No abstract

Zeranol, a semi-synthetic oestrogenic growth promoter, was banned in the EU in 1988. The ability of Member States to police the ban on zeranol has been hampered by suggestions from New Zealand and from this laboratory that zeranol may be formed by the in vivo metabolism of naturally occurring Fusarium spp. toxins. The present study demonstrates that zeranol is formed from alpha-zearalenol and zearalenone in vivo and is detected in bovine bile following the oral administration of these compounds. However, it is not detected following administration of beta-zearalenol. These data suggest that hydrogenation of alpha-zearalenol, probably in the rumen, is responsible for the appearance of zeranol. The present study shows that environmental contamination with Fusarium spp. toxins is widespread in Northern Ireland. Fusarium spp. toxins were present in 32% (n = 422) of all bovine bile samples tested for zeranol during 1995. Zeranol itself was confirmed in 6.6% (n = 28) of the samples. However, the mean alpha-zearalenol and beta-zearalenol concentrations in the bile of zeranol-positive animals were 12 and 9 times higher, respectively, than those in the zeranol-negative animals. The alpha-zearalenol concentration always exceeded the zeranol concentration by at least 5:1. This may, in the future, permit differentiation between zeranol abuse and natural contamination.

No abstract

Lasalocid is a coccidiostat licensed for use in poultry, but not for use in egg-laying birds. Lasalocid residues were determined in an egg sample from each of 161 egg producers in Northern Ireland using liquid chromatography-electrospray ionization mass spectrometry, following reports from the Veterinary Medicines Directorate concerning the incidence of lasalocid residues in the United Kingdom. Approximately 66% of the eggs contained lasalocid residues at concentrations in excess of 0.3 ng/g. There was no apparent difference in the incidence of lasalocid residues between free range and battery eggs. Carry-over of lasalocid from medicated to unmedicated batches of both premix and feed, during milling processes, was identified as a possible cause of contamination. Subsequently, egg-laying birds were fed meal containing a range of lasalocid concentrations, similar to those found as a result of unintentional contamination at a feed mill (0.1-5.0 mg/kg). The concentrations of lasalocid, measured in their eggs, were similar to that found in the survey. Lasalocid persisted in eggs for 10 days after withdrawal of medicated feed and replacement with lasalocid-free feed.

A method is presented for the detection of the nitrofuran, furazolidone, in porcine tissue. Following methanol-buffer extraction of the tissue, liquid partitioning, and solid-phase clean-up, samples are analysed by using thermospray LC-MS monitoring the positive ion m/z 243 with filament-assisted ionization. The LOD is 1 microgram kg-1. The assay is used to investigate the depletion of furazolidone from tissue and sample stability post mortem. It is necessary to snap-freeze samples by immersion in liquid nitrogen immediately upon collection in order to improve the stability of residues in tissue.