Effects of microbial phytase supplementation to low phosphorus diets on the performance and utilization of nutrients in broiler chickens

A five wk feeding experiment was conducted with day-old one thousand broiler chicks (Arbor Acres) to determine the effects of microbial phytase (Natuphos(R)) supplemented to low nonphytate P (NPP) corn-soy diets. Five pens of 50 mixed sex birds each were randomly assigned to each of the four dietary treatments: T1, control diet containing normal NPP level; T2, T1-0.1% NPP+600 U of phytase/kg diet; T3, T1- 0.2% NPP-I 600 U of phyease/kg diet; and T4, T1-0.3% NPP+600 U of phytase/kg diet. T1, T2, and T3 showed similar growth rate, Feed intake, and feed efficiency, indicating that NPP level in broiler diets could be reduced by approximately 0.2% by the microbial phytase supplementation. But T4 showed significantly (p<0.05) lower weight gain than others. The phyrase supplementation improved P availability resulting in low P excretion. Weight and girth of metatafsal bone were increased by phytase supplementation at low NPP diet treatments but ash contents were not significantly different. It can be concluded that NPP level of corn-soy broiler diets can be safely lowered by approximately 0.2% by supplementing 600 U of microbial phytase/kg diet. With the adjusted level of NPP and phytase supplementation, P excretion could be reduced by 50%.