Detoxification of jack beans (Canavalia ensiformis): studies with young chicks

Abstract 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 KHCO 3 (10 g l −1 ) at 80°C for 48 h followed by autoclaving for 1 h at 121°C reduced the concentration of canavanine, a toxic amino acid, to negligible quantities. Inclusion of KHCO 3 -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°C with subsequent autoclaving was markedly less effective as a detoxifying technique than using the KHCO 3 solution, while microwave treatment was only marginally less effective than autoclaving of KHCO 3 -extracted jack beans. A residuum of toxicity associated primarily with a depression of N retention efficiency was recorded in groups fed on KHCO 3 -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.