Fate and Transport of Veterinary Antibiotics in the Midwestern Karst Region

The discovery and development of antibiotics has been considered by many to be the greatest advance in the history of medicine. Antibiotics are used extensively for both human medicine and animal agriculture, with agriculture accounting for between 40-80% of the total annual usage. The vast majority of agricultural antibiotics are used for growth promotion and prophylaxis. There is growing concern that antibiotics used in livestock production are contaminating surface and ground waters and contributing to the development and spread of antibiotic resistance in the environment. In this presentation, we will summarize the results of a three year field study conducted in Midwestern karst region quantifying antibiotic losses from leaching and runoff from land-application of manure. In addition, we will also summarize a field study conducted to quantify antibiotic degradation during manure composting. Antibiotics monitored in these studies included chlortetracycline, monensin, sulfamethazine, and tylosin. Our results indicate that antibiotic losses associated with land-application of manure were low. Less than 5% of the total amount of antibiotics applied with manure was exported to aquatic environments. To address the potential environmental risks associated with antibiotic use in agriculture, several composting intensities were evaluated. In general, antibiotic degradation ranged from approximately 50-99% of the initial levels. Collectively, the results from these studies suggest that small quantities of veterinary antibiotics may appear in aquatic environments or food supplies; however, manure management practices can be an effective option to mitigate these environmental risks.