Fungi and mycotoxins in fresh and ensiled maize and the affects of agronomic practices, weather conditions and silage characteristics on toxin contamination.

摘要

Maize silage, which constitutes a significant portion of the cattle diet, can become contaminated by mycotoxins produced by Aspergillus, Alternaria, Fusarium and Penicillium and the presence of these toxins has been associated with serious herd health problems (226). The objectives of this work were to study the mycoflora and mycotoxins in maize silage and investigate how agronomic practices, weather conditions and the process of ensiling affect the frequency and concentrations of several classes of mycotoxins. Silage was collected in Pennsylvania from 30-40 dairies during harvest and six months after storage in 2001 and 2002. Fusarium and Penicillium were the most commonly occurring toxigenic fungi although Aspergillus fumigatus, two Alternaria species and a novel species, Penicillium farinosum, were also present. The most commonly detected mycotoxins were those produced by Fusarium species deoxynivalenol (DON) and fumonisins. AAL-TA and AAL-TB, produced by Alternaria species, were also present and this is the first report of AAL-TB in maize silage. All four Penicillium toxins, cyclopiazonic acid, mycophenolic acid, patulin and roquefortine C were present in both fresh and ensiled maize, although it was previously believed that contamination by these toxins occurs almost exclusively during storage. The majority of silage samples were contaminated by multiple mycotoxins simultaneously and only 4 of 120 samples appeared to be free of detectable levels of contamination. The implications of theses findings are that multi-toxin contamination is likely to be wide-spread in silage and therefore, management strategies to prevent contamination must have a multi-facted approach rather than focusing on a single toxin.