Researchers Study Muzzled Horse Behavior

An owner’s No. 1 goal when outfitting their horse with a muzzle is usually related to weight management—either keeping them from gaining weight or helping them shed some pounds. While study results have shown that muzzles are, indeed, effective for weight control, they can also have other effects. For instance, they can alter horse behavior.

However, few studies have documented exactly how muzzling impacts behavior. So, Ashley Fowler, MS, and colleagues at the University of Kentucky, in Lexington, conducted a study to compare the behavior of 12 horses when they were muzzled and unmuzzled. She presented the results at the 2017 Equine Science Society Symposium, held May 30-June 2, in Minneapolis, Minnesota.

Fowler and colleagues observed the horses (turned out in groups of three for six hours) for one hour, two days per week, for five weeks. The researchers watched their unmuzzled behavior for the first week, then monitored their muzzled behavior for Weeks 2 through 5. The team tested closed-bottom muzzles that prevented feed ingestion, but allowed water consumption.

“We used total exclusion muzzles because some horses become really adept at grazing through muzzles that contain a hole,” Fowler explained, “so much so that they can continue to gain weight even while wearing a muzzle. For these horses, exclusion muzzles are a good option to still allow horses access to turnout, for exercise—which could encourage further weight loss—and socialization.”

The team found that:

  • When unmuzzled, horses foraged 52% of the time, stood 41% of the time, and walked 6% of the time; and
  • When muzzled, horses stood 81% of the time and walked 16% of the time.

Although horses spent more time walking around their paddocks when muzzled, they also more than doubled the time they spent standing, Fowler said. She cautioned that “movement during grazing bouts in unmuzzled horses was not recorded, so the difference in total movement is unknown.” She said additional studies using pedometers could help shed light on the total movement and energy expenditure between muzzled and unmuzzled horses.

Additionally, the team observed that muzzled horses rubbed their muzzles and pawed more frequently during the first two weeks of muzzling compared to the last two weeks. Fowler said this suggests it took the horses about two weeks to acclimate to wearing the muzzles. Unmuzzled horses did not have muzzles to rub, she added, and pawed very infrequently.

She also noted that the team observed altered drinking behavior when horses wore muzzles.

“During the first week of muzzling, horses increased the number of times they visited the water trough,” she said. “While we didn’t measure water consumption, we suspect that instead of drinking, horses were playing in the water or attempting to remove their muzzles in the trough because we didn’t see an increase in the frequency of urination with the increase in visits to the water trough.”

Finally, Fowler said the team observed more social interactions when horses were muzzled than when they were unmuzzled.

“Because horses aren’t able to graze anymore, they must fill their day up with other behaviors, and increasing social interactions is one way to do so,” she said. “So even though horses do spend more time standing around outside when they are muzzled, at least they are able to have social interaction.”

Fowler cautioned that “these horses wore total exclusion muzzles; muzzles that allow reduced foraging might have different effects on behavior.”

Muzzle use remains an effective equine weight-management strategy that many owners employ daily.

“Make sure that muzzles are well-fitting and sufficiently padded,” Fowler advised. “Ill-fitting muzzles can cause sores (especially when the horses are trying to rub their grazing muzzles off) and could also make it easier for the horse to remove the grazing muzzle.”

She also encouraged owners to wait out the horse’s acclimatization period, even if he develops new behaviors.

“Horses appear to adjust to muzzling within two to three weeks,” she said. “If an owner sees a horse rubbing their muzzle or pawing a lot during the first couple weeks of daily muzzling, they shouldn’t give up. It is likely that the horse will reduce these behaviors in a couple weeks.”