Food safety implication: certain antibiotics may rapidly contaminate egg albumen during the process of its formation.

1. Egg white formation occurs in 3 phases: synthesis and storage of albumen proteins prior to ovulation, secretion of proteins during passage of the ovum down the reproductive tract (preplumping) and addition of water (plumping phase). 2. This study was to determine if oxytetracycline would transfer into egg albumen during the latter 2 phases of albumen formation. 3. In 2 experiments 48 hens were injected with either 400 mg/kg oxytetracycline or physiological saline. Hens were dosed at 0.5 h (preplumping phase) or 5.5 h (plumping phase) after oviposition. 4. Five hours following injections, hens were euthanised and albumen was collected from the reproductive tract. 5. Oxytetracycline transferred into albumen during both phases of albumen formation. Concentrations (ppm) were greater in the preplump vs plump phase (3.2 vs 1.8 in experiment 1; or 2.8 vs 1.6 in experiment 2. However, when differences in albumen weights were accounted for, total microg transfer did not differ between the 2 phases. 6. Drugs may transfer into egg whites during the latter phases of formation prior to oviposition. Therefore, poultry producers or veterinary practitioners dosing laying hens must consider that egg whites contained in the 1st egg laid after dosing may contain drug residues.