Mycotoxin contamination and fungal populations in silages for dairy cows in Spain
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Ensiling is a practice commonly employed worldwide to preserve different kinds of crops for long periods of storage with similar nutritional values to the fresh materials. Since silages are one of the major components of the ruminant diet, these materials represent a potential source of mycotoxins as
a consequence of the growth of filamentous fungi. The aim of this study was to analyse the presence of aflatoxins and Fusarium mycotoxins in different types of silages (maize, grass, alfalfa, sugar beet pulp, immature corn and ryegrass) collected in dairy farms located in four Spanish regions. Fungal populations, lactic acid bacteria, pH and water activity of the samples were also evaluated. Penicillium (4-26%), Geotrichum (2-21%) and Monascus (0.34-3%) were the main fungal genera identified in the microbiological survey. As for mycotoxins analysis, aflatoxins were found in 10% of the samples, being detected in samples of maize, alfalfa and immature corn silage. Fusarium mycotoxins were found in 40% of the analysed samples, and fumonisins (FBs) were the most commonly detected. These toxins were found in samples of maize, grass, alfalfa, sugar beet pulp and immature corn silage. Among the different types of silages studied, maize silage samples were the most heavily contaminated. Out of 44 analysed samples, 30 were contaminated by at least one mycotoxin: 41% were positive for the presence of FBs, 14% for deoxynivalenol, 23% for 15-acetyldeoxynivalenol and 16% for zearalenone. The levels of mycotoxins detected in the samples did not exceed the guidance values recommended by the EU. The lack of relationship between Fusarium counts in the microbiological study and the mycotoxin analysis pointed that these mycotoxins were probably synthetized before or immediately after ensiling. Mould growth and mycotoxin contamination in silages and crops, which are subjected to ensiling, should be regularly monitored in order to minimize the chronic exposure of dairy cows to mycotoxins through the intake of contaminated feed.