Texas Bentonites as An Amendment of Aflatoxins in Poultry Feed.

Aflatoxins are toxic metabolites produced by fungi in grains. Moderately contaminated grains that cannot be used as food are often directed to animal feed. Economically-feasible detoxification measures for contaminated feeds are needed. The objectives of this research were to identify effective bentonites as aflatoxin adsorbents and to evaluate the performance of the clays as aflatoxin amendments in feeds for broiler chickens. Five bentonite samples from Gonzales, Texas, USA were collected and characterized by the published selection criteria for aflatoxin adsorbents (Dixon et al, 2008). Aflatoxin adsorption capacity, pH, CEC, organic carbon, particle size distribution, and mineralogical and structural compositions of the bentonites were analyzed.  Two bentonites were identified as potentially good aflatoxin adsorbents based on the analyses. These two bentonites were selected for an in vivo poultry experiment where chickens were fed with highly aflatoxin-contaminated corn to test the efficacy of the clays in detoxifying aflatoxins. Also, detailed mineralogy analyses were conducted on these two samples after size fractionation. Clay 4TX and 1TX contained 87% and 65% clay, respectively. Smectite was the dominant mineral phase in the clay fractions of the two bentonites. Other minerals were also present and it is not likely that the zeolite, quartz, or feldspars will cause harmful effects on the chickens, but the presence of pyrite and heavy metals in 1TX raised concerns about its use in animal feed. These investigations indicate that certain bentonites can effectively adsorb aflatoxin in vivo. Directly mixing the high-adsorbing bentonites as dry powder to highly contaminated poultry feed can reduce the acute aflatoxin toxicity to broiler chickens but does not eliminate it.