Effects of phytase transgenic corn on growth performance and calcium and phosphorus utilization in broilers

The goal of this study was to determine the effects of phytase transgenic corn (PTC) in low phosphorus (P) corn-soybean meal diets on growth performance, and P and calcium (Ca) utilization by broilers. Six hundred and forty 1-day-old male broiler chicks were randomly divided into four groups, with eight replicates of 20 birds in each group, and fed 42 days. Four treatments consisted of a positive control (PC), a negative control (NC), a PTC group and an exogenous phytase (EP) group. The PC group was fed with basal diet containing adequate amount of P. The NC group had 50% of the dicalcium phosphate supplement in the basal diet. The PTC group had the same inorganic P as the NC diet, but was substituted PTC for normal corn, so that the diet contained 500 phytase units (FTU) per kg of diet. The EP group was fed a diet identical to the NC diet but supplemented with 500 FTU of EP/kg of diet. The experiment showed that: there were no significant differences between the PTC and the PC groups, although a more favorable feed/gain occurred from the PTC group. The average daily feed intake and the average daily gain in the PC, PTC and EP groups were higher than those in the NC group (P<0.05). The Ca and P contents of tibia ash and serum in the PTC group were similar to those in the PC group, except for a higher tibia P percentage in the PC group at day 21 (P<0.05). These values were slightly higher than those in the EP group, except for a lower content of tibia P of the PTC group on day 42; the apparent retention of total phosphorus of the PTC and EP groups from day 17 to 21 was higher than that in the PC group (P<0.05). In conclusion, PTC as a source of phytase can replace the EP in broiler diets, especially in the starter phase of broiler chicks. The use of PTC could reduce the inclusion of inorganic P, improve the retention rate of P, and reduce pollution of the environment by farm animals without affecting the growth performance of broilers.