Broiler Age Influences the Apparent Metabolizable Energy of Soybean Meal and Canola Meal

SIMPLE SUMMARY: The accurate estimation of the apparent metabolizable energy (AME) content of feed ingredients is crucial for a precise poultry feed formulation. Protein-source ingredients are the second major source of energy supply in broiler diets. The current AME values of protein sources are obtained from reference tables or equations, which have been determined using older broilers (usually 3-5-week-old). In this approach, the effects of broiler age on the AME or nitrogen-corrected AME (AMEn) of feed ingredients are ignored. The objective of the current investigation was to examine the effects of broiler age on the AMEn of soybean meal (SBM) and canola meal (CM) from day 1 to 42 of age. It was found that age has a marked effect on the AMEn of SBM and CM. Nutritionists, therefore, must consider using age-dependent AME or AMEn values for SBM and CM in feed formulation. ABSTRACT: The effects of broiler age on the apparent metabolizable energy (AME) and nitrogen-corrected AME (AMEn) of soybean meal (SBM) and canola meal (CM) were examined. A corn-SBM basal diet was developed, and two test diets were formulated by substituting (w/w) 300 g/kg of the basal diet with SBM or CM. Six groups of broiler chickens, aged 1–7, 8–14, 15–21, 22–28, 29–35 or 36–42 d post-hatch, were utilized. Each diet, in pellet form, was randomly allocated to six replicate cages in each age group. Except for the 1–7 d age group, the birds were fed a starter (d 1–21) and/or a finisher (d 22–35) diet prior to the introduction of the experimental diets. The number of birds per cage was 10 (d 1–7), 8 (d 8–14) and 6 (d 15–42). The AME and AMEn of SBM and CM were determined by total excreta collection. The data for each protein source were subjected to orthogonal polynomial contrasts using the General Linear Models procedure. Bird age decreased the retention of dry matter quadratically (p < 0.001) for both SBM and CM. The retention of nitrogen decreased linearly (p < 0.001) with the advancing age of broilers for SBM and CM. The AMEn of SBM and CM decreased quadratically (p < 0.001) as the birds grew older. The highest AMEn was observed during week 1 for both SBM and CM, then declined until week 3, followed by increases thereafter. The current results showed that the age of broiler chickens influenced the AMEn of SBM and CM and supported the use of age-dependent AMEn of feed ingredients in diet formulations.