64 Total Replacement of Inorganic Phosphorus by a Novel Consensus Bacterial 6-phytase Variant in Grower Pigs Fed Corn-soybean Meal-based Diets
Abstract The efficacy of a novel consensus bacterial 6-phytase variant (PhyG) to totally replace dietary inorganic phosphorus (Pi) was evaluated in grower pigs fed diets with reduced net energy (NE) and digestible amino acids (AA), using growth performance and total tract digestibility (ATTD) of nutrients as outcome measures. A total of 352 growing pigs (23.4 ± 1.3 kg) were randomized to 4 dietary treatments with 8 pigs/pen and 11 pens/treatment. Diets were corn, soybean meal, distiller’s dried grains with solubles and wheat middlings based, formulated by phase (Grower 1, 25 to 50 kg and Grower 2, 50 to 75 kg). The positive control (PC) diet provided adequate energy and nutrients. A negative control diet was formulated without Pi (0.12% STTD P) and reduced Ca (-0.12 to -0.13 percentage points), NE (-32 kcal/kg) and essential AA (-0.15 to 0.3 percentage points) vs. PC. The NC was supplemented with 500 or 1,000 FTU/kg of PhyG. Data were analyzed by analysis of variance and orthogonal polynomial were used for linear response to increasing PhyG. Nutrient reductions in the NC reduced (P < 0.05) average daily gain (ADG) during both phases and overall, increased (P < 0.05) feed conversion ratio (FCR) and tended to reduce (P < 0.1) feed intake during Grower 1 and overall, vs. PC. Supplementation of PhyG showed linear improvement (P < 0.05) in FCR during Grower 1 and ADG during Grower 2 and PhyG at 1,000 FTU/kg maintained a similar growth performance compared to PC. Addition of PhyG improved (P < 0.001) ATTD P and tended to improve ATTD of DE (P < 0.1) in linear manner. In conclusion, the novel consensus phytase can replace Pi and compensate for the reduction of Ca, NE and digestible AA in grower pig diets with equal performance compared to the nutrients adequate positive control.