Effects of administration of four different doses of Escherichia coli phytase on femur properties of 16-week-old turkeys

BACKGROUND: The enzyme phytase is able to initiate the release of phosphates from phytic acid, making it available for absorption within gastrointestinal tract and following utilization. The aim of the study was to determine effects of Escherichia coli phytase administration on morphological, densitometric and mechanical properties of femur in 16-week-old turkeys. One-day-old BUT Big-6 males were assigned to six weight-matched groups. Turkeys receiving diet with standard phosphorus (P) and calcium (Ca) content belonged to the positive control group (Group I). Negative control group (Group II) consisted of birds fed diet with lowered P and Ca content. Turkeys belonging to the remaining groups have received the same diet as group II but enriched with graded levels of Escherichia coli phytase: 125 (Group III), 250 (Group IV), 500 (Group V) and 1000 (Group VI) FTU/kg. At the age of 112 days of life, the final body weights were determined and the turkeys were sacrificed to obtain right femur for analyses. Geometric and densitometric properties of femur were determined using quantitative computed tomography (QCT) technique, while mechanical evaluation was performed in three-point bending test. RESULTS: Phytase administration increased cross-sectional area, second moment of inertia, mean relative wall thickness, cortical bone mineral density and maximum elastic strength decreasing cortical bone area of femur (P < 0.05). Reduced dietary Ca and P content decreased final body weight of turkeys by 6.5% (P = 0.006). The most advantageous effects of Escherichia coli phytase administration on geometric, densitometric and mechanical properties of femur were observed in turkeys receiving 125 and 250 FTU/kg of the diet. Phytase administration at the dosages of 500 and 1000 FTU/kg of the diet improved the final body weight in turkeys. CONCLUSIONS: The results obtained in this study indicate a possible practical application of Escherichia coli phytase in turkey feeding to improve skeletal system properties and function.