Abstract Phytate-bound phosphorus (P) in plant-based feed ingredients limits mineral availability in swine diets, often requiring supplemental inorganic P to meet nursery pig requirements. Exogenous microbial phytase can increase P release from phytate, thereby improving P utilization and decreasing P excretion. The present study evaluated the effects of graded levels of a novel phytase on growth performance, apparent total tract digestibility (ATTD) of minerals, and bone mineralization in nursery pigs. A total of 150 Pietrain × (Landrace × Large White) pigs (8.25 ± 0.42 kg body weight (BW)) were used in a 35-d experiment. Pigs were blocked by sex and initial BW and housed 3 pigs/pen across 50 pens. Within block, pens were randomly assigned to one of five dietary treatments: a positive control (PC; 0.35% digestible P), a negative control without inorganic P (NC; 0.12% digestible P), or the NC supplemented with 250, 500, or 1,000 FTU/kg of a novel phytase. Diets were based on wheat–barley–rice by-product meal and soybean meal, pelleted, and offered ad libitum. Wheat and barley were pre-heated (85 °C) prior to feed manufacture to inactivate endogenous phytase. Titanium dioxide (0.4%) was included as an indigestible marker. During the final week, fecal samples were collected from each pen, freeze-dried, and analyzed for crude protein (CP) and P to determine ATTD. One pig per pen was euthanized on d 35 to collect metacarpals (III and IV) for bone weight and ash analysis. Data were analyzed using the GLM procedure of SAS, and means were separated using Tukey’s test. Significance was observed when P ≤ 0.05. Pen served as the experimental unit. Feed efficiency and average daily gain (ADG) were reduced (P 0.001) in NC compared with the PC. Supplementation of phytase at any inclusion level restored ADG and feed efficiency to values comparable with the PC. The ATTD of CP of pigs supplemented the 500 FTU/kg diet exceeded the PC, with all remaining treatments intermediate (P = 0.047). The ATTD of P increased in a dose-dependent matter with phytase supplementation, matching the PC at 250 FTU/kg and exceeding it by 15% at 1,000 FTU/kg (P 0.001). Bone weight was reduced in pigs fed the NC, and phytase supplementation restored to levels comparable with the PC (P ≤ 0.003). Bone ash percentage followed the same pattern, increasing from NC (10.85%) to the highest phytase inclusion (16.21%; P 0.001), demonstrating improved bone mineralization with increasing phytase dose. Overall, the novel phytase improved growth performance and mineral utilization in nursery pigs fed diets limited in inorganic P. Higher phytase activity (1,000 FTU/kg) produced the greatest improvements in ATTD of P and bone mineralization, suggesting potential to reduce inorganic P supplementation and P excretion while maintaining productive performance
Cordero et al. (Wed,) studied this question.