Signs of Dehydration in Horses

Here’s how to monitor your horse for dehydration and help prevent it.
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chesnut horse drinking water from tank
Preventing dehydration in horses is key. | iStock

Q. As the summer heat drags on, I’m worried about my horse being well-hydrated. What signs of dehydration I should look for? Should I provide my horse with salt or electrolytes?

A. When we’re talking about how to manage a horse nutritionally, water intake doesn’t typically top the list, but it is one of the most important nutrients. Supporting hydration is critical year-round, but when the summer months arrive, focusing on optimal hydration can make all the difference for your horse.

Preventing Dehydration in Horses

Prevention is key. Be sure your horse receives an adequate amount of salt (based on the NRC guidelines for his age and workload) and has free-choice access to fresh, clean water at all times. In the summer months it can be more challenging to keep water troughs clean, so scrub and rinse them regularly, changing out the water, to prevent algae buildup. Providing free-choice loose salt and adding salt directly to your horse’s feed are both good options.

Beyond baseline requirements, try to supplement your horse with an electrolyte if he sweats regularly. Gold-standard practice provides a well-balanced powdered electrolyte in solution for them to consume. However, you can also add powdered or pelleted electrolytes as a top dressing on your horse’s feed. How much to supplement and which product to use depend on the horse’s fluid losses. Be sure to provide ample water for your horse, especially when supplementing with electrolytes because electrolytes given without water can worsen dehydration. Electrolytes might also be contraindicated for horses with kidney problems, which might affect the horse’s ability to filter excess.

Monitoring Horses for Dehydration

Even with steps to prevent dehydration, horse owners should know how to recognize subtle signs of the condition before it becomes severe. Loss of skin elasticity (due to the loss of water) and dull mentation often appear first.

A slower capillary refill time, dark urine, and changes in vital signs, such as an elevated heart rate or respiratory rate, can also indicate dehydration. As dehydration progresses, more serious problems, such as tying-up, impaction colic, and weakness, can arise. Knowing your horse’s normal water intake and vitals can help you recognize changes early. You can use this free Horse Health Check Tool to help you evaluate your horse’s health status.

Two simple checks can also help you assess your horse for possible dehydration: the skin pinch test and capillary refill time.

Skin Pinch

To check skin elasticity, lightly pinch the skin on your horse’s neck, just above the shoulder, to create a tent. Release the skin and watch how quickly it returns to normal.

Check capillary refill time
VIDEO | Horse Vital Signs: How To Check Capillary Refill Time

In a well-hydrated horse, the skin should snap back quickly. If it remains tented for more than 2 seconds, the horse might be dehydrated. If it takes longer to return to normal, call your veterinarian.

Capillary Refill and Mucous Membranes

Lifting your horse’s upper lip and examine his gums, or mucous membranes. Healthy gums should appear pink and feel moist. Dry, pale, or tacky gums can indicate dehydration or other health problems.

Next, press your thumb against the gum until the tissue beneath it turns pale. Release the pressure and watch for the pink color to return. This should occur within 1-1.5 seconds. A longer capillary refill time can indicate dehydration and warrants concern.

Take-Home Message

Horses need consistent access to fresh water and adequate salt to maintain hydration. Know your horse’s normal water intake and vital signs and watch for changes that could indicate dehydration.

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Written by:

Madeline Boast, MSc completed her master’s in equine nutrition at the University of Guelph and started an independent nutrition company known as Balanced Bay. She has worked with a variety of equids—from Miniature Horses to competing Thoroughbreds. Boast designs customized balanced nutrition plans that prioritize equine well-being, both for optimal performance and solving complex nutritional issues and everything between. 

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