Equine electrolytes, exercise performance and recovery

Those who work outside during hot and humid weather are familiar with sweat-soaked shirts and sweat rolling from their foreheads. Horses and humans are two of the very few mammals that really rely on sweating to regulate body temperature. Horses have one of the highest sweat rates of all mammals and can lose 1–12 liters of sweat per hour, meaning they can lose about 70% of their metabolic heat from evaporative sweat. Several factors can affect the amount of sweat excreted, including work intensity, temperature, humidity and level of fitness.

The sweat of both humans and horses is composed of water, minerals (sodium, chloride, potassium, calcium and magnesium), and some proteins. The minerals, also called electrolytes, are influential in the maintenance of fluid balance, osmotic pressure, nerve response, muscle contraction and relaxation. However, although both humans and horses sweat liberally, their sweat glands are not the same, creating different concerns for dehydration and exercise recovery. Humans largely have eccrine sweat glands, while horses predominantly have apocrine sweat glands.

Human eccrine sweat glands retain large quantities of electrolytes, producing what’s called hypotonic sweat, which contains lower concentrations of electrolytes when compared to other bodily fluids. This increases plasma osmolarity, stimulating the thirst response. But equine apocrine sweat glands do not retain large quantities of electrolytes, so horses’ sweat tends to be isotonic or hypertonic, containing the same to higher concentrations of electrolytes compared to other bodily fluids. This isotonic or hypertonic sweat doesn’t increase plasma osmolarity, which in turn doesn’t stimulate the horse’s thirst response. Consequently, equine athletes lose more electrolytes and are at an increased risk for dehydration, heatstroke, muscle fatigue/cramping, and potential cardiac arrhythmia in extreme cases.

Electrolyte supplementation and its role in exercise and recovery

Optimal hydration and electrolyte status sets equine athletes up for improved exercise performance. Research from the University of Veterinary Medicine Hannover reported improved water and electrolyte metabolism when horses were supplemented one to four hours pre-exercise. This can lead to improved exercise performance in hot weather. 2021 research led by Canadian researchers at the Nutraceutical Alliance reported increased exercise duration and sweat volume, as well as delayed onset of fatigue when three to eight liters of electrolyte water was consumed before the onset of moderate exercise.

Electrolyte supplementation is also beneficial in optimal exercise recovery, helping prepare horses for returned performance — and adequate post-exercise hydration can do more than prevent risk factors from dehydration. Research by the University of Guelph reported that oral administration of electrolyte water after prolonged, moderate-intensity exercise improved the rate of muscle glycogen repletion. These results indicate that post-exercise dehydration may be a contributing factor to slow muscle recovery and slow glycogen repletion.

Providing electrolytes in water during and after exercise will further induce drinking during exercise recovery. The electrolyte solution increases plasma osmolarity and leads horses to consume more water within 60 minutes post-exercise than they do when given regular water. However, nonelectrolyte water should be provided as well, in case a horse doesn’t favor the taste of water with dissolved electrolytes.

Checking for dehydration

Horse owners can check for signs of dehydration in the field. Two common tests include checking skin elasticity and gum coloration.

When evaluating skin elasticity, pinch and pull a small section of skin on the neck above the shoulder. Well-hydrated skin will snap back quickly. Dehydration will show the skin remaining as a ridge or taking longer than two seconds to return.

Long capillary refill time is another sign of dehydration. Hydrated horses should have moist, pink gums. When testing for dehydration, lift the horse’s lip and press the gums, above the teeth, for a couple of seconds. After pressure is released, the pink color should refill the white spot created by your finger. If gums are white in color, or if the spot takes more than two seconds to return to the original pink color, these are signs of dehydration.

Electrolyte supplementation

When to provide electrolyte supplementation is a common question asked by horse owners. Under average conditions, forage, commercial feed, and free-choice salt will cover electrolytes excreted from sweat. Although free-choice salt is recommended and can be beneficial, excessive salt supplementation in feed isn’t a recommended practice. It can cause horses to refuse feed, can lead to gum ulceration, and can increase dehydration post-exercise when horses don’t consume adequate water. Due to these risks, most provide free-choice salt separately from the feed.

As mentioned before, several factors affect the amount of sweat that horses excrete including work intensity, temperature, humidity, and level of fitness. In many commercialized diets, sodium and chloride are not provided at high enough levels to replenish electrolytes lost from excessive sweating. When these factors coincide and excessive sweating occurs, additional electrolyte supplementation is crucial to recovery!

Why McCauley’s® Hydrolyte®?

McCauley’s Hydrolyte encourages water consumption, improving hydration status and maximizing exercise recovery. It doesn’t contain added sugar, which makes it safe for horses with metabolic diseases like Cushing’s disease, equine metabolic syndrome, and chronic laminitis. It has long been said that added sugar improves electrolyte absorption and retention, but this myth has long been debunked in horses. No added sugar in Hydrolyte further ensures a focus on providing quality electrolyte ingredients rather than containing a large fraction of sugar.

Hydrolyte also provides optimal electrolyte supplementation by mimicking the ratio of electrolytes lost in equine sweat. It is balanced with sodium, chloride, calcium and magnesium to replenish minerals lost from excessive sweating due to exercise, stress and environmental conditions. Hydrolyte can also easily be top-dressed on feed and/or dissolved in water for flexible electrolyte supplementation.

Summary

• Horses have one of the highest sweat rates of all mammals and can lose 1–12 liters of sweat per hour.
• Equine sweat glands lose more electrolytes than human sweat glands do, increasing the risk of dehydration.
• Providing electrolyte water can improve equine exercise performance and recovery.
• Ways to check for dehydration include evaluating skin elasticity and gum capillary refill time.
• Providing free-choice salt is industry standard and recommended, but it may not ensure full electrolyte replenishment from excessive sweating.
• McCauley’s Hydrolyte is a great addition to your horse’s exercise program to aid in exercise performance and recovery during hot and humid conditions!

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