Heat and Horses
A healthy horse can dissipate an astonishing amount of body heat, sweating as much as 10 – 15 liters in a single, intense workout and moving warm blood to the skin for evaporative cooling. Yet once ambient temperature, humidity, solar load or exercise intensity outrun those cooling mechanisms, the result can be exertional heat illness (EHI), a potentially life‑threatening veterinary emergency. Recent work in Thoroughbred racehorses shows that the key to survival is early recognition and rapid, aggressive cooling.PMC
Understanding the “Heat Equation”
Horses rely on sweat evaporation, respiratory heat loss and convective transfer from the skin. High humidity or restricted airflow blocks those avenues. Governing bodies now quantify risk with simple indices:
Heat Index (°F + %RH)—When the sum tops 150, riders should shorten or reschedule work; above 180, competition or shipping demands veterinary supervision.US Equestrian
Wet Bulb Globe Temperature (WBGT)—Used by the FEI at international events; a WBGT ≥ 28 °C (82 °F) triggers mandatory cooling stations and shortened courses.Inside FEI
Because each horse is an individual, start checking rectal temperature during training now; most horses finish work at 101–103 °F, but a reading > 104 °F that fails to drop within 10 minutes warrants intervention.
Spotting Trouble Before It Escalates
Look for:
Excessive or absent sweating (anhidrosis)
Dark, “brick‑red” mucous membranes or prolonged capillary refill
Rapid breathing (> 60 bpm) that doesn’t slow in five minutes
Stumbling, muscle tremors or mental dullness
A rectal temperature > 105 °F predicts central‑nervous‑system dysfunction and possible organ damage.United States Polo Association®
Who’s at Highest Risk?
Unfit or overweight horses, dark‑coated breeds, older or very young animals, and any horse shipping long distances in a closed trailer accumulate heat faster. Add tack or protective boots, and the thermal load climbs further. Even well‑conditioned equine athletes struggle when intense exercise coincides with tropical humidity or still air.Nature
Prevention Is Better Than Treatment
Plan the clock and the calendar. Ride at dawn or after sunset and schedule lessons, farrier work or transport around cooler windows.
Provide unlimited cool water. Horses will drink 50 – 70 liters per day in extreme heat; add plain salt (30 – 60 g) or commercial electrolyte blends to replace sodium and chloride lost in sweat.
Maximize airflow. Shade, fans and open barn doors cut ambient temperature by several degrees.
Clip heavy coats and remove non‑breathable turnout sheets. Slick summer coats dry faster and radiate heat better.
Condition gradually. Heat acclimation over 10–14 days improves sweat rate and plasma volume, giving your horse physiological “air‑conditioning.”
Cooling That Works
Research is unequivocal: continuous application of cold or ice water, immediately scraped off to prevent insulation, then reapplied is the gold standard. Combine it with shade, fans and cool mist. If the horse’s temperature isn’t < 102 °F within 20 minutes, call your veterinarian, intravenous fluids, anti‑inflammatories and monitoring for secondary complications (laminitis, rhabdomyolysis) may be necessary. (PMC)
Debunking Common Myths
“Cold water causes muscle cramping.” False, rapid cooling saves lives; no evidence shows any downside to cold hosing hot horses.
“Let him drink only a few sips.” Horses can safely gulp cool water as soon as they ask for it; restricting fluids delays recovery.
“Sweating always means heat stress.” Actually, anhidrosis, no sweat, poses equal danger. Know your horse’s normal sweat pattern and watch for changes.
Take‑Home Message
Summer rides and competitions aren’t off‑limits, but they do demand vigilance. Monitor the heat index, adapt your training, and practice proactive cooling. At the first hint of heat stress, temperature that won’t come down, neurological changes, or stubborn tachycardia: stop, cool and call your veterinarian. By partnering with your vet team and respecting the weather, you’ll keep those hooves pounding happily through the hottest months of the year. Stay cool, and ride on!