Reducing the phosphorus concentration in diets for turkeys between 10 and 22 weeks of age

1. An experiment lasting for 13 weeks was started at the beginning of week 10 with male turkeys weighing 5.38 kg. The experiment comprised three subsequent periods with adjusted metabolisable energy (ME) and nutrient concentrations from weeks 10 to 13, 14 to 17, and 18 to 22. Seven pens of 12 birds each were allocated to each of 5 treatments. Treatments differed in dietary phosphorus concentration and phytase supplementation (500 U/kg) only. Total phosphorus varied between treatments from 4.9 to 8.0 g/kg (weeks 10 to 13), from 4.4 to 7.5 g/kg (weeks 14 to 17) and from 3.5 to 7.0 g/kg (weeks 18 to 22). Phosphorus concentration was adjusted by different inclusions of monocalcium phosphate. Diets were pelleted and offered ad libitum. 2. A final body weight of, on average, 22.3 kg was achieved at the end of week 22. Body weight gain, feed consumption, feed conversion, toe ash, toe phosphorus and toe calcium were not significantly affected by dietary phosphorus concentration. There was no indication of an effect on mortality or on broken or deformed bones. 3. Phosphorus concentrations (g/kg diet) of 5.9, 5.4 and 4.4 without microbial phytase and of 4.9, 4.4 and 3.5 with microbial phytase, respectively, were sufficient in the three periods. As compared with the control, a reduction in phosphorus excretion of turkeys by 0.4 without phytase and by 0.5 with phytase was achieved without negative effects on turkeys. 4. Because the data demonstrate the great potential for a reduction in dietary phosphorus concentration, detailed requirement and availability studies with turkeys should follow.