Cooling out is the process of helping your horses body return to his normal, resting state after exercise. This includes more tha just bringing down his body temperature.
Although the wild horse's pace is more energy conserving, he gets a lot of conditioning. Roaming the ranges all day, instead of being confined to a stall or limited area, results in strong muscles, bones, tendons and ligaments and a cardiovascular fitness that is difficult if not impossible to achieve under domestic conditions.
One reason why your horse needs cooling out is that domestic horses can't build and maintain the natural strength and fitness the wild mustangs achieve under natural conditions in the wild.
The main time you would see a mustang galloping for a long session up and down hills, cuttting, jumping, ring style work or something to achieve the work out we give domestic horses is when they are being chased. Mustangs will slow down when they feel like it and only exert themselves when necessary. We don't allow our horses to do that. We let them go until were ready to stop, some knowing when is appropriate, some not. This slowing down allows the horse to catch their breath, a gradual return to normal temperature, pulse and respiration.
As the horse heats up, blood flow to the skin increases, again at the expense of internal organs. THe horse's metabolism greatly speeds up to generate the needed energy for exercise. Hormonal changes occur both during and after exercise. Electrolyte patterns shift in the exercising muscle and in the blood. Tendons are repeatedly lengthened and shortened, and the joints are put through various ranges of motion. Even the nervous system gets a workout.
Exercise also generates a tremendous amount of heat, which the horse must get rid of to avoid damaging the internal organs and brain. Waste products, such as lactic acid build up in the muscles and the blood, must be excreted. The horse looses fluids, both in sweat and by evaporation along the respiratory tract. Electrolytes are lost in sweat and in urine if exercise is prolonged.
Failure of the horse to return to his normal resting state as quickly as possible can result in dehydration, overheating or heat stroke, metabolic abnormalities and cramping of the muscles.
This slow walking also begins the process of bringing the heart rate back to a normal level. Blood begins to be redistributed back to the intestinal tract, liver and kidneys. The liver and kidneys then assist in the processing of waster from exercise and intestinal tract function returns to more normal levels.
Sweating will decrease as the pace is slowed, and breathing will slow. By allowing the horse this time of slow walking before you dismount, untack and give him a bath, you help avoid muscle cramping, which can result when exercise stops suddenly.
After walking under saddle, bring the horse in, remove all tack and give him a bath. Plain water is fine. You can also use one of the many liniments of braces designed for use after exercise. These cut through grease and sweat and open the pores. Heat is transferred from the horse to the bath water, so you'll want to either continue running water over the horse for a few minutes while he cools or scrape the hot water off him so evaporation can aid the cooling process. Ingredients such as witch hazel and alcohol also help the horse to cool out quicker since they evaporate readily.
If he seems very hot or stressed, take the horses temperature before giving the bath. Temperatures in the 105 range mean the horse is in danger of heat stroke. Hose him with liberal amounts of cold water until his temperature comes down to 103* or lower. Check the horse's respiratory rate also (count the number of breaths per minute)> An upper-normal range is about 16 to 18. The more overheated/distressed the horse is, the higher his respiratory rate will be. Horses that are obviously working hard (heaving to breathe), with temperature elevated in the danger zone, should be hosed until they become more comfortable. If no improvement is seen within five minutes, call the vet.
You may have heard it is not a good idea to hose the large muscles of the hindquarters with cold water as this could produce cramping or tying-up. Controlled studies found no evidence this is true. Common sense tells you to use water that is cool/tepid rather than icy unless the horse is dangerously over heater, simply to avoid having sensitive horse "scrunch down" and tuck their tails when you hose them.
There fore, except for comfort, there is little reason to be worried about using cold water on the hind end. An exception to this might be ahorse that is already crampy/tight over the hindquarters after work. You still want the muscles to cool down but don't want the horse to contract them further in response to the water. Tepid water will relax the horse, hasten cooling and allow circulation to continue, washing out the metabolic wastes from the muscle.
You may also have heard that you should always hose off the legs of the horse first. There is no practical reason to do this. The horse will cool by evaporation, conduction and convection from all body surface areas equally well. To help cool the interior of the horse more quickly, apply ice or cold water over the groove in the neck where the large jugular vein runs. This carries cooled blood directly to the lungs and heart.
For horses who are jumpy, sensitive to water temperature or objection general to being hosed, hosing the legs first may be preferred. ONce the horse has stopped fidgeting and has accepted having his legs hosed, you can gradually work upward to the upper limbs and then the body and head.
After the first drink of water, begin walking the horse in a cool and shaded area. The horse should not be blanketed unless the air temperature is low enough to cause shivering. Blanketing slows the cooling-out process. (An exception to this might be a horse who is obviously experiencing cramping in the hindquarters. Massage and cover the area with a towel or light blanket to encourage blood flow during cooling out and help relieve the cramping.)
Antisweat sheets are mesh blankets for cooling out in hot weather. They allow the heat to escape (instead of trapping it as other blankets do) and don't promote sweating. These sheets work well but no better than a regular fly sheet, which also allows efficient heat escape while providing protection from insects.
The observant rider may note an interesting phenomenon at 5 to 15 minutes after exercise has stopped: The horse may have seemed fairly comfortable, with respiratory rate coming down nicely, but he then begins to breathe more rapidly. This is probably related to the muscles "dumping" a load of waste into the blood at this time and is most likely to be seen when horses have worked very hard and work was stopped suddenly without a cooldown under saddle.
Continue cooling the horse but keep an eye on the respiratory rate. It should fall again fairly quickly as you continue walking. If it does not, recheck the horses temperature. He may need hosing again. If his temperature has not gone up again, check for a cause of pain, such as a cramped muscle or pulled tendon.
A common mistake is putting the horse away too soon. A dry coat is not a reliable indicator that the horse has cooled out, especially true if the humidity is low. Putting the horse into the stall too quickly may result in him sweating and even blowing again.
A better indicator is the horses temperature. Temperature should be 101* or less before you put the horse away in a stall and leave him. He should also have had his fill of water and be interested in eating by this time. A horse whose coat has dried, whose body and ears feel cool to the touch (ears will always feel cool if the horse has been cooled out properly), has had his fill of water and has a temperature in the range of 101* to 102* can be safely turned out to continue his cooling out.
It is fine to allow the horse some grazing during cooling out as long as he has stopped blowing and sweating. Once you think the horse has been cooled out using the guidelines described, put him away and observe him for 10 - 15 minutes. If he still appears normal, he can be safely given hay, but wait at least an hour for feed.
Horses can replace most, if not all, of the electrolytes they lose from their diet, especially if they are not worked heavily every day. However, horses that are working regularly in hot weather, that tend to become dehydrated easily and horses that have a tendency toward any muscle soreness may benefit from electrolyte supplementation.
Finally after an exercise session, check the horse's legs and muscles before going home. Lameness, filling of tendons and ligaments, even muscle soreness may take hours to appear or be noticed. Run your hands down the legs. Check the hooves for coolness, no swelling and that all legs have the same temperature.
Exert gentle pressure with your finger along the muscles of the back and rump. If not tender, the horse will show no reaction. If tender, the horse will flinch, tighten up or sink down away form the pressure. e may even kick. If there's a significant problem, call the bet for advice. If an area seems suspicious, but the horse is generally comfy make a mental note to check on him again later.