Effects of Calcium and Phosphorus Levels in Starter and Grower Diets on Broilers During the Finisher Period

Abstract

Studies were conducted to determine if the calcium and phosphorus content of diets fed to broilers during the starter and grower period influenced their response to levels fed during the finisher period. Broiler chickens were grown to 42 days on diets with low, medium, or high levels of Ca and nonphytate phosphorus (NPP). At 42 days they were continued on low, medium, or high levels of Ca and NPP, or they were fed diets with no Ca or NPP supplement (Experiment 1); or they were continued on low, medium or high levels of Ca and NPP, or fed diets with 1) removal of supplemental phosphorus; 2) removal of both Ca and NPP supplements (Experiment 2).Body weight gain and feed utilization by broilers fed diets in which Ca and NPP supplements were removed from 42 to 49 days did not differ significantly from those of broilers fed similar diets in which low, medium, or high levels of Ca and NPP were maintained. However, levels of Ca and NP fed prior to 42 days and the removal of both Ca and NPP supplements from 42 to 49 days significantly influenced tibia strength. When broilers were fed low and medium levels of Ca and NPP prior to 42 days, removal of the NPP supplement alone had no adverse effect on tibia strength at 49 days. When a high level of Ca and NPP was fed to 42 days, tibia strength was significantly reduced when the NPP supplement was removed, in comparison to the control group. Maintaining a 2:1 Ca:NPP ratio during the 42- to 49-day period enabled the removal of supplemental dicalcium phosphate with minimal effect on tibia strength.