115 Functionality of a novel consensus bacterial 6-phytase variant on ileal phytate degradation in weaned piglets fed diets without inorganic phosphate

Abstract

Abstract Microbial phytases are used in animal feed to hydrolyze phytic acid (myo-inositol hexakisphosphate, IP6) and phytate (salt of phytic acid), to improve phosphorus (P) bioavailability. This study evaluated the efficacy of a novel consensus bacterial 6-phytase variant (PhyG) on ileal IP6 degradation in piglets. A positive control diet was formulated based on corn and soybean meal with adequate digestible P (2.9g/kg) and calcium (Ca, 7.0g/kg). A negative control (NC) diet was formulated without inorganic P (1.1 g digestible P/kg), reduced in Ca (5.0 g/kg) with analyzed phytate P of 2.6g/kg. This diet was supplemented with PhyG at 250, 500 and 1,000 FTU/kg. A total of 90 crossed Pietrain x (large White x Landrace) 21-d-old piglets were fed adaptation diets until 42 d old and then assigned to pens (2 pigs/pen and 9 pens/treatment) in a completely randomized block design. Piglets were fed mash diets ad libitum for 28 d, at the end of the study 1 piglet/pen was euthanized for collecting ileal digesta samples for determination of IP6 digestibility, using TiO2 as a marker. Data was analyzed by one-way ANOVA using JMP 14.0 with treatment comparison by Tukey test and dose response by curve fitting. The ileal IP6 content was reduced with increasing phytase dose in a dose dependent manner (Plinear < 0.0001; Pexponential = 0.08). Similarly, the ileal IP6 digestibility increased exponentially (P < 0.05) with increasing phytase dose (49.1% for NC and 89.3% for PhyG at 1,000 FTU/kg). Improved ileal IP6 digestibility is closely related to improved bone ash, body weight gain and feed conversion ratio (R2 > 0.91). The in vitro IP6 degradation profile supports these in vivo observations. The results demonstrated that the novel consensus phytase variant is highly efficient in hydrolyzing phytate and increasing the bio-availability of phytate bound P in piglets fed diets without inorganic phosphate.