Efficacy of Wearing Grazing Muzzles for 10 Hours per Day on Controlling Bodyweight in Pastured Ponies

• Grazing muzzles for 10 hours followed by 13 hours of free grazing reduced weight gain in most ponies.
• However, one pony muzzled for 10 hours gained as much weight as ponies grazing unmuzzled for 23 hours.
• One pony developed an aversion to wearing a grazing muzzle for 10 hours.

Five, nonobese, adult ponies were pastured for 23 hours daily, either grazing freely (freegraze) or fitted with a grazing muzzle (muzzle) for 10 hours, from 8 AM to 6 PM. The trial was a crossover design, with 2, 3 week periods, in the summer of 2014. Ponies were acclimatized to grazing and drinking through their muzzles before the trial. Ponies were weighed on alternate days at 8 AM and 6 PM, and the daily average determined. Average daily changes in bodyweight (as a percentage of bodyweight) for four of the ponies when on treatment freegraze were 0.289 ± 0.109 being significantly greater than the -0.039 ± 0.098 when on treatment muzzle. Daily changes in percentage bodyweight for the fifth pony when undergoing treatment muzzle averaged 0.313 per day. Because of the rapid weight gain observed when this pony was muzzled, it was withdrawn from the trial and did not undergo treatment freegraze. There was an apparent learning phase during the first week of treatment muzzle, as changes in percentage bodyweight at the end of week 1 of this treatment averaged losses of −0.216, versus daily increases in percentage bodyweight of 0.073 and 0.029 for weeks 2 and 3, respectively. Corresponding values for treatment freegraze were 0.265, 0.283, and 0.322 for weeks 1, 2, and 3, suggesting a fairly constant mean daily weight change across the 3-week period. Thus, overall, use of grazing muzzles for 10 hours per day generally reduced the rate of weight gain in most, but not all animals.