Interaction between dietary calcium and non-phytate phosphorus on growth performance and bone ash in early White Pekin ducklings

A 4 × 5 factorial experiment containing four non-phytate phosphorus (NPP) levels (2.0, 3.0, 4.0, 5.0 g/kg) and five calcium (Ca) levels (4.0, 6.0, 8.0, 10.0, 12.0 g/kg) was conducted to evaluate the interaction between dietary Ca and NPP on growth performance and bone ash in White Pekin ducklings from hatch to 14 days of age. A total of 1280 one-day-old male White Pekin ducklings were assigned to twenty experimental treatments, each containing 4 replicate pens with 16 birds per pen, and these birds were raised with feed and water provided ad libitum. At 14 days of age, weight gain, feed intake, feed/gain and tibia ash of each treatment were measured. In the current study, the interaction between dietary Ca and NPP significantly influenced weight gain, feed intake, feed/gain, and tibia ash but the overall effects of these two minerals on these parameters except tibia ash were not significant. The weight gain, feed intake and tibia ash decreased (P<0.01) as dietary Ca increased from 4.0 to 12.0 g/kg at the lowest NPP level (2.0 g/kg) but these adverse effects could be alleviated or reversed at other dietary NPP from 3.0 to 5.0 g/kg. Considering the significant interaction between dietary Ca and NPP, the quadratic response surface regression analysis was used to predict the Ca and NPP requirements of ducklings. According to this regression analysis, the predicted requirements of Ca and NPP for maximum weight gain and minimum feed/gain were 8.06 and 4.03 g/kg, 7.96 and 3.79 g/kg, respectively.