Horses have a relatively small surface area to body mass ratio, which makes thermoregulation a challenge in hot and humid conditions. As such, horses tend to need aggressive cooling to prevent exertional heat illness after strenuous exercise in hot and humid conditions. A recent study, conducted in Japan, compared various methods for cooling horses in such conditions.
Five Thoroughbreds were exercised on a treadmill at an average temperature of 89°F until their pulmonary artery temperature reached 108°F. The time until the pulmonary artery temperature returned to <102°F and the rectal temperature at 30 minutes after the onset of cooling were compared between five cooling methods including: 1) walking, 2) walking with fans, 3) walking with the intermittent application of cold water (50°F), 4) walking with the intermittent application of cold water with scraping, and 5) stationary with continuous tap water (79°C) application.
The stationary with continuous tap water application produced the shortest time to return to a pulmonary artery temperature <102°F, which averaged 2 minutes. The intermittent application of cold water produced the next shortest time length with an average of 10 minutes, while adding scrapping to that protocol lengthened the time to 12 minutes. Simply walking the horse took the longest time and averaged 25 minutes, while walking plus the fan took 15 minutes. All cooling methods resulted in lower rectal temperatures at 30 minutes compared to walking. Continuously showering the horse with cool tap water was the most effective method to decrease core temperature in horses.
This study demonstrated that showering horses continuously with tap water was superior to the intermittent application of cold water for cooling a hot horse after exercising in hot and humid conditions. The essential feature was not the water temperature or the use of scraping, but that the horse was kept covered in water cooler than its body temperature over an extended period.
For more information on this research, click here.
Research summarized by Krishona Martinson, PhD, University of Minnesota