ZERANOL IS FORMED FROM FUSARIUM SPP. TOXINS IN CATTLE IN-VIVO

Zeranol, a semi-synthetic oestrogenic growth promoter, was banned in t he EU in 1988. The ability of Member States to police the ban on zeran ol has been hampered by suggestions from New Zealand and from this lab oratory that zeranol may be formed by the in vivo metabolism of natura lly occurring Fusarium spp. toxins. The present study demonstrates tha t 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 nor detected following administration of bet a-zearalenol. These data suggest that hydrogenation of alpha-zearaleno l, probably in the rumen, is responsible for the appearance of zeranol . The present study shows that environmental contamination with Fusari um spp. toxins is widespread in Northern Ireland. Fusarium spp. toxins were present in 32% (n = 422) of all bovine bile samples tested for z eranol during 1995. Zeranol itself was confirmed in 6.6% (n = 28) of t he samples. However, the mean alpha-zearalenol and beta-zearalenol con centrations in the bile of zeranol-positive animals were 12 and 9 time s higher, respectively, than those in the zeranol-negative animals. Th e alpha-zearalenol concentration always exceeded the zeranol concentra tion by at least 5:1. This may, in the future, permit differentiation between zeranol abuse and natural contamination.