Doxycycline and sulfadimethoxine transfer from cross-contaminated feed to chicken tissues.

During feed preparation at feed mills or during feed mixing in bins at farms, the accidental contamination of feed at trace levels by veterinary drug residues, commonly known as carry-over, can accidentally but frequently occur. To evaluate the concentrations of residual antimicrobials in poultry edible tissues, due to contaminated feed, sulfadimethoxine and doxycycline were administered for 10 days to chickens in poultry feed incurred at the contamination levels frequently found during national feed monitoring programmes (1-5 mg kg(-1)). Sulfadimethoxine and doxycycline residual concentrations detected in muscle (<LOD and 31 µg kg(-1), respectively), liver (13 and 56 µg kg(-1), respectively) and kidney (56 and 115 µg kg(-1), respectively) were compared with their maximum residue limits (MRLs) fixed by EC 470/2009 and EU 37/2010 Regulations for a preliminary risk evaluation.