In cereal-based diets, non-starch polysaccharides (NSP) lower precaecal nutrient absorption and increase endogenous protein and amino acid (AA) losses. Adding exogenous NSP-degrading enzymes aims amongst others to reduce these negative effects and to thereby improve protein and AA supply. However, biased results exist in the literature on their efficacy in growing pigs. Hence, the objective of this study was to analyse the effects of different levels of xylanase and beta-glucanase supplementation. Nitrogen (N) retention from a threonine-limited diet was chosen as an indirect indicator for differences in praecaecal threonine absorption and endogenous protein and AA losses. During three balance periods, 12 male pigs with a bodyweight of 31-66 kg were used in a cross-over design. They received three different diets based on wheat, barley, rye, and soybean meal containing 0, 40 or 80 mg/kg of an enzyme preparation containing endo-1,4,-beta-xylanase and endo-1,4-beta-glucanase. N excretion and retention were identical in animals of the different treatment groups, stressing that enzyme supplementation did not affect threonine absorption and/or endogenous protein and AA losses neither at medium nor at high supplementation level. Hence, in the present trial, beta-glucanase and xylanase addition to cereal diets did not improve protein and AA availability in growing pigs of a body weight > 30 kg.
