Don't Restrict Horses to Shelters in Hot Conditions

Common sense might say that if horses in hot, sunny conditions have access to a shade structure, they’ll use it. However, horses in these environments might not be a shelter-dependent as owners would think.

Betsy Greene, MS, PhD, professor and equine extension specialist at the University of Arizona, and colleagues recently conducted a study to find out how much time horses spent in the shade in desert conditions. She presented their findings at the 2019 Equine Science Society Symposium, held June 3-6 in Asheville, North Carolina.

The University of Arizona’s (UA) Campus Agricultural Center is home to an approximately 70-horse training and research herd. Until recently, said Greene, the desert facility’s paddocks didn’t have shade structures, which led to an outpouring of concern from the surrounding suburban community. So, in 2016 UA added shelters to its pens.

“Erecting shade structures did not decrease complaints, even generating a new demand to tie the horses, forcing them to use the shade structures during the summer,” said Greene.

This prompted her and her team to gather data on the horses’ actual voluntary use of the shelters. They aimed to find if horses spent more time in the shade and less time being active as the heat index (a measure indicating the level of discomfort the average person is thought to experience as a result of the combined effects of the temperature and humidity of the air) increased.

During the summer of 2017 Greene fitted her two sets of study horses (five geldings and six mares) with GPS tracking collars and rotated each group through four paddocks over a four-week period. She gathered temperature and humidity data hourly and used the GPS data to observe the amount of time each horse spent near shade. She found that:

  • The temperature-heat index was lowest in the morning.
  • Horses spent the most time near shade in the afternoon and the least time in the morning.
  • Horses spent, on average, 72 minutes a day near the shade.
  • Horses’ activity levels were lower during peak heat and sun.

“While horses seek shade and decrease activity with increased temperature-heat indices and solar radiation, the overall quantity of time spent near shade was relatively small,” said Greene.

Her take-home: Don’t restrict horses to shelters. They do have effective ways to dissipate heat naturally (e.g., evaporation of sweat, convection through wind, radiating heat) and, when given a choice, appear to prefer to be out in the open.