Halofuginone contamination in feeds as a cause of residues in eggs Original Research Article

An experiment was designed to establish the relationship between halofuginone (HFG) contaminated feed and HFG residues in eggs. Five groups of six-layer hens each were fed with HFG contaminated diets at concentrations ranging between 1 and 10% of the therapeutic dose for broilers (3 mg kg−1) for 14 days. The group fed on the highest dose was then fed with a HFG-free diet for a further 14 days. Eggs were collected, homogenised, extracted and analysed using a method employing liquid chromatography (LC) coupled to electrospray (ES)–tandem mass spectrometry (MS–MS). In general, the HFG concentration was much lower than those seen in similar studies on nicarbazin. However, comparison of the HFG concentrations measured in eggs and the maximum residue limit (MRL) for HFG in bovine muscle suggested that feed contamination could give rise to potentially significant HFG residues in eggs. Depletion of HFG from eggs, following the feeding of an HFG-free diet was 2.6 days, somewhat slower than the corresponding values for lasalocid and nicarbazin (1.1 and 1.6 days, respectively).