Investigation of organophilic montmorillonite clay inclusion in zearalenone-contaminated diets using the mouse uterine weight bioassay

Previous studies with low-pH montmorillonite (LPHM) clay exchanged with alkylammonium compounds showed that these organo clays were quite effective in sorbing the estrogenic mycotoxin zearalenone (ZEN) from aqueous solution. The potential toxicity of these types of clays, in particular hexadecyltrimethylammonium (HDTMA) LPHM, led to the investigation of the sorption efficacy of clay exchanged with a less toxic primary amine analog, hexadecylamine (HDA). Isothermal analysis studies showed that HDA LPHM was able to bind ZEN, but less effectively than HDTMA LPHM as evidenced by a significantly lower Freundlich K (63,900 vs. 845). The in vivo effectiveness of these two clays to bind ZEN was tested utilizing the mouse uterine weight bioassay. At a dietary inclusion level of 0.25%, the clays did not have a negative impact on overall animal health as measured by final body weight; however, they did not protect the animals from the estrogenic effects induced by 35 mg ZEN/kg in the feed (i.e., the uterine weights were not reduced in comparison to ZEN alone). In fact, the HDTMA LPHM group showed an increase in uterine weight that was more than the ZEN treatment group. When the animals were fed 0.5% clay, both exchanged clays (i.e., HDTMA LPHM and HDA LPHM) resulted in decreased body weight gain. The uterine weights of ZEN-fed animals (either alone or in combination with clays) were not significantly different from each other. In contrast, the uterine:body weight ratio showed a dramatic increase in the groups fed exchanged clay + ZEN compared to ZEN alone. These results suggest that alkylamine groups may assist the transport or uptake of ZEN and result in an enhanced toxicity from contaminated feed. The findings from this study clearly demonstrate the need for careful testing of all mycotoxin-binding agents before their inclusion in the diet.