Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2009
Publication Date: 12/1/2009
Citation: Kerr, B.J., Weber, T.E., Miller, P.S., Southern, L.L. 2009. Effect of Phytase on Apparent Total Tract Digestibility of Phosphorus in Corn-Soybean Meal Diets Fed to 100 kg Pigs. Journal of Animal Science. 88:238-247. Interpretive Summary: Phosphorus (P) is an essential nutrient for energy utilization, a component in many enzyme systems, and bone formation. Plant P is in the form of phytin–P and is largely unavailable to the animal; consequently, P is often supplemented to swine diets by various animal and inorganic sources. Exogenous phytase has been shown to be an effective enzyme to release moderate amounts of phytin-P resulting in improved P balance in swine and, subsequently, reducing environmental P excretion. The objectives of the current experiments were to define the response curve of apparent P digestion as affected by level and source of exogenous phytase in finishing pigs and to subsequently predict the amount of inorganic P release at an assumed level of phytase supplementation. Data presented show clear improvements in P digestibility regardless of which phytase was used, with the estimated level of inorganic P release being dependent upon phytase source and level. This information is important for nutritionists at pork production companies to improve the utilization of dietary P and, consequently, maintain or improve pig productivity, decrease diet costs, and reduce the excretion of P into the environment.
Technical Abstract: Five experiments were conducted to investigate the ability of different sources of phytase supplemented to the diet at graded levels to improve apparent P digestibility in finishing pigs. A corn-soybean meal basal diet containing 0.50% Ca and 0.32% P (0.06% available P) was used in all experiments and all diets contained 0.40% chromic oxide as an indigestible marker to calculate apparent P and energy digestibility. All pigs were individually penned and fed their respective diet ad libitum for 12 d prior to fecal grab sampling on d-13 and 14 for P. Experiment 1 through 4 each utilized 3 groups of 24 gilts with an initial and final BW of 84 and 97 kg, respectively. Pigs were fed either Nathphos (Exp. 1), Optiphos (Exp. 2), Phyzyme (Exp. 3), or Ronozyme (Exp. 4) at 0, 200, 400, 600, 800, or 1,000 FTU/kg in each experiment. In Exp. 5 there were 2 groups of 36 barrows with an initial and final BW of 98 to 111 kg, respectively, and were fed diets containing 0, 500, or 1,000 FTU/kg of Nathphos, Optiphos, Phyzyme, or Ronozyme. Pigs fed Natuphos (Exp. 1) and Optiphos (Exp. 2) exhibited a quadratic (P < 0.01) improvement in P digestibility with increasing levels of dietary phytase; while pigs fed Phyzyme (Exp. 3) and Ronozyme (Exp. 4) exhibited a linear (P < 0.01) improvement in apparent P digestibility with increasing levels of dietary phytase. In Exp. 5, the improvement in apparent P digestibility with increasing levels of dietary phytase was linear (P < 0.01) for Natuphos, Phyzyme, and Ronozyme, but quadratic (P < 0.01) for Optiphos. Using regression equations, the increase in inorganic P release at 500 FTU/kg was predicted to be 0.072, 0.096, 0.039, and 0.030 percentage unit for Natuphos, Optiphos, Phyzyme, and Ronozyme, respectively. This compares favorably to pigs in Exp. 5 where the estimated inorganic P release at 500 FTU/kg was 0.101, 0.039, and 0.028 for Optiphos, Phyzyme, and Ronozyme, respectively, but not for the 0.034 value determined for Natuphos. The effect of dietary phytase on energy digestibility was inconsistent with a linear (P < 0.01) improvement in energy digestibility noted for Optiphos (Exp. 2) and Ronozyme (Exp. 4), and quadratic for Natuphos and linear for Optiphos (P < 0.01) in Exp. 5. There was no effect of dietary phytase on plasma inorganic P. Data presented show clear improvements in P digestibility regardless of which phytase was used, with the estimated level of inorganic P release being dependent upon phytase source.