Salt and electrolytes for horses

“Electrolytes” is a collective term, and that is exactly where the confusion starts. Behind it are mainly three substances – sodium, chloride and potassium – which behave completely differently in feeding. Two of them are normally present in abundance. Only one regularly runs short.

That is why a clear distinction helps: your horse needs a source of sodium all year round. It only needs an electrolyte product beyond plain salt when it is genuinely sweating a lot. Marketing likes to merge these two statements into one – wrongly.

Basic supply according to Coenen/Vervuert

For adult horses, we calculate the basic supply of sodium, chloride and potassium according to Coenen/Vervuert based on metabolic body weight. Per kg body weight to the power of 0.75, that is 0.187 g sodium, 0.235 g chloride and 0.203 g potassium per day.

For 500 kg, this gives around 19.8 g sodium, 24.8 g chloride and 21.5 g potassium. For 600 kg, it is around 22.7 g sodium, 28.5 g chloride and 24.6 g potassium. Sweat at rest is already accounted for in this basic supply and is not added a second time.

This calculation applies to adult horses at maintenance and in work. Breeding and growth remain outside this change and belong in specialist advice.

Forage and the usual concentrates often supply little sodium. That is why a measured salt source is not a purely seasonal measure but part of the plannable basic supply.

Chloride and potassium: almost always covered

Chloride is well absorbed in horses and efficiently reabsorbed by the kidneys. In forage-based rations it is often already present in abundance, but with significant sweat losses the requirement rises further.

Forage usually supplies plenty of potassium. The additional losses during work are real, but with a typical hay ration they often remain covered by the forage. That is why the salt module contains sodium chloride and no blanket potassium addition.

What sweat actually costs

Horse sweat contains a lot of sodium, chloride and potassium. For the requirement calculation, an additional 4.0 g sodium, 5.5 g chloride and 1.6 g potassium are allowed for each litre of exercise sweat.

These exercise values are added to the basic supply. For a 600 kg horse, this gives around 34.7 g sodium for light work, 50.7 g for moderate, 78.7 g for heavy and 106.7 g for very heavy work.

For calcium and magnesium, on the other hand, there is no work-related allowance. A blanket additional requirement for all minerals cannot be derived from heavier sweating.

A salt lick is an offer, not a dose

This is the point with the greatest practical consequences in this article. Horses voluntarily take in very different amounts of salt: in a long-term measurement over up to 45 weeks, intake ranged between 19 and 143 g per day. Some took in nothing at all. In a study of six sport horses, the range was from 0 to 62 mg per kg body weight per day.

The form of presentation is not the reason: a comparison of salt lick and loose salt in 16 horses found no effect of the form, but a clear effect of the individual animal. Intake ranged from 2 to 135 g per day, and over half of the horses took in less than their requirement would have called for.

When a product can do more than salt

An electrolyte product makes sense where really large amounts of sweat are lost and replacement is to take place immediately around the exercise. Anything that can be planned over days can be covered with measured table salt in the feed.

Two things are worth checking on the label. First, osmolarity: oral solutions should be hypotonic. A target of around 200 mOsm/l is given, because higher concentrations can inhibit gastric emptying. Second, the sugar content. Whether dextrose improves absorption has not been conclusively settled.

The simple arithmetic behind it remains: the more sugar a product contains, the less electrolyte there is in the same serving. If dextrose or glucose is near the top of the composition, you need a larger serving for the same amount of sodium.

The method of administration determines the risk

There are two controlled studies on electrolytes and the stomach lining that seem contradictory at first glance – in fact, they examine two completely different practices.

In one, 14 horses received 56.7 g of electrolyte powder in just 60 ml of water by oral syringe every hour for eight hours; the number and severity of lesions in the non-glandular part of the stomach increased. In the other, 15 stallions received 600 g of salt pellets daily with their feed over two periods of 19 days, without clinically relevant negative effects on the stomach lining.

So the statement that can be supported is not “electrolytes harm the stomach”, but: highly concentrated, repeated and given without feed by syringe is something different from measured salt in the feed bucket. A high salt dose needs a reason; it should not be a habit.