First, stop riding, remove the saddle and move the horse into the shade. Keep him walking, to encourage circulation that will bring more heated blood to the surface of the skin for cooling; if there's a breeze, walk him in circles to expose him to the cooling air on all sides.
Let him drink his fill as soon as you stop working and as you walk him. A hot horse needs to take in as much water as he wants to replace what he lost though sweating. And don't worry about the temperature of the water. One myth that still crops up is the notion that letting a hot horse drink cold water will cause colic and muscle cramps. But there's no scientific basis for that fear.
Splash or spray cold water onto the horse to aid evaporative cooling. Another false notion is that putting cold water on hot muscles will constrict the blood vessels and lead to cramping; however, studies done in preparation for the Olympic Games in Atlanta in 1996 failed to identify any ill effects from the practice. "We disproved the myth that if you put cold water over the big muscles the horse would tie up," Allen says. In fact, cooling stations, where hot horses will be doused head to toe with cold water, are one of the strategies to be employed for the 2008 Olympic equestrian games in Hong Kong.
"Cooling the horse with [room temperature] water all over the body is fine in a hot, dry climate," says Marlin. The water will evaporate quickly into the dry air. "If it's hot and humid, you need water that's lower in temperature than the horse." Add ice to buckets of water to cool it to as low 40 degrees F before applying it to the horse. If the horse's body temperature is edging upward into the danger zones--105 degrees F or higher--douse as much of his body as possible with the coldest water available.
If dousing the whole horse is difficult, you can achieve some cooling by wetting down or holding ice on areas where large veins run close to the surface of the skin, such as the jugular. "You can do the same thing up between the hind legs, if the horse is used to this, since the veins are very distended in that area," Allen says. But don't "surprise" a hot horse with this tactic, he advises. Even just the legs provide about a quarter of the body's surface area, and the arteries and veins running have little insulation from muscle and fat. "There's a lot of blood circulating through the feet," says Barney Fleming, DVM, who practices in Custer, South Dakota, and monitors endurance rides all over the country. "If there's a stream nearby, just walk the horse in, stand him in the water and use it to keep wetting his jugular groove and abdominal veins."
Continue to monitor your horse's temperature as you walk and cool him. Within 10 minutes, you ought to see a 2 degree F drop. Stop using the cold water once his temperatures drops to 101 degrees or lower, his respiration approaches normal and the skin on his hindquarters feels cool to the touch after a walking period. If the horse is not back to normal and drinking readily within an hour, then summon immediate veterinary assistance. He may need intravenous hydration and other measures.
To read more, see "Heat Stress Prevention Strategy" in the July 2008 issue of EQUUS magazine.
