Cereal grains, such as wheat, have been regarded as one of the most affordable ingredients to supply dietary energy for fast growing broilers. However, broilers compete with humans for wheat to satisfy their nutritional needs and also they cannot effectively utilise wheat due to the limited ability of their gut enzymes to utilise dietary fibre. The efficiency of wheat utilisation can be increased by adding exogenous enzymes into cereal based diets for these birds (Annison and Choct, 1993). These enzymes can also reduce fermentation in the small intestine and so help maintain the gut health. Therefore, we compared the effect of adding a commercial fibrolytic enzyme to wheat and barley-based diets on the utilisation of either diet by broilers from 0 to 35 days of age.