Study On Metabolic Changes Of Florfenicol In Eggs

In recent years,the poultry and egg industry in China has a good prospect and rapid development,but the main producers of poultry and egg are still small farmers,scattered and small-scale breeding accounts for more than 85%of the total amount of breeding,extensive production methods,low ability to prevent and control diseases of laying hens,lack of knowledge of scientific drug use,etc.,leading to greater risks of quality and safety of poultry and egg products.The improper use of flufenicol is one of the important reasons for unqualified poultry egg products.Therefore,the excessive use of flufenicol has become a key risk point affecting the quality and safety of Chinese poultry eggs.To study the metabolic changes of flfenicol residue in eggs by feeding drugs to hens in the early stage of laying and laying stage,which has important guiding significance for quality and safety control.In this study,chickens in a breeding farm in Tai’an were fed 50 mg/kg·bw^-1flufenicol（FF）in the growing period and laying period,respectively,to study the residual metabolic changes of FF and its metabolite flufenicol（FFA）.Based on the study of the changes of residual metabolism,an ultra-high performance liquid chromatography-tandem mass spectrometry（UPLC-MS/MS）method for the detection of total FF was extended and established.Through acid hydrolysis,FF of the free and bound states was converted into FFA for detection.The results show that:1.Thirty laying hens were fed flufenicol powder at the dosage of 50 mg/kg·bw^-1 for 5days.High concentrations of FF and FFA residues could be detected in the egg whites on the first day of administration,and the residues increased slowly during administration,but rapidly decreased after withdrawal on the fifth day until the 11th day.Low concentrations of residues were detected in egg yolks on day 1 of administration and increased significantly to a maximum of 3308.2±32μg/kg at the end of treatment on day 5.Residues remained stable for a period after discontinuation of administration and declined rapidly on day 8 until no residues were detected on day 15 after discontinuation.2.Laying hens in four groups（B1-B4）at the growing stage were fed flufenicol powder at the dosage of 50 mg/kg·bw^-1 for five consecutive days on the 25th,20th,15th and 10th days before first laying,respectively.No FF and FFA were detected in the eggs of group B1,while FF and FFA were detected in the egg whites and yolks of groups B2 to B4,and the residues gradually increased.The maximum concentration of flufenicol was3189.9μg/kg（egg white）and 3214.3μg/kg（egg yolk）in the newly laid eggs of group B4,and then it began to decline until no drug residue was detected in egg white and yolk on the 17th and 21st days after administration,respectively.Therefore,In order to ensure the food safety of consumers,the growing laying hens should stop feeding FF at least on the21st day before the beginning of production.3.Ultrahigh performance liquid chromatography-tandem mass spectrometry（UPLC-MS/MS）was used to detect the total residue of FF in eggs.The samples were first hydrolyzed with acid to release the residue of the bound state,and all FF was converted into FFA.The hydrolyzed samples were washed with ethyl acetate to remove the interfering substances,extracted by ethyl acetate under alkaline conditions,purified by solid phase extraction,and quantified by UPLC-MS/MS.The method can be used for the determination of FF residue in eggs.The recoveries were 91.2%to 102.4%with RSDS≤10.88%.The limit of detection（LOD）and limit of quantitation（LOQ）were 0.5μg/kg and1.0μg/kg respectively.