Efficacies of phytase, phosphorolytic enzymes (phytase + acid phosphatase), an enzymic "cocktail" (phytase + acid phosphatase + pectinase + citric acid), a novel Aspergillus niger (fungal) mycelium (FM), and FM enriched in phytase and antioxidants were investigated in growing broilers (Days 1 to 21) fed wheat-based diets. Broilers were fed the following seven diets at 0.69% Ca: 1) a negative control diet, 0.17% nonphytate P (NPP); 2) Diet 1 + 750 phytase units/kg diet; 3) Diet 1 + 750 phytase units + 3,156 units acid phosphatase/kg diet; 4) Diet 1 + 750 phytase units + 3,156 acid phosphatase units + 1,900 units of pectinase/g diet + 3% citric acid; 5) Diet 1 + 4% FM; 6) Diet 1 + 4% FM + 1,300 phytase units + 2% ascorbic acid and 1% of glucose oxidase; and 7) a positive control diet (Diet 1 + 0.24% NPP from dicalcium phosphate). The dietary treatments were fed to four pen replicates of eight birds each. Prior to feed formulation, mycelium and antioxidants dosages were optimized on Diet 1 by an in vitro technique and an experimental design module of a statistical software package. Phytase addition increased BW gain (BWG), feed intake, and P retention. Subsequent addition of acid phosphatase resulted in further increases in BWG, feed intake, and toe ash and reduced digesta viscosity; however, neither P nor Ca retention were improved. Body weight gain and feed intakes superior to those found in chicks fed Diet 7 were observed in birds receiving the cocktail of enzymes (Diet 4) or FM. Chicken fed Diet 6 had the highest percentage of toe ash and retained 76 and 51% of P and Ca, respectively. Supplementation of wheat-based 0.17% NPP diets with FM increased bursa of Fabricius weights and reduced the intestinal surface covered by Peyer's patches.