This study compared the influences of differential protein levels of feed on growth, copper‐induced digestive enzyme activity, immune response, oxidative stress and Nrf2 signalling molecules genes expression of Rhynchocypris lagowski in a biofloc‐based system and traditional autotrophic system. Four hundred and fifty R. lagowski were fed four experimental dietary containing graded levels of protein from 25% to 37% (referred as biofloc technology [BFT]25, BFT29, BFT33 and BFT37, respectively) in a biofloc‐based system, and 37% crude protein level (control group) were cultured in an autotrophic system in 8 weeks. At the end of the trial, there was an improvement of 50.35%–61.64% in terms of growth performance (weight gain rate); 0.25–0.53 (U/mg prot) amylase; 6.9–8.02 (U/ml) lysozyme (LZM); and 7.98–8.12 (U/ml) total superoxide dismutase (T‐SOD) in R. lagowski cultured in BFT37 groups as compared to control. Obviously, the growth performance, digestive enzymes activity, immune response, antioxidant statue and antioxidant‐related genes expression of R. lagowski fed with the same protein level in BFT system were significantly higher than those in the control group (p < .05). Furthermore, the level of T‐SOD in liver and kidney and interferon‐γ in liver of BFT33 group were also significantly higher than that of control group (p < .05). Moreover, there was no notable difference of LZM, alkaline phosphatase, complement C3, C4, heat shock proteins 70, heat shock proteins 90, insulin‐like growth factor I, glutathione peroxidase, catalase, total antioxidant capacity, malondialdehyde, Ascorbic acid in gill, liver, kidney, gut and serum among the BFT29 groups and those in the control (p > .05). Besides, bioflocs assists in regulating the expression of Nrf2 signalling molecules including Nrf2, Keap1, Maf, HO‐1, CAT, CuZn‐SOD, GPX and GCLC. We summarized that despite the low protein content in feed, BFT system has the potential to promote growth performance, alleviate copper‐induced immunosuppression and oxidative stress of juvenile R. lagowski.

中文翻译：

---

饲料中蛋白质水平的差异对基于生物絮凝剂的拉格氏梭菌的生长，铜诱导的免疫反应和氧化应激的影响

本研究比较饲料上生长，铜诱导消化酶活性，免疫反应，氧化应激和Nrf2的信号分子的基因的表达差异蛋白水平的影响Rhynchocypris lagowski在基于生物絮凝的系统和传统的自养系统。四百五十R. lagowski在以生物絮凝剂为基础的系统中饲喂四种实验性饮食，其中蛋白质的分级水平分别为25％至37％（分别称为生物絮凝技术[BFT] 25，BFT29，BFT33和BFT37），粗蛋白水平为37％（对照组） ）在自养系统中培养8周。在试验结束时，生长性能（增重率）提高了50.35％–61.64％；0.25–0.53（U / mg蛋白质）淀粉酶；6.9–8.02（U / ml）溶菌酶（LZM）；和7.98-8.12（U / ml）的总超氧化物歧化酶（T-SOD）中R. lagowski在BFT37组培养与对照相比。显然，拉格夫斯基草的生长性能，消化酶活性，免疫反应，抗氧化状态和抗氧化相关基因的表达在BFT系统中以相同蛋白质水平喂养的人明显高于对照组（p  <.05）。此外，BFT33组的肝脏和肾脏中的T-SOD水平和肝脏中的IFN-γ水平也显着高于对照组（p  <.05）。此外，LZM，碱性磷酸酶，补体C3，C4，热激蛋白70，热激蛋白90，胰岛素样生长因子I，谷胱甘肽过氧化物酶，过氧化氢酶，总抗氧化能力，丙二醛，抗坏血酸在difference中没有显着差异BFT29组和对照组中的肝，肾，肠和血清水平（p  > .05）。此外，生物絮凝剂还有助于调节包括Nrf2在内的Nrf2信号分子的表达，Keap1，Maf，HO-1，CAT，CuZn-SOD，GPX和GCLC。我们总结说，尽管饲料中蛋白质含量低，但BFT系统仍具有促进生长性能，减轻铜诱导的幼小R. lagowski免疫抑制和氧化应激的潜力。