South African Equine Veterinary Association Congress 2015 Protea Hotel Stellenbosch
approximate one dose of an oral slurry) or to provide the additional electrolytes in a mix of
concentrate feed at the checkpoints.
What remains unclear is whether or not horses can be administered “too much electrolytes” and
whether or not there truly can be adverse effects of electrolyte supplementation. In theory, excess
electrolyte administration should not be a problem as long as competing horses are provided
frequent access to water and continue to drink because excessive electrolytes should be excreted
in urine. However, when electrolytes were administered in a high dose to fully replace anticipated
sweat losses in an 80 km ride, mild hypernatremia and hyperchloremia developed in some horses.
Although no clinical problems were observed with these electrolyte changes, this finding provides
support to recommend limiting electrolyte replacement to 30-40% of the anticipated losses.
Again, another 20% of anticipated losses may be replaced by intestinal reserves resulting in an
overall deficit of 40-50%, approximating a 4-5% BW loss. Finally, whether or not
supplementation with hypertonic oral electrolyte slurries may exacerbate gastric ulcer disease is
another concern. A recent gastroscopic survey of high-level endurance horses found ulcers in 93%
of horses during the competitive season as compared to only 48% during the short rest period
between seasons. To assess whether or not electrolyte supplementation could possibly exacerbate
gastric ulcer disease, groups of non-exercised horses were administered either eight doses of
hypertonic oral salt slurries or a placebo (water) at hourly intervals. In comparison to gastroscopic
findings 24 h before treatments were started, blinded scores for both number and severity of
gastric ulcers were increased on gastroscopic examination 12 h after the last dose of electrolytes
or placebo in both groups. However, scores for the horses treated with oral electrolyte slurries
increased to a greater extent that for the horses administered the placebo. It would certainly be of
interest to repeat this type of study in a group of endurance horses completing a 160 km race.
Our discussion of electrolyte supplementation so far has been limited to additional NaCl during
training or a mix of NaCl and KCl during competition. The large amount of K+ lost in sweat
would support that supplementation with both NaCl and KCl is warranted during prolonged
endurance exercise. Many commercially available electrolyte supplements also contain calcium
and magnesium salts as well as varying amounts of carbohydrate (glucose and others). Although
8-10 g of calcium and 4-5 g of magnesium may be lost in 50 litres of sweat, no research to date
has specifically investigated whether supplementation with these minerals is of benefit. Of
interest, when a mixture of NaCl and KCl were administered to horses completing a 60 km
treadmill endurance exercise test, the mild decrease in ionized calcium concentration and mild
increase in venous blood pH observed during control (non-supplemented) runs were abolished
with NaCl and KCl supplementation alone.
So, what‟s the bottom line? The bottom line is that horses exercising for more than a couple of
hours in hot, humid climes (especially when combined with transport) will likely benefit (and
voluntarily drink more water) when they are supplemented with extra NaCl and KCl. An easy
recipe for hard working horses in the summer would be 1-2 oz of an equal mix of table salt and
lite salt added to the grain twice daily. Next, an initial drink of salt water during the first few
minutes after exercise (or at rest stops during H^\