Heat Domes and Horses

As average temperatures rise, projections for San Mateo County anticipate an increase in the frequency and duration of extreme heat events due to climate change. As a horse owner, it is essential to understand how heat can affect your horses.

Heat tolerance in horses varies based on factors such as breed, fitness level, acclimatization to heat, and individual physiology. Horses will generate a significant amount of heat during exercise, which they will need to dissipate to avoid overheating and heat stress. Lighter breeds like Arabians and Thoroughbreds are better adapted to hot climates than heavier breeds like warmbloods and draught horses.

Horses that are fitter have better cardiovascular efficiency, which helps in heat dissipation. Horses that are acclimated to hot environments can tolerate heat better. It takes about 10 to 14 days to acclimatize a horse to a hotter environment. Keep that in mind when you are traveling to ride and show in hotter zones that are even a few hours away. Proper hydration and balanced nutrition play crucial roles in maintaining heat tolerance.

Horses with underlying conditions such as Cushing's disease can be more susceptible to heat stress. Obese horses, juvenile horses and foals are also at increased risk

Overheating occurs when a horse’s body temperature rises above its ability to dissipate heat. Heat stress can lead to serious health issues if not treated promptly.

Signs of Heat Stress:

  • Increased respiratory rate
  • Elevated heart rate
  • Excessive sweating, or in severe cases, absence of sweating
  • Lethargy or weakness
  • Elevated body temperature (over 103 degrees F/39.4 degrees C)
  • Muscle tremors
  • Uncoordinated movements
  • Collapse

The causes of heat stress include high ambient temperatures and humidity, intense exercise without adequate rest, dehydration, and lack of shade or poor ventilation. Transporting horses in hot conditions can be problematic and takes extra preparation and planning. Plan on traveling in the early morning or at night when it is cooler. It may be helpful to bring a supply of water that your horse is used to drinking.

An overheated horse must be cooled immediately. Move the horse to a shaded, well-ventilated area. It may be cooler outside than inside a barn. Use cool water to saturate the horse’s entire body, neck, and legs. Application of ice boots can help, as well as applying ice to the neck. If your horse is bothered by flies and you use a fly sheet, you can soak this thoroughly as well.

A fan can help speed up cooling in addition to repeated applications of water. Cooling is more efficient if you do not scrape the water off between applications.

Offer cool water to drink. Water with electrolytes can be offered as a choice in a separate bucket.

Monitor the horse’s temperature every 10-15 minutes. Normal temperature is around 99-101 degrees F (37.2-38.3 degrees C). Also monitor heart rate and respiratory rate until they return to normal levels. Allow plenty of time to rest and recover in a cool, shaded environment. Avoid strenuous exercise until the horse has fully recovered and ambient temperatures are more suitable. Adjust your riding schedule to the cooler times of the day.

If the horse's condition does not improve or if severe symptoms like collapse or muscle tremors are present, contact a veterinarian immediately.

Some existing barns are not designed to remain cool in our increasingly warmer summer climate, and at times it may even be cooler outside of the barn. Adding insulation can help and it may be possible to make modifications to improve general air flow and cross-ventilation. Fans can be used to increase circulation, and even temporary misters on a timer can be applied to help keep a horse cool.

New barn design and construction should incorporate appropriate insulation, ventilation, and cooling strategies.