Effects of the Level and Relationship of Calcium and Available Phosphorus on the Growth and Tibia Mineralization of Broiler Starter Chickens

SUMMARY The objective of this research was to evaluate the growth performance and tibia measurements in broilers from 8 to 21 d of age fed diets with increasing levels of aP at adjusted or variable levels of Ca. A total of 168 chicks from 8 to 19 d of age were allocated in pairs per cage and randomly assigned to 6 dietary levels of aP (0.13%, 0.23%, 0.33%, 0.43%, 0.53%, and 0.63%) and 2 Ca:aP ratios, adjusted (adjCa:aP) or variable (varCa:aP). In the AdjCa diets, the Ca:aP ratio was kept at 2:1; in the varCa diets the Ca:aP ratio varied from 7.69 to 1.59. Chicks were weighed at the beginning and end of the experiment. At the last day of the trial, all chicks were killed to determine the tibia ash and Ca and P content in the ash. Data was subjected to ANOVA and linear regression analysis. In broilers fed the adjCa:aP diets, the maximum WG, weight of tibia ash, and weight of P in tibia ash (P