Search

Herpesviral hematopoietic necrosis disease caused by cyprinid herpesvirus 2 (CyHV-2) results in huge economic losses for the gibel carp (Carassius auratus gibelio) aquaculture industry. A vaccination strategy is a feasible method to prevent CyHV-2 infection and the resulting economic losses. In this study, inactivators (including β-propiolactone, formaldehyde and binary ethylenimine) were used to prepare an inactivated vaccine. The optimal inactivated CyHV-2 vaccine (0.2% β-propiolactone inactivates CyHV-2 for 48 h) mixed with β-glucan, anisodamine, chitosan, and astragalus polysaccharide (APS) adjuvants were injected into gibel carp. The β-glucan and APS combined with inactivated vaccine significantly improved the relative immune protection rate of gibel carp against CyHV-2 infection. The highest specific antibody levels in β-glucan and APS groups were found in serum by ELISA assay and antibody neutralization titer. Furthermore, adjuvant addition groups produced better results for lysozyme, total superoxide dismutase, and complement C3 in serum. β-glucan and APS combined with vaccine treatment effectively enhanced mRNA expressions of important immune genes (IL-1β, IgM, IL-2 and IFN-γ2). Minimal tissue lesions (gill, spleen, and head kidney) and virus replication were seen in the β-glucan and APS groups by histopathological examination and expression analysis of CyHV-2 TK gene. These results indicated that the combination of inactivated vaccine and adjuvant β-glucan or APS is an effective method against CyHV-2 infection and provided a case study reference for prevention of fish viral diseases using inactivated vaccines.

Carassius auratus gibelio, commonly known as crucian carp, is the main species of freshwater aquaculture in China. Due to high-density aquaculture and environmental pollution, various diseases continue to emerge, especially the diseases caused by pathogenic bacteria have seriously restricted the development of freshwater aquaculture. Among these, Aeromonas hydrophila (AH) is the one of the most serious fish disease causing economic losses among fish farmers. An in-depth understanding of the crucian carp's immune system and its genes involved in the response to bacterial infection is necessary for disease control. In this study, the breeding period was divided into the control group (C group) and the Bacillus licheniformis (B. licheniformis) group (BL group). After 4 weeks of culture, the crucian carp was infected with AH and divided into the control group (Cg group) and the B. licheniformis group (BLg group). After the 72-h challenge, the Illumina-based paired-end sequencing approach to analyze the transcriptome profile of the crucian carp gut following AH infection. A total of 472.05 million valid reads were found from the four intestinal samples and 403.18 million reads were mapped successfully, of which 243.34 million were unique. About GO enrichment analysis, significant differentially expressed genes (DEGs) were more in biological process (406 DEGs), regulation of transcription, DNA-templated (345 DEGs), and signal transduction (304 DEGs). In the cell components, membrane (1913 DEGs) and integral component of membrane (1789 DEGs) had a higher number of significantly different genes. In the molecular function, metal ion binding (780 DEGs), ATP binding (535 DEGs), transferase activity (491 DEGs), and nucleotide binding (482 DEGs) have a large number of significantly different genes. Regarding the KEGG enrich analysis section, this study is arranged in ascending P-value order, andthe most significant signaling paths are lysosome, glucose metabolism, cycline cycline receiver interaction, and phagosome. Among them, the cycline cycline receiver interaction has the highest difference in significant genes. In addition, 5 immune-related genes were selected for real-time fluorescence quantitative PCR analysis to verify the RNA-seq data, and the results showed that the expression of all 5 genes was upregulated, which was consistent with the results of our RNA-seq analysis. After analysis, it was found that B. licheniformis can alleviate the inflammatory response and protect the fish body. Our results provide a reference for further analysis of the antagonism and mitigation mechanism of B. licheniformis against AH. [ABSTRACT FROM AUTHOR]

An 88-day feeding trial was conducted to evaluate the effects of dietary inosine 5′-monophosphate (5′-IMP) on the growth performance and salinity and oxidative stress resistance in the juvenile gibel carp CAS III (Carassius auratus gibelio; initial body weight: 7.48 g). Four isonitrogenous and isoenergetic diets containing exogenous 5′-IMP were formulated. P1, P2, P3 and P4 were diets containing 5′-IMP at four concentrations (0, 1, 2 and 4 g kg−1). The four diets were randomly allotted to triplicate tanks in a recirculating system. After the feeding trial, six fish per tank were netted randomly and placed into 12‰ saline water to test their response to salinity stress. The results indicated that the feed conversion rate was enhanced by dietary supplementation with 5′-IMP. The appetite, plasma neuropeptide Y level and feeding rate of the P3 group were lower than those in the control treatment group. Dietary supplementation with 5′-IMP improved the osmoregulatory adaptation of gibel carp under acute salinity stress. Six hours after the salinity stress treatment, in the dietary 5′-IMP treatment group, the plasma cortisol and K+ concentrations were lower and the Na+/K+-ATPase activity was greater than that in the control group. Dietary supplementation with 5′-IMP promoted the expression of the glucocorticoid receptors NKA-α1b and NKCC and retarded the expression of Hsp70 in P4-treated gill filaments and kidneys. Dietary supplementation with 5′-IMP resulted in a stable oxidative-stress-resistant phenotype characterized by increased levels of cellular antioxidants, including SOD, catalase, glutathione peroxidase, glutathione reductase and MPO. The above results of the current study demonstrate that supplementation of 5′-IMP can promote feed utilization and have positive influences on the salinity and oxidative stress resistance of gibel carp. [ABSTRACT FROM AUTHOR]

The experiment was carried out to evaluate the effects of double-layer-coated Enterococcus faecium on the growth performance, liver biochemical indices, digestive enzyme activity, intestinal morphometry, immunity gene expression, and microbiota of crucian carps (Carassius auratus gibelio). A total of 320 fish (mean weight 11.0 ± 0.04 g) were randomly distributed into 3 treatment groups of 4 replicates per treatment (20 fish/replicate). Three different experimental diets were designed: dietary C without double-layer-coated E. faecalis, dietary LP supplemented with 1.0 × 107 CFU/g, and dietary HP supplemented with 1.0 × 108 CFU/g double-layer-coated E. faecalis. The fish was fed for 70 days with different diets, followed by a challenge with lipopolysaccharide (LPS). The results showed that the weight gain and specific growth rate increased and the feed conversion rate decreased in the dietary HP (P < 0.05). The dietary LP had higher lipase and protease activities, and amylase activity increased in the dietary LP and HP after the LPS challenge (P < 0.05). The dietary HP had higher villi height (VH), thicker muscular thickness (MT), and higher VH/MT (VCR) in the intestine (P < 0.05). The intestines were damaged by the LPS challenge; the damage to the dietary HP was alleviated, showing a higher VH, thicker MT, and higher VCR (P < 0.05). The glutathione peroxidase activity of the liver was increased in the dietary HP (P < 0.05). There was no significant difference in liver antioxidant capacity with the LPS challenge among all diets. There was no significant difference in the expression level of the Occludin and Claudin-12 genes among all diets that was up-regulated in dietary HP after LPS challenge (P < 0.05). High-throughput sequencing revealed that the supplementation of double-layer-coated E. faecium increased the species diversity of the intestinal. In conclusion, double-layer-coated E. faecium can improve the absorption of nutrients, enhance immunity, maintain balance in the intestine microbiota, and promote the growth of crucian carp. The supplementation of double-layer-coated E. faecium in the diet can alleviate the intestinal damage caused by LPS challenge.

The experiment was designed to evaluate the effects of different levels of antimicrobial pep‐ tides on the growth, immunity and antioxidant performance of the Juvenile Carassius auratus gibelio.In the experiment, five groups of isonitrogenous and isolipidic diets were designed. A diet without antimicrobial peptides as control group (CK group), and the diets with 50, 75, 100, 125 mg/kg antimicrobial pep‐ tides as experimental diets (D1 group, D2 group, D3 group, D4 group) were fed to Carassius auratus gibelio in the breeding tank [initial average body mass (9.40±0.20) g], three repeats for each group, each group had 25 tail of test fish. After 8 weeks of culture, the fish body composition, growth and digestion performance, immune and antioxidation performance, as well as the serum related indexes were tested. The results showed that: compared with CK group, the growth performance and feed utilization rate of the fish were not influenced by the different levels of the antimicrobial peptides (P>0.05); the muscle crude lipid content the fish were decreased with the increased addition level of the antimicrobial peptides, the crude lipid content of the muscle and liver of D4 group were significantly lower than that of CK group (P<0.05); compared with CK group, the activities of trypsin in the anterior intestine of D2 group increased significantly (P<0.05); the superoxide dismutase activities and total antioxidant capacity of the liver in D2 and D3 groups were significantly increased (P<0.05); the activities of serum lysozyme in D2 and D3 groups increased significantly (P<0.05). The above results indicated that adding Fulitai antibacterial peptide to the diets of Juvenile Carassius auratus gibelio could reduce the muscle lipid content and improve the immune and antioxidant performance of the fish, and the effect would be better when the addition amount of antibacterial peptide were at 75 mg/kg or 100 mg/kg. [ABSTRACT FROM AUTHOR]

An 88-day feeding trial was conducted to evaluate the effects of dietary inosine 5′-monophosphate (5′-IMP) on the growth performance and salinity and oxidative stress resistance in the juvenile gibel carp CAS III (Carassius auratus gibelio; initial body weight: 7.48 g). Four isonitrogenous and isoenergetic diets containing exogenous 5′-IMP were formulated. P1, P2, P3 and P4 were diets containing 5′-IMP at four concentrations (0, 1, 2 and 4 g kg−1). The four diets were randomly allotted to triplicate tanks in a recirculating system. After the feeding trial, six fish per tank were netted randomly and placed into 12‰ saline water to test their response to salinity stress. The results indicated that the feed conversion rate was enhanced by dietary supplementation with 5′-IMP. The appetite, plasma neuropeptide Y level and feeding rate of the P3 group were lower than those in the control treatment group. Dietary supplementation with 5′-IMP improved the osmoregulatory adaptation of gibel carp under acute salinity stress. Six hours after the salinity stress treatment, in the dietary 5′-IMP treatment group, the plasma cortisol and K+ concentrations were lower and the Na+/K+-ATPase activity was greater than that in the control group. Dietary supplementation with 5′-IMP promoted the expression of the glucocorticoid receptors NKA-α1b and NKCC and retarded the expression of Hsp70 in P4-treated gill filaments and kidneys. Dietary supplementation with 5′-IMP resulted in a stable oxidative-stress-resistant phenotype characterized by increased levels of cellular antioxidants, including SOD, catalase, glutathione peroxidase, glutathione reductase and MPO. The above results of the current study demonstrate that supplementation of 5′-IMP can promote feed utilization and have positive influences on the salinity and oxidative stress resistance of gibel carp.

The experiment was to investigate the effect of adding bile acid to high-lipid diet on growth performance, muscle nutrition and fatty acid composition of gibel carp. A total of 450 healthy and initial body weight (32.37±0.13) g juvenile fish were randomly divided into five groups, with three replicates in each group and 30 fish in each replicate. Five kinds of iso-nitrogen and iso-lipid feed were prepared by adding 0 (BA0), 200 (BA200), 400 (BA400), 600 (BA600) and 800 mg/kg (BA800) bile acids to basic feed containing 12% soybean oil, respectively. The experiment lasted for 8 w. The results showed that compared with BA0, FBW of BA400 and BA600 gibel carp was significantly increased (P<0.05), WGR of BA600 was significantly increased (P<0.05), VSI was significantly decreased (P<0.05). The FCR of gibel carp in BA200, BA400 and BA600 was significantly decreased (P<0.05). HSI of all experimental groups was significantly decreased (P<0.05). CF of BA800 was significantly increased (P<0.05). Compared with BA0, muscle crude fat content of experimental groups was significantly decreased (P<0.05), and MUFA content was significantly increased (P<0.05). The crude protein content of gibel carp in BA400 and BA600 were significantly increased (P<0.05). The crude ash content of gibel carp in BA600 and BA800 were significantly decreased (P<0.05). The study indicates that adding 400~600 mg/kg bile acid to high-lipid diet can promote growth of gibel carp, increase the utilization rate of feed, promote fat digestion, absorption and decomposition for energy supply, improve muscle fatty acid composition. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Hydrobiology is the property of Editorial Department of Journal of Hydrobiology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The experiment was to investigate the effect of nutrient peptide on growth performance, serum biochemistry and antioxidant properties of Carassius auratus gibelio. Carassius auratus gibelio with an average body weight of 50 g/tail were randomly divided into two groups, Carassius auratus gibelio in control group were fed with basal diet, Carassius auratus gibelio in experimental group were fed with basal diet supplemented with 2.0% nutrient small peptide, with a feeding volume of 400 Carassius auratus gibelio/667 m2. The pond area of the experimental group and control group was 52 360 and 51 362 m2, respectively. The experiment lasted for 128 d. The results showed that the body weight and body length of Carassius auratus gibelio in experimental group were extremely higher than those of control group (P<0.01). serum total protein and albumin content was extremely higher than that of control group (P<0.01), and glucose content was extremely lower than that of control group (P<0.01), serum superoxide dismutase activity, total antioxidant capacity and malondialdehyde content were higher than that of control group. The experiment indicates that adding 2% nutritional peptide to diet can improve growth performance and health level of Carassius auratus gibelio. [ABSTRACT FROM AUTHOR]

Aflatoxin contamination of food and water is a serious problem worldwide. This study investigated the defensive ability of gibel carp exposed to aflatoxin B1 (AFB1) by challenging it with cyprinid herpesvirus 2 (CyHV-2) infection. The data showed that AFB1 exposure significantly increased the mortality of CyHV-2-infected gibel carp, and enhanced the viral load in the fish liver, kidney, and spleen. The oxidative-antioxidant balance suggested that AFB1 induced severe oxidative stress, including increased reactive oxygen species (ROS) and malondialdehyde (MDA) levels in the AFB1 exposed group, and the reduced activity of superoxide dismutase (SOD), glutathione-S-transferase (GST) and catalase (CAT) in the AFB1 exposed group. Meanwhile, the related expression of nuclear factor erythroid 2-related factor 2 (Nrf2), interferon regulatory factor 3 (IRF3) and the type 1 interferon (IFN1) were noticeably down-regulated, but caspase-1 was up-regulated, after exposure to AFB1, demonstrating that fish are unable to avoid the virus infection. It should be noted that the intestinal microbiota diversity and richness were lower in the AFB1 exposed group, and the composition of intestinal microbiota was affected by AFB1, resulting in the higher abundance of bacteria (such as Aeromonas and Bacteroides) and the lower abundance of potentially beneficial bacteria (such as Cetobacterium and Clostridium) in the AFB1 exposed group. This research provides insight into the possibility that AFB1 may increase the susceptibility of C. gibelio to CyHV-2 infection, and thus amplify the viral outbreak to endanger ecological safety in aquatic environment. [ABSTRACT FROM AUTHOR]

In the high-density pond aquaculture of gibel carp (Carassius auratus gibelio) in China, copper sulfate (CuSO 4) and trichlorfon (Tri) are commonly used, either in combination or alternately, to prevent and control various diseases and harmful algae. Despite their widespread use, there is a lack of studies on the toxic effects of CuSO 4 and Tri on gibel carp, particularly regarding their combined application. This study assessed the effects of exposure to CuSO 4 (0.5 mg/L) and Tri (0.5 mg/L), both individually and in combination, on gibel carp over 21 days. Histopathological assessments revealed significant structural damage to the liver and intestines in gibel carp exposed to either CuSO 4 or Tri alone, with co-exposure notably intensifying these effects. Analysis of antioxidant enzyme activities revealed a substantial reduction in the liver and intestines, concurrent with a significant rise in the oxidative stress marker malondialdehyde in both single and combined exposure groups. Moreover, quantitative PCR analyses indicated a downregulation of immune-related genes post-exposure, with the combined treatment causing more severe suppression. This suppressed immune response correlated with a reduced ability to resist infection by the pathogenic bacterium Aeromonas hydrophila , particularly in the combined exposure group. This indicates that long-term exposure to CuSO 4 and Tri, particularly in combination, induces significant oxidative stress damage in the liver and intestinal tissues, suppresses immune function, and reduces disease resistance. Additionally, 16S rRNA sequencing of the intestinal microbiota revealed that CuSO 4 and Tri exposure altered the diversity and composition of intestinal microbial communities, potentially bringing both benefits and drawbacks. These findings underscore the need for careful management of CuSO 4 and Tri in aquaculture to mitigate their adverse impacts, especially when used in combination for an extended period. • CuSO 4 and trichlorfon caused significant liver and intestine damage. • CuSO 4 and trichlorfon exposure, individually or combined, induces oxidative stress. • Immune-related gene expressions were inhibited after exposure to CuSO 4 and trichlorfon. • Combined CuSO 4 and trichlorfon exposure increased mortality rates post A. veronii infection. • CuSO 4 and trichlorfon significantly reduced intestinal microbial diversity and richness. [ABSTRACT FROM AUTHOR]

Malathion is an organophosphorous insecticide, used in agriculture and a possible source of environmental poisoning. During malathion metabolization, mitochondria generates reactive oxygen species, responsible for significant structural changes. In this study, gills and kidney histological changes in Carassius auratus gibelio exposed to 0.05 mg/l malathion were investigated. In kidney, the effects were dramatic. The 24 -72 hours exposure to malathion induced cytoplasm vacuolization and changes in cell and nuclear volumes. In addition, necrotic renal tubules appeared, nuclear malformations of epithelial cells, anisokary, nuclei pycnosis and nuclei hypertrophy, were noticed. Epithelial ruptures, secondary lamellae fusion and hyperplasia of branchial epithelium, vascular congestion were the main changes noticed soon after pollutant exposure. We suggest that structural changes in gill and kidney could be used as good response to aquatic pollution with organophosphorous insecticides.

To investigate the physiological features of the melanocortin-4 receptor (MC4R) gene, which was demonstrated to be strictly related to food regulation in vertebrates, the coding DNA sequence (CDS) of MC4R in gibel carp (Carassius auratus gibelio) was cloned and characterized (designated as CgMC4R). In this study, the CDS of the CgMC4R gene was 981 bp long that predicted to encode a protein of 327 putative amino acids with seven potential hydrophobic transmembrane domains (TMD1-TMD7). Bioinformatic analysis revealed that CgMC4R shared 99% identity with that in goldfish and exhibited high similarity with that in Cyprinidae species. In addition, CgMC4R was predominantly expressed in the hypothalamus. Furthermore, hypothalamic CgMC4R mRNA expression exhibited altered responses under fed/fasting conditions. In the postprandial experiment, the expression of CgMC4R in the unfed group was upregulated at 1 and 3 h postfeeding compared to that in the fed fish, respectively. During long-term fasting, CgMC4R mRNA transcript levels dramatically increased within 1, 3, 5, and 7 days of fasting. After refeeding, the CgMC4R gene presented a marked decrease in expression after refeeding at 9 days and finally returned to the level in control group. Taken together, these results indicated that the MC4R gene plays a significant role in the feed intake of gibel carp and provides basic evidence to explore the appetite-related roles of MC4R in gibel carp. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of poly-γ-glutamic acid (γ-PGA) diets on the growth, antioxidant capacity, and nutrient absorption of gibel carp. Six groups (Control, PGA-25, PGA-50, PGA-100, PGA-200 and PGA −400) were supplemented with different γ-PGA addition (0, 25, 50, 100, 200, 400 mg/kg), respectively, and were fed for 8 weeks. The results showed that the final weight (FW), weight gain (WG) were quadratically and cubically increased (P 0.05), whereas the crude fat was cubically affected by graded dietary γ-PGA levels (P = 0.049). The serum albumin (ALB) content was cubically increased, whereas the aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities, triglyceride (TG) and total cholesterol (TC) were decreased with increasing dietary γ-PGA levels. The alkaline phosphatase (ALP) activity, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C), however, were not affected by the γ-PGA trail. Digestive enzymes, including amylase, lipase and trypsin in the intestine and liver, were all quadratically or cubically increased with increasing dietary γ-PGA levels (P

Poly‐β‐hydroxybutyrate (PHB) can promote growth and enhance immunity of aquatic animals such as gibel carp, Carassius auratus gibelio. However, the optimal dietary supplementation level and feeding duration for gibel carp are still unclear. In this study, effects of various PHB supplementation levels on gibel carp growth performance, digestive enzyme activities, immune function, disease resistance, and intestinal mucosal barrier were evaluated. Six experimental diets differing in PHB levels were formulated, that is, 0% (P0 as control), 0.5% (P0.5), 1% (P1), 2% (P2), 4% (P4), and 8% (P8). Results indicated that PHB promoted fish growth performance significantly (p < 0.05). Compared to control group P0, the intestinal lipase, protease, and amylase activities in group P4 were significantly increased after 30 days (p < 0.05). Meanwhile, dietary PHB supplementation at 4% level for 30 days and 0.5% for 60 days upregulated the mRNA expression of immune‐related genes, including IL‐11, ITLN, MPO, KRT‐8, DUSP‐1, and PNP‐5α (p < 0.01). Furthermore, PHB at 4% for 30 days showed positive effects on disease resistance against both viral and bacterial infections and exerted beneficial effects on maintaining epithelial mucosal barrier integrity. In conclusion, 4% PHB supplementation for 30 days or 0.5% for 60 days was recommended for gibel carp culture. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Dalian Ocean University is the property of Journal of Dalian Ocean University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Paeonol, a naturally occurring polyphenol isolated from medical plant, has been known to exhibit anti-oxidative and anti-inflammatory effects. In order to evaluate the effect of paeonol on Carassius auratus gibelio infected by pathogenic bacteria Aeromonas hydriphila. 750 fish were randomly divided into 5 groups, which separately treated with 0.85% sterile saline (blank), A. hydriphila (negative control), A. hydriphila with paeonol (4 mg/kg, 64 mg/kg), and A. hydriphila with enrofloxacin (12 mg/kg, positive control). Fish were anaesthetized with MS-222 (100 mg/L), and samples were collected at 6 and 72 h after A. hydriphila challenge. The results showed that compared with the negative group, the survival in paeonol groups marked increased by 14.75% and 18.94%. The plasma immunoglobulin M (IgM) was notably increased, and low density lipoprotein (LDL) was significantly decreased in paeonol groups at 6 h (P < 0.05). The antioxidative enzymes catalase (CAT), total antioxidant capacity (T-AOC) and glutathione peroxidase (GSH-Px) were significantly increased in paeonol groups at 6 h, while malondialdehyde (MDA) and myeloperoxidase (MPO) contents were lower (P < 0.05). The inflammatory related genes MyD88 and TLR-5 were significantly downregulated, and the TLR-3 was significantly increased in paeonol groups at 72 h (P < 0.05). In addition, histopathological analyses showed that the lesion in liver, spleen and caudal kidney were considerably attenuated in paeonol groups. In conclusion, paeonol could increase the survival rate, mitigate oxidative damage, inflammation, tissue lesions, and improve the immunity of gibel carp challenged with A. hydrophila. [Display omitted] • Paeonol enhanced antioxidant and anti-inflammatory ability challenged with A. hydrophila. • Paeonol attenuated liver, spleen and caudal kidney lesions challenged with A. hydrophila. • Paeonol increased the survival of Carassius auratus gibelio challenged with A. hydrophila. [ABSTRACT FROM AUTHOR]

The experiment was to explore the effect of different fat sources in diet on growth of Ctenopharyngodon idella, Mylopharyngodon piceus and Carassius auratus gibelio, as well as conventional muscle nutrients and fatty acid composition. A total of 240 fish with an initial body weight of (34.8±0.4) g Ctenopharyngodon idella, (35.0±0.4) g Mylopharyngodon piceus, (26.3±0.1) g Carassius auratus gibelio were randomly divided into four groups with three replicates in each group and 60 fish in each replicate (three species mixed culture, 20 fish per species). The basic diet (BD group) without oil and fat was used as control group, and 6% soybean oil (SO group), fish oil (FO group) and lard (LO group) were added to basic diet as test groups. The experiment lasted for 8 w. The results showed that the average survival rate of the three species of fish in each group was significantly higher than that in BD group (P<0.05), and the survival rate of Mylopharyngodon piceus in test group was significantly higher than that in BD group (P<0.05). The total final weight and average weight gain of the three fish in each group were significantly higher than that in BD group (P<0.05). The feed coefficient of each group was significantly lower than that in BD group (P<0.05). The visceral body ratio and liver body ratio of Ctenopharyngodon idella in FO group were significantly higher than those in BD group (P<0.05), and the visceral body ratio and liver body ratio of Mylopharyngodon piceus in LO group were significantly higher than those in BD group (P<0.05). The visceral body ratio of Carassius auratus gibelio in BD group was significantly lower than that in other groups (P<0.05), and the liver to body ratio of Carassius auratus gibelio in FO group was significantly lower than that in other groups (P<0.05). The crude protein content of Ctenopharyngodon idella in FO group was significantly higher than that in BD group and SO group (P<0.05), and the crude protein content of Mylopharyngodon piceus in SO group was significantly lower than that in other groups (P<0.05). The crude fat content of Ctenopharyngodon idella in LO group was significantly higher than that in other groups (P<0.05), and the crude fat content of Mylopharyngodon piceus in SO group was significantly higher than that in other groups (P<0.05). The content of C16:0 was the highest in the three fish muscle fatty acids, followed by C18:1n-9, C18:0 and C18:2n-6. The content of C18: 2n-6, C18:3n-3 in SO group were significantly higher than other groups (P<0.05). The content of C20: 5n-3, C22:6n-3 in FO group were significantly higher than other groups (P<0.05). The content of C16:0, C18:1n-9 in LO group were significantly higher than those in other groups (P<0.05). The study indicates that adding fish oil to Ctenopharyngodon idella bait has a good growth-promoting effect, but adding 6% soybean oil and lard has no obvious growth-promoting effect, which indicates that Ctenopharyngodon idella has lower requirements for feed fat level. Adding 6% soybean oil, fish oil and lard to Mylopharyngodon piceus bait has better growth-promoting effect. Adding 6% fish oil and lard to Carassius auratus gibelio has better growth-promoting effect, but soybean oil has poor effect. [ABSTRACT FROM AUTHOR]

Aflatoxin contamination of food and water is a serious problem worldwide. This study investigated the defensive ability of gibel carp exposed to aflatoxin B1 (AFB1) by challenging it with cyprinid herpesvirus 2 (CyHV-2) infection. The data showed that AFB1 exposure significantly increased the mortality of CyHV-2-infected gibel carp, and enhanced the viral load in the fish liver, kidney, and spleen. The oxidative-antioxidant balance suggested that AFB1 induced severe oxidative stress, including increased reactive oxygen species (ROS) and malondialdehyde (MDA) levels in the AFB1 exposed group, and the reduced activity of superoxide dismutase (SOD), glutathione-S-transferase (GST) and catalase (CAT) in the AFB1 exposed group. Meanwhile, the related expression of nuclear factor erythroid 2-related factor 2 (Nrf2), interferon regulatory factor 3 (IRF3) and the type 1 interferon (IFN1) were noticeably down-regulated, but caspase-1 was up-regulated, after exposure to AFB1, demonstrating that fish are unable to avoid the virus infection. It should be noted that the intestinal microbiota diversity and richness were lower in the AFB1 exposed group, and the composition of intestinal microbiota was affected by AFB1, resulting in the higher abundance of bacteria (such as Aeromonas and Bacteroides) and the lower abundance of potentially beneficial bacteria (such as Cetobacterium and Clostridium) in the AFB1 exposed group. This research provides insight into the possibility that AFB1 may increase the susceptibility of C. gibelio to CyHV-2 infection, and thus amplify the viral outbreak to endanger ecological safety in aquatic environment.

• GA3 induced erythrocyte nucleus changes in gibel carp. • GA3 induced liver dysfunction and oxidative stress in gibel carp. • GA3 caused ER stress and apoptosis in the lives of gibel carp. Gibberellic acid (GA3), one of the most plant growth stimulator, is widely applied in agricultural regions and in beer industry. However, GA3 residue remained in soil and water can cause toxicity to all organisms. In this study, we investigated the mechanisms of GA3-induced hepatic injury in gibel carp (Carassius auratus gibelio). We found that GA3 exposure caused oxidative stress, endoplasmic reticulum stress (ERS), and apoptosis. The gibel carp exposed to GA3 exhibited significant alteration in erythrocyte nuclei. GA3 induced liver damage, as indicated by increasing the aminopherase activities. GA3 led to oxidative stress by increasing malondialdehyde content and decreasing the activities of CAT and GPx. GA3 stimulated ERS and increased the expression of grp78, perk, eif2s1α, chop, atf4, ire1α, xbp1, and atf6. Additionally, GA3 down-regulated the level of anti-apoptotic gene Bcl-2 and up-regulated the levels of pro-apoptotic genes bax and caspase-3. Overall results demonstrated that GA3 caused hepatic injury in gibel carp by increasing oxidative stress, ERS, and apoptosis. [ABSTRACT FROM AUTHOR]

There are indications that the intestinal microbiota, bile acids, lipid metabolism, and host genotype may all be interconnected, but their interrelationships are still only partially understood. In the present study, we designed three feeding trials and used gibel carp (Carassius auratus gibelio) as a model to investigate the interactions among all of the above parameters. In trial 1, we used wild-type (WT) and heterozygous pik3r1 -deficient (P85+/−) fish (each n = 15) and found that the composition and structure of gut microbiota significantly differed between the two groups. The WT group exhibited a lower intestinal content of bile acids and increased physiological and histological parameters associated with obesity. Citrobacter freundii was significantly correlated with bile acid content. In trial 2, we supplemented two different levels of C. freundii GC01 strain to the WT fish diet: 106 (C6) and 109 (C9) cfu/kg (all n = 24). Experimental groups had lower obesity indices, but higher growth parameters, and bile acid content. As cholic acid was the most abundant bile acid in the gut of gibel carp, in trial 3 we supplemented it to the fish feed: the experimental group had lower obesity indices. In summary, the P85+/− genotype restructured intestinal microbiota and increased the abundance of C. freundii. This triggered a metabolic cascade: gut microbiota modulation affected the bile acid content, which then affected the lipid metabolism, and thereby obesity indices in fish. The intriguing observation that Citrobacter freundii GC01 appears to improve feed utilization in gibel carp, while simultaneously reducing lipid accumulation, deserves further studies aimed at potential application in aquaculture. [Display omitted] • Our experiment has demonstrated that the host's genotype restructures the gut microbiome and regulates fat metabolism in fish. • We find a metabolic cascade: gut microbiota modulation affected bile acid content – which affected lipid metabolism in fish. • Our results indicate that certain bacterial strain may improve feed utilization and growth parameters, while reducing obesity [ABSTRACT FROM AUTHOR]

Paeonol (2′-hydroxy-4′-methoxyacetophenone) is a phenol that exhibits antioxidant and anti-inflammatory capabilities. In this study, the underlying mechanism of paeonol against LPS-induced oxidative stress and inflammatory responses in gibel carp was investigated. Three hundred healthy gibel carp were divided into five groups (n = 9), intraperitoneally injected with LPS and thereafter treated with paeonol (16 mg/kg and 64 mg/kg). Fish were anesthetized with MS-222 (100 mg/L), and samples were collected at 72 h to investigate plasma biochemical indexes, liver histopathology, antioxidant enzymatic activity, and TLR receptor-related gene expression. Fish injected with LPS (20 mg/kg) exhibited significantly increased plasma aminotransferase (ALT), aminotransferase (AST), lactate dehydrogenase (LDH), glucose (GLU), diamine oxidase (DAO), and alkaline phosphatase (ALP) levels (P < 0.05). In addition, LPS challenge significantly enhanced myeloperoxidase (MPO) and malondialdehyde (MDA) contents, whereas those of catalase (CAT) and glutathione peroxidase (GSH-Px) decreased (P < 0.05). However, treatment with paeonol attenuated these LPS-induced changes (P < 0.05). The mRNA expression of TLR4, TIRAP, MyD88, TRAF6, NF-κB, TNF-α, IL-1β, and IL-8, which were activated by LPS challenge (P < 0.05), were downregulated by paeonol. Additionally, histopathological examination demonstrated that paeonol alleviates LPS-induced hepatic tissue lesions in fish. Taken together, the results suggest that paeonol mitigates LPS-induced liver oxidative stress and inflammation in gibel carp. [Display omitted] • Paeonol alleviates the hepatic tissue lesions of gibel carp challenged with LPS. • Paeonol mitigates LPS-induced oxidative stress and inflammatory response in gibel carp. • The anti-inflammatory effect of paeonol in gibel carp is associated with the inhibition of TLR4/NF-κB signaling pathway. [ABSTRACT FROM AUTHOR]

A 10-week feeding trial was conducted to investigate the effects of individual and combined inclusion of phytase and protease on the growth performance, digestive ability, immune response and muscle amino acid profile of gibel carp (Carassius auratus gibelio) fed low phosphorus (LP) and/or low fish meal (LFM) diets. Seven experimental diets were designed: 1) Normal diet [PC, 15 g/kg Ca(H 2 PO 4) 2 and 80 g/kg fish meal], 2) Low P diet [10 g/kg Ca(H 2 PO 4) 2 and 80 g/kg fish meal], 3) LP + 0.4 g/kg phytase diet (LP + Ph), 4) Low fish meal diet [LFM, 15 g/kg Ca(H 2 PO 4) 2 and 50 g/kg fish meal], 5) LFM + 0.5 g/kg protease diet (LFM + Pr), 6) Low P and Low fish meal diet [LP-LFM, 10 g/kg Ca(H 2 PO 4) 2 and 50 g/kg fish meal] and 7) LP-LFM + 0.4 g/kg phytase +0.5 g/kg protease diet (LP-LFM + Ph + Pr). The results showed that the growth performance, whole body composition, nutrient digestibility, immunological indices, and muscle amino acid contents of gibel carp fed the LP, LFM and LP-LFM diets were dramatically lower than those of carp fed the normal diet (P <0.05). However, compared the LP-LFM, LFM and LP groups, dietary addition of phytase + protease, protease and phytase, respectively, (1) improved the special growth rate (SGR), weight gain rate (WGR), ADC of dry matter, crude protein and P; (2) upregulated the activities of lipase, trypsin, amylase and chymotrypsin in the liver and intestine; (3) increased liver lysozyme (LZM), superoxide dismutase (SOD), glutathione peroxidase (GPx) and total antioxidant capacity (T-AOC) levels, intestinal secreted immunoglobulin A (sIgA), complement 4 (C4) and C3 levels; (4) increased the contents of amino acids, for example, valine, leucine and methionine, in the muscle. Moreover, when both phytase and protease were added simultaneously, they had a better promoting effect than when individual added. It can be concluded that a reduction of dietary P and fish meal for gibel carp has side effects on growth performance, while phytase and protease could mitigate these effects by improving the digestive ability and immune response of gibel carp. • Supplementation of phytase, protease and their combination improved the growth performance of gibel carp. • Supplementation of phytase, protease and their combination improved digestive, immunity and flesh quality of gibel carp. • When both phytase and protease were added simultaneously, they had a better promoting effect than when individual added. [ABSTRACT FROM AUTHOR]

• Monoclonal antibodies against ORF66, the main encoding protein of CyHV-2, were successfully prepared. • The anti-CyHV-2 ORF66 monoclonal antibodies can specifically recognize the CyHV-2 ORF66 recombinant protein. • The anti-CyHV-2 ORF66 monoclonal antibodies can specifically recognize the ORF66 nucleocapsid protein in the virus. • The anti-CyHV-2 ORF66 MAb-2F11 can be used as a detection tool to detect virus particles in gibel carp tissues and cells. Cyprinid herpesvirus 2(CyHV-2)is the main pathogen causing haematopoietic necrosis disease of goldfish (Carassius auratus auratus) and gibel carp (Carassius auratus gibelio), which has caused huge economic losses to aquaculture industry of goldfish and gibel carp around the world. Currently, various detection methods based on nucleic acids have been established for the detection of CyHV-2. However, there is still a lack of rapid and effective immunological detection technology. In this study, anti-CyHV-2 ORF66 monoclonal antibodies (MAbs) were prepared to use the recombinant ORF66 protein as the antigen. Firstly, the open reading frame of CyHV-2 ORF66 was cloned into the pET-28a vector and expressed in Escherichia coli. Three MAbs (2F11, 2G8, and 3D6) against recombinant ORF66 protein were developed by immunization of Balb/C mice. Among them, MAb-2F11 belonged to the IgG2b isotype, 2G8 and 3D6 belonged to the IgG1 isotype. Western blotting analysis was performed to assess the ability of the MAbs to bind to the ORF66 recombinant protein and CyHV-2 nucleocapsid protein ORF66. In addition, the MAb-2F11 was used to detect the virus particles that infected in cell line and tissues of gibel carp virus infection by immunological methods. These results indicated that the anti-CyHV-2 ORF66 MAb-2F11 prepared in this study could not only detect the presence of the virus but also provide a research tool for further studying the role of ORF66 in the process of CyHV-2 infection. [ABSTRACT FROM AUTHOR]