces, urine and their breath. During exercise, electrolyte loss is increased through sweating. Sweating is how your horse regulates their body temperature, but the loss of fluids and electrolytes need to be taken into account when you are putting together your horse's diet. So we answer your questions and find out, does your horse need electrolytes?
What are electrolytes and why are they important?
There are times of the year when it is warmer weather and your horse will sweat even more during exercise. The amount of sweat your horse loses depends on a number of factors, including weather conditions, air movement, fitness level and temperament. As a guide, a horse doing moderate exercise for an hour will lose in the region of five litres of sweat and a horse that is dripping with sweat may have lost up to 18 litres. Below is a table from a research study conducted to estimate sweat loss by assessing sweat patterns on different areas of the horse.
How much can horses sweat?
| Sweat Score | Sweat Pattern | Total Sweat Loss |
| 1 | The area under the saddle is partly dry, partly dark, sticky, and moist. The throat area is sticky, and the flanks are darker than normal.
| 1 – 4 litres |
| 2 | The area under the saddle and the throat are both wet, there are small white areas at the edges of the saddle corners, and foaming may occur at sites of friction between the throat and reins and between the limbs.
| 4 – 7 litres |
| 3 | There is foam on the back of the bridle and noseband, the flanks are clearly wet, and the area under the saddle and girth are consistently wet.
| 7 – 9 litres |
| 4 | The throat and flanks are completely wet, above the eyes are moist and have dark wrinkles, and there is pronounced foaming between the limbs.
| 9 – 12 litres |
| 5 | The horse is actually dripping fluid above the eyes and under the belly.
| 12 – 18 litres |
Source: Zeyner et al. (2014). Scoring of sweat losses in exercised horses – A pilot study. Journal of Animal Physiology and Animal Nutrition 98: 146-50.
Does my horse need electrolytes?
If your horse is in work then the answer to this question is yes. Commercial feed mixes and forage do contain electrolytes, but only in amounts that are adequate for horses at maintenance or in light work. In particular, the one electrolyte most likely to be deficient is sodium (salt). Therefore, a horse that is doing anything other than light work will not have its electrolyte requirements met without supplementation.
One thing to bear in mind is that horses do not regulate their intakes from salt blocks; for example, if a horse needs 30g of salt per day there are some horses that will not use the salt lick at all and others that will consume much more salt than they require, even up to four times more! Therefore, it is much better to add electrolytes to your horse's feed or by syringe. Adding electrolytes to water also makes it difficult to know how much electrolytes your horses in consuming and so it is difficult to make sure you are meeting your horse’s electrolyte requirements by adding them to drinking water.
How many electrolytes should I feed and when?
The amount of electrolytes needed depends on diet, time of year, level of work. For horses in work, electrolytes should be fed every day. One litre of horse sweat contains approximately 3.5g of sodium, 6g of chloride, 1.2g of potassium and 0.1g of calcium. Therefore, for five litres of sweat loss following an hour of moderate exercise your horse needs approximately 50g of electrolytes. It is best to feed electrolytes every day, it is often the case that horses are only fed electrolytes around a specific competition; however, if enough electrolytes are fed each day then it is unlikely that additional supplementation will be required during competition.
It can take a long time (weeks or months) to replenish electrolyte levels and so feeding just before and after competing is not recommended, it is much better to feed an electrolyte supplement every day.
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Can I feed too many electrolytes?
If you are feeding according to the manufacturer’s guidelines it is unlikely that you will be over supplementing electrolytes. Generally, horses are under supplemented rather than over supplemented. Signs of over supplementing are drinking more water and urinating more. If an electrolyte paste is given then it is not the case that this will dehydrate the horse by drawing electrolytes into the gastrointestinal tract. An electrolyte paste will pull water into the gastrointestinal tract, but what this does is increase the concentration of electrolytes in the horse’s blood triggering the horse to drink.
When this does become a problem is if an electrolyte paste is given and the horse is not provided with free access to water. As a guide, a 500kg horse being exercise moderately in cool to warm weather will drink around 30 litres in two hours.
Overall recommendations:
- Most horses would benefit from having electrolytes daily
- Horses at maintenance or in light work may only need a small amount of salt added
- Horses in moderate work will require additional electrolyte supplementation
- Electrolytes should be fed according to the level of work and weather conditions
- Feed electrolytes daily during training and not just around competition
A rider's view:
"I use the Cool It Paste before dressage as it helps to keep my horses calm and focused without losing the presence they need to perform a good test and I feed Restorelyte powder to my competition horses on a daily basis to help maintain a balanced level of electrolytes. I then give a Restorelyte gel following a competition to speed up the recovery process. This means that my horses recover faster and are therefore able to compete on a more regular basis.”
Emma Hobday, International Event Rider
Thank you to Equine Products UK and Professor Jo-Anne Murray for providing the information in "Does my horse need electrolytes?"