Bioavailable Phosphorus Releasing Efficacy of Escherichia coli and Aspergillus Derived Phytases in Broiler Chick Diet

A broiler chick trial investigated the phosphorus (P) releasing efficacy of phytases derived from Eschericia coli (ECP) and Aspergillus niger, a fungus (FP) when added to a corn-soybean meal diet with no supplemental inorganic P (iP). Four graded levels of iP were added to the basal diet to construct a standard curve from which available P-release could be calculated for the phytase treatment. In all cases, phytase supplementation levels were based on an assessment of phytase premix activity. One phytase unit (FTU) is defined as the amount of enzyme required to release 1 mu mol of iP per min from 5.1 mM sodium phytate at 37 degrees C and pH 5.5. Weight gain, weight and percentage of tibia bone ash increased (P<0.05) with an increase in iP supplementation of the basal diet. ECP derived phytase released two to three times more P (P<0.05) when added at 130-260 FTU/kg compared to FP added at 250-500 FTU/kg. At 130 FTU/kg, ECP released more P (P<0.05) than FP added at 1000 FTU/kg. Tibia weight and percentage of tibia ash responded (P<0.05) to graded levels of ECP up to 260 FTU/kg, however, 130 FTU/kg was as effective as 260 FTU/kg. Weight gain and gain:feed ratio were higher (P<0.05) for chicks fed FP added at 250 and 1000 FTU/kg than for those fed ECP at 65 and 260 FTU/kg. However, chicks fed ECP at 130 FTU/kg had similar gain and gain:feed ratio as those fed FP at 1000 FTU/kg. Tibia ash (percentage and milligrams) was higher (P<0.05) for chicks fed ECP added at 130 and 260 FTU/kg than those fed FP at 250, 500, and 1000 FTU/kg, respectively. This trial revealed a significant advantage of the E. coli derived phytase over the Aspergillus fungal derived phytase in releasing phytate bound P in broiler chick diet.