Oxytetracycline transfer into chicken egg yolk or albumen

This study was conducted to determine whether the approved doses of oxytetracycline (OTC) for breeder hens and meat-type poultry would produce drug residue transfer into egg components when fed to laying hens. Twenty hens were assigned to equal groups (n = 10) and fed either 50 or 200 g/ton OTC for 5 d. Oxytetracycline concentrations in egg components were determined daily during a 2-d pretreatment control period, the 5-d dosing period, and following drug withdrawal. The stability and drug content of the medicated feed were determined the day dosing was started and the day of withdrawal. Residues of OTC were not detectable during the predosing, dosing, or withdrawal period in egg yolks. Oxytetracycline residues were detectable, however, in egg albumen during the 5th d of treatment and the 1st d of medicated feed withdrawal. These concentrations were close to the limit of the assay's sensitivity (117 ppb). These data indicate that illegal or unintentional dosing of laying hens with feed medicated at the doses allowed for breeder hens or meat-type poultry should not produce consistently detectable levels of residues of OTC in eggs.