Scientists have been testing the popular rugs.
Fly rugs are effective at reducing fly nuisance – but at a cost, researchers have discovered.
Five horses were monitored for heart rate, body temperature and cortisol levels (to indicate stress). Each horse alternated between a wearing fly rug or not over a ten-week period.
In the study, fly rugs significantly reduced fly avoidance behaviours such as head tossing and tail swishing. However, baseline cortisol levels were lowest without the rugs.
Heart rate was significantly higher when fly sheets were on. Body temperature varied with and without the fly rugs.
Fly rugs effectively reduce insect avoidance behaviours, said the researchers. But they are associated with increased heart rate and inconsistent effects on body temperature, suggesting a potential thermal or physiologic [normal body function] cost.
Fly rugs may improve horse comfort during insect season, but heat load and physiologic stress should be monitored, they recommend.
The study by Meggan Graves, Xiaocun Sun and Kellie Fecteau is published in the Equine Veterinary Journal.
