Effects of phytase on amino acid and energy digestibility in corn–soybean meal diets fed to growing pigs

An experiment was conducted to determine whether the effects of phytase on amino acid (AA) and energy digestibility in pigs is influenced by the concentration of dietary P. Fourteen barrows (initial BW: 37.8 ± 4.7 kg) were surgically fitted with a T-cannula in the distal ileum and randomly allotted to a replicated 7 × 7 Latin square design with 7 diets and 7 periods. Six diets were formulated to contain inadequate (0.13%) or adequate (0.23%) concentrations of calculated available P and supplemented with 3 levels (0, 250, or 500 phytase units/kg of diet) of an Escherichia coli phytase (OptiPhos 2000, Enzyvia, Sheridan, IN). A N-free diet was also formulated to measure ileal endogenous AA losses. Standardized ileal digestibility of AA and apparent ileal digestibility and apparent total-tract digestibility of energy and P were measured. Interactions between the effects of available P and phytase on all measured parameters were significant (P < 0.05). In diets containing inadequate available P, phytase supplementation improved (linear, P < 0.05) the standardized ileal digestibility of AA, the apparent ileal digestibility and apparent total-tract digestibility of energy, and the apparent total-tract digestibility of P. In diets with adequate available P, phytase supplementation had a quadratic effect (P < 0.05) on the apparent ileal digestibility of energy and on the standardized ileal digestibility of some AA. In conclusion, OptiPhos phytase may improve the digestibility of AA and energy if dietary P supply is inadequate, whereas in diets containing adequate concentrations of P, no effect of phytase on the digestibility of AA and energy was observed.