Residue depletion of florfenicol in eggs after oral administration to laying hens before laying
[Objective]To explore the withdrawal time of veterinary drugs in laying hens before laying,the accumulation and elimination of florfenicol in eggs of laying hens were examined after oral administration to laying hens before laying,and results can provide scientific support for laying hens breeding industry.[Method]378 healthy Lehmann Pink hens were orally administrated with florfenicol at a therapeutic dose,and the florfenicol and florfenicol amine residues in egg samples were determined by liquid chromatography-tandem mass spectrometry.The withdrawal time of florfenicol in laying hens before laying was determined by using the residue elimination model and software WT1.4.[Result]Results showed that the total residues of florfenicol and florfenicol amine in eggs were gradually increased during administration and reached the peak value(about 307.64 μg/kg)1 d after the drug was stopped,and then the drug residues were gradually decreased with the extension of drug withdrawal time.After 10-day withdrawal time,the total residues of florfenicol and its metabolites in eggs decreased to below the maximum residue limit(MRL)of 10 μg/kg and eventually belowed the detection limit on day 12 post-treatment.Based on the drug residue elimination model and software WT1.4,the withdrawal times of 9.70 d and 10.26 d for florfenicol were acquired.Verification results showed that the total concentrations of florfenicol and florfenicol amine residues in all egg samples belowed 10 μg/kg after 9-day withdrawal time.Based on above results,a 10-day safety interval was recommended for florfenoicol in laying hens before laying.The time interval from the first egg production to the theoretical laying time was 32 d during the experiment period.[Conclusion]Due to the irregularity of eggs production during early laying period,a 42-day withdrawal time is recommended for the florfenicol powder in laying hens before laying,to protect the health of egg consumers.
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