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A model of kleingrass (Panicum coloratum L.) growth and utilization by steers is presented. The model included stochastic inputs of climatological characteristics, water retention at different soil depths, rainfall runoff, potential evapotranspiration, forage growth, forage intake and steer performance. The model was used in a 2 x 3 x 4 factorial experiment where the factors were energy systems (ARC, 1965 versus NRC, 1976), stocking rates (2·47 head per hectare, 4·32 head per hectare and 6·18 head per hectare), and four management options. Individual steer weights by months were not significantly affected by the use of either energy system. Steer weights at the end of the grazing season were affected (F = 0·06) by energy system, the NRC system predicting 7·2 kg per head more liveweight gain than the ARC system. The light stocking rate had greater (P = 0·01-0·13) daily gains over months than the heavier stocking rates. The heavy stocking rate resulted, however, in greater (P < 0·05) production per hectare per year than the lighter stocking rates. Season-long production per hectare favored (P < 0·1) management options that removed steers immediately after forage was consumed rather than anticipating rainfall and new forage growth. The light stocking rate had the least mean seasonal production per hectare (P < 0.·05) but also had the least year-to-year variability. The heavy stocking rater yielded the greater (P < 0·05) mean seasonal production per hectare but the year-to-year variation was much greater. It was emphasized that the use of such probabilities of production could aid the grazier in making stocking rate and related decisions.