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The Interaction of Grazing Muzzle Use and Grass Species on Forage Intake Of Horses
Excessive pasture intakes have been linked to the increased incidence of equine obesity and pasture associated laminitis. Previous research found that grazing muzzles reduced pasture intake by 83%. However, horses are selective grazers, and forage grasses have different growth morphologies. Both factors could impact the effectiveness of grazing muzzles; however, this has not been investigated. Therefore, the objective of this research was to determine the effectiveness of grazing muzzles at reducing forage intake when horses were allowed access to different grass species. The study was conducted in 2012 and 2013. Four horses were grazed in 2012, while three horses were grazed in 2013. Prior to grazing, horses were acclimated to wearing a grazing muzzle and grazing for 4 hours. Four species of perennial, cool-season grasses were grazed in 2012 including: Kentucky bluegrass (KB; prostrate growth habit, preferred by horses), meadow fescue (MF; upright, preferred), perennial ryegrass (PR; prostrate, less preferred), and reed canarygrass (RC; upright, less preferred). In 2013, only KB and RC were grazed due to winter kill of PR and MF. Horses were allowed to graze a small pasture (4.5 x 9.9m) seeded with one of the individual grass species for 4 hours each day for 4 consecutive days in June and August of 2012 and August and September of 2013. Horses grazed the same grass species for two consecutive days, one day with the muzzle and one day without. Prior to each grazing event, a 0.9 x 3.3 m strip was mechanically harvested from the pasture to determine available initial herbage mass. Post grazing, an adjacent 0.9 x 3.3 m strip was harvested to determine residual forage mass. The difference (on a dry matter basis) was used to estimate horse forage intake. Data were analyzed using the PROC MIXED procedure of SAS, with statistical significance set at P ≤ 0.05. The effectiveness of a grazing muzzle was not affected by forage species (P ≥ 0.05). Use of a grazing muzzle decreased the amount of forage consumed by an average of 30% across species and years (P <.0001). These results will aid horse owners and professionals in estimating forage intake and balancing rations of muzzled horses on pasture.
Keywords: grazing, intake, muzzle