Influence of wheat hardness and xylanase supplementation on the performance, energy utilisation, digestive tract development and digesta parameters of broiler starters

Abstract

The aim of this study was to examine the influence of wheat hardness and xylanase supplementation on the performance, energy utilisation, digestive tract development and digesta parameters of broilers fed wheat-based diets. The experimental design was a 2 × 2 factorial arrangement of treatments evaluating wheat hardness (soft or hard) with or without xylanase supplementation. Two diets based on soft or hard wheat were formulated. Whole wheat (200 g/kg) from the same wheat batch replaced ground wheat before cold-pelleting of each diet. Each diet was fed ad libitum to six pens of eight male broilers each from day 1 to 21 posthatch. The distribution of particle size differed between diets, with the hard wheat diet having 32.7% of particles greater than 1 mm in size compared with 18.7% in the soft wheat diet. Interactions (P < 0.05) were observed between wheat hardness and enzyme supplementation for weight gain, feed intake, feed per gain and nitrogen-corrected apparent metabolisable energy (AMEn). Enzyme supplementation increased (P < 0.05) weight gain in the soft wheat-based diet but not in the hard wheat diet. Enzyme supplementation also increased (P < 0.05) feed intake in the soft wheat-based diet, but reduced (P < 0.05) intake in the hard wheat diet. Feed per gain and AMEn were improved (P < 0.05) by enzyme supplementation in the hard wheat-based diet, while no enzyme effect was observed in the soft wheat diet. Feeding the hard wheat-based diet increased (P < 0.05) the relative gizzard weight, and this was associated with a general increase in finer particles in the proximal intestinal digesta when compared with those present in the diet. These results suggest that the response of broilers to xylanase supplementation is influenced by wheat hardness and that wheat hardness may be an important criterion to consider when choosing for whole wheat inclusion in broiler diets.