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The electrolyte debate heats up
To supplement or not to supplement—and, if so, how much—is the question in these dog days of summer


Common ground: Adequate preparation before competition

Veterinarians and physiologists on both sides of the Atlantic agree that performance horses must start their competition with adequate stores of both water and electrolytes. Pagan advises that competition horses should be eating a diet high in forage (pasture or good-quality hay) before intense exercise. Researchers from the Institute for Animal Nutrition in Hannover, Germany, proved that horses fed adequate forage maintained water and potassium balance better during exercise than horses fed a high-concentrate diet.1 "When a horse is fed liberal quantities of forage, it can store extra water and electrolytes in its large intestine," Pagan says.

Forage is a major source of potassium, containing roughly 10 to 20 g of potassium per kilogram of hay. Grass and hay also hold a large amount of water in the horse's cecum and colon. "This 'hind-gut soup,'" Smith says, "is a huge electrolyte and water reserve for the horse to draw from during the early stages of long competitions." She also adds that there are more electrolytes in one day's worth of hay consumption than the estimated losses from a 100-mile ride.

Pagan cautions, though, that forage is very low in sodium and marginal in chloride, so "supplemental (sodium chloride) salt is still required by the performance horse." The best way to achieve this supplementation is through the use of extra electrolytes administered the night before and the morning of the event, while being careful not to oversupplement. Pagan and others recommend 60 g of a balanced electrolyte supplement at each of these times.

Following this electrolyte preloading program reduces the need for large volumes of electrolytes during the competition. Supplementation should concentrate on providing additional calcium and magnesium. Pagan says, "If calcium and magnesium are not replaced by either mobilization of skeletal stores (resulting in weakened horses and poor performance) or supplementation, metabolic disturbances, leading to such complications as synchronous diaphragmatic flutter (thumps), colic or exertional rhabdomyolysis (tying-up), may occur."

Additionally, researchers at the Animal Health Trust in Newmarket, England, evaluated the electrolyte status of 144 horses suffering repeated episodes of tying-up.2 One hundred of the 144 had electrolyte values that fell outside of the normal range, and of this 100, 72 horses suffered no further episodes after receiving proper and balanced electrolyte supplementation. The use of high forage levels in the horses' diet is thought to be a principal factor in decreasing the amount of tying-up seen in performance horses, and proper pre-competition water and electrolyte loading can also help ensure that equine athletes will not only perform at their best but will be less susceptible to performance-related metabolic problems as well.

Relation to travel and stress

The concept of having a properly fed horse with optimal water and electrolyte storage before competition seems to be slowly catching on for many disciplines. Horses prepared in this manner may need minimal electrolyte supplementation during an event. The need to have a properly fed and prepared horse before competition now puts some focus on all the factors that go into getting a horse from its home environment to a show, race or event in the best condition possible. Horses that must routinely trailer for long distances or are stabled in stressful conditions before showing will more quickly use up stored water and electrolytes, will be less likely to eat and drink normally to replenish those stores, and may show up for competition in already less-than-ideal condition.

Addressing all factors that may help competition horses travel better and adjust to show stress is important. Using antacid formulations, probiotics and other pharmacological agents that can keep a horse eating and digesting well is also beneficial. While some electrolyte supplementation is likely to always be a part of equine athletic activities, especially for less-than-fit horses doing moderate exercise in hot weather, recommendations and attitudes are beginning to shift to "less is more."

Dr. Marcella is an equine practitioner in Canton, Ga.


1. Meyer H, Perez H, Gomda Y, et al. Postprandial renal and faecal water and electrolyte excretion in horses in relation to kind of feedstuffs, amount of sodium ingested and exercise, in Proceedings. Equine Nutr Physiol Symp, 1987;67.

2. Harris PA, Snow DH. Role of electrolyte imbalances in the pathophysiology of the equine rhabdomyolysis syndrome. Equine Exercise Physiol 1991;3:435.


Source: DVM360 MAGAZINE,
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