SWEATING IT OUT: THE ELECTROLYTES STORY
The depletion of electrolytes in the cells of a horse, through excessive sweating, can be serious, the worst case scenario being the development of potentially fatal heat stress. Usually it is only high performance horses such as equine endurance athletes that are at risk and require electrolyte supplements, but in the heatwave we are currently experiencing here in the UK it’s useful to know when extra electrolytes may be necessary.
What are Electrolytes?
Electrolytes are common minerals – salts like ordinary table salt – which break down into elements called ions. Ions carry a positive or negative charge. Ions with positive charges are formed from minerals like calcium, magnesium, sodium and potassium, and negative ions from chloride, phosphate and bicarbonate.
The charged ions or electrolytes conduct electricity in an electrochemical process which carry neurological messages across the cells of the horse’s body, making muscles contract and systems work, from digestion and heart function to the regulation of the body’s fluid balance.
Excessive sweating causes an imbalance of positive and negative ions and a drop in blood volume and pressure, throwing systems out of whack, and they can begin to shut down, inducing a metabolic crisis.
Just drinking water is not enough to rectify the situation because with the electrolytes out of balance the fluid will not be delivered to the cells that need it.
In normal circumstances nature ensures that a well-fed horse receives the minerals he or she needs in the right proportions from a diet of hay and grass with the availability of a salt block. The kidneys play a big part in shedding excess electrolytes which are excreted in urine – and faeces.
It’s only when a horse sweats a great deal for a prolonged period, during work or on a very hot humid day that electrolytes become depleted and could cause problems.
Why does a horse sweat?
Sweating is nature’s way of cooling a hot horse. When the temperature of his blood and internal organs increases during exercise electrolytes signal the sweat glands into action, and usually the sweat on his skin evaporates, cooling him down. In humid weather this doesn’t happen fast enough and he’ll just keep sweating … sweat contains electrolytes which are then lost (about 9g per litre of sweat of vital minerals). The longer and more a horse sweats, the more electrolytes are lost, causing an imbalance which may cause problems before he has a chance to replace them.
In hot, humid conditions like a British heatwave even mild exercise or being transported in a van or trailer might result in profuse, prolonged (of around three hours) sweating – a potentially dangerous situation. Busy show and event horses, race horses, and endurance horses are most likely to become dehydrated and heat stressed in hot summer weather.
Also at risk are older horses with Cushings disease put out to pasture in hot weather, because they may still have a heavy coat even in summer.
It could take days to replenish vital electrolytes, and your horse will need your help in the form of electrolyte supplementation.
The Symptoms of Electrolyte Deficiency
Unfortunately there is no precise scientific formula for knowing when, or how much, electrolyte supplementation a horse needs. It depends largely on his work schedule. There is little danger in feeding too much electrolytes; the horse will simply drink more to dilute and excrete any excess. There are, however, signs to look out for if a horse is consistently lacking in electrolytes. These include:
A horse suffering from immediate heat stress during and after exercise in humid conditions will breath heavily, have an irregular heart rate, and exhibit signs of “thumps” (an irregular spasming of the diaphragm similar to hiccups).
What can you do to cure or prevent electrolyte deficiency?