Electrolyte Supplementation in the Horse

Sweating the Small Stuff -- Electrolyte Supplementation in Horses

Heather Beach, DVM

Now that we are getting into the hot summer months, many horse owners will instinctively reach for their tubs of electrolytes and start adding them scoop by scoop to their horse’s grain.  If you have fed electrolytes in summer before but are sitting there secretly wondering inside your head, “what are electrolytes anyway? Why exactly do I give them to my horse? When am I even supposed to give them?” you are definitely not alone.  Electrolytes are probably the most frequently administered feed additive that barely anyone in the horse world knows anything about.  

So what are electrolytes anyway?  

Essentially, electrolytes are the minerals and salts that circulate within the bloodstream and tissues of the body.  Sodium, potassium, calcium, magnesium, and bicarbonate are some of the most important ones found in the body.  These substances are abbreviated by their chemical name and also the “electric charge” they carry relative to one another.  So Sodium = Na2+, Potassium = K+, Chloride = Cl-,Calcium = Ca2+, Magnesium = Mg2+, and Bicarbonate = HC03-.  Proper concentrations of these electrolytes in the bloodstream and muscle tissues are essential for life and basic body functions.  

So, if I don’t feed electrolytes, my horse will die?  

Not exactly, but maybe.  The body is extremely good at maintaining normal levels of electrolytes in the blood stream.  It takes major disease processes or major electrolyte losses for the body to lose its ability to keep the levels in a normal range.  Under most normal circumstances, electrolyte supplementation is not necessary as a daily additive. 

So I can throw away my tub of electrolytes?  

Definitely no.  Both horses and humans lose a great deal of water through the action of sweating.  This is the purpose of sweating -- the water wets the skin and then evaporates as the air touches it, creating a cooling effect for the body.  This is why cooling is more difficult in humid weather, as sweat evaporates less efficiently.  What is unique about horses is the fact that they lose a tremendous amount of Sodium (Na2+) and Chloride (Cl-) in their sweat as well as smaller amounts of Calcium (Ca2+) and Potassium (K+).  This is why horse sweat gets so frothy sometimes -- the lather is caused by all the salts present in equine sweat. That's where your electrolytes are going!  So if your horse engages in strenuous activity especially in hot humid weather, and especially if he is going to be asked to repeat that activity in a short amount of time, you should be giving supplemental electrolytes.  For extremely demanding activities such as endurance racing or cross country, electrolytes should be administered before, during and after the stressful event.

What else should I know about electrolytes?

Electrolyte supplementation can help prevent dehydration during times of high sweating. Thirst is stimulated by increasing sodium (Na2+) concentration in the blood stream. Human sweat is much closer to plain water, so as water leaves our blood stream in the form of sweat, sodium stays behind, blood becomes saltier, brains says "Ah!! Thirsty! Drink more water!"

The horse on the other hand pulls yet another move from the "designed to die" playbook. The horse sweats water AND high concentrations of electrolytes, so as the horse loses more and more sodium and other electrolytes through sweat, it actually becomes LESS AND LESS THIRSTY which leads to dehydration then impaction colic if you're lucky; tying up, renal failure and death if you're really unlucky, or if you just keep giving it banamine relentlessly instead of calling a veterinarian for help. Horses who have become electrolyte depleted may have an elevated body temperature and heart rate, show signs of muscle cramping or tying up, exhaustion, lethargy and/or depression. An exhausted horse who is electrolyte depleted is a medical emergency and will require intravenous fluid replacement therapy as soon as possible. 

Horses can also lose so much calcium through their sweat that they develop a condition known as "Synchronous Diaphragmatic Flutter" aka "thumps." The horse will appear to have the hiccups with this condition and it is a sign of extreme electrolyte derangement and requires immediate treatment. You would think that lots of oral calcium supplementation would help prevent this, but sadly ... this is not true. Too much oral calcium for too long leading up to a stressful event (endurance race, cross country) can actually predispose a horse to getting the thumps by activating a hormone in the gut and kidneys that signals the body to excrete excess calcium instead of storing it in the bones. So it is best to keep calcium supplementation to just before an anticipated time of loss. 

What do I look for when buying electrolyes?

Dr. Jeannie Waldron, an equine veterinarian and endurance race rider, wrote a great article on this topic in Practical Horseman Magazine. She recommends the following:

  • Check the label carefully. Look for chloride and/or acetate combinations such as sodium chloride, calcium chloride or calcium acetate, potassium chloride; these are quickly and easily absorbed. Avoid products that use di-calcium phosphate (which horses don't absorb very well) and those that list sugar, dextrose or corn syrup as the first ingredient.

  • Important: Electrolytes containing bicarbonate are formulated for horses with diarrhea. These can be harmful when used as an electrolyte supplement for stress and exercise.

  • If you need to supplement your horse's electrolytes and commercial products are unavailable, it's possible to make homemade electrolytes by combining "lite" salt (an excellent source of potassium and chloride) with sources of calcium and magnesium such as Tums. However, these formulas aren't absorbed as well as the commercial ones.

Dr. Jeannie Waldron recommends the product Endura Max electrolytes for her horses when out on the trail or endurance racing. I personally use KER's Summer Games Electrolytes which does contain di-calcium phosphate, but I am not concerned about extreme calcium depletion as my horse is not eventing or doing endurance racing. Electrolyte supplementation for horses in those disciplines should be carefully fine tuned and is beyond the scope of this article!

Stay cool and hydrated everyone!