Growth Performance Of Grass Carp Research Articles

A new insight on alleviating the inhibitory effect of aflatoxin B1 on muscle development in grass carp (Ctenopharyngodon idella): the effect of 4-methylesculetin in vivo and in vitro

Aflatoxin B1 (AFB1), an important fungal toxin, exists mainly in plant feed ingredients and animals consuming feed contaminated with AFB1 will have reduced growth and impaired health condition mainly due to oxidative stress and reduced immunity. Our previous study found that AFB1 caused oxidative damage and inhibited muscle development of zebrafish. 4-methylesculetin (4-ME), a coumarin derivative, is now used in biochemistry and medicine widely because of its antioxidant function. Whether 4-ME could alleviate the inhibition of muscle development in grass carp induced by AFB1 has not been reported. In this experiment, 720 healthy grass carp (11.40 ± 0.01 g) were randomly divided into 4 groups with 3 replicates of 60 fish each, including control group, AFB1 group (60 μg/kg diet AFB1), 4-ME group (10 mg/kg diet 4-ME), and AFB1+4-ME group (60 μg/kg diet AFB1 + 10 mg/kg 4-ME diet), for a 60 d growth experiment. In vitro, we also set up 4 treatment groups in grass carp primary myoblast, including control group, AFB1 group (15 μmol/L AFB1), 4-ME group (0.5 μmol/L 4-ME) and AFB1+4-ME group (15 μmol/L AFB1+0.5 μmol/L 4-ME). The results showed that dietary AFB1 decreased growth performance of grass carp, damaged the ultrastructure and induced oxidative damage in grass carp muscle, and significantly decreased the mRNA and protein expression levels of myogenin (MyoG), myogenic differentiation (MyoD), myosin heavy chain (MYHC), as well as the protein expression levels of laminin β1, fibronectin and collagen Ⅰ (P < 0.05), significantly activated the protein expression levels of urokinase-type plasminogen activator (uPA), matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9) and phosphorylate-38mitogen-activated protein kinase (p38 MAPK) both in grass carp muscle and grass carp primary myoblast (P < 0.05). Supplementation of AFB1 with 4-ME significantly improved the growth performance inhibition and alleviated the muscle fiber development inhibition and extracellular matrix (ECM) degradation in grass carp induced by AFB1. The present results revealed that supplementation of AFB1 contaminated feed with 4-ME reduced the inhibition of growth and muscle development by alleviating AFB1-induced ECM degradation in grass carp, which might be related to the p38 MAPK/uPA/MMP/ECM pathway. The results implied that 4-ME could be used as a valuable mycotoxin scavenger in animal feed.

Metformin improves insulin resistance, liver healthy and abnormal hepatic glucolipid metabolism via IR/PI3K/AKT pathway in Ctenopharyngodon idella fed a high-carbohydrate diet

The effects and underlying mechanisms of metformin which can improve glucose homeostasis of fish have rarely been explored. This experiment aimed to explore the influence of metformin on growth performance, body composition, liver health, hepatic glucolipid metabolic capacity and IR/PI3K/AKT pathway in grass carp (Ctenopharyngodon idella) fed high-carbohydrate diets. A normal diet (Control) and high carbohydrate diets with metformin supplementation (0.00 %, 0.20 %, 0.40 %, 0.60 % and 0.80 %) were configured. Six groups of healthy fish were fed with the experimental diet for eight weeks. The results showed that the growth performance of grass carp was impaired in high carbohydrate diet. Impairment of IR/PI3K/AKT signalling pathway reduced insulin sensitivity, while hepatic oxidative stress damage and decreased immunity affected liver metabolic function. The glycolysis and lipolysis decrease while the gluconeogenesis and fat synthesis increase, which triggers hyperglycaemia and lipid deposition in the body. Metformin supplementation restored the growth performance of grass carp. Metformin improved IR/PI3K/AKT pathway signalling and alleviated insulin resistance, while liver antioxidant capacity and immunity were enhanced resulting in the restoration of liver health. The elevation of glycolysis and lipolysis maintains glycaemic homeostasis and reduces lipid deposition, respectively. These results suggest that metformin supplementation restores liver health and activates the IR/PI3K/AKT signalling pathway, ameliorating insulin resistance and glucose-lipid metabolism disorders caused by a high-carbohydrate diet. As judged by HOMA-IR, the optimum supplementation level of metformin in grass carp (C. idella) fed a high-carbohydrate diet is 0.67 %.

Impact of cadmium and diclofenac exposure on biochemical responses, transcriptome, gut microflora, and growth performance in grass carp (Ctenopharyngodonidella)

In recent years, the concentrations of cadmium (Cd) and diclofenac (DCF) in water have frequently exceeded the standard; however, the toxic effects of these two pollutants on grass carp under single and combined exposure are unknown. In this study, the concentrations of pollutants in different tissues were detected, and the toxicities of the two pollutants to grass carp under different exposure conditions were compared based on growth traits, biochemical responses, gut microbiome, and transcriptomes. Based on these findings, the brain showed the lowest levels of Cd and DCF accumulation. Oxidative stress and pathological damage were observed in the brain and intestines. Changes in the structure and abundance of the gut microflora affect the synthesis of neurotransmitters, such as GABA and steroids. Differentially expressed genes in the brain were enriched in circadian rhythm functions. The expression of PER, CLOCK,1L-1β, 1L-17, and other genes are related to the abundance of Akkermansia, which indicates that the disorder of gut microflora will affect the normal circadian rhythm of the brain. All indices in the recovery group showed an increasing trend. Overall, the toxicity of Cd and DCF showed antagonism, and a single exposure had a stronger effect on gut microorganisms and circadian rhythm, which provided a scientific basis for exploring the comprehensive effects of different pollutants.

Unveiling the emerging role of curcumin to alleviate ochratoxin A-induced muscle toxicity in grass carp (Ctenopharyngodon idella): in vitro and in vivo studies

BackgroundOchratoxin 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.MethodsA 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.ResultsFirstly, 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.ConclusionsIn 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

Integrated multiple-omics reveals the regulatory mechanism underlying the effects of homologous Bacillus tequilensis (GCB-3) on growth performance of grass carp (Ctenopharyngodon idellus)

The purpose of this study was to investigate the regulatory mechanism of Bacillus tequilensis (GCB-3) in improving the growth performance of grass carp by microbiome and targeted metabolomics analysis. Fish were fed with different amounts of GCB-3 including B0 (0 CFU/g), B6 (1×106 CFU/g), B7 (1×107 CFU/g), B8 (1×108 CFU/g), and B9 (1×109 CFU/g) for 8 weeks. The results indicate that with the increase of dietary GCB-3 concentration, grass carp showed a significant linear trend in growth performance, and appetite factors showed a significant linear and quadratic trend, the growth performance and appetite-promoting factors in the B8 group reach their maximum value in the B8 group. Microbiome analysis found that Proteobacteria and Actinobacteria were the most abundant phylum in the gut microbiota of grass carp. The functional potential predicted that GCB-3 affected the synthesis and degradation of carbohydrates, amino acids, fatty acids and lipids. It found that GCB-3 also affected the tricarboxylic acid (TCA) cycle VII (acetate-producers) pathway. The results of targeted metabolomics showed a significant linear and quadratic increase in intestinal acetate with GCB-3 concentration and a maximum in the B8 group. The results of the correlation analysis showed a significant positive correlation between Actinobacteria abundance and acetic acid content, and also between TCA cycle VII (acetate-producers) pathway abundance and Actinobacteria abundance and acetic acid content. In B8 group, grass carp showed a faster regulation speed of blood glucose levels after glucose injection, and the GLP-1 content remained stable. The activities of glycolytic enzymes, lipolytic enzymes, protein metabolism enzymes, and their related mRNA expression levels in grass carp showed a linear or quadratic increasing trend. However, the expression levels of gluconeogenic enzymes and fatty acid synthesis enzyme related mRNA showed an opposite trend. In summary, the addition of 1×108 CFU/g GCB-3 in grass carp feed can improve the abundance of dominant bacterial phyla in the intestine, especially Actinobacteria, increase the concentration of intestinal acetate, provide substrate for the TCA cycle VII (acetate-producers) pathway, thereby regulating the nutrient metabolism of grass carp and ultimately promoting growth.

Effects of sodium chloride in feed on growth performance of grass carp

Effects of sodium chloride in feed on growth performance of grass carp

DHA promotes healthy adipose tissue remodeling and carbohydrate utilization in grass carp (Ctenopharyngodon idellus) and largemouth bass (Micropterus salmoides)

Due to the wide usage of high-carbohydrate diets in aquaculture, improving the ability of fish to utilize high-carbohydrate diets is one of the important issues in aquaculture. Adipose tissue is an essential organ for storing energy and plays a vital role in glucose homeostasis. In this study, RNA sequencing reveals that docosahexaenoic acid (DHA) promoted the expression of the glucose metabolism related-genes in grass carp adipocytes, raising the hypothesis that DHA may attenuate the adverse effect of high-carbohydrate diets on fish via promoting glucose metabolism in adipose tissue. To verify this hypothesis, a total of 180 juvenile grass carp (14.24 ± 0.43 g) and a total of 180 largemouth bass (40.03 ± 0.12 g) were randomly distributed into 18 tanks (200 L), respectively, and fed with high-carbohydrate diets containing DHA. The results showed that high-carbohydrate diets promoted glycolysis and inhibited lipolysis and fatty acid β-oxidation, leading to the excessive accumulation of abdominal fat and adipose tissue inflammation. After feeding high-carbohydrate diets supplementation with DHA, glucose transporter type 4 (GLUT4) mediated-glucose uptake was increased in adipose tissue, resulting in significantly decreased blood glucose in grass carp and largemouth bass (P < 0.05). And then, the glucose was converted to triglyceride through the glucose-6-phosphate dehydrogenase (G6PD) mediated-pentose phosphate pathway, de novo synthesis of fatty acids and triglyceride (TG) synthesis. Subsequently, the resulting TG was broken down through lipolysis and fatty acid β-oxidation. These reprogrammed metabolic processes inhibited the excessive accumulation of abdominal fat. In addition, DHA attenuated inflammation in adipose tissue, and further reduced the levels of inflammatory cytokines in serum (P < 0.05), indicating that DHA promotes healthy adipose tissue remodeling. Ultimately, these benefits improved the growth performance of grass carp and largemouth bass fed with high-carbohydrate diets. Taken together, our study indicates that adipose tissue is an important target for improving the negative effects of high-carbohydrate diets, and DHA could promote healthy adipose tissue remodeling and improve carbohydrate utilization in fish by reprogramming the glucose and lipid metabolism in adipose tissues.

Assessment of black soldier fly (Hermetia illucens) larvae meal as a potential substitute for soybean meal on growth performance and flesh quality of grass carp Ctenopharyngodon idellus.

A 90-day feeding trial was conducted to assess the effects of black soldier fly larvae meal (BSFLM) as a replacement for soybean meal (SM) on growth performance and flesh quality of grass carp. A total of 420 grass carp (299.93±0.85g) were randomly divided into 7 groups (triplicate) and fed 7 diets with SM substitution of 0% (SM, control), 15% (BSFLM15), 30% (BSFLM30), 45% (BSFLM45), 60% (BSFLM60), 75% (BSFLM75) and 100% (BSFLM100) by BSFLM. The growth performance of grass carp in the BSFLM75 and BSFLM100 groups were significantly lower compared to other groups (P<0.05). The mid-gut villus height was the lowest in the BSFLM100 group (P<0.05). Muscle nutritional value was improved due to increased DHA (docosahexaenoic acid), EPA (eicosapentaenoic acid), total HUFA (highly unsaturated fatty acids) and glycine levels, and reached the optimum in the BSFLM100 group (P<0.05). According to the results of principal component analysis and weight analysis of muscle texture and body color, all the BSFLM diets except BSFLM15 could improve muscle texture and body color and reached the optimum level in the BSFLM100 group. Muscle drip loss and hypoxanthine content were the lowest and muscle antioxidant capacity was the highest in the BSFLM75 group, and water- and salt-soluble protein contents reached the optimum level in the BSFLM60 group (P<0.05). Dietary BSFLM significantly reduced muscle fiber area and diameter, and increased muscle fiber density and the proportion of small fiber (diameter <20μm)(P<0.05). Additionally, sarcomere lengths in the BSFLM75 and BSFLM100 groups were significantly higher than that in the SM group (P<0.05). The mRNA relative expression levels of MyoD, Myf5, MyHC and FGF6b were remarkably up-regulated at an appropriate dietary BSFLM level (P<0.05). In conclusion, BSFLM could replace up to 60% SM without an adverse effect on growth performance and improve the flesh quality of grass carp. The optimum levels of dietary BSFLM were 71.0 and 69.1g/kg diet based on the final body weight and feed conversion ratio. The flesh quality was optimal when dietary SM was completely replaced with BSFLM (227g/kg diet).

Effects of Replacing Soybean Meal Protein with Chlorella vulgaris Powder on the Growth and Intestinal Health of Grass Carp (Ctenopharyngodon idella).

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

Enhancing Growth Performance of Grass Carp (Ctenopharyngodon idella) and Tilapia (Oreochromis niloticus) with German Grass (Holcus mollis) and Vermicompost

In the present study, we evaluated the growth performance of grass carp (Ctenopharyngodon idella) and tilapia (Oreochromis niloticus) feeding German grass (Holcus mollis) produced organically using vermicompost. There were three treatments in the experiment, only German grass (T1), German grass + vermicompost @ 8,000 kg ha-1 year-1 (T2) and German grass + vermicompost @ 16,000 kg ha-1 year-1 (T3). In treatment T2 and T3, 25 % vermicompost was applied prior to 15 days ahead of fish stocking. The fish was stocked @ 10,000 grass carps and 15,000 tilapia ha-1, respectively. Water quality parameter such as temperature, dissolved oxygen, pH, nitrite, nitrate, and phosphate were varied among the treatments. 29 phytoplankton and 9 zooplankton genera observed in the three treatments with a significant abundance (p &lt; 0.05) in vermicompost treated ponds. According to a gut content study, tilapia primarily fed zooplankton and phytoplankton, whereas grass carp pre-dominantly consumed German grass and phytoplankton. The gross production was significantly higher in treatment T3 (2.94 Ton ha-1) followed by T2 (2.78 Ton ha-1) and T1 (2.57 Ton ha-1) 77 days-1. The research disclosed that the vermicompost application at 16,000 kg/ha/year with German grass was better option of producing organic grass carp and tilapia.

The beneficial effects of exogenous protease K originated from Parengyodontium album on growth performance of grass carp (Ctenopharyngodon idella) in relation to the enhanced intestinal digestion and absorption capacities

The study was primarily designed to analyze the effect of exogenous protease K on growth performance, amino acid metabolism, digestion and absorption capacities, expression of amino acid transporters related genes and proteins in intestine of sub-adult grass carp (Ctenopharyngodon idella). Six experimental diets with protease K (0, 3000, 6000, 9000, 12,000 and 15,000 U/kg) were fed to 450 grass carp (619.51 ± 0.54 g) for 60 days. The results indicated that the highest value of final body weight, percent weight gain (PWG), specific growth rate, protein efficiency ratio, activity of hepatopancreas glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase, and the lowest concentration of plasma ammonia were observed in groups with protease K of 6000 and 9000 U/kg. Meanwhile, the groups with 6000 and 9000 U/kg protease K exhibited the highest activities of digestive and brush border membrane enzymes in the three intestinal segments, as well as the highest value of intestinal somatic index and intestinal length index. The highest concentration of free amino acid in the serum and the lowest in intestine were observed in groups with supplementation of protease K 6000 and 9000 U/kg, which might be related to the up-regulated mRNA level and protein expression of intestinal amino acid transporters (SLC1A5, SLC7A6, SLC1A3 et al) in these groups. Furthermore, optimal levels of protease K up-regulated the mRNA levels of target of rapamycin (TOR), S6 kinase 1 (S6K1), and protein expression of TOR and phosphorylation TORSer2448, but reduced the mRNA level of 4E binding protein 1 (4EBP1). In summary, optimal levels of exogenous protease K was found to be conducive to facilitate the improvement of growth performance probably via enhancing digestion and absorption capacity, and utilization of amino acid in sub-adult grass carp. In addition, using quadratic regression analysis of PWG and alkaline phosphatase in the midgut, the optimum addition of protease K for the sub-adult grass carp were noted to be 7380.82 and 7406.44 U/kg, respectively.

Dietary effects of aucubin on growth and flesh quality of grass carp (Ctenopharyngodon idellus) based on metabolomics.

This aim of this study was to investigate the effects of dietary aucubin on the growth, flesh quality, and metabolomics of grass carp (Ctenopharyngodon idella). Five diets were designed with the aucubin inclusion of 0 (control diet), 0.2, 0.4, 0.6, and 0.8 g/kg (Auc-0.2, Auc-0.4, Auc-0.6, Auc-0.8) and were fed to grass carp with an initial body weight of 17.0 ± 0.2 g for 60 d. The results indicated that dietary aucubin did not significantly affect the growth performance of grass carp (P > 0.05). Compared to the control, dietary supplementation with 0.2 to 0.8 g/kg aucubin increased flesh hardness, chewiness, the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and the contents of total free amino acids (TFAA) and n-3 polyunsaturated fatty acids (n-3 PUFA) (P < 0.05). The contents of malondialdehyde (MDA) and lactic acid (LD) in the flesh were significantly decreased by the addition of 0.4 to 0.6 g/kg aucubin and by the addition of 0.6 to 0.8 g/kg aucubin (P < 0.05), respectively, while the content of delicious amino acids (DAA) was significantly enhanced by the addition of 0.4 to 0.8 g/kg aucubin (P < 0.05). Moreover, the contents of collagen and C22:6n3 (DHA) in the flesh of the Auc-0.8 group were significantly higher than those of the control (P < 0.05). In the metabolomics profiling of flesh, 133 and 135 named differential metabolites were identified in the Auc-0.4 and Auc-0.8 groups, respectively, compared to the control, and these metabolites were found to be involved in the second-grade pathways of "lipid metabolism" and "amino acid metabolism". Regarding gene expression, the mRNA levels of CuZn-SOD, CAT, COL1A1, COL1A2, Smad4, and FAS in flesh were upregulated in the Auc-0.4 and Auc-0.8 groups, and the expression levels of GPx, Nrf2, and TGF-β1 mRNA were also upregulated in the Auc-0.8 group (P < 0.05). In summary, dietary aucubin did not promote growth, but improved the flesh quality of grass carp, which might be associated with the TGF-β/Smad and Nrf2 pathways. The recommended supplementation level of aucubin in the diet of grass carp was 0.6 to 0.8 g/kg.

Comparative effects of dietary soybean oil and fish oil on the growth performance, fatty acid composition and lipid metabolic signaling of grass carp, Ctenopharyngodon idella

Lipid was an essential constituent of aquatic feeds, among which fish oil (FO) was the most excellent lipid source for its nutritive values. However, high price and limited production restricted its application, thus leading to the consideration of developing other alternative lipid sources, and soybean oil (SO) instead of FO was applied as the main lipid source in the commercial feed of grass carp. In the present study, two typical lipids sources FO and SO were used to prepare grass carp feed, and their comparative effects on the growth performance, nutrient composition and metabolic signaling were investigated. The growth performance of two groups exhibited no significant difference, while crude lipid was much higher in the muscle of SO group. Additionally, muscle fatty acid composition of both groups were highly correlated with that of diets, and the proportion of muscle n-3 polyunsaturated fatty acids was notably higher in the FO group, especially that of C20:5n-3 (EPA) and C22:6n-3 (DHA). Comparative digital gene expression profiles (DGE) was conducted and 1261 differentially expressed genes (DEGs) had been identified, then gene ontology (GO) enrichment analysis revealed the enriched functional subterms were primarily focused on cellular metabolic processes and regulation. KEGG pathway analysis elucidated the main metabolism related pathways, and DEGs involved in fatty acid elongation, fatty acid metabolism, and glycerolipid metabolism pathways were listed, including elongation of very long chain fatty acids protein 7 (el7), lysophospholipid acyltransferase 4 (lpcat4), long-chain acyl-CoA synthetase (acs), phosphatidate phosphatase LPIN (lpin), cathepsin L, and glucose-6-phosphate isomerase (gpi) et al. In conclusion, the nutritional composition rather than growth performance of grass carp was affected by different lipid sources, and the underlying regulatory signaling was predicted, which would provide theoretical basis for fish diet formulation.

Growth performance, intestinal microbiota and immune response of grass carp fed isonitrogenous and isoenergetic diets containing faba bean extracts

Functionally active components of faba bean (Vicia faba, FB) are known to improve the muscle texture and growth performance of grass carp (Ctenopharyngodon idellus), but this has not yet been proven by feeding trials using isonitrogenous and isoenergetic diets. Here, we formulated isonitrogenous and isoenergetic diets containing four types of FB extracts and examined their effects on the weight gain, textural quality, intestinal microbiota, metabolic enzymes and immune response of grass carp by a 100-day feeding trial. An isonitrogenous and isoenergetic diet with no FB extracts (control) and whole FB were also used. Compared to the control, the FB water extract diet increased weight gain, muscle hardness and chewiness, intestinal microbiota diversity, the activity of metabolic enzymes including lipase (LP), glucose-6-phosphatase (G-6-P), acetyl-CoA and succinate dehydrogenase (SDH) (P < 0.05). The FB alcohol extract diet also increased weight gain, intestinal microbiota diversity, but the total cholesterol (TC) and triglycerides (TG) contents were also increased (P < 0.05). The FB protein extract and FB residues diets had negative and no effects on weight gain, respectively, and caused intestinal microbiota disorder. FB water and alcohol extracts enhanced intestinal amino acids metabolism, whereas FB water extract and residues enhanced intestinal carbohydrate metabolism. These results further extend previous findings that FB water and alcohol extracts contain most functionally active components of FB, opening up the possibility that these extracts can be used as functional feed additives for freshwater fish.

Influences of dietary Eucommia ulmoides extract on growth, flesh quality, antioxidant capacity and collagen-related genes expression in grass carp (Ctenopharyngodon idellus)

The study investigated the effects of dietary Eucommia ulmoides extracts on growth, flesh quality and collagen-related genes expression of grass carp (Ctenopharyngodon idella). Eucommia ulmoides bark extract (EBE) and Eucommia ulmoides leaf extract (ELE) were individually supplemented into basal diet (control) at an inclusion of 4 g/kg, and then the three diets were fed to grass carp (59.7 ± 0.3 g) for 60 days. The results indicated that dietary ELE significantly increased weight gain (+4.22 %), and decreased feed conversion ratio (-4.05 %) (P < 0.05), while EBE did not significantly affect the growth performance of grass carp. Compared to the control, dietary ELE significantly increased apparent digestibility coefficient of dry matter, crude protein and intestinal digestive enzyme activity (P < 0.05), and the contents of calcium, total collagen, heat-insoluble collagen and free amino acids level (including delicious amino acids) in flesh were also significantly increased (P < 0.05). In both extracts groups, the flesh centrifugal loss, steaming loss, drip loss24h, protein carbonyl and malondialdehyde were significantly lower, and superoxide dismutase and glutathione peroxidase activities were significantly higher than the control (P < 0.05). No significant differences in the amount of saturated, monounsaturated and polyunsaturated fatty acids in flesh were found among the three groups, but docosapentaenoic acid (DPA), docosahexaenic acid (DHA), n-3 polyunsaturated fatty acids and n-3/n-6 ratio in flesh were significantly increased by dietary EBE and ELE (P < 0.05). In collagen-related genes expression, the ELE supplementation significantly promoted the expression of collagen type I (COL1A1, COL1A2), proline hydroxylase, lysine oxidasein in muscle, while the expression of matrix metalloproteinase-2 and matrix metalloproteinase-9 was significantly decreased (P < 0.05). In conclusion, dietary ELE improved the growth, muscle antioxidant capacity and flesh quality of grass carp.

Alginate oligosaccharide improves fat metabolism and antioxidant capacity in the liver of grass carp (Ctenopharyngodon idellus)

The aim of the current study was to investigate the potentially beneficial effects of alginate oligosaccharide (AOS) on the modulation of growth, fatty acid metabolism, and antioxidant capacity in grass carp (Ctenopharyngodon idellus), and the fundamental mechanisms involved. AOS enhanced the growth performance of grass carp in a dose-dependent manner. Histopathological analysis revealed that AOS had a protective effect in the liver and head kidney when changed by Aeromonas hydrophila, and that it could also reduce fat accumulation in the liver. In order to identify the mechanisms of action of AOS, transcriptomic profiling was performed in control fish fed a normal diet, and groups of fish fed 5 g/kg, 10 g/kg, or 20 g/kg of AOS. A total of 21,836 known genes and 818 novel genes were obtained, and higher dosages of AOS were associated with more differentially expressed genes (DEGs). Kyoto Encyclopedia of Genes and Genomes pathway analysis indicated that all three dosages of AOS activated fatty metabolism-related pathways. To further elucidate the transcriptomic data, expression levels of the six fatty metabolism-related genes Apoa 1, Apoa 4, Agpat 1, DGAT, MGAT, and ABCG 5 were determined. All six genes were activated by AOS. Antioxidant capacities were detected after 6 weeks on a diet containing AOS, including superoxide dismutase, glutathione peroxidase, and catalase. These results suggested that dietary AOS improves the liver's antioxidant capacity. Lastly, lipase, triglyceride, and malondialdehyde data showed that AOS could enhance lipase activity and reduce fat accumulation in the liver, lower residual malondialdehyde in the liver, and reduce apoptosis in the liver. The present study suggests that AOS can enhance growth performance, promote fat metabolism, and improve antioxidant capacity in the liver in grass carp. AOS can be beneficial as a dietary supplement in grass carp, particularly within the aquaculture industry.

Benefits of thymol supplementation on performance, the hepatic antioxidant system, and energetic metabolism in grass carp.

Thymol is an herbal food additive used to improve animal performance. Thymol acts via its potential to enhance productive and reproductive performance, and by improving bioavailability of nutrients in fish. Nevertheless, the exact mechanisms associated with these phenomena remain poorly understood, although recent evidence has suggested the involvement of the phosphotransfer network and antioxidant status. Therefore, the aim of this study was to determine whether the improvement of the antioxidant/oxidant status and the phosphoryl transfer network may be involved in enhanced growth performance in grass carp (Ctenopharyngodon idella) fed with various levels of thymol (100, 200, and 300 mg/kg feed). Thymol-supplementation (100 mg/kg feed) produced higher body weight and weight gain for 60-day post-feeding compared to the control group. Specific growth rate was higher; while feed conversion ratio was lower in fish that consumed 100 mg of thymol/kg compared to other groups. Hepatic lactate dehydrogenase activity and lipid peroxidation levels were lower in the thymol-supplemented group (100 mg/kg feed) than in the control group, while reactive oxygen species were lower in all supplemented groups than in the control group. Hepatic superoxide dismutase (300 mg/kg feed) and glutathione peroxidase (100, 200, and 300 mg/kg feed) activities, as well as antioxidant capacity against peroxyl radicals (100 mg/kg feed) were higher in these groups than in the control group. Based on these data, we conclude that 100 mg thymol/kg dietary supplementation increased growth performance of fingerling grass carp. Finally, hepatic adenylate kinase activity was lower in the thymol supplemented group (100 mg/kg feed) than in the control group. Thymol supplementation (100 mg/kg feed) improved hepatic energy metabolism, while practically all tested concentrations of thymol enhanced hepatic antioxidant status, all of which may be pathways involved in increased growth performance in fingerling grass carp.

Effect of Different Protein Source Diets on Growth, Sensory Parameters and Flesh texture of On-Growing Grass Carp (Ctenopharyngodon idellus)

The introduction of plant protein (PP) sources in aquafeed is regarded as an economic and environmental-friendly strategy for aquaculture. Our objective was to investigate the effects of pure PP diets on the growth performance and to analyze their effects on flesh quality of grass carp (357.2±0.7g). The study was performed using and comparing a control fish meal diet and two PP diets. Fish meal (FM), soybean meal (SBM), and rapeseed meal (RM) were served as sole protein source of corresponding feeds, respectively. The results suggested that the PP diets significantly impaired the growth performance of grass carp. In regard to flesh quality, the SBM and RM diets decreased the muscle lipid content, n-3 series of PUFA, EPA, DHA, and n-3/n-6 ratio at the nutritional level. However, from the consumer’s perspective SBM significantly improved flesh firmness, and RM diets, and PP diets had no adverse effects on flesh flavor, amino acids composition, and sensory characteristics. Fish fed the RM diet displayed a higher water holding capacity (WHC) in the fillets than in the other groups. In summary, compared to the FM diet, both SBM and RM diets reduced fish growth and flesh lipid nutritive values, but improved the fillet firmness. Plant ingredient-rich diets do not have detrimental effects on muscle flavor because of the free amino acids composition and organoleptic attributes.

Dietary taurine can improve the hypoxia-tolerance but not the growth performance in juvenile grass carp Ctenopharyngodon idellus

This study was conducted to evaluate the effects of dietary taurine, as a feed additive, on the hypoxia-tolerance and growth performance of the juvenile grass carp Ctenopharyngodon idellus, one of the most important and intensively cultured freshwater fish, with the largest production in China. Graded levels of taurine (0, 0.5, 1, 1.5, 2 and 2.5 g kg(-1) dry diet) were fed to grass carp juveniles (mean weight: 5.26 ± 0.03 g) for 8 weeks. The survival time during acute hypoxia increased as dietary levels of taurine increased, with the highest dose of taurine resulting in the best acute hypoxia-tolerance. The erythrocyte osmotic fragility in grass carp was significantly improved when dietary taurine level was at least 1.5 g kg(-1) diet and can be improved much more when dietary taurine level was up to 2.5 g kg(-1) diet. A significant correlation between hemolysis rate of the erythrocyte osmotic fragility test and the survival time of acute hypoxia (r = -0.873, P = 0.023 < 0.05) strongly suggested that the biomembrane stabilization function of taurine may contribute to its role of enhancing acute hypoxia-tolerance in grass carp. Dietary taurine cannot improve growth performance of grass carp, but it can increase the value of mesenteric fat index, indicating that dietary taurine influences the lipid metabolism. This study provides valuable information to improve hypoxia-tolerance of grass carp.

Effect of probioticBacillus subtilisCh9 for grass carp,Ctenopharyngodon idella(Valenciennes, 1844), on growth performance, digestive enzyme activities and intestinal microflora

Summary In the present study, Bacillus subtilis Ch9 was evaluated as a probiotic in grass carp, Ctenopharyngodon idella (Valenciennes, 1844). For 56 days the grass carp (50 ± 2.5 g) were given a feed containing B. subtilis Ch9 in three concentrations: 1.0 × 109 (T1), 3.0 × 109 (T2) and 5.0 × 109 (T3) CFU kg−1 feed in triplicate treatments. The control group (T0) was given feed without B. subtilis Ch9 for the same period. Determined were the specific growth rate (SGR), feed conversion ratio (FCR), and digestive enzyme activities in the intestine and hepatopancreas as well as the intestinal microflora. After 56 days, fish receiving the diets supplemented with B. subtilis Ch9 showed significantly higher SGR and lower FCR (P 0.05) by the dietary treatments. From days 14 to 56 of the experiment, higher protease, amylase and lipase activities in the foregut, midgut hindgut and hepatopancreas were observed in T1, T2 and T3 (P 0.05), but the ratio of Bacillus was significantly higher (P < 0.05) than in control fish. The total anaerobic bacterial quantity, Bifidobacterium and Lactobacillus were significantly higher (P < 0.05) in fish fed B. subtilis Ch9 compared with fish fed control feed. In conclusion, an optimum dose of B. subtilis Ch9 could modulate intestinal microflora, induce digestive enzyme activity and potentially promote the digestion and absorption of nutrients, as well as improve the growth performance of grass carp significantly.