Natural occurrence of aflatoxins (B₁ and M₁) in feed, plasma and raw milk of lactating dairy cows in Beja, Tunisia, using ELISA

Abstract

Beja is an agricultural area in northwest Tunisia. It contributes to national needs by offering cereals and milk to the market for human and animal consumption. A small number of studies on mycotoxin occurrence in feedstuffs and raw milk from lactating dairy cows in this region are available. Therefore, 226 samples were collected from farms and local markets during November 2008 until April 2010. Samples consisted of 112 raw cow milk, 56 blood from lactating cows and 58 feed destined for dairy cows. Plasma and feed were analysed for aflatoxin B₁ (AFB₁). Milk samples were analysed for aflatoxin M₁ (AFM₁). All samples were treated using a simultaneous methanolic-aqueous extraction, followed by immunoaffinity column clean-ups and were investigated by competitive enzyme-linked immunoabsorbent assay (ELISA). Recoveries were 80%-95% and 81%-92% for AFB₁ and AFM₁, respectively, while the limit of detection (LOD) was 0.01 µg/kg or µg/l for both mycotoxins. Results revealed the presence of AFB₁ in 84.4% of the feed samples (mean 18.7 ± 1.4 µg/kg), and 39.2% of the plasma-examined samples (median 7.1 ± 1.0 µg/l) were found to be contaminated at levels higher than the Tunisian and the European Union (EU) limit for dairy animals, which are 20 and 5 µg/kg in animal feed, respectively. AFM₁ was detected in 60.7% of the cow raw milk samples examined (median 13.6 ± 1.4 µg/l). Contaminated levels were higher than the EU limit of 0.05 µg/l. It was concluded that more precaution should be taken on hygiene controls in order to prevent fungal contamination.

Keywords: ELISA; aflatoxin B1; aflatoxin M1; feedstuff; occurrence; plasma; raw milk; risk.