Dehydration in Horses: Signs and Treatment

Dehydration in horses occurs when a horse loses more fluids than it takes in. It can affect horses of any age and may develop during hot weather, cold weather, intense exercise, travel, or illness.

Monitoring your horse’s water intake, activity level, and signs of discomfort can help you recognize possible dehydration and know when to contact your veterinarian.

What Is Dehydration in Horses?

Dehydration in horses occurs when a horse loses more fluids than it takes in. It can affect horses of any age, in any location.

Athletic horses, horses with conditions such as anhidrosis, and horses living through significant weather changes in the summer or winter may be more likely to experience dehydration.

It's important to monitor your horse's water intake, exercise level, and signs of dehydration or discomfort, as these may indicate an underlying issue.

What Are the Signs of Dehydration in Horses?

Signs of dehydration in horses may include low energy, changes in appetite, dry skin, and colic.

Common signs include:

• Fatigue or less energy than usual
• Decreased appetite
• Dry skin
• Colic

What Causes Dehydration in Horses?

Dehydration in horses can be caused by hot or humid weather, reduced water intake during cold weather, limited access to water, excessive sweating during exercise, stress, travel, or underlying medical conditions.

Horses may be less willing to drink water during very cold times of the year. Athletes, such as racehorses, can easily become dehydrated when they exercise hard and sweat excessively.

An overly stressed horse may pace constantly and sweat, and not have interest in drinking—becoming dehydrated. Extended periods of travel on the horse trailer may lead your horse to have a decreased appetite and thirst. 

Other causes include “tying up” or exertional rhabdomyolysis, diarrhea and colitis, and other underlying medical conditions.

How Veterinarians Diagnose Dehydration in Horses

Veterinarians assess dehydration in horses through a physical examination, including skin elasticity, gum color and moisture, capillary refill time, and heart rate. Blood testing may also be used to evaluate hydration and electrolyte imbalances.

Skin Tent Test

This test can also be performed at home. If you’re concerned your horse seems drier to the touch or is acting lethargic, you can grab a small piece of skin on the neck or shoulder and create a tent.

The skin should be fairly elastic and should return to its normal position in a second or two. A delayed reaction, or if the skin stays tented, is an indication of dehydration.

Gum Color, Consistency, and Capillary Refill Time

Checking the horse’s gum color, consistency, and capillary refill time (CRT) is another quick check or rough estimation that can give you important information at home. 

To check a CRT, you or your veterinarian will gently pull up the horse’s lip and check the gum color; normal should be a light pink. Gently push on the gum and then remove your finger. That spot will be white and should return to normal color in less than two seconds typically. 

This will also allow you to see your horse’s gum hydration. The gums should be moist, and not tacky, if your horse is adequately hydrated. 

You may get false estimates if your horse has just had a sip of water or if the gums have been pulled up repeatedly in a short period of time.

Heart Rate

Your horse’s heart rate may also be elevated (normal heart rate for a horse is 20–40 beats per minute), which you can note during a basic physical exam performed at home, especially if you keep a stethoscope in your first aid kit.

Blood Tests for Dehydration in Horses

To evaluate an exact measurement of your horse’s dehydration, your veterinarian will pull a blood sample and run a packed cell volume (PCV) test.

Your veterinarian may also run other bloodwork to check for electrolyte imbalances. Calcium, potassium, or other additives can be administered in IV fluids.

How Veterinarians Treat Dehydration in Horses

Treatment for dehydration in horses depends on its severity and may include electrolytes added to food or water, fluids administered through a nasogastric (NG) tube, or intravenous (IV) fluids and monitoring at a veterinary hospital.

Oral Electrolytes and Nasogastric Fluids

If your horse is mildly dehydrated at home, your veterinarian may administer water and electrolytes via nasogastric (NG) tube. They will pass a tube through your horse’s nose, down the esophagus, into the stomach. 

This is a typical part of a colic examination, so it will be performed if your horse is showing colicky signs (down/rolling, decreased appetite, pawing, lethargy, etc.) to check for reflux or excessive gas in the stomach.

IV Fluids and Additional Treatment

Your veterinarian may also recommend a few liters of IV fluids. They can run this on site or may recommend a trip to the local veterinary clinic so your horse can have further diagnostics performed and IV fluids administered over a longer period of time.

If your horse has an underlying disease or colic causing dehydration, they may require anti-inflammatories, antibiotics, muscle relaxers, or other medications.

Recovery and Management of Dehydration in Horses

Most horses recover uneventfully from dehydration when the underlying cause is appropriately managed. Your horse may need to be rested for several days to a week before resuming any sort of physical activity, depending on the severity.

Potential complications of dehydration in horses include:

• Colic: If your horse is systemically dehydrated, the intestines and food material in the gastrointestinal (GI) tract will also be dehydrated, and impactions are much more likely.
• Kidney damage
• Exercise intolerance
• Weakness

How To Prevent Dehydration in Horses

To help prevent dehydration in horses, monitor your horse's drinking habits, provide access to water during weather changes, and discuss electrolyte supplementation with your veterinarian.

The following practices can help you prepare for times of stress, exercise, or significant weather changes:

• Electrolytes are a huge help in promoting water intake in horses. Administering paste electrolytes before travel or a stressful event can encourage your horse to stay hydrated. Daily powder electrolytes is a great supplement worth discussing with your veterinarian, particularly in the warmer months.
  
  This can also be implemented in the late fall/early winter as it starts to get colder, as horses often drink less during this transition. They don’t believe they’re thirsty, and often start to feel frisky in the cold, so can get dehydrated much faster.

• In the cold, ensuring water is easily accessible is a crucial part of winter horse care. Water tank heaters/deicers will keep the water from freezing. Bucket warmers or adding warm water a few times a day in a warm and cozy location will also help your horse drink an adequate amount of water.
• If your horse is a chronic non-sweater and has anhidrosis, a daily dark beer may be recommended during the warmer months to promote appropriate sweating.