| An experiment was conducted using a total of 350 8-day-old Arbor Acre male chicks to evaluate the effects of corn soybean meal diets added phytase (0,500 and 1,000u/kg) and sodium gluconate (NaGlu, 0 and 2%) on growth performace, nutrients utilization, bone characteristics, gastrointestinal pH and carcass traits of broilders. A 3×2 factorial arrangement of treatments was adopted in the experiment. A positive control diet (PC diet) adequate in nonphytate phosphorus (NPP) (0.2%) and calcium (Ca, 0.9% and 0.85% for two periods respectively) without NaGlu and phytase was used. Chickens were randomly assigned by body weight to seven treatments and each dietary treatment was replicated 5 times with ten birds per replicates.The experiment was lasted 35d and was divided into growing period (8-21d) and finishing period (22-42d). The results showed as follows:1) Comparing to the PC diet, the low-NPP diet caused a negative effect (P<0.001) on the average daily gain (ADG), average daily feed intake (ADFI) during the whole periods. Ca apparent retention (P=0.001) in growing period and P apparent retention(P=0.028) in finishing period,tibia weight (P<0.001), tibia ash content(%) (P<0.001) at 21d and 42d and abnormal fat percentage(P=0.001) of broilers. Feed/gain, Nitrogen (N) apparent retention and energy apparent metabolism, gastrointestinal pH, tibia ash Ca and P content, blood criteria, carcass traits of broilers were not different in these two groups. (P>0.10).2) Adding phytase improved ADG and ADFI(P<0.001), Ca (P=0.005,P=0.020) and P (P<0.001,P=0.036)apparent retention during the whole periods, tibia weigh(tP<0.001), tibia ash content (%)(P<0.001)at 21d and 42d, tibia ash P content (P=0.03) at 21d, tibia ash Ca content (P=0.013) at 42d and abnormal fat percentage (P=0.001); phytase addition tended to improve percentage of eviscerated yield (P=0.065), leg muscle percentage (P=0.093), alkaline phosphatase (AKP) at 21d and decreased ileum pH (P=0.070). The ADG in growing and finishing periods, ADFI during the whole periods, P apparent retention from 8d to 21d, tibial ash content (%) at 21d, tibia ash content (mg) at 42d were higher in 1000u/kg group than that in 500u/kg group. The dry matter (DM) apparent retention from 8 to 21d, tibia weight at 21d, tibia ash P content at 21d and 42d, Ca and P apparent retention during the whole periods,tibia ash content (%) at 42d in 500u/kg group reached the positive control level. The ADG and ADFI in growing period, tibia weight and tibia ash (mg) at 42d, tibia ash content at 21d and at 42d reached the positive control level in 1000U/kg group.3) Adding 2% NaGlu improved ADG from 22d to 42d (P=0.005) and from 8 to 42d (P=0.009),Ca (P=0.003),P (P<0.001),DM (P<0.001) apparent retention in growing period, tibia ash content (%) (P=0.002) at 21d, serum Ca content (P=0.035) at 42d and indecreased AKP (P=0.038) at 21d. 2% NaGlu addition tended to improve ADFI from 22 to 42d (P=0.084) and from 8 to 42d (P=0.078), feed/gain (P=0.066) from 22 to 42d, tibia weigh (P=0.094) at 42d and abnormal fat percentage (P=0.063). DM apparent retention from 8 to 21d and Ca and P apparent retention during two periods, tibia ash P at 21d in 2% NaGlu addition group reached the PC level.4) There were interactions between phytase and NaGlu for ADG (P=0.027) and P apparent retention (P=0.008) in growing period, tibia ash (mg) (P=0.030) at 21d, tibia weigh at 42d and abnormal fat percentage (P=0.043). There were interaction trend for ADFI from 8 to 21d, tibia ash P content (P=0.059, P=0.090) at 21d and 42d.These results demonstrated that phytase and NaGlu were effective on the growth performance and P utilization of broilers and the combination of phytase and NaGlu might have potential synergistic effects during the whole periods.The fitting adding level of phytase for broilers is higher than 500u/kg.
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