DETECTING OXYTETRACYCLINE RESIDUES IN CHICKEN TISSUES USING THE DELVOTEST(R)-P SYSTEM

Oxytetracycline spiked chicken liver and kidney were tested for residu es using Delvotest P and the results compared to standard plate assay using Bacillus cereus as test organism. Delvotest P detected all repli cates at concentrations of greater than or equal to 0.62 mu g/g in liv er and kidney. Between 0.41-0.2 mu g/g, the responses were mixed (posi tive, doubtful, and negative); at 0.1 greater than or equal to concent ration, the responses were negative. The limit of detection of the pla te assay was 0.2 and 0.31 mu g/g for liver and kidney, respectively. R esidue analysis on tissues from chickens dosed twice daily (for 4 d) w ith 25 mg/kg oxytetracycline was carried out using the Delvotest P and the plate assay. Delvotest P responses were all positive for 1-4 h af ter treatment in kidney and 1 and 2 h in liver and serum. Muscle never achieved concentrations that were consistently positive. The plate as say detected drug from 0.5-6 h in serum, from 0.5-8 h in liver and kid ney, and at 4-6 h in muscle. Kidney tissue appeared to be the best for detecting oxytetracycline residues in chicken. The Delvotest P method was simpler to use and required less time; 3-4 h compared to about 18 h for the plate assay.