Biochemical characteristics of wheat and their relation with apparent metabolisable energy value in broilers with or without non-starch polysaccharide enzyme

Exogenous non-starch polysaccharide (NSP) enzymes do not always exhibit the same improvement in AMEn (apparent metabolisable energy corrected for nitrogen balance) in wheat-fed broiler chickens. In order to understand the factors that determine this variation, the in vitro mode of action of an NSP enzyme preparation (Rovabio Excel) was investigated in several wheats and wheat extracts. In vivo experiments were also performed in broilers fed seven different wheat cultivars. In vitro studies showed an important solubilisation of insoluble arabinoxylan (AX) in wheat flours, ranging from 65 to 85% depending on the wheat cultivar. The negative correlation observed between arabinose/xylose ratio and AX solubilisation (r² = 0.45, P = 0.001) suggests that the variation in solubilisation can be partly explained by the AX structure. NSP enzymes are also able to hydrolyse wheat bran AX by 30-50% depending on the enzyme dosage. Whereas rapid solubilisation of insoluble AX was confirmed in pig digestive physiological conditions (TIM-1), only a minor proportion of AX was hydrolysed as