Abstract
After feeding a diet containing 8, 000ppm equivalent of chlortetracycline (CTC) for 4 weeks and withdrawing CTC from the diet, 5 chicks each of male meat-type chicks were sacrificed at 0, 0.125, 0.25, 0.375, 1, 2, 3, 4, 6 and 8 days after the withdrawal to obtain samples of the liver, bile and left tibia bone. Contents of CTC in the liver and bile were determined microbiologically, using Bacillus cereus var. mycoides ATCC 11778, and that in the bone spectrophotofluorometrically as described by BUYSKE et al.
Following Equation 4 was found suitable to describe the change in contents of CTC in the liver and bile of growing chicks,
y=A1e-3.942T+A2e-0.3531T……(4)
where, y is the content of CTC (ppm equivalent) and T is days after the withdrawal of dietary CTC, A1 and A2 are constants, which are 0.626 and 0.150 for the liver, respectively, and 7.67 and 2.33 for the bile, respectively. The disappearance pattern expressed by Equation 4 can be understood by two-compartment model shown in Fig. 1. The disappearance pattern of CTC from the tibia bone can be described by simple expotential curve of Equation 5,
y=43.82e-0.1281T……(5)
where, y is CTC content in the bone and T is as in Equation 4.
Difference in disappearance patterns from the liver, bile and egg white between CTC and OTC, and between growing chicks and laying hens is discussed. It is also discussed that the bone is suspected to be the storage site in two-compartment model and that part of CTC released from the bone is deposited again in the bone making recycling shunt in two-compartment model as shown in Fig. 3. Similarity of individual error variance of CTC and OTC contents after logarithm transformation is discussed.
