Distribution of molds and aflatoxins in dairy cattle feeds and raw milk

RESUMO

Ninety six feedstuffs given to dairy cattle from four milk producing areas of the São Paulo state, Brazil (Sorocaba, Cotia, Vale do Paraíba and Itupeva) were analyzed over a one-year period (june 1992 to august 1993) for the presence of contaminating fungi, toxigenic or not, and aflatoxins. In addition, the occurrence of aftatoxins M(1) and M(2), in raw milk from the studied dairy cows was evaluated in 144 milk samples. Fungal species were isolated on potato-dextrose agar identified by routine mycological techniques. Detection and quatification of aftatoxins were done by thin layer chromatography (TLC). The most freguent fungi recovered from feeds were Fusarium spp. (67.7 per center main isolate F. moniliforme), Aspergillus spp.(58.3 percentage; main isolate A. flavus) and Penicillium spp. (52.0 per center), followed by eight other fungi genera. The numbers of colony forming units (CFU/g) ranged from 3.5 x 10(3) to 1.1 x 10(6) (Fusarium spp.), 3.0 x 10(2) to 7.8 x 10(3) (aspergillus spp.) and 1 x 10(2) to 3.1x x 10(5) (Penicillium spp.). Twelve (46.1 per center ) of the 26 A. flavus isolates were group B aflatoxins producers and 3 of the A. parasiticus isolates were group B and G aftatoxins producers. The presence of aflatoxins B(1) and B(2) was observed in 14 (14.6 per center) of the feed samples analyzed at levels that ranged between 11.5 and 287 ug/kg (AFB(1)) and 19 and 40 ug/kg (AFB(2)). No carryover of mycotoxins to raw milk was observed. Nonetheless, despite these negative results under the experimental conditions used, the continuous evaluation pf levels of aflatoxin M(1) and M(2) in dairy products is always necessary since either favorable or unfavorable conditions for mycotoxin production may vary over different periods.