Effect of microbial phytase on ileal digestibility of phytate phosphorus, total phosphorus, and amino acids in a low-phosphorus diet for broilers

Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand 5301. S.M.Rutherfurd@massey.ac.nz

The study aimed to assess the effect of a commercially available microbial phytase added to a corn-soybean meal diet on phytate P and total P in terminal ileal digesta as well as on true ileal amino acid digestibility. Three low-P diets containing 0, 500, or 750 U/kg of microbial phytase were fed to 21-d-old broiler chickens. Titanium dioxide was used as an indigestible marker. Ileal contents were collected from euthanized birds and analyzed, along with the diets, for total P, phytate P, and amino acids. Endogenous P determined at the terminal ileum was 446 +/- 59 mg/kg food dry matter (mean +/- SE). Endogenous ileal amino acids ranged from 219 +/- 33 mg/kg food dry matter for tryptophan to 1,255 +/- 166 mg/kg food dry matter for glutamic acid. Supplementation with microbial phytase resulted in a significantly (P < or = 0.05) greater phytate P disappearance (11% greater disappearance vs. unsupplemented control) from the terminal ileum. Similarly, true ileal total P digestibility was (P < or = 0.05) higher (10 to 12%) when microbial phytase was added. True ileal amino acid digestibility was significantly (P < or = 0.05) greater in the presence of microbial phytase for all the amino acids examined with the exception of methionine, tyrosine, histidine, and tryptophan. The mean increase in true ileal amino acid digestibility was 3.4%. The effect of phytase on true ileal phytate P, total P, and amino acid digestibility was similar for the 2 phytase inclusion levels tested. Microbial phytase improved phytate P and total P digestibility, as well as true ileal amino acid digestibility, for a corn-soybean diet.

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