The interaction between chick type and xylanase supplementation (Avizyme 1300) of a wheat based diet was investigated using a 32 factorial arrangement. The diet (645 g wheat/kg) was supplemented with 0 or 1g/kg xylanase and fed to broilers, broiler breeders, or pullets from 1 to 19 day-old. The basal diet was formulated based on the average of the nutrient requirements of all bird types investigated. Body weight, feed intake, feed:gain ratio, upper intestinal digesta content viscosity, and relative weights of gastrointestinal organs to body weight were determined. There were significant effects of chick type on live weight, daily gain, feed intake, and feed:gain ratio (P<0.01). During the course of this study, pullets always showed significantly lower body weight, feed intake, daily gain, and higher feed:gain ratio (P<0.05). The effect of enzyme supplementation on body weight, daily gain, and feed:gain was significant only at later age growth periods (P<0.05). The positive effect of enzyme inclusion was only pronounced in broiler chicks. Daily feed intake was not significantly affected by enzyme supplementation of the diets (P>0.05). Small intestinal digesta content viscosity was not different between different chick classes (P>0.05), but enzyme inclusion significantly (P<0.05) decreased digesta viscosity in all three chick types. Gastrointestinal tract characteristics were only affected by chick type (P<0.05). It was concluded that while performance differences between chick types were large as expected, the effect of enzyme supplementation on performance was dependent both on chick type and age. The reduction of intestinal digesta viscosity due to enzyme supplementation is not a reliable gauge of the positive enzyme effect observed on bird performance when compared across different classes of chicks.
