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 <i>in vitro</i> 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 <i>in vitro</i> energy digestibility of okara were analyzed. The <i>in vitro</i> 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 <i>in vitro</i> 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.