Metabolizable energy and amino acid digestibility of soybean cake subjected to different dry extrusion temperatures for broilers

ABSTRACT Two experiments were conducted to evaluate the apparent metabolizable energy (AME), nitrogen-corrected apparent metabolizable energy (AMEn), and standardized ileal amino acid digestibility coefficient (SIDC) of extruded soybean cake (ESC) at four different extrusion temperatures: 90, 100, 110, and 120 °C. In experiment 1, 300 male broilers were randomly distributed into four treatments (600 g kg−1 reference diet + 400 g kg−1 of SBC at different extrusion temperatures) + reference diet, with six replicates of 10 birds. A metabolic assay using the total excreta collection method was performed from 14 to 23 days to determine AME and AMEn. Quadractic effect of the extrusion temperature was observed, with the maximum AMEn value estimated as 3424.99 kcal kg−1 for 105.58 °C. In experiment 2, 300 male broilers were randomly distributed into four treatments (453 g kg−1 protein free diet + 547 g kg−1 SBC at different extrusion temperatures) + protein free diet, with six replicates of 10 birds. Experimental diets were offered from 16 to 21 days, and at 21days, birds were sacrificed by cervical dislocation for collection of the ileal digesta to determine the SIDC of ESC. The best SIDC values for lysine (0.824%), methionine (0.908%), and cysteine (0.741%) were estimated at 117.72, 114.40, and 107.37 °C, respectively. The other amino acids evaluated showed a linear response, with better SIDC values with increasing extrusion temperatures. The extrusion temperatures affect metabolizable energy and amino acid digestibility of soybean cake for broilers, being important the standardization of extrusion temperature to maximize the nutritional value of soybean cake used in broiler diets.