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.

摘要 本研究开展两项试验，以评估4种不同膨化温度（90、100、110、120 ℃）下膨化大豆粕（ESC）的表观代谢能（AME）、氮校正表观代谢能（AMEn）以及标准回肠氨基酸消化率（SIDC）。

试验1选取300只雄性肉鸡，随机分为5组：4个处理组为600 g·kg⁻¹基础日粮 + 400 g·kg⁻¹对应不同膨化温度的膨化大豆粕，外加1个基础日粮对照组，每组设6个重复，每个重复10只鸡。试验于14~23日龄采用全收粪法开展代谢试验，以测定AME与AMEn。结果显示，膨化温度对AMEn存在二次效应，估算得到105.58 ℃时AMEn达到最大值3424.99 kcal·kg⁻¹。

试验2选取300只雄性肉鸡，随机分为5组：4个处理组为453 g·kg⁻¹无氮日粮 + 547 g·kg⁻¹对应不同膨化温度的膨化大豆粕，外加1个无氮日粮对照组，每组设6个重复，每个重复10只鸡。试验日粮饲喂期为16~21日龄，21日龄时采用颈椎脱臼法处死肉鸡，采集回肠食糜，以测定膨化大豆粕的SIDC。其中赖氨酸、蛋氨酸、半胱氨酸的最优SIDC分别为0.824%、0.908%和0.741%，对应膨化温度分别为117.72 ℃、114.40 ℃和107.37 ℃；其余测定氨基酸的SIDC随膨化温度升高呈线性提升，且消化率数值更优。

综上，膨化温度会影响肉鸡饲用大豆粕的代谢能与氨基酸消化率，因此标准化膨化温度对于最大化肉鸡日粮中大豆粕的营养价值具有重要意义。