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.

Twenty-four multiparous Holstein cows were randomly assigned at calving to treatment diets using a modified split-plot design to determine the effects of protein source on milk production and composition. The treatment diets consisted of an 80:20 combination of corn and alfalfa silages and whole cottonseed at 12% of the dietary dry matter (DM). The treatment diets were formulated to contain 17% crude protein (CP) and 20% acid detergent fiber on a DM basis. One of the following sources of supplemental CP was included in each treatment diet: 1) cottonseed meal, 2) cottonseed meal plus a rumen-undegradable protein (RUP) supplement, 3) soybean meal, and 4) soybean meal plus an RUP supplement. Cows were fed the initial treatment diet for 6 wk and then were switched to the other oilseed meal source but continued to receive the same amount of RUP during the second period of the study. Milk production and composition were not affected by treatment diet. Cows fed treatment diets without RUP supplementation consumed more DM and thus more CP. Supplementation with RUP resulted in greater milk production efficiency per unit of DM consumed. Cows fed treatment diets containing cottonseed meal had higher plasma gossypol concentrations than did cows fed treatment diets containing soybean meal. Plasma gossypol concentrations for all cows in each group were below the recommended upper limit that is considered to be safe. Data suggest that cottonseed meal in the diet can be substituted for soybean meal, resulting in similar milk production and composition.