In an experiment carried out on 560 broiler chickens, the effect of supplementing diets with particulate limestone (grit, diameter 1.2-4 mm) and 25-hydroxycholecalciferol (25-OH-D₃) on selected biomechanical parameters of tibia bones was studied. Replacement of 30% of pulverized limestone by grit increased ultimate load, yielding load and stiffness of tibias at 43 days of age. Partial or complete substitution of 25-OH-D₃ for cholecalciferol positively affected yielding load and stiffness of bones. The best quality of tibia bones was found in chickens fed a diet with simultaneous addition of grit and replacement of 90 or 100% of cholecalciferol by 25-OH-D₃.