Summarized by Krishona Martinson, University of Minnesota
To prevent obesity in grazing horses, it is important to control pasture intake. The use of a grazing muzzle may help to achieve this goal. The objective of this study, conducted in England, was to determine the efficacy of grazing muzzles in controlling the bodyweight of grazing ponies.
Five, non-obese, adult ponies were pastured for 23 hours daily and either grazed freely (without a grazing muzzle) or were fitted with a grazing muzzle for 10 hours. Ponies were acclimatized to grazing and drinking through their muzzles before the trial. Ponies were weighed, and the daily average bodyweight was determined.
Average daily changes in percent bodyweight for four of the ponies when grazing without a muzzle was 0.3% compared to a slight loss in bodyweight (-0.04%) when fitted with a grazing muzzle. Daily change in percent bodyweight for the fifth pony while muzzled averaged 0.3% . Because of the rapid weight gain observe while muzzles, this pony was removed from the trial and was not allowed to graze without a muzzle.
There was an apparent learning phase during the first week of grazing with a muzzle. Percent change in bodyweight increased throughout the study as the ponies learned to graze with a muzzle. Pasture intakes for ponies with a grazing muzzle were fairly constant throughout the trial period.
Based on this research, it appears the use of a grazing muzzle for 10 hours per day generally reduced the rate of weight gain in most, but not all, ponies on pasture.