Occurrence of aflatoxin B1 in dairy cow feed over 10 years in Portugal (1995-2004).

In Portugal, there is rather little information about the natural occurrence of aflatoxin in feedstuffs. The aim of this work was to report the results of screening the natural incidence of aflatoxin B1 (AFB1) in samples of cattle feed collected from seven dairy cow's farms from Portugal distributed in several locations of the country. One thousand and one samples were taken from 1995 to 2004. High performance liquid chromatography (HPLC) was used for separation, identification and quantification of the compound. Detection limit was 1 microg/kg. Aflatoxin B1 was detected in 374 (37.4%) of the samples. The incidence and mean content of AFB1 was generally low. Levels of aflatoxin B1 above the maximum limit established in Portugal (5 microg/kg) for dairy cattle feed samples were observed in 62 samples (6.2%) with levels ranging from 5.1 to 74 microg/kg. Out of those 62 samples, 3.7% had levels between 5.1 to 10 (mean 7.8); 1.8% had a contamination level of 10.1 to 20 (mean 12.0), and 0.7% exceeded 20.1 microg/kg (mean 50.4). On the last two years (2003-04) none of the samples exceeded the maximum permissible level of the toxin.