Nicarbazin contamination in feeds as a cause of residues in eggs

A survey was carried out to investigate the prevalence of nicarbazin residu es in eggs in Northern Ireland. Nicarbazin, in the form of 4,4'-dinitrocarb anilide (DNC), was detected in 39 of the 190 eggs analysed. An experiment w as designed to establish the relationship between nicarbazin-contaminated f eed and nicarbazin residues in eggs. The concentrations of both the DNC and 4,6-dimethyl-2-hydroxypyrimidine (DHP) components of the drug in eggs were proportional to feed levels. The maximum feed nicarbazin concentration of 12.1 mg/kg (8.6 mg/kg DNC and 3.5 mg/kg DHP) gave rise to mean maximum whol e egg concentrations of 631 mu g/kg DNC and 51.8 mu g/kg DHP. After withdra wal of the experimental diet, DNC was undetectable in eggs after 12 days an d DHP after 3 days. Feed contaminated with nicarbazin at concentrations gre ater than about 2 mg/kg gave rise to egg DNC residues at concentrations gre ater than the Differential Action Limit (DAL) set by the UK (100 mu g/kg). DNC was contained almost entirely in the yolk of the egg, whereas DHP was d istributed between albumen and yolk in a ratio of approximately 3:1.