Influence of Broiler Age on the Apparent Metabolizable Energy of Cereal Grains Determined Using the Substitution Method

SIMPLE SUMMARY: Knowledge of the metabolizable energy content of cereal grains is critical for their economical and sustainable use and precise poultry feed formulation. The current practice in the feed industry is to use the apparent metabolizable energy (AME) or nitrogen-corrected AME (AMEn) values of ingredients from prediction equations or reference tables, which have been estimated using (5-week-old birds). Several factors, including age, ingredient type, and methodology, can affect the AMEn value of ingredients in poultry. Currently, there are no data available on the age effect, from hatch to 6 weeks of age, on the AMEn of grains in broilers. The aim of the present study was to investigate the influence of age on the AMEn of wheat, sorghum, barley, and corn from hatching to day 42 using the substitution method. The results showed that the age influence on the AMEn of cereal grains was grain dependent. In wheat and sorghum, AMEn was influenced by age, while the AMEn of barley and corn were unaffected. Poultry nutritionists might need to consider age-dependent AME or AMEn values for some grains in feed formulations. ABSTRACT: The present study investigated the influence of broiler age on the AMEn of wheat, sorghum, barley, and corn using the substitution method at six different ages (days 7, 14, 21, 28, 35, and 42). A corn-soybean meal basal diet was formulated and, the test diets were developed by replacing (w/w) 300 g/kg of the basal diet with wheat, sorghum, barley, or corn. Bird age influenced (p < 0.001) the AMEn of wheat and sorghum but had no effect (p > 0.05) on those of barley and corn. The AMEn of wheat increased with age (p < 0.001) from 12.53 MJ/kg DM in week 1 to 14.55 MJ/kg DM in week 2, then declined subsequently, but no linear or quadratic responses were observed. The AMEn of sorghum demonstrated a quadratic response (p < 0.05), increasing from 12.84 MJ/kg DM in week 1 to 13.95 MJ/kg DM in week 2, and then plateauing to week 6. Overall, the present results suggest that the effect of broiler age on the AMEn varies depending on the grain type. The current data suggest that the application of age-dependent AME or AMEn of wheat and sorghum will lead to more precise feed formulations.