Heat Stroke in Horses
Written by World Horse Welfare Chief Executive, Roly Owers MRCVS and World Horse Welfare Trustee, Sarah Coombs MRCVS
Heat stroke occurs when the horse’s internal body temperature becomes too high and can, in the severest cases, be fatal particularly if the horse is dehydrated or lacking electrolytes. It is important that owners take all precautions to avoid heat stroke occurring.
The key with heat stroke is spotting the signs early and whilst these vary from horse to horse, they can include; excessive sweating, heavy rapid breathing, an elevated heart and respiratory rate, and altered behaviour which can progress from dull/listless to panicky or manic as the condition becomes more serious. Individual horses cope differently with hot or humid weather conditions so it is important to know what is normal for your horse in order that you can spot any changes as soon as they occur.
Horses can become acclimatised to working in hot conditions by careful exposure to gradually increasing periods of exercise in the heat. If your horse has not been acclimatised, or the weather suddenly becomes very hot, try to avoid prolonged or intense periods of exercise in hot conditions and similarly avoid exercise during the hottest times of the day. Remember that increased humidity will reduce the horse’s ability to lose heat through sweating so that conditions of high temperature combined with high humidity make heat stress more likely to occur.
Finish your exercise session with walking to begin the cooling process. When back at the yard or water point, remove all tack as quickly as possible and then wet the whole horse with copious quantities of cold water. Work from both sides of the horse and ensure that the large veins on the inside of the legs and down the neck are continuously cooled. As cold water is continuously applied it will displace the water that warms up on the horse’s skin so that scraping off in between applications of water is not necessary. Walk your horse lightly whilst cooling to aid circulation and help him to cool down more effectively. Do not apply wet towels or cooler rugs during the cooling process.
Ensure that your horse has free access to water at all times and if you do need to exercise him strenuously in hot weather, they will need supplementation with electrolytes in feed and drinking water to assist with rehydration. Remember that the horse may need time to accept electrolyte water with so offer a choice of plain water as well.
Utilise any shade that may be available and avoid rugging your horse as this can cause their temperature to become artificially elevated.
If your horse has a particularly thick coat or if you exercise them strenuously during hot weather then consider clipping them to help him to regulate his body temperature. Lean horses adapt better to hot conditions and lose heat more effectively, so that overweight horses are more at risk of heat stroke so take extra care with them.
Trailers and horseboxes can become very hot inside when the weather conditions are warm so try to avoid travelling your horse in these conditions and if you do have to travel ensure you have plenty of water on board and ventilate the vehicle as best you can. Park the vehicle in the shade before loading to reduce loading temperature. You may wish to consider travelling at night if the temperature is lower. Horses lose significant amounts of water when travelling in hot weather especially; around 2-3 kg / hour of transport. If you have a long journey it is essential to allow the horse at least 24-48 hours to recover before exercising strenuously.
If you suspect that your horse is suffering from heat stroke, you should cease any exercise immediately, call your vet and cool the horse as quickly as possible as detailed above. Remember to keep the horse moving while cooling. In the unlikely event that the horse collapses, maintain the cooling from a safe position until veterinary help arrives.