Three experiments were conducted to examine: (a) the apparent metabolisable energy (AME) contents, the level of non-starch polysaccharides (NSP), and the extract viscosity value of 9 wheat samples; (b) the efficacy of a xylanase in reducing between-bird variation for AME; and (c) the effect of a xylanase on the number of Clostridium perfringens in broilers fed a low AME wheat diet. Experiment 1 revealed that the AME value of wheat varied from 11.5 to 13.6 MJ/kg dry matter (DM), which negatively correlated with the total NSP level (r = –0.97). Experiment 2 involved a 48-cage individual bird trial, where xylanase increased (P < 0.05) the AME from 12.51 to 13.09 MJ/kg DM and reduced (P < 0.05) its standard deviation from 1.13 to 0.52. The standard deviation for feed conversion ratio, ileal viscosity, and faecal viscosity was also reduced. In this experiment, there was a strong correlation between AME and excreta viscosity (r = –0.81) and the caecal xylanase activity of birds fed the control diet was positively correlated with AME (r = 0.72). In Expt 3, xylanase reduced the number of Clostridium perfringens, the causative agent for necrotic enteritis, to a non-detectable level in the ileum and caeca of broilers fed a low-ME wheat diet.