Abstract
Diets containing various levels from 0 to 4, 000ppm equivalent of oxytetracycline (OTC) were fed to meat-type male chicks and after 8 weeks of age dietary OTC was withdrawn. Chicks were sacrificed at 2, 4, 6 and 8 weeks of age during feeding OTC, and at 0, 3, 6 and 9 hours and 1-8 days after the withdrawal of OTC for sampling the blood, breast muscle, liver and bile. Content of OTC in the organs was determined microbiologically using Bacillus cereus var. mycoides ATCC 11778.
No residue was detected in the blood, breast muscle and lived of the chicks given OTC at the level of 20ppm.
Residue of OTC in the blood, breast muscle and liver on the dietary levels over 500ppm was in proportion to the dietary level of OTC. More OTC residue was found at 2 weeks of age than at older age.
Disappearance pattern from the liver and bile of the chicks after the withdrawal of 4, 000ppm of OTC can be described well by the following equation,
y=A1e-c1T+A2e-c2T
where, y is residue in the organ, T is days after the withdrawal of dietary OTC, A1 and A2 are constant, c1 and c2 are constants indicating the initial and later speed of disapperance. The constants, A1, A2, c1 and c2 were estimated from the data obtained. Application on two-compartment model to explain the disappeance pattern was discussed.
