Studies on Aflatoxin Detoxification in Shelled Corn by Ensiling

ince the mechanical picker-sheller has come into widespread use for harvesting field corn, farmers generally are confronted with the problem of safe storage of highmoisture shelled corn. The moisture content of field-shelled corn is often too high for direct binning, and storing such grain in regular farm bins without first lowering the moisture level is almost certain to result in spoilage. Molds grow readily in corn having a moisture content above 15.5 %, and with growth of molds there is potential danger of mycotoxin formation (Steinberg and Nelson, 1969) which would render the grain unsuitable for feed (Forjacs, 1965; Forjacs and Carll, 1962; Hesseltine, 1967). High-moisture corn can be preserved by ensiling (Burmeister et al., 1966; Foster et al., 1955). It is known, too, that aflatoxin B, can be converted by acid catalysis to aflatoxin B2• (Ciegler and Peterson, 1968; Pohland et al., 1968), a compound possessing less than Ihoo the toxicity of B1 (Lillehoj and Ciegler, 1969). Since lactic and other organic acids are produced in a silage fermentation (Barnett, 1954), it seemed expedient to determine whether ensiling moldy, aflatoxin-containing corn would render it nontoxic and possibly suitable for livestock feed. Similar studies have been made on the degradation of DDT in forage silage made from pasture grass contaminated with the insecticide (Henzell and Lancaster, 1969). In addition, it is possible that the mixed microflora of a silage fermentation might directly degrade aflatoxin, since it has been shown that aflatoxin partially disappears in peanuts contaminated with a mixed fungal flora (Ashworth el al., 1965). However, Ashworth's study did not demonstrate that actual degradation by microorganisms was involved, and other evidence indicates that direct degradation of aflatoxin by microorganisms does not occur (Ciegler et al., 1966a,b; Ciegler and Peterson, 1968). To convert aflatoxin B1 in moldy corn to the nontoxic form through ensiling, a lactic fermentation resuiting in maximal acid production is a prime requisite. Various means have been explored for this purpose in forage silage; e.g., addition of molasses or a Lactobacillus culture to the chopped material during silo filling (Barnett, 1954). We have tested some of these methods for their capability to enhance lactic fermentation and, subsequently, to detoxify aflatoxin in shelled corn.