The supplementation of low-P diets with microbial 6-phytase expressed in Aspergillus oryzae increases P and Ca digestibility in growing pigs

A trial was conducted to evaluate the dose response of a novel microbial 6-phytase expressed in Aspergillus oryzae (Ronozyme HiPhos; DSM Nutritional Products, Basel, Switzerland) in pigs. Forty- eight individually housed pigs (Landrace × Pietrain; 52 kg BW; 24 males and 24 females) were distributed among 6 experimental treatments consisting of a low-P diet (3.5 g P/kg; 1.1 g digestible P/kg), which was supplemented with 500, 1000, 2000, or 4000 units of phytase activity/kg, and a standard-P diet (4.5 g P/kg; 1.8 g digestible P/kg) that was supplemented with CaHPO 4 . After 17 d, fresh feces were sampled from all pigs and the apparent total tract digestibility of DM, OM, ash, P, and Ca was measured using TiO 2 as indigestible marker. Blood samples were also obtained from each pig and serum was analyzed for P and Ca concentrations. The nonsupplemented low-P diet increased Ca and reduced P blood serum concentrations (P < 0.05) relative to the standard-P diet (10.8 vs. 10.2 and 6.7 vs. 7.7 mg/dL, respectively). Phytase supplementation of the low-P diet reduced Ca (from 10.8 to 9.9 mg/dL; linear, P < 0.001) and increased P concentrations (from 6.7 to 8.0 mg/dL; linear and quadratic, P < 0.001) in serum and reduced P concentration in feces (from 13.7 to 7.6 g/kg DM; linear and quadratic, P < 0.001). Phytase improved the total tract digestibility of P (from 29.0 to 62.3%; linear and quadratic, P < 0.001 and P < 0.05), Ca (from 54.0 to 75.7%; quadratic, P < 0.01), and ash (from 46.2 to 57.7%; quadratic, P < 0.01). In conclusion, the microbial 6-phytase tested improves the apparent total tract digestibility of P in growing pigs and reduces P excretion in feces in a dose-dependent manner.