Experiment was carried out on 6 groups of Avian broilers, in two replicates of 85 birds in each. They were fed the same starter diet containing 22% crude protein and 12.27 MJ/kg. From 22 to 49 days of age, 6 grower diets based on 65% maize, 67% wheat, wheat plus 15% or 30%, husky or dehulled oats were offered. All diets were isoprotein and isoenergetic ones and were fed as a mash. In one replicate of each group various Avizyme preparations were supplied according to composition of the diet. Chemical composition of ground cereals, content of amino acids and content of soluble and insoluble dietary fibre as well as content of AX, Gin and NCP were determined. Viscosity of digesta were measured in 6 birds aged 36 days, from each of 12 subgroups. Four males and four females from each group were taken for carcass analysis. Fatty composition of abdominal fat pads in 4 hens from each replicate of the group 1, 2, 4 and 6 were analysed. Dehulled oats contained 2.5 times less dietary fibre, however, 3 times more water-soluble glucans than husky oats. The heaviest (2287 g) were broilers fed maize diet, while the lightest – wheat diet. There were no statistically significant differences between body weights of chicken fed maize or wheat-oats diets. Avizyme had no beneficial effect on body weight. Feed efficiency of diet containing 30% dehulled oats was as good as that of maize diet, and when supplemented with Avizyme 1100 – even better. PUFA/SFA fatty acid ratio in abdominal fat pads was 0.48 when maize diet was fed, and 0.41 when diet contained 30% dehulled oats, while with wheat diet was only 0.35.