Heat, Hydration & Electrolytes

August 02, 2017
By Richard G. Godbee, Ph.D., PAS, Dipl. ACAS-Nutrition

It’s summertime, which is usually the time of year when most horse owners begin riding and working their horses more. However, this is also the hottest time of the year and riders need to be aware of the dangers that heat poses to their horses and the increased demands to keep them hydrated.

In addition to humans, horses are one of the few animal species who use sweating as the primary means to cool themselves. Sweating is an example of evaporative cooling and is more efficient in areas with low humidity. Sweat not only contains water, it contains electrolytes, certain minerals and a protein called latherin. It is this protein that imparts the “foam” in heavily sweating horses. Wiping sweat off the horse is counterproductive since it decreases the evaporative cooling effect.

In hot temperatures, horses may become dehydrated due to excessive sweat loss. Maximum sweating rates in horses may exceed 10 quarts per hour and averages about 8 quarts per hour at the trot and canter combined. Failure to replenish this in a timely fashion can have many health consequences.

In order to keep horses hydrated, an adequate amount of clean water must be provided. Although water is a large part of hydration, it’s not the only factor. Several minerals (commonly referred to as electrolytes) are lost in the sweat as well, and are comprised of sodium, chloride, potassium and small amounts of calcium and magnesium. Horses will lose 3 times the amount of sodium and chloride and up to 10 times the amount of potassium as compared to humans. Both sodium and chloride are required to help regulate all body fluids, maintaining acid-base balance and muscle function due to their involvement in nerve activity.

Unlike many other nutrients in the body, electrolytes are not readily stored and are excreted if not needed. While “stockpiling” electrolytes in advance of sweating may not be effective, it is recommended to give additional electrolytes shortly (8-12 hours) before exercise. While this practice may be helpful, it is paramount that electrolytes lost in sweat are replaced for a day or two after the activity, since it may take that amount of time to replace what has been lost.

Feeding Electrolytes

A horse can lose 8-12oz of salt per day with moderate to heavy sweating. Since heavy sweating does not usually occur on a daily basis, adding this amount of salt daily is not required nor recommended. A horse in moderate exercise will lose 6.8-9 quarts of sweat and may require about 2oz of electrolytes per hour. Feeding a good electrolyte, such as Horse Health™ Electro Dex® electrolytes, is imperative to replenishing a horse’s mineral levels. Electro Dex® electrolytes contain a proper ratio of potassium, sodium and chloride plus a small amount of glucose (sugar) to enhance the absorption of the electrolytes. Since electrolytes will stimulate drinking, it is imperative that water is readily available.

Electrolytes may be added to a grain mix to ensure consumption or given as a paste. When feeding prior to exercise, it may be easier to top dress the horse’s grain. If giving electrolytes during exercise, a paste electrolyte should be used. A paste or gel electrolyte is great to have on-hand when on the trail or at a horse show. The administration of electrolytes should be given in addition to supplying the horse with 2-3oz of salt on a daily basis to encourage adequate water consumption and help maintain electrolyte balance. Regardless of the form used, be sure water is available and follow the directions for use.

By understanding why horses need electrolytes and how they are utilized, horse owners can ensure that their horses stay hydrated through the summer heat. Happy Riding!

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