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A 2 × 3 factorial arrangement of treatments with 2 ages of broilers (11 to 14 or 25 to 28 days of age) and 3 samples of feed ingredients was utilized to compare metabolizable energy (ME) and ratio of ME to gross energy (GE) in each group of 3 cereal grains (CG, including 1 corn, 2 wheat flour), 3 oilseed meals (OM, including 1 soybean meal, 1 peanut meal, and 1 cottonseed meal), 3 corn gluten meals (CGM A, B and C), and 3 feather meals (FM A, B and C). Each treatment contained 6 replicates of 4 Arbor Acre male broilers in energy balance experiments. Trends toward interactions between age and source of CG were observed on the ME and ME/GE of CG (0.05 <P < 0.10). The ME and ME/GE in corn was greater for broilers from 25 to 28 than 11 to 14 days of age (P < 0.05). However, the ME and ME/GE in wheat flour A and B were not affected by the age of broilers. The ME and ME/GE of OM were not affected by the age of broilers but differed across sources (P < 0.01). Conversely, the ME and ME/GE of FM were not different across sources of FM, but the ME and ME/GE of FM was less for broilers from 11 to 14 compared to 25 to 28 days of age (P < 0.01). Significant interactions between age and sources of CGM affected the ME and ME/GE of CGM (P < 0.05). The ME and ME/GE of CGM A was greater than CGM B (P < 0.05) when fed to broilers from 25 to 28 days of age but there was no effect from 11 to 14 days of age. The ME and ME/GE of CGM was less in broilers from 11 to 14 compared to 25 to 28 days of age (P < 0.05). These results indicate that the energy value of wheat flour and OM are similar regardless of age, but the ME in starter diets with corn, CGM and FM may be overestimated if the ME values are obtained from growing broilers.

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