Efeitos de diferentes níveis de fitase e densidades energéticas em dietas de frangos de corte sobre o desempenho e composição da tíbia, na fase de 28 a 35 dias de idade

Abstract

Phytase is an enzyme able of eliminating the antinutritional properties of phytate by hydrolyzing and unfolding myoinusitolfophosphate and releasing phosphorus to be absorbed, improving nutrient metabolism and reducing the excretion of phosphorus, nitrogen and other nutrients into the environment. However, the operational fragility of this enzyme under extreme conditions of pH and temperature are the main limitations of phytase use in animal feed. In this work, 576 male broilers from the Cobb500 strain were housed in metabolic cages. Feed and water were supplied ad libitum. The diets contained increasing levels of apparent metabolizable energy corrected for nitrogen balance - AMEn (2950, 3050, 3150 and 3250 kcal/kg) and different levels of phytase (control, 500 and 1000 FTU/kg phytase) distributed in randomized blocks design, with 12 treatments, 8 replicates of 6 birds each. For the performance data, live weight, feed intake, weight gain and feed conversion were evaluated. For the physical characteristics and mineral deposition of the tibia, strength, area, length, dry matter, calcium, phosphorus, magnesium, zinc and bone ash were evaluated. A diet with 500 FTU/kg of phytase and an energy level of 3150 kcal AMEn/kg presented the best performance of broiler chickens. Phytase supplementation at levels of 500 and 1000 FTU/kg negatively influenced calcium, phosphorus, dry matter and ash deposition, as well as strength and area variables of broiler chickens. There was no difference in the bone length variables and in the magnesium and zinc content levels present in the tibia.