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) 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/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 ( < 0.05). Ultimate load, bending moment, stiffness and energy to fail were decreased ( < 0.05) in broilers fed diets deficient in Ca and P. Addition of 25OHD did not influence performance but significantly increased serum 25OHD levels. Furthermore, the addition of 25OHD caused an increased tibial and femoral bone density and femoral hydroxyproline content ( < 0.05), increased bending moment in tibias ( < 0.05), and enhanced ultimate load and bending moment in femurs ( < 0.05). No significant interactions were observed for bone properties. Overall, feeding 25OHD at 69 μg/kg feed to broilers had no effect on growth performance but partly improved bone biochemical and biomechanical properties of broiler starters.