Effects of Water-Soluble Feed Components, Such as Proteins, On Aflatoxin Binding to Clays.

Clays are added to animal feed to improve the physical properties and can bind mycotoxins, such as aflatoxins, only after ingestion because clays are mixed with dry feed.  Simple adsorption isotherms from pure water measure aflatoxin adsorption capacities, which usually do not correlate to animal feeding studies because adsorption conditions for ingested clays are different.  Soluble compounds in feed can affect mycotoxin binding to feed additives.  Aflatoxin adsorption to clays and other feed additives mixed with feed materials, such as corn and peanut meal, correlated with animal feeding studies.  Mycotoxins must compete with proteins and other water-soluble feed components for ingested clay adsorption sites.  Organic compounds adsorbed to clays can increase contaminant sorption, but adsorbed feed solubles would more likely decrease mycotoxin sorption.  Adsorption of water-soluble compounds in peanut meal to the montmorillonitic feed additive, Novasil plus, reduced the N₂ surface area from 68 to 13 m²/g and activated carbon from 940 to 173 m²/g.  Soluble compounds from corn and peanut meal adsorbed to clays and activated carbon increased the %C and %N and reduced aflatoxin and BSA protein adsorption.  Selection tests to identify feed additive materials that can effectively bind mycotoxins in feed should include adsorption tests directly from feed or feed ingredients, such as corn meal.  Expensive animal feeding studies are needed to establish with certainty that a feed additive can prevent mycotoxicoses, but mycotoxin adsorption from feed materials might be used to more economically identify feed additives that effectively bind mycotoxins.