Effect of time and weather on preference, frequency, and duration of shade use by horses.

This research investigated how healthy, mature horses used shade in a Bureau of Land Management (BLM) holding facility during hot, sunny weather. The results showed that horses used shade more often than expected by chance, particularly in the morning before the day’s peak temperature, and on the sunniest days, thus supporting the recommendation of the Federation of Animal Science Societies to provide shade for horses in hot weather.

Study Design and Setting

• The study was conducted at the Bureau of Land Management’s Palomino Valley Wild Horse and Burro Center in Reno, Nevada, over a period of approximately one and a half month from August 10 to October 1, 2014.
• The research utilized freestanding shade structures covered with shade cloth that blocked 98% of UV radiation which were constructed in two drylot pens.
• Two groups of four mares each were placed in the two pens. After a two-day acclimation period, their movements were recorded for five days before being moved to the opposite pen and observed for an additional five days. This process was repeated four times, resulting in a total of 32 horses being observed.

Data Collection and Analysis

• Data on the horses’ positions relative to the shade structures were collected through time-lapse cameras. Observations were made every 10 seconds from 9:30 AM to 5:00 PM.
• UV exposure was measured using dosimeters attached to the horses’ halters.
• Weather conditions, including ambient temperature, relative humidity, black globe temperature (a measure of the effect of solar radiation on an object), and solar radiation, were recorded using automated weather stations.

Key Findings

• Horses spent 10.9% more time in the shade than would be expected by chance, which gives a clear indication of their preference for shade during hot and sunny conditions.
• The average daily time spent in the shade per horse was about 108 minutes, broken up into an average of 17.1 intervals (or bouts), with each lasting an average of 6.3 minutes.
• Horses experienced a lower mean daily UV Index in the partially shaded drylots (1.52) compared to a control instrument in the sun (3.4).
• Horses made greater use of the shade on the sunniest days and at all hours of the day, with the most use occurring in the morning before the peak ambient temperature of the day.

Implications

• The findings suggest that shade use by horses is not random, but a conscious choice potentially associated with thermoregulatory behaviour.
• The study supports the recommendation made by the Federation of Animal Science Societies for the provision of shade for horses in hot and sunny weather conditions.
• The results of this study might be useful in the design and management of facilities for both domestic and captive wild horses, to improve their well-being in hot and sunny climates.