Phytate phosphorus hydrolysis in broilers in response to dietary phytase, calcium, and phosphorus concentrations

Three 5-d bioassays were conducted to investigate the microbial phytase effect on apparent phytate phosphorus (PP) hydrolysis by 21-d-old broilers using corn-soybean meal basal diets. In Experiment 1, broilers fed corn-soy basal diet [0.7% Ca, 0.4% total P (TP), and 0.12% nonphytate P (NPP)] with 0, 250, 500, 750, 1,000, 1,500, 2,000, and 5,000 FTU of phytase/kg diet produced PP hydrolysis (%) of 43.12, 68.12, 74.7, 85.02, 85.25 92.77, 96.91, and 99.45, respectively. In Experiment 2, broilers fed corn-soy basal (0.5% Ca and 0.17% PP) without added phytase and 0.08, 0.13, 0.18, 0.23, 0.28, 0.33, 0.38, and 0.45% NPP had PP hydrolysis (%) of 8.5, 27.6, 26.4, 28.9, 26.3, 17.1, 21.0, and 27.7, respectively. Broilers fed the same 0.5% Ca basal and NPP concentrations with 1,000 FTU of phytase/kg of diet increased (P < 0.05) PP hydrolysis (%) to 80.9, 75.9, 73.5, 72.2, 68.4, 71.6, 58.3, and 62.5, respectively. Experiment 3 was conducted in the same way as Experiment 2 but Ca was maintained at 0.9% for all diets. Phytate P hydrolysis (%) without addition of phytase in 0.08, 0.13, 0.18, 0.23, 0.28, 0.33, 0.38, and 0.45% NPP-fed groups was 49.2, 19.6, 16.0, 8.0, 9.4, 2.1, 4.0, and 4.2, respectively. The addition of phytase increased (P < 0.05) PP hydrolysis (%) to 85.3, 76.1, 70.0, 76.1, 62.6, 68.6, 67.4, and 63.7, respectively. In conclusion, these studies indicated near-complete hydrolysis (99.45%) of PP at greater dietary phytase (5,000 FTU/kg) supplementation, but maximum TP retention was obtained with only 1,000 FTU of added phytase. Maximum PP hydrolysis occurred for broilers fed diets with 1,000 FTU added phytase when the diets contained the lowest concentration (0.08%) of dietary NPP with either 0.5 or 0.9% dietary Ca concentrations. These data also suggest that broilers fed 0.9% dietary Ca have a greater P physiological threshold before a loss in retention compared with broilers fed lower (0.5%) dietary Ca concentrations with no dietary phytase supplementation.