Dehydration in Horses: What to look out for

Dehydration in Horses: What to look out for

Dehydration in Horses: What to look out for 

Dehydration in Horses is common during the hotter months, therefore, it remains vitally important to recognise warning signs, alongside understanding how to prevent and treat should the issue occur. Here, Dr Jessica May, UK lead vet at the video vet service FirstVet, is on hand to give the best advice on the matter.

Signs of Dehydration in Horses

In hot weather, horses rely heavily on sweating for temperature regulation, leaving them prone to dehydration caused by the loss of electrolytes. The heat and sweat loss caused during the long hot days means it is essential to look out for signs of dehydration.

Signs of dehydration to look out for

Lethargic: If the horse seems distracted and is not performing as well as usual, or if they generally seem lethargic, this may be due to dehydration.

Urine: Dark or frothy urine can also be a tell-tale sign that the horse hasn’t been drinking enough water.


Gums: Another way to check if the horse is dehydrated is to look at the gums, which should be pink and moist. If the gums are tacky or dry, this gives you an indication that a horse may be dehydrated.

Capillary refill time: You can also press gently on the gum and see how long it takes for colour to return (this is known as capillary refill time, or CRT). The rebound should take one or two seconds, but it may take longer in a horse suffering from dehydration. It is important to note that an abnormal CRT can also point to more significant problems, usually associated with other clinical signs.

Skin: Perhaps one of the oldest known techniques is the skin pinch/tent test. Lightly tent some skin on the horse’s neck using your thumb and index finger and release it. The skin should ping back flat immediately; however, if it remains tented or is slow to flatten after you let go, the horse may be dehydrated.

Other indicators: Dark or dry droppings, a high heart rate, dull or dry eyes, a depressed state, and a fever can all be signs of dehydration in a horse.

Dehydration in horses is very common, there are a number of pointers to help you recognise early signs here.
Dehydration in horses is very common, there are a number of pointers to help you recognise early signs here.

How to prevent dehydration in a horse

There are small and straightforward measures horse owners can take that will help prevent dehydration.

Fresh water: Perhaps the most obvious measure is to make sure all horses have constant and easy access to clean, fresh water, particularly after exercise or when out in the paddock. Horse owners should check the water supply and quality there-of throughout the day.

Stabling: While stabling can help prevent overheating and offer time away from the sun, owners should be aware they can often become too warm. If stables lack ventilation and generally hold heat well in the winter, this may not be the best option for the horse. A field lined with mature trees offers a haven away from the heat; however, be mindful of flies and other nuisances.

Feed: If you want to make sure the horse takes in extra water, you can try soaking their hay or adding excess water to their hard food. Make sure hay is soaked immediately before feeding to avoid excess time spent in water. Hay soaking for too long can cause a loss of nutrients. Soakable feeds can also offer assistance in hydrating a horse reluctant to take in water.

Riding: To help prevent excess sweating, ride either first thing in the morning or in the evening when the day’s heat is not as prominent. If a horse has been exercising in the sun, which is sometimes unavoidable, it will lose electrolytes that need to be replenished.


Electrolytes are common minerals needed for all bodily functions and are lost when the horse sweats. Sweating can vary depending on several factors, including fitness, age and activity. There are five main types of electrolytes; Calcium, Chloride, Magnesium, Potassium and Sodium. Alongside sweating, Electrolytes are lost in droppings and urine.

Typically Electrolytes are replaced by forage: well-maintained grass and good quality hay, for example. However, when a horse has sweated excessively or after a prolonged period without access to water, Electroylets will need to be replaced by other means.

Replacing Electrolytes

Electrolytes are essential to the proper functioning of the digestive system and muscles, especially on recovery from exercise.

Adding a spoonful of table salt to the horse’s water or mixed into feed can help replace Electrolytes for those horses in regular work, or for those who are excessively sweating. The best way to replace Electrolytes is to supplement the horse via feed, water or paste. If not all, many of the industry’s top supplement manufacturers offer products that will replace Electrolytes lost depending on requirements, however, you should pay careful attention to the feed manufacturer’s instructions prior to use. Salt licks can be helpful for field grazed and stabled horses in excessive heat, but will not provide adequate intake should the horse sweat excessively.

If concerns arise surrounding severe hydration, veterinary advice should be sought immediately.

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