The effects of light on degradation of chloroteracycline （CTC） and oxytetmcyline（OTC） in chicken feces was studied, and the degradation velocity of CTC and OTC was determined by HPLC. The chicken feces were randomly assigned into two groups. One was in photophobic condition and the other was exposed to light. Samples were respectively collected from the two groups on day 0, 0.5, 1, 2, 3, 5, 7, 9, 12, 15 and analyzed by HPLC. In photophobic condition, the degradation velocity of three levels of OTC and CTC in chicken feces were 5.67%, 6.05%, 7.61% and 5.93%, 6.20%, 7.36% respectively within 15 days, while, in natural light, they were 87.60%, 95.66%, 97.81% and 89.53%, 95.98%, 98.62% respectively. Degradation velocity of CTC and OTC in chicken feces were similar, which consisted with the first order kinetic equation Ct=C0e^-kt. The half-lives of CTC and OTC in chicken feces were （3.24～1.02）d and （4.1 1±1.17）d respectively in natural light. The results indicated CTC and OTC had photolytic characteristics, and the photolysis speed of CTC was higher than that of OTC in chicken feces.
Journal of Agro-Environment Science( J. Agro-Environ. Sci.)