Effects of dietary calcium and phosphorus levels and supplementation of 25-hydroxycholecalciferol on performance and bone properties of broiler starters.

To investigate effects of dietary calcium (Ca) and phosphorus (P) levels and 25-hydroxycholecalciferol (25OHD ₃ ) supplementation on performance and bone properties of broiler starters, 224 male Arbor Acre broilers were used in a 21-d trial. Broilers were allotted to one of four treatments in a 2 × 2 factorial arrangement including diets either normal or low in Ca and P, which were further supplemented or not with 69 μg 25OHD ₃ /kg feed. Feeding low Ca and P diets significantly reduced performance of boilers and decreased ash, Ca, P and hydroxyproline contents in tibias and femurs ( p < 0.05). Ultimate load, bending moment, stiffness and energy to fail were decreased ( p < 0.05) in broilers fed diets deficient in Ca and P. Addition of 25OHD ₃ did not influence performance but significantly increased serum 25OHD ₃ levels. Furthermore, the addition of 25OHD ₃ caused an increased tibial and femoral bone density and femoral hydroxyproline content ( p < 0.05), increased bending moment in tibias ( p < 0.05), and enhanced ultimate load and bending moment in femurs ( p < 0.05). No significant interactions were observed for bone properties. Overall, feeding 25OHD ₃ at 69 μg/kg feed to broilers had no effect on growth performance but partly improved bone biochemical and biomechanical properties of broiler starters.