November 6, 2017 
You do it at the end of every ride—take ten minutes to walk your horse out, then maybe rinse them with cool water in the summer, or throw on a wool cooler in winter. You feel the temperature between their front legs and pronounce them “cooled out” when it feels normal to the touch. Most horse owners are pretty comfortable with the basics of cooling off their horses. But what does it really mean, physiologically speaking, to say that your horse is “cooled out”? And are you taking the best steps to help them get there?
Joan Hiltz, VMD, serves frequently as a control/safety veterinarian for competitive trail and endurance competitions and is frequently called on to check the well-being of equine competitors.
“The best way to know if a horse is cooled out or recovered from their work is when the horse returns to a resting heart rate within twenty to thirty minutes of stopping,” says Hiltz.
How hot a horse gets during work depends on a variety of factors, including fitness level, breed, and climate. During exercise, a horse’s temperature can go up to 103 degrees or even a little higher, so efficiently cooling out your horse is critical.
Physiologically speaking, the horse uses several different mechanisms to cool down, most of which function by bringing the heat towards the skin’s surface so it can be released from the body. Understanding how these mechanisms work, and how we can support them, can allow riders to better care for their animals post-workout.
Evaporation is one of the horse’s best mechanisms for cooling down their body. This is achieved through sweating; the sweat initially helps to cool the skin’s surface, but its evaporation draws small amounts of heat away. Removing tack is one simple step that riders can take to increase the evaporative surface area. Horses being kept in moderate to heavy work in colder climates often benefit from at least a partial clip to enhance the effects of evaporation through sweat. The hair itself holds the heat generated by exercise, but so does the sweat, which cannot evaporate as effectively in colder temperatures. Even just removing hair from the under neck and belly can help in these circumstances.
Radiation occurs when the heat from inside moves outside of the body. Anyone who has stood next to a hot horse has likely felt the heat coming off of them. Remember that heat is drawn to cold. By moving a horse to the shade and removing their tack, a handler can help the heat generated from exercise transfer from a warm body to the cooler air around it.
Convection occurs when air blowing on a hot horse moves the heat away. As warmed blood circulates through the body, ultimately ending up in the superficial veins, air blowing on the horse will help to cool this blood, which then is circulated back into the core of the horse’s body, thereby bringing the overall internal temperature of the horse down. Anyone who has stood in front of a fan on a hot day will understand this effect.
Conduction is what happens when the cool water you have sprayed onto your horse absorbs the heat from their body. It is only when the handler then scrapes off this water that the heat is fully removed. So if the water which is coming off of your horse is still warm, so is the horse. Scraping off the water has the added benefit of removing any dirt trapped on the skin, which can clog the sweat glands.
If the weather is hot then the water used to cool the horse must be colder than the ambient air temperature. “You can even put ice in the water,” says Hiltz. “If the water is warm it will not do the job. The whole point is to suck up the heat, and warm water won’t do it.”
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Concentrate on the areas of the body with large blood vessels, including the under neck and between the hind legs. “If it is rainy or the weather is a little chilly, you can cover the hindquarters while still applying water to those big vessels,” adds Hiltz. Improving conduction is one of the most effective mechanisms a handler can use to rapidly cool out a horse.
When conditions are ideal, a fit horse should be able to recover to resting temperature, pulse and respiratory rates within 20-30 minutes. If this does not occur it is cause for concern and further support. In particular, a horse which is dehydrated can struggle to effectively cool themselves. Dehydration can occur whenever a horse isn’t consuming water with enough frequency, and its occurrence is not limited to just hot and humid conditions.
“The horse’s thirst reflex doesn’t work like ours,” says Hiltz. “They don’t start drinking as early as they should, and they lose electrolytes through their sweat. It is not true that a horse will just drink when they need to.”
When a horse is dehydrated the blood becomes less viscous, and the heart has to work harder to push it around. A hanging elevated heart rate, especially in a fit, high performance athlete like an endurance horse or eventer, can often be due to the effects of dehydration. In addition, a dehydrated horse will not produce enough sweat to cool themselves effectively.
Another sign that a horse might be in trouble is if they have been sweating and then suddenly stop. A horse in this condition will usually feel warm or hot to the touch and is likely to have an elevated heart and respiratory rate. It is imperative to get them to shade and cool them with water immediately. Veterinary intervention may be required.
Panting, which is when the horse takes rapid shallower breaths, can be a normal way of cooling. But if the rate of panting doesn’t slow within 20 minutes, that is a sign that the horse is struggling to get oxygen moving. “Get that horse’s tack off and move them to a cool spot,” advises Hiltz.
Taking the time to properly cool out your equine athlete by enhancing their own natural mechanisms can ensure that their body returns to its normal resting condition efficiently. The cool out process allows horses to return to homeostasis and recover from their day’s work.
*All content is for informational purposes only. Contact your veterinarian if you have any questions or concerns about the health of your animals.
About the Author
Christina Keim is a self diagnosed equine addict who has been around or on top of horses for a nearly uninterrupted span of over thirty years, when she was first given riding lessons “just for the summer.” She has enjoyed and experienced many disciplines including hunters, equitation, jumpers, dressage, eventing, Pony Club and most recently competitive trail riding. Christina is based at her Cold Moon Farm in Rochester, NH, and holds an M.Ed. from the University of New Hampshire.
