Study On Residue Elimination Of Doxycycline Hydrochloride Soluble Powder In Pigs And Chickens

Doxycycline is a broad-spectrum tetracycline antibiotic produced by Streptomyces.It is mainly used for the prevention and treatment of bacterial diseases of livestock and poultry.It is widely used in veterinary clinic because of its remarkable effect.However,because doxycycline has toxic and side effects such as liver and kidney damage and allergic reaction,long-term consumption of livestock and poultry products with excessive doxycycline residue will lead to hypoglycemia,intracranial hypertension,organ lesions and chronic poisoning.Maximum residue limit（MRL）of doxycycline in edible animal tissues was established to ensure the safety of animal food.Doxycycline is often used in its hydrochloride.At present,the dosage forms of doxycycline hydrochloride approved for use in Veterinary clinic in China mainly include soluble powder,tablet,injection and capsule.Doxycycline hydrochloride soluble powder has the advantages of convenient use and simple operation,and is favored by the majority of farmers.Doxycycline hydrochloride soluble powder is currently included in the Chemical volume of Veterinary Drug Quality Standard（2017 edition）,and its withdrawal period is 28 days for pigs and 28 days for chickens.This standard lags behind and does not adapt to the current largescale breeding practice,so it is in urgent need of revision and is difficult to implement in farming.The purpose of this study was to investigate the withdrawal period of doxycycline hydrochloride soluble powder in clinical use of pigs and chickens,in order to provide data support for ensuring the quality of animal products and food safety of pigs and chickens.1.A HPLC method for determination of doxycycline residues in pig and chicken tissues was establishedThe samples were extracted by Na₂EDTA-Mcllvaine buffer solution for three times,purified by HLB solid phase extraction column,determined by HIGH performance liquid chromatography-Ultraviolet method,and quantified by external standard method.A method for the determination of doxycycline residues in pig and chicken tissues was established.The limits of detection and quantification of this method were 20 μg/kg and 40 μg/kg in pig muscle,liver,kidney and skin with fat tissue.The limits of detection were 25 μg/kg in chicken muscle tissue,50 μg/kg in chicken liver,kidney and skin with fat tissue,50 μg/kg in chicken muscle tissue,100 μg/kg in chicken liver,kidney and skin with fat tissue.In the concentration range of 0.05～5μg/m L,the linear relationship is good,and the correlation coefficient r is 0.999.The average recoveries of docicycline in blank tissues of pigs and chickens were 74.1% to101.3% with the relative standard deviations（RSDS）of 1.3% to 11.5% within the batch and 3.5% to 10.4% between the batches when docicycline was added in blank tissues of pigs and chickens in the concentration range of 40 to 1200 μg/kg.2.Study on the residue elimination rule of doxycycline hydrochloride soluble powder in pigsAccording to the Guidelines for Veterinary Drug Residue Elimination Test issued by the Ministry of Agriculture of the People’s Republic of China No.326,40 healthy three-yuan hybrid pigs weighing about 50 kg were selected,with half male and half female.Doxycycline.Mixed drink,every 1 L water,containing doxycycline hydrochloride soluble powder 50 mg,for 5 days.Five pigs were slaughtered at 0 d（8h）,1 d,3 d,5 d,7 d,10 d,15 d and 21 d after withdrawal of doxycycline.The residues of doxycycline in four tissues including back muscle,liver,kidney and skin with lipid were determined.According to the fitting of WT1.4 withdrawal period software,the withdrawal period of doxycline hydrochloride soluble powder was 1 d in pig muscle tissue,1.3 d in liver tissue,2.0 d in kidney tissue,and 0 d in skin with lipid tissue.Therefore,the recommended dose should be used.It is suggested that the withdrawal period of doxycycline hydrochloride soluble powder in pigs should be 3 days.3.Study on the rule of residual elimination of doxycycline hydrochloride soluble powder in chickensAccording to the Guidelines for Veterinary Drug Residue Elimination Test issued by the Ministry of Agriculture of the People’s Republic of China No.326,120 healthy white broilers（variety: Ross 308）weighing 1.5 kg were selected,half male and half female.Doxycycline.Mixed drink,every 1 L water,containing doxycycline hydrochloride soluble powder 300 mg,for 5 days.Fifteen chickens were randomly slaughtered at 0 d（4 h）,1 d,3 d,5d,7 d,10 d,15 d and 21 d after withdrawal of doxycycline.The residues of doxycycline in muscle,liver,kidney and skin with fat were determined.According to the fitting of WT1.4 withdrawal period software,the withdrawal period of doxycline hydrochloride soluble powder in chicken muscle tissue was 10.9 d,in liver tissue was 11.1 d,in kidney tissue was 11.4 d,and in skin with fat tissue was 4.5 d.Therefore,the recommended dosage should be used.It is suggested that the clinical withdrawal period of doxycycline hydrochloride soluble powder in chicken should be 12 days.