The digestibility of the proteins of broad bean (Vicia faba) and soya bean (Glycine max) under in vitro conditions simulating the alimentary tracts of rainbow trout (Salmo gairdneri) and carp (Cyprinus carpio)

The in vitro digestibility of the proteins of broad bean and soya bean was compared by using a physiologically oriented method developed in our laboratory. The physical and chemical conditions of the alimentary tracts of rainbow trout and carp were simulated in vitro as closely as possible. Generally protein digestibility of broad bean is poorer than that of soya bean. Differences in digestibility are more pronounced after digestion under the simulated conditions of the carp gut than under those of the trout gut. The deficiency in the sulfuric amino acids cysteine + methionine is more marked in broad bean than in soya bean. Furthermore, in broad bean, threonine and lysine (for carp) and phenylalanine (for trout) are near or slightly below the limits of dietary requirement.