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Chill Out: Researchers Compare Cooling Methods For Equine Athletes

Elite athletes like racehorses and three-day event horses sometimes exercise on hot, humid days, often resulting in high body temperatures that must be lowered quickly before heat-related stressors set in. While much research has been performed on effective cooling strategies, a new study compared several different cooling methods.^*

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Thoroughbreds were exercised on an inclined treadmill until the pulmonary artery temperature reached 107.6 degrees Fahrenheit. One of five cooling methods was then implemented. The methods included:

Walking on a treadmill with one commercial fan placed 6.5 feet in front of the horse set at low velocity to simulate the breeze that would occur if walked outside (control);
Walking on a treadmill with two fans placed 13 feet in front of the horse set at almost twice the airflow of the fans used in the control;
Cooling with intermittent application of cold water (4.2 gallons at 50 degrees Fahrenheit) every three minutes on its body behind the neck, scraping as much water as possible after dousing; two cycles of dousing performed with return to treadmill walking and two low-speed fans in the interim;
Cooling with intermittent application of cold water (16 liters; 50° F or 10° C) every three minutes on its body behind the neck with no scraping; two cycles performed with return to the treadmill and two low-speed fans in the interim; and
Showering continuously with tap water (78.8 degrees Fahrenheit) for 30 minutes with no return to the treadmill.

To determine the most effective cooling method, researchers measured the time necessary for the pulmonary artery temperature to return to 102.2 degrees Fahrenheit or lower, and recorded the rectal temperature at 30 minutes after onset of cooling.

The researchers concluded that showering the horse continuously with a large volume of tap water resulted in the most rapid decrease of both pulmonary artery and rectal temperatures, signifying its effectiveness as a way to achieve cooling in hot, humid conditions.

Sweat production goes hand-in-hand with exercise. Multiple factors determine how much sweat is lost doing any exercise bout (heat, humidity, and work intensity, for example). Light exercise with minimal sweating may induce a sweat loss of 1 quart to 1 gallon, while high-performance horses at the peak of exertion may have losses of 12.25 to 3 gallons.

Because large quantities of electrolytes are lost in sweat, electrolyte supplementation becomes a key factor in managing the diets of performance horses. Choose research-proven electrolytes formulated by specialists in equine nutrition and exercise physiology.

Electrolyte supplementation is not season-specific. Well-formulated electrolytes should be used whenever horses sweat on a daily or near daily basis, no matter the season.

^*Takahashi, Y., H. Ohmura, K. Mukai, T. Shiose, and T. Takahashi. 2020. A comparison of five cooling methods in hot and humid environments in Thoroughbred horses. Journal of Equine Veterinary Science 91:103130.

Sun Worshiper Or Shade Seeker? No Common Denominator For Hot Horses

Though most humans seek shade on swelteringly hot days, horses don't necessarily feel the same way. Even when provided with a respite from the sun in the form of a run-in shed or shade trees, not all horses will use it, though most welfare guidelines recommend offering a horse a place to get out of the sun.

Drs. Iwona Janczarek, Anna Stachurska, Izabela Wilk, Anna Wiśniewska, Monika Różańska-Boczula, Beata Kaczmarek, Witold Kędzierski and Jarosław Łuszczyński created a study to test horses' preference for shade, sun or a mist curtain, which offers immediate cooling capabilities.

The team used 12 Warmbloods that were normally kept in stalls for the study. They turned out each horse for 45 minutes on a sandy paddock on a day when temperatures were between 84 and 89 degrees Fahrenheit and humidity was 42 percent. Almost half the paddock was covered in shade and there was a mist curtain in one corner.

The research team monitored heart variables to determine if the horses' behavior or emotional states were affected when they stood in different areas of the paddock. The scientists found that the horses had no strong preference on the amount of time spent in a particular area.

The horses showed slightly heightened relaxation when standing under the mist curtain, but they displayed similar levels of emotional arousal in all three areas. They showed no signs of overheating when standing in the sun.

The team suggests that additional studies be completed that focus on longer periods of turnout. The ability to choose between sun and shade may be crucial for maintaining body temperature, so the provision of shade for equine welfare is reasonable, they conclude.

Read the full study here.

Study: How To Cool Out A Horse Quickly

Five methods commonly used to cool out horses in hot and humid environment were evaluated to determine which cooled the horses the quickest. The study team used rectal temperature and pulmonary artery blood temperature, which is an indicator of core body temperature, for their findings.

Drs. Yuji Takahashi, Hajime Ohmura, Kazutaka Mukai, Tomoki Shiose and Toshiyuki Takahashi exercised five Thoroughbreds on a treadmill in WetBulb Globe Temperature (WBGT) of nearly 90 degrees Fahrenheit. WBGT is a measure of heat stress in direct sunlight; it considers temperature, humidity, sun angle, wind speed and cloud cover. This is different than the heat index, which only takes into consideration humidity and temperature in shady areas.

Each horse was worked at a canter five separate times until their arterial blood temperature reached nearly 108 degrees F. They were then given a different cooling treatment each time. These included:

Walking on a treadmill with slow fan blowing on the horse
Walking on a treadmill with two large fans blowing on the horse
Intermittent cold-water hosing and scraping while walking on a treadmill. Every three minutes the horse was taken off the treadmill and hosed all over his body, but not his head and neck, with 4 gallons of 50 degree water, scraped and returned to the treadmill.
Intermittent cold-water hosing and no scraping used the same parameters as above, but did not remove the water from the horse
Continually using cool water on a horse that is not on a treadmill. The horse was hosed all over with water that was nearly 80 degrees F.

The team determined that the fastest method of cooling out a horse was continually hosing the horse with cool water. This lowered the horse's temperature five times faster than intermittent hosing with cold water. Scraping off the water did not affect the rate of cooling.