Amino acid reduction in broiler diets supplemented with phytase and elaborated according to different nutritional plans

the need for suitable diets in chickens, considering the ideal protein concept associated with phytase, is important in order to improve the productivity of birds. the aim of this study was to assess the need for the correction of amino acid levels in the diets of broilers, by using different combinations of crude protein (cp) supplemented with phytase. for performance, eight days old cobb 875 broiler chicks, with initial body weights of 155 ± 1.4g were used. the birds were distributed in a completely randomised design with seven treatments (nutritional plans) and five replicates of 25 birds. for the metabolism trial, 300 birds were selected which were also distributed using the same design, but with five, four and three birds per experimental stage: 8-21 days, 22-35 days and 36- 42 days. the nutritional plans consisted of different combinations of cp in diets with reduced calcium and phosphorus, supplemented with phytase and amino acids. the reduction of amino acids in diets with reduced levels of cp resulted in an increased intake, feed conversion and abdominal fat level, and decreased the yield of thigh + drumstick. the inclusion of phytase reduced the excretion of calcium and phosphorus, but increased nitrogen excretion when the cp was not reduced. as a result, this study concluded that the reduction of amino acids to 3.5%, supplemented with phytase and prepared according to a nutritional plan does not improve the performance and carcass characteristics of broilers, although it may reduce the emission of polluting elements by excreta.