Some minerals are also called electrolytes. This is because when dissolved in body fluids they carry an electrical charge. It is this electrical charge that helps to regulate water balance in the horse.
Complex homeostatic mechanisms control water and electrolyte balance to avoid dehydration or, rarely, over-hydration.
Severe dehydration can be very serious. However, even mild dehydration can result in loss of performance and increase the risk of issues such as tying-up and colic.
Electrolytes also play a vital role in muscle and nerve function and, through their role in hydration, both temperature regulation and the transport of nutrients and waste products throughout the horse’s body.
The most significant electrolytes are sodium, potassium and chloride, with calcium and magnesium playing a smaller role. While phosphate acts as an electrolyte, there should always be sufficient in feed to meet requirements.
A horse is more than 65% water, and even at rest a 500kg horse needs approximately 20-25 litres per day to maintain hydration. Water requirement can easily double in hot weather to replace water lost via sweating. The water can come from forage and feed as well as liquid water.
Electrolytes, mainly salt (sodium chloride) are needed to maintain good hydration status. The main way salt, together with the other electrolytes, is lost from the horse’s body is through sweat. In particular the loss of sodium through sweat can easily exceed the intake of sodium through the diet.
One of the important mechanisms that allow horses to regulate their body temperature is evaporation of sweat. It allows them to dissipate the significant heat generated by the muscles during work.
Latherin is the soapy protein in sweat that causes sweat to foam. It allows sweat to readily disperse over the horse’s coat to maximise evaporation and in turn heat loss.
The amount of sweat lost by a horse is affected by the intensity and duration of exercise, his fitness, and the prevailing humidity.
Equine sweat contains significant amounts of electrolytes, at a slightly higher concentration than in blood. Each litre of sweat contains about 3.5g of sodium, 5.6g of chloride and 1.2g of potassium, plus traces of calcium, magnesium and phosphate.
In medium work and moderate environmental conditions, a 500kg horse can lose about five litres of sweat per hour, containing about 17g sodium, 28g chloride and 6g potassium.
Even if he sweats considerably less than this, he will probably need either salt or a commercial electrolyte preparation added to his feed.
If he is receiving ad-lib forage (which is rich in potassium) salt may well be sufficient. However if he is offered, or eats, less than 2% of his bodyweight as dry weight of forage daily (this would be about 11kg hay ‘as fed’ for a 500kg horse) then electrolytes should be added his diet.
However, a two-star 16.2hh eventer who sweats freely will need more than the salt provided by his ad-lib forage, and 3-4kg of balancer and blend.
He may well need access to a salt-lick 24 hours a day plus added salt in his feed, plus an added commercial electrolyte preparation for at least 48 hours following heavy sweating and competing.
WHEN TO USE
Commercial electrolyte preparations always provide less sodium than plain salt; this is because they contain other electrolytes and also a product to enhance palatability, usually sugar.
Therefore, commercial electrolyte preparations should always be fed on top of any salt added to the feed, not instead of the salt.
A rare exception to this is for those few horses that dislike the taste of salt, then commercial electrolyte preparations become valuable.
For example, a 14.2hh jumping pony that is on a calorie-controlled diet to manage weight during the summer that rarely uses his salt lick and dislikes salt being added to his feed would benefit from the addition of a commercial electrolyte preparation daily.
It is always best to consult an experienced nutritionist to determine when and how much salt or commercial electrolyte preparation should be added to your horse’s feed but as a guide a 500kg horse in light-medium work, sweating lightly, could safely have one level tablespoon of salt added to his feed twice daily.
The amount of salt and/or commercial electrolytes preparation you need to add clearly depends upon what you are feeding and how much your horse sweats but remember that a horse cannot store electrolytes for when they are needed so added salt and commercial electrolyte preparations can only top-up deficient levels in the horse’s fluids.
This means that commercial electrolyte preparations, in particular, tend to be needed after sweating has taken place, not before.
Sweating is not always obvious and judicial use of electrolytes following travelling, when discreet or ‘silent’ sweating may have taken place, should be beneficial.
Care must be taken not to add to feed or syringe-in commercial electrolyte preparations in advance of sweating, this will cause horses that do not drink enough water to effectively become dehydrated, reducing performance and risking ‘tying-up’ and even more severe effects.
This is seen too often when horses are competing away from home.
When choosing a commercial electrolyte preparation make sure that either salt or chloride is the highest ingredient. Sugar (glucose/dextrose) should not be the first ingredient listed as it means that the product may not supply sufficient electrolytes to meet your horse’s needs.
Good products will contain high levels of sodium, chloride and potassium, with additional low levels of calcium and magnesium.
Feeding instructions on the commercial electrolyte preparation label should clearly indicate varying levels of preparation to be added according to the horse’s level of sweating.
If you are uncertain about whether your horse would benefit from the addition of salt or electrolytes it is recommended that you contact an experienced equine nutritionist.
Call the TopSpec helpline on 062 85401 or 00 44 1845 565030 (UK).
When feeding salt, it is useful to know that:
KEY MANAGEMENT POINTS