Transfer of flubendazole and tylosin at cross contamination levels in the feed to egg matrices and distribution between egg yolk and egg white.

Chemical residues may be present in eggs from laying hens' exposure to drugs or contaminants. These residues may pose risks to human health. In this study, laying hens received experimental feed containing flubendazole or tylosin at cross contamination levels of 2.5, 5, and 10% of the therapeutic dose. Eggs were collected daily and analysis of the whole egg, egg white, and egg yolk was performed using liquid chromatography tandem mass spectrometry. Highest concentrations of the parent molecule flubendazole, as well as the hydrolyzed and the reduced metabolite, were detected in egg yolk. Residue concentrations of the parent molecule were higher compared with those of the metabolites in all egg matrices. No tylosin residue concentrations were detected above the limit of quantification for all concentration groups and in all egg matrices. Neither molecule exceeded the set maximum residue limits.