The presence of aflatoxin B1 in livestock's feed results in contamination of milk and its productswith aflatoxinM1. Different sequestering agents have been added to cows' ration to adsorb these toxins, although influence of processed bentonites on aflatoxins adsorption has not been evaluated yet. This experiment was carried out to assess the effects of incorporating natural and processed bentonite (local or commercially available), to the diet of Holstein dairy cows subjected to an aflatoxin B1 diet, and the transfer of aflatoxin metabolites (AFM1) to milk. Aflatoxin sequestering capacity, pH, CEC, XRD and XRF of natural and processed bentonites were measured. Then, twelve Holstein dairy cows were assigned to 3 treatments as the following: 1) local processed bentonite (G.Bind™), 2) local unprocessed bentonite (F), and 3) commercially available bentonite (M). Aflatoxin content in feed and milkwas evaluated and transfer rate was measured. Results of the present study showed that the aflatoxin contents of milk were remained unchanged except for treatment G.Bind™ that considerably decreased aflatoxin M1 in milk after the second and third weeks of the experiment. G.Bind™ lowered the transfer rate of aflatoxin B1 from 1.17% at the beginning of the experiment to 0.43% and 0.39% after the first and second weeks, respectively. Processing of bentonites (basic processing in present study) can considerably help to adsorb aflatoxin from feed and also to decrease aflatoxin transfer to milk.

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