Aflatoxin B1 and deoxynivalenol contamination of dairy feeds and presence of aflatoxin M1 contamination in milk from smallholder dairy systems in Nakuru, Kenya

Background: Mycotoxins are metabolites produced by phytopathogenic and spoilage fungi in animal feed as a result of poor storage. The mycotoxins can also originate in the field and are excreted in milk when dairy animals consume such feeds, posing a public health risk concern. Methods: The aim of this study was to conduct a risk assessment in the informal sub-value chains of rural and peri-urban dairy systems in Nakuru County, by determining the prevalence and quantity levels of mycotoxins in animal feeds and milk. A total of 74 animal feed samples and 120 milk samples were simultaneously collected from individual cows and actors in the informal dairy value chain. Feed samples were analyzed for Aflatoxin B1 (AFB1) and Deoxynivalenol (DON) while milk samples were analyzed for Aflatoxin M1 (AFM1) using commercial Enzyme Linked Immune Sorbent Assay (ELISA) method. Results: Aflatoxin B1 contamination levels in 56 % (41/74) of the animal feeds exceeded the European Union (EU) limits of 5 μg/kg ranging between 0 and 147.86 μg/kg. Deoxynivalenol (DON) was identified in 63 % (27/43) of all the animal feeds ranging between 0 and 179.89 μg/kg. In the peri-urban dairy system, 48.5 % (33/68) of the milk samples were contaminated with the AFM1 concentration above the EU regulation of 0.05 μg/L ranging between 0.017 and 0.083 μg/L. All milk samples from the rural dairy system had AFM1 contamination levels below the EU limits of 0.05 μg/L ranging between 0 and 0.041 μg/L. Linear regression model showed significant association of abiotic factors; pH, water activity and moisture content of animal feed with AFB1 and DON contamination of the animal feeds. Conclusions: The results obtained from this study indicate that the peri-urban dairy farms, where intensive management predominate face the challenge of quality feeds, and one contributing factor is the on-farm production and handling of animal feeds.