Abstract
In this experiment the effects of total dietary phosphorus (TP) and calcium (Ca) on growth, feed conversion ratio, breast muscle yield, serum phosphorus (P), and bone measurements were examined. From 3 to 6 weeks, four levels of TP (4.5, 5.0, 5.5, and 6.0g kg
−1
) and two levels of Ca (7.0 and 9.0g kg
−1
) provided eight treatments. From 6 to 7 weeks, diets with two levels of TP (4.5 and 5.5g kg
−1
) and three levels of Ca (6.0, 7.0, and 8.0g kg
−1
) were used. Diets with 4.5g kg
−1
TP did not contain a source of inorganic P. Interactions were detected for feed intake, weight gain, and serum P at 6 weeks. Birds fed 5.0, 5.5, and 6.0g kg
−1
TP with 9.0g kg
−1
Ca consumed more feed and gained more weight as compared to the other groups. Feed conversion of birds fed the 9.0g kg
−1
Ca diet was lower than those fed diets with 7.0g kg
−1
Ca. Serum P was increased (P < 0.05) at the lowest level of TP when dietary Ca was lowered. Lowering the Ca level, in general, raised (P < 0.05) serum P. Ash was a function of the amounts of TP and Ca in the diets; Ca and P contents of the bones were not affected by the dietary treatments (P > 0.05). Interactions or main effects for TP and Ca were not detected for body weight gain, feed consumption, feed conversion, breast muscle yield, serum P and bone measurements at 7 weeks of age. Our findings demonstrate that from 3 to 6 weeks of age, dietary total P can be lowered to 5.0-5.5 g kg
−1
while the inorganic P source can be removed in the finisher diets without loss in performance or bone integrity.