Avaliação da matriz nutriconal de uma 6-fitase em dietas de frangos de corte

Abstract

The objective was to validate the nutritional matrix of a dietary 6-phytase supplementation at different levels on performance, carcass and bone characteristics and nutrient digestibility in broilers. In the experiment I were used 1980 one day male chicks, Cobb 500, distributed in randomized design (RD) in nine treatments with 10 replicates of 22 birds in each, in the floor system. The treatments consisted of positive control (PC) and negatives controls (NC). The PC was adequate on levels of nutrients, four NC with reduction values on metabolizable energy, crude protein, available phosphorus, calcium, sodium and amino acids according to the enzyme matrix (NC 250, NC 500, NC 750, NC 1000) and four NC with phytase supplementation according at their respective levels (NC + 250, NC + 500, NC + 750, NC + 1000). Performance was analyzed by feed intake (FI), weight gain (WG), feed conversion ratio (FCR) and productive efficiency index (PEI). For the carcass characteristics, carcass yields (CY), breasts yields (BY) and percentage of abdominal fat (AF) were analyzed. The bone characteristics analyzed were Seedor index (SI), breaking resistance (BR), percentage of mineral matter (MM %) and weight of mineral matter by tibia (MM (g/ tibia)). In the experiment II, 96 male oneday chicks, Ross AP 95, were distributed in RD in eight treatments with six replicates and two animals each, housed in metabolic cages. The treatments were similar to experiment I, except PC. The nutrient digestibility was evaluated in two phases of total excreta collection, at 18º to 21º and 39º to 42º days of age. The dry matter digestibility coefficient (DMDC), crude protein (CPDC), calcium (CaDC) and total phosphorus (PDC) were analyzed. The data were submitted to ANOVA and, when significant, the SNK test was applied for experiment I and the Tukey test for experiment II at 5%. The PC resulted better values (P <0.05) for WG, FCR and PEI. The FI of the PC birds and the treatments with enzyme supplementation and the NC 250 were higher (P <0.05) than others NC. The birds in the treatments supplemented with phytase resulted higher performance in relation to their NC starting up the level of 500 FTU / kg of the diet. For CY the NC + 250 shows higher results (P < 0,05) than NC 750 and NC 1000. For BR and SI the treatments supplemented with phytase, the NC 250 and the PC shows betters results (P <0.05) at 21 and 42 days. There was an increase (P <0.05) in the CaDC and PDC at 21 days when phytase was used in the diets, regardless of the level used. It was evidenced that the phytase nutritional matrix considered was not satisfactory for performance, but for the carcass and bone characteristics the enzyme was effective. The values of CaDC and PDC improved with the enzyme supplementation in the initial period.