Tuesday, November 6, 2007 - 10:45 AM
230-4
Occurrence and Fate of Antibiotics in Dairy Farming with Irrigated Forage Crops.
Thomas Harter, University of California, Davis, Department of Land, Air, and Water Resources, 125 Veihmeyer Hall, Davis, CA 95616-8628, Naoko Watanabe, Land, Air, and Water Resources, University of California, Davis, 125 Veihmeyer Hall, Davis, CA 95616-8628, and Brian Bergamaschi, California Water Science Center, United States Geological Survey, 6000 J Street, Placer Hall, Sacramento, CA 95819.
Intense animal husbandry is of growing concern as a potential contamination source of a variety of emerging contaminants including pathogens, naturally occurring and synthetic steroid hormones, and various pharmaceuticals, particularly antibiotics. For example, more than twenty million pounds of antibiotics are sold for use in animal husbandry with 95% going towards therapeutic use. Here, we focus on the application and potential environmental occurrence of pharmaceuticals and disinfectants on dairies. Recommended drug applications are available from national databases. Statistical data on actual usage, however, are not available. We complement national data with interviews and dairy visits for further evaluation of drug and chemical usage (not including pesticides used on crops and fertilizer). Aminoglycosides, tetracyclines, and coccidiostats make up much of the total mass of antibiotics used. On dairies using the ionophoric antibiotic monensin as feed additive, monensin makes up a large fraction of the total antibiotics use (by mass). Other chemicals of potential concern include disinfectants used to prevent mastitis, detergents used in the milking parlor, footbath reagents to prevent and treat lameness, and insecticides used to control flies and mites.