Information regarding how much phytase should be added to the diet and how phytase influences performance of chickens has accumulated. However, how phytase affects skeletal formation remains unanswered. They provide a good opportututy to study effectiveness of supplemental phytase and its influence on these lines. Preliminary studies have shown that minimal dietary supplementation of phytase at 3OOIUkg can significantly decrease mortality, which makes the selection experiment economically feasible. The studies also indicated variation of phytate phosphorus utilization probably existed among TD lines and their families.
Body weight is a key character in broilers for utilization of phytate phosphorus.
Thus, the present study was conducted to divergently select 6-week BW under a P deficient environment with added phytase. Broiler chicks were fed two rations, one containing 300 UIkg phytase without supplemental inorganic P and the other a normal control diet Individual BW was measured at week 2,4 and 6 and the incidence of'ID was evaluated at week 5. At week 2, there were no significant differences for mortality among the TD lines. The incidence in the H line responded to phytase more dramatically than those of C and L lines. In conclusion, there were differences in ability of broilers to utilize phytate P with the addition of phytase.