Replacement of added trace minerals (zinc, copper, iron, and manganese) by a consensus bacterial 6-phytase variant in weaned pigs fed an all-vegetable diet

This experiment evaluated whether a consensus bacterial 6-phytase variant (PhyG) could totally replace the effect of added trace minerals (TM; Zn, Cu, Fe, and Mn) in an all-vegetable diet, in weaned pigs. A total of 144 DanBred × Pietrain weaned pigs (28 d of age, body weight 7.0 ± 0.44 kg) were assigned to floor pens (12 pens/treatment; 4 pigs/pen; 2 females, 2 castrated males). Diets were based on corn, wheat, barley and soybean meal, fed in 2 phases (starter I: day 1 to 14 and starter II: day 14 to 42) and provided ad libitum. Treatment diets comprised: 1) a negative control (NC1) diet formulated without added TM but otherwise nutritionally adequate; 2) a positive control (PC), comprising the NC1 supplemented with Zn, Cu, Fe, and Mn at 120, 80, 96, and 80 mg/kg, respectively, and; 3) the NC1 reduced in Ca and digestible P to account for the expected contribution of PhyG which was supplemented at 1,500 phytase units (FTU)/kg during starter I and 1,000 FTU/kg during starter II (NC2+PhyG). Growth performance was monitored over 42 d, and on day 42 blood, liver and femur bone samples were collected from 1 pig/pen for TM analysis. Data were analyzed by one-way ANOVA and treatment means were separated by Tukey's HSD test. Pen was the experimental unit. Final (day 42) body weight and overall average daily gain were reduced in NC1 compared with PC (-2.04 kg/pig and -48.8 g/pig/day, respectively; P < 0.05) and increased (P < 0.05) in NC2+PhyG compared with NC, to levels not different from the PC. Zinc in bone ash at day 42 was increased in the PC compared with NC1 (+25.7 mg/kg, respectively; P < 0.05) and further increased in NC2+PhyG vs. NC1 or PC (+49.9 and +24.2 mg/kg, respectively), whereas Fe in bone was increased in NC2+PhyG vs PC (+35.4 mg/kg; P < 0.05). The results indicate that PhyG supplementation at the applied doses maintained growth performance and tissue TM concentrations at levels comparable to those achieved by the TM-supplemented diet. The findings suggest that the enzyme could replace supplemental Zn and may also support a reduction in the level of supplemental Cu, Fe and Mn in piglet diets, depending on the content of these TM in the basal diet.