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Heat Stress

Horses sweat freely and are often over exposed to the environment for lengthy periods in a paddock. In addition to this many horses undertake regular and vigorous work like racing, endurance, and eventing and weekend trail riding. These horses have an increased risk of suffering from dehydration. Dehydration can be a life threatening condition and should not be dismissed lightly.

Dehydration is the result of fluid and electrolyte loss. The more a horse sweats the more electrolytes that they loose. It is important that your horse receives adequate electrolytes to prevent and minimize several serious conditions such as dehydration, anhydrosis and the thumps.

Electrolytes are minerals that are dissolved in the blood and within cell fluids as electrically charged salts or” ions”. These salts are either acid or alkaline and the horse’s body usually keeps a careful balance between the two. The function of electrolytes is to aid in nerve transmission, muscle contraction and metabolic process and the control of water excretion.

When this balance is disrupted muscle fatigue sets in and the muscles become incapable of further contraction. Cramping and tying up are often the result of excessive electrolytes loss in the sweat that is not replaced as there are insufficient electrolytes in the diet to restore the balance.

Daily feeding of electrolytes will ensure that they are replaced when used and thus preventing dehydration.

Signs of Dehydration

· Dry harsh coat

· Sunken eyes

· Lethargy

· Loss of appetite

· Fatigue

· Cramping

· Tying up

· Poor performance and slow recovery from work.

· Poor capillary refill and lack of elasticity in the skin following a pinch test.

Causes of Dehydration

· Continual electrolyte loss though sweat, faeces and urine

· Extreme hot weather

· Exercise

· Travel

· Diarrhoea

· Lack of water

· Lack of free sweating(anhydrosis)

· Loss of appetite


· Daily electrolyte supplementation

· Oral electrolyte preparations

Veterinary treatment may include intravenous rehydrating, blood tests to source the imbalance and special drugs depending on the severity of dehydration.

In closing in the warmer months try to exercise your horse in the cooler part of the day if possible. Ensure that you supplement your horses feed with electrolytes daily. Always be prepared when travelling and plan rest stops along the way if travelling long distance. On arrival give your horse an electrolyte paste or liquid to help encourage water consumption. Most importantly ensure that your horse has natural or man made protection available from the extreme heat and always allow you horse free access to clean, fresh water.

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