Mycopathologia 157: 233–241, 2004. © 2004 Kluwer Academic Publishers. Printed in the Netherlands. 233 Aflatoxin Binders II: Reduction of aflatoxin M1 in milk by sequestering agents of cows consuming aflatoxin in feed Duarte E. Diaz 1 , Winston M. Hagler Jr. 2 , John T. Blackwelder 1 , Julie A. Eve 1 , Brinton A. Hopkins 1 , Kevin L. Anderson 3 , Frank T. Jones 4 & Lon W. Whitlow 1 1 Department of Animal Science; 2 Department of Poultry Science, College of Agriculture and Life Sciences; 3 College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA; 4 Current address: Department of Poultry Science, University of Arkansas, Fayetteville, AR, USA Received 20 July 2000; accepted in final form 15 March 2002 Abstract Sequestering agents bind dietary aflatoxin B1 (AFB1) and reduce absorption from an animal’s gastrointestinal tract. As a result, they protect an animal from the toxic effects of AFB1 and reduce transfer of the metabolite, aflatoxin M1 (AFM1), into milk. Three experiments, using late-lactation Holstein cows fed AFB1-contaminated feed, were conducted to evaluate several potential sequestering agents for their abilities to prevent or reduce the transmission of AFM1 into milk. Six agents previously tested in our laboratory for AFB1 binding in vitro were evaluated in these experiments. These were: SA-20  , an activated carbon (AC-A); Astra-Ben-20  , a sodium bentonite (AB-20); MTB-100  , an esterified glucomannan (MTB-100); Red Crown  , a calcium bentonite (RC); Flow Guard  , a sodium bentonite (FG); and Mycrosorb  , a sodium bentonite (MS). Five of the six sequestering agents significantly (P< 0.01) reduced AFM1 contamination of milk (AB-20, 61%; FG, 65%; MS, 50%; MTB- 100, 59%; and RC, 31%); whereas, AC-A, activated carbon, had no effect on AFM1 transmission at 0.25% of feed. By the first milking (1 day after cows consumed contaminated feed), AFM1 appeared in milk, then reached maximum levels after three days, and was absent from milk within four days after AFB1 was removed from the feed. Sodium bentonites at 1.2% of feed showed good potential as AFB1 binders; MTB-100, a yeast cell wall product, was equally effective at 0.05% in feed. Potential AFB1 binding agents should be evaluated experimentally to demonstrate efficacy. Our data show that sequestering agents can reduce AFM1 in milk of cows fed AFB1-contaminated feed. Key words: aflatoxin B1; aflatoxin M1; bentonite; activated carbon; esterified glucomannan; sequestering agents. Disclaimer: The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service, nor criticism of similar ones not mentioned. Introduction When diets contaminated with aflatoxin B1 (AFB1) are fed to lactating animals, aflatoxin M1 (AFM1), a metabolite of AFB1, is secreted into milk [1]. Like AFB1, AFM1 is toxic and carcinogenic, although tox- icity of AFM1 is somewhat lower than that of AFB1 [2]. However, AFM1 is of great concern because of the high consumption of milk and milk products by humans, especially children; it is regulated by the U.S. Food and Drug Administration (FDA) at 0.5 ppb. Al- though the use of binding agents to remove or reduce aflatoxin is not approved by the FDA for this purpose, some montmorillonite clay products, some of which are known as hydrated sodium calcium aluminosilic- ates (HSCAS), bind AFB1 in vitro and, apparently, in vivo. These products have been shown to bind AFM1 in liquid milk [3], reduce AFM1 in milk from cows consuming AFB1 contaminated feed [4, 5], and pro- tect many species from the toxic effects of AFB1 [6].