THERE was a time when Irish horse owners worried chiefly about rain-softened ground, flooded gateways and rugged-up horses standing in draughty yards. But summers are changing. Heatwaves, once considered more unusual, are now arriving with increasing frequency and, with them, comes a growing responsibility to understand how horses cope with heat stress, particularly those expected to train, travel and compete.

From racehorses in busy parade rings to young ponies at local shows, hot weather places significant physiological demands on horses. And, while equestrians are becoming more aware of the dangers, experts say there is still a tendency to underestimate just how quickly a horse’s body temperature can rise.

“Horses are elite athletes, but they are surprisingly inefficient at losing heat,” explains veterinary research from the Fédération Equestre Internationale (FEI) and the American Association of Equine Practitioners (AAEP). During exercise, around 70-80% of the energy a horse produces becomes heat rather than motion. Unless that heat is dissipated effectively, internal body temperature can climb rapidly.

Sweat evaporation

Unlike humans, horses rely heavily on sweating to regulate body temperature. An exercising horse can lose between 10 and 15 litres of sweat per hour in warm conditions, and in extreme circumstances considerably more. Sweat evaporation is therefore critical.

Humidity plays a major role. On muggy days, sweat does not evaporate efficiently, meaning horses struggle to cool themselves, even if they appear drenched. This is why heat stress can occur in Ireland and Britain at temperatures that might not seem particularly extreme.

Additional welfare

Research published by the FEI’s Equine Welfare Advisory Group has highlighted the importance of the Wet Bulb Globe Temperature (WBGT), which combines heat, humidity, wind and solar radiation to assess environmental risk. Many international competitions now use WBGT readings to determine whether additional welfare precautions are required.

Competition environments present unique challenges. Horses may spend hours travelling in poorly-ventilated lorries before standing on warm concrete, fully tacked up, waiting for classes. Racehorses in particular experience multiple heat stress points; transport, saddling, parade rings, exertion and post-race recovery.

At major race meetings and FEI competitions, cooling protocols are now increasingly sophisticated. Ice water, aggressive cooling station fans, and veterinary heat monitoring have become standard at elite level.

The science behind aggressive cooling has evolved significantly over the last decade. Traditional fears that cold water could “shock” muscles are now largely outdated. Studies from the University of Queensland and FEI veterinary guidance show that repeated application of cold water over large muscle groups, combined with scraping and reapplying, is one of the fastest and safest ways to reduce core temperature in overheated horses.

The key is speed.

Veterinarians generally advise that if a horse shows signs of heat distress - elevated respiratory rate, prolonged recovery, lethargy, muscle weakness or rectal temperatures above 40°C - immediate cooling should begin without delay.

Warning signs

Early signs are not always dramatic. A horse experiencing heat overload may simply appear unusually quiet, reluctant to move forward or slow to recover after exercise. Persistent panting, flared nostrils and excessive sweating are obvious warning signs, but a horse can also stop sweating altogether in severe cases: a dangerous condition known as anhidrosis. Other symptoms may include:

In racehorses and event horses, dehydration can also affect performance and increase the risk of metabolic problems and tying up.

Climate experts predict warmer summers and more frequent heat events across Ireland and Britain in the coming decades. That means heat management is no longer a niche issue reserved for international endurance competitions in the Middle East, it is becoming part of everyday horsemanship.

Most horse owners recognise obvious distress when they see it. The greater challenge is understanding how early intervention, hydration and cooling strategies can prevent a horse ever reaching that stage.

Good horsemanship has always depended on observation. In hot weather, that vigilance becomes even more important. Because when temperatures rise, welfare cannot become secondary to schedules, competition plans or racing calendars. Horses may be powerful athletes, but they remain remarkably vulnerable to heat and the responsibility for managing that risk rests with us.

HYDRATION management has become increasingly scientific in professional yards. A horse may drink 25-55 litres of water daily in normal conditions, but considerably more during hot weather and exercise. Yet many horses drink poorly away from home, making travelling horses especially vulnerable in hot weather.

Electrolyte replacement is now common practice in performance yards because sweat contains substantial losses of sodium, chloride and potassium. However, experts caution that electrolytes should never replace access to plain clean water.

Feeding wet feeds, soaked hay and offering water frequently during transport can all help maintain hydration.

Interestingly, studies suggest horses often prefer lukewarm water to ice-cold water after exercise, and may drink more readily when familiar flavours or feed mashes are offered.

Exercise schedules

Many trainers and riders are now adjusting exercise schedules to avoid peak afternoon heat. Early morning work has become increasingly common during warm spells, particularly for racehorses and event horses undertaking fast work. The same applies to amateur riders. Even relatively low-intensity exercise can become dangerous in high heat and humidity, especially for overweight horses, older horses or those with underlying respiratory conditions.

Black-coated horses and heavily muscled horses may also absorb and retain more heat.

Travel tips

in hot weather

TRANSPORT remains one of the most underestimated risks during hot weather. Research has shown temperatures inside horseboxes can rise rapidly, particularly in stationary traffic. Poor ventilation significantly impairs heat dissipation, while stress itself contributes to elevated body temperature.

Many welfare organisations now advise avoiding long journeys during the hottest part of the day where possible.

For racehorses and competition horses travelling significant distances, professional transporters increasingly monitor internal temperatures carefully and schedule strategic rest stops.

Planning journeys to minimise delays can help.