Recently, the Food and Drug Administration announced that the number of antibiotic growth promoters that are available to be used by pigs will be reduced to reduce the risk of transferring antibiotic resistance from animals to humans. Only antibiotics that are not used in human medicine may be used as antibiotic growth promoters by animals in the future. To accommodate this change, it may be necessary to re-evaluate the use of antibiotic growth promoters in diets fed to pigs. It is possible that antibiotic growth promoters may be eliminated from swine diets if the complexity of the diets is increased. To test this hypothesis, an experiment was conducted to determine the effects of using an antibiotic growth promoter in diets formulated to vary in complexity.