The current dietary copper (Cu) requirement (8 mg/kg) of broilers is mainly based on growth, hemoglobin concentration, or hematocrit, which might not be the most sensitive indices to evaluate dietary Cu requirements of broilers. The present study was carried out to estimate dietary Cu requirements of broilers fed a conventional corn-soybean meal diet from 1 to 21 d of age using biochemical or molecular biomarkers. A total of 384 1-d-old Arbor Acres male broilers were randomly allocated to 1 of 6 treatments with 8 replicates and fed a Cu-unsupplemented corn-soybean meal basal diet containing 5.17 mg Cu/kg by analysis and the basal diet supplemented with 3, 6, 9, 12 or 15 mg Cu/kg as CuSO₄⋅5H₂O for 21 d. Regression analysis was performed to estimate the optimal dietary Cu level using the broken-line model. Dietary supplemental Cu level affected (P < 0.05) Cu contents in serum and liver and kidney monoamine oxidase (MAO) activity, but had no effects (P > 0.05) on the growth performance, Cu contents in heart, kidney, pancreas and spleen, Cu- and zinc-containing superoxide dismutase (CuZnSOD) activity and ceruloplasmin content in serum, CuZnSOD and cytochrome c oxidase (COX) activities and ceruloplasmin, CuZnSOD, MAO A, MAO B, COX 4I1 and COX 1 mRNA and protein expressions in the above tissues of broilers. As dietary supplemental Cu levels increased, Cu contents in serum and liver increased linearly (P < 0.05), but kidney MAO activity decreased linearly and quadratically (P < 0.05). The estimated dietary Cu requirement based on the fitted broken-line model (P = 0.035) of kidney MAO activity was 11.30 mg/kg. In conclusion, kidney MAO activity is a new and sensitive criterion to evaluate the dietary Cu requirement of broilers, and the dietary Cu requirement was 11.30 mg/kg for broilers fed the conventional corn-soybean meal diet from 1 to 21 d of age, which is higher than the current National Research Council (NRC) Cu requirement (8 mg/kg) of broilers.

目前肉鸡日粮铜 (Cu) 需求量 (8 mg/kg) 主要基于生长、血红蛋白浓度或红细胞比容，这可能不是评估肉鸡日粮铜需求量的最敏感指标。本研究旨在使用生化或分子生物标志物估计 1 至 21 日龄饲喂常规玉米-豆粕日粮的肉鸡的日粮铜需求量。总共 384 只 1 日龄 Arbor Acres 雄性肉鸡被随机分配到 6 个处理中的 1 个处理，8 个重复，并饲喂经分析含有 5.17 mg Cu/kg 的未添加铜的玉米-豆粕基础日粮，基础日粮中添加了3、6、9、12或 15 mg Cu/kg 作为 CuSO ₄ ⋅5H ₂O 21 天。使用折线模型进行回归分析以估计最佳膳食铜水平。日粮补充铜水平影响（P  < 0.05）血清铜含量和肝肾单胺氧化酶（MAO）活性，但 对生长性能、心脏、肾脏、胰腺和脾脏铜含量无影响（P > 0.05），血清中含铜和锌的超氧化物歧化酶 (CuZnSOD) 活性和铜蓝蛋白含量、CuZnSOD 和细胞色素c氧化酶 (COX) 活性和铜蓝蛋白、CuZnSOD、MAO A、MAO B、COX 4 I 1和COX 1肉鸡上述组织中mRNA和蛋白的表达。随着膳食补充铜含量的增加，血清和肝脏中的铜含量呈线性增加（P  < 0.05），而肾脏MAO活性呈线性和二次下降（P  < 0.05）。根据 肾脏 MAO 活性拟合折线模型 ( P = 0.035)估算的膳食铜需求量为 11.30 mg/kg。综上所述，肾脏 MAO 活性是评价肉鸡日粮铜需要量的一个新的敏感标准，在 1-21 日龄饲喂常规玉米豆粕日粮的肉鸡日粮铜需要量为 11.30 mg/kg。高于当前国家研究委员会 (NRC) 对肉鸡的铜需求量 (8 mg/kg)。