The experiment was performed on 1296 Isa Brown laying hens aged 35 weeks. Hens were allocated to 6 groups and fed for 13 weeks on diets in which 30% of whole wheat or ground or whole rye was substituted by ground wheat. Rye diets were fed unsupplemented or supplemented with a feed enzyme (pentosanase and β-glucanase). Rye-containing diets (ground or whole) supported comparable productive performance to the wheat control diet in respect to hen-day egg production (81% on average) and feed conversion. Crop content and gizzard mass were significantly (P≤0.05) larger in the group fed the whole wheat containing diet. Viscosity of digesta was significantly (P≤0.05) higher on unsupplemented whole vs. ground rye diet (11.5 vs. 5.0 cP in proximal and 28.5 vs. 16.5 cP in distal part of the small intestine, respectively) but diminished significantly (to 5.1 and 8.3 cP) after enzyme supplementation.