Efeitos da inclusão de diferentes níveis de fitase na alimentação de frangos de corte

Abstract

Three experiments were conducted to evaluate the effects of increasing levels of phytase in diets with reduced nutritional matrices or digestible amino acids, as well as to determine the bioavailability of phosphorus released by phytase on performance, bone mineralization, biochemical parameters, intestinal health, and carcass yield of broiler chickens. In the first experiment, seven treatments were evaluated in a completely randomized design, with eight replicates of 16 birds per experimental unit. Treatments included a basal control diet (meeting all nutritional requirements), a negative control diet with reductions of 0.15% calcium and phosphorus, 0.03% sodium, and 30 kcal kg⁻¹ of metabolizable energy, and five diets containing increasing phytase levels (500, 1000, 2000, 4000, and 8000 FTU/kg) added to the negative control. In the second experiment, seven treatments were evaluated in a completely randomized design, with six replicates of 16 birds per experimental unit. Treatments consisted of a diet deficient in available P, three levels of dicalcium phosphate supplementation (0.09%, 0.18%, and 0.27% available P), and three phytase supplementation levels (600, 1200, and 2400 FTU). In the third experiment, nine treatments were evaluated in a completely randomized design, with 10 replicates of 22 birds per experimental unit. Treatments included a positive control diet (minimum crude protein level), two negative controls (with reductions of 2% and 4% digestible amino acids, 0.15% calcium and phosphorus, and 15 kcal kg⁻¹ of metabolizable energy), and three phytase levels (500, 1000, and 2000 FTU/kg) applied to each negative control. Zootechnical performance and feed intake were recorded at 21 and 42 days in all three experiments. For intestinal histomorphometry, jejunal samples were collected at 21 and 42 days in the first experiment, and duodenal and jejunal samples at 21 and 43 days in the third experiment. Blood samples were collected at 21 and 42 days in the first experiment and at 35 days in the third, for analysis of biochemical parameters and enzymatic activity. Thigh samples were collected at 21 and 42 days in the first and second experiments to assess bone parameters. In the first experiment, a metabolism assay was carried out to evaluate the apparent digestibility of calcium, phosphorus, and metabolizable energy, and litter quality was analyzed at 40 days. In the third experiment, ileal content was collected at 21 days, while cecal content was collected at 21 and 35 days. Carcass yield was assessed at 42 and 43 days in the first and third experiments, respectively. In the first experiment, inclusion of up to 8000 FTU/kg of phytase maintained results similar to those of the positive control. In the second experiment, supplementation with up to 2400 FTU/kg increased the bioavailability of essential minerals, surpassing both deficient diets and diets supplemented with dicalcium phosphate, ensuring proper performance and bone development. In the third experiment, phytase improved performance and nutrient utilization in birds fed diets with reduced nutritional density, although doses above 1000 FTU/kg provided limited additional benefits.