Electrolyte Supplementation in Horses: No Benefit to Include SugarBy Kentucky Equine Research Staff · July 19, 2012
As horses exercise, they lose sodium, potassium, and other electrolytes through sweating. These critical substances are necessary to maintain osmotic pressure, fluid balance, and nerve and muscle function. Electrolyte replacement is called for if horses sweat heavily or for a sustained time. Electrolyte supplements are available in a number of forms including pastes and powders. Some can be administered orally while others are designed to be top-dressed on feed or dissolved in the horse’s drinking water.
Owners who taste a pinch of their horses’ equine electrolyte supplements may detect a variety of flavors. Some preparations have a distinctly sweet taste, while others are more salty. Sweet mixtures may seem more appealing to the horse owner, but is a sugary supplement what the heavily sweating horse needs to replace the salt and other electrolytes that have been depleted?
An explanation circulating around stables is that the dextrose or other sugars in electrolyte mixtures are included to increase absorption of the other substances contained in the supplement. In an effort to find out if this is true, two studies were conducted at Kentucky Equine Research to evaluate whether sugar inclusion affects electrolyte and water uptake and retention in idle horses.
In the first study, four mature Thoroughbred geldings were used. Three of the horses were dosed with either 92 g of electrolyte alone, or the electrolyte with either 10 g or 100 g of dextrose. For these treatments, the electrolyte was mixed with 1 liter of water and administered by nasogastric tube. The fourth horse was given 1 liter of water as a control. All horses rotated through the trial so that each horse received each treatment. Blood samples were taken before and four hours after treatment and sodium, potassium, chloride, and glucose were measured. Sodium was significantly elevated post-dosing in all three electrolyte treatments compared to the control, but dextrose did not affect the rate or duration of increase.
In the second study, each horse was given distilled water and a small amount of deuterium oxide (a marker of total body water content). Horses were also treated with additional sodium chloride and potassium chloride; with electrolyte and dextrose; or electrolyte and starch. The control horse received only water with deuterium oxide. Blood samples were taken before treatment and one-half, 1, 2, 3, and 4 hours post-dosing, and urine and fecal electrolyte excretion were measured before and for 72 hours after treatment. Blood levels of electrolytes were higher in all three treated horses, but neither dextrose nor starch affected the rate or duration of increase.
These results indicate that adding dextrose or starch to electrolyte mixes does not increase rate of absorption or retention of electrolytes. Dextrose may still have some value in improving palatability of electrolyte mixes, but the higher the dextrose content, the lower the electrolyte content of the product. This means high-dextrose products supply lower amounts of electrolytes per kilogram and may be less effective as a result.