Grazing Muzzles: Helpful or Stressful?
By Sarah Davis DVM
We have long known that grazing muzzles can aid in weight loss or maintenance by restricting pasture intake. What had not been studied until recently was how muzzling affects horses’ behaviors and stress levels. Since muzzles cover the lips and nose, horses cannot groom each other or communicate certain facial expressions. Researchers at the University of Maryland recently conducted a study to see how grazing muzzles affected horses’ stress levels and social behaviors.
The study looked at two groups of miniature horses that were turned out in a muzzle for varying amounts of time. The researchers tracked data including weight loss or gain, stress levels, steps walked, grooming/hierarchy behaviors, and heart rate. They found that while the minis muzzled 24/7 did not groom one another, they did not show any indicators of stress and ended up losing the most amount of weight. Despite not being able to bite or groom, the herd dynamics remained the same. Heart rates were low, cortisol (stress hormone) levels remained normal and they did not show any frustrated behaviors.
When comparing weight loss between the groups, the minis muzzled continuously while on pasture lost weight, while the other group that were only muzzled part-time ended up gaining weight. This could explain why only muzzling for part of the day can lead to unsuccessful diets. Horses may restrict their intake while wearing the muzzle, but when the muzzle is taken off they may eat more grass to make up for earlier.
Based on the results of this study, grazing muzzles are an easy way to restrict pasture intake without compromising the welfare of the horse. Horses continuously muzzled in the study lost weight, did not show any increase in stress behavior, and maintained herd hierarchy.
Remember to consult a veterinarian before starting a weight loss plan for your horse. We can help you to formulate a balanced diet of forage, grain and vitamins and minerals to help your horse lose weight at an appropriate rate.