Purpose: The study was aimed to evaluate tissue depletion of DC in broiler chicken when 200 mg/l of DC in drinking water were applied. The serum DC concentrations during and 24 h after medication were also studied.
Methods: Two hundred mg/l of DC in drinking water was applied to chickens for 5 consecutive days. Fresh water was supplied after daily dose reached 40 mg/kg body weight. Skin/fat, liver, kidney, heart, gizzard and muscle tissues were analyzed for DC level on the 3rd, 5th, and 7th day of withdraw. Blood samples were collected during and up to 24 h post medication.
Results: The skin/fat residue on the 7th day was 240 ± 45 ng/g (n = 3), and the 95% upper distribution limit (383 ng/g) exceeds its MRL (300 ng/g). All other tissues contained DC levels below their respective MRLs on the 3th day of withdraw. The serum DC level reached a steady state after the 3rd day of medication and the Cmax was 2.9 ± 0.2 μg/ml (n = 4). After medication ceased, the serum level dropped to 0.4 μg/ml in 24 h.
Significance: These data suggested a possible violation in skin/fat but not other tissues under common field medication practice. Longer WDT may be necessary if the recommended DC concentration is doubled in drinking water.