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Effect of levels of exogenous enzyme in feed for broiler chickens on performance, digestibility, morphometry of the GI tract, enzyme production, activity and gene expression of digestive enzymes


Two experiments will be conducted in FMVZ-USP, Pirassununga / SP, to determine the effects of the use of exogenous alpha-amylase and protease in the diets of male Cobb broilers from 1 to 42 days of age on performance, digestibility, enzymatic activity of trypsin, alpha-amylase and lipase, and gene expression of endogenous alpha-amylase and trypsin. In each experiment 18 birds will be housed in each of the 32 replicates, totaling 576 birds per experiment. The diets are based on corn and soybean meal, and treatments will follow the requirements according to Rostagno et al. (2005). In experiment I will be used four levels of alpha-amylase added to the diet and in experiment II will be used four levels of protease. The levels, in both experiments, will be based on the manufacturer's recommendation to this enzyme as 100%. The design is completely randomized with four treatments and eight replicates for both experiments, four diets: T1 - 0% enzyme, T2 - 50% enzyme, T3 - 100% of enzyme T4 - 150% enzyme. In both experiments will be evaluated the performance (weight gain, feed conversion, carcass yield and viability) and proceeded to economic evaluation. For the metabolism trial, by experiment, will be used 288 day-old chicks Cobb males, bred in metabolic cages until 42 days of age, who underwent the same treatments as experimental performance. The total collection will be used in two phases: from 17 to 21 days and from 38 to 42 days old. At 21 and 42 days will be collected in the pancreas of two birds per cage for the subsequent analysis of enzyme activity and gene expression of alpha-amylase and trypsin. Results will be analyzed with the Statistical Analysis System (SAS,1998), after the verification of the normality of residuals by the Shapiro-Wilk test (Proc Univariate) the polinomial regression will be performed. (AU)

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