A study from Sweden suggests that horses head for run-in sheds to avoid insects rather than to seek respite from the sun.
For the study, researchers at the Swedish University of Agricultural Sciences monitored the behavior of eight horses for two weeks in July 2012. During the study period, each horse was turned out in one of four paddocks for one day at a time. In two of the paddocks there were two shelters: a three-sided shed with a roof, and an open structure that had a roof but no walls. Horses were free to choose either shelter and move between the two. The remaining two paddocks had no shelters.
“An open-sided shelter would give shade and allow a surrounding view but may be less effective in terms of insect protection,” says Elke Hartmann, PhD. “Therefore, we wanted to ask the horses themselves whether they ‘prefer’ an open or closed shelter.”
In addition to determining how long each horse stayed in each shelter, the researchers gathered data on weather conditions—including temperature, wind speed and relative humidity—every 10 minutes. They also did a daily count of insects collected in traps in the shelters and in a control trap set up in a paddock some distance from the horses.
Finally, rectal and skin temperatures were taken on all of the horses three times a day, and their behavior was documented at five-minute intervals from 9 a.m. to noon and from 1 p.m. to 4 p.m.
The data revealed that five of the seven horses who entered a shelter during the study period had a clear preference for the three-sided shelter over the open structure. The researchers noted a significant drop in insect-defensive behavior, such as skin shivers and ear flicking, when the horses were in the closed shelter, which suggests that the insects were less bothersome in that type of structure.
Temperatures during the study period were moderate, reaching only 77 degrees Fahrenheit. The researchers found no correlation between temperature and humidity and shelter use, but they did find that horses were less likely to utilize a shelter on windy days.
Noting that fewer insects were caught in the traps on those days, Hartmann says, “Increased wind speed often decreases insect activity, thus horses are more likely to be observed outside shelters.”
She adds that individual preferences could have also played a role in shelter utilization during the study. “There may be other reasons besides insects and weather conditions that can influence whether a horse goes into the shed,” she says. “And some horses may have simply liked to stay inside.”
Based on the results of this study, Hartmann recommends offering horses shelter, even when temperatures may be mild. “If horses are kept 24 hours on pasture during summer, I would recommend to offer shelter. At least horses would then have a choice.”
Reference: “Daytime shelter use of individually kept horses during Swedish summer,” Journal of Animal Science, February 2015
This article first appeared in EQUUS issue #455
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