Blunt Snout Bream Megalobrama Amblycephala Research Articles

Evaluation Of Zinc-Bearing Palygorskite Effects on Growth Performance, Nutrient Retention, Meat Quality, and Zinc Accumulation in Blunt Snout Bream Megalobrama Amblycephala

AbstractZinc (Zn) is widely known as an essential trace element for fish and new ways to supply it to them are needed. Palygorskite (Pal) is a natural silicate clay mineral and the palygorskite structure contains nano-channels, which are filled with water and exchangeable ions. Zn-bearing palygorskites (Zn-Pal) prepared using ion exchange have attracted attention due to the durable antibacterial properties that limit pathogens and as a potential new Zn source for livestock. The present study was conducted to evaluate the effects of Zn-Pal supplementation on the growth performance, nutrient retention, meat quality, Zn accumulation, and intestinal Zn transporter protein gene expression in blunt snout bream Megalobrama amblycephala. The fish were fed a basal diet without an exogenous Zn source and the basal diet was supplemented with 125 mg/kg Zn as Zn sulfate (ZnSO4) or 35, 80, or 125 mg/kg Zn as Zn-Pal. Each diet was tested using three replicates for 7 weeks. The results showed that dietary Zn-Pal supplementation quadratically (P<0.05) increased growth performance, nutrient retention, total and Cu/Zn superoxide dismutase activity, Zn content in scales, and intestinal Zn transporter protein gene expression. The muscular cooking loss in blunt snout bream decreased with the optimum Zn-Pal Zn level of 35 mg/kg. Compared to the fish treated with ZnSO4, the fish supplemented with 35 mg/kg as Zn-Pal exhibited similar growth performance and nutrient retention (P>0.05), increased mRNA expression of the metal-response element-binding transcription factor-1 in the intestine (P<0.05), and decreased cooking loss of muscle (P<0.05).The results suggested that 35 mg/kg Zn supplementation as Zn-Pal could improve the growth performance and body composition, increase nutrient retention and tissue Zn concentrations, enhance the muscle water-holding capacity, and enhance antioxidant status in blunt snout bream. The Zn-Pal was more efficient and could be used as an alternative Zn source to ZnSO4 in the diet of blunt snout bream.

Lysine supplement benefits the growth performance, protein synthesis, and muscle development of Megalobrama amblycephala fed diets with fish meal replaced by rice protein concentrate.

This study aimed to investigate the effects of lysine supplement on the growth performance of blunt snout bream Megalobrama amblycephala fed diets with fish meal (FM) replaced by rice protein concentrate (RPC) with the potential mechanisms characterized. Fish were fed three diets, including the FM diet (containing FM), the RPC diet (FM replaced by RPC), and the MRPC diet (the RPC diet supplemented with lysine) for 8weeks. Weight gain, protein efficiency ratio, and nitrogen and energy utilization of fish fed the FM diet were all significantly higher than those of the RPC treatment, but they showed no statistical difference with those of the MRPC group. Fish fed the RPC diet showed shorter villi length of the distal intestine than that of the other treatments. No significance was found in whole-body composition and intestinal and hepatic cell proliferation among all the treatments. However, fish fed the RPC diet obtained relatively low transcriptions of growth hormone (GH), GH receptor, insulin-like growth factor-I (IGF-I), target of rapamycin (TOR), ribosomal protein S6 kinase 1, myoblast determination protein, myogenic factor 5, and myostatin a (MSTNa) but high levels of eukaryotic translation initiation factor 4E-binding protein 2 (4E-BP2) than those of the other groups. Furthermore, little difference was found in the transcriptions of 4E-BP2, myogenin, muscle-specific regulatory 4, and MSTNb in muscle. Overall, these results showed that dietary supplement of lysine benefits the growth performance of blunt snout bream fed FM-free diets through the mediation of the GH-IGF-I axis, TOR signaling pathway, myogenic regulatory factors, and MSTN.

Molecular Characterization of the RNA-Binding Protein Quaking-a in Megalobrama amblycephala: Response to High-Carbohydrate Feeding and Glucose/Insulin/Glucagon Treatment.

The RNA-binding protein quaking-a (Qkia) was cloned from the liver of blunt snout bream Megalobrama amblycephala through the rapid amplification of cDNA ends method, with its potential role in glucose metabolism investigated. The full-length cDNA of qkia covered 1,718 bp, with an open reading frame of 1,572 bp, which encodes 383 AA. Sequence alignment and phylogenetic analysis revealed a high degree of conservation (97–99%) among most fish and other higher vertebrates. The mRNA of qkia was detected in all examined organs/tissues. Then, the plasma glucose levels and tissue qkia expressions were determined in fish intraperitoneally injected with glucose [1.67 g per kg body weight (BW)], insulin (0.052 mg/kg BW), and glucagon (0.075 mg/kg BW) respectively, as well as in fish fed two dietary carbohydrate levels (31 and 41%) for 12 weeks. Glucose administration induced a remarkable increase of plasma glucose with the highest value being recorded at 1 h. Thereafter, it reduced to the basal value. After glucose administration, qkia expressions significantly decreased with the lowest value being recorded at 1 h in liver and muscle and 8 h in brain, respectively. Then they gradually returned to the basal value. The insulin injection induced a significant decrease of plasma glucose with the lowest value being recorded at 1 h, whereas the opposite was true after glucagon load (the highest value was gained at 4 h). Subsequently, glucose levels gradually returned to the basal value. After insulin administration, the qkia expressions significantly decreased with the lowest value being attained at 2 h in brain and muscle and 1 h in liver, respectively. However, glucagon significantly stimulated the expressions of qkia in tissues with the highest value being gained at 6 h. Moreover, high dietary carbohydrate levels remarkably increased plasma glucose levels, but down-regulated the transcriptions of qkia in tissues. These results indicated that the gene of blunt snout bream shared a high similarity with that of the other vertebrates. Glucose and insulin administration, as well as high-carbohydrate feeding, remarkably down-regulated its transcriptions in brain, muscle and liver, whereas the opposite was true after the glucagon load.

Divergence of Genes Encoding CITED1 and CITED2 in Blunt Snout Bream (Megalobrama amblycephala) and Their Transcriptional Responses to Hypoxia.

The proteins CITED belong to a family of non-DNA-binding transcriptional co-regulators involved in the regulation of various transcriptional responses. Previous studies suggest that members of CITED family may function in response to hypoxia in mammals. however, the molecular and functional information on CITED genes in aquaculture fish is unclear. Here, we characterized and examined the transcriptional patterns of CITED1 and CITED2 genes in the hypoxia-sensitive blunt snout bream (Megalobrama amblycephala). Blunt snout bream CITED1 and CITED2 genes shared a relatively low sequence identity of 45%. CITED1 and CITED2 mRNAs were widely transcribed in adult tissues. During embryogenesis, CITED1 mRNA was significantly transcribed at 4, 24, 28, 40, and 44 hpf, whereas CITED2 mRNA levels fluctuated from the zygote to 44 hpf larval stage. Whole-mount in situ hybridization demonstrated that CITED1 and CITED2 mRNAs were detected in the brain at 12 hpf, brain and gut at 24 hpf, and brain at 36 hpf. In addition, low expression of CITED1 mRNA was detected in the tailbud at 24 hpf. The results of acute hypoxia experiment showed that CITED1 and CITED2 mRNAs were markedly upregulated in the kidney and downregulated in the liver, brain, gill, and heart under hypoxia. Embryos in hypoxic conditions at different developmental stages showed a significant increase in mRNA levels of CITED1 and CITED2. These results provide a new insight into the divergence of CITED1 and CITED2 genes and their transcriptional responses to hypoxia.

Dietary Supplementation of Glycyrrhetinic Acid (GA) Promoting Lipid Lipolysis from Blunt Snout Bream Megalobrama amblycephala by TNF-α and LPL Expression

Glycyrrhetinic acid (GA), which is a main active principal constituent of liquorice, is extensively used as a non-nutrition sweetener or antiinflammatory in Chinese medicine. This study was carried out to evaluate the effects of different GA levels on growth, biometric parameters, plasma lipid metabolites, Tumor necrosis factor alpha (TNF-α) and Lipoprotein lipase (LPL) gene expression of Megalobrama amblycephala (average weight, 68.78 ±1.13 g). Three diets were formulated to contain various levels of GA (0, 30 and 300 mg/kg). Fish were randomly distributed into 12 cages and fed three times daily for 8 weeks. Dietary GA levels have little significant effect on weight gain and feed conversion ratio. Intraperitoneal fat ratio and viscera/body ratio decreased significantly as dietary GA levels increased, and hepatosomatic index tended to decrease as dietary GA levels increased. Plasma triglycerides, cholesterol, and non-esterified free fatty acid levels also decreased as dietary GA concentrations increased. Adipose tissue and liver TNF-α expression increased significantly with increasing dietary GA levels; whereas, LPL expression showed an opposite trend. Results of this study indicate that dietary supplementation of 300 mg/kg GA had a positive effect in promoting lipid lipolysis in Megalobrama amblycephala without having a negative effect on growth through the regulation of TNF-α and LPL expression.

Interactions between dietary carbohydrate and metformin: Implications on energy sensing, insulin signaling pathway, glycolipid metabolism and glucose tolerance in blunt snout bream Megalobrama amblycephala

A 12-week feeding trial was performed to evaluate the effects of metformin on growth performance, energy sensing, insulin signaling pathway, glycolipid metabolism and glucose tolerance of blunt snout bream fed high-carbohydrate diets. Fish were randomly fed four diets containing two dietary carbohydrate levels (30 and 43%) and two metformin levels (0 and 0.25%). High carbohydrate levels remarkably increased tissue glycogen and lipid contents, hepatic adenosine triphosphate (ATP) and adenosine monophosphate (AMP) contents and the ATP/AMP ratio, plasma levels of glucose, insulin, triglyceride, glycated serum protein (GSP), advanced glycation end products (AGES) and lactic acid, hepatic t-AMPK protein levels and the transcriptions of AMPKα1, AMPKα2, target of rapamycin (TOR), insulin receptor (IR), ribosomal protein S6 kinase-polypeptide 1 (S6K1), glucokinase (GK), pyruvate kinase (PK), glucose transporter 2 (GLUT 2), glycogen synthase (GS), acetyl-CoA carboxylase α (ACCα), fatty acid synthase (FAS) and sterol regulatory element-binding protein-1 (SREBP1), whereas the opposite was true for weight gain, relative feed intake (RFI), feed conversion ratio (FCR), pyruvate levels, p-AMPK level, p-AMPK/t-AMPK ratio and the transcriptions of insulin receptor substrate 1 (IRS1), phosphoenolpyruvate carboxykinase (PEPCK), glucose-6-phosphatase (G6Pase), fructose-1,6-biphosphatase (FBPase), carnitine palmitoyltransferase IA (CPT IA), peroxisome proliferator activated receptor α (PPARα) and acyl-CoA oxidase (ACO). In addition, metformin supplementation remarkably increased tissue glycogen contents, plasma lactic acid level, hepatic AMP content, t-AMPK and p-AMPK level, p-AMPK/t-AMPK ratio and the transcriptions of AMPKα1, AMPKα2, IR, IRS1, GK, PK, GLUT 2, GS, CPT IA, PPARα and ACO, while the opposite was true for the remaining indicators. Significant interactions between dietary carbohydrate and metformin were also observed in RFI, FCR, tissue glycogen and lipid contents, hepatic ATP/AMP ratio, plasma metabolites, the phosphorylation of AMPK and the transcriptions of TOR, IRS1, S6K1, PK, G6Pase, GLUT 2, GS, ACCα, FAS, SREBP1, CPT IA, PPARα and ACO. Furthermore, metformin improved the glucose tolerance of fish fed high-carbohydrate diets after glucose loading. Overall, our findings indicated that metformin should be benefits the intermediary metabolism of Megalobrama amblycephala fed high-carbohydrate diets through the enhancement of energy sensing, insulin sensitivity, glycolysis, glycogenesis and fatty acid oxidation coupled with the suppression of gluconeogenesis and lipogenesis.

Dietary carbohydrate levels and lipid sources modulate the growth performance, fatty acid profiles and intermediary metabolism of blunt snout bream Megalobrama amblycephala in an interactive pattern

This study aimed to investigate the interactive effects of dietary carbohydrate levels and lipid sources on growth performance, tissue fatty acid (FA) profiles and intermediary metabolism of Megalobrama amblycephala. Fish (average weight: 37.98±0.07g) were randomly fed one of eight diets containing two carbohydrate levels (30% and 43%) and four lipid sources (fish oil, FO; soybean oil, SO; palm oil, PaO; and mixed oil (FO: SO: PaO=1:1:1), MO) for 11weeks. Little difference (P>0.05) was observed in growth performance and whole-body composition (except for lipid). However, energy retention, body lipid content, tissue lipid and glycogen contents and plasma metabolites concentrations all increased significantly (P<0.05) with increasing carbohydrate levels. Additionally, nitrogen retention (NRE), body and tissue (liver and muscle) lipid content, liver and intraperitoneal fat glycogen contents and plasma metabolites concentrations were all significantly affected (P<0.05) by lipid sources. Hepatic and muscle monounsaturated fatty acids (MUFA) contents increased significantly (P<0.05) with increasing carbohydrate levels, whereas the opposite was true for eicosapentaenoic acid, docosahexaenoic acid, polyunsaturated fatty acids (PUFA) and n−3 long-chain PUFA (n−3 LC-PUFA) contents (P<0.05). In terms of lipid sources, fish fed FO presented a high proportion of n−3 LC-PUFA, EPA and DHA (P<0.05); while fish received SO and PaO obtained a high proportion of n−6 LC-PUFA and MUFA, respectively (P<0.05). Liver glucokinase, glycogen synthase, fatty acid synthetase (FAS), acetyl-CoA carboxylase α, delta-6 fatty acyl desaturase and peroxisome proliferator-activated receptor γ (PPARγ) as well as muscle pyruvate kinase (PK) expressions all increased significantly (P<0.05) with increasing carbohydrate levels, whereas the opposite was true for the transcriptions of enzymes involved in β-oxidation and gluconeogenesis. Hepatic FAS and muscle phosphoenolpyruvate carboxykinase (PEPCK) transcriptions were significantly affected (P<0.05) by lipid sources. Furthermore, an interaction between dietary carbohydrate levels and lipid sources was also observed in feed intake, NRE, body/tissue lipid and glycogen contents, plasma lipids, tissue MUFA, PUFA, n−3 LC-PUFA and n−6 LC-PUFA contents as well as the transcriptions of enzymes involved in glucose and lipid metabolism (P<0.05). Overall, these findings suggested that blunt snout bream can efficiently utilize various lipid sources at different carbohydrate levels. Dietary carbohydrate levels and lipid sources as well as their interaction significantly affected nutrient retention, tissue lipid and glycogen contents, plasma metabolites, tissue FA profiles and the intermediary metabolism, but not growth and feed efficiency.

Dietary arginine affects the insulin signaling pathway, glucose metabolism and lipogenesis in juvenile blunt snout bream Megalobrama amblycephala

This study evaluated the mechanisms governing insulin resistance, glucose metabolism and lipogenesis in juvenile fish fed with graded levels of dietary arginine. The results showed that, compared with the control group (0.87%), 2.31% dietary arginine level resulted in the upregulation of the relative gene expression of IRS-1, PI3K and Akt in the insulin signaling pathway, while 2.70% dietary arginine level led to inhibition of these genes. 1.62% dietary arginine level upregulated glycolysis by increasing GK mRNA level; 2.70% dietary arginine level upregulated gluconeogenesis and resulted in high plasma glucose content by increasing PEPCK and G6P mRNA level. Furthermore, 2.70% dietary arginine level significantly lowered GLUT2 and increased PK mRNA levels. 1.62% dietary arginine level significantly upregulated ACC, FAS and G6PDH mRNA levels in the fat synthesis pathway and resulted in high plasma TG content. These results indicate that 1.62% dietary arginine level improves glycolysis and fatty acid synthesis in juvenile blunt snout bream. However, 2.70% dietary arginine level results in high plasma glucose, which could lead to negative feedback of insulin resistance, including inhibition of IRS-1 mRNA levels and activation of gluconeogenesis-related gene expression. This mechanism seems to be different from mammals at the molecular level.

Estimation of genetic parameters for resistance to Aeromonas hydrophila in blunt snout bream (Megalobrama amblycephala)

Bacterial hemorrhagic disease caused by Aeromonas hydrophila is one of the harmful bacterial diseases for aquaculture. The aim of this study was to evaluate the genetic parameters for resistance to A. hydrophila in blunt snout bream Megalobrama amblycephala. A total of 834 individuals at one-year old from 27 families were experimentally infected with A. hydrophila. During five days duration of the challenge test, deaths peaked at the second day after infection and average mortality over the whole population was 83.93% (family averages ranging from 97.22% to 22.22%). The heritability of A. hydrophila resistance (dead or alive at peak mortality, day 2, under an animal model) under cross-sectional linear (LIN), cross-sectional threshold models (THRp and THRI) was quite different, ranging from zero to 0.33. Compared with the phenotypic correlation coefficient, the genetic correlation coefficient between disease resistance and growth related traits, was relatively high for all genetic parameters. Genetic correlations of resistance to A. hydrophila with body height (0.63), body length (0.65) and body weight (0.60) were significant (P < 0.01) and positive; however, correlations of resistance with sex was non-significant (P >0.05). These results provide the first report for heritability of resistance to A. hydrophila in M. amblycephala, and correlation with three growth related traits (body height, body length and body weight) could efficiently facilitate indirect selection of M. amblycephala with high A. hydrophila resistance.

The draft genome of blunt snout bream (Megalobrama amblycephala) reveals the development of intermuscular bone and adaptation to herbivorous diet.

The blunt snout bream Megalobrama amblycephala is the economically most important cyprinid fish species. As an herbivore, it can be grown by eco-friendly and resource-conserving aquaculture. However, the large number of intermuscular bones in the trunk musculature is adverse to fish meat processing and consumption. As a first towards optimizing this aquatic livestock, we present a 1.116-Gb draft genome of M. amblycephala, with 779.54 Mb anchored on 24 linkage groups. Integrating spatiotemporal transcriptome analyses, we show that intermuscular bone is formed in the more basal teleosts by intramembranous ossification and may be involved in muscle contractibility and coordinating cellular events. Comparative analysis revealed that olfactory receptor genes, especially of the beta type, underwent an extensive expansion in herbivorous cyprinids, whereas the gene for the umami receptor T1R1 was specifically lost in M. amblycephala. The composition of gut microflora, which contributes to the herbivorous adaptation of M. amblycephala, was found to be similar to that of other herbivores. As a valuable resource for the improvement of M. amblycephala livestock, the draft genome sequence offers new insights into the development of intermuscular bone and herbivorous adaptation.

Effects of dietary vitamin E supplementation on growth performance, fatty acid composition, lipid peroxidation and peroxisome proliferator-activated receptors (PPAR) expressions in juvenile blunt snout bream Megalobrama amblycephala.

A 9-week feeding experiment was conducted to evaluate the effects of dietary vitamin E (VE) supplementation on growth performance, liver fatty acid composition, lipid peroxidation and peroxisome proliferator-activated receptors (PPAR) genes expressions in blunt snout bream juveniles. Fish (average initial weight: 0.59g) were fed diet supplemented with 0, 50, 100, 300 and 500mg α-tocopherol acetate/kg in triplicates, which were found to, respectively, contain 11.2, 56.3, 114.6, 306.5 and 588.4mg α-tocopherol/kg diet. Results showed that final weight, body weight gain and specific growth rate significantly increased with increasing dietary VE supplemented level from 11.2 to 56.3mg/kg. When the broken-line model was employed to estimate the adequate requirement of vitamin E based on body weight gain, the optimal level was 55.5mg/kg in diet. Hepatosomatic index value significantly decreased with incremental dietary VE levels. However, liver VE concentration showed a direct relationship with the dietary VE level. The percentages of 20:5n-3, 22:6n-3 and total n-3 long chain polyunsaturated fatty acids in liver increased with increasing dietary VE supplementation. Meanwhile, the expressions of PPAR-α, PPAR-β and PPAR-γ in liver were down-regulated by supplementation of dietary VE level from 56.3 to 588.4mg/kg. In conclusion, supplementation of more than 55.5mg/kg vitamin E may improve growth and increase n-3 LC-PUFA content in blunt snout bream, which is beneficial to human consumer.

Molecular characterization of fructose-1,6-bisphosphatase 1b in blunt snout bream Megalobrama amblycephala and the transcriptional response to glucose loading after the adaptation to high-carbohydrate diets.

This study aimed to characterize the full-length complementary DNA (cDNA) of fructose-1,6-bisphosphatase 1b (FBP1b) from fish Megalobrama amblycephala, and investigate its transcriptional response to glucose administration after the adaptation to high-carbohydrate diets. The cDNA obtained covered 1435bp with an open reading frame of 1014bp. Sequence alignment and phylogenetic analysis revealed a high degree of conservation (76-96%) among most fish and other vertebrates, retaining one N-linked glycosylation site, one N-terminal acetylation site, 13 phosphorylation sites, one fructose-1,6-bisphosphatase (FBPase) active site, five metal-binding sites, four substrate-binding sites, and several AMP-binding sites. The highest messenger RNA (mRNA) level of FBP1b was observed in liver followed by intestine, whereas relatively low values were detected in heart, gill, and eye. Then, the mRNA levels of FBP1b and the FBPase activity were both determined in the liver of fish injected intraperitoneally with 1.67g glucose per kilogram body weight after being fed two dietary carbohydrate levels (30 and 42%) for 11weeks. After the glucose load, the mRNA levels of FBP1b in both treatments decreased significantly to the basal value at 8h and showed a slight increase afterward. However, the enzymatic activity showed no statistical difference during the first 4h, but increased remarkably with further increasing times. In addition, both the mRNA levels and activities decreased significantly with increasing dietary carbohydrate levels. The results indicated that the FBP1b of M. amblycephala shared a high similarity with that of the other vertebrates. Its mRNA expression in liver was downregulated remarkably by a glucose administration, as also held true after the long-term adaptation of a carbohydrate-rich diet.

Acinetobacter johnsonii: an Emerging Pathogen for Cultured Blunt Snout Bream Megalobrama amblycephala

Bacteriosis has caused significant economic losses in farmed blunt snout bream Megalobrama amblycephala. Only scarce information is available on Acinetobacter johnsonii as a possible causal agent in M. amblycephala. In this study, a virulent strain temporarily named BY3, was isolated from diseased bream, identified phenotypically and molecularly as A. johnsonii. Phylogenetic trees of 16S rRNA and gyrB gene sequences were constructed to examine the taxonomic position of isolate BY3 and compare it to other known isolates. When screened against a range of common veterinary antibiotics, isolate BY3 has not shown resistance to florfenicol, neomycin, and sulfisoxazole antibiotics in aquaculture. To the best of our knowledge, this is the first report of A. johnsonii infection in farmed blunt snout bream.

Acinetobacter johnsonii: an Emerging Pathogen for Cultured Blunt Snout Bream Megalobrama amblycephala

Bacteriosis has caused significant economic losses in farmed blunt snout bream Megalobrama amblycephala. Only scarce information is available on Acinetobacter johnsonii as a possible causal agent in M. amblycephala. In this study, a virulent strain temporarily named BY3, was isolated from diseased bream, identified phenotypically and molecularly as A. johnsonii. Phylogenetic trees of 16S rRNA and gyrB gene sequences were constructed to examine the taxonomic position of isolate BY3 and compare it to other known isolates. When screened against a range of common veterinary antibiotics, isolate BY3 has not shown resistance to florfenicol, neomycin, and sulfisoxazole antibiotics in aquaculture. To the best of our knowledge, this is the first report of A. johnsonii infection in farmed blunt snout bream.

Long-term administration of benfotiamine benefits the glucose homeostasis of juvenile blunt snout bream Megalobrama amblycephala fed a high-carbohydrate diet

This study aimed to investigate the effects of benfotiamine on growth performance, glucose homeostasis and intermediary glucose metabolism of blunt snout bream (Megalobrama amblycephala). A total of 240 fish (average body weight: 24.24±0.05g) were randomly distributed into 12 tanks and fed three diets (control, diet with 30% carbohydrate; HC, diet with 43% carbohydrate; HCB, HC diet supplemented with 2.85mg/kg benfotiamine) for 12weeks. The results indicated that fish fed the HCB diet had a lower specific growth rate and feed conversion ratio compared to those fed the control and HC diets, whereas protein efficiency ratio, nitrogen retention efficiency and energy retention efficiency showed an opposite trend. Additionally, fish offered HCB diet showed relatively high values of whole-body lipid contents, tissue glycogen and lipid contents and plasma insulin levels, whereas plasma levels of glucose, advanced glycation end products and glycated serum protein significantly decreased compared with other treatments. Furthermore, benfotiamine improved the glucose tolerance of fish fed HC diet after a glucose load. High carbohydrate intake significantly up-regulated the mRNA levels of glucokinase, pyruvate kinase, glucose transporter 2, glycogen synthase, fatty acid synthetase and glucose-6-phosphate dehydrogenase, whereas the opposite was true for phosphoenolpyruvate carboxykinase, fructose-1,6-biphosphatase, glucose-6-phosphatase, carnitine palmitoyl transferase I and acyl-CoA oxidase. This also held true for fish fed HCB diet except for fatty acid oxidation process which was further enhanced. Overall, these findings suggested that benfotiamine benefited the glucose metabolism of Megalobrama amblycephala fed high-carbohydrate diet through the stimulation of glycolysis, glycogenesis, lipogenesis and fatty acid oxidation coupled with the depression of gluconeogenesis.Statement of relevanceThis study investigated the effects of dietary benfotiamine supplementation on growth performance, glucose homeostasis and intermediary metabolism of blunt snout bream. The data obtained here will facilitate our understanding of the potential mechanisms concerning the beneficial effects of benfotiamine on the carbohydrate metabolism of fish. It is also helpful for the development of low-protein and high-energy feed for fish.

Adequate dietary protein level enhances stress resistance and immune status of blunt snout bream (Megalobrama amblycephalaYih, 1955)

This study hypothesized that an optimum dietary protein level might play an important role in improving stress tolerance, enhancing an immune function, and ultimately minimizing temperature stress. For this purpose, the present study conducted a 10-week feeding trial followed by a 7-day stress experiment to evaluate the effects of dietary protein levels (28%–36%) on the physiological performances and hepatic Hsp70 gene expression in blunt snout bream Megalobrama amblycephala fry under a high temperature challenge. Fish fry (initial weight, 16.08 ± 0.03 g, n = 25) were fed with their respective diets to apparent satiation, and samples taken once before stress and four times during high temperature stress days (0.125, 0.5, 2 and 7 days). Serum total protein and cholesterol contents before stress were affected by dietary protein levels; during stress these parameters showed no significant changes up until day 2, showing some changes thereafter. Regardless of 0.125, 0.5, 2 or 7 days during stress, cortisol and aspartate aminotransferase levels in the group fed 32% dietary protein were significantly lower than in the other groups. At 0.125, 0.5 or 2 days during stress, the complement component 3 (C3) and 4 (C4) levels increased significantly up to certain levels, declining thereafter. The expression level of Hsp70 mRNA before stress was not affected by dietary protein levels, but increased significantly from 0.125 to 0.5 days during stress, and was reduced thereafter. Overall, low cortisol and high C3, C4 and Hsp70 mRNA levels were found in the group fed 32% protein throughout the stress experiment, which indicated that an adequate protein level enhances stress resistance and immunity in fish.

Dietary vitamin B12 requirement of fingerling blunt snout bream Megalobrama amblycephala determined by growth performance, digestive and absorptive capability and status of the GH-IGF-I axis

This study aimed to investigate the optimal dietary vitamin B12 requirement of fingerling blunt snout bream Megalobrama amblycephala based on the results of growth performance, intestinal digestive and absorptive capability and responses of the growth hormone (GH)-insulin-like growth factor-I (IGF-I) axis. Fish (initial body weight: 0.71±0.03g) were randomly assigned to six purified diets containing graded levels of vitamin B12 (0, 0.028, 0.051, 0.12, 0.23 and 0.41mg/kg) for 12weeks. Both weight gain (WG) and specific growth rate increased significantly (P<0.05) as dietary vitamin B12 levels increased from 0 to 0.051mg/kg, then plateaued with further increasing levels. Feed conversion ratio decreased as dietary vitamin B12 levels increased from 0 to 0.12mg/kg, but no statistical difference was observed. Whole-body composition and intestinal brush border enzymes activities also exerted little difference within the vitamin B12 range tested, whereas hepatic vitamin B12 contents increased remarkably (P<0.01) with increasing dietary vitamin B12 levels. Intestinal protease, amylase and lipase activities all increased significantly (P<0.05) as dietary vitamin B12 levels increased from 0 to 0.12mg/kg, but decreased remarkably (P<0.05) with further increasing vitamin B12 levels. Similar results were also observed in hepatic IGF-I expressions. Furthermore, the mRNA expressions of GH in the brain decreased significantly (P<0.05) with increasing dietary vitamin B12 levels. Based on the broken-line regression analysis of WG, the optimal dietary vitamin B12 requirement of fingerling blunt snout bream was estimated to be 0.06mg/kg. In addition, a supplementation of 0.12mg/kg vitamin B12 boosted intestinal digestive capability and hepatic IGF-I expression. Statement of relevanceThis study investigated the optimal dietary vitamin B12 requirement of fingerling blunt snout bream based on growth performance. The underlying mechanisms were also investigated with emphasis on intestinal digestive and absorptive capability and modulation of the GH-IGF-I axis. Data obtained here might facilitate the development of low-cost formulated feed for aquatic species.

Relationship between Lipid Oxidation, Protein Function Properties, and Freshness Changes of Salt-Treated Blunt-Snout Bream (Megalobrama amblycephala) Fillets Stored at 4°C

ABSTRACTThe aim of this study was to investigate the relationship between lipid oxidation, protein function properties, and freshness changes of blunt-snout bream (Megalobrama amblycephala) fillets treated with 2% and 4% salt during storage at 4°C. Salting with 2% and 4% salt could delay quality deterioration and protein denaturation, thus improving sensory attributes to some extent. But, 4% salt promoted lipid oxidation of blunt-snout bream fillets. There is a significant correlation (p < 0.05) between freshness indexes and lipid oxidation or protein function properties (total SH content, Ca2+-ATPase activity). Salting with 2% salt is an ideal treatment to control the quality of blunt-snout bream fillets stored at 4°C.

Dietary methionine requirement of pre-adult blunt snout bream, (Megalobrama amblycephalaYih, 1955)

Summary A nine-week feeding trial was conducted to test the hypothesis that an adequate methionine diet might improve growth, feed utilization, body composition and physiology, and biochemical parameters in pre-adult blunt snout bream Megalobrama amblycephala, whereas a methionine deficiency might have adverse effects on these parameters. Six isonitrogenous and isoenergetics semi-purified diets (33.0% crude protein, 7.0% crude lipid) were formulated to contain graded methionine levels (0.39–1.54% of dry weight) at 0.25% increments replaced by equal proportions of glycine. Results show that the survival rate (SR) was not significantly affected by the dietary methionine level. Final weight (FW), feed efficiency ratios (FER), weight gain (WG), and specific growth rate (SGR) increased with increasing dietary methionine levels up to 1.00% and then showed a declining trend. Using quadratic regression analysis of FER and SGR, the dietary methionine requirement was estimated to be 0.74% (2.24% of dietary protein) and 0.76% of the diet (2.30% of dietary protein), respectively. Fish fed the 0.39% methionine diet showed significantly lower whole body protein content compared to those fed with 0.85, 1.00 and 1.24% methionine diets (P 0.05). No significant differences were found in other indexes such as the hepatosomatic index (HSI), viscerosomatic index (VSI), condition factor (CF), albumin (ALB), total protein (TP), alanine aminotransferase (ALT), and spartate transaminase (AST) (P > 0.05). Most important, the optimal dietary methionine level of pre-adult blunt snout bream should be 0.74–0.76% of the diet (2.24–2.30% of dietary protein).

Effects of berberine on the growth and immune performance in response to ammonia stress and high-fat dietary in blunt snout bream Megalobrama amblycephala.

This study aimed to figure out the effects of berberine on growth performance, immunity, oxidative stress and hepatocyte apoptosis of blunt snout bream (Megalobrama amblycephala) fed with high-fat diet. 320 fish (80.00±0.90g) were divided randomly into four trial groups (each with four replicates) and fed with 4 diets (normal diet, normal diet with 50mg/kg berberine, high-fat diet, high-fat diet with 50mg/kg berberine), respectively. At the end of the feeding trial, ammonia stress test was carried out for 5 days. The result showed the growth performance, immune parameters including plasm acid phosphatase (ACP) activities, lysozyme (LYZ) activities and alternative complement C3 and C4 contents were suppressed in fish fed with high-fat diets but improved in berberine diets compared with control (normal diet). Hepatopancreas oxidative status, the malondialdehyde (MDA), protein carbonyl (PC) and lipid peroxide (LPO) were increased significantly (P<0.05) when fish were fed with high-fat diets. Berberine could slow the progression of the oxidative stress induced by high-fat through increasing superoxide dismutase (SOD) activities and total sulfydryl (T-SH) levels of fish. And the hepatocyte apoptosis in the high-fat group could also be alleviated by berberine. After the ammonia stress test, the accumulative mortality was extremely (P<0.05) low in fish fed high-fat diet with berberine compared to other groups. It was concluded berberine as a functional feed additive significantly inhibited the progression of oxidative stress, reduced the apoptosis and enhanced the immunity of fish fed with high-fat diet.