To investigate potential residues in tissues arising from naturally occurring low levels of chloramphenicol in plant material, feeding studies were conducted with chickens. A common chicken feed was prepared containing 0, 10, 50 and 200 μg kg-1 chloramphenicol and levels were confirmed by LC-MS/MS. Four separate groups of broiler chickens, eight animals in each group, were fed all their 35-day life with this contaminated feed. They were allowed ad libitum access to this feed and fresh water. After slaughtering the chickens, the residues in muscle and liver tissues were determined using GC/MS-NCI method. No residues were detected in tissues of animals from groups fed with feed containing 0, 10 or 50 µg kg-1. Low chloramphenicol residual concentrations were observed in a few of the muscle samples obtained from the group of chickens fed with feed containing chloramphenicol in added concentration 200 µg kg-1. No residues were detected in the remaining samples of this group. These results indicate that when residues of chloramphenicol are detected it is in all probability through illegal use.

ÚSKVBL Institute for State Control of Veterinary Biologicals and Medicines Brno Czech Republic

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