Estimation of Apparent Metabolizable Energy of Dried Okara Meal in Broiler Chickens

Metabolizable energy is a key information when formulating chicken feed. The present study employed chemical analysis data and in vitro digestibility values to investigate the apparent metabolizable energy (AME) of dried okara, a soybean byproduct, in broiler chickens. A total of 105 male Ross-308 broiler chickens were fed dehulled rice-soybean meal-based diets containing 0%, 10%, and 20% okara derived from either tofu or soymilk. The proximate composition, neutral detergent fiber content, acid detergent fiber (ADF) content, and in vitro energy digestibility of okara were analyzed. The in vitro digestibility of okara was influenced by particle size, with 0.5-mm samples showing higher digestibility than 1.0-mm samples. Soymilk okara had a higher AME (3300 kcal/kg DM) than tofu okara (2827 kcal/kg DM), which was attributed to its lower ADF but higher protein content. To predict the AME of okara, we developed a stepwise regression model that combined the variables: ADF as X₁, ether extract as X₂, and the in vitro energy digestion rate from the 0.5-mm sample as X₃. AME could be predicted with high accuracy using the following formula: Y = -14.12 X₁ + 20.98 X₂ + 32.42 X₃ + 1100.1 (R² = 0.99, P < 0.01), with minimal root mean square error.