Non-phytate phosphorus requirement for male broilers subjected to two calcium supply regimens from 8 to 21 days of age under thermoneutral environment conditions

The purpose of this study was to determine the non-phytate phosphorus (nPP) requirement for male broiler subjected to two calcium supply regimens from 8 to 21 d of age, based on performance and bone mineralization. Birds were distributed in a complete randomized 4 x 2 factorial design with four nPP concentrations: 0.25, 0.35, 0.45 and 0.55%, and two Ca supply regimens: Ca fixed at 9.0 g/kg of diet (CaF) or varying together with the nPP concentrations tested keeping a fixed Ca:nPP ratio (CaV), with 8 battery cages/treatment and 9 birds/battery cage. Feed intake (FI), body weight gain (BWG) and Ca:P ratio deposited in the dry defatted tibia (TibCa:TibP) were quadraticaly increased by the increasing nPP concentrations, regardless of the Ca supply regimen adopted (p<0.01). The nPP levels tested also influenced FCR and TibAsh, which presented a quadratic and linear response when CaF and CaV diets were used, respectively, and TibP and TibCa, which presented a quadratic response with both Ca supply regimen, CaF and CaV diets. Also, CaV diets provided a 2.86 and 5.02% higher FCR (p<0.05) and TibCa (p<0.01), respectively, when compared to CaF diets. Therefore, nPP nutritional requirement for male broilers reared at thermoneutral conditions from 8 to 21 d of age that provided better perfonnance and bone mineralization were, respectively, 0.480 and 0.459% with CaF and 0.550% with CaV diets, indicating that, under thermoneutral conditions, CaV diets negatively affected growth performance of broilers, while positively affecting bone mineralization especially when low nPP levels are applied.