Effect of inulin and oligofructose on performance and bone characteristics of broiler chickens fed on diets with different concentrations of calcium and phosphorus.

1. In a 6-week experiment with broilers, the effect of diet supplementation, using prebiotic fructans, on the performance and biomechanical and geometrical parameters of the tibia and femur bones was evaluated. 2. A total of 240, 1-d-old, Ross 308 chickens were randomly assigned to 1 of 6 treatments, each comprising 5 replicate cages, with 8 birds (4 male and 4 female) per cage. A 2 x 3 factorial arrangement was employed, with two dietary concentrations of calcium and available phosphorus (standard: 9 x 4/9 x 2 g Ca/kg and 4 x 3/4 x 0 g P available/kg; or reduced: 8 x 3/8 x 1 g Ca/kg and 3 x 7/3 x 5 g P available/kg, for the starter/finisher feeding phases, respectively), and with three diets supplemented by selected prebiotics (none; inulin, 7 x 0 g/kg; oligofructose, 7 x 0 g/kg). 3. The concentration of Ca and available P in the diet had no effect on performance parameters at 21 and 42 d of age. At 42 d, reducing the dietary concentrations of Ca and P significantly decreased such biomechanical parameters of bones as tibia stiffness (by 9 x 2%); and femur breaking strength (by 5 x 8%) and stiffness (by 5 x 1%). The diet with a lower concentration of Ca and P negatively affected such geometrical parameter of the tibia as the cross section area, but had no effect on cortex thickness, or bone weight and length. 4. At 21 or 42 d of age, broilers fed on diets supplemented with inulin or oligofructose displayed a performance similar to those fed on the unsupplemented diet. The prebiotics under study also had no statistically significant effects on the biomechanical and geometrical parameters of either bone. There were no significant Ca and P concentration x prebiotics interaction effects, on either performance parameters or on bone quality indices. 5. It was thus concluded that inulin and oligofructose do not improve the performance and bone quality of broilers, either when fed on diets with a standard concentration of Ca and available P, or with reduced concentrations of these macrominerals.