Evaluation of Pasture Systems and Grain Levels for Growing Beef Cattle with Prediction Equations for Estimating Animal Performance

A three-year grazing study evaluated native, native-interseeded range and a tame grass pasture production, quality and animal performance. Animal production and performance were evaluated with yearling steers fed corn daily at zero, 0.5 and 1.0 percent of body weight. Interseeding alfalfa into native rangelands enhanced sod-forming over bunch grasses and allowed alfalfa to become the dominant species. Alfalfa was not selectively graved in the interseeded range and in 1978 contributed 35 percent of the dry matter yield during the spring and summer. Forage quality declined with maturity; IVDMD and CP decreased while ADF, NDF, lignin and silica all increased with the grazing season. Alfalfa greatly increased forage quality in the interseeded range with tame pastures having the best quality season-long. Five methods were evaluated to estimate dry matter intake for grazing steers. Methods using forage quality along with animal weights and gains gave higher predictions than using body weight alone. Average daily gains of steers increased with increasing levels of grain supplementation; however, no differences were found between pasture systems. Interseeded and tame pastures increased gains per ha and carrying capacity by 60 and 54 percent, respectively, over the native range. Grain supplementation at 0.5 and 1.0 percent of body weight increased carrying capacity by 9 and 21 percent, respectively over the zero grain level. Native and interseeded range steers consistently suffered weight loss in the late fall grazing periods at zero and 0.5 percent grain levels, while the 1.0 percent grain level allowed animals to maintain body weights. Native range required 32 percent more acreage per animal unit than interseeded or tame pastures. Four equations to predict mean average daily gain were recommended on the basis of research or producer use. Coefficients of determination ranged from 48.8 to 52.6 percent and standard deviations from 0.281 to 0.291. The most practical equations require estimates of dry matter intake, IVDMD (or TDN) ADF, NDF, animal body weight and period of the grazing season