Horses Reveal Paddock Preferences

Where would horses prefer to laze on a hot summer’s day: directly in the sunlight, tucked beneath a shade tree, or under the sun but sprayed with water mist? What’s your guess? Researchers examined the preference of horses exposed to these three options by recording a variety of behavioral and physiologic measures.^*

Polish researchers used 12 mature horses in this study. A sand-covered experimental paddock that provided neither feed nor water served as the site. Mature trees with overhanging, though out of reach, limbs shaded nearly half of the paddock. In a corner of the paddock with no shade, an automatic mist curtain (250-cm or 8-ft square) that spritzed tap water (60° F or 16° C) was installed. Horses were completely acclimated to the paddock and the mist curtain prior to the study.

The study took place in July when the average air temperature in the shade was 90° F (32° C), though slight variation throughout the testing periods occurred based on wind speed and humidity. Horses were turned out in the paddock alone for 45 minutes, and they were allowed to move freely and choose areas to rest, either in the sun, in the shade, or at the mist curtain. All turnout sessions were video recorded. The horses were outfitted with a heart rate monitor during turnout to track heart rate and heart rate variability as measures of emotional arousal. Body temperature was recorded before and after turnout.

What did the researchers find? As a group, the horses showed no preference for one location in the paddock over another. Individual differences between horses, however, were far greater, with some horses showing a strong preference for a single location. While no horse showed evidence of overheating during these short periods in the paddock based on body temperatures, heart rate variability revealed that horses were most relaxed in sunny or misty areas.

Horses depend on sweating as their primary mechanism for thermoregulation. On hot and humid days, even horses lazing in paddocks can sweat. Not all sweat is noticeable, as some rises to the surface of the coat and evaporates before perceptible wetting of the coat occurs.

As they sweat, horses lose significant amounts of electrolytes, especially sodium, chloride, and potassium. These electrolytes should be replaced through the provision of a scientifically formulated electrolyte, especially when horses sweat daily or nearly so, as performance horses do. The effects of inadequate electrolyte supplementation in athletic horses have been documented and include a decrease in performance with reduced stamina.

^*Janczarek, I., A. Stachurska, I. Wilk, A. Wisniewska, M. Rozanska-Boczula, B. Kaczmarek, J. Luszczynski, and W. Kedzierski. 2021. Horse preferences for isolation, shade or mist curtain in the paddock under heat conditions: Cardiac and behavioural response analysis. Animals 11:993.