With temperatures forecast into the mid to high 90s this weekend, I’ve been thinking about the best method for cooling hot horses. When it’s hot and humid like that it’s not just too hot to ride, it feels to hot to do just about anything. Just think of how bad it would be if you weighted 1200+ pounds and were covered by fur.

There are a couple of weighs to help horses deal with the heat.

• Make sure your horse has access to shade
• Provide plenty of clean fresh water (we use smaller tubs when it’s really hot out so we dump them and refill with cold water twice a day), and
• Get your horse wet!

One of the myths that I’ve seen perpetuated on the Internet about horse care is that if you hose down a horse but don’t scrape the water off, somehow the horse will get hotter. Yes, the theory is that failure to scrape leads to super-heated water insulating the horse and making them hotter rather than cooler.

Dr. David Marlin, an equine thermoregulation expert, debunked the myth years ago after he worked extensively with the 1996 Atlanta Olympics to ensure competition horses were safe in the hot and humid conditions with research that showed the quickest and most effective way to cool down horses is to continue spraying them with cold water. Taking the time to scrape off the water actually slows down the process. Marlin explained that applying cold water cools a horse in two ways: first, it transfers heat from the horse to the water because of the conductive transfer of heat; and second, the evaporation of water uses energy and cools the surface on which the water sits.

New Study Published by the Japan Racing Association

Dr. Marlin recently posted information about a new study, published by the Japan Racing Association, on his Facebook page.

“A Comparison of Five Cooling Methods in Hot and Humid Environments in Thoroughbred Horses,” will appear in the August 2020 issue of Science Direct. The study looked at the rate of decrease in pulmonary artery blood temperature and rectal temperature after five Thoroughbred horses were exercised on a treadmill in a WBGT index of ~32°C. The horses were exercised at canter until their pulmonary artery blood temperature reached 42°C. Pulmonary artery temperature is considered to be an indicator of “core” (central) body temperature. Each horse was exercised on 5 different occasions and after each exercise was given each cooling treatment in randomized order. These were:

1) Walking – walking on treadmill with a slow fan in front (same speed as treadmill).

2) Walking + Fans – walking on treadmill with two large fans in front blowing at 3m/s.

3) Intermittent Cold water +Scraping – walking on the treadmill. Every 3 min the horse was taken off and cooled over whole body (except head and neck) with 16 litres of water at 10°C. Scraping. Horse returned to walking on treadmill.

4) Intermittent Cold water No Scraping – as above but water was not scraped off

5) Continuous Cool water – horse removed from treadmill. Stood in stocks. Continuous hosing all over with water 26°C.

His Conclusions
➡ By far the fastest method of cooling was the continuous application of cool (26°C) water.
➡ The rate of cooling of the continuous application was 5x faster than the intermittent application of cold (10°C) water
➡ Scraping water off made no difference to the rate of cooling
➡ The factors that determine the rate of cooling are: 1) area covered; 2) temperature difference between horse and water; 3) volume of water applied; 4) rate of application of water.

Reference>
https://www.sciencedirect.com/…/a…/abs/pii/S0737080620302215

Freedom will be delighted because he really enjoys a good hosing, especially if he gets to drink some of the water. I often give the horses an extra spray down when I come to the barn because they look so darned miserable, even when they are in their sheds. I generally leave the wet. In fact, if they are wearing fly sheets I figure getting the sheet wet will help them stay cooler even longer.

How do you keep your horses cool in the summer?