A trial was conducted to evaluate the effects of exogenous enzymes added to corn-soy diets with different nutritional levels. Four hundred and eight day-old COBB 500 male chicks were distributed in a randomly factorial experiment (2 x 2) with diets having two nutritional densities (standard and low), with or without a pool of enzymes (50g/ton of Rovábio®), six replicates of 20 birds each were randomly distributed in 1.5 x 1.5m floor pens. Nutritional density of the standard diet was: 22,00/3000; 19,80/3100 and 17,82/3200 of crude protein (%CP)/ Metabolizable energy (Kcal kg-1), respectively in the initial, grower and finisher phases. The low density diets had 2% less CP, lysine and methionine+cystine, and 65kcal of ME kg-1 of feed. Feed comsumption, body weight, feed conversion and index of bio economical feed efficiency were analized. Results showed there was no difference for the interaction between nutritional densities and the pool of enzymes in the initial phase. However a significative interaction for feed consumption and body weigh between standard and low density diets. The low density diets added with enzymes had higher body weight gain compared to the one without enzymes. Feed comsumption and body weight gain were higher for standard diets without enzymes compared to low density with or without enzymes, even though feed conversion was not significantly different among them. In conclusion the addition of the multienzymatic complex improves the performance of the birds fed diets of low density. However, they had lower performance than those fed standard diets, regardless the use of enzymes. Cost of production of broilers receiving diets with low density supplemented with enzymes was lower than those with standard diets, with the formulation cost used.
bioeconomical analysis; enzymes; nutritional density
