The purpose of this chapter is to familiarise the reader with the range of veterinary pharmaceuticals used in agriculture in the United States and to provide examples of the environmental occurrence of selected veterinary pharmaceuticals. A 1998 survey conducted by the Animal Health Institute (AHI) reported that there were 109 million cattle, 7.5 billion chickens, 92 million swine, and 292 million turkeys in the United States (AHI 2002). In comparison, a 2002 survey conducted by the National Agricultural Statistics Service (NASS) reported 104 million cattle, 8.6 billion chickens, 60 million swine, and 275 million turkeys in the United States (NASS 2002). To increase the efficiency of food production and maintain economic viability, animal agribusinesses began contracting with cooperative farmers, which lead to a proliferation of large animal-feeding operations (AFOs) over the last decade. Because of the close proximity of the large numbers of animals at these facilities and the potential for the rapid spread of disease, use of pharmaceuticals is important to maintain their operations.
