Veterinarians at Rood and Riddle Equine Hospital answer your questions about sales and healthcare of Thoroughbred auction yearlings, weanlings, 2-year-olds and breeding stock. Email us at [email protected] if you have a question for a veterinarian.

Question: Oral electrolyte supplementation in horses: worth its salt?

Dr. Peter Morresey, Rood and Riddle Equine Hospital: There is great wisdom in the old saying, “You can lead a horse to water, you can’t make it drink.” While the horse is likely the best judge of its needs most of the time, domestication and use create situations where it is necessary to intervene.

Electrolyte supplementation of horses with oral products is widely practiced and considered good management where it is predicted a deficiency could arise. Stress, whether imposed by exercise, social changes, or transportation results in weight loss from loss of water and tissue mass. Some researchers suggest to supplementing with sodium chloride prior to and during exercise or stress, but the horse must be allowed adequate time to eat and drink afterward.

There is evidence that dehydrated horses will not eat, and water alone is not effective in restoring hydration to horses that have exercised and depleted their energy stores. Water and especially potassium are also needed after exercise to allow regeneration of energy stores and preservation of body tissue mass. Horses must maintain correct blood concentrations of electrolytes, which allow them to retain ingested water in the correct body compartments during rehydration.

During exercise, the administration of concentrated electrolyte pastes has been shown to increase water consumption and replace electrolyte losses. It is reasonable to conclude that during any stressful period, including transport or sales activity, similar water and electrolyte changes will occur, albeit of lesser magnitude but no less importance.

As with all things, moderation is prudent. In one study, the number and grade of gastric ulcers was increased in horses that received a concentrated electrolyte supplement in water by mouth compared to horses that received the same volume of water alone. That is not to say electrolyte supplementation is not beneficial, as the effects of large electrolyte losses in sweat in exercising horses can be profound, requiring aggressive treatment to correct.

Study results are not uniformly consistent in recommending an ideal electrolyte combination to administer under any particular condition. However, if a balanced electrolyte product is not administered to excess, harm to the horse is unlikely and benefits are reasonable to expect.

While the jury may still be out for some people on the practice of giving horses an electrolyte supplement prior to transport or sale, one thing is not in doubt: supplements of any kind, including electrolytes, are not a substitute for a balanced diet, close observation during exercise or stressful periods, and consideration of the horse a whole.

Dr. Peter Morresey

Dr. Peter Morresey began his career in New Zealand as a mixed animal practitioner following graduation from Massey University in 1988. He completed a theriogenology residence at the University of Florida and spent time as part of the clinical faculty at the University of Pennsylvania. Areas of interest include reproduction, internal medicine, neonatal medicine, veterinary business and Chinese medicine.

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