Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Animal Science


An interactive computer program was constructed and used to develop a deterministic linear programming model of a typical Midwestern farm feedlot production system. Data from a three-year series of cattle feeding trials served as the principal data base for the model which was utilized to evaluate the effects of diet (different silage:grain ratios), feeding management practices (restricted vs ad libitum feeding) and cattle marketing strategies (live weight vs carcass selling) on the relative profitability of feedlot beef cattle production;Two simulations were conducted with the model. Simulation A was run under no restrictions as to the amount of operating capital available for crop and livestock production or on feedlot capacity. Simulation B was conducted with operating capital limited to 200,000 and feedlot capacity fixed at 100 head to reflect production conditions likely to be encountered in the field. Results from simulation A indicated that rations which contained higher levels of corn grain were more profitable to feed than were higher silage rations with the 37:63 (silage:grain) ration fed to 2,492 steers recommended as the most profitable feeding program. Feeding management and cattle marketing practices had little impact on the overall profitability of the farm feedlot system. Results from simulation B showed that the higher silage feeding programs were more profitable to feed with the 93:7 ration fed to 208 steers selected as the optimal feeding program. Feeding management practices had little effect upon profitability while cattle marketing strategies had a major impact with the model showing a clear preference for selling cattle on a carcass basis. Sensitivity analyses indicated that the type of ration fed was of major importance in simulation A while feed production/acquisition strategies were of greater importance in simulation B;Interactions between the various crop and livestock production alternatives were observed. Although the variable costs of production for each of the feeding programs evaluated differed by only 9/head, income penalties to the entire farm feedlot operation ranged from 45 to 176/head fed in simulations A and B, respectively. Additionally, net farm income expressed as a percentage of the operating capital required for production was influenced by the scale of the cattle feeding enterprise (4.7% vs 18.7% for simulations A and B, respectively).



Digital Repository @ Iowa State University,

Copyright Owner

Robert William Brennan



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145 pages