| The breeds of broilers raised in China mainly include white-feathered broilers,hybrid broilers and yellow-feathered broilers.In recent years,the quantity and consumption of broilers have been increasing in China,and veterinary drug residues in broiler products have become a public health problem.Enrofloxacin is a cheap and effective veterinary drug,which is commonly used for the prevention and treatment of intestinal and respiratory tract infections caused by pathogenic bacteria in broiler breeding.The Ministry of Agriculture and Rural Affairs of China formulated the withdrawal period for different forms of enrofloxacin,and stipulated the maximum residue limit（MRL）for enrofloxacin residue markers（the sum of enrofloxacin and ciprofloxacin）in broiler tissues.The supervision and management department found that enrofloxacin residue in poultry products is not optimistic,and the problem of enrofloxacin residue exceed the standard is particularly serious in yellow-feathered broiler products.Relevant studies show that the current withdrawal period is not entirely applicable to yellow-feathered broilers.This study investigated the rule of enrofloxacin residue elimination in different breeds of broilers,providing data support for formulating accurate withdrawal period of different breeds.In this study,enrofloxacin and its metabolite ciprofloxacin residues in broilers were detected by high performance liquid chromatography-tandem mass spectrometry.1%acetonitrile was used as extraction reagent,0.1% formic acid water and methanol were used as mobile phase.Enrofloxacin and ciprofloxacin were added to blank tissue samples at low,medium and high concentrations.The results showed that the recovery rate of enrofloxacin was 81.24%～105.24%,RSD ≤ 4.66%,and the intra-batch and inter-batch coefficient of variation were less than 3.54% and 4.58%,respectively.The recovery rate of ciprofloxacin was 80.25%～105.54%,RSD ≤ 4.85%,and the intra-batch and inter-batch coefficient of variation were less than 4.21% and 5.26%,respectively.This method,with high accuracy, sensitivity and good reproducibility,can effectively extract drug residues in breast meat,liver,kidney and sebum.In addition to the pre-treatment steps,the detection of a single sample only takes 6.5 min.AA broilers,WOD168,Jinling Partridge,Xueshan chicken and Jinling black bone chicken were selected as the research objects,with 50 chickens in each breed.In the first three weeks of market age,chickens orally enrofloxacin at 10 mg/kg body weight for 5 days.Samples（chest muscle,liver,kidney and sebum）were collected on days 1,3,5,7,10 and 14 after drug withdrawal,and 6 samples were randomly selected from each variety at each time point.The drug residues in this sample were detected,the results showed that:（1）The elimination rate of drug residues in AA broilers was fast.On the first day after drug withdrawal,the drug residues in the tissues from high to low were kidney,liver,chest muscle and sebum,and the drug residues in sebum were lower than MRL;On the third day after drug withdrawal,drug residues in each tissue were lower than MRL;On the 10 th day after drug withdrawal,drug residues in all tissues were below the detection limit.（2）There was no significant difference in the elimination rate of drug residues between WOD168 and AA broilers tissues.（3）The rate of elimination of drug residues in the sebum of Jinling Partridge was slow,and the rate of elimination of drug residues in other tissues was fast.On the first day after drug withdrawal,the drug residues in the tissues from high to low were kidney,liver,sebum and chest muscle;On the third day after drug withdrawal,drug residues in chest muscle,liver and kidney were lower than MRL;On the 7th day after drug withdrawal,drug residues in sebum were lower than MRL;On the 14 th day after drug withdrawal,drug residues were detected in liver and sebum,and the drug residues in sebum were higher than those in liver.（4）The drug elimination rate in tissues of Xueshan chickens was slow,and the drug residue in sebum was higher and the elimination time was longer.On the first day after drug withdrawal,the drug residues in the tissues from high to low were kidney,sebum,liver and chest muscle;On the third day after drug withdrawal,drug residues in chest muscle,liver and kidney were lower than MRL;On the 7th day after drug withdrawal,drug residues in sebum were lower than MRL;On the 14 th day after drug withdrawal,drug residues were detected in all tissues except pectoral muscle.（5）The drug elimination rate in tissues of Jinling black bone chicken was slow,and the drug residues in sebum were high and the elimination time was the longest.On the first day after drug withdrawal,the drug residues in the tissues from high to low were sebum,kidney,liver and chest muscle;On day 7 after drug withdrawal,drug residues in liver and kidney were lower than MRL;On the 10th day after drug withdrawal,the drug residues in chest muscle were lower than MRL;On the 14th day after drug withdrawal,high concentration of drug residue was detected in all tissues,and the average drug residue concentration in sebum was up to 898.96μg/kg.According to the MRL of enrofloxacin residue markers in each tissue,the withdrawal period of breast muscle,liver,kidney and sebum of broilers of 5 breeds was calculated by WT1.4 based on 95%confidence interval.The results showed as follows:（1）The withdrawal periods of AA broilers tissues were 2.03 d,2.09 d,2.30d and 1.67 d,respectively.（2）The withdrawal periods of WOD168 tissues were 2.11 d,2.46d,2.64 d and 2.26 d,respectively.（3）The withdrawal periods of Jinling Partridge tissues were2.24 d,2.33 d,1.72 d and 8.16 d,respectively.（4）The withdrawal periods of Xueshan chicken tissues were 3.36 d,3.33 d,4.47 d and 10.29 d,respectively.（5）The withdrawal periods of Jinling black bone chicken tissues were 13.59 d,8.97 d,7.71 d and 39.74 d,respectively.In conclusion,（1）Drug residues in sebum of yellow-feathered broilers were observably higher than AA broilers and WOD168,and the elimination rate was observably slower than AA broilers and WOD168.The elimination rate of drug residues in tissues of Jinling black bone chicken was significantly slower than that of other broilers.（2）The withdrawal period of yellow-feathered broilers was significantly longer than AA broilers and WOD168.The withdrawal period of AA broilers,WOD168,Jinling Partridge,Xueshan chicken and Jinling black bone chicken were 2.30 d,2.64 d,8.16 d,10.29 d and 39.74 d,respectively. |
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