Precaecal amino acid digestibility of dehulled or toasted plus dehulled lupin and pea grains in broiler chickens

The use of legume grains as a protein and energy source in broiler rations promotes regional feed production and offers ecological and economic advantages over imported feed. The feeding value of legume grains can be limited by antinutritional factors. Three consecutive experiments were conducted to determine precaecal amino acid (AA) digestibility of native (experiment 1), dehulled (experiment 2) or toasted and dehulled lupin and pea grains (experiment 3). For each experiment, the grains were ground through 2- or 3-mm sieves, mixed into experimental diets and pelleted. The digestibility of AA was estimated by linear regression using ileal digesta samples of broiler chickens 34 d of age. Total precaecal AA digestibility of 2-mm and 3-mm ground lupin grains was 83 and 85% (native), 89 and 91% (dehulled) and 90 and 87% (toasted plus dehulled), respectively. Total precaecal AA digestibility of 2-mm and 3-mm grounded pea grains was 81 and 81% (native), 95 and 94% (dehulled) and 87 and 86% (toasted plus dehulled), respectively. Particle size had no effect on precaecal AA digestibility and no difference was found between the legume species. Dehulling increased precaecal AA digestibility up to 17%. The combination of toasting and dehulling led to maximal 8% improvement of precaecal AA digestibility. The improved digestibility through dehulling appears to be largely a result of tannin reduction. In this study, dehulling improved precaecal AA digestibility, but the combination of thermal treatment (toasting) and dehulling mitigated this positive effect.