Effects of different totals and ratios of dietary calcium and phosphorus on the performance and incidence of leg abnormalities in male broiler chickens derived from normal and dwarf maternal genotypes

A factorial experiment, with day-old Hubbard male broiler chicks (702 each from Normal and Dwarf maternal genotypes), assessed the effects of three levels of total calcium (Ca) and available phosphorus (aP) at three different ratios (Ca:aP) during the starter (0–21 d) and finisher (22–40 d) periods. General performance was assessed as well as tibia characteristics (strength, ash, Ca, P), serum parameters (akaline phosphatase, Ca, P, Na, K, Cl) and leg abnormalities (tibial dyschondroplasia (TD), twisted legs (TL) and erosion of femoral head (EFH)). Nine starter and nine finisher diets were matched with percentages of Ca and aP ranging from 0.95 to 1.45 and from 0.41 to 0.73 for the starters and from 1.00 to 1.43 and from 0.31 to 0.51 for finishers, respectively. Increasing the total Ca + aP to 2.00 and 1.81 and the Ca:aP ratio to 2.65 and 3.55 for starter and finisher, respectively, reduced (P