SOYBEANS TRANSFORMED WITH A FUNGAL PHYTASE GENE IMPROVE PHOSPHORUS AVAILABILITY FOR BROILERS

Male broilers (n = 416) were used to compare the efficacy of providing dietary phytase either as a commercial supplement or as a recombinant protein in transformed soybean. From 7 to 21 d of age, broilers were fed a basal diet containing 0.20% nonphytate P (nP) with additional su pplementation by fungal phytase as Natuphos(R) or as raw transformed s oybeans expressing recombinant phytase at 400, 800, or 1,200 U/kg. For comparison, broilers were also fed the basal diet containing 0.08, 0. 16, or 0.24 added nP. The basal diet was fed as the negative control. Diets were consumed ad libitum as a mash. All excreta were collected f rom each pen from 18 through 20 d of age, and the birds were killed at 21 d of age. Supplementing the basal diet with nP linearly increased body weight gain, feed efficiency, feed intake, toe ash weight and per centage, and tibia shear force and energy. Phosphorus digestibility de ceased Linearly as nP level increased, but P excretion increased. Diet ary phytase linearly increased growth rate, feed intake, toe ash weigh t and percentage, tibia shear force and energy, and P digestibility, w hereas excretion was decreased. Except for P digestibility, there was no difference in efficacy of responses for performance, bone mineraliz ation, and P excretion bet between the two sources of phytase. It arre ars from this study that phytase can improve growth performance of bro ilers fed low nP diets when provided either as a commercial supplement or in the form of transformed seeds.