It might seem counterintuitive to put a blanket on a stalled horse on a hot day. But Japanese researchers have learned this idea might not be as far-fetched as it seems.

The catch?

It’s a specially designed ice blanket that appears effective in helping keep stabled horses cool in hot and humid environments.

“Applying this methodology should enable effective reduction of heat stress not only in horses but also in other mammals kept in barns,” said study leader Yuki Ojima, of the Kitasato University School of Veterinary Medicine, in Towada.

Studies have shown that misters and cool water can effectively reduce horses’ body temperature and combat heat stress, the researchers said. However, these aren’t ideal in all situations, particularly when horses are stalled.

“If a horse spends a long time in the stall with its hooves wet, bacteria and fungus will develop,” Ojima said, which can lead to issues such as white line disease or thrush.

And, while fans are commonly used to help cool horses, the team said researchers have shown fans are far less effective than cooling with water.

In recent years, studies in humans have revealed that ice vests are effective in decreasing skin temperature, heart rate, and perceptual strain. Because these garments stay relatively dry compared to applying water, Ojima and colleagues decided to test whether an ice blanket could be an option to help combat heat stress in horses.

The team secured ice packs to a light, waffle-weave blanket; they’d conducted preliminary studies to ensure the ice packs wouldn’t freeze the horses at contact points or increase in temperature too much over five hours in the sun to cool effectively. They said the ice packs were designed to keep three areas of the body cool: the front of the back, the rear portion of the back, and the loins.

The team measured five variables (skin surface temperature, heart rate, respiratory rate, rectal temperature, and plasma cortisol) in 19 horses residing either at the Kitasato University veterinary school or a local private stable and collected measurements three times throughout each day. The horses were stalled (part of their normal daily routine) and not exercised on study days. The researchers conducted the study on days when the ambient temperature was forecasted to exceed 25°C (77°F).

The researchers found that skin temperature on the front of the back decreased over time when horses wore the ice blanket, while it remained unchanged sans blanket; they noted the more pronounced skin temperature difference on the front back compared to the rear part and the loins was likely due to the blanket shifting.

Additionally, they said, horses’ heart rates, respiratory rates, and plasma cortisol levels decreased when horses wore the ice blanket compared to when they did not.

More research is needed to determine how effective the ice blanket is at cooling horses immediately after exercise, Ojima said.

Ultimately, Ojima concluded, “the blanket used in the present study (allowed) for gentle cooling of the horse’s body without the use of water or fans.”

The study, “Effect of Cooling Blanket on Heat Stress of Horses in Hot and Humid Environments,” was published in September 2022 in Animals.