Zeranol is formed fromFusarium spp.toxins in cattlein vivo

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 α‐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 β‐zearalenol. These data suggest that hydrogenation of a‐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 α‐zearalenol and β‐zearalenol concentrations in the bile of zeranol‐positive animals were 12 and 9 times higher, respectively, than those in the zeranol‐negative animals. The α‐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.