Effect of microbial phytase on broilers fed barley-based diets in the presence or not of endogenous phytase

Abstract

Three hundred and eighty four male broilers of the Ross 308 strain were used to evaluate the effects of a microbial phytase on the improvement of performance, dietary energy and mineral retention in diets with or without endogenous barley phytase. The chicks were housed in 48 cages in Petersime battery brooders and cages were allocated to eight replicates of six dietary treatments. Treatments were based on: two different concentrations of non-phytate P (NPP) (4.5 and 2.7 g/kg), use of untreated or autoclaved barley, and addition or not of 500 U/kg feed of microbial phytase to the P-deficient diets. Diets included 5 g titanium oxide (TiO 2)/kg as a digestibility tracer. The reduction of NPP in broiler diets produced a decrease of daily feed intake and water consumption and a reduction of animal growth that was overcome by the inclusion of phytase enzyme SP-1002 in these feeds. Similar broiler performance was obtained feeding the animals with diets containing 4.5 g NPP/kg or with diets containing only 2.7 g NPP/kg plus 500 U phytase enzyme SP1002/kg. The concentration of toe ash, a good indicator of phosphorus retention, varied according to the dietary content of phosphorus and the presence or not of microbial phytase enzyme. Plasma concentrations of phosphorus and calcium were also influenced by dietary P concentrations and the presence or not of exogenous phytase. The inclusion of phytase enzyme to diets with a low concentration of NPP increased the coefficient of phosphorus retention and reduced the presence of this element in broiler excreta by up to 45%, thus, indicating a favourable environmental effect. In general, no effects were observed due to the presence or not of endogenous barley phytase.