Evaluation of phytase concentration needed for growing-finishing commercial turkey toms.

1. Growth performance, serum bone markers, and bone strength and mineralisation were determined in tom turkeys grown from 9 to 17 weeks of age. 2. Dietary non-phytate phosphorus was formulated to be reduced by 1.0 g/kg in the low phosphorus diet compared to a control diet and phytase was added to provide 0, 150, 300, 450 or 600 units/kg activity to the low phosphorus diet. 3. From 9 to 12 weeks of age, body weight and gain:food were reduced by the low phosphorus diet without added phytase, compared to the adequate phosphorus diet. Increasing the concentration of phytase linearly increased these growth parameters. There were no significant growth responses at 17 weeks of age. 4. Serum osteocalcin was reduced by increasing dietary phosphorus at 12 weeks of age when growth was affected, but not at later ages. Serum pyridinoline was reduced by higher dietary phosphorus and decreased linearly with increasing phytase activity at 17 weeks of age. 5. Fracture force of the ulna and femur increased linearly with increasing phytase activity but bone strength was not affected when corrected for bone cross-sectional area. Bone strength of the ulna and ash concentration of the ulna and tibia were increased by higher dietary phosphorus. Humerus and ulna ash increased linearly with increasing phytase activity. 6. Water-soluble phosphorus content of the litter was increased by higher dietary phosphorus and addition of phytase to the low phosphorus diet. The increase in water-soluble phosphorus content of the litter when phytase was fed may indicate that phosphorus could be fed at a lower concentration than used in this trial, at least in the finisher diet when phytase is added to the food. 7. Bone fracture force, strength and ash were generally optimised when 450 units/kg phytase activity was added to the low phosphorus diet. However, growth performance was best in the grower I (9 to 12 weeks) phase when 600 units/kg phytase was added to the diet.

Benefit of feeding dietary calcium and nonphytate phosphorus levels above National Research Council recommendations to tom turkeys in the growing-finishing phases.

This experiment evaluated the effects of feeding various dietary Ca and nonphytate P (nPP) levels to Large White male turkeys from 3 to 17 wk of age. After consuming a common prestarter diet, poults were fed approximate NRC (1994) levels of dietary Ca and nPP from 3 to 9 wk of age or levels approximately 25% higher. From 9 to 17 wk of age, each starter group was fed approximately 75 (low P), 100 (medium P), or 145% (high P) of the NRC (1994) requirements for Ca and nPP. Diets were fed as crumbles to 6 wk of age and as pellets from 6 to 17 wk of age. There were no effects on BW or feed efficiency to 9 wk of age. Litter P was increased by 21% when high Ca and nPP were fed from 3 to 9 wk. High dietary Ca and nPP fed during the growing-finishing period generally improved bone strength and ash. Tibia strength and ash were higher in the medium P group compared with in the low P group. Wing bone strength was greater in the high P group than in both the birds fed low or medium P. Litter P was increased by 23% when High P was fed in the growing-finishing period compared to the birds fed the Medium P diet during the same period. The results show there is a benefit to bone strength and mineralization when Ca and nPP are fed at levels higher than NRC (1994) recommendations.