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Low utilization of plant P by pigs has been reported due to the 65 to 85% of the total P of plant origin is bound to phytate. Oilseed meals such as canola meal (CM) and soybean meal (SBM) contain large amounts of phytate, and pigs do not have sufficient intestinal phytase to liberate this P from phytate. There is, however, no report on the true P digestibility (TPD) in canola and SBM for growing pigs and the effect of microbial phytase on the TPD. Thus, the objectives of this study were to use the regression analysis technique to estimate TPD in growing pigs fed CM and SBM and to quantify the effect of exogenous microbial phytase supplementation on TPD.
Two studies with growing pigs were conducted using the regression analysis technique to estimate the true digestibility of P (TPD) in canola (CM) and soybean (SBM) meals, and quantify the effect of microbial phytase on TPD of CM and SBM. In each study, 48 (Exp. 1) or 36 (Exp. 2) 17-kg barrows were assigned to 6 dietary treatments arranged in a 3×2 factorial of 3 graded levels of CM (Exp. 1) or SBM (Exp. 2) at 132, 264, or 396 g/kg, and 2 levels of phytase at 0 or 1,000 units/kg. The total collection method was used to calculate P digestibilities.
In Exp. 1, phytase supplementation increased (P < 0.01) the apparent total tract digestibility of P in CM with values ranging from 26 to 33% without phytase and from 57 to 62% with supplemental phytase. Regression of digested P against dietary P intake resulted in a decreased (P < 0.05) TPD estimate of 34.3% for the diet without phytase than the 61.4% TPD estimate for diet with added phytase. In Exp. 2, phytase supplementation improved (P < 0.05) apparent total tract P digestibility for SBM with values ranging from 34.3 to 38.6% without phytase and from 68 to 71.2% with supplemental phytase. True P digestibility estimate for SBM without phytase at 40.9% was different (P < 0.05) from that with added phytase at 70.8%.
The present results indicate a TPD of 34 or 41% in growing pigs fed CM or SBM and demonstrate that the addition of microbial phytase at 1,000 units/kg improves true digestibility of P in CM and SBM by 78 and 73%, respectively.
AS Akinmusire and O Adeola. True digestibility of phosphorus in canola and soybean meals for growing pigs: Influence of microbial phytase. 2009. Journal of Animal Science, 87:977-983. doi:10.2527/jas.2007-0778