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Signs Your Horse May Have Heat Stress

Well, i'm from Australia, and as we all know, it gets quite hot down under, with temperatures reaching up to 50 degrees celsius, (120 Fahrenheit), I wish you Americans would ditch Fahrenheit, its hard to convert and spell!

Anyway, I'm known for getting right to the point, signs your horse may have heat stress.

Commonly observed signs of heat stress are:
Profuse sweating.
No sweating.
Rapid breathing rate - panting (>20 breaths / min)
Rapid heart rate (>50 beat/min)
Skin that is dry and hot.
Unusually high rectal temperatures (>38°C) (100 f!!!!!)

During exercise, there is a significant increase in the amount of heat produced by working muscles. Muscles cannot transform energy into movement with 100% efficiency. Horses transform energy to movement at approximately 25% efficiency. As a result, some of the energy is lost in the form of heat. The rate of heat production by working muscles is proportional to how hard the muscles work. Therefore the faster a horse goes the more heat it produces. The amount of heat a horse produces in a 160 km endurance race would be enough to boil approximately 770 litres of water. That's approximately 7.7 litres per mile. Fortunately for the horse, it is able to dissipate around 97% of the heat it produces during an endurance race in cool-warm conditions!! If not, its body temperature would increase by around 15°C/h. In response, a horse increases its sweating rate, moves more blood to the capillaries under the skin and increases its rate of breathing in an effort to release this build up of heat.

Hose horses with cold water. Hose the horse down then take it for a 1-minute walk, then repeat hosing. This will encourage the dilation of capillaries close to the skin, which will increase the evaporation of heat from the horse.
Encourage horses to drink cool water (small amounts frequently). If you are able to monitor the amount of water your horse drinks it will give you a good idea of how much water it is consuming. Horses working in hot/humid conditions should drink approximately 50-70Litres of water per day.
In severe cases vets have been known to give cold-water enemas or drenches to cool the horses core body temperature down to approximately 38°C. The critical temperature, one that is characteristic of a life-threatening situation, if maintained for any length of time, is 40-41°C.
Supplement electrolytes daily. 60g of HYGAIN® REGAIN® and 60g of Salt.
It is important not to overlook cool-down periods following exercise bouts, even when environmental temperatures are well within normal parameters.
Ensure that the horse has plenty of ventilation and access to a cool breeze as convection helps cool horses quicker. If none is available fans / air conditioners can be used to produce an artificial breeze. (Remember poor ventilation in stables can lead to respiratory problems).


Horses that are breathing with great difficulty, appear distressed, become weak, develop diarrhoea or signs of colic, or stop sweating are in serious distress and need immediate attention. A veterinarian should examine the horse as soon as possible and provide medical treatment. You should immediately get the horse into shade and hose or sponge it with cool or even cold water. Direct the hose to the insides of the legs and the head and neck areas where large blood vessels are located near the surface. Use fans and encourage the horse to drink. Offer water, both plain and with electrolytes, and let the horse choose. It may take an hour or more to get all the vital signs back to normal. Horses that have seriously overheated tend to be more susceptible to overheating in the future. Horses that have suffered a serious episode should have 10 to 14 days of rest with some turnout and a gradual return to work. If a horse develops these symptoms in tropical environments such as Asia, they should be sent to higher elevations to be rested, as it is generally cooler and less humid. Thus horses can recover from heat stress more quickly Most horses adapt to summer weather if given time to adjust gradually. Use a little common sense and keep a close watch on horses for signs of distress. Horses that are overweight and not used to regular hard physical activity are at the greatest risk.


Halting the downward spiral of an overheated horse requires active intervention the moment you recognize the problem. The extent of the measures you need to take depends on how hot the horse has gotten. If he's still alert, still sweating normally, and his rectal temperature reads 104 degrees Fahrenheit or lower, he is overheated but not in danger. "He just needs walking around, letting him drink, and some washing down with cool water," says Allen. "It's normal for a horse to heat this much while working."

But, when a horse starts edging toward severe overheating, more extreme cooling measures are necessary:

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 the horse drink his fill as you walk him out.

A hot horse needs to take in as much water as he wants to replace what he lost through 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.

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