Effects of dietary phytase on performance and nutrient metabolism in chickens
Résumé
Abstract. 1. A broiler-growth study was conducted to compare the effect of different concentrations of an E. coli derived phytase on performance, apparent metabolisable energy (AME), nitrogen (N), amino acid and mineral metabolisability, sialic acid excretion and villus morphology when fed to broiler chickens. 2. Female Ross 308 broilers (480) were reared in floor pens from 0 to 28d age. All birds were fed a nutritionally complete starter (0 to 21d age), and grower (21 to 28d age) with the exception that they were low in P (28g/kg and 23g/kg available P, respectively). These maize-soy diets were supplemented with 0, 250, 500 or 2500 FTU/kg feed. 3. Between 21 and 28d age, two birds from each floor pen were selected, and each pair placed in one of thirty-two metabolism cages (2 birds per cage). Feed intake was recorded and excreta collected for the last two days of the feeding period, and AME, N, amino acid and mineral metabolisability coefficients and endogenous losses were determined following a total collection procedure. 4. Feed intake (P<0.001) and weight gain (P<0.05) improved in a linear manner in response to phytase dose, with an average improvement of approximately 11.7% and 13.5% respectively compared to chickens fed the low-P diet. Birds fed diets with 2500 FTU diet weighed 6.6% more (P<0.05) and had a 2.4% higher FCE (P<0.05) compared with those fed diets containing 500 FTU. 5. Enzyme supplementation increased the intake of AME and metabolisable N by 10.3% (P<0.001) and 3.9% (P<0.05), respectively principally through improvements in intake. Birds fed enzyme supplemented diets also improved their intake of metabolisable amino acids and P by approximately 14% (P<0.05) and 12.4% (P<0.05) respectively compared to birds fed the control diet. Enzyme supplementation did not affect ileal villus morphometry of the birds.
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