A factorial design experiment was conducted to test the effects of two methods of feed formulation, i.e. based on total (TAA) vs digestible (DAA) amino acids and a multi-enzyme preparation in diets with different sources of plant protein, and two energy levels on carcass parameters, especially breast (BM) and breast + leg muscles (VM) content, of two broiler strains (ISA 215 and Ross 308). Treatment diets were fed from 22 to 42 days of age. Overall, Ross birds deposited relatively more BM and VM muscles than ISA broilers. The diet with a lower energy level decreased BM yield in the faster-growing ISA strain. Formulating diets on the basis of DAA vs TAA yielded higher BM and VM percentages in both strains. Enzyme supplementation had a positive effect on BM (Ross) and VM (ISA) yields. In both genotypes feed formulation based on DAAs appeared more effective in improving carcass meatiness than enzyme supplementation.