A total of 297 pigs (DNA 241 × 600; initially 8.64 ± 0.181 kg) were used in a 21-d trial to determine the efficacy of a novel phytase derived from Citrobacter braakii and expressed in Aspergillis oryzae (HiPhorius; DSM Nutritional Products, Animal Nutrition & Health, Parsippany, NJ) on pig growth and bone mineralization indicators. Pens of pigs were assigned to 1 of 5 dietary treatments in a randomized complete block design with 5 pigs per pen and 12 pens per treatment. The trial was initiated 14-d after weaning. The first three treatments were formulated to contain 0.09% aP; without added phytase (control), or the control diet with 600 or 1,000 FYT/kg of added phytase (considering a release of 0.15% or 0.18% aP, respectively). The remaining two treatments were formulated to contain 0.27% aP, one without added phytase and the other with 1,000 FYT/kg. From days 0 to 21, pigs fed increasing phytase in diets containing 0.09% aP had increased (linear, P ≤ 0.002) ADG, ADFI, and G:F, but added phytase in the 0.27% aP diet did not impact growth performance. Increasing phytase in diets containing 0.09% aP increased percentage bone ash in metacarpals and 10th ribs (linear, P < 0.001; quadratic, P = 0.004, respectively), and increased grams of Ca and P in metacarpals, 10th ribs, and fibulas (linear, P ≤ 0.027). Adding 1,000 FYT/kg phytase in diets with 0.27% aP increased (P ≤ 0.05) percentage bone ash and grams of Ca and P in fibulas and 10th ribs compared with pigs fed 0.27% aP without added phytase. Increasing aP from 0.09% to 0.27% in diets without added phytase increased (P < 0.001) ADG, ADFI, and G:F. Increasing aP from 0.09% to 0.27% in diets without added phytase increased bone density (P ≤ 0.002) in fibulas and metacarpals, percentage bone ash in all bones (P ≤ 0.074), and increased (P < 0.05) grams of Ca and P in fibulas and 10th ribs. Pigs fed diets containing 0.09 or 0.27% aP, both with 1,000 FYT added phytase, had increased (P < 0.05) bone density in fibulas and metacarpals, percentage bone ash in all bones, and increased grams of Ca and P in fibulas and 10th ribs. For growth performance (average of ADG and G:F), aP release was calculated to be 0.170% for 600 FYT/kg and 0.206% for 1,000 FYT/kg. For the average of all bone measurements (average of 3 bones for both bone density and percentage bone ash), aP release was calculated to be 0.120% and 0.125% for 600 and 1,000 FYT/kg, respectively.
Keywords: bone ash; bone density; growth; nursery pigs; phosphorus; phytase.
Approximately 60% to 80% of phosphorus (P) in feedstuffs of plant origin is stored in the form of phytic acid. Phytase is an enzyme used in swine diets to improve the digestibility of phytate-bound P. As phytase sources continue to advance, their efficacy must be evaluated. In this study, nursery pigs (9 kg) were used to determine the efficacy of a novel phytase derived from Citrobacter braakii and expressed in Aspergillis oryzae in releasing phytate-bound P. Increasing phytase added to diets deficient in aP improved growth performance and bone mineralization. Adding phytase to a diet already adequate in aP did not affect growth performance, but improved bone mineralization indicators. Available P release attributed to phytase was estimated using growth performance and found to be 0.170% for 600 FYT/kg and 0.206% for 1,000 FYT/kg. For the average of all bone measures, the estimated aP release was 0.120% for 600 FYT/kg and 0.125% for 1,000 FYT/kg. Results of this study indicate an increasing release of phytate-bound P with increasing additions of the novel phytase tested in nursery diets and confirm that additional P is needed for bone development compared to growth.
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