Influence of differential protein levels of feed on growth, copper‐induced immune response and oxidative stress of Rhynchocypris lagowski in a biofloc‐based system

Abstract

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 bioflocbased 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.

Growth performance, tissue mineralization, antioxidant activity and immune response of oreochromis niloticus fed with conventional and gluconic acid zinc dietary supplements

“…Indeed, dietary supplements may have a better advantage in improving the fish immune response or control the severity of infection (Menanteau‐Ledouble et al, 2017). The biological trial has demonstrated that dietary supplements are the key source to maintain optimal growth and health of fish, which have high biocompatibility and sustainability (Wu et al, 2019; Yu et al, 2020).…”

Dietary supplementation with biofloc promotes growth, improves immune and antioxidant status, and upregulates NF‐κB/Nrf2 signalling molecules and stress resistance in Rhynchocypris lagowskii Dybowski

“…They can recognize denatured proteins, assist protein repair, stimulate immunity, reduce oxidative damage and play a protective role (Li, Li, et al., 2019; Roberts et al., 2010). Interferon‐γ can effectively block the invasion of pathogens, along with a variety of immune enzymes, to resist virus infection (Yu, Zheng, et al, 2020b). IGF‐1 is a necessary active protein polypeptide in the physiological process of growth hormone production, and it has the laudatory name “growth hormone medium” (Chen et al., 2016).…”

“…Growth index and muscle nutrient composition (e.g. WGR, SGR, feed conversion rate [FCR], protein efficiency rate [PER], hepatosomatic index [HI], viscerasomatic index [VI], condition factor [CF], moisture, ash, crude lipid and crude protein) were measured, with reference to our previous study (Yu, Quan, et al., 2020; Yu, Zheng, et al., 2020b). Second, the gill, kidney, hepatopancreas and gut were removed quickly from each living fish by vivisection on a liquid nitrogen cold plate; the tissues were washed with ice‐cold double‐distilled water, cut into pieces and mixed with physiological saline at 1:9 (W:V).…”

“…Amylase (starch‐iodine colorimetric method, Long et al., 2015), lipase (methyl halogen substrate method, Yu, Wu, et al., 2020) protease (ultraviolet colorimetric method, Anand et al., 2014), and lysozyme activities (turbidimetric method, Chen, Ren, Wang, et al., 2018); complement C3, complement C4 and immunoglobulin M (IgM) levels (immune turbidimetry, Li, Liu, et al., 2019; Li, Zhu, et al., 2019); insulin‐like growth factor I (IGF‐1), interferon‐γ (IFN‐γ), heat shock protein 70 (HSP70) and heat shock protein 90 (HSP90) contents (double antibody sandwich enzyme‐linked immunosorbent assay, Yu, Zheng, et al., 2020b); total superoxide dismutase (T‐SOD) activity (hydroxylamine method, Wang et al., 2019); total antioxidant capacity (T‐AOC) (ABTS fast method, Li, Li, et al., 2019); catalase (CAT) activity (visible light method, Panigrahi et al., 2019); glutathione peroxidase (GSH‐PX) activity (turbidimetric method, Feng et al., 2016); and malondialdehyde (MDA) content (TBA method, Yin et al., 2018) were determined using commercial assay kits (Nanjing Jiancheng Bioengineering Institute, Nanjing, China).…”

“…Then, their body length and body mass were measured, and the muscles above the lateral line and below the dorsal were collected. TA B L E 3 Primers for real-time qPCR analysis protein) were measured, with reference to our previous study (Yu, Quan, et al, 2020;Yu, Zheng, et al, 2020b). Second, the gill, kidney, hepatopancreas and gut were removed quickly from each living fish by vivisection on a liquid nitrogen cold plate; the tissues were washed with ice-cold double-distilled water, cut into pieces and mixed with physiological saline at 1:9 (W:V).…”