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If electrolyte losses during heavy sweating aren’ t replaced promptly, the consequences can go far beyond simple fatigue. Horses can develop conditions such as thumps, puffs, and even tying‐up, all of which can escalate quickly into medical emergencies. Thumps, properly known as Synchronous Diaphragmatic Flutter( SDF), occur when the diaphragm begins to contract in rhythm with the heartbeat. This creates a visible jerking of the flanks that almost resembles hiccups, and it is strongly associated with low blood calcium levels. Thumps often appear during rest breaks or recovery periods, especially if a horse has been allowed to drink large volumes of water without receiving appropriate electrolytes. This dilutes blood calcium and potassium even further, worsening the problem instead of relieving it.
EFFECTIVE COOLING: WHAT SCIENCE TELLS US WORKS BEST
Cooling a horse effectively and quickly can be lifesaving. The evidence is clear: continuous application of cold water is the most efficient method. Instead of applying water and scraping it off repeatedly, simply continue hosing or pouring cold water over the entire body, focusing on the large veins of the neck, inner thighs, and lower limbs. As fresh cold water replaces the water warming on the skin, heat is steadily drawn away.
Removing tack immediately, walking the horse slowly, and offering small drinks of cool water all help support recovery. Avoid towels, coolers, or any fabric that traps heat against the skin. Shade and airflow are also essential. Small details matter, such as planning rides during the cooler parts of the day, reducing unnecessary tack, clipping heavy coats, and using fly protection to minimise energy lost to stomping or pacing.
ACCLIMATION, CONDITIONING & PREVENTION
Horses cope best with heat when they are fit, well‐conditioned, and gradually exposed to warmer weather. A horse brought from a cool climate into a hot, humid environment requires time for its sweating mechanism and circulatory response to adjust. During this acclimation period, even mild exertion may stress the horse more than expected.
Conditioning should progress slowly, allowing the horse’ s cardiovascular and muscular systems to adapt. Careful attention during training, monitoring heart rate, breathing, and recovery times, can offer early clues about how well the horse is managing heat. Riders should also be aware that excessive warm‐ups can push a horse into heat load before the main work even begins, especially if the humidity is high.
WHEN HEAT BECOMES AN EMERGENCY
If a horse shows signs of severe heat stress, including confusion, weakness, staggering, extreme sweating or lack of sweating, or rapid breathing that worsens after exercise, the situation can deteriorate quickly. The priority is to cool the horse immediately while contacting a veterinarian. Rapid cooling, continuous cold water, slow walking, and attentive monitoring may be the difference between recovery and a medical emergency. If the horse’ s condition does not improve quickly, intravenous fluids and electrolyte therapy may be required.
CONCLUSION
Summer riding can be one of the great pleasures of horse ownership, but it requires a heightened awareness of how horses respond to heat and humidity. By understanding the physiology of heat load, recognising early signs of distress, implementing hydration and electrolyte strategies, and cooling horses using scientifically proven methods, riders can minimise risk and keep their horses healthy and comfortable even on the hottest days.
With thoughtful preparation and attentive care, you and your horse can enjoy the season safely and make the most of every summer ride.
Dr Jennifer Stewart BVSc BSc PhD Equine Veterinarian and Consultant Nutritionist
www. jenquine. com
2026 AQHA MARCH / APRIL ISSUE