Farmers use antibiotics to treat, prevent, and control animal diseases and increase the productivity of animals and operations. However, there is concern that routine antibiotic use in livestock will contribute to antimicrobial-resistant pathogens, with repercussions for human and animal health. Given these concerns, pressure to limit antibiotic uses for purposes other than disease treatment is mounting. Changes in use will lead to a series of adjustments in animal agriculture as producers change production practices, with potential repercussions for prices and volumes in livestock markets. This report addresses the following questions: How widely are antibiotics used in the livestock industries? How could the current structure of the livestock industry influence the effects of restrictions on certain uses of antibiotics? How might the restriction of antibiotics affect production and costs at the animal and farm levels? How might those impacts affect production and prices in markets?