Mycobiota and naturally-occurring ochratoxin A in dairy cattle feed from Rio de Janeiro State, Brazil

The worldwide contamination of foods and feeds with toxigenic fungi and its mycotoxins is a significant problem of great agro-economic importance. The impact of mycotoxins includes toxic effects on humans and animals with increased health care, veterinary care costs and a reduced livestock production. The aims of the present work were: (1) to determine the mycobiota present in raw materials and finished cow's feed as well as to determine the ability of several Aspergillus and Penicillium isolated species to produce ochratoxin A, and (2) to evaluate the ochratoxin A production on these substrates. Samples (133) (corn, brewer's grain, barley rootlets, cotton flour, pelletised citric pulp and finished cow's feed) were collected. They were examined for total moulds, Aspergillus and Penicillium spp. occurrence and relative densities. The capacity to produce ochratoxin A by selected Aspergillus and Penicillium spp. was determined by HPLC. Total mould counts were generally higher than 1 x 10⁴ cfu/g. Aspergillus and Penicillium species were isolated in the highest numbers. Aspergillus flavus, A. niger and A. ochraceus were the most prevalent species. A. niger (38.5%), A. carbonarius (71.4%), A. ochraceus (32.7%), and P. verrucosum (13.1%) were OTA producers at levels that ranged between 9 and 126 µg/kg. Finished cow's feed (25%), corn (31%), barley rootlet (21.6%) and brewer's grain (45%) samples were positive for OTA contamination. In this study, total counts were over the proposed limit to ensure hygienic quality. In general, samples showed the main toxicogenic genera, Aspergillus, Penicillium and Fusarium, as prevalent. OTA producer strains were found and many samples yielded OTA levels higher than the permissible limits. OTA survey in raw materials and storage practices must be investigated to determine their occurrence and to establish the livestock toxicological risk in cow's feed.