Transference of dietary veterinary drugs into eggs.

Twelve veterinary drugs, bacitracin (BC), chloramphenicol (CAP), chlortetracycline (CTC), oxytetracycline (OTC), tylosin (TS), amprolium (APL), furazolidone (FZD), nicarbazine (NCZ), ormetoprium (OMP), sulfadimidine (SDD), sulfadimethoxine (SDM) and sulfamonomethoxine (SMM) were fed to laying hens for 14 days, each at a dietary concentration of 500 mg/kg. The concentrations of the drugs in the eggs from these birds were determined at 2-day intervals for 14 days after the start of feeding. The relationship between the concentrations of the drugs (mg/kg) in the eggs and the number of days after the start of feeding was analysed by regression and covariance analyses. The concentrations of the drugs in the eggs became constant after 4 days for OTC, TS, FZD and all the sulfonamides, and after 6 days for CAP, APL, NCZ and OMP. No BC or CTC was detected in the eggs. The transfer rates of the 10 drugs (excluding BC and CTC) from the feed to eggs varied from 0.005% for TS up to 1.540% for SDD.