Effects of the procedure of inclusion of a sequestering agent in the total mixed ration on proportional aflatoxin M1 excretion into milk of lactating dairy cows

The objectives were to determine changes of aflatoxin M1 (AFM1) concentration and proportional excretion in milk of lactating cows when adding a commercial sequestering agent (SA) to a total mixed ration (TMR) contaminated with aflatoxin B1 (AFB1) from different feeds and how these changes were affected by different ways of adding the SA to the TMR. Two experiments were completed using eight cows each and the same TMR which had a common forage base of corn silage, alfalfa and grass hays (300, 250 and 50g/kg dry matter, respectively) to which AFB1-contaminated feeds were added. The AFB1 ingestion period was 9 days followed by a 5 day clearance period. In experiment 1, cows were randomly assigned to one of the two diets in a completely randomized design and fed a control diet made of forages plus AFB1-contaminated corn meal plus a pelleted protein/mineral/vitamin premix (Pmx) or the CC-SA diet of forages plus AFB1-contaminated corn meal with SA plus the pellet Pmx. In experiment 2, cows were randomly assigned to one of four diets in a replicated 4x4 Latin square design. Diets were CC-SA (forages plus AFB1-contaminated corn meal with SA plus a pellet Pmx), Pellet-SA (forages plus an AFB1-contaminated complete concentrate with SA as a pellet), Meal-SA (forages plus AFB1-contaminated complete concentrate with SA as a meal) and PMX-SA (forages plus AFB1-contaminated corn meal plus a pellet Pmx with SA). Milk samples were collected at days 0, 3, 5, 7, 9, 11 and 14 of each period and analyzed for AFM1 content and the proportion AFB1 excretion in milk was calculated. In experiment 1, milk AFM1 concentration and proportional excretion were reduced (47% and 44%, respectively; P<0.05) when SA was added to the diet. In experiment 2, the lowest (P<0.05) proportional AFB1 excretion (0.013) occurred in milk from cows feed the Pellet-SA diet. The PMX-SA diet obtained higher (P<0.05) AFM1 concentration in the milk (120ng/kg) when compared to other ways of SA inclusion (97, 76 and 11ng/kg, respectively for CC-SA, Pellet-SA and Meal-SA diets).