The growth habits of certain grasses and legumes make them more favored by horses. Given free choice, grazing horses prefer to eat some types of grass, specifically Kentucky bluegrass and meadow fescue, rather than others such as reed canarygrass and perennial ryegrass. It was not known whether wearing a grazing muzzle would change equine preferences. To explore this question, a study was designed by researchers from the University of Minnesota to compare grazing behavior in muzzled horses turned out on plots sown with different forages.
Plots were planted with Kentucky bluegrass, perennial ryegrass, meadow fescue or reed canarygrass. Among these, bluegrass and fescue have prostrate growth habits (foliage stays close to the ground) while the others have upright growth habits.
Seven mature stock-type horses were accustomed to wearing grazing muzzles. Before allowing the horses to graze, a strip of forage was harvested from each plot, dried, and analyzed for dry matter. Horses were allowed to graze each plot for equal periods of time, first with and next without wearing grazing muzzles. After each grazing period, a second strip of forage was harvested, dried, and analyzed for dry matter. Plots were allowed to regrow before the next horse grazed. Horses always had free access to water. The research was carried out over a two-year period.
Results showed that in the first year, acceptance of the various forage species was not different when horses did or did not wear muzzles. In the second year, horses showed a preference for bluegrass over the other species. However, for all plots, about 30% less forage was consumed by muzzled horses than by horses that were not muzzled. Consumption of reed canarygrass in the first year was an exception, with about the same amount being eaten by horses with and without muzzles. This grass has an upright growth habit and its stiff stalks might have made it easier for muzzled horses to grasp. Also, because it is not a favorite forage, unmuzzled horses might have eaten less of it than of some other more favored grasses.
The researchers stated that results from this study showed about a 30% reduction in intake by muzzled horses, somewhat different from much greater intake reductions quoted by some other studies. What is clear is that use of grazing muzzles does significantly reduce forage intake for horses grazing several grass species. This management method is inexpensive and effective, and combined with other management practices, can help in limiting caloric intake for horses.