View my basket/checkout
 

Case Studies

Electrolytes Explained

Hermione Perry MSc, Nutritionist, Brinicombe Equine

Water and electrolytes are probably the most important component of the body, giving soft tissues and cells their structure. Electrolytes are minerals in soluble form which have a particular role in the body. Because they are either positively or negatively charged, they create the tension between and within the cells. They also allow osmosis, so that nutrients can flow into the cells, in exchange for waste products diffusing out. In order for the body to function efficiently, water and electrolytes must be replaced every day.

While a horse is exercising hard, the muscles are producing heat. The heat produced is transported by the blood to the skin for evaporation in sweat. Sweating is responsible for about 60% of the body’s cooling mechanism, and the respiratory tract dissipates approximately 25% of the heat. The remainder of the heat loss is through convection, but only if the ambient temperature is less than body temperature.

As the blood is being transported to the skin, it is diverted away from the muscles. This restricts the oxygen supply to the muscles, increasing lactic acid production in the muscle cells and fatigue. However, the cooling mechanism is essential as without sweat, the body’s core temperature would increase by 0.33°C per minute, reaching a life threatening temperature within a 6 minute gallop!

Horses sweat contains more protein during the initial stages of sweating. This protein has detergent-like properties which disperse the sweat into fine droplets over the hair, thus enhancing the rate of evaporation. The protein content is also the reason why horse’s sweat lathers. As sweating continues the protein content drops and the sweat becomes more watery so that it can run off the horse, cooling it quickly. Wiping sweat off is counter-productive as it prevents its evaporation and cooling effect, where as putting water on the horse will increase evaporation and enhance cooling.

The horse’s maximum sweating rate is 10 - 15lt per hour and during an endurance ride it is likely to be 6 - 9 lt per hour, thus a horse can lose up to 50lt of sweat during performance, which is equivalent to its entire blood volume! If not replaced, this would result in 11% weight loss from dehydration, a 15% loss is fatal. Moderate dehydration would result in a decrease in blood flow to the muscles and skin, fatigue and exhaustion. Decreased blood flow to the skin would result in less heat dissipation and an increase in core temperature.

Sweating results in water loss as well as sodium, chloride, potassium, magnesium and calcium. Significant sweating results in a considerable loss of these important electrolytes. Providing only water to the horse will result in dilution of the remaining blood salts, making the need for electrolytes even greater. Hormones produced as a response to exercise help to maintain the fluid balance of the body, by controlling the sodium and chloride balance via the kidneys. However, if the plasma chloride level falls too low, as in aerobic endurance type exercise, it will result in alkalosis. Alkalosis inhibits respiration, therefore decreasing the oxygen availability for energy production, increasing lactic acid and exhaustion. It is also believed that large electrolyte losses will dehydrate red blood cells so that they become deformed. These deformed red blood cells slow the blood flow and therefore reduce oxygen delivery to the tissues.

Anaerobic exercise, such as during racing, results in acidosis from increased lactic acid and transport of potassium out of the cells. Important enzymes such as creatine kinase will be lost from the muscles as a result of damage caused by exertion.

Dehydration can be checked clinically by pinching the skin over the shoulders. The skin should return to its original position in less than one second, but will be slower if dehydrated. However, poor performance is usually the first obvious symptom.

Feeding Electrolytes

There are no body stores of water or electrolytes, other than those carried in the gut, as any excess is excreted in the urine. Therefore you cannot load the body with water and salts prior to exercise as it will just be excreted. Fluids must be replaced as they are losing them, which is particularly important during endurance rides. The major electrolytes, sodium and chloride are provided by common salt, which should be freely available for horses in hard work. Most feeds have little or no salt added as it tends to decrease its shelf life. Electrolytes must therefore be provided in the form of a supplement, which also allows the dose to be adjusted in accordance with the workload. It is important to provide a supplement designed to match the electrolytes lost by horses. It is estimated that a 500kg horse in light work, will require 20g sodium, 25g chloride, 30g potassium and 11g magnesium per day. Just providing salt to a dehydrated horse would result in further potassium and water losses. The type of feed also affects the water carrying capacity of the gut. For endurance horses, forages should be fed prior to the ride as they increase the amount of water and electrolytes in the gut.

Drinking an electrolyte and glucose drink is more beneficial than just drinking water during endurance type activity. Research has shown significant improvements in performance and recovery time when horses are fed electrolytes during competition. Providing salts will also increase their water consumption so it can be used for sweat and cooling the body.

Electrolyte supplements may be given in feed or in water, though feed is often preferable to ensure their consumption and not impair the horse’s water intake. No matter how the electrolytes are fed, fresh water should always be available. The provision of fresh water will greatly reduce the risk of feeding too many electrolytes. There will be no benefit of feeding electrolytes to a horse who does not need them, but the health of a horse who does need them will be significantly improved.

Recommended product: Think Drink Syrup

» Return to case studies list

Website design by www.get-oomph.com