PSIV-17 Effect of Phytase Supplementation on Growth Performance, Bone Mineralization, Metabolism, and Excretion of Calcium and Phosphorous on Fattening Pigs Fed a Diet Containing no Inorganic Phosphate
Authors: Verdu Marcal , Merriman Laura A , Guitart Xavier Soldevila , Balart Marta , Llovet Jaume Civis , Montull Raul Teixido , Comas Joan Grau , Becker Spenser , Parra Diego , Cordero Gustavo 
Published: October 2023

Abstract
Global concern about sustainability has led many countries to establish legislation to reduce phosphorus (P) pollution. Phytase application has evolved significantly in the last years, with greater dose rates leading to a greater reduction in inorganic P supplementation and decreased feeding costs. An experiment was conducted to determine the impact of 3 supplementary levels of phytase on pig growth performance, bone mineralization, and mineral excretion (P, Ca, and N) in corn/barley/wheat/SBM based diets containing no inorganic P. Crossbred [(Landrace x Large White) Duroc] pigs [n=137; initial body weight (BWi) = 16.8 ± 4.04 kg) were housed in 24 pens containing 5 or 6 pigs/pen) for 62-day trial. After a 21-day adaptation period, each pen was assigned one of three experimental treatments according to the dietary inclusion dose of the study phytase (Quantum Blue, AB Vista): 500, 800 and 1,500 FTU/kg feed. The feeding program was based on a single diet that was pelleted and formulated according to FEDNA (2013) recommendations. The basal diet was designed with a similar composition of ingredients and nutrients (2,450 kcal/kg net energy, 15.3% crude protein, and 0.23% phytic P) except for the levels of total P and calcium. Feed consumption (per pen) and individual BW of the animals were recorded on days 0, 21, 42, and 62 of the study. On day 62 of the study, pigs were euthanized. Feces and blood samples from 2 pigs per pen were collected on days 0, 42, and 62 of the study. Data were analyzed using a mixed effects model with repeated measures. The statistical model included experimental treatment, initial BW block, study day and their interaction as fixed effects, and pen as a random effect of the fit model platform in JMP 16.0. The addition of 1,500 FTU/kg phytase tended to improve (P = 0.10) feed conversion by 4.3% relative to lower phytase inclusion levels. This production improvement is explained by the combination of greater animal growth (1.3%) and lower feed consumption (3.5%). Tendencies were observed in the net bone weight (10.41, 11.50, and 11.24 g, for 500, 800, and 1,500 FTU/kg, respectively; P = 0.05) and in bone ash content (6.26, 6.88, and 6.71 g for 500, 800, and 1,500 FTU/kg, respectively; P = 0.08), with greater values at 800 and 1,500 FTU/kg compared with 500 FTU/kg. The inclusion of 1,500 FTU/kg phytase significantly (P &lt; 0.05) reduced fecal P and calcium content throughout the study compared with inclusion levels of 500 and 800 FTU/kg. The results of this study demonstrate the potential of adding 1,500 FTU/kg phytase to diets formulated without inorganic P to improve feed conversion, bone mineralization, and environmental sustainability, and could be an economically advantageous solution to reduce feed costs.