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Walk your horse slowly in the shade. Monitor your horse’s heart and breathing rates. Run cold water all over your horse’s body. Mist your horse with cold water. Offer frequent sips of cold water to your horse. Replace your horse’s electrolytes.
When it’s warm outside, it is especially important to cool off your horse after a ride or workout. To start cooling down your horse, find a shady area where you can walk him at a leisurely pace. Walking helps your horse cool off by creating a small breeze and keeping his blood circulating through his muscles and skin.  The blood circulation helps remove waste products, such as lactic acid, from your horse’s muscles that accumulate during exercise.  How quickly a horse cools down can depend on several factors, such as age and overall health. Although there is no set amount of time for you to walk your horse, plan to walk him for at least 10 to 15 minutes to start the cooling down process. Your horse’s heart and breathing rates will have gone up during exercise, so he will need some time to bring them back down to normal. While you are walking your horse, find his pulse by placing three fingers on the blood vessel that runs underneath and inside of his lower jaw. To calculate his heart rate, count his pulse for 15 seconds, then multiply by 4.  A horse’s normal heart rate is 30 to 40 beats/minute. After exercise, your horse’s heart rate could be as high as 140 to 200 beats/minute.  Watch your horse’s flank rise and fall to count the number of breaths/minute. Count the breaths for 15 seconds, then multiply by 4. Your horse normally takes 8 to 16 breaths/minute. Right after exercise, your horse will likely be taking big breaths, but his breaths will become more shallow as he cools off. Those big breaths allow excess heat to exit through his lungs.  A breathing rate that is faster than the heart rate could signal a serious health problem. Call your veterinarian if this is the case for your horse. Monitor your horse’s heart and breathing rates throughout the cooling off process so you know when they return to normal. In a process called evaporation, your horse will naturally sweat to release excess heat. If you exercise your horse on warm days, though, sweating probably will not be enough to cool him off sufficiently. Running cold water over your horse, with either a sponge or hose, will be a tremendous help in cooling him down.  On hot days, or after a particularly vigorous workout, start with running cold water over your horse’s chest, the large jugular grooves running down his neck, and his lower legs. These areas have small blood vessels that can carry cooled blood to the rest of his body and help him cool off more quickly.  You can also hose off your horse’s large muscle groups first (e.g., back, glutes), since they tend to hold a lot of heat.  The cold water helps your horse stop sweating earlier, which can prevent him from becoming dehydrated. It is a myth that hosing down a horse with cold water will harm him.  If you choose to use a sponge, you may want to have someone help you so you can sponge more of your horse’s body more quickly. Alternate between applying cold water for about 30 seconds and walking your horse. It is important to keep your horse moving throughout the cooling off process.  You will know your horse has cooled off sufficiently when the water running off underneath his body feels cool to the touch. An alternative to sponging or hosing down your horse is misting him with cold water. When moisture is absorbed from the skin with misting, that moisture takes some of your horse’s excess heat with it. If you already have a misting system set up, you can use this to cool down your horse.  You may find that frequent misting is more effective at cooling off your horse than hosing him down.  If you do not have a misting system, consider adding a nozzle to your hose that has a ‘mist’ setting. You may want to consider installing a sprinkler system just outside your pasture that can periodically mist your horse with cool water to keep him cool. During exercise, your horse’s digestive system slows down. The blood that would normally go to his gut to fuel digestion instead goes to his muscles. As your horse cools down, his digestion will still be on the slow side, so gulping water quickly would not be a good idea for your horse.  If he drinks water too quickly, he may develop colic or muscle cramps.  As you are walking your horse, offer him small sips of cool water from a bucket. Keep in mind that, if he’s still breathing hard, he may not be ready to drink water. Continue to offer it to him, and he will drink when he’s ready. Although sweating will help your horse cool off, the sweat contains important electrolytes, such as salt and potassium. Electrolytes help maintain your horse’s nerve and muscle functions, so it is very important for you to replenish these electrolytes after he exercises. One way to replenish them is to give your horse a pre-formulated electrolyte paste via a dosing syringe.  Since your horse’s digestive system will still be a bit slow right after exercise, you may want to wait until he has fully cooled down before offering him the paste. Electrolyte powders are also available that can be added directly to your horse’s water.  Your horse may not like the taste of ‘electrolyte-laced’ water. If this is the case, offer him plain water instead.  Follow the label instructions carefully to avoid overdosing your horse on electrolytes. Speak with your veterinarian if you are unsure about the most effective way of replacing your horse’s electrolytes.