Heat Stress in Horses
Heat stress and heat stroke are equine emergencies that are most commonly observed in the summer months when the temperature and humidity outside are at their highest.
Horses naturally produce heat in two normal metabolic functions: digestion and exercise. Heat stress occurs when there is a breakdown in the way a horse normally cools down and sweat is not able to evaporate and allow for proper cooling. If left untreated, the process of heat stress can lead to heat stroke, which can be life-threatening.
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| How to tackle Heat Stress in Horses |
Symptoms of Heat Stress
A horse who is experiencing heat stress may exhibit one or more of the following signs:
Profuse sweating or less sweating than expected
Hot skin to the touch
Rapid breathing
Rapid Heart rate or pulse that does not improve with rest from exercise
Increased body temperature of above 102 degrees Fahrenheit
Muscle weakness
Stumbling
Dehydration (signs may include tacky mucous membranes, sunken eyes, lack of skin elasticity or tent when you pull up from body, lack of urination)
Symptoms of Heat Stroke
Heat stress can quickly turn into heat stroke. Symptoms of heat stroke include:
Rapid respiratory rate continues
Increased body temperature of over 106 degrees Fahrenheit
Collapse
Convulsion
Causes of Heat Stress and Heat Stroke in Horses
There are several factors and conditions that can lead to heat stress in horses.
These conditions include:
High outside temperature
High environmental humidity
Poor barn ventilation
Prolonged exposure to sunlight
Excessive work
Transportation
Obesity
The most common scenario for a horse to become heat stressed is if they are exercised when the conditions outside are hot and humid. Under these conditions, evaporation from sweat is greatly reduced and heat stress leading to heat stroke are much more likely to occur.
What Temperature Is Too Hot to Ride a Horse?
Every horse tolerates heat differently, but there are some general guidelines. In the heat of summer, it is best to ride in the mornings and evenings instead of the heat of the day. It is also important to allow adequate time for a horse to acclimate to hotter weather if they are new to the environment. Below is a chart with guidelines on when it is too hot to ride based on the outside temperature and humidity.
Outside temperature (F) + Humidity (%) | Heat risk with exercise |
Less than a 130 | Minimal risk |
130-150 | Low risk, as long as horse replenishes fluid loss from sweating |
Greater than 150 | Moderate risk of heat stress |
Greater than 180 | Severe risk, DO NOT EXERCISE |
Additional factors that can make a horse more prone to heat stress include:
Dehydration
Loss of electrolytes from sweat
Geriatric horses
Horses with anhidrosis (unable to sweat normally)
How Veterinarians Diagnose Heat Stroke in Horses
Your veterinarian will start with a history and physical exam in order to diagnose heat stress and heat stroke in your horse. During the exam, it will be important for the veterinarian to look at the horse's mucus membranes for color and moisture, check heart and respiratory rate, and check body temperature.
Treatment of Heat Stroke in Horses
Treatment of heat stress and stroke in horses will depend on the severity of your horse’s symptoms. If you suspect your horse is experiencing heat stress, it is critical to stop all exercise immediately and move your horse to a cooler setting, such as in the shade. Be sure to contact your veterinarian immediately.
While waiting for veterinary assistance, place a fan next to your horse and spray them with cool water. Allow your horse access to fresh water in small intervals until the veterinarian arrives. Your veterinarian will likely want to give your horse some intravenous fluids and electrolytes to help cool them off as well as replenish fluid and electrolyte losses.
Recovery and Management of Heat Stroke in Horses
Horses generally recover from heat stress with no lasting effects. Depending on the severity of the heat stress, your veterinarian will be able to advise you on how to safely return to your horse's normal lifestyle. Typically, allowing rest for a day or two and slowly easing your horse back to exercise is advised.
Prevention of Heat Stress in Horses
You can help prevent heat stress in your horse in a variety of ways:
Provide access to fresh water
Provide access to shade
Reduce ride time and intensity when it is hot and humid
Ride in the morning or evening when it is the coolest
Ask your veterinarian about providing electrolytes in times of strenuous work and increased sweating
Provide access to a fan if there is low to no air flow in your horse’s stall
Consider clipping horses with long hair
Transport horses during the cooler parts of the day
Heat Stress in Horses FAQs
How does a horse normally cool off?
Heat stress occurs when the body's normal mechanisms to cool off are not able to function sufficiently to disperse heat. Normally, a horse can get rid of extra heat through sweating and exhaling of warm air. By sweating, the horse becomes wet and allows for evaporation to take place, which cools down the horse.
How do you cool down a horse after exercise?
It is always important to take the time to cool out your horse at the end of every ride. This is crucial not only for the horse to appropriately cool down but also for the well-being of your horse's heart, lungs, and muscular system. Ten to fifteen minutes of walking at the end of every ride allows a chance for your horse to cool down slowly. After you have finished walking out and have unsaddled, always offer fresh water. Hose off your horse with cool water when sweaty and provide access to a fan after exercise.