Incidence ofPenicillium roqueforti and roquefortine C in silages

Abstract

Wilted grass and whole-crop maize silages taken from farm silos in northern Germany were analysed for fermentation pattern, mould counts and composition of mycoflora as well as for roquefortine C. In general, increasing DM contents of visibly unmoulded silages resulted in decreasing amounts of volatile fatty acids and a greater portion of samples with a high number of mould propagules. The average mould count of these silages was found to be 1·4×104 cfu g−1, whereas visibly moulded samples contained about 1×108 cfu g−1. Penicillium roqueforti was the predominating fungal species in silages occasionally accompanied by species of the genera Aspergillus, Mucor, Monascus and/or Geotrichum. Penicillium roqueforti was detected in 89% of the visibly moulded and in 85% of the visibly unmoulded samples. Of 24 visibly moulded silages tested, 21 samples contained roquefortine C, a mycotoxin known to be produced by P roqueforti. The highest level of roquefortine C found was 36 mg kg−1 DM. Even 6 of 24 visibly unmoulded samples analysed for this mycotoxin were contaminated with roquefortine C but only in trace amounts. Roquefortine C is considered as a model compound for the biosynthesis of toxic fungal metabolites produced by P roqueforti in silages. The P roqueforti-count can be employed as a criterion to predict the contamination of silages with mycotoxins produced by this fungal species. © 1998 SCI.