Isolation and metabolite production by Penicillium roqueforti, P. paneum and P. crustosum isolated in Canada.

Penicillium roqueforti, P. crustosum and P. paneum grow on ensiled grain and recycled feed unless properly treated. The former two species occur also on cut lumber in Canada. These are known to produce a number of secondary metabolites including roquefortine. In cooler dairy production areas, including Scandinavia and North America, cattle toxicosis has been associated with silage contaminated by these fungi. We collected strains associated with cow or cattle toxicoses. The principal metabolites were determined making use of a new extraction method and analysis combining HPLC, LC/MS/MS, and LC/NMR. Penicillium roqueforti and P. crustosum required amino acid nitrogen for metabolite formation and their toxins were formed under conditions of low oxygen (20-30% saturation). Production of roquefortine C occurred on depletion of the available nitrogen and penitrem A on depletion of carbon source. Yield was reduced by excess carbon. Medium osmotic tension (aw) affected metabolite production by the two species differently. Penicillium paneum was associated with ill-thrift of dairy cows and P. roqueforti was associated with more serious symptoms. Our data suggest a physiological basis for the common occurrence of roquefortine C in silage without serious consequences and the alternative, the presence of roquefortine C and toxicoses. The strain isolated from lumber was the best producer of the toxins studied. This is the first report of the toxigenic potential of P. roqueforti and P. paneum from Canada.