The trial was carried out to evaluate the performance and mineral levels in the litter of broilers from 1 to 21 days old, fed diets with low-crude protein (CP) and low available phosphorus (AP) supplemented with synthetic amino acids and phytase. A total of 1-d 1.500 male Cobb broiler chickens averaging initial weight of 42.5 g was allotted to floor pens as a complete randomized blocks design, with 3 x 3 + 1 factorial arrangement, being three levels of CP (15, 17 and 19%) and three levels of AP (0.25, 0.34, and 0.45%) and a control with expected nutritional requirements, according to Brazilian researchers recommendations, with six replicates of 25 broilers. In the diets with 0.25 and 0.34% of AP 500 FTU of phytase were added and the Ca levels decreased by 17%. Weight gain of the broilers fed diets with 15% of CP supplemented with synthetic amino acids in the three levels of AP + phytase and in the diet with 17% CP and 0,25% AP + phytase was lower than those fed the control diet. The feed intake of the broilers feeding low CP (15% ad 17%) and low AP (0,25%) + phytase was lower than those fed the control diet.. However, it was not observed any significant differences for feed conversion. The broilers fed diets with 17% and 19% of CP, with low AP (0.34%), supplemented with synthetic amino acids and phytase showed performance similar to those obtained with control diet. The CP and AP levels affected P, Ca, Zn, Cu ad K contents in litter, but did not affect N content. The mineral levels in the litter decreased when broilers were fed diet containing 17% CP and 0.34% of AP, supplemented with synthetic amino acids and phytase, except for the N content. The CP and AP levels may be reduced by 17 and 0,34% respectively, in the broilers diets in the initial phase (1 to 21 days old), with no effect on performance, since the diets are supplemented with synthetic amino acids and phytase. These levels of CP and AP resulted in decreasing environmental impact, due to the decreasing P, Ca, Cu, and Zn contents in the litter.
amino acids; environmental impact; enzyme; ideal protein
