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Simple Summary: Aeromonas hydrophila and Aeromonas veronii are common pathogenic bacteria in grass carp aquaculture. Through comprehensive histopathological analysis and molecular characterization, we found that both pathogens caused severe cellular necrosis, cytoplasmic vacuolization, and hemorrhage in the liver of grass carp, similar to the manifestations of infection in other aquatic animals. The grass carp showed complex regulation of immune and metabolic responses during infection, especially activation of Toll-like receptors and TNF signaling pathways. Our findings provide new insights into host–pathogen interactions during Aeromonas co-infection in grass carp and provide a scientific basis for the development of prevention and control strategies. The grass carp (Ctenopharyngodon idella) is highly susceptible to infections caused by Aeromonas species, particularly A. hydrophila and A. veronii. However, the immunological mechanisms underlying co-infection by these pathogens remain largely uncharted. This study investigated the pathogenesis and host immune response in grass carp following concurrent infection with A. hydrophila and A. veronii. Mortality was observed as early as 24 h post-infection, with cumulative mortality reaching 68%. Quantitative analysis demonstrated significantly elevated bacterial loads in hepatic tissue at 3 days post-infection (dpi). Histopathological evaluation revealed severe hepatic lesions characterized by cellular necrosis, cytoplasmic vacuolization, and hemorrhagic manifestations. Comparative transcriptomic analysis of hepatic tissues between co-infected and control specimens identified 868 and 411 differentially expressed genes (DEGs) at 1 and 5 dpi, respectively. Gene ontology and KEGG pathway analyses revealed significant enrichment of immune-related genes primarily associated with Toll-like receptor signaling and TNF signaling cascades. Notably, metabolic pathways showed substantial suppression while immune responses were significantly activated after infected. These findings provide novel insights into the host–pathogen interactions during Aeromonas co-infection in grass carp, which may facilitate the development of effective prevention and control strategies. [ABSTRACT FROM AUTHOR]

The current study was conducted to assess the impact of market available probiotic containing Lactobacillus rhamnosus GG bacteria on the growth performance and morphometric characters of grass carp for 60 days. A total of 120 fish fingerlings of mean weight 2.95±0.27g were randomly distributed into four experimental groups having three replicates (n=10/aquarium) and fed with four experimental diets i.e., D1 (commercial fish feed without probiotics as control), D2, D3 and D4 (commercial fish feed with addition of 2g, 4g and 6g Lactobacillus rhamnosus GG/kg respectively) @ 5% of their body weight. Growth performance was determined in terms of final body weight (FBW), weight gain (WG), percent weight gain (%WG), average daily weight gain (AWG), specific growth rate (SGR), feed conversion ratio (FCR) and survival rate (SR) of fingerlings. Morphometric traits were measured including total length (TL), standard length (SL), fork length (FL), head length (HL), eye diameter (ED), dorsal fin length (DFL), pectoral fin length (PFL), pelvic fin length (PvFL), anal fin length (AFL) and caudal fin length (CFL). The highest FBW (14.20±0.08g), WG (11.25±0.08g), AWG (0.18±0.00g), SGR (2.61±0.05% day-1), %WG (381.340±14.40g), and SR (100%) and lowest FCR (1.94±0.00) were recorded in D4 (P< 0.05) followed by D3, D2 and D1. Fish fed with probiotics showed improved (P<0.05) morphometric traits and highest TL(15.19±0.29cm), SL(13.17±0.40cm), FL(14.04±0.28cm), HL(1.76±0.04cm), ED(0.62±0.04cm), DFL(1.82±0.04cm), PFL(1.43±0.04cm), PvFL(1.36±0.05cm), AFL(1.41±0.09cm) and CFL(1.82±0.04cm) was observed in D4. The result of this study demonstrated the importance of commercial probiotic as feed additives containing L. rhamnosus GG to improve the growth, survival rate and morphometric parameters of grass carp. [ABSTRACT FROM AUTHOR]

Grass carp belongs to Cypriniformes, Cyprinidae, and Cyprinus family, and is typically referred to as the four famous domestic fishes, black carp, silver carp, and bighead carp, respectively. The annual production of Chinese grass carp is consistently among the highest, with an output of 5.905 million tons in 2022, accounting for 24.3% of total of freshwater fish production. Reproduction is the core process of fish reproduction. Normal gonad development is a prerequisite for fish reproduction. At present, there are few reports on the sex differentiation of Chinese grass carp. Studying the differentiation and development of grass carp gonads can provide a typical model for gonadal development of cyprinid fish. In contrast, the start and completion time of gonadal differentiation are one of the key factors inducing sex reversal in fish using hormones. Research on gonadal differentiation and development in grass carp can also lay the foundation for the establishment of a unisexual population of grass carp.Sex-related genes play important roles in biological processes such as sex determination, gonadal differentiation, and reproduction and development in fish. In most differentiated teleost fish, genes such as dmrt1, sox9, foxl2, amh, and cyp19a1a, are considered the key genes involved in sex regulation. cyp19a1a plays a key role in the gonadal differentiation and ovarian development of teleost fish by aromatizing androgens into estrogen via aromatase activity. This gene is specifically expressed in the gonads and is used served as a characteristic gene for sex differentiation towards females. Anti-Müllerian hormone (amh) regulates the structure of reproductive organs and the differentiation and development of reproductive cells. In fish such as carp, rainbow trout, and grass carp, the expression level of the amh gene in the testes is significantly higher than that in the ovaries, and is often used as a characteristic gene for male differentiation.To explore the sex differentiation and developmental patterns of grass carp gonads, this study analyzed the tissue structure and expression differences of sex characteristic genes cyp19a1a and amh in the gonads of grass carp at 1, 2, 3, 4, 5, 6, 12, 24, 36, and 48 months of age using tissue sectioning technology and real-time fluorescence quantification technology. The results of tissue sectioning showed that grass carp exhibited reproductive ridges at 1-month-old. At 2 months of age, primitive germ cells were first observed in the reproductive crest, marking the formation of their primitive gonads. At 3-month- old, ovarian cavities and lobules were observed in the gonads of female grass carp. At 4-month-old, oogonia was observed, indicating anatomical differentiation at 3-month-old and cytological differentiation at 4-month-old. At the age of 4 and 5 months, ductus deferens and spermatogonia were respectively observed in male grass carp gonads, indicating anatomical differentiation at 4 months and cytological differentiation at 5 months. The ovaries of 24, 36, and 48-month-old grass carp were in the first, second, third, and fourth stages of development, respectively, while the testes were in the second, second, third, and fourth stages of development, respectively. At 48 months of age, the gonads of grass carp have matured. The fluorescence quantitative results showed that the expression level of the female characteristic gene cyp19a1a in the ovary showed an overall trend of first increasing, then decreasing, and then increasing again. The expression level of this gene was significantly upregulated at 2 months of age (P < 0.05), and reached its peak at 3, 6, and 48 months of age. During these three periods, anatomical changes were observed in the female gonads in the tissue sections, with a large proliferation of oocytes and the gonads tending to mature. The expression level of the male characteristic gene amh in the testes showed an overall trend of first increasing and then decreasing. At 2 months of age, the expression level of this gene was significantly upregulated (P < 0.05). At 5 months of age, it reached the peak when there were a large proliferation of spermatogonia in the gonads, and then remained low expression until gonadal maturity.In summary, this study confirmed that the initiation time of grass carp gonadal development is approximately 2 months old, and the differentiation time of male and female gonads is approximately 3 and 4 months old, respectively. By the age of 6 months, both male and female grass carp gonads completely differentiated. These results not only enrich the reproductive physiology data of grass carp but also provide a reference basis for the study of hormone-induced sex reversal technology in grass carp.

The biofloc technology (BFT) offers benefits in improving feed utilization and reducing the feed conversion ratio compared to the recirculating aquaculture system (RAS). In this study, high-throughput 16S rRNA gene sequencing was employed to investigate and compare the bacterial communities in these aquaculture systems and the gut microbiota of grass carp reared in them. We observed a significant distinction between the microbial communities of the aquaculture systems and the intestinal microbiota of grass carp. The genera cetobacterium and bacillus were more abundant in the BFT system, accounting for only 0.05% and 0.25% in the RAS. Our study also demonstrated that BFT could influence the intestinal microorganisms of grass carp (Ctenopharyngodon Idella) by reducing the relative abundance of burkholderia-caballeronia-paraburkholderia and increasing that of cetobacterium. Based on bugBase community predictions, the potential pathogenicity in BFT and grass carp intestine was lower than in RAS. Regarding gene expression in the grass carp intestine, immunosuppressive genes showed higher expression, while pro-inflammatory genes exhibited lower expression in grass carp reared in BFT. Furthermore, the final average length and weight of grass carp in the BFT system were significantly higher than those in the RAS. This study provides valuable insights into gut microbiome ecology in relation to two grass carp aquaculture systems, which could be effectively applied in grass carp management to promote health and improve water quality.

Abstract Background Ochratoxin A (OTA) is a toxin widely found in aquafeed ingredients, and hypoxia is a common problem in fish farming. In practice, aquatic animals tend to be more sensitive to hypoxia while feeds are contaminated with OTA, but no studies exist in this area. This research investigated the multiple biotoxicities of OTA and hypoxia combined on the liver of grass carp and explored the mitigating effect of curcumin (CUR). Methods A total of 720 healthy juvenile grass carp (11.06 ± 0.05 g) were selected and assigned randomly to 4 experimental groups: control group (without OTA and CUR), 1.2 mg/kg OTA group, 400 mg/kg CUR group, and 1.2 mg/kg OTA + 400 mg/kg CUR group with three replicates each for 60 d. Subsequently, 32 fish were selected, divided into normoxia (18 fish) and hypoxia (18 fish) groups, and subjected to hypoxia stress for 96 h. Results CUR can attenuate histopathological damage caused by coming to OTA and hypoxia by reducing vacuolation and nuclear excursion. The alleviation of this damage was associated with the attenuation of apoptosis in the mitochondrial pathway by decreasing the expression of the pro-apoptotic proteins Caspase 3, 8, 9, Bax, and Apaf1 while increasing the expression of the anti-apoptotic protein Bcl-2, and attenuation of endoplasmic reticulum stress (ERS) by reducing Grp78 expression and chop levels. This may be attributed to the fact that the addition of CUR increased the levels of catalase (CAT) and glutathione reductase (GSH), increased antioxidant capacity, and ensured the proper functioning of respiratory chain complexes I and II, which in turn reduced the high production of reactive oxygen species (ROS), thus alleviating apoptosis and ERS. Conclusions In conclusion, our data demonstrate the effectiveness of CUR in attenuating liver injury caused by the combination of OTA and hypoxia. This study confirms the feasibility and efficacy of adding natural products to mitigate toxic damage to aquatic animals.

In order to identify biomarkers of lipid deterioration in grass carp (Ctenopharyngodon idella) muscle during cold storage, the lipid profile change of the grass carp muscle stored at 4 ℃ for different periods (3, 6, and 9 d) was investigated by UPLC-Q Exactive HF-X. Multivariate statistical analysis and one-way ANOVA were used to screen the differential lipids during the cold storage, and then to enrich the metabolic pathways involved in the differential lipids through the KEGG database. The results showed that the pH in grass carp muscle decreased gradually, while the thiobarbituric acid reactive substance, total free fatty acid content, and volatile base total nitrogen increased gradually, reaching 0.82 µg/kg, 168.22 µg/10 g and 23.63 mg/100 g, respectively, on the 9 d of cold storage. A total of 1265 lipid molecules belonging to 5 categories and 35 subclasses were identified in the chilled grass carp muscle. Glycerol phospholipids (GP) and glycerol esters (GL) were the main components of lipids in grass carp muscle. There was no significant difference in lipid profile between grass carp muscle refrigerated for 3~6 days (P>0.05), but there were significant changes in lipid composition when refrigerated for 9 days. Fatty acyl (FA) and sphingolipids (SP) were the major different lipids in the early stage of refrigeration (3~6 days), and GP was the main lipids with significant changes in the late stage of refrigeration (6~9 days). A total of 20 different lipid molecules were screened from multivariate statistical difference analysis, and they were mainly glycerol ester and glycerol phospholipid, among which PE (16:1e/22:6) showed significant differences (P

Grass carp was an important economic fish for freshwater aquaculture. The exploring and utilization of high-quality grass carp germplasm resources were important for ensuring a domestic supply of high-quality aquatic protein. However, natural grass carp populations in China were facing severe threats because of the effects of frequent human activities, water environment damage, overfishing, etc. Against this background, high-quality grass carp germplasm resources were the foundation for the healthy and sustainable development of the grass carp aquaculture industry, so systematic collection, preservation, identification, evaluation, protection, and utilization of them carry great strategic importance. This paper summarizes major research results of grass carp in morphology, cytogenetics, molecular population genetics, etc. It not only introduced genetic improvement techniques such as gynogenesis, hybrid breeding, and polyploid breeding, but also discussed the existing research on the protection measures of grass carp germplasm resources. On this basis, the paper proposed new methods to improve the protection of grass carp germplasm and create improved varieties, which could provide high-quality resources for the sustainable development of the grass carp industry.

There are major gaps in illustrating the risk to freshwater fish that are exposed to environmental microplastics (MPs), even though MPs in freshwater environments has drawn much concern. To explore the potentially negative effects of microplastics on freshwater fish, grass carp (averaging 9.215 ± 0.035g) were exposed to microplastics (32–40 μm in diameter) at two environmental concentrations (100 and 1000 μg/L) for 21 days, and evaluated for physio-biochemical performance, gut microbiome, and metabolome responses. After exposure, microplastics were detected in the intestine and within basal nuclei and goblet cells hyperplasia. Antioxidant enzyme activities (superoxide dismutase and catalase) also significantly decreased within the intestines (P

Olfaction, the sense of smell, is crucial for animal survival, especially in localizing prey or food. However, little is known about the fish behavioral responses to specific food odors and which olfactory receptor might be activated by the food odors. Here, we examined the evolutionary relationships and classified the subfamilies of olfactory receptors (ORs), and conducted behavioral and gene expression analysis in grass carp (Ctenopharyngodon idellus). We identified 196 intact ORs in the grass carp genome and classified them into 8 subfamilies: β, δ, ε, η, γ, κ, θ, and ζ. 12 representative ORs (4 β, 4 δ, and 4 ε) were highly expressed in the olfactory epithelium (OE) of 24-month-old grass carp. Behavioral exploration found that grass carp showed different behaviors to different food odors at a series of concentrations. Specifically, 0.01 μmol/L amino acid mixtures and 0.005 × Hydrilla verticillata extracts strongly changed the preference index and swimming trajectories in 6-month-old grass carp. In addition, the two food odors stimulation differentially induced ORs expression in three tissues, especially strong in the olfactory bulb and brain. Altogether, our results suggest that olfaction plays an important role in the regulation of fish feeding behavior and provide a basis for further studies on the function and specific recognition of olfactory receptors in fish.

In nature, aflatoxins, especially aflatoxin B1 (AFB1), are the common mycotoxins, which cause serious health problems for humans and animals. This paper aimed to study the effects of AFB1 on flesh flavor and muscle development of grass carp (Ctenopharyngodon idella) and its mechanism. There were 1440 individual fish in total, with 6 treatments and each treatment replicated 3 times. The 6 treatments were fed a control diet with different doses of AFB1 (0.04, 29.48, 58.66, 85.94, 110.43 and 146.92 μg/kg diet) for 60 d. AFB1 increased myofiber diameter, as well as decreased myofiber density of grass carp muscle (P

The pomegranate plant is considered one of the medicinal herbs rich in antioxidants that can be used in aquaculture to support immunity and health. The objective of this investigation was to ascertain the impact of pomegranate peel (Punica granatum) extract (PPE) on growth performance, the intestinal bacteria count, total number of fungi and histological analysis of the grass carp. One hundred five fingerlings (11.04±0.22g) were distributed among 21 aquariums (60-L) in a completely randomized design (triplicated) and fed diets containing 0, 0.5, and 1% PPE for 70 days at a feeding rate of 3% body weight. A spectrophotometry assessment indicated for PPE that the total phenol content was 151.09 and 175.95 GAE/100 g, and flavonoid content was 36.04 and 42.89 RE/100 g, respectively. The results of the present work revealed that growth indicators (final weight, weight gain, specific growth rate (SGR), and feed conversion ratio (FCR)) increased (P<0.05) in the PPE group in comparison to the control group. PPE had an impact on the total count of aerobic bacteria or lactic acid bacteria (LAB), but the experimental treatments dramatically decreased the amount of enteric Gram-negative bacteria (P<0.05). The total fungi count showed a significant increase in all treated fish (P<0.05). Also, histological examination showed improvement and elongation of the villi, as well as an increase in goblet cells for the treatments supplemented with PPE. Therefore, it is recommended to use PPE (0.5%) as a diet additive for grass carp to improve their growth performance and health. [ABSTRACT FROM AUTHOR]

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Background: Ochratoxin A (OTA) is a toxin widely found in aquafeed ingredients, and hypoxia is a common problem in fish farming. In practice, aquatic animals tend to be more sensitive to hypoxia while feeds are contaminated with OTA, but no studies exist in this area. This research investigated the multiple biotoxicities of OTA and hypoxia combined on the liver of grass carp and explored the mitigating effect of curcumin (CUR). Methods: A total of 720 healthy juvenile grass carp (11.06 ± 0.05 g) were selected and assigned randomly to 4 experimental groups: control group (without OTA and CUR), 1.2 mg/kg OTA group, 400 mg/kg CUR group, and 1.2 mg/kg OTA + 400 mg/kg CUR group with three replicates each for 60 d. Subsequently, 32 fish were selected, divided into normoxia (18 fish) and hypoxia (18 fish) groups, and subjected to hypoxia stress for 96 h. Results: CUR can attenuate histopathological damage caused by coming to OTA and hypoxia by reducing vacuolation and nuclear excursion. The alleviation of this damage was associated with the attenuation of apoptosis in the mitochondrial pathway by decreasing the expression of the pro-apoptotic proteins Caspase 3, 8, 9, Bax, and Apaf1 while increasing the expression of the anti-apoptotic protein Bcl-2, and attenuation of endoplasmic reticulum stress (ERS) by reducing Grp78 expression and chop levels. This may be attributed to the fact that the addition of CUR increased the levels of catalase (CAT) and glutathione reductase (GSH), increased antioxidant capacity, and ensured the proper functioning of respiratory chain complexes I and II, which in turn reduced the high production of reactive oxygen species (ROS), thus alleviating apoptosis and ERS. Conclusions: In conclusion, our data demonstrate the effectiveness of CUR in attenuating liver injury caused by the combination of OTA and hypoxia. This study confirms the feasibility and efficacy of adding natural products to mitigate toxic damage to aquatic animals. [ABSTRACT FROM AUTHOR]

The objective of current study was to evaluate the effect of commercially prepared probiotics (PREPRO) containing Lactobacillus rhamnosus GG on body composition of grass carp (fingerlings). Grass carp is a fresh water fish of edible test and having multiple feed sources. The study was aimed to enhance the production and improve the meat quality of a grass carp in controlled environment. A total of 120 grass carp (fingerlings) were selected and stocked in 12 glass aquaria (n=10 fish in each) in a triplicate manner with four different diet groups D1 (control), D2 (2g of L. rhamnosus/kg), D3 (4g of L. rhamnosus/kg), D4 (6g of L. rhamnosus/kg) as feed additive. Statistical analysis was done by using one-way analysis of variance and was applied the Duncan's multiple range test for the identification of significant differences within the treated groups by using statistical package for the social sciences (SPSS) computer software. After the 90 days of experimental trial the results revealed that probiotics treated groups had significantly (P < 0.05) better meat quality as compared to control. The best meat quality was observed in D4 in terms of crude protein, crude fat, ash content and total moisture (45.86±0.44, 33.59±0.28, 8.80±0.34, 63.98±0.01) compared to control and other tasted groups. The L. rhamnosus improves the meat quality of grass carp. [ABSTRACT FROM AUTHOR]

Nutritional value and shelf life of the consolidated burger (grass carp-red meat) during freezing storage at -18 °C was determined in this study. In recent years, with the change in lifestyle and the development of urban life, consuming semi-prepared foods has increased and meat products based on minced meat such as burgers have a major share among these foods in the modern lives. In this study, a combined red meat (beef meat)-grass carp burger with different ratios of 0: 100, 25: 75, and 50:50 was prepared and stored at -18 °C for 4 months. The value of protein, fat, moisture, ash pH, peroxide value, thiobarbituric acid value, volatile nitrogen bases, fatty acid profiles and sensory evaluation were determined on the first day and end of the storage period. Measuring parameters showed the amount of protein, fat, moisture, and ash decreased and the average pH, peroxide, thiobarbituric acid, and volatile basic nitrogen values increased over storage. With increasing the amount of fish meat used in the burger formulation, protein, moisture, ash, and pH values and sensory properties decreased and fat, peroxide, thiobarbituric acid, and volatile nitrogen values increased. The results of this study suggest that consuming Mix50% burger provides some parts of body's needs for unsaturated fatty acids and protein. [ABSTRACT FROM AUTHOR]

This study aimed to explore the effects of different brining times on the sensory, physicochemical properties, and volatile organic compounds (VOCs) of marinated grass carp (MGC). The results showed that different brining time changed the sensory quality, color and texture. The moisture content increased significantly with the extension of brining time, while the salt content, protein content, thiobarbituric acid reactive substances (TBARS), and total volatile basic‑nitrogen (TVB-N) decreased (p

Nucleotides and β-glucan have demonstrated positive effects on the growth and health of aquaculture species. However, little research has been done on the combined effects of using both supplements on the intestinal health and flesh quality of fish. In the present study, we evaluated the impact of nucleotides (0.01 %) or/and β-glucan (0.10 %) on parameters related to intestinal health and flesh quality in grass carp (69.97 ± 0.05 g) over a 60-day feeding period. The results showed that both nucleotides and β-glucan significantly increased catalase activity, enhanced mRNA expression level of zonula occludens-3, downregulated interleukin-1β, interferon, Toll-like receptor-4, and Toll-like receptor-7 expression in the intestine (P < 0.05). Additionally, they also resulted in enhanced springiness and increased percentage of total unsaturated fatty acids, while reducing Myostatin 1 expression and total saturated fatty acids content in the muscle (P < 0.05). This indicates that these supplements have similar effects in promoting oxidation resistance, suppressing inflammation, and improving intestinal barrier integrity and flesh quality in grass carp. Besides, the combination of nucleotides and β-glucan led to a decrease in Firmicutes abundance and an increase in Actinobacteria compared to the control group. We further observed the synergistic effects of nucleotides and β-glucan in decreasing the expression of inflammation related genes (interleukin-1β, interferon, Toll-like receptor-4, and Toll-like receptor-7) and improving parameters associated with intestinal morphology (villus height, villus width and gut wall thickness) and flesh quality (chewiness, springiness, total tasty free amino acids, total saturated fatty acids and total unsaturated fatty acids). Overall, our results suggest that the combined application of nucleotides and β-glucan is more effective in promoting intestinal health and improving flesh quality in grass carp compared to using either supplement alone.

Grass carp, a common aquatic species in China, suffer significant annual losses due to infection by the parasitic ciliate Ichthyophthirius multifiliis (Ich), thus necessitating effective prevention and control measures. In the present study, the Ich β-tubulin gene was cloned and inserted into the eukaryotic expression vector pVAX1 plasmid to construct the Ich β-tubulin DNA vaccine (pVAX1-Bt). After two doses of the pVAX1-Bt vaccine, the relative percentage survival (RPS) reached 70.0 %, whereas the RPS after 2 doses of pVAX1 reached 10.0 %. The β-tubulin antibody, specific antibody IgM, and immune enzymes (MDA, SOD, CAT, ACP, AKP, and cortisol) were tested over13 weeks. The findings revealed a significant enhancement in the vaccinated fish compared to their unvaccinated counterparts, indicating that the vaccine can activate the humoral immune pathway and non-specific immunity in fish, thereby promoting the production of specific antibodies and memory B cells. Collectively, these results indicate that the Ich β-tubulin DNA vaccine has potential in treatment of Ich infection (ichthyophthiriasis).

Yeast culture (YC) has potential effects on improving the health of fish, however, its mechanism of regulating antioxidation and anti-inflammation in hepatocytes remains unclear. In the present study, the oxidative and inflammatory models were constructed in vitro to investigate the effects of yeast culture on the antioxidant and anti-inflammatory capacity in the hepatocytes of grass carp (Ctenopharyngodon idellus). Malondialdehyde (MDA) and lipopolysaccharide (LPS) were used to construct oxidative and inflammatory models, respectively. Then adding 0.025, 0.05, 0.1 and 0.2 g/L YC into the medium of the two models, respectively. The control group was not added MDA, LPS or YC. The results showed that MDA and LPS obviously destroyed the morphology of hepatocytes and significantly decreased the cell viability (P < 0 .05), as well as increased the ROS content in the hepatocytes of grass carp. In addition, compared with the control group, MDA incubation significantly increased the AST and APT activities and the MDA content in cells and significantly decreased the T-SOD, CAT and GPx activities (P < 0 .05). When the YC concentrate was 0.1 and 0.2 g/L in the medium, the morphology and cell viability of hepatocytes were significantly improved compared with these in MDA group (P < 0 .05). Meanwhile, compared with control group, adding 0.1 and 0.2 g/L in the medium could significantly decreased the ROS and MDA content in cell and increased T-SOD, CAT and GPx activities, which may be related to activating nrf2-mediated antioxidant pathway. Compared with LPS group, adding 0.025, 0.05, 0.1 and 0.2 g/L YC into the medium significantly improved the morphology and the cell viability of hepatocytes (P < 0 .05) and decreased the ROS production. Moreover, 0.05, 0.1 and 0.2 g/L YC in the medium could significantly decreased the ALT and APT activities induced by LPS. In addition, compared with control group, the gene expression related to pro-inflammatory cytokine (il-1β) was significantly up-regulated by LPS, however, addition of 0.05, 0.1 and 0.2 g/L YC could significantly decrease the gene expression of il-1β induced by LPS (P < 0 .05), which was related to that YC could suppress the tlr4/myd88/nfκb signaling pathway in the hepatocytes. Besides, LPS significantly increased the gene expression of apoptosis-related genes including caspase-3, caspase-7 and caspase-9, however, addition of 0.05, 0.1 and 0.2 g/L YC could significantly decreased mRNA levels of apoptosis-related genes induced by LPS (P < 0 .05). To sum up, YC could modulate the MDA-activated oxidative stress by regulating the nrf2 signaling pathway and LPS-activated inflammation by regulating the tlr4/myd88/nfκb signaling pathway in the hepatocytes of grass carp. The results of the present study provide the theoretical basis of yeast culture for solving liver injury in fish.

This study was conducted to evaluate the effect of supplement ferulic acid on growth performance, digestive ability and transport function of amino acids and oligopeptides in the intestine of sub-adult grass carp (Ctenopharyngodon idellus). The experiment was divided into two parts: a. Digestion experiment: healthy grass carp (678.83±1.00 g) were divided into two groups: control group (0 mg/kg FA) and ferulic acid group (100 mg/kg FA) for 2 weeks; b. Growth experiment: healthy grass carp (678.83±1.00 g) were divided into five treatment groups, the control group (FA0) with no ferulic acid and the experimental group supplemented with ferulic acid 50 (FA50), 100 (FA100), 150 (FA150) and 200 (FA200) mg/kg feed for 9 weeks. The results showed that a. Ferulic acid supplementation increased the apparent digestibility of crude protein and crude fat in grass carp. b. Ferulic acid supplementation improved the growth performance and feed efficiency (FE) of grass carp; increased the activities of trypsin and Na+/K+-ATPase; and up-regulated the levels of mRNAs of some neutral and cationic (non-anionic) amino acid transporter proteins (Solute Carrier Family7member1 (SLC7A7), SLC7A8, etc.) and H+/oligopeptide transporter protein 1 (PepT1) gene and protein levels. In addition, ferulic acid promoted the gene expression levels of protein kinase B (Akt), target of rapamycin (TOR); up-regulated the mRNA levels of tail-side-associated homologous frame transcription factor 2 (Cdx2), cAMP response element-binding protein (CREB), and transcriptional co-activator-specific protein 1 (Sp1), and down-regulated the gene and protein levels of protein kinase CβII (PKCβII). In a word, dietary ferulic acid promoted growth performance, digestion, as well as amino acid and oligopeptide transport capacities. Finally, based on regression analyses of percentage weight gain (PWG), FE, specific growth rate (SGR), intestine fold height, trypsin activity, and Na+/K+-ATPase activity, we recommend optimal supplementation levels of ferulic acid in sub-adult grass carp of 92.18–120.60 mg/kg diet.

To elevate the effects of creatine on muscle growth, flesh quality, lipid metabolism and antioxidant responses of aquatic animals, we set up three diets with dietary creatine levels at 0 % (Control), 1 % and 2 % for juvenile grass carp (4.33 ± 0.02 g). Experimental fish were stocked in nine 300-L tanks (30 fish/tank) and randomly assigned with one of the three diets for 8 weeks. We found that 2 % dietary creatine improved the growth performance (SGR) and feed utilization (FCR) of the experimental grass carp. Dietary creatine supplementation further increased the diameter of muscle fibers through elevating the expression levels of muscle growth-related genes (pax3, mrf4, myog, myf5, mef2a, and mef2d) and proteins (Pax3, Myog and Mef2a). Furthermore, both 1 % and 2 % creatine supplementation elevated the muscle flesh quality of grass carp, indicated by the enhanced water holding capacity, improved texture properties, increased flavor compounds (flavor nucleotides and amino acids) content and decreased odorants compounds (2-MIB and GSM) content in the muscle. Dietary creatine supplementation also reduced muscle lipid deposition main forced by suppressing lipogenesis and activating fatty acids β-oxidation. Moreover, the increased antioxidant capability and reduced oxidative stress were found in the muscle of creatine supplementation groups, as evaluated by Nrf2 nuclear-translocation, enzymatic activities, antioxidative genes and proteins expression. Therefore, our study suggested that 1 % or 2 % dietary creatine levels not only promoted the muscle growth, but also enhanced the flesh quality of juvenile grass carp.

Abstract Background The Gα family plays a crucial role in the complex reproductive regulatory network of teleosts. However, the characterization and function of Gα family members, especially Gαq, remain poorly understood in teleosts. To analyze the characterization, expression, and function of grass carp (Ctenopharyngodon idella) Gαq, we identified the Gα family members in grass carp genome, and analyzed the expression, distribution, and signal transduction of Gαq/gnaq. We also explored the role of Gαq in the reproductive regulation of grass carp. Results Our results showed that the grass carp genome contains 27 Gα genes with 46 isoforms, which are divided into four subfamilies: Gαs, Gαi/o, Gαq/11, and Gα12/13. The expression level of Cignaq in the testis was the highest and significantly higher than in other tissues, followed by the hypothalamus and brain. The luteinizing hormone receptor (LHR) was mainly localized to the nucleus in grass carp oocytes, with signals also present in follicular cells. In contrast, Gαq signal was mainly found in the cytoplasm of oocytes, with no signal in follicular cells. In the testis, Gαq and LHR were co-localized in the cytoplasm. Furthermore, the grass carp Gαq recombinant protein significantly promoted Cipgr expression. Conclusions These results provided preliminary evidence for understanding the role of Gαq in the reproductive regulation of teleosts.

Abstract BF/C2 is a crucial molecule in the coagulation complement cascade pathway and plays a significant role in the immune response of grass carp through the classical, alternative, and lectin pathways during GCRV infection. In vivo experiments demonstrated that the mRNA expression levels of BF/C2 (A, B) in grass carp positively correlated with GCRV viral replication at various stages of infection. Excessive inflammation leading to death coincided with peak levels of BF/C2 (A, B) mRNA expression and GCRV viral replication. Correspondingly, BF/C2 (A, B) recombinant protein, CIK cells and GCRV co-incubation experiments yielded similar findings. Therefore, 3 h (incubation period) and 9 h (death period) were selected as critical points for this study. Transcriptome sequencing analysis revealed significant differences in the expression of BF/C2A and BF/C2B during different stages of CIK infection with GCRV and compared to the blank control group (PBS). Specifically, the BF/C2A_3 and BF/C2A_9 groups exhibited 2729 and 2228 differentially expressed genes (DEGs), respectively, with 1436 upregulated and 1293 downregulated in the former, and 1324 upregulated and 904 downregulated in the latter. The BF/C2B_3 and BF/C2B_9 groups showed 2303 and 1547 DEGs, respectively, with 1368 upregulated and 935 downregulated in the former, and 818 upregulated and 729 downregulated in the latter. KEGG functional enrichment analysis of these DEGs identified shared pathways between BF/C2A and PBS groups at 3 and 9 h, including the C-type lectin receptor signaling pathway, protein processing in the endoplasmic reticulum, Toll-like receptor signaling pathway, Salmonella infection, apoptosis, tight junction, and adipocytokine signaling pathway. Additionally, the BF/C2B groups at 3 and 9 h shared pathways related to protein processing in the endoplasmic reticulum, glycolysis/gluconeogenesis, and biosynthesis of amino acids. The mRNA levels of these DEGs were validated in cellular models, confirming consistency with the sequencing results. In addition, the mRNA expression levels of these candidate genes (mapk1, il1b, rela, nfkbiab, akt3a, hyou1, hsp90b1, dnajc3a et al.) in the head kidney, kidney, liver and spleen of grass carp immune tissue were significantly different from those of the control group by BF/C2 (A, B) protein injection in vivo. These candidate genes play an important role in the response of BF/C2 (A, B) to GCRV infection and it also further confirmed that BF/C2 (A, B) of grass carp plays an important role in coping with GCRV infection.

Graphical Abstract Highlight Research • PPE supported the growth indices like final weight, weight gain, SGR, and FCR. • PPE affected the total aerobic bacteria or total lactic acid bacteria (LAB) count, but the enteric gram-negative bacteria count was significantly reduced in the experimental groups. • Add PPE caused a reduced total fungi count in all treated fish. • The histological examination showed enlargement of the villi, depth of the villi, and an increase in goblet cells for the treatments supplemented with PPE. Abstract Pomegranate is considered one of the medicinal herbs rich in antioxidants that can be used in aquaculture to support immunity and health. The objective of this investigation was to ascertain the impact of pomegranate peel (Punica granatum) extract (PPE) on growth performance, the intestinal bacteria count, the total number of fungi and the histological analysis of the grass carp. 105 fingerlings (11.04±0.22g) were distributed among 21 aquariums (60-L) in a completely randomised design (triplicated) and fed diets containing 0, 0.5, and 1% PPE for 70 days at a feeding rate of 3% body weight. A spectrophotometry assessment indicated for PPE that the total phenol content was 151.09 and 175.95 GAE/100 g, and the flavonoid content was 36.04 and 42.89 RE/100 g, respectively. The results of the present work revealed that growth indicators (final weight, weight gain, specific growth rate (SGR), and feed conversion ratio (FCR)) increased (P

The objective of study was to investigate the softening effect and mechanism of Garcinia gummi-gutta on grass carp bones. The pattern of change in the hardness of grass carp bones was studied during pickling using a G. gummi-gutta juice-based marinade at different temperatures (5, 10, 25, and 40 ℃). At the same time, changes in the composition and structure of grass carp bones and in the acidity and pH of the marinade were also determined. The results showed that the hardness of grass carp bones gradually decreased with pickling time, which decreased by 71.5%–79.4% after 25 days of pickling (P < 0.05). The ash content decreased by 11.90%–16.65% (P < 0.05), and the moisture content by 4.23%–13.08% (P < 0.05). The dense and ordered microstructure became loose and porous. This was because the reaction of H+ with hydroxyapatite in fish bones enabled calcium to be dissolved from fish bones and the consumption of H+ in the pickling solution decreased its acidity and increased its pH. Malic acid was played a major role in softening fish bones. Infrared spectroscopic analysis showed that the triple helix structure of fish bone collagen was not destroyed, but the absorption peak corresponding to amide A shifted to a higher wavenumber, suggesting a reduction in the number of hydrogen bonds, which might be related to the loss of hydroxyapatite in fish bones.

Background: The Gα family plays a crucial role in the complex reproductive regulatory network of teleosts. However, the characterization and function of Gα family members, especially Gαq, remain poorly understood in teleosts. To analyze the characterization, expression, and function of grass carp (Ctenopharyngodon idella) Gαq, we identified the Gα family members in grass carp genome, and analyzed the expression, distribution, and signal transduction of Gαq/gnaq. We also explored the role of Gαq in the reproductive regulation of grass carp. Results: Our results showed that the grass carp genome contains 27 Gα genes with 46 isoforms, which are divided into four subfamilies: Gαs, Gαi/o, Gαq/11, and Gα12/13. The expression level of Cignaq in the testis was the highest and significantly higher than in other tissues, followed by the hypothalamus and brain. The luteinizing hormone receptor (LHR) was mainly localized to the nucleus in grass carp oocytes, with signals also present in follicular cells. In contrast, Gαq signal was mainly found in the cytoplasm of oocytes, with no signal in follicular cells. In the testis, Gαq and LHR were co-localized in the cytoplasm. Furthermore, the grass carp Gαq recombinant protein significantly promoted Cipgr expression. Conclusions: These results provided preliminary evidence for understanding the role of Gαq in the reproductive regulation of teleosts. [ABSTRACT FROM AUTHOR]

Simple Summary: Intensive aquaculture decreases immunity and increases diseases that occur in grass carp, which increases economic loss. Hence, improving grass carp immunity is an important strategy for solving the problem of intensive aquaculture. It has been reported that akirin takes part in immune responses. However, the role of akirin in grass carp is unclear. In this study, the akirin gene was isolated from grass carp spleen. The tissue-specific expression of akirin was analyzed. Akirin expression was detected by treatment with LPS, poly (I:C), and A. hydrophila. The immunologic function of akirin proteins was evaluated in HKLs. The findings showed that akirin expression was widely detected in grass carp tissues. Akirin levels were markedly induced via LPS, poly (I:C), and A. hydrophila stimulation in vitro and in vivo. Recombinant grass carp akirin proteins were produced by E. coli. The immune-related genes in HKLs were increased by treatment with recombinant akirin proteins. Intensive aquaculture of grass carp often leads to decreased immunity and increased disease prevalence, resulting in economic losses. Improving grass carp immunity is therefore a critical strategy for addressing these challenges. Akirin reportedly participates in myogenesis, growth, and immune responses. However, its role in grass carp remains unclear. Herein, we isolated akirins from the spleen of grass carp and analyzed their tissue-specific expression. Akirin expression was detected following treatment with poly (I:C), LPS, and Aeromonas hydrophila (A. hydrophila). The immunological function of the akirin protein was evaluated in head kidney leukocytes (HKLs). The results revealed that the coding sequence (CDS) of akirin1 is 570 bp, encoding 189 amino acids. There was one predicted nuclear localization signal (NLS) and two predicted α- helix domains. The CDS of akirin2 is 558 bp, encoding 185 amino acids. There were two predicted NLSs and two predicted α-helix domains. Tissue-specific expression analysis showed that akirins are widely detected in grass carp tissues. akirin1 was highly detected in the brain, kidneys, heart, spleen, and gonads, while akirin2 was highly detected in the brain, liver, gonads, kidneys, spleen, and heart. The mRNA levels of akirins were promoted after treatment with poly (I:C), LPS, and A. hydrophila. Recombinant akirin proteins were produced in Escherichia coli (E. coli). il-1β, ifnγ, il-6, tnfα, il-4, iκbα, and nfκb were markedly increased in grass carp HKLs by treatment with the akirin protein. These results suggest that akirins play a role in the immunological regulation of grass carp. [ABSTRACT FROM AUTHOR]

The hydrodynamics at the fishway entrance play an important role in attracting fish into a fishway. Adjusting the entrance angle of the fishway to allow suitable water flow patterns at the entrance is an effective measure that can be used to improve the attraction efficiency. In this study, we analyzed the movement behavior of grass carp (Ctenopharyngodon idella) in a river channel at a fishway entrance with different fishway entrance angles (30°, 45°, and 60°) and different replenishment velocities (0.1 m/s, 0.2 m/s, and 0.3 m/s). The flow velocity was 0.32–0.50 m/s when the fish head deflected into the entrance under different entrance angles for grass carp. As the entrance angle of the fishway increased, the fish energy consumption increased. The range of energy consumption for grass carp increased from 1.26–3.59 × 10−3 J to 3.32–7.33 × 10−3 J when the entrance angle was increased from 30° to 60°. There was a negative correlation between the entrance angle of the fishway and the deflection angle of the tested fish's head. This research presents a reference that combines fish swimming behavior and hydraulics to optimize the design of fishway entrances. [ABSTRACT FROM AUTHOR]

Ecological operation of hydraulic engineering is essential for the conservation of fishery resources. Water velocity is known to affect the spawning of fishes delivering drifting eggs. This study aims to explore the effects of water velocity stimulation on the ovarian maturation and antioxidant capacity of adult grass carp (Ctenopharyngodon idellus) through laboratory experiments in order to understand the physiological mechanism underlying the response of natural reproduction to ecological flows. We examined the histology, sex hormones and vitellogenin (VTG) concentrations of ovary, and the transcripts of key genes in the hypothalamus-pituitary-gonad (HPG) axis, as well as the antioxidant activities of ovary and liver in grass carp. The results showed that although there was no discernible difference on the ovarian development characteristics of grass carp under water velocity stimulation, estradiol, testosterone, progesterone, 17a, 20bdihydroxy- 4-pregnen-3-one (17a, 20b-DHP), and VTG concentrations were elevated, which was related to the transcriptional regulation of the HPG axis genes. The gene expression levels (gnrh2, fshb, lhb, cga, hsd20b, hsd17b3, and vtg) in the HPG axis were significantly elevated under water velocity stimulation, while those of hsd3b1, cyp17a1, cyp19a1a, hsd17b1, star, and igf3 were suppressed. In addition, appropriate water velocity stimulation could enhance body health status by increasing the activities of antioxidant enzymes in the ovary and liver. The results of this study provide the fundamental knowledge and data support for ecological operation of hydropower projects and river ecological restoration. [ABSTRACT FROM AUTHOR]

BF/C2 is a crucial molecule in the coagulation complement cascade pathway and plays a significant role in the immune response of grass carp through the classical, alternative, and lectin pathways during GCRV infection. In vivo experiments demonstrated that the mRNA expression levels of BF/C2 (A, B) in grass carp positively correlated with GCRV viral replication at various stages of infection. Excessive inflammation leading to death coincided with peak levels of BF/C2 (A, B) mRNA expression and GCRV viral replication. Correspondingly, BF/C2 (A, B) recombinant protein, CIK cells and GCRV co-incubation experiments yielded similar findings. Therefore, 3 h (incubation period) and 9 h (death period) were selected as critical points for this study. Transcriptome sequencing analysis revealed significant differences in the expression of BF/C2A and BF/C2B during different stages of CIK infection with GCRV and compared to the blank control group (PBS). Specifically, the BF/C2A_3 and BF/C2A_9 groups exhibited 2729 and 2228 differentially expressed genes (DEGs), respectively, with 1436 upregulated and 1293 downregulated in the former, and 1324 upregulated and 904 downregulated in the latter. The BF/C2B_3 and BF/C2B_9 groups showed 2303 and 1547 DEGs, respectively, with 1368 upregulated and 935 downregulated in the former, and 818 upregulated and 729 downregulated in the latter. KEGG functional enrichment analysis of these DEGs identified shared pathways between BF/C2A and PBS groups at 3 and 9 h, including the C-type lectin receptor signaling pathway, protein processing in the endoplasmic reticulum, Toll-like receptor signaling pathway, Salmonella infection, apoptosis, tight junction, and adipocytokine signaling pathway. Additionally, the BF/C2B groups at 3 and 9 h shared pathways related to protein processing in the endoplasmic reticulum, glycolysis/gluconeogenesis, and biosynthesis of amino acids. The mRNA levels of these DEGs were validated in cellular models, confirming consistency with the sequencing results. In addition, the mRNA expression levels of these candidate genes (mapk1, il1b, rela, nfkbiab, akt3a, hyou1, hsp90b1, dnajc3a et al.) in the head kidney, kidney, liver and spleen of grass carp immune tissue were significantly different from those of the control group by BF/C2 (A, B) protein injection in vivo. These candidate genes play an important role in the response of BF/C2 (A, B) to GCRV infection and it also further confirmed that BF/C2 (A, B) of grass carp plays an important role in coping with GCRV infection. [ABSTRACT FROM AUTHOR]

As a member of the pattern recognition receptor (PRR) class, scavenger receptor class B type 1 (SRB1) plays a key role in innate immunity. Grass carp (Ctenopharyngodon idellus) ranks among the most extensively cultivated freshwater aquaculture species in China. However, little is known about the function of SRB1 in C. idellus. In this research study, a SRB1 gene was identified in C. idellus, named CiSRB1. The full-length cDNA of CiSRB1 is 2486 bp long, with an open reading frame (ORF) of 2486 bp encoding a 497 amino acid (aa) protein containing a conserved CD36 domain. The identified genomic DNA length of CiSRB1 is 20,042 bp, including 12 exons and 11 introns. The predictive analysis of protein interactions revealed that CiSRB1 could interact with the outer capsid proteins of typical GCRV strains. The tissue distribution of CiSRB1 exhibited age-dependent characteristics. CiSRB1 displayed the highest expression in the intestines and moderate levels in muscle, spleen, liver, and brain of one-year-old grass carp while maintaining relatively low levels in three-year-old grass carp. Following grass carp reovirus (GCRV) infection, notable upregulation of CiSRB1 transcripts was observed in major immune tissues (gills, intestines, spleen, and liver). Furthermore, significant differences were found between one-year-old and three-year-old grass carp, with lower CiSRB1 expression levels being detected in the older group. Additionally, a distinct response to GCRV infection was observed in one-year-old and three-year-old grass carp. It was found that one-year-old individuals had a mortality rate of up to 84% 6 days post-infection (dpi), whereas all three-year-old counterparts survived after GCRV infection. The analysis of GCRV copy numbers across tissues revealed substantially higher levels in one-year-old grass carp compared with their older counterparts, confirming the existence of age-dependent susceptibility to GCRV infection in grass carp. Combined with these results, it was speculated that the decline in cell-surface CiSRB1 expression with age may impede reovirus binding to host cells, potentially explaining why older grass carp demonstrated enhanced resistance to GCRV infection. This observation accentuates the importance of CiSRB1 in the context of GCRV infection and provides insights into age-dependent susceptibility to reovirus. [ABSTRACT FROM AUTHOR]

Gonadotropin-releasing hormone (GnRH) is a key stimulator for gonadotropin secretion in the pituitary and its pivotal role in reproduction is well conserved in vertebrates. In fish models, GnRH can also induce prolactin (PRL) release, but little is known for the corresponding effect on PRL gene expression as well as the post-receptor signalling involved. Using grass carp as a model, the functional role of GnRH and its underlying signal transduction for PRL regulation were examined at the pituitary level. Using laser capture microdissection coupled with RT-PCR, GnRH receptor expression could be located in carp lactotrophs. In primary cell culture prepared from grass carp pituitaries, the native forms of GnRH, GnRH2 and GnRH3, as well as the GnRH agonist [D-Arg6, Pro9, NEt]-sGnRH were all effective in elevating PRL secretion, PRL mRNA level, PRL cell content and total production. In pituitary cells prepared from the rostral pars distalis, the region in the carp pituitary enriched with lactotrophs, GnRH not only increased cAMP synthesis with parallel CREB phosphorylation and nuclear translocation but also induced a rapid rise in cytosolic Ca2+ by Ca2+ influx via L-type voltage-sensitive Ca2+ channel (VSCC) with subsequent CaM expression and NFAT2 dephosphorylation. In carp pituitary cells prepared from whole pituitaries, GnRH-induced PRL secretion was reduced/negated by inhibiting cAMP/PKA, PLC/PKC and Ca2+/CaM/CaMK-II pathways but not the signalling events via IP3 and CaN/NFAT. The corresponding effect on PRL mRNA expression, however, was blocked by inhibiting cAMP/PKA/CREB/CBP and Ca2+/CaM/CaN/NFAT2 signalling but not PLC/IP3/PKC pathway. At the pituitary cell level, activation of cAMP/PKA pathway could also induce CaM expression and Ca2+ influx via VSCC with parallel rises in PRL release and gene expression in a Ca2+/CaM-dependent manner. These findings, as a whole, suggest that the cAMP/PKA-, PLC/PKC- and Ca2+/CaM-dependent cascades are differentially involved in GnRH-induced PRL secretion and PRL transcript expression in carp lactotrophs. During the process, a functional crosstalk between the cAMP/PKA- and Ca2+/CaM-dependent pathways may occur with PRL release linked with CaMK-II and PKC activation and PRL gene transcription caused by nuclear action of CREB/CBP and CaN/NFAT2 signalling. [ABSTRACT FROM AUTHOR]

Grass Carp Reovirus (GCRV) and Aeromonas hydrophila (Ah) are the causative agents of haemorrhagic disease in grass carp. This study aimed to investigate the molecular mechanisms and immune responses at the miRNA, mRNA, and protein levels in grass carp kidney cells (CIK) infected by Grass Carp Reovirus (GCRV, NV) and Aeromonas hydrophilus (Bacteria, NB) to gain insight into their pathogenesis. Within 48 h of infection with Grass Carp Reovirus (GCRV), 99 differentially expressed microRNA (DEMs), 2132 differentially expressed genes (DEGs), and 627 differentially expressed proteins (DEPs) were identified by sequencing; a total of 92 DEMs, 3162 DEGs, and 712 DEPs were identified within 48 h of infection with Aeromonas hydrophila. It is worth noting that most of the DEGs in the NV group were primarily involved in cellular processes, while most of the DEGs in the NB group were associated with metabolic pathways based on KEGG enrichment analysis. This study revealed that the mechanism of a grass carp haemorrhage caused by GCRV infection differs from that caused by the Aeromonas hydrophila infection. An important miRNA–mRNA–protein regulatory network was established based on comprehensive transcriptome and proteome analysis. Furthermore, 14 DEGs and 6 DEMs were randomly selected for the verification of RNA/small RNA-seq data by RT-qPCR. Our study not only contributes to the understanding of the pathogenesis of grass carp CIK cells infected with GCRV and Aeromonas hydrophila, but also serves as a significant reference value for other aquatic animal haemorrhagic diseases. [ABSTRACT FROM AUTHOR]

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This study aimed to employed the effects of five thermal processing methods, namely steaming (SM), boiling (BO), frying (FY), roasting (RO), and vacuum sealing (SV), on the sensory, physicochemical properties, and microbial composition of grass carp meat during refrigerated storage, alongside unheated raw meat (RW) as control. The results showed that thermal treatment improved the sensory quality and shelf life of refrigerated grass carp meat, and their shelf life was RW

Animal health is generally improved by biochar (BC), a promising dietary supplement made from various organic materials including wheat straw, corn cob, home trash, agricultural waste and wood waste. In the current investigation, effects of different BCs inclusion on the growth, digestibility, body composition, hematological indices and mineralization of Ctenopharyngodon idella (6.11±0.02 g; n = 315 fish) fed diets based on sunflower meal (SFM) were investigated over a 60-day period. Seven diets were prepared: first was the control diet i.e., CON and six other diets were supplemented with 2 % different types of BCs, i.e., cotton stick BC (CSBC), wheat straw BC (WSBC), corn cob BC (CCBC), house waste BC (HWBC), grass waste BC (GWBC), and green waste BC (GwBC). A triplicate tank design was employed for each experimental diet, with fifteen fingerlings per tank. Throughout the experimental duration, they were fed 5 % of their live wet weight. The results revealed that CCBC supplementation significantly (p

Enteritis often limits intensive aquaculture, where bile acids (BAs), a group of steroid molecules, are used to prevent intestinal diseases. However, the functions of certain BAs are poorly understood. In this study, grass carp with enteritis (EGC) and healthy grass carp (HGC) were sampled, and the BAs' composition was analyzed. Results showed distinct differences in the BA profiles: EGC exhibited significantly elevated levels of taurodeoxycholic acid (TDCA), lithocholic acid (LCA), glycoursodeoxycholic acid (GUDCA), and glycohyocholic acid (GHCA) (P < 0.05), and decreased levels of TCDCA, taurocholic acid (TCA), and cholic acid (CA) in the intestine compared with their levels in HGC. Subsequently, five diets containing four typical BAs (CA, chenodeoxycholic acid [CDCA], deoxycholic acid [DCA], and LCA) at the same concentration (0.1 %) were formulated to feed the juvenile grass carps (6.29 ± 0.05 g) for 8 weeks. DCA alone increased body weight, reduced the feed conversion ratio (FCR), and ameliorated histological intestinal inflammatory hallmarks. Conversely, individual supplementation with CDCA, LCA, or CA decreased body weight and increased FCR and exacerbated the histological hallmarks of enteritis. Furthermore, DCA markedly reduced the mRNA expression levels of endoplasmic reticulum stress (ERS)-related genes in the intestine, including glucose-regulated protein 78 (GPR78), activating transcription factor 6 (ATF6), inositol-requiring enzyme 1, and protein kinase RNA-like ER kinase, as well as genes encoding proinflammatory cytokines, such as interleukin (IL)-1 beta, IL-8, and tumor necrosis factor α (TNF-α). Supplementation with CDCA, LCA, or CA promoted the expression of ERS- and proinflammatory-cytokine-related genes. Additionally, Actinobacteriota abundance negatively correlated with intestinal mRNA expression levels of TNF-α, ATF6, IL-1β, GPR78, and IL-8, and Candidatus-Arthromitus abundance positively correlated with these inflammatory markers (P < 0.05). In conclusion, our results demonstrated that BAs play differential roles in modulating the enteritis process and that DCA may have a specific anti-inflammatory role in grass carp.

Grass carp hemorrhagic disease is caused by the grass carp reovirus (GCRV). The disease spreads rapidly and has a high fatality rate, which seriously affects grass carp culture. Moreover, the molecular mechanisms underlying grass carp hemorrhagic disease remain unclear. To decipher the effects of GCRV on grass carp tissues, resistant grass carp A (GA) and susceptible grass carp B (GB) were selected through GCRV treatment, and control grass carp C (GC) was also established. The gill, liver, and muscle tissues exhibited different onset symptoms under the influence of GCRV by histological observation. We selected muscle samples with significant differences in symptoms for Illumina RNA sequencing. Analyses using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes revealed 3512, 3074, and 1853 differentially expressed genes between ''GC vs. GB,'' ''GC vs. GA,'' and ''GA vs. GB,'' respectively. Additionally, 40 differential immune-related genes and 28 differential interferon-stimulating genes (ISGs) related to the interferon (IFN) pathway were identified. The expression of immunogene-related genes of GB and GA, such as MDA5, IL-34, NF-KB, TRIM25, SOCS3, CEBPB, and BCL2, and genes associated with the JAK-STAT signaling pathway, such as IRF4, STAT1, STAT3, JAK 1, and JAK 2, was significantly upregulated. The IFN and JAK-STAT signaling pathways were closely related to anti-GCRV infection. The transcriptome data and predicted immune genes and ISGs in this study provide novel insights into the treatment of GCRV.

Abstract Background Ochratoxin A (OTA), a globally abundant and extremely hazardous pollutant, is a significant source of contamination in aquafeeds and is responsible for severe food pollution. The developmental toxicity of OTA and the potential relieving strategy of natural products remain unclear. This study screened the substance curcumin (Cur), which had the best effect in alleviating OTA inhibition of myoblast proliferation, from 96 natural products and investigated its effect and mechanism in reducing OTA myotoxicity in vivo and in vitro. Methods A total of 720 healthy juvenile grass carp, with an initial average body weight of 11.06 ± 0.05 g, were randomly assigned into 4 groups: the control group (without OTA and Cur), 1.2 mg/kg OTA group, 400 mg/kg Cur group, and 1.2 mg/kg OTA + 400 mg/kg Cur group. Each treatment consisted of 3 replicates (180 fish) for 60 d. Results Firstly, we cultured, purified, and identified myoblasts using the tissue block culture method. Through preliminary screening and re-screening of 96 substances, we examined cell proliferation-related indicators such as cell viability and ultimately found that Cur had the best effect. Secondly, Cur could alleviate OTA-inhibited myoblast differentiation and myofibrillar development-related proteins (MyoG and MYHC) in vivo and in vitro and improve the growth performance of grass carp. Then, Cur could also promote the expression of OTA-inhibited protein synthesis-related proteins (S6K1 and TOR), which was related to the activation of the AKT/TOR signaling pathway. Finally, Cur could downregulate the expression of OTA-enhanced protein degradation-related genes (murf1, foxo3a, and ub), which was related to the inhibition of the FoxO3a signaling pathway. Conclusions In summary, our data demonstrated the effectiveness of Cur in alleviating OTA myotoxicity in vivo and in vitro. This study confirms the rapidity, feasibility, and effectiveness of establishing a natural product screening method targeting myoblasts to alleviate fungal toxin toxicity. Graphical Abstract

The production of selenium-enriched fish can contribute to alleviating selenium deficiency in human diets. However, it is still unclear which selenium source, as an additive, can efficiently and cost-effectively produce high-quality selenium-enriched fish. This study evaluated the effects of selenium nanoparticles (SeNP), selenite, and selenomethionine (SeMet) on the growth, antioxidant capacity, selenium content, selenium speciation, and meat quality of grass carp. Ten diets were prepared, including a basal diet (BD) and three concentrations (0.1, 0.3, and 0.9 mg/kg) of SeNP, selenite, and SeMet. A total of 600 fish (250.79 ± 1.57 g) were randomly assigned to 30 tanks (3 tanks/group). Fish were fed the experimental diet three times daily for 60 d. In this study, SeNP most significantly promoted the growth and antioxidant capacity of grass carp, with 0.3 mg/kg SeNP identified as the optimal additive concentration. Additionally, SeNP demonstrated equally excellent bioavailability as SeMet and significantly increased the content of SeMet in grass carp (Ctenopharyngodon idella) muscle. Furthermore, compared to SeMet and selenite, dietary SeNP could more significantly enhance the content of selenocysteine (SeCys2) and methylselenocysteine (MeSeCys) in grass carp muscle tissue. In addition, we have demonstrated that SeCys2 and MeSeCys promote apoptosis of cancer cells (HeLa) through the mitochondrial apoptotic pathway (involving Bax and Bcl-2). Furthermore, as an additive, 0.3 mg/kg SeNP significantly improved the flesh quality of grass carp by reducing crude fat and heavy metal content, as well as increasing the levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and the ratio of n-3/n-6 polyunsaturated fatty acid (PUFA). In summary, SeNP is the most suitable additive for producing selenium-enriched fish.

Vitamin E (VE) is an essential lipid-soluble vitamin that improves the fish flesh quality. However, the underlying molecular mechanisms remain unclear. This study aimed to investigate the effects of VE on growth performance and flesh quality in sub-adult grass carp (Ctenopharyngodon idella). A total of 450 fish (713.53 ± 1.50 g) were randomly divided into six treatment groups (three replicates per treatment) and fed for nine weeks with different experimental diets (dietary lipid 47.8 g/kg) that contained different levels of VE (5.44, 52.07, 96.85, 141.71, 185.66, and 230.12 mg/kg diet, supplemented as dl-α-tocopherol acetate). Notably, the treatment groups that were fed with dietary VE ranging from 52.07 to 230.12 mg/kg diet showed improvement in the percent weight gain, special growth rate, and feed efficiency of grass carp. Moreover, the treatment groups supplemented with dietary VE level of 141.71, 185.66, and 230.12 mg/kg diet showed enhancement in crude protein, lipid, and α-tocopherol contents in the muscle, and the dietary levels of VE ranging from 52.07 to 141.71 mg/kg diet improved muscle pH24h and shear force but reduced muscle cooking loss in grass carp. Furthermore, appropriate levels of VE (52.07 to 96.85 mg/kg diet) increased the muscle polyunsaturated fatty acid content in grass carp. Dietary VE also increased the mRNA levels of fatty acid synthesis-related genes, including fas, scd-1, fad, elovl, srebp1, pparγ, and lxrα, and up-regulated the expression of SREBP-1 protein. However, dietary VE decreased the expression of fatty acid decomposition-related genes, including hsl, cpt1, acox1, and pparα, and endoplasmic reticulum stress-related genes, including perk, ire1, atf6, eif2α, atf4, xbp1, chop, and grp78, and down-regulated the expression of p-PERK, p-IRE1, ATF6, and GRP78 proteins. In conclusion, dietary VE increased muscle fatty acid synthesis, which may be partly associated with the alleviation of endoplasmic reticulum stress, and ultimately improves fish flesh quality. Moreover, the VE requirements for sub-adult grass carp (713.53 to 1590.40 g) were estimated to be 124.9 and 122.73 mg/kg diet based on percentage weight gain and muscle shear force, respectively.