The University of Arizona

Stocking Rate and Fuels Reduction Effects on Beef Cattle Diet Composition and Quality

Abe Clark, Tim DelCurto, Martin Vavra, Brian L. Dick

Abstract


An experiment was conducted to evaluate the influence of forest fuels reduction on 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 whole plots (3 ha) being fuel reduced or no treatment (control), and split plots (1 ha) within whole plots were grazed to three levels of forage utilization; (low) 3 heifers .  ha^-1, (moderate) 6 heifers . ha^-1, (high) 9 heifers . ha^-1, with a 48-h grazing duration. Grazing treatments were applied in August of 2005 and 2006. Cattle diet composition and masticate samples were collected during 20-min grazing bouts using six ruminally cannulated cows in each experimental unit. Relative preference indices indicated a strong preference for grass regardless of treatment and stocking rate. Grass consumption was lower in control pastures (P,0.05) and tended (P,0.095) to decrease with increased stocking rates. Shrub use was higher in control pastures displaying a quadratic effect (P,0.05) due to stocking, whereas shrub use increased with stocking rate across all treatments. Cattle grazing control pastures consumed diets higher in crude protein compared to cattle grazing treated pastures (P,0.05). In vitro dry matter digestibility values were lower (P,0.05) in control sites and tended (P¼0.10) to decrease with increased stocking rates. In both control and treated pastures, bites per minute and grams consumed per minute declined (P¼0.003) with increased stocking, indicating foraging efficiency of cattle decreases with increased stocking rates. Our data indicated cattle grazing late season grand fir habitat types have a strong preference for grasses 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.

Key Words: diet quality, diet selection, forage preference, fuels reduction


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