Dehydration is a serious problem in competing and working horses, especially during hot weather. Horses are very sweaty animals and can quickly become dehydrated.

Horses competing in endurance racing or engaging in sustained heavy exercise are at the highest risk of dehydration.

Dehydration occurs when your horse loses excessive fluids from sweat, urine, feces, and respiration. If your horse does not drink enough to offset the fluid loss, she can become dehydrated.

The most common signs of dehydration are poor performance, loss of skin elasticity, weakness and increased respiratory rate. Dehydration also increases the risk of heat stroke, tying-up and slow exercise recovery.

Knowing the signs of dehydration and how to help keep your horse hydrated is important for every horse owner.

Dehydration in Horses

Horses become dehydrated when fluid loss is not offset by adequate water consumption. Water is one of the most important nutrients for the horse and makes up 61 – 72% of a mature horse’s body weight.

To maintain appropriate hydration status, the average non-working horse must drink at least 6.6 gallons (25 litres) of water daily. [1]

If your horse is exercising or in a hot climate, the amount of water they need to drink increases. [1]

Exercising horses can lose +10 litres of moisture per hour through sweating. Even in moderate environmental conditions, dehydration can occur after 3 hours of exercise. [3]

Field studies of endurance horses show that fluid losses are greatest by mid-ride. Horses can lose 20-25 litres total after an 80-kilometre ride. [4]

During heavy, prolonged exercise on a hot day, a horse’s water needs can increase by 300%. [2] Offer your horse water multiple times during long, intense workouts or when a horse is being exercised during hot weather.

Illness

Illness or fever can also cause dehydration if a horse isn’t drinking sufficiently.

Additionally, horses with severe and acute gastrointestinal infection are at risk for dehydration. Severe diarrhea caused by colitis or copious gastric reflux caused by enteritis can result in life-threatening fluid losses.

A horse with chronic loose manure can have four times greater fecal output than a healthy horse. To compensate for increased fluid losses, they would need to double water intake. [1]

Electrolyte Imbalance

Sweating also causes the loss of electrolytes including sodium, potassium, and chloride. [14]

These electrolyte minerals are needed to maintain proper fluid balance, nerve and muscle function, as well as acid/base balance in the horse’s body.

Low electrolyte levels can actually suppress your horse’s thirst response and worsen dehydration, especially with continued exercise and sweat loss. [17]

Feed your horse 1 – 2 ounces of salt every day to promote water intake, and use an electrolyte supplement in hot weather or after heavy work.

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Top 10 Signs of Dehydration in Horses

Every person who cares for or owns a horse should be able to recognize the early warning signs of dehydration.

Early detection can help you ensure you can rehydrate your horse quickly and avoid heat stroke or other complications.

1) Loss of Skin Elasticity

The skin pinch test can show loss of skin elasticity. Though not completely foolproof, it is one of the most common ways to check for dehydration in horses.

To perform this test, use your thumb and forefinger to gently pinch the skin of your horse’s neck, just above the point of the shoulder.

In normal cir