Influence of β-glucanase supplementation on the metabolisable energy and ileal nutrient digestibility of normal starch and waxy barleys for broiler chickens

The influence of β-glucanase supplementation on the nitrogen-corrected apparent metabolisable energy (AMEn) and apparent ileal digestibility (AID) coefficient of starch, protein and amino acids in four barley cultivars that differed in fibre contents (hulls) and starch characteristics (waxiness), was investigated. The cultivars included a conventional, hulled normal starch barley (C-NS), a hull-less normal starch barley (H-NS) and two hull-less waxy barleys (H-W1 and H-W2). The AMEn of the two hull-less waxy cultivars were determined to be lower (P<0.05) than those of C-NS and H-NS. The AMEn of the C-NS and H-NS barleys, irrespective of the presence or lack of hulls, were similar (P>0.05). β-Glucanase supplementation improved the AME of all barley cultivars, but the magnitude of response was markedly greater (P<0.05) in waxy genotypes compared to the normal starch genotypes. The cultivar type had no influence (P>0.05) on the AID of protein and most amino acids. Enzyme supplementation improved (P<0.001) the AID of protein and amino acids in all barley cultivars. The average AID of the 18 amino acids was increased by 11.9% by enzyme addition, ranging from 5.1% for methionine to 18.1% for threonine. These data suggest that starch characteristics and type of β-glucan may influence the available energy in barley for broiler chickens. These characteristics may be equally or more important than fibre contents in determining the feeding value of barley for poultry.