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Gut microbiota has shown tight and coordinated connection with various functions of its host such as metabolism, immunity, energy utilization, and health maintenance. To gain insight into whether gut microbes affect the metabolism of fish, we employed fast-growing transgenic common carp (Cyprinus carpio L.) to study the connections between its large body feature and gut microbes. Metagenome-based fingerprinting and high-throughput sequencing on bacterial 16S rRNA genes indicated that fish gut was dominated by Proteobacteria, Fusobacteria, Bacteroidetes and Firmicutes, which displayed significant differences between transgenic fish and wild-type controls. Analyses to study the association of gut microbes with the fish metabolism discovered three major phyla having significant relationships with the host metabolic factors. Biochemical and histological analyses indicated transgenic fish had increased carbohydrate but decreased lipid metabolisms. Additionally, transgenic fish has a significantly lower Bacteroidetes:Firmicutes ratio than that of wild-type controls, which is similar to mammals between obese and lean individuals. These findings suggest that gut microbiotas are associated with the growth of fast growing transgenic fish, and the relative abundance of Firmicutes over Bacteroidetes could be one of the factors contributing to its fast growth. Since the large body size of transgenic fish displays a proportional body growth, which is unlike obesity in human, the results together with the findings from others also suggest that the link between obesity and gut microbiota is likely more complex than a simple Bacteroidetes:Firmicutes ratio change. [ABSTRACT FROM AUTHOR]

Otolith microstructure was analyzed to determine the early growth of Neosalanx taihuensis juveniles from Three-Gorges Reservoir (TGR) and Tian-e-zhou Oxbow (TEO, below the dam). The early growth of the N. taihuensis juveniles differed significantly between the two populations. Higher relative condition index and wider otolith increments of the fish in the TGR indicated the faster early growth and larger otolith nucleus radius indicated the larger size of larvae at hatch for the TGR population, which may result in higher early survival rate. We suggest that increased primary production and food availability following the impoundment of the TGR contributed importantly to the increased early growth and survival of the N. taihuensis population. Fishery management and conservation in the TGR should consider the potential impacts to other fish species and the ecosystem of the increasing abundance of N. taihuensis. [ABSTRACT FROM AUTHOR]

The trial was conducted to investigate the effects of the replacement of dietary fishmeal (FM) by the blend of Tenebrio molitor meal (TMM), Chlorella meal (CM), Clostridium autoethanogenum protein (CAP), cottonseed protein concentrate (CPC) on growth, protein utilization and intestinal health of gibel carp (Carassius gibelio, CAS Ⅴ). The FM-based diet was used as the control, and the blended proteins (TMM: CM: CAP: CPC) at ratios of 1 : 1:8 : 2 (BLEND A), 1 : 1:6 : 4 (BLEND B), and 1 : 1:4 : 6 (BLEND C) were used to replace FM at three levels (33%, 67%, 100%), respectively. The results showed that, compared to the control group, growth performance increased significantly when dietary FM was fully replaced by BLEND B (P < 0.05), while decreased by BLEND A (P < 0.05). The complete substitution of FM with BLEND B significantly upregulated the mRNA expression of intestinal proinflammatory cytokines, anti-inflammatory cytokines, and tight junction-related genes (P < 0.05), improving intestinal tissue morphology and health. And it also significantly increased intestinal trypsin activity (P < 0.05), upregulated the mRNA expression of amino acid sensory receptor-related and amino acid or peptide transport-related genes (P < 0.05), increased protein apparent digestibility coefficient (P < 0.05). The 100% substitution of FM with BLEND A significantly upregulated the mRNA expression of intestinal proinflammatory cytokines and downregulated the mRNA expression of anti-inflammatory cytokine il-10 (P < 0.05), reduced intestinal villus height (P < 0.05), and decreased protein apparent digestibility coefficient (P < 0.05). In conclusion, BLEND B could completely substitute dietary FM and was beneficial to the growth and health of gibel carp. Dietary digestible essential amino acids index (DEEAI) was found as an important indicator and should be higher than 79.5% to meet the maximum growth of fish. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the nutritional value of Clostridium autoethanogenum protein (CAP) as a sole protein source at different dietary protein levels by growth performance, health status, and intestinal microbiota of grass carp. Grass carp (4.56 ± 0.01 g) were randomly divided into 6 treatments in triplicate (30 fish per replicate) and fed with gradient protein level (24.45%, 27.31%, 31.82%, 35.79%, 38.64%, and 42.82%, respectively; named CAP1, CAP2, CAP3, CAP4, CAP5, and CAP6) diets for 8 weeks. Final body weight (FBW) and specific growth rate (SGR) were the significantly highest in the CAP4 group (P < 0.05). Based on SGR and feed efficiency (FE), the dietary protein requirement for juvenile grass carp was estimated to be 36.14–37.90%. CAP4 promoted hepatopancreatic health by reducing lipid deposition and structural lesions, and improved the anti-inflammatory ability by upregulating the relative expression level of il10 (P < 0.05). At the same time, the CAP4 improved the length of mucosal fold and the thickness of muscular layer. In addition, CAP4 can maintain the composition and metabolic function of intestinal microbiota and enhance the endocrine system and bacterial chemotaxis. However, it is worth noting that increasing CAP inclusion depressed hepatopancreatic antioxidant capacity. In conclusion, CAP is a promising novel protein source for grass carp, while careful consideration of its side effect at high inclusion level is deserved. [ABSTRACT FROM AUTHOR]

Excessive carbohydrate intake leads to metabolic disorders in fish. However, few literatures have reported the appropriate carbohydrate level for zebrafish, and the metabolic response to dietary carbohydrate remains largely unknown in zebrafish. This study assessed the responses of zebrafish and zebrafish liver cell line (ZFL) to different carbohydrate levels. In vivo results showed that ≥30% dietary dextrin levels significantly increased the plasma glucose content, activated the expression of hepatic glycolysis-related genes, and inhibited the expression of hepatic gluconeogenesis-related genes in zebrafish. Oil red O staining, triglyceride content, and Hematoxylin-Eosin staining results showed that dietary dextrin levels of ≥30% significantly increased lipid accumulation and liver damage, as well as processes related to glycolipid metabolism and inflammation in zebrafish. In ZFL, the transcription factor sterol regulatory element binding protein-1c signal intensity, 4,4-difluoro-1,3,5,7,8-pentamethyl-4-bora-3a,4a-diaza-s-indacene (BODIPY 493/503) signal intensity, and triglyceride content were also significantly increased when incubated in high glucose, along with abnormal glycolipid metabolism and increased inflammation-related genes. In conclusion, we demonstrated that the maximum dietary carbohydrate level in adult zebrafish should be less than 30%. Excess dietary carbohydrates (30%–50%) caused hepatic steatosis and damage to zebrafish, similar to that seen in aquaculture species. Thus, this study assessed responses to different carbohydrate levels in zebrafish and illustrated that zebrafish is an optimal model for investigating glucose metabolism in some aquatic animals. [ABSTRACT FROM AUTHOR]

To assess the effect of dietary selenium (Se) sources on the meat quality and antioxidant capacity of yellow catfish (Pelteobagrus fulvidraco), sodium selenite (Na2SeO3), Se yeast, and selenium-enriched Spirulina platensis (Se–SP) were supplemented in the control diet at 0.30 mg Se/kg feed to formulate four diets. The experimental period lasted 50 days. The results showed that Se levels in the plasma, liver, muscle, and whole body were significantly increased by dietary Se yeast supplementation (P < 0.05) but showed no change in response to Na2SeO3 (P > 0.05). The three types of Se all increased the firmness and decreased the fracturability of the muscles (P < 0.05), but only Na2SeO3 resulted in higher springiness, flexibility, stringiness, and stickiness (P < 0.05). In addition, the muscle n−3 polyunsaturated fatty acid (PUFA) content was increased by Se yeast (P < 0.05). Regarding antioxidant capacity, dietary Se yeast and Se–SP supplementation improved hepatic glutathione peroxidase activity but decreased hepatic malondialdehyde content (P < 0.05). Given these results, Se yeast was found to be the optimal source of Se for yellow catfish for higher tissue retention, antioxidant capacity, and PUFA levels. Dietary Se is an effective way to regulate the meat quality and antioxidant capacity of yellow catfish. [ABSTRACT FROM AUTHOR]

The present study investigated the sequential regulation signals of high-carbohydrate diet (HCD)-induced hepatic lipid deposition in gibel carp (Carassius gibelio). Two isonitrogenous and isolipidic diets, containing 25% (normal carbohydrate diet, NCD) and 45% (HCD) corn starch, were formulated to feed gibel carp (14.82 ± 0.04 g) for 8 weeks. The experimental fish were sampled at 2nd, 4th, 6th, and 8th week. In HCD group, the hyperlipidemia and significant hepatic lipid deposition (oil red O area and triglyceride content) was found at 4th, 6th, and 8th week, while the significant hyperglycemia was found at 2nd, 4th, and 8th week, compared to NCD group (P < 0.05). HCD induced hepatic lipid deposition via increased hepatic lipogenesis (acc, fasn, and acly) but not decreased hepatic lipolysis (hsl and cpt1a). When compared with NCD group, HCD significantly elevated the hepatic sterol regulatory element binding proteins 1 (SREBP1) signals (positive hepatocytes and fluorescence intensity) at 4th, 6th, and 8th week (P < 0.05). The hepatic SREBP1 signals increased from 2nd to 6th week, but decreased at 8th week due to substantiated insulin resistance (plasma insulin levels, plasma glucose levels, and P-AKTSer473 levels) in HCD group. Importantly, the hepatic carbohydrate response element binding protein (ChREBP) signals (positive hepatocytes, fluorescence intensity, and expression levels) were all significantly elevated by HCD-induced glucose-6-phosphate (G6P) accumulation at 2nd, 4th, 6th, and 8th week (P < 0.05). Compared to 2nd and 4th week, the hepatic ChREBP signals and G6P contents was significantly increased by HCD at 6th and 8th week (P < 0.05). The HCD-induced G6P accumulation was caused by the significantly increased expression of hepatic gck, pklr, and glut2 (P < 0.05) but not 6pfk at 4th, 6th, and 8th week, compared to NCD group. These results suggested that the HCD-induced hepatic lipid deposition was mainly promoted by SREBP1 in earlier stage and by ChREBP in later stage for gibel carp. This study revealed the sequential regulation pathways of the conversion from feed carbohydrate to body lipid in fish. [ABSTRACT FROM AUTHOR]

Simple Summary: The development of novel protein sources plays an important role in improving the economic benefit of aquatic products. The Chlorella vulgaris (C. vulgaris) powder is a novel non-grain single-cell protein with a high reproductive rate, short growth cycle, strong environmental tolerance and easy artificial cultivation. In this experiment, grass carps (initial weight: 20.13 ± 0.09 g) were fed diets by replacing 0% (SM), 25% (X25), 50% (X50), 75% (X75) and 100% (X100) of SM with C. vulgaris for 8 weeks. In conclusion, the C. vulgaris powder replacement of 50% soybean meal was recommended as feed for grass carp. However, the positive effects were apparently weakened when the soybean meal was replaced with high levels of C. vulgaris powder. Chlorella vulgaris (C. vulgaris) powder is a novel non-grain single-cell protein with enormous potential to be a protein source. However, it is poorly studied in aquatic animals. The purpose of the present study was to explore the optimum replacement ratio of C. vulgaris powder and the influence of the substitution of soybean meal with C. vulgaris on grass carp (Ctenopharyngodon idella) in terms of growth performance, intestinal integrity and the microbial community. Five isonitrogenous and isolipidic diets were formulated by replacing 0% (SM, containing 30% soybean meal), 25% (X25), 50% (X50), 75% (X75) and 100% (X100) soybean meal with C. vulgaris. The feeding trial period lasted 8 weeks. At the end of the experimental trial, the X50 group showed higher FW, WGR and PER than the SM group (p < 0.05). The feed conversion ratio (FCR) of the X50 group was significantly lower than that of the SM group (p < 0.05). The X50 group showed the highest value of the goblet cell number, intestinal amylase and trypsin activities when compared with the SM group (p < 0.05). Replacing 50% soybean meal with C. vulgaris improved the intestinal barrier integrity, as evidenced by upregulating zo-1, zo-2 and occluding transcript (p < 0.05), and alleviated oxidative stress by an increased SOD enzymatic activity and transcript level, probably mediated through the Nrf2-keap1 signaling pathway (p < 0.05). Meanwhile, the X50 group enhanced intestinal immunity, as manifested by increased ACP and LZM activities (p < 0.05), and downregulated the tlr-4, tlr-7, tlr-8 and il-6 through the tlr pathway (p < 0.05). The functionally predicting pathways related to the nitrate respiration and nitrogen respiration were observably activated in the X50 group (p < 0.05). The X50 group improved the biological barrier, as manifested by increased Firmicutes and Rhodobacter (p < 0.05). In conclusion, dietary C. vulgaris powder could promote the growth performance of grass carp by restoring intestinal morphology, increasing digestive enzyme activities, improving antioxidant properties and immunity and optimizing the microflora structure. A C. vulgaris powder replacement of 50% soybean meal was recommended as feed for grass carp. [ABSTRACT FROM AUTHOR]

To investigate the effects of different dietary protein sources on the reproductive performance of female broodstock, yellow catfish (Pelteobagrus fulvidraco) were fed with three experimental diets using fishmeal (FM), soybean meal (SBM), and rapeseed meal (RSM) as main protein sources, respectively. Females (initial weight: 64.56 ± 0.45 g) were distributed into 9 net cages for feeding trial. Results indicated that 30% dietary SBM improved the reproductive performance for higher gonadosomatic index (GSI), relative fecundity, total egg production, egg diameter, and hatching rate. In addition, SBM and RSM diets resulted in higher estradiol (E2), vitellogenin (VTG), luteinizing hormones (LH), and lower follicle-stimulating hormone (FSH) and testosterone (T) in plasma (P < 0.05) of female broodstock. Dietary SBM and RSM also resulted in lower mesenteric fat index (MFI), plasma total cholesterol (TC), plasma total bilirubin (T-Bil) contents, and gonadal cortisol concentrations, while dietary SBM downregulated the transcription levels of steroidogenesis-related proteins by negative feedback (P < 0.05). The results demonstrated that dietary SBM and RSM could promote sex steroid hormone and VTG biosynthesis and showed hypocholesterolemic effects. Besides, 30% dietary SBM inclusion could improve the reproductive performance of female yellow catfish broodstock. [ABSTRACT FROM AUTHOR]

This study investigated the potential role of curcumin (CUR) in preventing oxidative stress and ferroptosis induced by ammonia exposure in gibel carp. Experimental fish (initial weight: 11.22 ± 0.10 g, n = 150) were fed diets supplemented with or without 0.5% CUR for 56 days, followed by a 24 h ammonia (32.5 mg/L) exposure. Liver damages (aspartate aminotransferase (AST), alanine aminotransferase (ALT), adenosine deaminase (ADA), and alkaline phosphatase (ALP)) and oxidative stress enzyme activities (reactive oxygen species (ROS), malondialdehyde (MDA); and the content of antioxidant capacity (T-AOC), superoxide dismutase (SOD), and glutathione peroxidase (GPx)) were induced by ammonia stress. The antioxidant capacity was decreased, as indicated by inhibited gene expression of nuclear factor erythroid 2-related factor 2 (nrf2), heme oxygenase-1 (ho-1), catalase (cat), and sod. Ferroptosis was induced by ammonia stress, as suggested by upregulated mRNA levels of nuclear receptor coactivator 4 (ncoa4), transferrin receptor 1 (tfr1), and iron-responsive element-binding protein 2 (ireb2), and downregulated expression of glutathione peroxidase 4 (gpx4), ferroportin (fpn), and ferritin heavy chain 1 (fth1). In addition, both mRNA and protein levels of ferroptosis markers acyl-CoA synthetase long-chain family member 4 (ACSL4) and prostaglandin-endoperoxide synthase 2 (PTGS2) were upregulated, while cystine/glutamate antiporter (SLC7A11) was downregulated. However, liver injury and ferroptosis in fish induced by ammonia could be attenuated by CUR. Collectively, these findings demonstrate that CUR ameliorates oxidative stress and attenuates ammonia stress-induced ferroptosis. This study provides a new perspective on potential preventive strategies against ammonia stress in gibel carp by dietary CUR. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was conducted to evaluate the application of common carbohydrate sources, cornstarch (CS), wheat starch (WS), and wheat flour (WF), to different gibel carp genotypes, Dongting, CASIII, and CASV. The results of the growth and physical responses were analysed by data visualization and unsupervised machine learning. As revealed by a self-organizing map (SOM) and the cluster of growth and biochemical indicators, CASV had superior growth and feed utilization and better regulation of postprandial glucose, followed by CASIII, while Dongting showed a high level of plasma glucose with poor growth performance. CS, WS, and WF were differently utilized by the gibel carp, and WF was associated with greater zootechnical performance based on higher specific growth rate (SGR), feed efficiency (FE), protein retention efficiency (PRE), and lipid retention efficiency (LRE), induced hepatic lipogenesis, increased liver lipids, and enhanced muscle glycogen. Spearman's correlation analysis of the physiological responses indicated that plasma glucose had a significantly negative correlation with growth, feed utilization, glycogen storage, and plasma cholesterol level, and it was positively related to liver fat content in gibel carp. Transcriptional variabilities were observed: CASIII showed increased expression of pklr, which is involved in hepatic glycolysis, and pck and g6p, which are involved in gluconeogenesis. Interestingly, Dongting showed upregulation of genes involved in glycolysis and fatty acid oxidation in muscle. Furthermore, there were numerous interactions between carbohydrate sources and strains for growth, metabolites, and transcriptional control, confirming the existence of genetic polymorphisms in carbohydrate use in gibel carp. Globally, CASV showed relatively better growth and carbohydrate utilization, and wheat flour seemed to be more efficiently utilized by gibel carp. [ABSTRACT FROM AUTHOR]

The present study aimed to evaluate the feasibility of a formulated diet to replace live baits as feed for Siniperca chuatsi. A 2 × 2 factorial design with three replicates was used to investigate the effects of conventional live baits (LB) and a formulated diet (FD) on the growth, muscle nutrition composition, and digestive enzyme activities of S. chuatsi at two growth stages. The results showed that the feed conversion ratio (FCR) in the FD group was significantly lower than that in the LB group. The final body weight (FBW) and weight gain (WG) were not significantly different between the two feeding modes. However, at the juvenile stage, the specific growth rate (SGR) in the FD group was significantly lower than that in the LB group. Muscle moisture, crude protein, and crude lipid contents were not influenced by dietary treatments. There were no significant differences in ∑EAA, ∑NEAA, and ∑AA compositions of the juvenile and adult stages fed the two kinds of diets. At the juvenile stage, histidine (His) content in the FD group was significantly higher than that in the LB group; at the adult stage, cysteine (Cys) content in the FD group was significantly higher than that in the LB group; at both growth stages, Met content in the FD group was significantly lower than that in the LB group. The FD group showed higher levels of ∑SFA, ∑HUFA, ∑n-3PUFA, n-3/n-6, EPA, and DHA than the LB group did, whilst the opposite occurred in the MUFA levels. In addition, fish fed with LB had significantly higher values of pepsin and intestinal trypsin activities in the juvenile fish compared to the FD group, but the activities were not significantly different between the two feeding modes at the adult stage. The activities of stomach and intestine amylase in the FD group were significantly higher than those in the LB group. Overall, these results showed that under long-term feeding conditions, S. chuatsi fed with the artificial diet had no significant difference in muscle crude protein, crude lipid, amino acid composition, and digestive capacity, but showed superiority in the composition of fatty acids such as EPA and DHA levels compared to the live baits group. Therefore, the artificially formulated diet might be a more appropriate feeding approach for sustainable development of the S. chuatsi industry. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was conducted to detect the optimal dietary protein and energy, as well as the effects of protein to energy ratio on growth, for the rare minnow ( Gobiocypris rarus), which are critical to nutrition standardization for model fish. Twenty-four diets were formulated to contain three gross energy (10, 12.5, 15 kJ/g), four protein (20%, 25%, 30%, 35%), and two lipid levels (3%, 6%). The results showed that optimal dietary E/P was 41.7-50 kJ/g for maximum growth in juvenile rare minnows at 6% dietary crude lipid. At 3% dietary lipid, specific growth rate (SGR) increased markedly when E/P decreased from 62.5 kJ/g to 35.7 kJ/g and gross energy was 12.5 kJ/g, and from 75 kJ/g to 42.9 kJ/g when gross energy was 15.0 kJ/g. The optimal gross energy was estimated at 12.5 kJ/g and excess energy decreased food intake and growth. Dietary lipid exhibited an apparent protein-sparing effect. Optimal protein decreased from 35% to 25%-30% with an increase in dietary lipid from 3% to 6% without adversely effecting growth. Dietary lipid level affects the optimal dietary E/P ratio. In conclusion, recommended dietary protein and energy for rare minnow are 20%-35% and 10-12.5 kJ/g, respectively. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was conducted to investigate carbohydrate use in a low-lipid diet between different strains of gibel carp (Carassius gibelio). The wild-type Dongting strain and artificially selected CASIII strain were fed three levels of carbohydrate: 15%, 30%, and 45%, in a low-lipid formulation (4%). The results showed that low-lipid supplementation with high carbohydrate seems to improve the feeding rate (FR) and specific growth rate (SGR), while it did not result in hyperglycaemia in gibel carp. Transcriptional regulation was slightly affected by carbohydrate levels; only hepatic pfk expression was more increased in the 30% and 45% carbohydrate diets than in the 15% carbohydrate diet (p < 0.05). Regarding the strains, CASIII obtained higher growth performance by having higher FR and SGR than Dongting (p < 0.05). Relatively higher glycaemia was found in CASIII, and it was coupled with increased plasma triglycerides and insulin (p > 0.05). Enhanced gene expression of pk involved in glycolysis and decreased mRNA levels of pepck in gluconeogenesis were also observed in CASIII (p < 0.05). There were strong strain ∗ diet interactions of gene expression involved in lipogenesis, and Dongting had higher mRNA levels of srebp-1, acly, and fas when fed carbohydrate at 45% (p < 0.05). In conclusion, the tolerant level of carbohydrates in a low-lipid diet could be up to 45% for gibel carp by an improvement of growth and noninducement of postprandial plasma glucose. CASIII had a better ability to use dietary carbohydrates for growth with active glycolysis and restrained gluconeogenesis, and Dongting had more potential in lipid metabolism in response to carbohydrate intake. [ABSTRACT FROM AUTHOR]

An investigation into the replacement of soybean meal (SBM) with cottonseed protein concentrate (CPC) in the diet of grass carp feed (Ctenopharyngodon idellus) was carried out. During a 56-day feeding trial, 750 grass carp were fed five experimental diets (isonitrogenous and isolipidic) with different levels of CPC: SBM (control group), CPC25, CPC50, CPC75, and CPC100, corresponding to dietary SBM replacements levels of 0%, 25%, 50%, 75%, and 100%. The results showed that dietary CPC inclusion significantly increased FW, WGR, and PER (P < 0.05) except CPC100 groups, which did not differ with SBM group (P > 0.05). FCR was remarkably increased when SBM replacement levels reached up to 100% (P < 0.05). Based on broken-line regression analysis of WGR against the dietary replacement of SBM with CPC, the optimal replacement level of SBM with CPC was estimated to be 75.11% for juvenile grass carp. Muscle texture parameters hardness, gumminess and chewiness were apparently elevated (P < 0.05), demonstrated an improved flesh quality followed CPC added. The CPC inclusion groups showed significantly higher serum IgM, C3 amd C4 contents, as well as ACP and AKP activities than SBM group except CPC100 groups (P < 0.05). The hepatic antioxidant capacity was enhanced followed CPC inclusion verified at enzymatic and transcriptional levels (P < 0.05). The intestinal inflammation was relieved evidenced by the down-regulated il-β , il-6 and tnf-α expressive abundance mediated through NF-κB pathway (P < 0.05). Additionally, the intestinal mucosal barrier function was enhanced by the up-regulation of tight junction proteins (occludin , claudin12 , zo-1 , and zo-2). The intestinal lipase and trypsin activities in CPC50 and CPC75 and intestinal folds height in CPC25, CPC50 and CPC75 were advanced (P < 0.05). The gut microbiota revealed no significant differences in the alpha diversity indices across treatments (P > 0.05). While the key bacteria of Aeromonas in the CPC100 group was increased leading intestinal dysbacteriosis. Besides, the ME1 of the microbial network has a negative correlation with pro-inflammatory gens and a positive correlation with antioxidant gens and tight linking proteins (P < 0.05). Summarily, CPC could partially replace SBM with positive influences on growth, antioxidant capacity, immunity, and intestinal microbiota in grass carp. • CPC could replace 75% of SBM with positive influences on growth, antioxidant capacity, immunity and intestinal health in juvenile grass carp. • The complete replacement of SBM with CPC impaired intestinal health. • The study provided a reference for the application of CPCe instead of SBM in aquatic animals. [ABSTRACT FROM AUTHOR]

Tributyrin (TB) has applications as a growth and intestinal health promoter for animals. A 10‐week feeding trial was conducted to evaluate the application of TB to relieve the negative effects induced by high cottonseed and rapeseed meal (CRM) in juvenile grass carp (Ctenopharyngodon idellus; initial weight 9.59 ± 0.01 g). Grass carp were fed a normal fish meal (FM) diet (positive control [PC], 50 g/kg FM, 340 g/kg CRM), high CRM diet (T0, 20 g/kg FM, 540 g/kg CRM) or a T0 diet supplemented with 500 (T500), 1000 (T1000) and 1500 (T1500) mg/kg TB. The results showed that (1) grass carp fed diet T0 displayed the poorest growth (p <.05), whilst no significant differences in growth performance were observed in those fed diets PC and T1000. (2) Complement 3, glutathione peroxidase and superoxide dismutase levels in the T0 group were significantly lower (p <.05) than those in the PC group. The immune indices of fish fed the 1000 or 1500 mg/kg TB diet were significantly higher (p <.05) than those of fish fed the T0 diet, whilst there was no significant difference with PC group. (3) Compared with that of the T0 group, pro‐inflammatory cytokine (il‐6, il‐8, nf‐κb and tlr‐4) expression in the 1000 mg/kg tributyrate group was significantly downregulated, whilst the expression of anti‐inflammatory cytokines (il‐10 and thf‐β) and intestinal tight junction proteins (zo‐1, zo‐2, claudin‐b, claudin‐c and occludin) was significantly upregulated (p <.05). In conclusion, high CRM diets induced negative effects on grass carp, and dietary TB supplementation promoted growth, improved antioxidant capacity and enhanced intestinal barrier function of grass carps. And the optimum supplemental level of TB was 1000 mg/kg. [ABSTRACT FROM AUTHOR]

To investigate the effects of tea polyphenols (TPs) on the growth and carbohydrate metabolism of grass carp (Ctenopharyngodon idella), 0 (control group), 250, 500, 1000, 2000, and 4000 mg kg−1 TPs were added to the basal diet and fed to grass carps for 8 weeks. The results show that 500 mg kg−1 group exhibited the significantly highest feed conversion efficiency (FCE) and specific growth rate (SGR) (p <.05) and significantly higher activities of pyruvate kinase (PK), lactate dehydrogenase (LDH), malate dehydrogenase (MDH) and succinate dehydrogenase (SDH) (p <.05). The livers of the control group and 500 mg kg−1 group were subjected to RNA‐Seq, and the expressions of glycogen phosphorylase (PYG) and sucrase‐isomaltase (SI) genes were upregulated, while that of glucose‐6‐phosphatase (G6PC) was downregulated, and these promoted glycogen catabolism. The expressions of glucokinase (GK), PK, 6‐phosphofructokinase (PFK), glucose‐6‐phosphate 1‐dehydrogenase (G6PD) and fructose‐bisphosphate aldolase A (ALDOA) genes were upregulated to promote glucose catabolism. The results indicate that 500 mg kg−1 TPs could upregulate the expressions of some genes that promote carbohydrate decomposition, increase the activities of carbohydrate decomposition enzymes and enhance the utilization of carbohydrates, thereby improving the FCE and SGR. [ABSTRACT FROM AUTHOR]

The cyanobacterium Arthrospira platensis is regarded as a potential future source of food for humans due to its superior nutritional value compared with many conventional crops. An 8-week feeding trial was conducted to evaluate nutritional and pigmentation effects of whole A. platensis, defatted A. platensis and its lipid extracts in diets for the yellow catfish Pelteobagrus fulvidraco. Four percent whole A. platensis (AP4), 0.4% A. platensis lipid extracts (AL0.4), and 4% defatted A. platensis (AR4) were used as experimental diets, and a diet without any A. platensis was as the control diet (AP0). The AP4 and AL0.4 groups had no effects on the growth performance and feed utilization in yellow catfish; however, the AR4 group was significantly lower than the AP0 group in terms of specific growth rate and feed efficiency (P < 0.05). AP4 and AL0.4 groups significantly increased the body protein of fish (P < 0.05). The skin color was significantly improved in the AP4 and AL0.4 groups, as well as the fish skin and plasma lutein contents (P < 0.05). Correlations between skin color and the lutein contents in liver and muscles were weak, whereas the correlations between skin color and the lutein contents in skin and plasma were significant and strong. The results suggest that whole A. platensis and its lipid extracts can be functional additives to improve whole body protein and skin color of fish, while defatted A. platensis showed no advantage in yellow catfish diets. [ABSTRACT FROM AUTHOR]

Gelatin and carboxymethyl cellulose (CMC) were often used as binders due to their binding ability. To investigate the effects of gelatin and CMC supplementation on feed quality, intestinal ultrastructure and growth performance of gibel carp, six pelleted feed were formulated: control; supplemented with gelatin (10 g/kg, 30 g/kg and 50 g/kg); and supplemented with CMC (10 g/kg and 30 g/kg). Increased gelatin supplementation levels reduced feed solubility and pellet softening (p <.05) and decreased chemical oxygen demand in the surrounding water after pellets were immersed (p <.05). Increased levels of gelatin supplementation enhanced digesta viscosity and reduced intestinal microvilli length and digestive enzymes activities (chymotrypsin and amylase; p <.05) of fish. Fish‐fed diets supplemented with 30 g/kg gelatin had higher levels of plasma total free amino acids and glucose (p <.05) than fish fed 10 g/kg and 50 g/kg gelatin. Feed supplemented with 10 g/kg CMC were softer than those supplemented with 30 g/kg CMC (p <.05); fish‐fed diets supplemented with 10 g/kg CMC had longer intestinal microvilli (p <.05) than fish fed 30 g/kg CMC. Thus, our results indicated that either gelatin or CMC is applicable to supplement in the feed for improving feed quality and without negative effect on growth performance of gibel carp. [ABSTRACT FROM AUTHOR]

The current study was conducted to evaluate the effect of dietary soy isoflavones (SI) on growth performance, antioxidant status, immune response and resistance to Aeromonas hydrophila in juvenile grass carp (Ctenopharyngodon idella). Six diets were formulated to contain 0 (control), 10, 50, 100, 500 or 1,000 mg SI per kg feed. Each diet was randomly allotted to triplicate net cages, and each net cage was stocked with 30 fish. The fish were fed one of the experimental diets to satiation twice per day for 60 days. The results showed that the WGR and DGC of the 500 mg/kg SI‐supplemented group were significantly higher than those of the non‐SI‐supplemented group (p <.05). Serum LZM and IgM activities in the SI‐supplemented groups were improved compared to the control group. SOD and GSH‐Px levels of fish fed the diet containing 500 mg/kg SI were significantly enhanced compared to those of fish fed the control diet (p <.05). Additionally, serum CAT, GSH‐Px and AKP activities in 50, 100 and 500 mg/kg SI‐supplemented groups were significantly higher than that in the control group (p <.05). The expression of most immune‐related genes (including IFN‐γ2, TNF‐α, M‐CSF2, IL‐6, IL‐12p40 and IL‐4) was significantly affected by dietary supplementation of SI. The group fed with 500 mg/kg SI had the highest 7‐day cumulative survival rate after challenge test (p <.05). The current results revealed that dietary inclusion of SI could improve the immune response and resistance against A. hydrophila and the supplementation level is suggested to be 500 mg/kg diet. [ABSTRACT FROM AUTHOR]

Insulin-sensitive lipogenesis dominates the body lipid deposition; however, nonalcoholic fatty liver disease (NAFLD) develops in the insulin-resistant state. The regulation mechanism of insulin resistance-driven NAFLD remains elusive. Using zebrafish model of insulin resistance (ZIR, insrb −/−) and mouse hepatocytes (NCTC 1469), we explored the regulation mechanism of insulin resistance-driven hepatic lipid deposition under the stimulation of carbohydrate diet (CHD). In ZIR model, insulin resistance induced hyperlipidemia and elevated hepatic lipid deposition via elevating the gene/protein expressions of lipogenic enzymes, that was activated by carbohydrate response element binding protein (ChREBP), rather than sterol regulatory element binding proteins 1c (SREBP-1c). The metabolomic analysis in zebrafish and silencing of chrebp in mouse hepatocytes revealed that the increased hepatic frucotose-6-phosphate (F6P) and glucose-6-phosphate (G6P) promoted the ChREBP-mediated lipid deposition. We further identified that F6P alone was sufficient to activate ChREBP-mediated lipid deposition by a SREBP-1c-independent manner. Moreover, we clarified the suppressed hepatic phosphofructokinase/glucose-6-phosphatase functions and the normal glucokinase function preserved by glucose transporter 2 (GLUT2) manipulated the increased F6P/G6P content in ZIR. In conclusion, the present study revealed that insulin resistance promoted hepatic lipid deposition via the F6P/G6P-mediated ChREBP activation. Our findings deciphered the main regulation pathway for the liver lipid deposition in the insulin-resistant state and identified F6P as a new potential regulator for ChREBP. [Display omitted] [ABSTRACT FROM AUTHOR]

High cottonseed meal diets can reduce the growth and cause intestinal damage of aquatic animals. Sanguinarine is a plant alkaloid with demonstrated anti-inflammatory. Howerve, its role in the negative effects caused the high cottonseed meal diet is unclear. Herein, an eight-week feeding trial was conducted to evaluate the effects of sanguinarine supplementation in a high cottonseed meal diet on the growth and intestinal health (such as inflammation, physical barrier, oxidative stress, and microbiota of Ctenopharyngodon idellus , providing a theoretical basis for the application of sanguinarine in cottonseed meal diets. A basal diet of 0% cottonseed meal was designated as the control diet (CON). Diets (44% cottonseed meal) supplemented with four sanguinarine (0, 300, 600, and 1200 μg/kg; designated as the CM, CMLS, CMMS, and CMHS, respectively) were prepared. There were 3 replicates per group and 50 fish per replicate. One-way ANOVA and Duncan's multiple comparisons of the means were used in this experiment. The results showed that feeding grass carp with CM obviously reduced the growth, impaired the intestinal physical and immune barrier function, and disrupted the microbiota balance of the intestine. Compared with the CM group, supplemented sanguinarine markedly improved the growth performance, serum AKP, C3, and IgM levels of grass carp, and enhanced intestinal antioxidant capacity (gpx1 , cat , and gsto expression levels obviously up-regulated and ROS and MDA contents reduced). Sanguinarine observably down-regulated the expression levels of il-1β , il-8 , il-6 , and tnf-α and up-regulated the expression levels of il-10 , il-15 , and tgf-β1 by inhibiting NF-κB signaling molecules, thereby alleviating intestinal inflammation caused by a CM diet. Additionally, sanguinarine observably down-regulated claudin-12 and claudin-15 gene expression and up-regulated zo-1 and occludin gene expression by inhibiting MLCK signaling molecules. Besides, compared with the CM group, the α-diversity indices and abundances of Proteobacteria , Actinobacteria , and Planctomycetes in the CMMS group were markedly reduced, while the abundance of Firmicutes was the opposite. In conclusion, the CM diet negatively impacted grass carp, and supplemented sanguinarine can improve growth, enhance intestinal antioxidant ability, alleviate intestinal barrier damage, and ameliorate intestinal microbiota homeostasis. • High cottonseed meal diets had negative effects on growth and intestinal of grass carp. • Sanguinarine improved growth and the homeostasis of intestinal microbiota in grass carp fed high cottonseed meal diets. • Adding sanguinarine to high cottonseed meal diets enhanced the intestinal physical barrier through MLCK. • Adding sanguinarine to high cottonseed meal diets improved the intestinal immune barrier by inhibiting NF-κB. [ABSTRACT FROM AUTHOR]

Spirulina, Arthrospira platensis , contains high levels of protein and lutein. To evaluate nutritional, pigmentation, and antioxidation effects of A. platensis , a total of 900 juvenile yellow catfish (Pelteobagrus fulvidraco) were divided into 18 tanks (3 tanks/treatment, 50 fish/tank) and fed a diet supplemented with A. platensis for 50 days. A. platensis was used in quantities of 0, 57.6, 115.1, 172.7, 230.3, and 287.9 g kg−1 for experimental diets to replace fishmeal protein at levels of 0 (AP0), 20% (AP20), 40% (AP40), 60% (AP60), 80% (AP80), and 100% (AP100). Results revealed that substituting up to 80% of fishmeal by A. platensis biomass did not have a negative effect on fish growth, feed utilization, or apparent digestibility. However, significantly lower growth rates were observed when 100% of the fishmeal was substituted (P < 0.05). A. platensis replacement groups led to an increase in skin yellowness and dose-dependent enrichments of total lutein in dorsal skin, abdominal skin, and liver tissues (P < 0.05). There were similar enhancements observed in glutathione concentrations and glutathione peroxidase activities in plasma and liver (P < 0.05). Analyses based on lutein concentration between abdominal skin and experimental diets revealed that the optimal substitution amount was 72.03% (207.4 g kg−1 of A. platensis), which could ensure growth and pigmentation in yellow catfish. • Arthrospira platensis can be used as alternative source of fish meal in yellow catfish diets. • Arthrospira platensis could increase the lutein contents to enhance the yellowness in skin of yellow catfish. • The quality was improved of yellow catfish because the A. platensis enhanced the pigmentation and antioxidant abilities. [ABSTRACT FROM AUTHOR]

High-throughput sequencing of the 16S rRNA gene of microbial communities was used to investigate how biofloc technology (BFT) improved water quality and fish yield in freshwater pond aquaculture. Three treatments included conventional treatment (CT), biofloc treatment (BT) and biofloc systems augmented with floc-forming bacterium (Zoogloea resiniphila MMB) treatment (BZT). The feeding trial lasted for 8 weeks with triplicate groups of cyprinid species in nine enclosures, which were placed in an outdoor pond to simulate a real aquaculture environment. Biofloc was generated by adding organic carbon and continuous aeration, which resulted in reducing dissolved nitrogen from 22% to 14% and sedimentary nitrogen from 49% to 5% and increasing nitrogen accumulation in biofloc and fish biomass. Nitrogen content in fish biomass increased from 28% in a CT to 42% when BFT was applied. Changes in the bacterial community and stimulation of biofloc formation played a central part in transferring nitrogen from remaining food, excreta and feces to bacteria and fish biomass. Z. resiniphila MMB did not outcompete indigenous communities and had no impact on floc formation by direct addition to the pond. Filamentous bacteria comprised the major structure of biofloc, while the proportion of zoogloea-forming microorganisms was very low. The proportion of aerobic heterotrophic microorganisms increased in both BFT treatments. Actinobacteria promoted the formation of floc and could have secondary benefits of protecting against fish pathogens, such as Aeromonas sp. , though may increase the accumulation of off-flavor in the water and fish tissue. Display Omitted • Supplying carbohydrate and air in pond improved biofloc formation and water quality. • Dietary nitrogen recovery in fish increased from 28% to 42% with biofloc technology. • Filamentous bacterium formed the major structure of biofloc then eaten by fish. • Biofloc technology may protect against pathogens and cause earth odor accumulation. • No effects on biofloc were found with bioaugmentation of Z. resiniphila MMB. [ABSTRACT FROM AUTHOR]

Abstract The effects of guar gum, when used as a feed binder, on growth performance, digestive enzyme activity, and intestinal histology in gibel carp were evaluated. Four isonitrogenous and isoenergetic diets were formulated and supplemented with 0%, 1%, 3%, and 5% guar gum. The different diets were fed to triplicate groups of gibel carp (mean initial weight: 5.60 ± 0.003 g) for 51 d. Feed supplemented with 1% guar gum had no effect on specific growth rate, feed efficiency, condition factor, or protein retention efficiency as compared to the control group; this level of supplementation increased microvillus length in the distal intestine and increased fecal viscosity. In contrast, 5% guar gum supplementation increased feed hardness, decreased feed water solubility, and decreased total nitrogen content in the soaking water after 3-h immersion. However, 5% guar gum supplementation decreased feed intake and induced distal intestine damage, as indicated by shorter microvilli as compared to the control group. Supplementation with 5% guar gum also decreased the activity levels of intestinal digestive enzymes (chymotrypsin, amylase, and alkaline phosphatase) and decreased plasma total cholesterol and triglycerides, and finally reduced fish growth. Dietary supplementation with 1% guar gum increased fecal viscosity sufficiently to decrease water pollution, without significant adverse effects on growth performance, feed utilization, and intestinal microstructure in the gibel carp. Highlights • Diets supplemented with 5% guar gum decreased gibel carp growth. • Diets supplemented with 5% guar gum damaged gibel carp intestinal structure. • Optimal guar gum supplementation level in the gibel carp was 1%. [ABSTRACT FROM AUTHOR]

Many fish species experience natural periods of starvation; however, mobilization of energy sources may vary. To elucidate the mechanism underlying energy utilization and metabolic adaptation to food deprivation in gibel carp ( Carassis auratus gibelio var. CAS III), fish (initial body weight: 111.13 ± 0.65 g) were starved for 0 d, 1 d, 2 d, 7 d, and 21 d, respectively. After seven days of food deprivation, plasma glucose levels significantly decreased, whereas plasma free fatty acids levels significantly increased. Liver glycogen levels in the group starved for 7 d significantly decreased, whereas muscle glycogen levels decreased in the group starved for 21 d, suggesting that glycogen in the liver is first utilized to provide energy than glycogen in the muscle. The transcriptional levels of glucose transporter type 2 (GLUT2) in the liver were upregulated during starvation. No changes in the mRNA levels of glycolytic enzymes such as glucokinase (GK) and 6-phosphofructokinase (6PFK) were observed in the liver. Gluconeogenic potential increased with starvation, possibly for blood glucose homeostasis, as indicated by the enhanced mRNA levels of gluconeogenic enzymes, including glucose-6-phosphatase (G6Pase), fructose 1,6-bisphosphatase (FBPase), and phosphoenolpyruvate carboxykinase (PEPCK). The observation of a decrease in liver triglycerides content and the enhanced expression of hormone-sensitive lipase (HSL) and lipoprotein lipase (LPL) suggests the mobilization of lipid reserve in the liver. Enhanced fatty acid oxidation as indicated by the upregulated mRNA carnitine palmitoyl transferase 1 isoform a (CPT1a) and acyl-CoA oxidase 3 (ACO3) levels in the liver suggests that fatty acids are catabolized to provide energy during starvation. Sterol regulatory element binding protein 1 (SREBP1), ATP citrate lyase (ACLY), acetyl-CoA carboxylase (ACC), and fatty acid synthase (FAS) were downregulated during starvation in both liver and muscle, indicating suppressed lipogenesis. [ABSTRACT FROM AUTHOR]

Aquaculture needs effective antibiotic alternatives to control outbreaks of intestinal inflammation, as well as liver inflammation and metabolic disorder caused by enteritis. Specific metabolites have been shown to have immunomodulatory effects by the field of immunometabolism. As derivatives of the Krebs cycle metabolites, the itaconate and fumarate, 4-octyl itaconate (OI) and dimethyl fumarate (DMF) have recently attracted a lot of interest as anti-inflammatory medications. To evaluate the effects of oral administration of OI and DMF on fish growth and health, an 8-week feeding experiment followed by induction of enteritis with 2,4,6-trinitrobenzene sulfonic acid (TNBS) was carried out in gibel carp. The results showed that dietary 0.1%DMF improved the growth performance, and 0.1%OI up-regulated the abundance of beneficial intestinal microbiota. Both of OI and DMF alleviated intestinal inflammation by increasing intestinal anti-inflammatory cytokines, and relieved enteritis-induced hepatopancreas injury by inhibiting glycolysis both in vivo and in vitro. The 0.1%DMF also enhanced the tight junction and altered the microbiota to maintain the intestinal barrier. Collectively, dietary supplementation with 0.1% OI and DMF might be novel strategies to prevent enteritis and intestinal inflammation-induced hepatopancreas damage in gibel carp. [Display omitted] • Dietary 0.1%DMF improved the growth performance. • Both 0.1% OI and 0.1% DMF alleviated TNBS-induced intestinal inflammation in gibel carp. • DMF enhanced the tight junction and altered the microbiota to maintain the intestinal barrier. • OI and DMF alleviated enteritis-induced liver injury by inhibiting glycolysis both in vivo and in vitro. [ABSTRACT FROM AUTHOR]

Abstract Hyperglycemia in type 2 diabetes results from an inability of insulin to regulate gluconeogenesis. To characterize the role of the insulin/insulin receptor pathway in glycometabolism and type 2 diabetes, we created a zebrafish model in which insulin receptors a and b (insra and insrb) have been ablated. We first observed that insra and insrb were both expressed abundantly during embryonic development and in various adult tissues. Increased expression of insulin and number of β-cells were observed in insra −/−/ insrb −/− fish together with higher glucose in insra −/−, insrb −/−, or insra −/−/ insrb −/− fish, indicating that insra and insrb were knocked out effectively. However, compared to the wild-type fish, insra −/−/ insrb −/− fish died between 5 and 16 days post-fertilization (dpf) with severe pericardial edema and increased level of cell apoptosis, which was not induced by increased total body glucose content. Increased gluconeogenesis and decreased glycolysis were also observed in both single and double knockout fish, but no mortality or malformation was observed in single knockout fish. Given the importance of insulin receptors in glucose homeostasis and embryonic development, transcriptome analysis was used to provide an important model of defective insulin signaling and to study its developmental consequences in zebrafish. The results indicated that both insra and insrb played a pivotal role in glucose metabolism and embryonic development, and insra was more critical than insrb in the insulin signaling pathway. [ABSTRACT FROM AUTHOR]

It is well known that most fish would prefer to use body lipid stores for energy expenditure when receiving a long-term food restriction. However, the mechanism of this is still not clear. In the present study, a growth experiment was carried out to investigate the effects of food restriction on growth performance, gene expression related in regulation of lipid metabolism and food ingestion in grass carp ( Ctenopharyngodon idellus ). Four rations, satiation (S), 80% S, 60% S and 40% S, were adopted in this study. Each treatment was randomly assigned to triplicate net cages of 15 fish (177.3 ± 3.3 g) per cage. The experiment lasted for 49 days at 30.0 ± 3.0 °C. The experimental results showed that a significant increase in feeding rate and weight gain was found in grass carp with the increased ration level. The body lipid and energy content of the grass carp exhibited a significant decrease when receiving food restriction. The transcriptional levels of the genes involved in lipogenesis ( srebp -1 c , fas , pparγ ) were down-regulated at the rations of food restriction. The relative expression of hepatic fas (fatty acid synthetase) and srebp -1 c (sterol regulatory element-binding protein 1c) in the fish at satiation were significantly higher than the restricted-fed groups. Similarly, the expressions of hepatic pparγ (peroxisome proliferator-activated receptor-γ) in the fish at the ration of satiation and 80% S were significantly higher than the group at the low ration of 40% S. However, the expression of hepatic cpt -1 a (carnitine palmitoyl transferase I) involved in fatty acid β-oxidation in fish was significantly up-regulated when receiving food restriction. Other hepatic lipolysis genes of pparα (peroxisome proliferators-activated receptor α) and hl (hepatic lipase) didn't show any significant changes in restricted-fed fish. The transcriptional levels of hepatic leptin and hypothalamus pomc (proopiomelanocortin) were significantly down-regulated in fish fed with restricted rations. But the hypothalamus npy (neuropeptide Y) and lepr (leptin receptor) had no change. The present results indicated that a long-term food restriction could cause less accumulation of lipid and could be through a way of down-regulating lipogenesis genes and up-regulating lipolysis genes. Long-term restriction could also activate the appetite of grass carp by down-regulating some anorexigenic genes. Statement of relevance Food restriction for some time could lead to a suitable lipid storage, in case of accumulation of fatty acid profile and lipid, in cultured grass carp. [ABSTRACT FROM AUTHOR]

An 8-week trial was performed to investigate the effects of replacing soybean meal (SBM) by sunflower meal (SM) or enzymolysis sunflower meal (ESM) on the growth, lipid metabolism, and intestinal health of Ctenopharyngodon idellus. Compared with SM, the small peptides and amino acids contents in ESM increased, while the crude fiber decreased. Seven isonitrogenous and isolipid diets (SM0, SM25, SM50, SM75, SM100, ESM75, and ESM100) were prepared for SM to replace 0, 25, 50, 75, 100% SBM and ESM to replace 75 and 100% SBM, respectively. The results showed that with an increasing proportion of SM instead of SBM, weight gain rate (WGR) of grass carp showed a decreasing trend, while feed conversion ratio (FCR) showed a rising trend, and significantly changed in the SM75 and SM100 groups. WGR in the ESM75 group was significantly increased compared with the SM75 group, and there was no statistical difference with the SM0 group. Replacing 75% and 100% SBM with ESM was beneficial to lipid metabolism, which was mainly manifested in decreased serum low-density lipoprotein, triglyceride, and total cholesterol contents, and significantly down-regulated acetyl-CoA carboxylase (acc), fatty acid synthase (fas) and sterol regulatory element binding protein 1 (srebp1) gene expression in liver. Replacing 75% and 100% SBM with SM resulted in intestinal oxidative damage (reactive oxygen species and malondialdehyde contents increased; superoxide dismutase, glutathione reductase, and glutathione peroxidase activities decreased) and disrupted intestinal physical and immune barrier functions (claudin15 , myosin light chain kinase (mlck), interleukin-1β, 6, 12β (il-1β , il-6 , il-12β), tumor necrosis factor-α (tnf-α), and nuclear factor-κB (nf-κb) gene expression up-regulated; zonula occluden 1, 2 (zo1 , zo2), transforming growth factor β1 (tgf-β1), and il-10 gene expression down-regulated), while substitution of 75% and 100% SBM by ESM alleviated oxidative damage and improved intestinal immune and physical barrier functions. In addition, the α-diversity index and the abundances of Erysipelatoclostridium and Bacteroides in the ESM75 group were significantly increased compared with the SM0 and SM75 groups. In conclusion, the replacement proportion of SBM with SM should not exceed 50%, otherwise it will lead to reduced growth, lipid deposition, intestinal health damage and intestinal microbiota disorder. However, the replacement of 75% SBM with ESM has no negative effect on grass carp, and it improved lipid metabolism and intestinal health compared with substitution of SBM with SM. • Substitution of sunflower meal (SM) for soybean meal should not exceed 50%. • Substitution of 75% and 100% soybean meal with SM had negative effects on growth and lipid metabolism of grass carp. • Higher replacement level (≥75%) induced intestinal oxidative stress and impaired barrier function of grass carp. • Substitution of 75% soybean meal with enzymolysis SM had no negative effect on grass carp. [ABSTRACT FROM AUTHOR]

Cottonseed meal (CM) was used at up to 36.95% content in the diet (replacing 60% of dietary fish meal protein) without any negative eff ects on growth performance of pre-adult grass carp (initial body weight, 761 g) under outdoor conditions. A culture trial was conducted in net cages installed in a large concrete pond. Seven isonitrogenous and isoenergetic diets containing a gradient of CM concentrations (0, 12.2%, 24.4%, 36.6%, 48.8%, 54.8%, and 61.0%) as replacement for dietary fish meal protein (0, 20%, 40%, 60%, 80%, 90%, and 100%) were formulated. Dietary non-resistant starch (from maize) was inverse to dietary CM. Growth performance and feed utilization of fish fed the diets containing CM replacing 0-40% fishmeal protein were not aff ected after the 6-week feeding trial. Accumulation of hepatopancreatic total gossypol in the hepatopancreas was significantly correlated with free gossypol content in the diets (HTG=88.6+1.5×DFG, R=0.89, P<0.05). Intestinal α-amylase and γ-glutamyl transpeptidase activities rose along with increasing dietary CM level. The structure of the mid-intestinal tissues and the ultrastructure of the enterocyte microvilli were normal when dietary CM was <36.6% (60% protein replacement). Increasing dietary CM content increased serum alanine aminotransferase levels but decreased serum alkaline phosphatase, cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, and albumin ( P<0.05). [ABSTRACT FROM AUTHOR]

High mortalities and suppressed immune functions of farmed fish over winter are the universal problems in aquaculture. It is necessary to improve the immune response and disease resistance in the overwintering fish. A recent study suggested that repeated handling increased innate immune mechanisms and disease resistance in Senegalese sole. Therefore, the present study evaluated the hypothesis that appropriate repeated handling could compromise the immune depression and increase the disease resistance in gibel carp over winter. The experiment was executed in field net cages (2 m × 2 m × 2 m) from Dec. 4, 2012 to Apr. 2, 2013. Three cages with 50 fish per cage were randomly designed as the control group and did not receive any interfere over winter. The other three cages received repeated handling with an air exposure for 5 min every week during the experiment. Fish were not fed over winter. At the end of the trial, fish were challenged with Aeromonas hydrophila at a dose of 1.5 × 10 8 CFU ml −1 . The results showed that no significant difference of final body weight was found between groups. The spleen and kidney somatic index increased in the control fish after bacterial challenge and showed a rising trend but not a statistical change in repeated handled fish. Plasma cortisol levels significantly increased in the control fish at 6 h post bacterial challenge and then declined. However, repeated handled fish did not show any significant change in plasma cortisol levels after challenge. The reduced inducement of heat shock protein 70 (HSP70) expressions by repeated handling was found in gibel carp post bacterial challenge. After overwintering, the repeated handled fish exhibited increased catalase (CAT) and superoxide dismutase (SOD) activities. Enhanced plasma CAT activities and reduced plasma malondialdehyde (MDA) contents were found in repeated handled fish over time against invading bacteria. Up-regulation of myeloid differentiation primary response gene 88 (MyD88) and interleukin 11 (IL11) was observed in repeated handled fish over time after bacterial challenge. The overexpression of IL11 was significantly reduced by repeated handling against invading bacteria compared to the control group. The present results implied that a MyD88-dependent signaling pathway was involved in the innate immune responses of gibel carp by repeated handling over winter against invading bacteria. [ABSTRACT FROM AUTHOR]