Occurrence and assessment of veterinary antibiotics in swine manures: A case study in East China

We investigated the occurrence of 14 selected antibiotics including five therapeutic classes of tetracyclines, sulfonamides, macrolides, fluoroquinolones and chloramphenicols in manures collected from four swine farms of different sizes in eastern China. Tetracyclines (tetracycline, oxytetracycline, chlortetracycline, and doxycycline) and sulfadiazine were the most prominent contaminants in the manure samples, with maximum concentrations reaching 98.2 × 103, 354.0 × 103, 139.4 × 103, 37.2× 103, and 7.1× 103 μg/kg, respectively. The occurrence of these compounds was dependent on breeding scale, animal type, and breeding season. Manure storage and vermiculture were not able to effectively deplete the heavier contaminants (tetracyclines and sulfadiazine), resulting in high levels of these chemicals remaining in manures. Therefore, the occurrence of these antibiotics in agricultural soils (0.1–205.1 μg/kg) collected from four types of agricultural land (pear orchard, tea plantation, bamboo forest, and paddy field) near the studied farms, was a reflection of manure application. However, the extremely high concentrations of antibiotics in manures were unlikely from feed consumption, but from other direct forms of medicine application.