Diets For Sea Bass Research Articles

Effect of Aspergillus niger Fermented Soybean Meal Supplementation in Formulated Diets on Growth Performances in Juvenile Asian Seabass (Lates culcarifer Bloch)

The utilization of indigenous mold Aspergillus niger from aquaculture areas to improve the quality of soybean meal (SM) by fermentation and replacement in Asian seabass diet was studied on growth performances and feed utilization in juvenile Asian seabass, Lates calcalifer. Sinking diets with 40 % of protein were formulated. The main sources of protein in the diets were from fish meal (FM). Low substitution levels of 4 % of protein from SM, 10 % of total protein, were used in diets D1 - D4 with replacement of fermented soybean meal (FSM) at 0, 25, 75, and 100 %, respectively, and high substitution levels of 8 % of protein from SM, 20 %of total protein, were used in diets D5 - D8 with replacement of FSM at 0, 25, 75, and 100 %, respectively. Initial weight of juvenile Asian seabass was 12.83 - 12.90 g. 10 fish were stocked in 100 L glass tanks with triplicate groups. Each diet was fed to apparent satiation twice daily for 10 weeks. The results presented that the final body weight (BW), specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER), and feed capital showed significant difference (P < 0.05) while final total length (TL), survival rate (SR), carcass percentage, and hepatosomatic index (HSI) did not show significant difference (P > 0.05). The 4 % of protein from SM was able to be replaced by 25 - 100 % of FSM with increased growth performances and feed utilization, while feed cost (Thai baht kg-1 of fish) was reduced, respectively. The A. niger FSM is alternative protein source for growth, feed utilization improvement, and feed cost reduction of Asian seabass farmers.

Use of technological processing of seaweed and microalgae as strategy to improve their apparent digestibility coefficients in European seabass (Dicentrarchus labrax) juveniles

Algae are natural sources of nutrients, but the presence of anti-nutritional factors often compromises nutrient apparent digestibility coefficients (ADCs) in several fish species. In this study, physical-mechanical and enzymatic technological processing was applied to two seaweeds (Gracilaria gracilis and Ulva rigida) and three microalgae (Nannochloropsis oceanica, Chlorella vulgaris, and Tetraselmis sp.) in order to evaluate its effectiveness in improving nutrient ADC values in diets for European seabass. A practical commercial-based diet was used as reference (REF) and experimental diets were prepared by replacing 30% of REF diet with each test alga used either intact or after processing. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and fast performance liquid chromatography (FPLC) analyses revealed that enzymatic processing was more effective than the physical one in changing the protein and peptides composition, increasing the amount of low-molecular-weight compounds in seaweeds and N. oceanica microalgae. Protein digestibility was significantly affected by algae species and in the case of the microalgae by the technological process. Gracilaria gracilis is better digested than U. rigida and physical processing enhanced protein and energy ADC values. Nannochloropsis oceanica and C. vulgaris are better digested than Tetraselmis sp.; the highest protein and energy ADCs were observed in diets containing enzymatically processed N. oceanica (NAN-ENZ) and physically processed C. vulgaris (CHLO-PHY), followed by the diet with physically processed Tetraselmis sp. (TETR-PHY). Results clearly showed that it is possible to increase nutrient accessibility and digestibility of algae by fish, by selecting the most adequate method to disrupt the cell wall. Moreover, the physical-mechanical and enzymatic technological processes used in this study are scalable to the industrial level.

Assessment of a high protein distillers dried grain (HP-DDG) augmented with phytase in diets for European sea bass, Dicentrarchus labrax fingerlings on growth performance, haematological status, immune response and related gut and liver histology

Inclusion of high levels of plant protein ingredients in fish feeds induces the presence of undesirable compounds such as Anti-Nutritional Factors, including non-starch polysaccharides and phytates. The present study evaluated the effect of partial replacement of dietary soybean meal by a high protein distillers dried grains (HP-DDG) a co-product of corn based ethanol production. We evaluated HP-DDG in experimental diets with a supplemented commercial phytase on growth performance, physiological parameters and histological changes of the intestine and liver of European sea bass, Dicentrarchus labrax fingerlings. The experiment was conducted for six weeks. A total of 240 D. labrax fingerlings was randomly divided to four experimental treatments (each in triplicates groups) and fed to apparent satiation six days per week for a six weeks’ period. Four dietary treatments: containing 0, 30, 40 and 50% HP-DDG supplemented with enzyme phytase 0.5g kg-1 diet respectively, were tested. The results showed that growth performance and feed utilization efficiency of sea bass was significantly higher (P≤0.05) with increasing levels of HP-DDG-and phytase supplementation. Superior phosphorous utilization was also observed with respect to whole body retention for each incremental level of HP-DDG inclusion. Hematology and serum biochemistry (hemoglobin (Hb), red blood cells (RBCs), white blood cells (WBCs) and humoral immune parameters including total protein, globulin, cholesterol, lysozyme activity and total antioxidant capacity (TAC) were improved (P≤0.05) in fish fed diets with increased levels of HP-DDG and supplemented phytase. The findings suggest that the use of HP-DDG supplemented with phytase in sea bass diets enhanced growth, physiological and immunological responses, and evidenced a cost benefit advantage for European sea bass production compared to the use of a diet without either HP-DDG or phytase incorporation.

Dietary micronutrient supplementation in low fishmeal based diets for optimum growth and immune status of European sea bass (Dicentrarchus labrax) juveniles

The present study aimed to evaluate the optimal dietary micronutrient supplementation of plant-based diets for juvenile European sea bass. A 90-day feeding trial was performed, where fish were fed a high fishmeal (FM) based diet (62% DM; positive control) or low FM diets (12.5% FM and krill meal), supplemented with increasing levels of a micronutrient mixture (Nutrient Package, NP) consisting of vitamins, minerals and other micronutrients. The supplementation levels ranged from 0% (no supplementation, negative control) to 400%, where 100% supplementation level corresponded to the requirement levels recommended for other fish species. Fish growth and feed performance (SGR, DGI, FCR, PER) were significantly impaired at levels NP0 and NP25 compared to the FM control. Body Fe and Zn concentrations were positively affected by the graded levels of the NP, while Mn and Se concentrations remained stable. Growth parameters were particularly correlated to body Fe and Zn, while immune parameters were mainly correlated to body Zn. Significant immunosuppression was evidenced (concerning the respiratory burst activity) when low FM diets were not supplemented with NP. High inclusion levels of the NP showed a negative impact on lysozyme activity. Histological examinations did not reveal any significant effects on gills, gut and liver morphology. At identical NP supplementation level (50%), fish fed low and high FM diets showed similar growth and innate immunity suggesting that long-term feeding with plant-based diets do not significantly affect the fish when adequate minerals and vitamins supplementation is provided. Quadratic regression analysis showed that the inclusion of the NP between 260 and 300% improves growth and immune parameters of fish fed low-FM diets as well as Zn body incorporation. Overall, the present study suggested the positive impact of NP supplementation of PM-based diets on both fish growth and health but future NP could include less Mn, more Fe, closer to levels obtained in fish fed FM (245 mg·kg−1), and Zn at 122 mg·kg−1.

Exploring the potential of seaweed Gracilaria gracilis and microalga Nannochloropsis oceanica, single or blended, as natural dietary ingredients for European seabass Dicentrarchus labrax

Gracilaria gracilis and Nannochloropsis oceanica, single or blended, were tested in European seabass (Dicentrarchus labrax) diets. A control (CTRL) diet was compared with experimental diets including either 8% G. gracilis (GRA8), 8% N. oceanica (NAN8), or a blend of 4% of each alga (NAN4GRA4). After 106 days of feeding, growth, nutrient utilization, antioxidant defense, immunological status, and end-product quality were evaluated. All fish exhibited similar feed intake (1.4–1.5%), body weight, growth, and feed conversion ratio (1.6). Dietary inclusion N. oceanica did not affect digestible N intake and gain. Fish fed GRA8 had the lowest digestible N and energy intake (P < 0.05), and simultaneously the highest nitrogen retention efficiency and energy retention efficiency, resulting in a N and energy gain similar to all other treatments. All fish had well-preserved intestinal morphology; feeding NAN8 resulted in a significant increase in neutral goblet cells compared with GRA8. Fish fed the algal diets had significantly lower (P < 0.05) hepatosomatic index (1.7–1.8 vs 2.1) and plasma triglyceride levels than CTRL, but whole body composition remained similar among treatments. The liver total antioxidant capacity of fish fed NAN8 was significantly higher than that of fish fed GRA8 but did not differ significantly from the CTRL group. NAN4GRA4 resulted in lower values of total glutathione, glutathione peroxidase, and alternative complement. N. oceanica decreased fillet springiness; however, with NAN4GRA4, the muscle fillet became less resilient. G. gracilis and N. oceanica biomass, either used single (8%) or blended (4% each), can be valuable natural ingredients for partial replacement of fish meal in European seabass diets.

Prebiotics and phytogenics functional additives in low fish meal and fish oil based diets for European sea bass (Dicentrarchus labrax): Effects on stress and immune responses

The use of terrestrial raw materials to replace fish meal (FM) and fish oil (FO) in marine fish diets may affect fish growth performance and health. In the last years functional additives have been profiled as good candidates to reduce the effects on health and disease resistance derived from this replacement, via reinforcement of the fish immune system. In the present study, three isoenergetic and isonitrogenous diets with low FM and FO (10% and 6% respectively) were tested based on supplementation either with 0.5% galactomannanoligosaccharides (GMOS diet) or 0.02% of a mixture of essential oils (PHYTO diet), a non-supplemented diet was defined as a control diet. Fish were fed the experimental diets in triplicate for 9 weeks and then they were subjected to a stress by confinement as a single challenge (C treatment) or combined with an experimental intestinal infection with Vibrio anguillarum (CI treatment). Along the challenge test, selected stress and immunological parameters were evaluated at 2, 24 and 168h after C or CI challenges. As stress indicators, circulating plasma cortisol and glucose concentrations were analyzed as well as the relative gene expression of cyp11b hydroxylase, hypoxia inducible factor, steroidogenic acute regulatory protein, heat shock protein 70 and heat shock protein 90 (cyp11b, hif-1α, StAR, hsp70 and hsp90). As immune markers, serum and skin mucus lysozyme, bactericidal and peroxidase activities were measured, as well as gene expression of Caspase-3 (casp-3) and interleukin 1β (il-1ß).The use of functional additives induced a significant (p < 0.05) reduction of circulating plasma cortisol concentration when confinement was the unique challenge test applied. Supplementation of PHYTO induced a down-regulation of cyp11b, hif-1α, casp-3 and il-1β gene expression 2h after stress test, whereas StAR expression was significantly (p < 0.05) up-regulated. However, when combination of confinement stress and infection was applied (CI treatment), the use of PHYTO significantly (p < 0.05) down-regulated StAR and casp-3 gene expression 2h after challenge test, denoting that PHYTO diet reinforced fish capacity of stress response via protection of head kidney leucocytes from stress-related apoptotic processes, with lower caspase-3 gene expression and a higher il-1β gene expression when an infection occurs. Additionally, dietary supplementation with GMOS and PHYTO compounds increased fish serum lysozyme after infection. Both functional additives entailed a better capability of the animals to cope with infection in European sea bass when fed low FM and FO diets.

Bioconversion of fish-wastes biomass into a fish meal alternate for European seabass (Dicentrarchus labrax) diets

The effect of replacing fish meal (FM) in juvenile European seabass (Dicentrarchus labrax) diets with fish wastes (FW) and fermented FW (FFW) by marine fungus Beauveria bassiana was investigated. Seven diets were prepared: control (CTRL) and six diets containing either FW or FFW to substitute FM at 15, 30 and 45% (FW15/FFW15, FW30/FFW30 and FW45/FFW45 each in turn). Fish (initial weight Ca. 30 g) were reared for 90 days in 21 PVC tanks (3 m3) and fed to apparent visual satiation. The recorded values for growth, feed utilization efficiency, survival rate and amino acids composition of fish fed either FW or FFW diets, at all tested levels, are not significantly different relative to those values of control group. Carcass protein content was not influenced by diet, but lipid content of FW45 and FFW45-fed fish showed a significant elevation relative to that of other fish groups. Blood parameters indicate an improvement in general health status and both liver and kidney function of FW-fed fish up to 30% FM replacement level, relative to those of CTRL and FFW-fish. Fish fed the FW-diets showed higher fungal and acid fermentative bacterial counts and lower count of Vibrio spp. and coliform, suggesting better gut health as compared to FFW-fed fish. These results indicate that 30% of dietary FM can be replaced with FW meal without adverse effects on fish growth performance, feed utilization, general health status or intestinal microbiome and fermentation with B. bassiana has some negative influence on gut integrity at 45% FM substitution level.

Anchovy and giant squid hydrolysates can enhance growth and the immune response of European seabass (Dicentrarchus labrax) fed plant-protein-based diets

The aim of the present study was to evaluate: 1) the in vitro bactericidal and bacteriostatic activities of four selected marine hydrolysates, from anchovy or giant squid, against several fish pathogens, and 2) if the inclusion of 3% of those hydrolysates in a plant-protein-based diet could result in similar growth, feed efficiency, humoral immune status and haematological parameters of juvenile European seabass (Dicentrarchus labrax), compared to a fish meal-based diet, during an in vivo trial. Four marine hydrolysates from anchovy (ANC) or giant squid (GS) were obtained by hydrolysis using either a single protease (P1, endopeptidase activity; or P2, endo - and exopeptidase activities) or a mixture of P1 and P2 (MIX). Bactericidal and bacteriostatic activities of each hydrolysates were evaluated in vitro against several fish pathogens. Afterwards, four experimental diets with ANC (ANC-P1 and ANC-P2) or GS (GS-MIX and GS-P2) hydrolysates, a positive control (PC) diet with a higher content of a fishmeal (25%), and a negative control (NC) diet, where 50% of fishmeal of PC diet was replaced by plant sources, were formulated for an in vivo trial. Diets were fed to triplicate groups of juvenile European seabass (7.0 ± 2.0 g) distributed into tanks of 250 L each, at a density of 3.7 kg m−3, for 60 days. At the end of the in vivo trial, growth performance, nutrient utilization, whole body composition and humoral immune status of fish were evaluated.The in vitro trial showed that all marine hydrolysates conferred resistance against fish pathogens, as they had bactericidal and bacteriostatic activities against a great number of bacteria belonging to the Vibrionaceae family. However, GS hydrolysed by a single peptidase (P2) resulted in a lower bactericidal activity (P < .050) against Vibrio harveyi than the others hydrolysates. During the in vivo trial, fish fed ANC-P1, ANC-P2 and GS-MIX diets had similar (P > .050) growth compared to fish fed PC diet, whereas fish fed GS-P2 had lower (P ≤ .001) final body weight and specific growth rate than fish fed PC. However, the experimental diets barely affected innate immunity. These results showed that the 3% inclusion of ANC and GS hydrolysates, mainly ANC hydrolysed by a single protease with both endo - and exopeptidase activities (P2) or GS hydrolysed by a protease mix (MIX), in plant-protein-based diets for juvenile European seabass could be good options to hamper the negative effects caused by plant ingredients.

Effects of black soldier fly (Hermetia illucens L.) larvae meal on growth performance, organs-somatic indices, body composition, and hemato-biochemical variables of European sea bass, Dicentrarchus labrax

Fishmeal (FM) is one of the major protein sources used in fish diets, which was obtained from wild fish catches. Due to the steady decline in fish catches accompanied with the increased demands for aquafeeds, a rapid decrease in the FM availability is much more expected. Alternative protein sources of animal origins, such as dried black soldier fly (Hermetia illucens L.) larvae meal (DBSFLM), may be used as an alternative protein source instead of FM in aquafeeds. Therefore, a feeding trial was carried out to evaluate the effects of partial replacement of FM with DBSFLM on growth performance and body composition of European sea bass, Dicentrarchus labrax. A basal diet (45% crude protein) was formulated, where DBSFLM protein replaced 25, 35, or 50% of FM protein. Fish (12.1 ± 0.21 g) were fed one of the tested diets up to apparent satiation thrice a day for 8 weeks. No significant differences were observed in fish growth, feed utilization, and survival (P > .05). The DBSFLM inclusion in diets of European sea bass did not affect its body constituents. Additionally, values of red blood cells, hemoglobin, hematocrit, mean corpuscular volume, and mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration were not significantly influenced by DBSFLM inclusion in fish diets as compared to the FM-control fish. Likewise, no significant changes were observed in counts of white blood cells, lymphocytes, monocytes, and neutrophils in DBSFLM-fed fish as compared to the FM-control fish. The DBSFLM inclusion in diets for European sea bass did not affect levels of serum total protein, albumin, globulin, serum alanine aminotransferase, and aspartate aminotransferase. The simple economic analysis evoked that feed cost decreased with increasing DBSFLM levels in fish diets. The findings of the present study elucidated that the growth performance was not significantly changed by partial replacement of FM protein up to 50% by DBSFLM protein, which reduced the feeding cost by 15.6% as compared with the FM-control diet.

Evaluation of co-fermented apple-pomace, molasses and formic acid generated sardine based fish silages as fishmeal substitutes in diets for juvenile European sea bass (Dicentrachus labrax) production

Due to a need to address the potential of converting overfished sardines in North Africa and Middle East into a stable product, whole sardines were ensiled using different methods, and subsequently tested in a feeding trial and sequential digestibility assessment performed on sea bass, an important farmed fish of this region.Four isonitrogenous and isocaloric experimental diets were formulated for juvenile European sea bass replacing the fish meal protein component of a control diet with an apple pomace fermented fish silage (APFS); molasses fish silage (MFS) and formic acid silages (FAFS). Feeding sea bass with fish silage based diets generated similar or lower growth performance, feed utilization, protein efficiency and retention compared to the fish meal based diet. Hematological parameters were also measured at the end of the feeding trial. However, a significant difference (P < .05) was observed between the FAFS fed group and fermented fish silage treatments except for the APFS group with respect to leukocyte levels. Formic acid silage fed sea bass, showed more complicated mucosal fold features with greater depth, regularity and overall surface area (gut perimeter ratio) being significantly different (P < .05) compared to the control group. The apple pomace silage resulted in fish having the lower gut perimeter ratio.Scanning electron micrographs (SEM) of the distal intestine revealed that sea bass fed with all experimental diets showed no evidence of mucosal epithelial damage with all fish having healthy and regular shaped enterocytes lining the posterior intestine.However the microvilli gut enterocyte layer of sea bass fed apple pomace fish silage appeared thinner compared to all other treatment groups of sea bass. The study showed no evidence of any impaired general hematological changes indicative of health status of sea bass at the end of the trial period.In a consecutive digestibility evaluation, the apparent digestibility coefficient of dry matter (ADCdry matter) of the experimental diets was found to be relatively lower than the control group. However, the apparent digestibility coefficients for protein (ADCprotein) and energy (ADCenergy) were deemed acceptable for all silages tested.The overall findings of this study indicate that fish silage produced from organic acids or by fermentation with carbohydrate sources and lactic acid bacteria were an effective partial replacement of fish meal in aquaculture feeds. We show that this has potential for applications in diet formulations for European sea bass being an important farmed Mediterranean marine species.

Assessment of sesame meal as a soybean meal replacement in European sea bass (Dicentrarchus labrax) diets based on aspects of growth, amino acid profiles, haematology, intestinal and hepatic integrity and macroelement contents.

An 87-day feeding trial was carried out to assess the use of dehulled and defatted sesame seed meal (SM) as a partial dietary replacement for soybean meal (SBM) at 0%, 15%, 30% and 45% (SM0, SM1, SM2 and SM3, respectively) in juvenile sea bass stocked in 12 tanks (0.5m3) and with an initial weight of 24 ± 0.50g. All diets were isonitrogenous (~ 47% crude protein), isoenergetic (~ 22MJ/kg) and tested in triplicate. The lowest growth and feed utilization efficacy were detected in fish fed the SM3 diet; moreover, diets with a lower SM content did not have significant effects relative to the CTR diet. Fish biochemical analysis indicated a gradual decrease in carcass protein content coinciding with an increase in lipid deposition and viscerosomatic index values as the SM level in the diet increased. The macroelements' (P, Na and K) fish contents did not differ significantly among groups. The SM3 group had the lowest Ca and highest Mg contents among the experimental groups. The fish amino acid profile indicated slight alterations in essential amino acid percentages among groups. Haematological analysis and serum biochemistry indicated that using SM at a content of up to 30% had limited negative impacts on fish health. Liver histological inspection indicated that higher levels of SM led to severe hepatocyte infiltration with slight signs of necrosis in fish fed SM3 diet. Intestinal histological examinations indicated that the distal portion of the intestine was the portion most affected by SBM replacement with SM with signs of intestinal inflammation in SM3 group.

Replacement of fishmeal with soybean meal for the diet of seabass, Lates calcarifer

Fishmeal is one of the essential raw materials in the fish diet, and this material is expensive and rarely available in the rural area. Therefore, the present study aimed to explore the possibility to replace the fishmeal with the soybean meal in the diet of Asian seabassLatescalcarifer. The study was conducted from November 2018 to January 2019 at Center for Brackish Water Aquaculture in Ujung Batee, Aceh Besar District, Indonesia. The completely randomized experimental design method was used in this study with six treatments and four replications. The tested treatment was the replacement proportion of fish meal with the soybean meal in the diet, namely: 0%, 20%, 40%, 60%, 80%, and 100%. The experimental fish were stocked at one fish per liter of seawater. The fish were fed on the experimental diet at feeding level of 10% body weight two times a day. The results showed that the proportion of the soybean meal in the diet gave the significant effect on the weight gain, specific growth rate, feeding conversion ratio and feed efficiency (P<0.05), but did not provide the considerable impact on the survival rate (P>0.05). In conclusion that approximately 40% of the fish meal can be replaced with soybean meal for Asian seabass diet.

European seabass (Dicentrarchus labrax) performance, health status, immune response and intestinal morphology after feeding a mixture of plant proteins-containing diets

The feasibility of reducing the fish meal (FM) content, as much as possible, in juvenile seabass diets by using a combination of four plant nutrients (plant mix, PX): soybean meal, SBM; soyprotein concentrate, SPC; corn gluten, CG and maize flour, MF was investigated . Seabass (mean initial body weight, 4.74±0.04 g) were fed with one of four isonitrogenous and isolipidic diets formulated to progressively reduce FM concentration of control diet (CTRL), by incorporation the PX, to be 30% (FM30 diet), 25% (FM25 diet), and 20% (FM20 diet) over a 13-week growth period. Fish were fed the experimental diets in triplicate and the resulting effects on growth performance, nutrient utilization, biochemical and amino acid composition, major blood constituents, immunity indicators and intestinal histology were evaluated. At the end of the trial, the FM25-fed fish presented growth, feed utilization, and survival rates comparable (P>0.05) to the CTRL fish. In addition, this diet did not negatively influenced major blood constituents, immunity indicators or intestinal histomorphology. Further dietary FM reduction to 20% (FM20 diet) and elevation of PX inclusion level (~ 59%) have caused a significant (P<0.05)decline in final fish weight, haemoglobin, erythrocyte, leukocyte and lymphocyte counts, elevated leukocytes phagocytic-activityand caused some abnormalities in the proximal intestine (PI) morphological features, but did not negatively impacted haematocrit value, mean erythrocyte cell volume (MCV), mean cellular haemoglobin content (MCH), mean cell haemoglobin concentration (MCHC), monocytes, eosinophils, serum total protein and lysozyme activity. Based on these results, the FM25 formulation (containing approximately 54% PX) can be considered the appropriate for reducing dietary FM down to 25% without compromising the performance, health, immunity or PI morphology of juveniles’ seabass.

Protective Effect of Dietary Taurine from ROS Production in European Seabass under Conditions of Forced Swimming.

Simple SummaryA number of recent studies have demonstrated the essentiality of dietary taurine in many commercially relevant cultured fish species. Taurine is involved in many physiological functions in fish and represents an essential nutrient, which exert powerful antioxidant properties and is required as a supplement in the feed when a relevant percentage of vegetable protein sources are utilized. Our results show that dietary taurine can reduce the oxidative status of marine fish under swim stamina stress conditions. These data could be essential for the development of diets with fishmeal/soybean meal substitutions in the effort to improve the sustainability of the aquaculture.Taurine (Tau) is an amino sulfonic acid, which is widely distributed in animal tissues, whereas it is almost lacking in plants with the exception of certain algae, seaweeds, and few others. In the aquafeed industry, Tau is mainly used as a feed additive to promote growth in marine fish species with limited cysteine sulfinate decarboxylase activity. In particular, Tau supplementation is required in feeds in which fishmeal (FM) is substituted with high percentages of plant-derived protein sources such as soybean meals (SBM) that have much lower levels of Tau than FM. In addition to being a growth promoter, Tau exert powerful antioxidant properties being a scavenger of the reactive oxygen species (ROS). Under sustained swimming conditions, an intracellular increase in ROS production can occur in fish red muscle where the abundance of mitochondria (the main site of ROS formation) is high. Accordingly, this study aimed at investigating the effects of dietary Tau on European seabass (Dicentrarchus labrax) growth and oxidative stress response induced by swimming exercise. Individually tagged fish of 92.57 ± 20.33 g mean initial weight were fed two experimental diets containing the same low percentage of FM and high percentage of SBM. One diet was supplemented with 1.5% of Tau. Tau supplemented in the diet had a positive effect on fish growth, and enhanced swimming performance and antioxidant status. Two swim endurance tests were performed during the feeding trial. Metabolic oxygen consumption (MO2) was measured during exercise at incremental swimming speeds (0.7, 1.4, 2.1, 2.8, 3.5, and then 4.2 BL (body length) s−1, until fatigue). Fish maximal sustainable swimming speed (Ucrit) was determined too. To investigate the antioxidant effect of dietary Tau, we also measured ROS production in fish blood by RBA (respiratory burst activity) assay and quantified the expression of genes coding for antioxidant enzymes by qPCR (quantitative polymerase chain reaction) , such as SOD (superoxide dismutase), GPX (glutathione peroxidase), and CAT (catalase) in red muscle and liver. There was a significant effect of Tau upon Ucrit during exercise. Additionally, ROS production was significantly lower in fish fed with Tau supplemented diet, supporting the role of Tau as ROS scavenger. The protective effect of Tau against oxidative stress induced by forced swimming was denoted also by a significant decrease in antioxidant enzymes gene expression in fish liver and muscle. Taken together these results demonstrate that Tau is beneficial in low FM-based diets for seabass.

Functional additives in low fish meal and fish oil based diets for European sea bass (Dicentrarchus labrax): Effects on immune response, stress and disease resistance

Functional additives in low fish meal and fish oil based diets for European sea bass (Dicentrarchus labrax): Effects on immune response, stress and disease resistance

Wheat germ as an alternative ingredient to a fair average quality fishmeal in diets for European seabass

Wheat germ as an alternative ingredient to a fair average quality fishmeal in diets for European seabass

Dietary N-Carbamylglutamate (NCG) alleviates liver metabolic disease and hepatocyte apoptosis by suppressing ERK1/2-mTOR-S6K1 signal pathway via promoting endogenous arginine synthesis in Japanese seabass (Lateolabrax japonicus)

N-Carbamylglutamate (NCG), an analogue of N-acetylglutamate (NAG), can promote the synthesis of endogenous Arginine (Arg) in mammals, but not well studied in fish. This study was conducted to investigate the capacity of Arg endogenous synthesis by NCG, and the effects of various dietary NCG doses on growth performance, hepatic health and underlying nutrient regulation metabolism on ERK1/2-mTOR-S6K1 signaling pathway in Japanese seabass (Lateolabrax japonicus). Four experimental diets were prepared with NCG supplement levels of 0 (N0), 360 (N360), 720 (N720) and 3600 (N3600) mg/kg, in which N360 was at the maximum recommended level authorized by MOA, China in fish feed, and the N720 and N3600 levels were 2 and 10-fold of N360, respectively. Each diet was fed to 6 replicates with 30 Japanese seabass (initial body weight, IBW = 11.67 ± 0.02 g) in each tank. The results showed that the dietary NCG supplementation had no significant effects on the SGR and morphometric parameters of Japanese seabass, but 360–720 mg/kg NCG inclusion promoted PPV, while the 10-fold (3600 mg/kg) overdose of NCG had remarkably negative effects with significantly reduced feed efficiency, PPV and LPV. We found that Japanese seabass can utilize 360–720 mg/kg NCG to synthesis Arg to improve the amino acid metabolism by increasing plasma Arg and up-regulating intestinal ASL gene expression. Increased plasma GST and decreased MDA indicated the improved antioxidant response. Dietary NCG inclusion decreased plasma IgM and down-regulated the mRNA levels of inflammation (TNF-α and IL8), apoptosis (caspase family) and fibrosis (TGF-β1) related genes in the liver. The immunofluorescence examination revealed significantly decreased hepatic apoptosis and necrosis signals in the NCG groups. The ameliorated liver function and histological structure were closely related to the improved lipid metabolism parameters with decreased plasma VLDL and hepatic TG and NEFA accumulation, down-regulated fatty acid and cholesterol synthesis and simultaneously increased lipolysis gene mRNA levels, which regulated by inhibiting phosphorylation of ERK1/2-mTOR-S6K1 signaling pathway. Consuming 3600 mg/kg of dietary NCG is not safe for Japanese seabass culturing with the significantly increased FCR and decreased protein and lipid retention, and reduced plasma ALB. Accordingly, the observed efficacy and safety level of dietary NCG in the diet of Japanese seabass is 720 mg/kg.

Mixed culture purple phototrophic bacteria is an effective fishmeal replacement in aquaculture

Aquaculture is the fastest growing animal food production industry, now producing 50% of all food fish. However, aquaculture feeds remain dependent on fishmeal derived from capture fisheries, which must be reduced for continued sustainable growth. Purple phototrophic bacteria (PPB) efficiently yield biomass from wastewater with high product homogeneity, a relatively high protein fraction, and potential added value as an ingredient for fish feeds. Here we test bulk replacement of fishmeal with PPB microbial biomass in diets for Asian sea bass (Lates calcarifer), a high value carnivorous fish with high protein to energy requirement. Mixed culture PPB were grown in a novel 1 m3 attached photo-biofilm process using synthetic and real wastewater. Four experimental diets were formulated to commercial specifications but with the fishmeal substituted (0%, 33%, 66%, and 100%) with the synthetic grown PPB biomass and fed to a cohort of 540 juvenile fish divided amongst 12 tanks over 47 days. Weight and standard length were taken from individual fish at 18, 28, and 47d. No significant difference in survival was observed due to diet or other factors (94–100%). There was a negative correlation between PPB inclusion level and final weight (p = 5.94 × 10−5) with diet accounting for 4.1% of the variance over the trial (general linear model, R2 = 0.96, p = 1 × 10−6). Feed conversion ratio was also significantly influenced by diet (p = 6 × 10−7) with this factor accounting for 89% of variance. Specifically, feed conversion ratio (FCR) rose to 1.5 for the 100% replacement diet during the last sample period, approximately 1.0 for the partial replacement, and 0.8 for the nil replacement diet. However, this study demonstrates that bulk replacement of fishmeal by PPB is feasible, and commercially viable at 33% and 66% replacement.

Evaluation of defatted black soldier fly (Hermetia illucens L.) larvae meal as an alternative protein ingredient for juvenile Japanese seabass (Lateolabrax japonicus) diets

Defatted black soldier fly larvae meal (DBSFLM) has been shown a promising fish meal (FM) substitute in diets for turbot, rainbow trout, Jian carp, Pacific white shrimp and Atlantic salmon, but it has not been examined as an alternative protein source in Japanese seabass (Lateolabrax japonicus) diets. A 56-day feeding trial was conducted to assess the effects of partial replacement of dietary FM with DBSFLM on the growth performance, whole body composition, blood metabolites, digestive enzyme activities, hepatic and intestinal histomorphology, and lipid metabolism related genes expression of juvenile L. japonicus. Five isoproteic (39%) and isolipidic (11%) diets were formulated by replacing 0% (FM), 16% (DBSFLM16), 32% (DBSFLM32), 48% (DBSFLM48) and 64% (DBSFLM64) of fish meal. Each diet was randomly assigned to triplicate groups of 30 fish per tank. Fish were fed two times daily to apparent satiation. Results showed that growth performance, somatic indexes, hepatic and intestinal histomorphology, and the intestinal antioxidant and immunity indexes of fish were not affected (P > 0.05) by dietary treatments. Fish consuming DBSFLM48 and DBSFLM64 had higher (P < 0.05) feed intake, but lower (P < 0.05) whole body ash content and ash retention along with serum concentrations of total cholesterol, triacylglycerol, high density lipoprotein cholesterol and malondialdehyde than those fed FM. DBSFLM inclusion did not alter activities of hepatic trypsin, lipase and amylase, but increased (P < 0.05) activity of intestinal lipase for fish fed DBSFLM48 and DBSFLM64 than those fed FM. Relative genes expression were up-regulated (P < 0.05) in hepatic lipoprotein lipase for fish fed DBSFLM64 and in hormone sensitive lipase for fish fed DBSFLM32, DBSFLM48 and DBSFLM64, whereas down-regulated (P < 0.05) in fatty acid synthase for fish fed DBSFLM diets than those fed FM. It was concluded that the replacement of dietary FM with DBSFLM up to 64% level did not alter growth performance, hepatic and intestinal histomorphology of L. japonicus. The increased feed intake, reduced blood lipid and inhibited hepatic lipid deposition suggest that DBSFLM can be a desirable protein alternative source as a replacement of fish meal in L. japonicus diets.

Appraisal of a high protein distiller’s dried grain (DDG) in diets for European sea bass,Dicentrarchus labraxfingerlings on growth performance, haematological status and related gut histology

High protein distiller's dried grains (HP‐DDG) are co‐products of ethanol production that uses prefractionation technology. An 8‐week growth trial was conducted to investigate the effect of partial replacement of soybean meal (SBM) by three levels of HP‐DDG (30%, 40% and 50%) on growth performance, physiological parameters and histological changes of the intestine of European sea bass, Dicentrarchus labrax. The results indicated that an increased dietary level of HP‐DDG of more than 30% significantly increases growth performance and improved the FCR of sea bass. In addition, replacement of SBM by HP‐DDG enhanced feed intake efficiency and the health status of fish. Haematology and serum biochemistry (haemoglobin (Hb), red blood cells (RBCs), white blood cells (WBCs), packed cell volume (PCV %) and humeral immune parameters including total protein, albumin, globulin, cholesterol, lysozyme activity and total antioxidant capacity significantly increased with increase HP‐DDG inclusion levels. The findings of this study indicated that HP‐DDG is a good complementary protein source for inclusion aquaculture diets and levels above 30% as a replacement of SBM did not compromise growth performance and physiological parameters of sea bass while enhancing some important indices of health status in this species.