Growth Of Carp Research Articles

Withania coagulans root powder effect on growth, hematology, digestive enzyme activity, antioxidant status, serum immune response, and tolerance against Aeromonas hydrophila in Common Carp

AbstractObjectiveThe use of plant‐derived products in aquaculture has garnered considerable attention due to their potential benefits. This study investigated the impact of supplementing Withania coagulans root powder (WCRP) in the diet of Common Carp Cyprinus carpio on various parameters, including growth performance, digestive enzymes, hematology, antioxidant activity, and immunological aspects.MethodsCommon Carp (mean weight ± standard deviation = 11.69 ± 0.48 g) were divided into four groups in triplicate, receiving different WCRP concentrations (0.0, 1.0, 1.5, and 2.0%; labeled as WCRP0, WCRP1.0, WCRP1.5, and WCRP2.0, respectively) over a 60‐day period, followed by an experimental challenge with Aeromonas hydrophila to assess the relative percentage survival (RPS) over 14 days.ResultResults showed that Common Carp receiving WCRP1.5 and WCRP2.0 demonstrated significantly improved growth performance, with reduced feed conversion ratios (FCRs) being particularly evident in WCRP1.5. Polynomial contrasts indicated significant linear and quadratic effects on weight gain and FCR. Additionally, WCRP1.5 and WCRP2.0 supplementation led to significantly higher activity of digestive enzymes (lipase and protease). Hematological parameters, including white blood cells, red blood cells, hemoglobin, and hematocrit, were significantly elevated in fish that were fed WCRP1.5 and WCRP2.0 compared to the control group. Moreover, serum parameters, such as total protein, albumin, globulin, lysozyme, catalase, superoxide dismutase, and total immunoglobulins, were significantly enhanced in WCRP1.5‐ and WCRP2.0‐treated fish. Notably, the WCRP1.5 group showed the lowest serum cortisol levels. The RPS was highest in WCRP1.5 (73.77%), followed by WCRP2.0 (70.43%), compared to the other groups.ConclusionIn conclusion, supplementation with WCRP1.5 and WCRP2.0 effectively improved both growth and health parameters in Common Carp.

Individual and combined effects of dietary chlorogenic acid and quercetin supplementation on the growth, lipid metabolism and flesh quality of grass carp, Ctenopharyngodon idellus

The purpose of this study was to evaluate the individual and combined effects of dietary chlorogenic acid and quercetin supplementation on the growth, lipid metabolism and flesh quality of Ctenopharyngodon idellus (C. idellus). Fish (59.7 ± 0.3 g) were fed for 60 days with five diets, including a basal diet not added (CON) or added with chlorogenic acid (CGA, 400 mg/kg), quercetin (QC, 400 mg/kg), and their combinations (CGA:QC=1:1) with 400 mg/kg and 800 mg/kg (CGA:QC-400; CGA:QC-800). The weight gain was increased (+4.00 %, +4.41 %), and the feed conversion ratio was decreased (-0.07, -0.08) by individual supplementation with CGA and QC (P<0.05), but not by their combinations (P>0.05). In addition, dietary CGA and QC promoted the apparent digestibility of dry matter and protein and the activities of intestinal amylase and protease (P<0.05). The CGA, QC and CGA:QC-800 groups presented higher activities of flesh superoxide dismutase, flesh glutathione peroxidase (GSH-Px) and serum GSH-Px, as well as lower contents of protein carbonyl and malondialdehyde (MDA) in flesh and MDA in serum than those of CON group (P<0.05). An increase in flesh hardness, water-holding capacity, and total collagen, heat-insoluble collagen and n-3 polyunsaturated fatty acids contents was observed in the CGA, QC and CGA:QC-800 groups (P<0.05). The four supplements reduced mesenteric lipid-somatic index, flesh n-3/n-6 ratio and serum triglycerides (P<0.05), and the CGA:QC-400 and CGA:QC-800 groups also showed lower lipid content in flesh than CON group (P<0.05). Taken together, the individual supplementation of dietary CGA and QC enhanced the growth performance, lipid metabolism and flesh quality of C. idellus, and their combination presented synergistic effect only on lipid metabolism.

Effect of Dietary Moldavian Balm (Dracocephalum moldavica L.) on Growth Performance, Antioxidant Status, Immune Response, and Gene Expression of Common Carp (Cyprinus carpio)

Abstract Chemical compounds used to prevent and control fish disease often cause environmental hazards; thus, alternative approaches as new and effective strategies are needed. The current investigation was performed with the aim of exploring the effects of dietary Moldavian balm (MB, Dracocephalum moldavica L.) on the growth, immune parameters, and antioxidant status of common carp (Cyprinus carpio). Fish (n=300, w=3.80±0.02 g) in four groups in triplicates were supplemented with 0%, 0.5%, 1%, and 2% MB. After 42 days, it was found that feed supplements increased final weight (FW), weight gain (WG), and specific growth rate (SGR) and decreased the food conversion ratio (FCR) (P&lt;0.05). In addition, fish supplemented with 2% MB significantly showed higher serum total protein (TP), alternative complement pathway (ACH50), and glutathione peroxidase (GPx) (P&lt;0.05). The 0.5% MB-supplemented fish represented higher levels of LYZ, alkaline phosphatase (ALP), total Ig, and ACH50 in their skin mucus in comparison with the unsupplemented fish (P&lt;0.05). The results also indicated that 2% MB resulted in a significantly higher expression level of intestinal tumor necrosis factor (TNF- α) (P&lt;0.05); however, the level of LYZ, interleukin-1β (IL-1 β), and TLRs decreased in supplemented fish. CAT and SOD expressions were increased in 0.5% MB supplement. In conclusion, MB could be recommended as an efficient feed additive to boost common carp’s growth, immunity, and health status.

Dietary Clostridium butyricum metabolites mitigated the disturbances in growth, immune response and gut health status of Ctenopharyngodon idella subjected to high cottonseed and rapeseed meal diet

Cottonseed meal and rapeseed meal exhibit a potential for fishmeal substitute in grass carp feed, while their excessive use contribute to growth decline and weakening immunity of aquatic animals. Clostridium butyricum metabolites (CBM) was recognized as a functional additive due to its antioxidant properties and maintenance of intestinal microbiota balance. CBM was added to a high of cottonseed and rapeseed meal diet to determine its effects on growth, immunity, and intestinal microbiota alterations of grass carp (Ctenopharyngodon idella) over 56 days. Eight hundred grass carp (mean weight, around 50 g) were randomized to five treatments and fed with the basic diet (CON), CBM0 diet (28 % cottonseed and 27 % rapeseed meal), and CBM diets (CBM0.5, CBM1, and CBM2, namely CBM0 diet supplemented with 500, 1000, and 2000 mg kg−1 CBM). The results indicated that compared to CBM0, The ingestion of 1000 mg kg−1 CBM diet by grass carp significantly promoted growth as measured by intestinal lipase activity, villus height, and muscle thickness. Moreover, accompanied by a decrease in intestine MDA content, and enhance antioxidant capacity by activating Keap1/Nrf2 signaling pathway to increase enzyme activities (SOD, CAT and T-AOC) and corresponding gene expression (mnsod, cat, gsto and gpx1) in the intestine of grass crap fed CBM1 diet. The dietary CBM1 diet increased serum levels of C3 and IgM, increased ACP activity and expression of the corresponding anti-inflammatory factors (tgf-β1 and il-15), and suppressed the expression of pro-inflammatory factors (tnf-α and il-12β), resulting in enhanced immunity. The dietary CBM1 diet up-regulates gene expression of tight junction proteins (zo-1, occludin, occludin7a and occludin-c), coupled with the decreases in DAO and D-lactate contents, implying that the decreased mucosal permeability could be observed in the gut. The dietary CBM1 diet largely altered the intestinal microbial community, especially reducing the relative abundance of intestinal pathogenic bacteria (Streptococcus and Actinomyces). And it significantly increased the content of short-chain fatty acids (acetic acid, butyric acid, isobutyric acid, propionic acid and isovaleric acid). Taken above, dietary CBM supplementation improved growth in grass carp and attenuated the intestinal oxidative stress, inflammation and microflora dysbacteriosis caused by high proportions of cottonseed and rapeseed meal diets.

Foodborne iron overload induces oxidative stress and causes mitochondrial damage in the liver of grass carp (Ctenopharyngodon idellus)

Iron is essential to biological processes such as energy metabolism and oxygen transport. However, excessive iron can cause iron overload and ultimately result in tissue damage. To date, the damage mechanism of foodborne iron overload in aquatic animals is still unclear. This study used grass carp (Ctenopharyngodon idellas) as the research subject to establish a chronic iron overload model by feeding diets with different iron levels, and combined in vitro experiments to investigate the mechanisms of iron overload-induced damage. The growth performance and liver HE staining indicated that a high‑iron diet led to decreased growth in grass carp, accompanied by hepatic iron deposition. ELISA and qRT-PCR analysis data revealed that a high‑iron diet disrupted the antioxidant balance and modulated the expression of genes associated with iron metabolism. CCK-8 determination results revealed that treatment of L8824 cells with ferri ammonii citras (FAC) resulted in iron overload, led to disruption of iron metabolism and enhanced the intracellular production of reactive oxygen species (ROS), and caused lipid peroxidation. Furthermore, qRT-PCR analysis results showed that the treatment of L8824 cells with FAC resulted in a significant up-regulation of genes associated with antioxidant, apoptosis, and necrosis pathways, and increased the rate of apoptosis. In addition, fluorescence microscopy observation and mitochondrial DNA detection data showed that excess iron could increase the iron accumulation in mitochondria and the production of mtROS, reduce the mitochondrial membrane potential, and finally cause mitochondria damage. In conclusion, our research offers invaluable insights that iron overload leads to disrupted intracellular iron pool stability, causing mitochondrial damage and oxidative stress, eventually causing cell death.

Effects of Taurine and Vitamin C on the Improvement of Antioxidant Capacity, Immunity and Hypoxia Tolerance in Gibel Carp (Carrassius auratus gibeilo).

To investigate the effects of taurine and vitamin C on gibel carp (Carrassius auratus gibeilo), fish (41.85 ± 0.03 g) were fed three diets with 0% taurine + 0% vitamin C (D0), 0.1% taurine + 0% vitamin C (D1), and 0.1% taurine + 0.1% vitamin C (D2) for 8 weeks. Then 12-hour hypoxic stress test was conducted. The results showed that weight gain rate (WGR), specific growth rate (SGR), and sustained swimming time (SST) were significantly increased in the D2. CAT, SOD, T-AOC, and GSH were increased. GSH-Px and il-6 were decreased in D1 and D2. In hypoxia, CAT and T-AOC were decreased, while GSH, sod, and nrf2 were the highest in D1. Compared to normoxia, GSH-Px was increased, while SOD and MDA were decreased. Il-10 and nf-κb were increased. Vegf, epo, and ho-1 were increased and they all were higher than that in normoxia. The number of gill cell mitochondria and survival rate (SR) of gibel carp had an increasing trend but no significant difference among groups. In conclusion, taurine with vitamin C improved the growth and SST of gibel carp, and taurine and taurine with vitamin C improved antioxidant capacity, immunity, and hypoxia tolerance.

Effect of exercise intensity on growth performance, serum biochemistry parameters, liver antioxidant capacity, and intestinal health of common carp (Cyprinus carpio) in recirculating aquaculture system

This study examined the impact of different exercise intensities on the growth performance, serum biochemistry, liver antioxidant capacity, and intestinal health of common carp (Cyprinus carpio). A total of 270 common carp with an initial weight of 63.91 ± 1.45 g were divided into three groups: a Sustained Exercise group [SE, 1 bl/s (body length per second), 24 h/day], an Intermittent Exercise group (IE, 1 bl/s, 8 h/day), and a Control group (CG, 3 cm/s) for a 90-days experiment. The results demonstrated that exercise substantially improved weight gain rates in common carp. Analysis of serum biochemical parameters revealed that increased exercise intensity significantly reduced levels of triglycerides (TG), total cholesterol (T-CHO), and glucose (GLU) (P < 0.05). Post-exercise evaluations also indicated significant reductions in immune-related markers, including lysozyme (LZM), aspartate aminotransferase (AST), and alanine aminotransferase (ALT). Regarding liver antioxidant enzyme activities, the levels of glutathione peroxidase (GSH-Px) and total superoxide dismutase (T-SOD) were significantly higher in the IE group relative to the CG group (P < 0.05). Conversely, the total antioxidant capacity (T-AOC) was significantly lower in the SE group than in the CG group (P < 0.05). In terms of intestinal health, intermittent exercise significantly reduced the expression of pro-inflammatory cytokine genes and increased gut villus length. Additionally, an increase in exercise intensity significantly enhanced the activities of intestinal amylase and lipase. Analysis of the intestinal microbiota through 16S rRNA sequencing revealed that intermittent exercise fostered a more diverse microbial community. Specifically, with an increase in exercise intensity, the relative abundance of Fusobacteriota rose, while those of Firmicutes decreased. At the genus level, the abundances of Cetobacterium and Aeromonas increased, contrasting with declines in Muribaculaceae, Bacteroides, and Escherichia-Shigella. PICRUSt2 functional predictions suggest that exercise might modify the intestinal environment by increasing the prevalence of pathogenic bacterial communities, potentially leading to intestinal damage and adversely affecting the physiological state of the intestine. An observed increase in riboflavin metabolism in the SE group likely contributed to its markedly improved growth performance relative to other groups. In summary, sustained exercise at 1 bl/s improved growth and intestinal digestive enzyme activity in common carp. However, it also induced stress, potentially compromising physiological health, liver function, and immune strength, consequently elevating the risk of disease. These findings provide crucial insights for optimizing growth and physiological health in common carp and other fish species in recirculating aquaculture systems through exercise.

Synergistic effects of dietary selenium nanoparticles and vitamin C improve growth performance, immune response, and antioxidant status of juvenile common carp (Cyprinus carpio)

IntroductionThis study aimed to investigate the synergistic effects of dietary selenium nanoparticles (Se-NPs) and vitamin C (VC) on growth, body composition, antioxidant defense, immunity, and serum biochemical indexes of common carp (Cyprinus carp) juveniles. MethodologyThe test diets were supplemented with three levels of Se-NPs (0, 0.5, and 1 mg/Kg) and three levels of VC (0, 500, and 1000 mg/Kg): the basal diet without supplemental Se-NPs and VC (VC0SeNPs0; control), 0.5 mg Se-NPs /Kg (VC0SeNPs0.5), 1 mg Se-NPs /Kg (VC0SeNPs1), 500 mg VC/Kg (VC500SeNPs0), 1000 mg VC/Kg (VC1000SeNPs0), 500 mg VC/Kg and 0.5 mg Se-NPs (VC500SeNPs0.5), 1000 mg VC/Kg and 0.5 mg Se-NPs (VC1000SeNPs0.5), 500 mg VC/Kg and 1 mg Se-NPs (VC500SeNPs1), 1000 mg VC/Kg and 1 mg Se-NPs (VC1000SeNPs1). The fish were randomly divided into nine experimental groups in triplicate tanks per treatment and fed on their respective diets for 60 days. ResultsThe findings displayed that fish fed with VC500SeNPs1 and VC500SeNPs0.5 diets had significantly (P < 0.05) higher specific growth rates when compared to other groups. The lowest feed conversion ratio was detected in the VC1000SeNPs1 group and the highest in the control group (P < 0.05). VC, Se-NPs, and their interaction had no significant effect on serum malondialdehyde, ACH50, and IgM (P > 0.05). However, the best parameters associated with antioxidant capacity (higher serum levels of superoxide dismutase and total reduced glutathione) and physiological status (higher concentration of serum globulin and lower amounts of aspartate aminotransferase and lactate dehydrogenase) belonged to the VC1000SeNPs1 and VC500SeNPs1 groups. The results suggest that the Se-NPs and VC combination more efficiently influence the common carp’s growth performance, antioxidant status, immunity, and physiological parameters. ConclusionOverall, the diet enriched with 500 mg VC and 1 mg Se-NPs /Kg (VC500SeNPs1) is suitable for boosting the growth and immunity of common carp.

Effects of Dietary Lipid Levels on the Growth, Muscle Fatty Acid and Amino Acid Composition, Antioxidant Capacity, and Lipid Deposition in Mirror Carp (Cyprinus carpio).

In fish, increasing the crude lipid level of feed can save protein and improve feed utilization. Mirror carp (Cyprinus carpio) is one of the most widely farmed fish species in the world. In this study, mirror carp larvae were fed isonitrogenous diets with different lipid levels (3%, 5%, 7%, 9%, 11%, and 13%). The rearing trial lasted for eight weeks. The results revealed that when the fat content was 9%, the AWGR, WGR, and FCR were highest, whereas FCR was lowest. The AWGR was correlated with the dietary lipid level, and the regression equation was y = -2.312x2 + 45.01x + 214.49. Compared with those in the control group, the T-CHO and TG contents were significantly greater in the 13% lipid content groups and significantly lower in the 9% lipid content groups (p < 0.05). In terms of muscle quality, the contents of MUFAs, PUFAs, and DHA + EPA were significantly greater than those in the other experimental groups (p < 0.05). Oil red O staining revealed a lipid content of 13% with severe fat deposition. In addition, the results of the analysis of antioxidant enzyme activity revealed that the activities of GSH, CAT and T-AOC were significantly greater at the 9% lipid content, and that the MDA content was significantly greater at the 13% lipid content (p < 0.05). Similarly, the mRNA levels of GH, IGF-I, FAS, and LPL were significantly highest at a lipid level of 9% (p < 0.05). The above results revealed that the optimal dietary lipid requirement for the fast growth of mirror carp (6.86 ± 0.95 g) was 9.74% on the basis of nonlinear regression analysis of the AWGR. The dietary lipid level (9%) improved the growth, stress resistance, and lipid utilization of mirror carp to a certain extent.

Whole-genome resequencing and RNA-seq analysis implicates GPR75 as a potential genetic basis related to retarded growth in South China carp (Cyprinus carpio rubrofuscus)

The south China carp (Cyprinus carpio rubrofuscus) is an indigenous and important fish species, widely cultured in south China. However, part of individuals experienced retarded growth, the genetic basis of which has yet to be elucidated. In this study, whole-genome resequencing of 35 fast-growing and 35 retarded-growing south China carp were conducted to identify promising genes associated with retarded growth. Twelve candidate SNPs were detected and annotated to the Gpr75 gene, which has been reported to be related with body weight through regulating insulin homeostasis. RNA-seq analysis of muscle suggested that differentially expressed genes were significantly enriched in the insulin signaling pathway. Additionally, the fasting serum insulin level was significantly lower while the blood glucose level was significantly higher in the retarded-growing group. Our preliminary study provides insights into the genetic basis underlying the retarded growth and may facilitate further genetic improvement of south China carp.

Effects of Environmental Enrichment on the Growth, Gonadal Development, and Welfare of the Chinese Hooksnout Carp (Opsariichthys bidens)

To investigate the effects of environmental enrichment on the growth and welfare level of the Chinese hooksnout carp (Opsariichthys bidens), an experiment was carried out for 56 d with four types of enrichment environments: low-density physical enrichment, high-density physical enrichment, low-density social enrichment, and high-density social enrichment. The experimental results revealed that both physical and social enrichment treatments positively affected the growth and gonadal development of O. bidens. The physical enrichment treatment was found to increase the antioxidants’ content, such as CAT, SOD, and GSH, in the liver of O. bidens. Moreover, this treatment was able to lead to a reduction in MDA content and enhancement of the fish’s antioxidant capabilities. Behavioral observations, cortisol level analysis, and pcna gene expression analysis indicated that the physical enrichment treatment redused the clustering, aggression, and stress behaviors of O. bidens, maintaining them in a low-stress state. In most respects, the high-density physical enrichment has more positive effects than the low-density one. In contrast, the social enrichment treatments resulted in higher stress levels for O. bidens.

Alpha-linolenic acid/linoleic acid ratio can effectively promote muscle growth and protein deposition in grass carp (Ctenopharyngodon idella)

Polyunsaturated fatty acids (PUFAs) promoted the muscle structure (muscle fiber cross-sectional area and diameter, as well as thickness of the connective tissue surrounding muscle fibers-endomysium) and taste (fishy) of fillets. As members of the omega-3 and omega-6 PUFA family, alpha-linolenic acid (ALA) and linoleic acid (LNA) have important functions. This study explores influences of ALA/LNA ratio on muscle growth and protein deposition and its mechanisms. Six different diets containing ALA/LNA ratios (0.03, 0.47, 0.92, 1.33, 1.69, and 2.15) were fed to grass carp (Ctenopharyngodon idella) for 9 weeks. Results showed that according to the quadratic regression model, the optimal ALA/LNA ratios of grass carp were 1.12 and 1.22 using malondialdehyde content and muscle fiber diameter as indicators, respectively. Optimum ALA/LNA ratio promoted hypertrophy of myofibers, which might be attributed to genes related to myofiber development (myogenic determinant, myogenin, myosin heavy chain, myogenic regulatory factor 4 and myogenic factor 5). Optimum ALA/LNA ratio enhanced protein deposition, which might be associated with the promotion of protein synthesis (insulin-like growth factors-1, phosphoinositide 3-kinase, target of rapamycin), and inhibition of the ubiquitin-proteasome system and autophagy-lysosome system to inhibit protein degradation. In addition, optimum ALA/LNA ratio enhanced muscle amino acid composition and antioxidant capacity of fish.

Exploring Arthropods as Sustainable Protein Source and the Effect of Cockroach Meal Supplemented Diet on the Growth of Fish

This comprehensive study centres on exploring the arthropods as sustainable protein sources, addressing both human dietary needs and livestock feed requirements. A diverse set of twenty arthropod species were collected from different locations of Kanyakumari District and the species were identified based on the identification keys pertaining to morphological characters. The surveyed animals comprises of Insects: Dragon Fly (Pantala sp.), Western subterranean termite (Reticulitermes sp.), Longhorn beetle (Callipogon sp.), Asiatic rhinoceros beetle (Oryctes rhinoceros), Brown grasshopper (Melanoplus sp.), Bush cricket (Tettigonia sp.), Grasshopper (Diabolocatantops sp.), Housefly (Musca domestica), Cockroach (Periplaneta americana), Termite (Macrotermes sp.), Black carpenter ant (Camponotus sp.), Red carpenter ant (Camponotus sp.); Crabs: Mottled light footed crab (Grapsus albolineatus), Sartoriana sp., Asian paddle crab (Charybdis sp.,),Box crab (Calappa sp.,), Asian shore crab (Hemigrapsus sp.); Millipedes: Yellow spotted millipede (Harpaphe haydeniana), Pill millipede (Arthrosphaera disticta) and African giant millipede (Thyropygus descriptus) were analyzed for the protein content. The samples were tested for protein using Biuret’s method. Among the different arthropods tested insects- Callipogon sp. and Periplaneta americana, crabs - Calappa sp. and Charybdis sp. and Myriapod - Harpaphe haydeniana, exhibited the highest protein content. Crustaceans demonstrated the highest protein content when compared to insects and millipedes. However, since cockroaches are generally considered as a pest and repugnant in human dwelling, it would be ideal to convert cockroach as a sustainable protein source in aquaculture. Moreover. since cockroach showed a higher protein content of 6.146 2.024 mg/ml it was tried as a supplement feed for fish. Cockroach meal was prepared in two different proportions (2% and 3%) to evaluate its impact on the growth of Koi carp fish in comparison with cockroach free meal as control. The inclusion of 3% cockroach powder in the fish meal augmented the growth of Koi carp when compared to the control during a fifteen-day study period. Thus, this study has tapped a potential protein source from insects. Cockroach can be used as an ideal fish feed as it contributes to the pursuit of sustainable and environmentally friendly animal feed source.

Evaluation of four novel non-grain protein sources completely replacing soybean meal on growth performance, serum biochemistry, amino acid transport and intestinal health of grass carp (Ctenopharyngodon idella) at different water temperatures

To investigate the effects of non-grain protein source and water temperature on growth and feed utilization differences of grass carp, the effects of different protein sources on the growth performance, serum biochemistry, digestive enzymes, amino acid transport and intestinal health of grass carp were studied at 24 °C, 28 °C and 32 °C. In this study, a total of 1350 grass carp (Ctenopharyngodon idella) (initial weight 5.00 ± 0.02 g) were selected, and Clostridium autoethanogenum protein (CAP), Tenebrio molitor meal (TMM), cottonseed protein concentrate (CPC) and Chlorella powder (CHP) were used as a single protein source to completely replace soybean meal for 56 days. The results showed that the final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR) and protein efficiency ratio (PER) of grass carp increased significantly with the increasing temperature (P < 0.001). The CHP and SBM groups showed no significant differences in FBW, WGR, SGR and PER (P > 0.05), which were higher than the CAP, TMM and CPC groups (P < 0.001). The alanine transaminase (ALT), aspartate aminotransferase (AST), total protein (TP) and triglyceride (TG) concentrations of grass carp at 32 °C were significantly lower than those at 24 °C and 28 °C (P < 0.001). The acid phosphatase (ACP) activity decreased significantly with the increase of temperature (P = 0.001). The amylase (AMS) activity of the TMM, CPC and CHP groups was significantly lower than that of the SBM and CAP groups (P < 0.001), and the ACP and lipase (LPS) activities in the TMM group were significantly lower than those in the SBM group (P < 0.001). In addition, the interaction between temperatures and protein sources significantly affected the gene expression levels of amino acid transport including solute carrier family 1 member 3 (SLC1A3), solute carrier family 7 member 1 (SLC7A1), solute carrier family 7 member 5 (SLC7A5), solute carrier family 15 member 1b (SLC15A1b), solute carrier family 7 member 7 (SLC7A7), target of rapamycin (TOR), 4E binding protein 1 (4E-BP1) and ribosomal protein S6 kinase 1 (S6K1), intestinal inflammatory including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-8 (IL-8), interleukin-10 (IL-10) and tight junction proteins (occludin, claudin1, claudin3, claudin7 and claudin11) (P ≤ 0.001). Collectively, our results indicated that CHP could be a potential protein source in the case of complete replacement of soybean meal in grass carp.

Effects of coated Enterococcus faecium on the growth performance, immunity, digestive enzyme activity, intestinal morphometry, and microbiota of crucian carp (Carassius auratus gibelio)

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.

Carp growth, body composition, lipidomics, and flesh quality in response to replacing dietary fish meal with a complex protein source

Alternatives to fish meal (FM) in fish feed are urgently required in aquaculture. We therefore examined the effect of replacing FM with a complex protein source (CPS) comprising soybean meal, peanut meal, corn protein meal, feather meal, and yeast protein, on carp (Cyprinus carpio) growth, body composition, lipidomics, and flesh quality. Lipidomics analysis was conducted to reveal the impact of dietary changes on fish lipid composition and metabolism, which is closely related to flesh quality and nutritional value. Over an eight-week growth trial, fish meal was replaced with CPS at 0 % (FM only), 20 %, 40 %, 60 %, 80 %, or 100 %. Weight gain and other growth parameters did not differ significantly among the treatments. Lipid deposition (LD) was positively correlated, and protein deposition negatively correlated, with CPS levels. LD and fillet ether extract were significantly elevated at 100 % CPS, whereas superoxidase dismutase expression, claudin-1 expression, and lipase activity were significantly reduced. The n-3 PUFA level and n-3/n-6 PUFA ratio were significantly lower following CPS feeding, reducing flesh quality. These findings indicate that CPS successfully replaced 60–80 % of dietary FM in carp diets, while the 100 % replacement group provided insights into the comprehensive effects of total substitution. Future studies will further optimize formulations based on these results to resemble practical production more closely. CPS with nutrient supplementation may therefore present a viable and safe partial replacement for dietary FM.

Effect of pellet-size on fish growth, feeding behaviour and natural food web in pond polyculture

In carp-tilapia pond polyculture, carps are stocked once and usually harvested each 12 to 24 months, while, tilapia is stocked and harvested each 4 to 6 months. Therefore, per carp cycle there are 3 to 6 tilapia cycles. With time, carps grow bigger while tilapia reach only 10 to 50% the mass of carps. Pellet size can offer a feeding management tool in the ponds with large carp and small tilapia. This experiment investigated whether pellet-size can steer the growth of large carps (∼ 500 g) and small tilapias (∼30 g) in polyculture ponds. Four pellet-size treatments were applied in this study, each with a different combination of small (2 mm) and large (6 mm) pellets (on weight basis): S100L0 (100% small, 0% large), S50L50 (50% small, 50% large), S25L75 (25% small, 75% large) and S0L100 (0% small, 100% large). Each treatment was applied to six replicate ponds. The experiment lasted for 8 weeks. The treatments did not alter carp production, but tilapia production was highest in S100L0 treatment ponds (P < 0.001). The fish always needed more time to consume large pellets than the small pellets. Small pellets were consumed much quicker when the portion fed was small, indicating strong competition. A similar trend was observed with large pellets but the difference in feed intake time across the treatments was smaller than with small pellets. This is because tilapia ate the majority of both small and large pellets while carps ate less pellets. Tilapia at treatment S0L100 had a lower protein and fat content and a higher ash content than at the other pellet-size treatments. Carp's body composition remain unaffected by pellet-size treatment except the ash content of rohu which was highest at S100L0 and lowest at S0L100. By volume, tilapia had a higher amount of food in the stomach in treatments S100 L0 and S50L50 than in the other treatments. In contrast, more food was found in the gut of rohu in treatments S0L100 and S25L75 than in the other treatments. Pellet-size treatments did not affect water quality and the pond food web (P > 0.05) except phytoplankton diversity which was positively influenced when feeding more large pellets. The plankton population increased with the progression of the experiment, suggesting the food web was not fully exploited. In conclusion, pellet-size proves to be a feeding management tool to steer the production of tilapia as well as of total fish biomass, but not of carp's biomass in carp-tilapia pond polyculture.

Feasibility evaluation of cottonseed protein concentrate to replace soybean meal in the diet of juvenile grass carp (Ctenopharyngodon idellus): Growth performance, antioxidant capacity, intestinal health and microflora composition

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

Effects of the medicinal plant, Tamarindus indica, as a potential supplement, on growth, nutrient digestibility, body composition and hematological indices of Cyprinus carpio fingerlings

Tamarindus indica, a beneficial herb, has many health benefits but there is limited research on its use in fish nutrition industry. The current study investigated the effects of incorporating extracts of T. indica into the canola meal-based diets of Cyprinus carpio (common carp); following which, the growth, digestibility, carcass and hematological markers were assessed. A total of six diets were formulated with varying concentrations of T. indica extracts (TIE) viz, 0 %, 0.5 %, 1 %, 1.5 %, 2 % and 2.5 %. The fish (N = 270, 15 fish/tank with triplicates) in each tank were fed experimental diets for 70 days. The study demonstrated that TIE supplementation significantly improved the growth of common carp when compared to 0 % TIE level (control). The best results were observed at 1 % TIE level for the specific growth rate (1.68 ± 0.03 %), weight gain (15.00 ± 0.57 g), and feed conversion ratio (1.36 ± 0.05). Conversely, the 2.5 % TIE level gave the least improvement in terms of growth performance. Specifically for nutrient digestibility, the maximum values of crude protein (CP, 67.60 ± 0.83 %), crude fat (CF, 67.49 ± 0.45 %) and gross energy (GE, 70.90 ± 0.56 %) were recorded at 1 % TIE level. In addition, the best results of body composition (protein: 63.92 ± 0.06 %, ash: 18.60 ± 0.03 %, fat: 7.12 ± 0.02 % and moisture: 10.36 ± 0.04 %) and hematological indices, were measured in carps fed with 1 % supplementation level. In conclusion, the overall health of C. carpio fingerlings was improved with TIE supplementation in the diet containing 1 % TIE.

Effect of long-term temperature-controlled rearing on growth traits and sexual maturity of common carp (Cyprinus carpio)

Many economically important fish have a long sexual maturation cycle, with the first sexual maturation time exceeding four years, which poses a long-term challenge for the cultivation of excellent varieties of these fish. Gonadal development and reproductive timing of fish are closely related to changes in environmental temperature. This study used the common carp as an economic fish model and set up three aquaculture modes for a one-month old common carp population: constant temperature test group (CTTG), normal temperature control group (NTCG), and variable temperature control group (VTCG). A long-term (approximately 11 months), temperature-controlled aquaculture experiment was conducted. The results of growth traits and gonadal development tests showed that at 10 months, the body length and weight of the CTTG were significantly higher than those of the other two groups. At seven months, the gonadosomatic index (GSI) value of CTTG was also significantly higher than that of the other two groups; At 10 months, the serum estradiol (E2) concentration of CTTG was significantly higher than that of the other two groups, while the testosterone (T) levels of VTCG and CTTG were significantly higher than those of NTCG, and only the 11-ketotestosterone (11-KT) concentration of VTCG was significantly higher than that of the other two groups. Simultaneously, qPCR analysis of sex hormone regulatory genes revealed that the expression of Cyp19a1a in CTTG ovaries was significantly higher than that in NTCG and VTCG ovaries, whereas the expression of Cyp11b and Hsd11b2 in VTCG ovaries was significantly higher than that in NTCG and CTTG ovaries. At 12 months, artificial reproduction revealed that only fish from the CTTG (66.67%) successfully laid eggs and fertilized normally. The results indicate that long-term constant temperature cultivation at 28 °C starting from the juvenile stage is not only beneficial for the body growth of common carp, but also promotes their gonadal development. This may be due to the conversion of T into E2 by Cyp19a1a in the common carp, ultimately facilitating the functional development of gonadal tissue under hypothalamus-pituitary-gonadal (HPG) axis regulation, normal egg laying, and fertilization. This study reduced the normal first sexual maturation time of common carp by at least 50% and provides a reference for the rapid cultivation of excellent varieties of other economically important fishes.