A dairy cow model was established to measure the transmission of aflatoxin M1 (AFM1) into milk. Four Ayrshire mid-lactation dairy cows (ranging 590 – 650 kg body weight and averaging 4.5 years of age) were used in a crossover experimental design in which each cow acted as its own control and was subjected to four dietary treatments administered as six 12-day feeding periods followed by a 7-day washout period. Periods I – VI comprised a 7 d of adaptation followed by 5 d of sampling. Period VII was a 7-d washout with sampling in the final two days. From each morning's milking, yield was recorded and sampled for AFM1 analysis by HPLC. Treatments included a negative control, contamination with AFB1 (5 µg of AFB1/kg feed), AFB1 + Mycosorb® (MTB) 10 g/cow/d, and AFB1 + MTB 50 g/cow/d. In response to the negative control, AFM1 concentrations in milk remained below the limit of detection (<5 ng/kg), whereas cows fed the AFB1-contaminated feed had milk AFM1 concentrations ranging from 110 to 230 ng/kg. At the end of the washout period, AFM1 was again undetectable. The dairy cow model was also used to test the efficacy of the yeast-cell-wall-based mycotoxin binder Mycosorb® (MTB) in reducing secretion of AFM1 into milk by cows fed the same AFB1-contaminated diet. When supplemented at 50 g/head/day, MTB significantly reduced (P < 0.05) AFM1 secretion into milk with no adverse effects on milk production. The dairy cow model is a sensitive tool for measuring aflatoxin transmission to milk and mycotoxin binder efficacy at 5 µg of AFB1/kg feed. As it is common for on-farm AFB1 concentrations to exceed 5 µg/kg, more research may be warranted to determine the effectiveness of the model at higher AFB1 concentrations.
