A digestibility assay was carried out to determine the apparent metabolizable energy values (AMEn), dry matter digestibility coefficients (DMDC), the excretion and apparent retention coefficient of phosphorus (P), nitrogen (N), calcium (Ca), potassium (K), copper (Cu) and zinc (Zn), using 250 Cobb male broiler chickens receiving the treatments distributed in a factorial schedule 3 <FONT FACE=Symbol>´</FONT> 3 + 1 (available phosphorus level - 0.25; 0.34 and 0.45% and crude protein level [CP]- 15.0; 17.0 and 19.0% and a control diet, with normal nutritional levels), with five replicates of five birds each. In the diets with reduced levels of available phosphorus (aP), 500 FTU of phytase were added and calcium requirement was reduced in 17%. Except for control treatment, all the diets were formulated on digestible amino acids basis. The energetic values of the diets with 15.0 and 17.0% CP, independently of the aP levels used or the phytase supplementation, presented higher AMEn that the control diet possibility regarding to supplemental amino acids addition. The DMDC of the diets with reduced CP levels and different levels of aP were higher than the control diet. The CP reduction in the diet associated to lower aP levels and phytase enzyme supplementation allowed to reduce the minerals excretion, which showed better retention coefficients, except for Zinc that presented lower retention coefficient than the the control diet. However, all minerals excretion, as relatively compared to the control diet, was minimized when lower levels of CP and aP was used in the diet, supplemented with phytase. The manipulation of the protein and phosphorus levels in diets supplemented with amino acids and phytase could reduce mainly the excretion of nitrogen, P and Cu, minimizing the environment pollution caused by these elements.
available phosphorus; digestible amino acids; environmental pollution; enzyme; ideal protein
