The objective of this study was to screen the occurrence of 50 antibiotics in a typical swine farm in southern China, which includes animal feeds, waste collection and treatment systems (lagoons and anaerobic digesters), and receiving environments (vegetable fields, streams, and private wells). Nine antibiotics were found in the feeds for different stages of the development of pigs in the swine farm, at concentrations ranging from 2.37 AE 0.16 ng g À1 (sulfamethazine) to 61 500 AE 11 900 ng g À1 (bacitracin). 11, 17 and 15 target compounds were detected in feces, flush water, and suspended particles in the swine farm, respectively. Based on the survey of feeds and animal waste from the farm, chlortetracycline, tetracycline, bacitracin and florfenicol in the feces, flush water and suspended particles mainly originated from the feeds, while most sulfonamides, including doxycycline, oxytetracycline, fluoroquinolones, macrolides and trimethoprim, were mainly from injection and other oral routes. The daily excretion masses of antibiotics per pig calculated based on animal waste had the following order: sows (48.3 mg per day per pig), piglets (18.9 mg per day per pig), growing pigs (7.01 mg per day per pig) and finishing pigs (1.47 mg per day per pig), indicating that the usage of antibiotics (type and dosage) and excretion masses are related to the growth stage of pigs. Chlortetracycline and bacitracin are the main contributors to the total excretion mass of antibiotics from pigs at different stages of development in the farm. The waste treatment system (lagoons and anaerobic digesters) was found to be ineffective in the elimination of antibiotics. The detection of some antibiotics in the surrounding environments of the farm (the well water, stream water and vegetable field soil) was a reflection of pollution from the swine farm.
Environmental impactAntibiotics are commonly used in both human and animal therapy. Particularly in animal therapy the usages span from therapeutic, prophylactic and subtherapeutic. The extensive use of antibiotics in livestock industry has become an increasing concern due to the potential risks posed by their residues to the environment and human health. So far, previous studies on antibiotic residues in animal farms have been limited and most of them are focused on selected groups of antibiotics such as tetracyclines and sulfonamides. This study screened for the rst time the occurrence and fate of 11 classes of antibiotics (in total 50 compounds selected based on their usage in China) in a typical swine farm in China, and evaluated the fate of the detected antibiotics from administration to excretion, and from waste collection and treatment systems (lagoons and anaerobic digesters) to the receiving environments (private wells, streams and vegetable elds). Feeds and animal waste (ush water and fecal samples) from different breeding units of the farm were collected to investigate the usage patterns of antibiotics (type, dosage, administration route) in the swine farm, and to estimate dail...