DETOXIFICATION OF JACK BEANS (CANAVALIA-ENSIFORMIS) - STUDIES WITH YOUNG CHICKS

Two experiments were conducted with young chicks to examine the efficacy of extraction procedures, heat treatments and dietary supplements of amino acids+potassium acetate on the nutritive value of jack beans. Extraction of whole beans with an aqueous solution of KHCO3 (10 gl-1) at 80-degrees-C for 48 h followed by autoclaving for 1 h at 121-degrees-C reduced the concentration of canavanine, a toxic amino acid, to negligible quantities. Inclusion of KHCO3-extracted beans at levels of up to 280 g kg-1 diet allowed growth rates, intakes of food and apparent metabolisable energy (AME(N)) and efficiency of food utilisation which were equivalent to those observed in control groups. Simple aqueous extraction at 100-degrees-C with subsequent autoclaving was markedly less effective as a detoxifying technique than using the KHCO3 solution, while microwave treatment was only marginally less effective than autoclaving of KHCO3-extracted jack beans. A residuum of toxicity associated primarily with a depression of N retention efficiency was recorded in groups fed on KHCO3-treated autoclaved beans; however, a marked improvement in N utilisation occurred on supplementing diets containing this product with a mixture of lysine, arginine, tryptophan and potassium acetate.