A 21-day experiment was conducted to study the effect of reference diet type and assay method on apparent metabolizable energy (AME) and nitrogen-corrected (AMEn) of soybean meal (SBM) and canola meal (CM). Broilers (n = 240) were allocated to 10 treatments with eight replicates/treatment and three birds/replicate. Treatments included corn-SBM or corn-CM reference diets (RD). To each RD, 300 or 450 g/kg of SBM or CM were added to make a total of eight test diets. For the difference method, AME of SBM and CM substituted at 300 g/kg in corn-CM RD gave greater AME values compared to inclusion in the corn-SBM RD. The AMEn of SBM increased with increase in inclusion level in the corn-CM RD but AMEn of CM decreased with increased inclusion level of CM in the corn-SBM RD. For the regression method, AME and AMEn of the test feedstuffs were greater with corn-CM RD compared with corn-SBM RD. The AME of SBM was not affected by assay method, whereas AME of CM was lower when determined using the regression method. In conclusion, both the reference diet type and assay method influenced assayed AME and AMEn value of test protein feedstuffs and should be considered in cross-studies comparisons.

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Background: This effect of adaptation length (AL) on the apparent metabolizable energy (AME) and nitrogen-corrected AME (AMEn) of maize and barley supplemented with or without β-glucanase enzyme was assessed in this study. Three experimental diets were formulated with a wheat-soybean meal diet as a reference diet (RD) and two additional diets with maize or barley included at 300 g kg À1 into the reference diet. A total of 324 Cobb 500 broilers were used for the experiment in a 3 Â 2 factorial with factors AL (10, 7, or 4 days) and enzyme (with or without) for cereal grains maize and barley. Birds on 10, 7, or 4 days AL were given experimental diets beginning at from d 11, 14, and 17 of age, respectively. Excreta were collected on d 20 and 21. The AME and AMEn of cereal grain were calculated by the difference method.