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Palm oil, with its higher production, lower prices, and higher levels of palmitic acid and oleic acid, may have great potential for use in the aquafeed industry. In this study, with an 8‐week feeding experiment, the efficacy of palm oil as a substitute for fish oil in tiger puffer feeds was comprehensively evaluated. The control diets (FO group) contained 8% marine fish oil as the main lipid source, while in the treatment diets, the added marine fish oil was replaced with palm oil at 25%, 50%, 75%, and 100%, respectively, which was named 25PO, 50PO, 75PO, and 100PO, respectively. Juvenile tiger puffers with an initial weight of 15.0 ± 0.04 g were used, with three replicate tanks of 30 juvenile fish tiger puffer for each dietary group. The fish oil replacement by palm oil did not have an adverse effect on fish growth and feeding, but the weight gain decreased by 17.3% in group PO100. Palm oil had no significant effects on fish proximate composition and muscle texture. The effects of dietary palm oil on muscle fatty acid composition were not significant, with DHA and EPA significantly lowered only in the 100PO group. In contrast, the changes in liver and intestinal fatty acid compositions in response to diets were more significant than those in the muscle. In the intestine, the replacement of more than 50% fish oil by palm oil significantly downregulated the gene expression associated with peroxisomal fatty acid β‐oxidation and triglyceride hydrolysis, while upregulated the expression of cholesterol biosynthetic genes. In the liver, the replacement of more than 75% fish oil also significantly upregulated the cholesterol synthesis. In conclusion, palm oil can replace 75% of added marine fish oil in tiger puffer diets and does not adversely affect the growth performance, feed utilization, muscle composition, and muscle texture. [ABSTRACT FROM AUTHOR]

Myostatin (MSTN), a member of the transforming growth factor‐β (TGF‐β) superfamily, has retained the function of inhibiting muscle growth in fish. Turbot Scophthalmus maximus possesses two MSTN paralogs (MSTNa and MSTNb), but their respective response to dietary nutrients is still unclear. To clarify the effects of fish protein hydrolysate (FPH) on MSTNa and MSTNb, their mRNA levels were quantified in the muscle using the fasting–refeeding experiment and long‐term feeding trial. Gene expressions in various tissues showed that MSTNb but not MSTNa was expressed mostly in the muscle. After 2 weeks of starvation, MSTNa expression was up‐regulated in the muscle by refeeding FPH diet at 3 h and 6 h, while MSTNb expression was affected from 3 h to 3 days. Moreover, changes in MSTNb expression over time showed that significant reduction was observed at 3 h in fish refed optimal levels of FPH, but at 6 h in fish refed excessive levels of FPH. The expressions of two MSTN paralogs and related gene expressions of TGF‐β/SMAD‐dependent signalling pathway were not significantly altered by graded levels of FPH after 7 days of refeeding, while the expressions of MSTNb as well as the upstream FMODa and downstream SMAD4 were significantly affected after the long‐term feeding trial (8 weeks). In conclusion, FPH mainly modulated the expression of MSTNb in the muscle, whereas MSTNa was only affected in the early stage of refeeding. Furthermore, during the refeeding period, optimal levels of FPH in diets may regulate MSTNb more rapidly to initiate compensatory growth. [ABSTRACT FROM AUTHOR]

The relative shortage of fishmeal is challenging the sustainable development of aquaculture industry. A 56‐day feeding trial was conducted to evaluate the efficacy of fishmeal replacement by poultry by‐product meal (PBM) in juvenile obscure pufferfish. The basal diet with 45% (dry matter) fishmeal was used as the control diet, and in the four experimental diets PBM was added into the control diet to replace fishmeal at the level of 15% (PBM15), 30% (PBM30), 45% (PBM45) and 60% (PBM60) respectively. Each diet was fed to triplicate tanks, each of which was stocked with 30 fish. PBM30 did not significantly affect the growth performance, nutrient apparent digestibility coefficient, proximate composition, amino acid profile, muscle texture and serum biochemical indices (p > 0.05). PBM45 did not significantly (p > 0.05) affects the weight gain, but reduced the feed efficiency ratio (p < 0.05). PBM60 resulted in significantly reduced fish growth (p < 0.05). PBM‐supplemented diets resulted in lower contents of long chain‐polyunsaturated fatty acid in the liver, but higher deposition of C18:1n‐9 and C18:2n‐6 in experimental fish (p < 0.05). In conclusion, replacing 30% fishmeal with PBM in the diet did not compromise the growth performance, feed utilisation, health status and muscle texture of farmed obscure pufferfish. [ABSTRACT FROM AUTHOR]

The study was conducted to investigate the effects of fish protein hydrolysate (FPH) in diets for turbot on growth performance, muscle fibre morphometry, and the expression of muscle growth‐related genes. A control diet (FPH0) contained 0 g/kg FPH, and four experimental diets were formulated replacing fishmeal with FPH at levels of 45 (FPH4.5), 120 (FPH12), 180 (FPH18) and 300 (FPH30) g/kg. Fish fed the FPH12 and FPH18 diets had higher specific growth rate (SGR) than fish fed the FPH0 diet (p <.05), and a quadratic regression was found between SGR and dietary FPH level (p =.001, R2 =.677). Cross‐section area (CSA) and the length of sarcomere in the FPH12 group increased compared with the control group (p <.05), and a quadratic regression was observed between CSA and dietary FPH level (p =.006, R2 =.574) and between sarcomere length and dietary FPH level (p =.018, R2 =.788). An appropriate level of FPH down‐regulated myostatin 2 gene expression and up‐regulated proliferating cell nuclear antigen gene expression, while the expression of myogenic regulatory factors was not affected by dietary treatments (p >.05). To conclude, an appropriate level of FPH may improve muscle growth by regulating the expression of muscle growth‐related genes, and muscle microstructure and ultrastructure. [ABSTRACT FROM AUTHOR]

A 3-month feeding trial with tongue sole Cynoglossus semilaevis broodstock was conducted before and during the spawning season to investigate the effects of dietary arachidonic acid (ARA) on the production of sex steroid hormones and gonadal gene expression of key proteins in steroidogenesis. Three isonitrogenous and isolipidic experimental diets were formulated to contain different ARA levels: the control diet without ARA supplementation (C, 0.58% ARA of total fatty acids (TFA)) and two diets with low (5.14% of TFA, ARA-L) or high ARA (15.44% of TFA, ARA-H) supplementation. The diets were randomly assigned to 9 tanks of 3-year-old tongue sole (10 females and 15 males in each tank). Fish were reared in a flowing seawater system and fed to apparent satiation twice daily. At the end of the feeding trial, tissue samples from mature females (MF, with spontaneous ovulation), immature females (IMF, early vitellogenesis), and mature males (MM, expressing milt) were collected to assay the production of sex steroid hormones, gonadal gene expression of sex steroid-synthesizing proteins, as well as the fatty acid profiles of gonad, liver and muscle lipids. Results showed that ARA supplementation significantly reduced the estradiol production in females, but stimulated the testosterone production in males. ARA supplementation significantly reduced the mRNA expression of aromatase in ovaries but significantly increased the gene expression of 3β-hydroxysteroid dehydrogenase (3β-HSD) in testes. In mature ovaries, diet ARA-L significantly reduced the gene expression of follicle stimulating hormone receptor (FSHR), 3β-HSD, and 17β-HSD; however, in immature ovaries, it significantly increased the gene expression of FSHR, steroidogenic acute regulatory protein (StAR), cholesterol side-chain cleavage enzyme (P450ssc), 3β-HSD, and 17β-HSD. In all gonads, 17α-hydroxylase (P450c17) responded to dietary ARA differently from other sex steroid-synthesizing proteins. ARA was preferentially accumulated in tongue sole gonad lipids. ARA concentrations were highest in gonad, liver and muscle lipids of MM fish and lowest in MF fish. Compared to female tongue sole, males had higher DHA concentrations in gonad lipids, but lower concentrations in liver lipids. In conclusion, results suggest dietary ARA regulates sex steroid hormone synthesis in tongue sole broodstock, and accumulates in gonad lipids, depending on both fish gender and maturation stage. Dietary ARA supplementation appears more important for male fish than for female fish, and more important for immature females than for mature females. Statement of relevance This study is beneficial to the broodstock diet formulation. [ABSTRACT FROM AUTHOR]

A 10-week feeding experiment in offshore floating cages was conducted to investigate the effects of dietary fatty acid profiles on growth, tissue lipid accumulation, liver histology and flesh texture of juvenile Japanese seabass (mean initial weight 29.53 ± 0.86 g). Six low-fish meal diets were prepared with different lipid sources (10% in the diets), each with a characteristic fatty acid: Diet MCA: medium-chain fatty acid, C8:0 + C10:0; Diet PA: palmitic acid, C16:0; Diet SA: stearic acid, C18:0; Diet OA: oleic acid, C18:1n − 9; Diet LNA: α-linolenic acid, C18:3n − 3; Diet N-3 LC-PUFA: n − 3 LC-PUFA, DHA + EPA. A diet with 10% fish oil was used as the control diet (Diet FO). Each diet was fed triplicate groups of 30 fish. The results showed that the compared to group FO, the final body weight (FBW), specific growth rate (SGR) and feed efficiency ratio (FER) were significantly reduced in groups MCA, PA, and SA, but not in groups OA, LNA, and N-3 LC-PUFA. The feed intake (FI) in group MCA was much lower compared to other groups, while group PA showed the highest FI, significantly higher than that in group N-3 LC-PUFA. Diets MCA, PA, and SA leaded to much lower lipid content in muscle, gut, and whole fish body, while the liver lipid content was significantly higher in groups PA, SA, OA, and LNA than that in groups FO, MCA, and N-3 LC-PUFA. Obvious hepatocytes swelling, lipid vacuolization and nucleus polarization were observed in liver from groups OA, SA, PA, and LNA, while in group MCA, the hepatic tissue was in disorder with indistinguishable hepatic cell outline and dissolved nuclei. Fish fed MCA, PA, and SA tended to have firmer flesh than fish fed OA, LNA, and N-3 LC-PUFA. These results showed that Japanese seabass has a relatively high tolerance to oils rich in C18:1n − 9 and C18:3n − 3 but high levels of C16:0 or C18:0 enriched lipid sources could reduce the feed efficiency and growth rate. High levels of medium chain fatty acids (C8:0 and C10:0) in the diets could drastically reduce the feed intake. All the alternative lipid sources leaded to impairment to liver histology and modified the flesh texture, probably via altering tissue lipid concentrations. Statement of relevance This study provided useful data for the application of a range of alternative lipid sources in fish feed. Also, the present results are helpful in formulating a balanced dietary fatty acid profile for Japanese seabass. [ABSTRACT FROM AUTHOR]

A 12-week feeding experiment in indoor flowing seawater system was conducted to investigate the effects of graded levels of dietary fish protein hydrolysate (FPH) on growth performance and lipid accumulation of juvenile turbot ( Scophthalmus maximus ) (initial body weight 4.16 ± 0.01 g). Four isonitrogenous and isoenergetic experimental diets with high plant protein were formulated to contain graded levels of FPH, meanwhile the fish meal was replaced correspondingly by 0% (Diet FPH-0, control), 5% (Diet FPH-5), 10% (Diet FPH-10) and 20% (Diet FPH-20) of total dietary protein, respectively. Quadruplicate groups of 25 fish were fed to apparent satiation twice daily during the feeding trial. The results showed that the specific growth rate (SGR), protein efficiency ratio, and protein retention was not significantly different among group FPH-0, FPH-5, and FPH-10. The highest level of dietary FPH (FPH-20) significantly reduced the SGR but increased the feed intake compared to the control group. The viscerosomatic index in group FPH-10 and FPH-20 were significantly lower than that in the control group. Fish fed FPH-20 also showed significantly lower crude lipid concentration in whole body than fish fed the control diet. The concentrations of total and neutral lipid in gut were significantly lower in fish fed FPH-10 compared to the control group. For muscle lipid, the polar lipid concentration significantly decreased while the neutral lipid concentration significantly increased with increasing levels of dietary FPH, but no significant difference in total lipid concentration was observed among experimental groups. The lipid concentrations in liver were not significantly different among dietary treatments. With increasing levels of dietary FPH, serum triacylglycerol and cholesterol concentrations significantly decreased. The influence of dietary FPH on tissue fatty acid compositions generally corresponded with that on tissue lipid concentrations. In conclusion, these results suggested that in high plant protein diets FPH replacing fish meal by 10% of total dietary protein did not compromise the growth of juvenile turbot. However, a higher FPH level (replacing fish meal by 20% of total dietary protein) reduced the growth and feed utilization but it increased the feed intake. In the present experimental conditions, the FPH treatments, especially at high levels, significantly modulated the lipid accumulation and fatty acid compositions in turbot tissues, in a dose- and tissue-dependent manner. Statement of Relevance This study provided useful data for the circulatory use of fish processing by-products in fish diets. Also, based on the results of lipid analysis in fish tissues, potential lipid manipulating feed additives could be explored from fish protein hydrolysates. [ABSTRACT FROM AUTHOR]

A 10-week feeding experiment was conducted to investigate the effects of dietary DHA/ EPA ratio on juvenile Japanese seabass reared in sea floating cages. Six practical diets were formulated differing only in DHA/ EPA ratio: 0.55 (Diet D/E0.55), 1.04 (D/E1.04), 1.53 (D/E1.53), 2.08 (D/E2.08), 2.44 (D/E2.44) and 2.93 (D/E2.93). All diets had the same contents of total n-3 long-chain polyunsaturated fatty acid ( LC- PUFA) and arachidonic acid ( ARA). The results showed that the final weight and specific growth rate significantly increased with increasing dietary DHA/ EPA ratio from 0.55 to 2.08 and thereafter declined. Activities of lysozyme and superoxide dismutase in serum in groups with DHA/ EPA of 1.53-2.93 was significantly higher compared to group D/E0.55 while the activity of serum alternative complement pathway in group D/E2.93 was significantly lower compared with group D/E1.53. However, no difference was observed in activities of both respiratory burst of head kidney macrophage and serum catalase among dietary treatments. The per cent survival after air exposure in group D/E1.53, D/E2.08 and D/E2.93 was significantly higher compared with group D/E0.55. The fatty acid composition of whole body and tissues reflected closely those of diets, while fish accumulated more DHA than EPA in fish tissues, especially in muscle. These results suggested that at the same dietary contents of n-3 LC- PUFA (appr. 18% of TFA) and ARA (appr. 0.7% of TFA), moderate dietary DHA/ EPA ratios of 1.53-2.08 significantly enhanced growth performances, certain innate immune responses, and the stress tolerance of Japanese seabass, in accordance with the preferential incorporation of DHA into fish tissues. [ABSTRACT FROM AUTHOR]

Ethoxyquin (EQ) is the most common synthetic antioxidant used for preventing rancidity in fish foodstuffs. However, literature related to the effects of dietary EQ on performance of fish was limited. The present study was conducted to investigate the effects of EQ on performance and EQ residue in muscle of juvenile Japanese seabass Lateolabrax japonicus and to estimate the optimal EQ concentration in the diet. Graded levels [0 (control), 50, 150, 450 and 1350 mg EQ kg−1 diet] of EQ were added to the basal diet, resulting in five dietary treatments in the experiment. Each diet was fed to triplicate groups of seabass (initial body weight 8.01 ± 0.76 g) for 12 weeks in floating sea cages (1.5 × 1.5 × 2.0 m, 30 fish per cage). Survival ranged from 78.9 to 86.7%, and was irrespective of dietary EQ levels. The specific growth rate (SGR) of fish fed diets supplemented with ≤50 mg kg−1 EQ had significantly ( P < 0.05) higher SGR than fish fed diets supplemented with ≥150 mg kg−1 EQ, the highest SGR was observed in fish fed diet with 50 mg kg−1 EQ supplementation. Feed intake (FI) and feed efficiency (FE) were not significantly ( P > 0.05) different among dietary treatments. Fish fed diets with 50 and 1350 mg kg−1 EQ had a significant ( P < 0.05) lower body lipid content than fish in the control group. Muscle EQ level significantly increased when dietary EQ increased. Optimal EQ concentration estimated by polynomial regression based on maximum growth of juvenile Japanese seabass was 13.78 mg kg−1 diet. [ABSTRACT FROM AUTHOR]

An 8-week feeding experiment was conducted to investigate the effects of dietary glycyrrhizic acid ( GA) on growth, survival and immune response of juvenile large yellow croaker, in seawater floating net cages. GA was supplemented into the basal diet to formulate four isonitrogenous and isoenergetic practical diets containing 0.00% (the control diet), 0.01%, 0.02% and 0.04% GA of dry weight, respectively. Triplicate groups of 60 fish were fed to apparent satiation by hand twice daily. The results showed that the specific growth rate, survival rate and feed efficiency ratio revealed no significant differences among dietary treatments ( P > 0.05). The phagocytic index of head kidney macrophage was significantly increased by the supplementation of 0.04% dietary GA compared to the control group ( P < 0.05). Fish fed 0.04% dietary GA also showed significantly higher serum lysozyme activity than fish fed the control diet and diet with 0.01% GA ( P < 0.05). The cumulative mortality rate after natural infestation of parasites (protozoan, Cryptocaryon irritans Brown) showed no significant differences among dietary treatments. These results suggested that dietary glycyrrhizic acid improved certain non-specific immunological parameters of juvenile large yellow croaker. However, GA was not able to protect juvenile large yellow croaker effectively from protozoan infection. [ABSTRACT FROM AUTHOR]

Abstract: A feeding experiment was conducted to examine the effects of dietary administration of Bacillus subtilis and fructooligosaccharide (FOS) on growth performance, survival, immune responses and disease resistance of juvenile large yellow croaker, Larimichthys crocea (mean initial body weight 7.82g±0.68). Nine practical diets were formulated to contain three levels of B. subtilis (0.0, 0.42×107 cfug−1 and 1.35×107 cfug−1), each with three FOS levels (0, 0.2% and 0.4% of dry weight). Each diet was randomly assigned to triplicate groups of 60 juveniles. The experiment was conducted in floating sea cages (1.0×1.0×1.5m) for 10weeks. At the termination of the feeding trial, alternative complement pathway (ACP), superoxide dismutase (SOD) and lysozyme activity of serum and respiratory burst activity of head kidney macrophage were determined and fishes were challenged intraperitoneally with Vibrio harveyi. The results showed that at each dietary FOS level, dietary supplementation of 1.35×107 cfug−1 B. subtilis significantly increased the specific growth rate (SGR) (P <0.01) and feed efficiency ratio (FER) (P <0.05) compared with the groups without B. subtilis supplementation. The immune assay showed that at each FOS level, compared to the groups without B. subtilis supplementation significantly enhanced serum lysozyme was observed in fish fed the B. subtilis-supplemented diets (P <0.05) and significantly enhanced serum SOD activity was observed in fish fed the diet with 1.35×107 cfug−1 B. subtilis (P <0.05), while the serum ACP activity and the respiratory burst activity of head kidney macrophage were independent of dietary treatments. The challenge experiment showed that compared to the groups without B. subtilis supplementation the cumulative mortality after infection with V. harveyi was significantly lower in fish fed the diet with 1.35×107 cfug−1 B. subtilis (P <0.05), at each FOS level. However, at each dietary B. subtilis level, addition of FOS in diets did not significantly affect the growth performance, immune response and disease resistance of large yellow croaker. No significant interactions were observed between dietary B. subtilis and FOS. These results showed that dietary supplementation of B. subtilis at a dose of 1.35×107 cfug−1 improved growth, feed efficiency ratio, non-specific immune responses and disease resistance of juvenile large yellow croaker, L. crocea. [Copyright &y& Elsevier]

Abstract: A 12-week feeding experiment was conducted to investigate the effects of dietary arachidonic acid (ARA) on growth, survival, immune response and tissue fatty acid composition of juvenile Japanese seabass (Lateolabrax japonicus) (mean initial weight 9.48±0.09g) in seawater floating net cages (1.5×1.5×2.0m). An ARA-enriched oil was supplemented into the basal diet to formulate six isonitrogenous and isoenergetic practical diets containing 0.08% (the control group), 0.22%, 0.36%, 0.56%, 1.33% and 2.12% ARA of dry weight, respectively. All diets had the same total n−3 long chain polyunsaturated fatty acid (LC-PUFA) level and 22:6n−3/20:5n−3 ratio. Triplicate groups of 30 fish were fed to apparent satiation twice daily for 12weeks. The water temperature ranged from 22.5 to 31.5°C, the salinity from 28‰ to 33‰ and the dissolved oxygen content was approximately 6mgl−1 during the experimental period. The results showed that final weight (FW) and specific growth rate (SGR) significantly increased with increasing dietary ARA from 0.08% to 0.36% (P <0.01) and thereafter declined. The feed efficiency ratio (FER) had the similar pattern with SGR, and fish fed the diet with 0.36% ARA showed significantly higher FER than the control (P <0.05). No significant differences were found in survival rate among dietary treatments (P >0.05). The hepatosomatic index (HSI) decreased significantly with the increase of dietary ARA, and HSI in fish fed the diets with more than 0.22% ARA content were significantly lower than the control group (P <0.01). The serum lysozyme (LYZ), alternative complement pathway (ACP) and superoxide dismutase (SOD) activity were significantly enhanced by the supplementation of ARA, especially in moderate supplementation (0.36–0.56%). However, there were no differences in both respiratory burst activity of head kidney macrophage and serum catalase (CAT) activity among dietary treatments. The body composition analysis showed that whole-body protein first increased, then decreased with increasing dietary ARA, while whole-body lipid content followed the opposite pattern. The fatty acid composition of whole body and liver reflected closely those of the diets, while liver EPA levels were inversely related to dietary ARA. These results suggested that dietary ARA, especially moderate ARA level (0.22–0.56% d.w.), significantly enhanced growth and immune response and modified the chemical composition of whole body and liver of Japanese seabass juvenile. [Copyright &y& Elsevier]

A 63-day feeding trial was conducted to evaluate the effect of Clostridium autoethanogenum protein (CAP) on the growth, digestibility, postprandial free amino acid concentrations in serum, and gene expression related to protein metabolism in obscure pufferfish (Takifugu obscurus). The basal diet with 420 g/kg of fishmeal was used as the control diet (CAP0), and then 20 % (CAP20), 40 % (CAP40) and 80 % (CAP80) dietary fishmeal were replaced by CAP. Compared with diet CAP0, the growth and feed utilization was not affected in fish fed diet CAP20, but was significantly reduced in fish fed diets CAP40 and CAP80 (P < 0.05). The apparent digestibility coefficients (ADCs) of dry matter and protein in the CAP80 group were significantly lower (P < 0.05) than those of the other three groups, and the ADC of lipid was significantly decreased (P < 0.05) in the CAP40 and CAP80 groups. Fish fed diets CAP40 and CAP80 had lower taurine content in muscle compared to those fed diets CAP0 and CAP20 (P < 0.05). Higher free essential amino acid concentrations in serum were observed in fish fed diet CAP80 compared to the other diets at 2 h after refeeding (P < 0.05). Fish fed diets CAP40 and CAP80 showed lower hardness and gumminess in muscle than those fed the other diets (P < 0.05). The expression of peptide transporter1 (PepT1) in intestine and target of rapamycin (TOR) in muscle were significantly up-regulated in the CAP40 groups compared to the control (CAP0) (P < 0.05). However, relative expressions of 4F2 heavy chain (4F2hC), L-type amino acid transporter 2 (y+LAT2) and T-type amino acid transporter1(TAT1) in intestine were not significantly affected by graded levels of CAP (P > 0.05). The inclusion of CAP did not significantly affect the expression of ribosomal protein S6 kinase 1 (S6K1), eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) and 4E-BP2 (P > 0.05) in muscle and liver. In summary, in a basal diet containing 420 g/kg fishmeal, 20 % fishmeal in diets could be successfully substituted by CAP, while high-level CAP decreased the growth, feed utilization and digestibility in juvenile obscure pufferfish. The main reasons for the inhibition of growth performance were probably that excessive CAP caused dietary taurine deficiency and the imbalance of amino acid absorption. • CAP can partially substitute fishmeal without negative effects on growth and feed utilization in obscure pufferfish. • Fishmeal replacement by CAP significantly up-regulated the expressions of TOR and PepT1 at transcriptional level. • Excessive CAP may cause dietary taurine deficiency and the imbalance of amino acid absorption. [ABSTRACT FROM AUTHOR]

A feeding trial was conducted to determine the effects of dietary chromium polynicotinate (Cr-Nic) on growth, feed utilization, and resistance to Cryptocaryon irritans in juvenile large yellow croaker ( Larimichthys crocea ). Six diets containing 42% crude protein and graded levels of Cr-Nic (0, 5, 10, 20, 40 and 80 mg kg − 1 diet) were fed to croaker juveniles initially averaging 8.74 ± 0.48 g for 10 weeks. Another diet containing 45% crude protein without Cr-Nic supplementation was also fed and served as a control. Wheat starch was used as the carbohydrate source for all of the experimental diets. Fish fed the diet supplemented with 5 mg kg − 1 Cr-Nic had significantly higher rates of survival, specific growth rate (SGR), feed efficiency (FE), and protein efficiency ratio (PER), but lower feed intake than fish fed diets with 0 and 80 mg kg − 1 Cr-Nic. Fish fed the diet containing 5 mg kg − 1 Cr-Nic had significantly higher SGR and PER than fish fed the 45% crude protein control diet. Analysis of SGR, FE, and PER by second-order regression indicated that the optimal dietary level of Cr-Nic for juvenile large yellow croaker was estimated to be 6.70–7.10 mg kg − 1 of diet. The 3-week cumulative mortality rate following natural infection of the parasite C. irritans was lowest in fish fed the diet containing 5 mg kg − 1 Cr-Nic, which was significantly lower than in fish fed the diet without Cr-Nic addition. It is suggested that Cr-Nic supplementation protects against C. irritans infection prior to parasitic outbreak to alleviate mortality. [ABSTRACT FROM AUTHOR]

Abstract: The study was conducted to investigate the effects of dietary n-3 highly unsaturated fatty acid (n-3 HUFA) on growth, nonspecific immunity, expression of some immune related genes and disease resistance of juvenile large yellow croaker (Larmichthys crocea) following natural infestation of parasites (Cryptocaryon irritans). Six isoproteic and isolipidic diets were formulated with graded levels of n-3 HUFA ranging from 0.15% to 2.25% of the dry weight and the DHA/EPA was approximately fixed at 2.0. Each diet was randomly allocated to triplicate groups of fish in floating sea cages (1.0 × 1.0 × 1.5 m), and each cage was stocked with 60 fish (initial average weight 9.79 ± 0.6 g). Fish were fed twice daily (05:00 and 17:00) to apparent satiation for 58 days. Results showed that moderate n-3 HUFA level (0.98%) significantly enhanced growth compared with the control group (0.15% HUFA) (P < 0.05), while higher n-3 HUFA levels (1.37%, 1.79% and 2.25%) had detrimental effects on the growth though no significance was found (P > 0.05). Nitro blue tetrazolium (NBT) positive leucocytes percentage of head kidney and serum superoxide dismutase (SOD) activity increased with increasing n-3 HUFA from 0.15% to 0.60%, and decreased with further increase of n-3 HUFA from 0.60% to 2.25% (P < 0.05). Serum lysozyme activity increased significantly as n-3 HUFA increased from 0.15% to 1.37%, and then decreased with n-3 HUFA from 1.37% to 2.25% (P > 0.05). There were no significant differences in phagocytosis index (PI) of head kidney leucocytes among dietary treatments (P > 0.05). The hepatic mRNA expression of Toll-like receptor 22 (TLR22) and Myeloid differentiation factor 88 (MyD88) was significantly up-regulated in fish fed the diets with low or moderate levels, while in kidney this increment was only found at specific sampling time during the natural infestation of parasites. The 13 d cumulative mortality rate following natural infestation of parasites decreased with n-3 HUFA increased from 0.15% to 0.60% (P < 0.05), and significantly increased with n-3 HUFA from 0.60% to 2.25% (P < 0.05). Results of this study suggested that fish fed low or moderate dietary n-3 HUFA had higher growth, nonspecific immune responses, expression levels of some immune related genes and disease resistance of large yellow croaker following natural infestation of parasites and dietary n-3 HUFA may regulate fish immunity and disease resistance by altering the mRNA expression levels of TLR22 and MyD88. [Copyright &y& Elsevier]

Abstract: Ethoxyquin (6-ethoxy-2, 2, 4-trimethyl-1, 2-dihydroquinoline (EQ)) is the most common synthetic antioxidant in fish feed. However, there was little literature related to the effects of dietary EQ on growth performance of fish. The present study was conducted to investigate the effects of EQ on survival, growth, feed utilization, and body composition of large yellow croaker Pseudosciaena crocea. Five experimental diets were formulated to contain graded levels of EQ (0, 50, 150, 450 and 1350mgkg−1). Each diet was randomly fed to three sea cages (1.0×1.0×1.5m), and each cage was stocked with 60 fish (with an initial body weight of 7.82±0.68g). Survival was more than 93%, and irrespective of dietary EQ levels. Specific growth rate (SGR) decreased with the increase of dietary EQ. SGR of fish fed the diet with 1350mgkg−1 EQ was significantly lower than the other treatments. There were no significant differences in SGR among fish fed diets with or less than 450mgkg−1 EQ. No significant difference in feed intake (FI) was found among dietary treatments. Feed efficiency ratio (FER) first increased, and then decreased with increasing dietary EQ, but no significant differences were observed among dietary treatments. No significant differences were found in moisture, protein, and ash content among dietary treatments. The lipid content, however, in fish fed the diets with EQ was higher than those fed the diet without EQ. The hepatosomatic index (HSI) and condition factor (CF) generally decreased with increasing dietary EQ level. The CF in fish fed the diet containing 1350mgkg−1 EQ was significantly lower than the others. The viscerosomatic index (VSI) of fish firstly decreased with the increase of dietary EQ, the lowest value was recorded in fish fed diet with 150mgkg−1 EQ, then increased with increasing dietary EQ. Results of the present study showed that EQ level in the diet of large yellow croaker should not exceed 50mgkg−1. [Copyright &y& Elsevier]

A feeding trial was conducted to test the efficacy of the fish oil-finishing strategy in a lean marine teleost, tiger puffer (average initial body weight, 19.50 g). During the 50-day growing-out period, fish was fed diets differing only in supplemented lipid source (6% of dry dietary matter), namely, fish oil (FO), tiger puffer liver oil (TO), linseed oil (LO), soybean oil (SO), rapeseed oil (RO), palm oil (PO), and beef tallow (BT). In the fish oil-fishing period, all the fish were fed diet FO for 30 days. The results showed that the fish oil-finishing strategy restored the muscle DHA content in terrestrially sourced oil (TSO)-based groups to be 82.8–91.6% of that in fish fed fish oil continuously. Compared to DHA, muscle EPA was less easily retained during the growing-out period, but more easily restored during the fish oil-finishing period. Compared to muscle, the LC-PUFA contents in liver of tiger puffer were much lower and more difficult to restore by the fish oil-finishing strategy. LO, RO and BT resulted in significant growth reduction than FO at the end of growing-out period, but this reduction no longer existed at the end of the fish oil-finishing period. Compensatory effects of fish oil re-feeding were also observed for LC-PUFA deposition. Very little difference was observed in fish proximate composition, somatic parameters, and muscle texture among dietary groups during the whole feeding period, but the lipid metabolism-related biochemical parameters in the serum were significantly affected by diet. Liver oil of farmed tiger puffer can be used a suitable and safe lipid source for diets of tiger puffer, and beef tallow seems a better dietary lipid source for tiger puffer than other TSO in terms of easy restoration of LC-PUFA and growth by the fish oil-finishing strategy. In conclusion, the fish oil-finishing strategy had high efficiency in restoring LC-PUFA and growth of tiger puffer previously fed TSO-based diets. • DHA was easily retained in muscle of tiger puffer fed terrestrial oils. • The fish oil-finishing had high efficiency in restoring LC-PUFA in tiger puffer. • Compensatory effects of fish oil-finishing existed for both LC-PUFA and growth. • Liver oil of tiger puffer and beef tallow are good lipid sources for tiger puffer. • Fish proximate composition and muscle texture were not affected by dietary oils. [ABSTRACT FROM AUTHOR]

Bile acid (BA) plays an important role in lipid metabolism. Tiger puffer has a unique lipid storage pattern; storing lipid predominantly in the liver. The present study aimed to investigate the effects of dietary BA supplementation on hepatic lipid accumulation and metabolism in tiger puffer fed normal or high-lipid diets. An 8-week feeding trial was conducted in an indoor flow-through seawater system. Two diets with suitable (8.5%, diet C) or high lipid level (12.5%, diet HL) were prepared. BA, a porcine bile extract mainly comprised of hyodeoxycholic acid was supplemented into the two diets at the level of 0.02% to formulate diet CBA and diet HLBA, respectively. A fifth diet was prepared by supplementing an excess level of porcine bile extract (0.10%) into diet C (diet CHBA). Each diet was randomly fed to triplicate tanks. Dietary BA supplementation did not significantly affect fish growth performances. Dietary BA tended to decrease the whole-body lipid content, liver lipid content, hepatosomatic index, and viscerasomatic index in both fish fed with normal diets and fish fed with high-lipid diets. Similar results were observed for the contents of triacylglycerol, total cholesterol, and low-density lipoprotein-cholesterol in serum. The quantitative bile acid metabolomics analysis showed that taurocholic acid and taurochenodeoxycholic acid were dominantly abundant in the gallbladder. Dietary BA supplementation increased the concentration of taurohyodeoxycholic acid, glycohyodeoxycholic acid, and glycocholic acid, but affected some other BAs in various patterns. Dietary BA regulated hepatic transcription of lipid metabolism-related genes differentially in fish fed normal diets and fish fed high-lipid diets, decreasing the transcription of lipogenic genes in fish fed normal diets but increasing the transcription of genes related to lipid digestion and lipid/cholesterol transport in fish fed high-lipid diets. In conclusion, dietary BA supplementation tended to reduce the lipid accumulation in juvenile tiger puffer. However, at the transcription level the regulation of lipid metabolism by dietary BA seemed very different between fish fed normal diets and fish fed high-lipid diets. This study contributes to the general knowledge of bile physiology under different nutritional conditions in teleost and is beneficial to lipid management in tiger puffer farming. • Dietary bile acid tended to decrease hepatic lipid accumulation and serum triacylglycerol and cholesterol levels. • Dietary bile acid increased the contents of taurochenodeoxycholic acid and taurohyodeoxycholic acid in the gallbladder. • Dietary bile acid regulates gene transcription differentially in fish fed normal diets and fish fed high-lipid diets. • Dietary bile acid decreased the transcription of lipogenic genes only in fish fed normal diets. [ABSTRACT FROM AUTHOR]