Thirty-two crossbred barrows were fed from about 28 to 100 kg body weight on a coarsely ground (800 µm) diet with a standard protein content (diet C), and on two finely ground (500 µm) diets with protein contents lowered by 8%, with or without supplementation with glucanase and xylanase (diets F and FE, respectively). Fine grinding (diet F vs C) and enzyme supplementation (diet FE vs F) increased protein digestibility, while grinding also increased energy digestibility. Pigs fed the F and FE diets excreted less nitrogen and retained the same amount of nitrogen as animals on diet C. Daily gains, feed utilization, carcass leanness, and fat and protein contents in Musculus longissimus dorsi were not significantly affected by treatment. Protein conversion was better in groups F and FE than in C.