1. This study investigated the nutritional value (digestibility of ileal crude protein and amino acids (AAs)) and the AMEN value of legumes (pea, faba bean, yellow lupin, and narrow-leaved lupin) with or without protease. 2. Two hundred, one-day-old, male Ross 308 broiler chickens were randomly allocated to ten groups. Each group received one of five different protein raw materials - either peas, faba beans, yellow lupins or narrow-leaved lupins, with or without protease produced from Bacillus licheniformis. The birds were kept in individual cages. Nutrient digestibility was calculated using the difference method. The total duration of the study was 23 d, and the study involved two phases - accommodation phase (d 1-18) and experimental phase (d 18-23). 3. The effect of protease on response traits was not consistent between the legumes. The enzyme increased the digestibility of some AAs in the pea (arginine, leucine, phenylalanine, histidine, tyrosine, alanine, and proline), faba bean (lysine, arginine, glycine, and asparagine), and yellow lupin diets (lysine, valine, and serine), but this effect was not observed in the narrow-leaved lupin diet. The change in AMEN values due to protease addition was only statistically significant for the pea diet (P < 0.05), whereas in the case of other legume species, the difference was insignificant (P > 0.05). 4. Exogenous protease increased the digestibility of AAs present in pea, faba bean, and yellow lupin seeds but not in narrow-leaved lupin diets. The AMEN value of peas increased with protease supplementation, but no effect of protease was found for the AMEN values of faba bean and both the lupin diets.
Keywords: Protein; broiler chickens; digestibility; protease.