Effet chez le porcelet d'une exposition à un régime co-contaminé en ...

INTRODUCTIONII. CHEMICAL METHODS1) AmmoniationTreatment with ammonia in the gaseous phase, or with substances capable of releasing it,achieved optimum results in detoxifying corn meals, especially for aflatoxins reduction. It has beenwidely demonstrated that the efficacy of mycotoxins detoxification with ammonia is positivelycorrelated with the quantity used, reaction time, temperature and pressure levels. Since few data onammonia treatment have been reported for other mycotoxins, the section on aflatoxindecontamination is presented in more details.First outcomes on the chemical inactivation of aflatoxin by ammoniation were reported forcottonseed and peanut meals (Dollear et al., 1969). Nowadays, it is an approved procedure and amethod of choice for the detoxification of aflatoxin-contaminated agricultural commodities andfeeds, in some of the North American states (Arizona, California, Georgia, Alabama), in France, inSenegal, in Sudan, in Brazil, in Mexico and in South Africa.While at least five types of ammoniation processes have been described or patented, the twoprocedures considered most practical are a high temperature/high pressure process used bycommercial treatment plants and an atmospheric pressure/ambient temperature process for in situfarm usage. Both procedures have the advantages of removing up to 90% of aflatoxin contaminationin the matrix.Aflatoxin B1 degradation by ammonia proceeds through hydrolysis of the lactone ring followed bydecarboxylation to aflatoxin D1 and loss of the cyclopentone ring to give a compound of a molecularweight of 206 daltons. It was also observed that the AFB1 molecular structure is irreversibly altered ifexposure to ammonia lasts long enough. In contrast, if exposure is not sufficiently protracted, themolecule can revert to its original state. To note that the addition of formaldehyde in the process,allows to reduce the use of ammonia, to break more easily the lactone ring and to avoid thereversibility of the reaction.The studies concerning the safety of ammoniation process began in 1983, where no signs oftoxicosis occurred in rats fed ammoniated aflatoxin-contaminated corn, in contrast to rats fed withuntreated aflatoxin-contaminated corn (Norred and Morrissey, 1983). A comprehensive review onfeeding trials carried out to evaluate the safety of ammoniated feed, was published by Park et al.(1988; see Table 7). In addition, toxicity assessment of metabolites obtained after aflatoxinprocessing was reported (Park, 1993; see also Table 7). More recently, an experiment on broilerchicks suggests that replacement of aflatoxin-containing maize with ammoniated grains significantlysuppress aflatoxicosis, leading to an improvement in production parameters in broilers (Allameh et61