Heat processing is a common procedure in feed manufacture, conferring improved properties as regards the safety and nutritive value of animal feeds. For example, heat treatment of dried poultry litter appears to be an effective method for controlling, or even eliminating, contamination with Salmonella, E. coli and Campylobacter (Jeffrey et al., 1998). Thermal processing is also effective for denaturing proteinase inhibitors, lectins and cyanogens. However, for antigenic proteins, more complex procedures involving the use of hot aqueous ethanol extraction are required (D'Mello, 1991).
For aflatoxin-contaminated oilseeds destined for animal feed, ammoniation appears to be the processing method of choice. The feedstuff is treated with either ammonium hydroxide or gaseous ammonia at high temperatures and pressure in commercial feed mills, or at ambient temperature and low pressure in small-scale operations in developing countries. If the ammoniation reactions are allowed to proceed to completion, the detoxification process is irreversible and aflatoxin contamination is virtually eliminated. Providing that the residual ammonia is dissipated, diets containing the decontaminated meals are readily consumed by animals without ill-effects. Depending on the efficacy of decontamination, residues of AFM1 in the milk of dairy cows are substantially reduced or absent altogether. The adverse effects of tannin-rich forages may be overcome by treatment or spraying of foliage with polyethylene glycol, but the practical application of this procedure still has to be economically evaluated.