Eficiência de fitase em dietas com baixo e alto teor de fósforo fítico para frangos de corte

Abstract

To evaluate the efficiency of phytase in diets with low and high phytic phosphorus (Pfit), depending on the inclusion or not of wheat bran, on performance, physical characteristics of the tibia, tissue and serum mineral deposition, the relative weight of organs, total and ileal digestibility coefficients and intestinal morphology, 384 broilers (males Cobb500 line) were housed in metabolic cages and assigned to four treatments in a 2x2 factorial arrangement in a randomized block design with eight replicates of 12 birds each . At 11 days of age broilers received the experimental diets, which consisted of T1 - low Pfit diet; T2 - low Pfit diet with phytase (500 FTU / kg); T3 - high Pfit diet and T4 – high Pfit diet with phytase (500 FTU / kg). The average feed intake, average body weight, weight gain and feed conversion were evaluated among 11 to 21 and 22 to 32 day of age. At 22 and 32 day of age two birds of each replicate were sacrificed and the tibia was collected for analysis of the physical characteristics and mineral deposition, and a portion of the pectoral muscle without skin and blood samples to evaluate the levels of calcium, phosphorus and sodium on tissue and serum, respectively. Also, gizzard, heart, liver, cecum, cloacal bursa were collected to determine the relative weight of these organs, the ileal content to quantify the ileal digestibility coefficient and a portion of the duodenum, jejunum and ileum to analyze the intestinal morphology. From 28 to 31 days the total excreta collection was carried out to quantify the total apparent digestibility coefficients. Data were subjected to analysis of variance in terms of the fixed effects of the diet and the phytase inclusion, as well as the interaction among the factors and the random effect of the block. An interaction for bone stiffness and serum calcium was observed. The inclusion of phytase in diets with low and high Pfit did not affect performance, endurance and bone flexibility, mineral deposition in the tibia and pectoral muscle, but increased bone stiffness at 22 days of age; at 32 days of age, a low Pfit diet provided a higher calcium content in the serum of the birds. A significant interaction among the apparent metabolizable energy corrected for nitrogen (AME) and total digestibility (CDAT) of calcium, phosphorus and sodium was observed, where the low Pfit diet with or without phytase presented the best results, except for sodium CDAT. The addition of phytase in low and high Pfit diets for broilers did not alter the relative weight of organs, intestinal morphology and the CDAI, but the low Pfit diet provided greater EMAn calcium and phosphorus CDAT.