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An experiment was conducted to evaluate the influence of forest fuels reduction on the diet quality, botanical composition, relative preference, and foraging efficiency of beef cattle grazing at different stocking rates. A split plot factorial design was used, with the whole plots (3 ha) being fuel reduced or no treatment (control) and the split plots (1 ha) within grazed to three levels of forage utilization; (low) 3 heifers/ha, (mod) 6 heifers/ha, (high) 9 heifers/ha, with a 48 hour grazing duration. Grazing treatments were applied in August of 2005 and 2006. Cattle diet composition and masticate samples were collected during 20 minute grazing bouts using six ruminally cannulated cows in each experimental unit. Masticate samples were analyzed for crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), and invitro dry matter digestibility (IVDMD). Relative preference indices (RPI) indicate a strong preference for grass regardless of treatment and stocking rate. Grass consumption was lower in the control pastures (p<.05) and tended (P<.95) to decrease with increased stocking rates. Shrub use was higher in control pastures displaying a quadratic effect (p<.05) due to stocking where shrub use increased stocking rate across all treatments. Cattle grazing control pastures consumed diets higher in crude protein compared to cattle grazing treated pastures (p<.05). IVDMD values were significantly lower (p<.05) in control sites and tended (p=.10) to decrease with increased stocking rates. In both control and treated pastures bites per minute and grams consumed per minute declined (p=.003) with increased stocking, indicating foraging efficiency of cattle decreases with increased stocking rates. Our data indicated that cattle grazing late season grand fir habitat types have a strong preference for grass regardless of treatment or stocking rate. However, as stocking rate increased in both control and treated pastures grass consumption decreased, shrub consumption increased and foraging efficiency decreased. Fuels reduction did not increase late season shrub consumption, however it could lower late season CP availability. |
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