An experiment was conducted to explore the effects of digestible amino acid (dAA) concentrations and supplemental protease on live performance and energy partitioning in broilers. Ross 308 male broilers (n = 288) were distributed into 24 floor pens and offered 1 of 4 dietary treatments with 6 replicates from 1 to 35 d of age. Dietary treatments consisted of a 2 × 2 factorial arrangement with dAA concentrations (standard and reduced [34 g/kg below standard]) and supplemental protease (without or with) as the main factors. At 1, 15, 28, and 35 d of age, feed and broilers were weighed to determine live performance. From 20 to 23 d of age, a total of 32 birds (2 birds/chamber, 4 replicates) were placed in closed-calorimeter chambers to determine respiratory exchange (heat production, HP), apparent metabolisable energy (AME), retained energy (RE), and net energy (NE). From 29 to 35 d of age, supplemental protease in the reduced-dAA diet decreased broiler feed conversion ratio (FCR) by 5.6 points, whereas protease supplementation in the standard-dAA diet increased FCR by 5.8 points. The indirect calorimetry assay revealed that supplemental protease decreased (P < 0.05) the heat increment of feed (HIF) by 0.22 MJ/kg. Also, from 20 to 23 d of age, broilers offered the reduced-dAA diet with supplemental protease had a higher daily body weight gain (BWG) (+10.4%), N intake (+7.1%), and N retention (+8.2%) than those offered the standard-dAA with supplemental protease. Broilers offered the reduced-dAA without supplemental protease exhibited a 3.6% higher AME-to-crude protein (CP) ratio than those offered other treatments. Protease supplementation in the standard- and reduced-dAA diets resulted in 2.7% and 5.6% lower AME intake-to-N retention ratios, respectively, compared with the unsupplemented controls. Reduced-dAA increased (P < 0.05) AME intake (+4.8%), RE (+9.8%), NE intake (+5.8%), NE intake-to-CP ratio (+3.0%), and RE fat-to-RE ratio (+8.6%). Protease supplementation increased (P < 0.05) respiratory quotient (+1.2%) and N retention-to-N intake ratio (+2.2%), NE-to-AME ratio (+1.9%), and reduced HP (−3.6%), heat increment (−7.4%), and NE intake-to-N retention (−2.5%). In conclusion, protease positively affected FCR and energy partitioning in broilers; responses were most apparent in diets with reduced-dAA concentrations.

进行了一项实验来探索可消化氨基酸 (dAA) 浓度和补充蛋白酶对肉鸡的活体性能和能量分配的影响。罗斯 308 雄性肉鸡（n = 288) 被分配到 24 个地板围栏中，并在 1 至 35 日龄期间提供 4 种饮食处理中的 1 种，6 次重复。膳食处理由 2 × 2 因子排列组成，其中 dAA 浓度（标准和降低 [低于标准 34 g/kg]）和补充蛋白酶（没有或有）作为主要因素。在 1、15、28 和 35 日龄时，称重饲料和肉鸡以确定活体性能。从 20 到 23 日龄，总共 32 只鸡（2 只鸡/室，4 个重复）被放置在封闭的热量计室中，以测定呼吸交换（产热，HP）、表观代谢能（AME）、保留能量（ RE）和净能（NE）。从 29 日到 35 日龄，在减少 dAA 日粮中添加蛋白酶可使肉鸡饲料转化率 (FCR) 降低 5.6 个百分点，而在标准 dAA 饮食中补充蛋白酶可使 FCR 提高 5.8 个百分点。间接量热测定显示补充蛋白酶减少（P  < 0.05) 饲料热增量 (HIF) 增加 0.22 MJ/kg。此外，从 20 日龄到 23 日龄，提供低 dAA 日粮和补充蛋白酶的肉鸡具有更高的每日体重增加 (BWG) (+10.4%)、N 摄入量 (+7.1%) 和 N 保留 (+8.2%) %) 比那些提供标准 dAA 和补充蛋白酶的。在不添加蛋白酶的情况下，提供减少 dAA 的肉鸡的 AME 与粗蛋白 (CP) 的比率比提供其他处理的肉鸡高 3.6%。与未补充的对照组相比，在标准和减少 dAA 饮食中补充蛋白酶分别导致 AME 摄入量与 N 保留率降低 2.7% 和 5.6%。减少-dAA增加（P < 0.05) AME 摄入量 (+4.8%)、RE (+9.8%)、NE 摄入量 (+5.8%)、NE 摄入量与 CP 的比率 (+3.0%) 和 RE 脂肪与 RE 的比率 (+8.6 %）。蛋白酶补充剂增加（P  < 0.05）呼吸商（+1.2%）和氮保留与氮摄入的比率（+2.2%）、NE 与 AME 的比率（+1.9%），并降低 HP（-3.6%） 、热量增量（-7.4%）和 NE 摄入对 N 的保留（-2.5%）。总之，蛋白酶对肉鸡的 FCR 和能量分配有积极影响；在 dAA 浓度降低的饮食中反应最为明显。