Influence of xylanase supplementation on the apparent metabolisable energy and ileal amino acid digestibility in a diet containing wheat and oats, and on the performance of three strains of broiler chickens

A commercial xylanase product was assessed for its effects on the performance of, and apparent metabolisable energy (AME) and ileal amino acid digestibility in, 3 commercial broiler strains (Strain A, B, and C) fed on a diet containing wheat (407 g/kg) and oats (78 g/kg). Exogenous xylanase improved weight gains (P = 0.07) and feed/gain (P < 0.04) of broilers, irrespective of genotype. Performance parameters significantly differed among the broiler strains. Strains A and C consumed more (P < 0.04) feed, and grew faster (P < 0.01) and more efficiently (P = 0.07) than Strain B. Enzyme supplementation resulted in 2.8% improvement (P < 0.05) in the AME of the wheat-based diet. The AME tended to be higher (P = 0.09) with Strain A (13.46 MJ/kg dry matter) and Strain C (13.57 MJ/kg dry matter) than with Strain B (13.10 MJ/kg dry matter). The apparent ileal digestibility of all amino acids was 1–2 percentage units higher in birds fed on the enzyme-supplemented diet than in those fed on the unsupplemented diet (controls), but the differences were significant (P < 0.05) only for threonine, methionine, isoleucine, arginine, aspartic acid, serine, and glutamic acid. Highly significant (P < 0.001) strain effects were observed for apparent ileal digestibility of all amino acids, with Strain A recording the highest (0.807–0.945) and Strain B the lowest (0.710–0.912). Mean ileal digestibility coefficients of the 15 amino acids in wheat-based diets for Strains A, B, and C were 0.858, 0.791, and 0.828, respectively. Ileal digesta viscosity was low, and was not affected by dietary enzyme, suggesting that other factors were responsible for the observed improvements in bird performance.