Effect of Calcium and Phosphorus on Energy Utilization by Chicks

The effect of calcium and phosphorus on energy utilization by mixed sex broilers was investigated. The calcium and phosphorus deficient basal diet was composed primarily of corn and soybean meal and contained chromic oxide as an indicating substance. The test diets were fed to three replicates of 10 chicks each. Two groups of chicks were fed diets containing either 0.3 or 0.5% non-phytate phosphorus and 1% calcium during the two-week preliminary period. Each group was then subdivided and each subgroup fed either the low phosphorus or the phosphorus adequate diet during a two-week test period. The level of non-phytate phosphorus fed during the preliminary period had no effect on subsequent energy content of the diet. In the second experiment chicks were reared for 10 days and then fed the test diets, which contained 0.2, 0.3, 0.4 or 0.5% non-phytate phosphorus, for 11 days. Each non-phytate phosphorus level was fed with either 1% calcium or at a 2:1 calcium: non-phytate phosphorus ratio. The energy content was reduced (P <0.05) only in those diets sufficiently deficient in non-phytate phosphorus to cause growth depression. The energy content was not reduced in diets containing adequate or borderline adequate levels of non-phytate phosphorus.