Water: Why Hydration In Horses Is So Very Critical.


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Water: Why Hydration In Horses Is So Very Critical.

Morgan Murphy

Water: Why Hydration In Horses Is So Very Critical.

We hear so much about equine nutrition that sometimes it can be easy to overlook the importance of clean, temperate water! As with humans, water accounts for a large percentage of the equine body and regular intake is imperative for good health. It is a myth that dehydration can only occur in hot weather – in fact, when a horse has restricted access to water or is under the stress of exercise, dehydration can occur at any time of the year.

Why is water important?

The horse’s body is made up of around 80% water and it is essential for every body function from fluid inside the cells to fluids outside cells such as that surrounding joints and blood plasma. The horse will need to replace any fluid lost through sweat, urine and faeces and therefore must drink enough each day to replenish this reserve.

Electrolytes are dissolved in the water in the body of the horse, forming charged ions such as sodium cation (Na+) and chlorine anion (Cl-). These are essential salts which help maintain bodily functions, including nerve transmission, muscle use and digestive facility. Any imbalance in these electrolytes can cause physiological problems in the horse, from reduced respiration rate and muscle cramping through to affected heart function. When a horse becomes dehydrated, the body loses both the water and electrolytes, consequently risking the horse’s wellbeing and normal functions.

What are the signs of dehydration?

Dehydration is not usually apparent until the horse is approximately 5% dehydrated, after which time he may start to display symptoms. Often the first notable sign is “tenting” – this is where the elasticity of the horse’s skin decreases, owing to the decreased cellular water content. If you pinch a fold of skin and it remains arched for longer than normal, this is a classic sign of dehydration. Other signs include:

  • raised heart and respiratory rates

  • reduced frequency and volume of urination and when urine is passed it is dark and concentrated

  • slower capillary refill time – this is the length of time it takes for the color to return to the gums when pressed with a finger; in a horse of good health this should take no longer than two seconds

  • fatigue

  • in severe cases the horse may collapse.

Why might my horse become dehydrated?

Every horse is at risk from dehydration. Water loss through sweating and stress in performance horses is quite extreme and this should be addressed each time they are exercised. However, leisure horses are also at risk. A horse under stress may sweat more, for example if he is travelling or unwell. Hot weather is always a contributory factor for dehydration but even on cooler days a moderately fit horse competing at an all-day show, and sweating through excitement and exercise, can be at risk of becoming dehydrated.

What happens when my horse becomes dehydrated?

Dehydration can affect the entire body. Not only will the horse become tired, weak and prone to lapses in concentration, which can put him as risk from injury, but internal changes also take place which cause significant problems. For example, the internal surface of the lungs needs to be kept moist; decreased moisture content increases the amount of sticky mucous present in the lungs and can alter the horse’s respiratory rate and make him vulnerable to infection. Furthermore, insufficient water in the hindgut will slow the digestion of food, leaving the horse susceptible to impaction colic.

How do I prevent dehydration?

The simplest way to prevent dehydration is to provide a constant source of fresh water. Unlike cattle, horses are notoriously fussy when it comes to drinking, particularly from unknown containers, therefore to encourage the horse to drink you should ensure that buckets are clean and do not bear the scent of other horses. If a horse is reluctant to drink at an event, try adding apple juice (Assuming the horse likes apples) to the water to further encourage drinking.

You can add additional water to the horse’s diet by mixing it with his feed, moistening his grain mix or soaking his hay. Don’t forget you may also need to replace lost electrolytes – traditional salt licks are not recommended as they have been proven to be ineffective. However, some manufacturers offer electrolyte supplements. These are normally balanced for hard work and sweating and can be diluted in water, so if you regularly compete or have a horse in hard work it is highly recommended that you keep a tub in the trailer and at the barn.

Water is essential for all life forms. Dehydration can cause physical discomfort and be seriously harmful if left untreated. By recognizing and responding to symptoms of dehydration, as well as considering your water horse’s water supply, travel arrangements and exertion levels, you can help prevent any long-term issues from arising.


  • Thanks for including about the ions. I like learning about the underlying science.