It is easy to become confused about electrolytes. The mere name conjures up an image of science labs and sterile solutions with exotic formulations. Certainly there are mountains of information available on the function and interaction of electrolytes, but much of that information has little or no application in every day horse feeding.
What are electrolytes?
Electrolytes are substances (similar to minerals) that dissociate in solution into charged particles called ions. These substances act in solution to preserve the balance of fluids within the body and are important for the correct functioning of nerves and muscles. If there is a shortage of electrolytes,
the horse will feel fatigued and weak. It will also feel LESS like drinking if dehydrated. The most important electrolytes for a working horse are sodium (Na+), Potassium (K+), chloride (Cl-) and magnesium (Mg++). These electrolytes are lost in sweat and urine.
Combine sodium and chloride and you have common salt while potassium is sold as light salt.
Hence electrolyte replacement should occur as close as possible to the time of stress/sweat loss to be effective.
How much does a horse need?
The horse’s primary method of heat loss is evaporative i.e. it loses sweat which is cooled and evaporates from the surface of his skin. Horses working under hot/humid conditions can lose as much as 10 – 15 litres of sweat per hour. The following table shows the makeup of electrolytes in that sweat.
From this table, it is easy to calculate the estimated total electrolyte loss of 170 grams that would result from a daily work out in a hot/humid climate involving a sweat loss of 10 litres.
This knowledge would also help you appreciate that no supplement containing a single electrolyte could be expected to replace that amount of salts.
When humans sweat they lose a lot of water and salt concentrates in the body, stimulating thirst.
In horses, sweat is quite high in electrolytes and as a result sodium is lost in a proportional amount to water.
Therefore, in the heavily sweating horse, plasma
odium concentrations may not increase and the "signal" for drinking is not produced.
This is part of the key as to why supplementing potassium disproportionately to sodium, i.e. the outdated concept of acid and alkaline electrolytes, is not as effective as more approximating the losses in actual sweat.
It is important to base any electrolyte programme over an existing allowance of sodium chloride. Approximately 50 grams per day is advisable for a working horse in a hot climate.
The most appropriate way to choose a product is to compare the electrolyte content of the supplement to
the electrolyte content of sweat.
If economy is a concern, the supplement should be evaluated on the basis of $/units of actual electrolytes, not $/unit of supplement, since some supplements may contain "filler" ingredients. Electrolyte administration will be most effective if the horse is actively drinking.