Weaned piglets were fed a wheat based diet either non-supplemented or supplemented with a multi-enzyme preparation or a xylanase mono-enzyme preparation, respectively. Both enzyme preparations increased live weight gain nonsignificantly, but only animals of the xylanase group showed a trend (p = 0.076) for an improved feed conversion. Only precaecal digestibility of total amino acids was improved significantly when the mono-enzyme preparation was added. Improvements of digestibility of crude fat, crude protein and starch did not reach the significance level. Both enzyme preparations reduced jejunal viscosity, however viscosity in the colon was only reduced by the mono-enzyme preparation. Both enzymes significantly reduced Lactobacillus spp. cell numbers as well as bacterial metabolites in the stomach and showed similar nonsignificant modifications in jejunum contents except for acetate in the mono-enzyme group. Total jejunal bile acids were unchanged. Compared to the control, the ratio of the main conjugated to the main deconjugated bile acid was significantly higher in the mono-enzyme group. This study has shown that the mono- and multi-enzyme preparation can lead to improved performance in wheat based diets for piglets. Like in poultry, the main mode of action seems to be the reduction of small intestinal viscosity. However, the generation of fermentable carbohydrates by the multi-enzyme preparation may mask beneficial effects on performance due to the development of an active bile acid deconjugating microbiota in the small intestine.