Hydrolysis of Selected Veterinary Antibiotics and Their Chemical Degradation in Anaerobic Swine Lagoons

Unmetabolized antibiotics excreted from swine are typically transported to an anaerobic lagoon at confined animal feeding operations (CAFOs). However, little research has focused on the fate of antibiotics in this setting. To help determine chemical degradation of selected antibiotics in lagoon systems, hydrolysis of selected sulfonamides, macrolides, tetracyclines and lincosamides was investigated in aqueous-phosphate buffered systems as a function of pH, temperature, and ionic strength and in swine manure collected from two CAFO lagoons in central Missouri. Lagoon manure was autoclaved to eliminate biological activity and then amended with one of the study antibiotics. Manure systems were maintained in an anaerobic environment for the duration of the two-month experiment at an ambient pH of 7.5 and 25 degrees C and were amended with one of four study antibiotics: oxytetracycline, tylosin, sulfathiazole, and lincomycin. In general, hydrolysis rates for oxytetracycline in the synthetic systems increased as pH deviated from pH 7 and as temperature increased. Tylosin underwent hydrolysis at pH 2 and 11 and the sulfonamides showed no significant hydrolysis under the study conditions. Lincomycin appears to hydrolyze slowly under the study conditions. Likewise, the manure study showed a similar trend for the study antibiotics. From the results in this study, it appears that hydrolysis may be a major removal mechanism for oxytetracycline in swine lagoons, while no significant removal has been observed for the other study antibiotics. Additional work is necessary to verify the chemical degradation of the study antibiotics by mechanisms unrelated to general hydrolysis.

Loftin, Keith, Adams, Craig, Meyer, Mike and Surampali, Rao, 2004, Hydrolysis of selected veterinary antibiotics and their chemical degradation in anaerobic swine lagoons [abst.]: The Ninth Symposium on the Chemistry & Fate of Modern Pesticides, Vail, Colorado, August 16-19, 2004.