Horse Owners Beware - 3 Myths that Can Be Disastrous to Horse Health

Horse in stall on a warm summer day.
Horse in stall on a warm summer day.

Working or riding horses in summer heat creates some significant health issues that can have severe consequences. Research has provided some valuable information about caring for horses during hot weather, but despite this research, many myths and misconceptions are rampant in the horse community about how cold water, hot weather, and electrolytes affect horses.

Best practices for caring for horses during hot weather

Best practices for caring for horses during hot weather

Summer's heat and humidity can be much more than just uncomfortable for your horse; they can be deadly and can lead to disastrous consequences as a result of inadequate care or belief in common myths about heat, cold water, and their effect on horses.

It isn't only upper level performance/racing horses that are at risk on hot humid days; serious dehydration and overheating can happen to any horse especially when horse owners and handlers believe some of the common myths that many horse owners take to heart.

For example: It Is a hot humid day. One rider. One horse. Both are exercising at a moderate level. Who is more likely to overheat?

It might surprise you to know that your horse gets hotter much faster than you and is more susceptible to the negative effects of heat stress, according to Prof. Michael Lindinger, an animal and exercise physiologist at the University of Guelph.

Summer's heat and humidity can be much more than just uncomfortable. They can be deadly. Horses lose their lives every year to heat stroke. Countless others struggle through anything from weakness to colic as a result of inadequate care in hot weather. Don't let this happen to your horse!

Prof. Michael Lindinger, an animal and exercise physiologist at the University of Guelph, explains: "It takes only 17 minutes of moderate intensity exercise in hot, humid weather to raise a horse's temperature to dangerous levels. That's three to 10 times faster than in humans. Horses feel the heat much worse than we do."

It takes only 17 minutes of moderate intensity exercise in hot, humid weather to raise a horse's temperature to dangerous levels. That's three to 10 times faster than in humans.

And the effects can be serious. If a horse's body temperature shoots up from the normal 37 to 38 C to 41 C, temperatures within working muscles may be as high as 43 C, a temperature at which proteins in muscle begin to denature (cook). Horses suffering excessive heat stress may experience a drop in blood pressure leading to hypotension, plus colic and renal failure.

First, horses are larger and have a higher percentage of active muscle than people do during exercise. When muscles are being used, they produce a lot of heat.

Your horse has several ways to stay cool. Some of the heat is transferred to the air exiting his lungs. The remainder is carried to the skin surface by the bloodstream. Blood vessels very close to the surface of the skin dilate, and dissipate heat through conduction, convection, and evaporation.

Beating the heat involves water - both on the inside of your horse via drinking and on the outside of your horse via hosing down.

Myth alert #1 -  Don't let a hot horse drink cold water

The facts: There are no health risks associated with letting a hot horse drink cold water. And there's no such thing as giving your horse "too much" water. Some believe that horses should not be allowed to drink unrestricted amounts of water when hot due to hyper-distension of the stomach leading to colic, but the truth is that a horse's stomach can hold between 2 and 4 gallons of fluid without becoming excessively distended.

Allowing your hot horse to drink also has cooling effects, as the water temperature and your horse's interior temperature equalize. Of course, water also helps to keep him hydrated. Severe dehydration can lead to organ damage.

Myth alert #2 - Don't hose your horse down with cold water

The facts: Research shows that hosing your hot horse down with cold water doesn't cause any ill effects. The colder the water, the more conduction heat loss occurs.

The belief that cold water can harm a horse has been thoroughly debunked based on extensive research conducted during 1995 at the University of Illinois and University of Guelph and at the 1996 Olympic Summer Games in Atlanta. Researchers proved conclusively that horses working under hot and humid conditions were better able to maintain core body temperature within an acceptable range, or even reduce i,t and also reduce heart rate during rest periods after intense phases, when ice water baths were used.

Horses suffering from heat stress and heat stroke require immediate cooling. Heat stroke is an emergency that requires immediate veterinary attention. Treatment includes stopping all exercise, getting the horse out of the sun, using fans, spraying and scraping ice water to cool the horse, providing cool, clean water, and making electrolytes available. Horses with heat stroke often require treatment with intravenous fluids and electrolytes to restore hydration and normalize blood chemistry.

Quick cooling for overheated horse

Quick cooling for overheated horse

Hosing down your horse is an effective cooling method because heat is transferred from the horse's muscles and skin to the water, which is then removed to cool the horse.

To cool an overheated horse (rectal temperature exceeding 103°F), spray or sponge the horse's head, back, neck, rump, and legs with cool water and immediately scrape the water off, repeating continuously until the horse is cool). As you hose off your horse, heat is lost due to evaporative cooling. Heat is also lost by conduction, as long as the water temperature is cooler than his body surface.

Hosing down your horse is an effective cooling method because heat is transferred from the horse's muscles and skin to the water, which is then removed to cool the horse. It is critical to scrape the warmed water off immediately, or the water may serve as insulation and might actually increase the horse's body temperature.

Adding ice to the water will increase the speed of cooling for very hot horses with rectal temperature exceeding 105°F. Although some believe adding ice will "shock" a hot horse, research has shown that using ice to cool a horse is safe. Ice baths have been found to reduce core body temperature and lower heart rates after intense exercise, and horses were also observed trotting more freely after an ice bath.

Finally, do not place a sheet or blanket on the horse while trying to cool him. Blanketing will block the evaporation of water from the skin and is not recommended during hot and humid conditions.

Myth alert #3 - Switch from salt to an electrolyte supplement

The Facts: Making a change from salt to an electrolyte supplement is the wrong thing to do and is potentially dangerous. Sodium and chloride, which are the components of salt, are the major electrolytes lost in sweat, followed by potassium.

However, the horse has a baseline requirement for salt that is about 1 ounce (28.4 grams) per day even without sweating. This needs to be met first and a typical dose or serving of many electrolyte products does not supply near that much, let alone the baseline requirement plus enough for sweat losses.

According to Eleanor Kellon, VMD, unlimited water both inside and out, lots of salt and care not to work the horse beyond his level of fitness will help you successfully avoid the danger zone in hot weather.

A function of electrolytes, especially sodium, is to hold water in your horse's body. To maintain proper hydration levels, the horse's brain constantly monitors sodium concentration. Thirst is triggered if the concentration of sodium gets too high; salt hunger is triggered if sodium gets too low.

There's a place for electrolyte supplements, but they have to be used correctly.

Consider this:

The skin pinch test can be used to determine if a horse is properly hydrated. When a section of skin on the neck or shoulder is pinched, the skin should recoil in 1-2 seconds in a normally hydrated horse. A delay indicates some dehydration..

According to Dr. Juliet Getty, Horse Nutritionist, a balanced electrolyte supplement is designed to replace what is lost from perspiration, but electrolyte supplements should only be given to a horse that is already in good sodium balance.

There are several ways to accomplish this. The best ways include offering free-choice granulated salt, or adding salt to your horse's meal. A plain, white salt block helps, but many horses do not lick it adequately.

A full-sized horse requires at least one ounce (two level tablespoons) of salt each day for maintenance, providing 12 grams of sodium. This is true all year long, even during the coldest winter months. Heat, humidity, and exercise increase the horse's need.

Horses often will not eat extra salt, so consider syringing one ounce of salt mixed with some oil or flavored liquid after an hour of intense sweating, not to exceed 4 ounces per day. If your horse is working for several hours at a time, you can add an electrolyte supplement but it should be offered in addition to salt, to replace what is lost from perspiration.

To prevent ulcers, always allow your horse to eat something before giving him salt or an electrolyte supplement. And never add electrolytes to a horse's only water supply. This will interfere with water intake. Fresh, clean water should always be nearby.

Helping your horse meet the challenges of hot weather

Overweight horses will have a harder time dealing with the heat. The added body fat acts as insulation, trapping body heat and making it more difficult for the horse to cool off. Working an overweight horse in the heat is an excellent way to end up with a sick animal.

Feeding management is also affected by the temperature. Some horses will go off feed if they get too hot. This can be a problem if the horse is too thin or is losing weight due to the heat - they can't gain if they don't eat.

In addition, the digestion of feed results in the generation of body heat, and some feeds generate more heat than others. Adding fat to the diet will increase the calories in the feed without increasing the volume of feed and fat burns cooler in the body than protein or carbohydrates.

Did you know?

If the humidity is over 75%, sweating as a cooling mechanism becomes compromised. The sweat doesn't evaporate off the horse; it runs off them, which is much less efficient.

Feed only as much protein as the horse needs in order to reduce the heat load. Also, feeding grass forages will decrease the metabolic heat generated as compared to feeding legume forage.

Barns should be opened as much as possible to allow any breezes to keep the stable ventilated.

If necessary, add fans and misters at strategic locations to help cool the interior of the barn and provide ventilation.

Cooler weather will return, never fear!

In the meantime, keep plenty of water and salt in front of the horses. Don't exercise them during the heat of the day, and feed them appropriately for their needs.

Together with diligent horse care, you and your horse should be set to enjoy the endless fun of summer.

About the Author

EquiMed Staff

EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.