Residue and Degradation of Oxytetracycline in Chicken Feces

In the first part of the study,the concentration of oxytetracycline in broiler chicken feces was examined after administration of different oral dosages of oxytetracycline by HPLC(high performance liquid chromatography).In the second part of the study,the degradability of oxytetracycline in sterilized chicken feces was tested under photophobic or illumination condition.In the third part of the study,the degradability of oxytetracycline in chicken feces was tested under different microbial conditions without illumination.The results were as follows.After feed medication in healthy broiler chicken,oxytetracycline was excreted in feces as the parent compound.When the dosage of feed medication was 100 mg·kg-1,200 mg·kg-1 and 400 mg·kg-1 feed,the concentration of oxytetracycline in chicken feces reached the peak at the 6th～8th hour after administration,with a peak concentration of 13.58 mg·kg-1,36.15 mg·kg-1 and 50.73 mg·kg-1 respectively.Oxytetracycline was undetectable at the 30th,62nd and 72nd hour after administration,respectively.The degradation process of oxytetracycline in chicken feces could be evaluated on the basis of the first order kinetics equation as Ct=C0 e-kt.The degradation of oxytetracycline in sterilized chicken feces was affected by illumination and the initial concentration of oxytetracycline.When the initial concentration of oxytetracycline was 10 mg·kg-1,20 mg·kg-1 and 40 mg·kg-1,the half-life of oxytetracycline in sterilized chicken feces was 55.5 d,123.8 d and 173.3 d respectively under photophobic condition and was 14.8 d,21.1 d and 27.5 d under illumination condition.Under photophobic condition,the degradability of oxytetracycline in chicken feces was affected by microbes and the initial concentration of oxytetracycline.When the initial concentration of oxytetracycline was 10 mg·kg-1,20 mg·kg-1 and 40 mg·kg-1,the half-life of oxytetracycline in chicken feces was 78.7 d,103.4 d and 157.5 d respectively with sterilized treatment,and was 40.5 d,50.6 d and 97.6 d respectively with unsterilized treatment,and was 14.5 d,33.6 d and 51.3 d respectively with added degrading bacteria treatment.Furthermore,in the second and third part of the study,the rate of oxytetracycline degradation increased when its initial concentration decreased under the same condition.