In vitro metabolism of fumonisin B1 by ruminal microflora

Fumonisin B1 (FB1) is a mycotoxin produced by Fusarium moniliforme and F. p roliferatum. Little is known of its metabolic fate after oral ingestion in ruminants, but these animals are reported to be tolerant towards FB1. The m etabolism of this mycotoxin was evaluated following incubation (1 mu g/ml) in ruminal fluid for up to 72 h, in the presence or absence of alfalfa as a substrate for microbial growth, using a model rumen (sealed flask, anaerob ic conditions, exclusion of light, gentle agitation, 39 degrees C). The dec rease in FB1 concentration and the production of short-chain fatty acids we re determined. FB1 had no effect on SCFA production. After 72 h incubation, FB1 depletion was 12% and 18% in samples with and without alfalfa, respect ively. No hydrolysed metabolites (aminopolyols or aminopentol) were detecte d. These results indicate that FB1 is poorly metabolized in the rumen and s uggest that such metabolism is not the cause of the tolerance to this toxin displayed by ruminants.