Dietary requirements of available phosphorus in growing broiler chickens at a constant calcium:available phosphorus ratio

Four experiments were conducted to study the requirements of available phosphorus (aP) for commercial male broilers of 1-10 day of age (exp.1), 11-21 days of age (exp. 2), 22-33 day of age (exp. 3) and 34-46 days of age (exp. 4), at a constant calcium:aP ratio. A complete randomized design was used in each experiment. The experimental diets were fed ad libitum to 8 replicate groups of ten broilers in each. The increments in the levels of aP ranged from 2.0 to 5.5 g/kg (exp. 1), 1.9 to 5.4 g/kg (exp. 2), 1.8 to 5.3 g/kg (exp. 3) and 1.7 to 5.2 g/kg (exp. 4), in 0.7 g/kg. The parameters evaluated were body weight gain, feed intake, feed conversion ratio and bone parameters. The level of aP in the diet influenced the performance of broilers of 1-10 and 11-21 days of age, but did not affect the performance of broilers at 22-33 and 34-46 days of age. Feed intake was not affected. The requirements of aP and Ca for male broilers from 1-10, 11-21, 22-33 and 34-46 days of age are 4.82 and 9.64 g/kg, 4.10 and 8.20 g/kg, 3.95 and 7.90 g/kg and 3.19 g.kg and 6.38 g/kg, respectively. The results indicate that low levels aP were required because the requirements of the mineral reduced as birds aged. Provided there is no excess of dietary levels of Ca, using a Ca:aP ratio of 2:1 may reduce the dietary levels of aP.