As summer approaches, and the weather heats up, so does the competitive season for horse shows, racing and other equine events. This is the time of the year that severe heat-related stress occurs in equine athletes.
Heat Stroke also known as heat exhaustion or hyperthermia, heat stroke is a condition that occurs with horses performing a great deal of work in excessively hot or humid conditions. When the horse is unable to lose body heat, its body temperature goes up rapidly, causing severe (and sometimes fatal) health concerns. Problems develop and the cooling system breaks down during hot, humid weather when sweat doesn’t evaporate and adequate cooling cannot take place. The result is heat stress, which often leads to heat exhaustion or life-threatening heat stroke.
Signs &Symptoms
Such as
- Reduced skin elasticity
- High Rectal temperature ( More than 1030F)
- Slow capillary refill time
- Rapid Shallow breathing
- Muscles tremor
- Dark Urine Color
- Decrease performance
- Anhidrosis (failure of the sweat glands)
- colic due to decreased water content of digesta
- Hyperthermia may all be due to heat-induced disruption of the horse’s normal water and electrolyte balance. Many horse owners don’t realize that only about 25% of the energy used in the performance horse’s working muscles is converted to actual muscle movement. The remaining 75% loss of efficiency is represented by waste heat that becomes very difficult for the horse to dissipate in hot and humid weather
Signs of Dehydration 
- Dry or tacky gums
- weak, fast pulse
- Sunken eyes
- CoolExtremities
Nutrition contributes to managing heat stress?
Electrolytes – A racehorse can lose up to 10 liters of sweat per performance (work/race). This fluid isn’t just water – it contains a lot of salt. These salts, when broken down into their chemical components, are referred to as electrolytes. These are typically groups of different salts that contain such electrolytes as sodium, potassium, chloride, magnesium and calcium. Electrolytes govern the transfer of water through cell membranes into or out of the cells. Thus, they function in getting the nutrients in and the waste products out.
If we don’t provide at least a minimum electrolyte replacement, horses show up with such medical conditions as metabolic alkalosis, inefficient transport of oxygen and energy substrates, poor tissue perfusion, thumps, muscle spasms, exertional rhabdomyolysis, cardiac arrhythmias, gastrointestinal stasis, anhidrosis, kidney impairment, and poor recoveries. (Actually, poor heart and respiratory recovery is one of the key signs that can lead you to recognize the problems associated with the task of accomplishing thermoregulation.)
The point is, most of these problems mentioned stem from the resulting dehydration and electrolyte imbalance.Thus, it is essential to correctly manage and supplement horse’s diets with electrolytes.
Low Heat Feeding
Many equestrians would know about cool feeds, but what we are referring to is feeds that do not provide much heat as a result of fermentation in the hindgut. This is done by processing grains by, processes such as Micronizing. This enables nearly all of the starch in the grain to be digested in the small intestine, which results in little or no heat produced. Thus the hindgut only has to digest the fibre in the horse’s diet, which in turn dramatically reduces the amount of heat generated by fermentation.
Fat is digested quite efficiently in the horses’ small intestine and does not produce any heat whil
st being digested. The problem however is that high fat feeds in the tropics can quickly go rancid and moldy. Anti-oxidants and mold inhibitors can be added to these feeds, which provided they are stored correctly will greatly prolong the effective use by date of the feed.
Elevated environmental conditions reduce the horse’s appetite. Micronizing improves feed efficiency, thus less feed is required to be fed to the horse. Also the Micronizing process actually
enhances the palatability of grains and is a useful tool to help keep horses eating during times of environmental stress.
Should I work My Horse Today?
A practical test to determine whether it is safe to work your horse is the
“Effective temperature” test, used to help determine the environmental conditions most likely to result in heat related illness in an exercising horse. This test combines ambient temperature with relative humidity.
To convert Celsius into Fahrenheit F =( 9 * C / 5) + 32
How does a Horse Chill Out?
The single most important means the horse has for getting rid of the enormous heat load generated during exercise is evaporation. This accounts for approximately 65% of the heat dissipation. Sweat is evaporated off of the skin surface and cools the horse. The lungs account for approximately another 25%. The capacity of the respiratory tract to dissipate heat from the body becomes very important under conditions of high humidity and high temperature when evaporative conditions are not favorable.
High humidity makes evaporative cooling less efficient. The combination of high temperature and high humidity combined can lead to serious trouble quickly. Direct sunshine on a clear day intensifies the problem.
How Can I Manage Heat Stroke?
- 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 horse’s 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, 60 gram of salt .
- 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).
- Stick to the shade and avoid strenuous exercise between noon and 3pm.
- Remember that weather forecasts quote the temperature in the shade, so a horse out in a field with no shade or shelter and limited water supply can suffer bad heatstroke
- Avoid leaving horses standing in horseboxes or trailers in direct sun.
- Do not leave your horse shut in a hot stuffy stable when there is no breeze.
- Allow small drinks at intervals during exercise – even before competing.
- Give soaked hay and sloppy, wet feeds to help get water on board.
- Rapid rehydration will not be possible with water alone as electrolytes, particularly sodium, are needed. There are a variety of commercially available equine oral replacement electrolyte solutions on the market, but it is important they are made up at the correct concentration and that your horse will take them. Adding apple squash or apple juice helps to mask the taste
- It is worth giving electrolytes before strenuous exercise as a preventative measures.
