| Three experiments were conducted to determine the apparent effective energy values of wheat by three bioassay methods in broiler, and established the optimum regression equations for predicting AME by chemical and physical indexes, and evaluating the effect of two xylanases on the apparent effective energy of wheat.Experiment 1, This trail was taken on 480 AA broilers aged 26~31 days to determine the apparent effective energy values AME, AMEn and IDE ( ileal apparent digestible energy ) of 14 wheat samples from different regions. by three bioassays, which included total feces collection, marker in excreta and ileal digesta procedure. The differences of apparent effective energy values of wheat among the three methods were compared, and physiochemical indexes of wheat were also measured. It was concluded that: (1) The average values of AME1, AMEn1 determined with total feces collection were 13.27 MJ/kg and 12.95 MJ/kg; The average values of AME2, AMEn2 determined with marker method were 12.64 MJ/kg and 12.01 MJ/kg; The average of IDE determined with ileal digesta procedure was 12.40 MJ/kg; (2) AME1 had significant difference with AME2, AMEn2, IDE (P<0.05), and there was no significant difference between the others (P>0.05); besides, IDE was higher than AMEn2, and lower than the others; (3) To the coefficient of variation (C.V), the average values of IDE, AME2, AMEn2, AME1, AMEn1, in descending order, were 13.81%, 10.86%, 10.44%, 10.40%, 10.18%, respectively.Experiment 2, According to the apparent metabolizable energy values of wheat from experiment 1, the direct and indirect effects of physical and chemical indexes of wheat on AMEn were analyzed with SAS software, and the optimum regression equation were established subsequently. It was concluded that: (1) The direct effect of crude protein(CP) on AMEn was the largest, path coefficient was 0.581, next was Viscidity(V), which was -0.531; The indirect effect of ether extract(EE) on AMEn was the largest, path coefficient was 0.983, next were ADF, Glucan, which were -0.837,-0.74; respectively; (2) The important predictors were CP and V, The optimun regression equation was AMEn = 10.319 + 0.323 CP– 0.010V (R2 = 0.9534, P < 0.05).;(3) CP and V were the major factors affecting the AMEn, therefore, the regression equation established according to CP and V of wheat can predict the AMEn of wheat well.Experiment 3, 624 AA broilers aged 26~31 days were randomly assigned into 13 treatments, with 8 replicates each treatment (6 broilers each replicate). The treatment 1 was the control group, the other 12 treatments were a total random design with two factors (wheat and xylanases). The wheat had 4 levels (samples), and the xylanases had 3 levels (no xylanase, xylanase A 400 mg/kg, xylanase B 257.56 mg/kg). The additive effect of two xylanases on AME and AMEn was evaluated with marker method. It was concluded that: (1) The two xylanases increased AME and AMEn of wheat significantly (P<0.01). The effect of xylanase B was better than xylanase A. Adding xylanase A 1500 U/kg increased the AME and AMEn of wheat by 420 KJ/kg and 300 KJ/kg, respectively; and xylanase B 1500U/kg increased the AME and AMEn of wheat by 790 KJ/kg and 710 KJ/kg, respectively. The effect of xylanase B is 50% higher than xylanase A; (2) Under the condition of this experiment, interaction between wheat and xylanase was not significant (P>0.05), which indicated that wheat breed could not effect the application effect of xylanase. |
