Mycotoxin Contaminating Maize and Grass Silages for Dairy Cattle Feeding: Current State and Challenges

Silages may represent 50-80 % of the total amount of diet for dairy cows during the winter. There is overwhelming evidence of contamination of maize and grass silages with fungi and associated trichothecenes, fumonisins, zearalenone, aflatoxins, ochratoxin A as well as some emerging mycotoxins (agroclavine, andrastin A, beauvericin, enniatins, festuclavine, fusaric acid, mevinolin, mycophenolic acid, roquefortins, T2/HT2 toxins). From year to year, multi contaminations often occurred with seasonal variations. The levels and incidences of deoxynivalenol and zearalenone raise concerns about animal health, as the levels overpassed the EC regulatory limits (2006/576/EC) for deoxynivalenol in 2006-samples from Poland and for zearalenone in 2000-2001 maize silages from Germany. AFB1 levels exceeded the maximum acceptable level in samples from Argentina. Atypical high occurring mycotoxins such as roquefortine C (up to 36,000 µg/kg), mevinolin (up to 65,400 µg/kg) and mycophenolic acid (up to 35,000 µg/kg) were not covered by routine analysis and legislation. These mycotoxins can diversely affect feed intake, productivity, reproductive performance and animal health but acute intoxications causing death are rare. Monitoring of mycotoxin in silages is extremely necessary. Both European and international legislation concerning the maximum tolerable limits must be strict and should also be adapted to include the interaction impacts between toxins. Further studies are needed to evaluate mycotoxin attributed to carry-over via meat, edible offal and lactation. Reliable multi-detection methods must be developed and should cover the normalized sampling plan to cover the heterogeneous distribution within the silo, the seasonal variation and the requirement to detect low levels of these contaminants. Conjugated (masked) forms of the mycotoxins and the long-term impacts to the exposure to low contamination deserved further assessment challenges.