The Environmental Protection Agency defines an animal feeding operation (AFO) in the Code of Federal Regulations (CFR, Federal Register, V. 68 No. 1, page 7265) as a lot or facility (other than an aquatic animal production facility) where the following conditions are met: The Environmental Protection Agency defines an animal feeding operation (AFO) in the Code of Federal Regulations (CFR, Federal Register, V. 68 No. 1, page 7265) as a lot or facility (other than an aquatic animal production facility) where the following conditions are met: The definition of an AFO was developed by EPA as a regulatory definition to delineate confined feeding of beef cattle, dairy cattle, horses, swine, sheep, poultry, or other livestock from pasture-based systems (grazing systems were not meant to be regulated by EPA) for enforcement of the clean water act. The AFO classification is meant to apply to all sizes of operations and is the first step in defining an operation as a Concentrated Animal Feeding Operation. Concentrated Animal Feeding Operations are facilities that require federal National Pollutant Discharge Elimination System (NPDES) water quality permits, irrespective of size. While state regulations differ from state to state, changes in 2003 to the NPDES permit program forced most state programs to adopt the AFO and CAFO designations, and thus the regulatory definition of an AFO is common across the United States.