The Residues and Elimination of Enrofloxacin and Ciprofloxacin in Loach Misgurnus anguillicaudatus

Abstract:

In recent years, with the rigorous limits on drug residues in the loach Misgurnus anguillicaudatus from importing countries, the M. anguillicaudatus exporting enterprises and the export inspections are facing enormous challenges in drug use and control. The current study investigated the residues and elimination of enrofloxacin (ENR) and ciprofloxacin (CIP) in M. anguillicaudatus to provide a reasonable dosing plan and withdrawal period for the aquaculture industry. The loach M. anguillicaudatus purchased from an aquaculture farm were fed 7 days to adapt the experimental water quality and then divided into three groups at different temperatures, and fed with enrofloxacin or ciprofloxacin at a dosage of 20 mg/kg per day for 7 consecutive days. Samples were collected at various time points to measure the contents of ENR and CIP by the high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The results showed that both the elimination of ENR and CIP were complied with the first-order kinetics, and the water temperature significantly affected the elimination rate of both drugs. At 25℃, 20℃ and 15℃, it took 25, 32 and 50 days, respectively, for the enrofloxacin compound metabolized to less than 10.0 μg/kg in the body of M. anguillicaudatus. It took 27, 31 and 33 days for ciprofloxacin to metabolize to less than 10.0 μg/kg. Based on the South Korea limits of no more than 10 μg/kg for quinolones in M. anguillicaudatus, a withdrawal period of 32 days is recommended for the M. anguillicaudatus exporters by considering the actual culturing environments in Xuzhou and nearby area.