As a part of phytic phosphorus (PP) is not digested with usual dietary inclusion range (500 FTU/kg) of microbial phytase (PhytM), greater concentrations of phytase (superdose), should further improve PP digestion in pigs. Effects of a superdose of PhytM on gastrointestinal tract pH, PP degradation, P and Ca concentrations and digestibility among the different gastrointestinal tract (GIT) segments were assessed. Twenty-four pigs of 41 kg were randomly assigned to one of the three experimental diets containing 0, 500 or 2000 FTU/kg of PhytM. Control diet without PhytM was formulated to contain 0.34% digestible P and 0.78% total Ca and PhytM, assumed to supply 0.12% digestible P and 0.12% total Ca to both 500 and 2000 FTU/kg diets. After 21 days, pigs were euthanized 2.5h after their last meal and digesta samples from GIT segments were collected. The total P, Ca, PP, and titanium dioxide contents were analyzed in total and soluble fractions and digestibility (disappearance) was calculated. Statistical analysis was done in R using linear (Lin) and quadratic (Quad) contrasts. Dietary differences in pH of the stomach (3.25) and duodenal (5.3) digesta were not detected. The PP degradation was enhanced by PhytM in the stomach (Lin and Quad, P < 0.001) and a total of 10, 42 and 62 % of the PP was degraded in the jejunum for diets containing 0, 500 or 2000 FTU/kg respectively (Lin and Quad, P < 0.001). In the jejunum, P (Lin and Quad, P < 0.01), PP (Lin and Quad, P < 0.001), and Ca (Lin, P < 0.05) concentrations decreased with the addition of PhytM. In the ileum, PhytM decreased only the P concentrations (Lin and Quad, P < 0.01). In the colon, P (Lin and Quad, P < 0.001) and Ca (Lin and Quad, P = 0.06) digesta concentration were decreased by PhytM. Throughout the colon, P digestibility was improved by PhytM (Lin and Quad, P < 0.001) whereas Ca digestibility was not affected. In conclusion, a superdose (2000 FTU/kg) of PhytM improved PP degradation by 1.5 times compared to 500 FTU/kg addition.
