Understanding Dehydration

The more a horse sweats, the more body fluid will be lost and the more dehydrated it will become. Dehydration is the result of excessive loss of water from the body. As sweat evaporates, it cools the body down.

Dehydration is estimated as a percentage of body weight that is lost and is hard to detect when it constitutes less than 5% but in cases where weight loss is greater than 5%, the horse’s skin becomes less elastic and is referred commonly as skin tenting. Signs that a horse is approaching or has reached a state of severe dehydration include:

• Elevated heart rate and decrease in performance
• Urine output decreases (or ceases) causing kidney dysfunction
• Excessive sweating (and associated electrolyte and isotonic fluid loss)
• A lack of perspiration (when the horse has stopped sweating inspite of continued exercise and hot ambient conditions)
• Anxiety and muscle twitching or, in severe cases, a lack of responsiveness
• Synchronous diaphragmatic flutters (commonly called "thumps")
• Rhabdomyolysis (tying-up); and in severe cases
• Exhaustion sets in and the dehydrated horse will collapse

How do you know if your horse is maintaining suitable hydration this summer?

There are some simple tests you can perform at home to check the hydration status of your horse.

Capillary refill time

1. Using both hands, part the horses lips to expose the upper gum.
2. Press gently on the gum just above the front teeth (incisors) for 3 seconds using your thumb or index finger. This will cause the blood to rush away from this area, blanching the gum.
3. Remove your finger. Watch and count how long it takes for the gum to return to its natural pink colour. Colour should return to the blanched area within 2 seconds, if it takes longer your horse may be dehydrated or have a circulatory problem.

Skin turgor test

1. Gently pinch and elevate the skin on the horses neck, in front of the shoulders using your thumb and forefinger.
2. Release the skin and watch to see if the skin snaps quickly (1 – 2 seconds) back into place. If the skin is slow to return and stays sticking up your horse may be dehydrated.

Important note: It is important to take both capillary refill and skin turgor measurements regularly so you get to know what is normal for your horse. The easiest way to remember to perform these tests is to include them in your regular grooming routine.

If you are concerned about your horses’ hydration status, seek veterinary assistance.

Capillary refill and skin turgor tests

Below is a short video, demonstrating both the capillary refill and skin turgor measurements. This horse displays a normal result to both hydration tests.