Hot weather presents an important challenge for horse owners, making it essential to adapt daily care to help prevent horses from becoming dangerously overheated.
Horses naturally regulate their body temperature by sweating. As sweat evaporates from the skin, it creates a cooling effect. However, sweating alone is not always enough to reduce body temperature quickly, and excessive heat can lead to heat exhaustion. If body temperature continues to rise, serious complications including organ failure, brain damage and other potentially fatal conditions can occur.
Recognising the Signs of an Overheated Horse
Although heavy sweating is commonly linked with overheating, breathing rate can also provide valuable information about a horse's temperature.
According to equine scientist Dr David Marlin, there is a common misunderstanding that horses breathing heavily after exercise are short of oxygen. He explains that, by the time a racehorse finishes a race, blood oxygen levels have already returned to normal. Instead, increased breathing is driven by elevated body temperature, making heavy breathing an indication that the horse is still very hot.
Other signs of a raised body temperature include wobbling, feeling hot to the touch, excitement, stress, depression, lethargy and a lack of interest in surroundings.
Exercise is not the only cause of overheating. Horses can also become dangerously hot when confined in situations such as a horsebox or a warm stable during very hot weather.
The Fastest Way to Cool a Horse
Dr Marlin advises that the quickest method of lowering a horse's body temperature is to continually apply plenty of cold water. Whether the water comes from a hose, a river or a pond, the quantity of water used is more important than the source.
He explains that horses finishing races, cross-country rounds or even dressage tests can become extremely hot, and this is why they are often cooled extensively with water immediately afterwards.
According to Dr Marlin, continuous application of water remains the most effective and fastest way to restore a horse's normal body temperature.
Why Water Volume Matters More Than Temperature
The effectiveness of cooling depends less on the exact temperature of the water and more on the amount applied. Water between 10°C and 25°C is suitable.
Studies show that continuous water application removes heat by conduction, transferring heat directly from the horse into the water. This works because there is a significant temperature difference between the horse's skin, which may exceed 40°C, and the cooler water.
If the water is the same temperature as the horse, cooling relies only on evaporation, which is a much slower process.
Why You Should Not Use a Sweat Scraper
Many owners routinely scrape water from their horses after hosing them down. However, Dr Marlin explains that this actually reduces the effectiveness of cooling.
Leaving the water on the horse allows conductive heat transfer to continue, removing heat much faster than evaporation alone. By scraping the water away, the horse loses much of this cooling benefit.
On hot days, allowing the water to remain on the horse helps keep it cooler for longer.
Knowing When Your Horse Has Recovered
Quickly spraying a horse or pouring a single bucket of water over it before turnout may help provide some temporary cooling through evaporation, but this is not an effective way to rapidly lower the temperature of an overheated horse.
Cooling should continue until signs of recovery become apparent.
Dr Marlin advises that the best indication is when the horse's breathing returns to its normal rate. Owners can also monitor heart rate and body temperature with a thermometer, although rectal temperature may return to normal more slowly than other signs.
Knowing a horse's normal vital signs makes it easier to recognise when something is abnormal.
He also explains that there are effectively no disadvantages to cooling a horse in this way. While a horse that begins shivering may have become slightly too cool, it is not realistically possible to overcool by applying water.
Allow Your Horse to Drink
Dr Marlin recommends including drinking as part of the cooling process because horses usually want water immediately after exercise.
He advises avoiding water that is extremely cold, below 10°C, or very warm, above 35°C. Horses generally prefer drinking water at around 25°C.
Although drinking colder or warmer water will not harm them, horses tend to drink more when the water is at a moderate temperature.
Understanding Heat Stress
Heatstroke is a genuine risk for horses during periods of high temperatures.
Symptoms include restlessness or lethargy, a rapid pulse and breathing rate, increased sweating, excessive salivation, redness inside the mouth, high body temperature, irregular heartbeat, muscle spasms, stumbling and, in severe cases, collapse.
If any of these signs are seen, or if there is any uncertainty, veterinary advice should be sought immediately.
Dr Marlin explains that while most horses cope well with hot weather in the UK, certain horses may be more vulnerable. These include older horses, young horses, overweight horses and those with health conditions such as heart disease, equine asthma, Cushing's disease, laminitis or a tendency towards colic.
He adds that horses generally cool quickly after strenuous exercise during cooler weather because the surrounding air temperature is much lower. Greater concern arises when both the horse and the surrounding environment are very hot.
Humidity and Electrolytes
Humidity also affects a horse's ability to cool itself. As humidity rises, sweat evaporates less effectively, making continuous application of water even more important because conductive cooling becomes increasingly significant.
Dr Marlin explains that in the UK, horses usually lose heat through convection because air temperature is lower than skin temperature. Applying cold water also removes heat through conduction.
In humid conditions, horses remain uncomfortable for longer, recover more slowly and face a greater risk of heat-related illness if left to cool naturally.
Hot weather also increases sweat loss, leading to greater electrolyte losses.
Dr Marlin states that many horse diets are deficient in sodium. For a 500kg horse, he recommends adding 25ml of salt daily together with a balanced electrolyte according to the level of work. Electrolytes should replace those lost through sweat, and he notes that a slight excess is preferable to providing too little because the kidneys remove any surplus.
Helping Horses Stay Comfortable During Hot Weather
On hot days, brick stables with good ventilation may be cooler than turnout, while wooden stables can become extremely warm.
Paddocks with trees or open field shelters may also offer greater comfort, although not every horse chooses to use them.
Unless specifically acclimatising horses to heat, riding should be avoided during the hottest part of the day, approximately between 10am and 8pm in the UK, because horses are not currently acclimatised to temperatures above 30°C.
Fresh, clean water without additives should always be available, as reduced water intake increases the risk of impaction colic.
Poor drinkers may benefit from the addition of 25ml of salt, while soaked feeds can also help improve hydration.
If a horse appears uncomfortable in hot weather, hosing it down and allowing it to dry naturally without scraping the water away can be repeated three or four times each day.
If a horse, person or dog develops heatstroke, cooling with plenty of water from a hose, household supply, river, pond or even bottled water is advised. The water does not need to be ice cold provided a generous amount is used.
Cooling Horses After Exercise in Cold Weather
Even during winter, horses can become very hot following exercise.
If a horse is sweating heavily, feels hot and is breathing hard, the same cooling approach should be followed by applying water until the horse begins to cool.
During colder weather the horse will cool more rapidly, and once its temperature has returned to normal, rugging can be considered to prevent it becoming too cold.
Common Cooling Myths
Dr Marlin explains that several long-standing beliefs about cooling horses are incorrect.
Using cold water does not cause muscle damage, laminitis, shock, heart attacks or prevent cooling through constriction of blood vessels in the skin.
Leaving water on the horse does not insulate the body or reduce heat loss.
It is also not more effective to begin cooling at the feet, scrape water away while cooling, focus only on large blood vessels or cover the horse with wet towels.
Knowing how to cool a horse down quickly in hot weather is essential for protecting horses from overheating. Applying plenty of water continuously, allowing the water to remain on the horse and monitoring recovery signs are key recommendations described by Dr David Marlin. Understanding these principles can help horses recover safely during periods of hot weather.
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