Diets For Turbot Research Articles

Beyond fish oil: Assessing the implications of alternative dietary lipid sources for turbot (Scophthalmus maximus) on growth, nutrient utilization and muscle quality

Various combinations of alternative marine lipid sources were evaluated for their potential to replace commercially available fish oil, specifically sardine oil (SO), in turbot (Scophthalmus maximus). A commercially based diet was used as a control (CTRL) containing sardine oil (7.0%) and rapeseed oil (RO; 3.8%) as the main lipid sources, providing 1.9% EPA + DHA. A positive control (SARDINE) was also included, which used SO as the sole lipid source to provide 2.6% EPA + DHA. Two other diets were formulated to target approximately the same levels of EPA + DHA as the positive control: ALGA (2.7% algae oil, 5.4% SO, and 2.7% RO), and ALGAMIX (a blend of 2.0% micro and macro algae biomass, 9.5% SO, and 0.7% salmon oil, a by-product of the salmon industry). SO was completely replaced in two alternative diets, ALT1 and ALT2, by different ratios of salmon and algae oils: 8.0/2.9 and 6.0/4.9%, providing 2.0% and 2.8% EPA + DHA, respectively. In these alternative diets, 30% of the fish meal was also replaced, by Tenebrio molitor meal and a single-cell protein concentrate from Corynebacterium glutamicum. After 75 days of feeding, all diets were equally well-accepted by the fish, and no significant differences were found in feed efficiency, growth performance, and somatic indexes. All fish had similar muscle EPA + DHA values, but only the ALGAMIX group exceeded the European Food Safety Authority (EFSA) recommended EPA + DHA levels for human daily consumption. Hepatic lipogenesis was decreased in fish fed with higher levels of EPA + DHA, suggesting that increased n-3 LC-PUFA negatively affects lipid metabolism. Additionally, the mixture of algae oil, sardine oil, and rapeseed oil (ALGA diet) showed potential for improving muscle antioxidant capacity. Overall, this study showed that combining expensive sources of n-3 long-chain polyunsaturated fatty acids (LC-PUFA) with less expensive oils, such as salmon by-product oil or vegetable oils, may be a viable cost-efficient strategy for replacing SO in diets for turbot. This can be achieved without compromising growth and while ensuring high flesh n-3 LC-PUFA content and improving its antioxidant potential.

Fish oil replacement by beef tallow in juvenile turbot diets: Effects on growth performance, body composition and volatile flavor compounds in the muscle

A 12-week feeding trial was conducted to evaluate the effects of dietary fish oil (FO) replacement by beef tallow (BT) on the growth performance and body composition of juvenile turbot (average initial weight, 19.6 g). The control diet contained 6% added FO (of dry matter, Diet FO-C). Beef tallow was supplemented into Diet FO-C, replacing added FO at different levels, i.e., 25%, 50%, 75%, and 100%, formulating the other 4 experimental diets, designated as 25BT, 50BT, 75BT, and 100BT, respectively. The feeding trial was conducted in a flow-through seawater system. Each diet was randomly fed to triplicate tanks (30 fish in each tank). The results showed that a cubic regression relationship was observed between weight gain and dietary FO replacement level. Although total FO replacement by BT significantly reduced the growth of juvenile turbot, no significant difference was observed between FO-C and 75BT. Diet BT decreased the whole-body crude lipid content but increased the whole-body moisture and ash contents. Dietary BT regulated the proximate composition of fish tissues in a dose dependent manner. High dietary BT levels did not reduce the n-3 long-chain polyunsaturated fatty acid content (% total fatty acid) in the muscle. Partial FO replacement (25 and 50%) by BT even significantly increased the muscle DHA content. The fatty acid composition of the liver, subcutaneous adipose tissue around the fin, and intestine generally reflected those of the diets. No significant difference was observed in muscle and liver mitochondrial DNA copy number among groups, indicating the similar general energy supply status. Dietary BT significantly reduced the concentration of triacylglycerol, cholesterol and malondialdehyde in the serum. The volatile flavor compound in muscle was analyzed with gas chromatography-ion migration spectrometry (GC-IMS). Dietary BT resulted in lower number and abundance of flavor aldehydes and alcohols in the muscle. In conclusion, beef tallow can replace 75% added fish oil (appr. 45% of total fish oil including the residual fish oil in fishmeal) in the diets of turbot, without reducing fish growth. Dietary beef tallow significantly affected the body composition and volatile flavor compound composition in the muscle.

Comparison of the performance of raw and Lactobacillus paracasei fermented soybean meal in diets for turbot (Scophthalmus maximus L.): Growth, intestinal morphology, apoptosis, tight junction, and microbiota

Fermentation is a promising method to improve the utilization of soybean meal (SM) by fish, and strain is the core of fermentation process. In this study, the effects of Lactobacillus paracasei fermentation on the SM quality were investigated. Also, an 8-week feeding trial was conducted to compare the performance of SM and L. paracasei fermented SM (LPFSM) in diets for turbot. Juvenile turbots (13.50 ± 0.13 g) were randomly divided into nine treatments fed on diets with 0% (FM, control), 15% (S15/L15), 30% (S30/L30), 45% (S45/L45), and 60% (S60/L60) of fishmeal protein replaced by SM or LPFSM respectively. The results showed that fermentation remarkably increased the lactic acid and decreased the anti-nutritional factors in SM. Furthermore, fishmeal could be replaced by SM up to 30% or by LPFSM up to 45% based on the growth performance. Typical groups (FM, S45, and L45) with significant differences in growth were selected for further analysis. Reduced villus height and widened lamina propria were observed in the S45 group, while no significant pathological symptom was found in the L45 group. The mRNA levels of the apoptosis-related genes (bax, p53, and caspase3) and tight junction-related gene (tricellulin) in the S45 group were significantly up-regulated or down-regulated, respectively, while the L45 group remained similar to the FM group. The mRNA levels of tight junction-related genes (zo-1 and occludin) were significantly down-regulated in both S45 and L45 groups compared to the FM group. Furthermore, dietary LPFSM modified the intestinal microbiota by regulating the dominant bacterial phyla (Proteobacteria, Firmicutes, and Actinobacteria) and genera (Cobetia, Pseudomonas, and Lactobacillus), and making the overall microbiota profile more coherent with FM-fed fish. Collectively, L. paracasei fermentation significantly improved the SM quality, and fishmeal could be replaced by LPFSM up to 45% without adverse effects on growth and intestinal health of turbot.

Effects of tributyrin supplemented in a high-soybean meal diet on the growth performance and intestinal histopathology of juvenile Scophthal musmaximus L.

This study was conducted to evaluate the influence of tributyrin (TB) supplemented in diet on the growth, feed utilization and intestinal health of turbot (Scophthalmus maximus L.). Four experimental diets were formulated with TB at 0 mg/kg, 100 mg/kg, 200 mg/kg and 300 mg/kg levels respectively. A total of 2016 turbot (initial body weight: 31.22±0.05g) were randomly distributed into 12 tanks and fed the corresponding diets for 70d. Results showed that fish in 100 mg/kg group had significantly higher weight gain rate (WGR) and specific growth rate (SGR) than that in other groups (P<0.05). No significant differences were observed in survival rate (SR), feeding rate (FR), feed conversion ratio (FCR), condition factor (CF), hepatosomatic index (HSI), and viscerosomatic index (VSI) among all groups (P>0.05). There was no significant difference in intestinal superoxide dismutase (SOD) activities and intestinal malonaldehyde (MDA) contents among all treatments (P>0.05), while the highest SOD activity and the lowest MDA content were found in 100 mg/kg group. The height of intestinal fold in 100 mg/kg treatment was significantly higher than that in other groups (P<0.05). However, no significant difference existed in intestinal wall thickness among all groups (P>0.05). The present study suggested that 100 mg/kg TB inclusion level was recommended in the diets of turbot to promote the growth and improve the intestinal morphology structure and health in turbot.

Impact of graded dietary fumonisin contamination levels on the growth performance and selected health indices of turbot (Psetta maxima)

ABSTRACT A common problem that arises from the use of plant ingredients is the presence of mycotoxins. The plant meals with more potential to be used in turbot diets have a natural tendency to be contaminated by fumonisins (FUM). Psetta maxima fed: FUM 1.0, FUM 2.0 and FUM 5.0 mg kg−1 diets showed a significantly lower final mean body weight, specific growth rate and protein efficiency ratio, and a concomitantly higher feed conversion ratio, than those fed the Control or FUM 0.5 diet. At dietary concentrations of 1 to 5 mg kg−1, FUMs caused a reduction of the brush border villi length in the distal intestine and a reduction of hepatic lipid inclusion. In conclusion, dietary FUM contamination over the course of 63 days, lead to significant damaging effects on the overall growth performance, nutrient retention, organ morphology and immune status of turbot.

Fish protein hydrolysate in diets of turbot affects muscle fibre morphometry, and the expression of muscle growth‐related genes

Fish protein hydrolysate in diets of turbot affects muscle fibre morphometry, and the expression of muscle growth‐related genes

Effects of dietary organic trace mineral mixture levels on survival, growth performance, body composition and antioxidant capacity of juvenile turbot ( Scophthalmus maximus )

A 70-day feeding trial was conducted to investigate effects of dietary organic trace mineral (OTM) mixture levels on survival, growth performance, body composition and antioxidant capacity of juvenile turbot (Scophthalmus maximus). The commercial diet with 0.03% inorganic trace mineral (ITM) premix was used as the control, and other four experimental isonitrogenous (50% crude protein) and isolipidic (12% crude lipid) diets were formulated to contain 0.0375%, 0.075%, 0.1125% and 0.15% OTM mixture respectively. Results showed that there were no significant differences in survival among dietary treatments. However, the growth was not significantly different between the control and OTM supplementation diets. Especially, turbot fed the diet with 0.075% OTM had significantly higher specific growth rate than 0.15%, 0.1125% and 0.0375% OTM treatments (p < .05). Moisture, crude protein, crude lipid and ash of the whole fish body showed no significant differences among dietary treatments. Activities of superoxide dismutase in serum of turbot fed diets with 0.1125% and 0.15% OTM were significantly higher than 0.0375% OTM treatment (p < .05). Activities of total antioxidant capacity and catalase in serum were the highest, while the malondialdehyde content was the lowest when the turbot were fed the diet with 0.075% OTM. In summary, results of the present study suggested that the supplementation of 0.0375% or more OTM in diets could obtain similar performance to the commercial diet with ITM premix, and the optimal amount of OTM supplementation in diets of turbot was approximately 0.075% on basis of growth performance and antioxidant capacity.

The effect of dietary cecropin AD on intestinal health, immune response and disease resistance of juvenile turbot (Scophthalmus maximus L.)

Cecropin AD (CAD) is a commercial cationic antimicrobial peptide that has been seldom studied in marine fish. This study investigated the effects of dietary CAD on intestinal health, immune response, disease resistance, and growth performance of turbot. A diet using fishmeal and plant protein as the main protein resources was used as the control (crude protein 53%, crude lipid 12%). CAD was supplemented into the control diet at the level of 250, 500, 750, and 1000 mg kg−1 to formulate four experimental diets, C1, C2, C3, and C4, respectively. No significant difference was observed in fish growth performance, feed utilization efficiency and whole-body composition among all groups. Dietary CAD significantly increased the activity of lysozyme and complement component 3 level in both serum and distal intestine (DI), as well as the immunoglobulin M content in DI. The gene expression of immune cytokines such as IFN-γ, IL-1β, and chemokine SmCCL19, and the goblet cell number in DI were also significantly increased by dietary CAD supplementation. Compared with the control group, the microbiota analysis indicated group C4 showed significantly decreased α-diversity, obvious alternation in dominant bacteria composition at phylum level, different clustering, and significantly decreased relative abundance of Lactobacillus. Besides, the relative abundance of Bacteroides was significantly decreased in groups C1, C3, and C4. In addition, the lowest mortality of turbot challenged with Edwardsiella tarda was observed in fish fed diets C2 and C3. In conclusion, moderate levels of CAD in diet of turbot improved the intestinal immune response without disrupting the intestinal bacterial community, and enhanced the disease resistance. However, dietary CAD at 1000 mg kg−1 greatly affected the intestinal bacterial composition and showed potentially inhibitory effects towards Lactobacillus.

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.

Sodium butyrate supplementation in high-soybean meal diets for turbot (Scophthalmus maximus L.): Effects on inflammatory status, mucosal barriers and microbiota in the intestine

A 12-week feeding trial was conducted to evaluate the effects of dietary sodium butyrate (NaBT) on the intestinal health of juvenile turbot (Scophthalmus maximus L.), in terms of inflammatory status, mucosal barriers and microbiota. Three isonitrogenous and isolipidic practical diets were used: (1) fish meal based group (FM); (2) soybean meal group (SBM), soy protein replacing 40% fish meal protein in FM; (3) NaBT group, 0.2% NaBT supplemented in SBM. Each diet was fed to triplicate tanks (30 fish in each tank). The current results showed that 0.2% dietary NaBT improved the growth performance of fish and alleviated the enteropathy, increasing the absorptive surface and mitigating the infiltration of mixed leukocytes in lamina propria. Fish fed the NaBT diet presented increased activities of intestinal brush border enzyme and similar nutrient digestibility with the FM group. Compared to SBM, the inclusion of 0.2% NaBT in diet significantly up-regulated the intestinal gene expression of tight junction proteins and down-regulated the gene expression of TNF-α and NF-κB. The gut microbial communities of the NaBT group were closer to the FM group than to the SBM group, in terms of PCoA, UPGMA and Heatmap analyses based on weighted Unifrac distance. The relative abundance of several dominant bacteria at the phylum (Proteobacteria, Bacteroidetes, Deinococcus-Thermus and Actinobacteria) and genus level (Thermus, Acinetobacter, Bacteroides and Silanimonas) were altered by dietary NaBT. In conclusion, dietary NaBT had positive roles in protecting the intestinal health of turbot from the impairment of soybean meal.

Dietary replacement of fishmeal by corn distillers dried grains with solubles (DDGS) in diets for turbot (Scophthalmus maximus, Linneaus, 1758) Juveniles

The aim of this study was to determine the potential of corn distillers dried grain with solubles (DDGS) to partially replace fishmeal (FM) in practical diets for turbot. For that purpose, a control diet was formulated to include 40% FM and a mixture of plant protein ingredients (soybean meal, corn gluten, and wheat gluten). Three other diets were formulated based on the control but with 10, 17.5, or 25% of DDGS replacing FM. Diets were tested in triplicate, in an 84-days growth trial with juveniles of 29 g initial body weight. Feed intake was not affected by diet composition, but growth and feed efficiency linearly decreased with the increase of dietary DDGS level. Whole-body dry matter and protein contents were not affected by diet composition, but lipid and energy content were higher in fish fed the control diet than the 17.5DDGS and 25DDGS diets and the 25DDGS diet, respectively. The apparent digestibility coefficients (ADCs) of protein and amino acids were similar among diets, while the ADCs of energy decreased with the increase of dietary DDGS level. Digestive amylase and lipase activities in posterior intestine were lower in fish fed the 17.5DDGS and 25DDGS diets than the control diet, while proteases activity was not affected by diet. No differences among dietary treatments were observed on plasma glucose, but plasma total protein, albumin, triglycerides, and cholesterol were lower in fish fed the DDGS diets. Activity of key enzymes of glycolysis, gluconeogenesis, and lipogenesis was not affected by diet composition, but activity of alanine aminotransferase increased with the increase of dietary DDGS. Moreover, oxidative status of liver and intestine was not affected by dietary treatments, but susceptibility to oxidative stress was higher in the intestine than in the liver. Overall, it is concluded that replacing FM by DDGS in practical diets for turbot juvenile reduced growth performance and impaired overall nitrogen and energy metabolism.

Apparent Digestibilities of Selected Feed Ingredients Fermented by Host Bacteria in Juvenile Turbot, Scophthalmus maxima L.

Fermentation is considered a promising method to improve the limited utilization of plant protein sources. In the present study, Shewanella sp. MR-7, isolated from the intestine of juvenile turbot, was used to ferment selected plant sources. We investigated the apparent digestibility coefficients (ADCs) of three plant sources fermented and not fermented by Shewanella sp. MR-7 in diets of juvenile turbot: soybean meal (SBM), fermented soybean meal (FSBM), peanut meal (PM), fermented peanut meal (FPM), corn gluten meal (CGM) and fermented corn gluten meal (FCGM). The ADCs of dry matter (DM), crude protein (CP), gross energy (GE), and amino acids（AA）were analyzed. Our results showed that the ADC of the plant protein sources improved significantly with fermentation. Moreover, the FSBM showed the highest improvement for apparent amino acid digestibility while FPM showed the lowest compared with the unfermented plant protein source. In conclusion, our results indicated that Shewanella sp. MR-7 fermentation can greatly improve the ADCs of SBM, PM, and CGM in diets of turbot. This study providedvaluable information for the use of host bacteria as zymocyte in aquaculture.

Effects of replacing fishmeal with different cottonseed meals on growth, feed utilization, haematological indexes, intestinal and liver morphology of juvenile turbot (Scophthalmus maximusL.)

A ten-week feeding trial was conducted to evaluate the effect of replacing fishmeal with two differently processed cottonseed meals (CSM), namely XC and SC, separately in turbot (5.28 ± 0.02 g). Nine isonitrogenous and isoenergetic diets were formulated without fishmeal replacement (FM), 150 g/kg (XC15, SC15), 250 g/kg (XC25, SC25), 350 g/kg (XC35, SC35) and 450 g/kg (XC45, SC45) of fishmeal replaced by CSM. Fishmeal was successfully replaced by XC in turbot diets without growth reduction at 350 g/kg, but not by SC even at 150 g/kg. The apparent digestibility coefficients of SC-included diets were significantly lower than XC-included diets at same replacement level. The activities of aspartate aminotransferase and superoxide dismutase were significantly affected in XC45 and SC45 group. The XC45 and SC-included diets caused shortened distal intestine villi height and structural damage of liver compared with FM diet. This study indicated that different processing methods could affect the nutritional value of CSM and effect as a protein source for turbot. CSM with high quality could be an important alternative dietary protein source for juvenile turbot.

Blue Mussel Protein Concentrate Versus Prime Fish Meal Protein as a Dietary Attractant for Turbot (Psetta maxima L.) Given Rapeseed Proteinbased Diets

A feeding experiment was conducted to test the attractant potential of a processed protein concentrate of the blue mussel (BMPC) as replacer for fish meal (FM) protein in rapeseed protein concentrate (RPC)-based diets for turbot. Triplicate fish groups received isonitrogenous and isoenergetic diets with a 50% or 75% replacement of FM protein by a RPC (RPC 50, RPC 75), and further FM protein substitution with 0, 2, 4 or 8% of BMPC. The application of RPC 50/0 provided no significant impact on fish performance compared to FM-reference diet, while daily feed intake (DFI), specific growth rate (SGR) and feed conversion were significantly impaired when fish fed with RPC 75/0 (P 0.05). Protein efficiency ratio and protein productive values remained unaffected among all treatments (P>0.05). Excepting crude ash content, no changes in crude protein, crude lipid, dry matter and energy content were obtained. Hepatosomatic index tended to increased (P>0.05) in accordance with slightly hypertrophic hepatocytes of fish fed diets with a BMPC incorporation of 40-80 g kg-1. Neither inflammatory nor degenerative alterations were detected in the intestine. In summary, we demonstrated that BMPC failed to stimulate the feed intake of turbot when dietary FM protein was substituted consecutively, but it was found to maintain performance level of turbot within the test diet groups. This indicates nutritional properties of BMPC comparable to prime FM protein, functional to further reduce the FM protein content in aquafeeds for carnivorous fish.

Soybean meal induces enteritis in turbot Scophthalmus maximus at high supplementation levels

The goal of the present study was to find whether higher soybean meal (SBM) levels might trigger soybean meal-induced enteritis (SBMIE) in turbot. If so, caution must be taken when mixing ingredients containing saponins and other antinutrients to avoid SBMIE like symptoms. In a 8week feeding trial conduced on turbot, three isonitrogenous and isolipidic diets were formulated to include 26%, 40% and 54% SBM to progressively replace 30%, 45% and 60% fish meal (FM) in a FM based diet, respectively. The results showed that SBM caused dose-dependent decreases in growth performance and nutrient utilization. Enteritis developed in the distal intestine in the inclusion range of 26–54%. Dose-dependent increases in severity of the inflammation, with concomitant alterations in brush border membrane enzymes and inflammatory marker genes expression were seen. Our results confirm the hypothesis that high inclusion level of SBM may cause similar inflammatory changes as observed in several other fish species. Thus, caution must be taken when formulating turbot diets based on ingredients that may contain saponins and other antinutrients. Moreover, turbot is also a candidate species for the study of causes and mechanism of diet induced inflammation in the intestine of fish. Statement of relevanceThe present work first describes the soybean meal induced enteritis in turbot and provides the information that caution must be taken when formulating turbot diets based on ingredients that may contain saponins of other antinutrients.

Effects of soybean meal fermentation by Lactobacillus plantarum P8 on growth, immune responses, and intestinal morphology in juvenile turbot (Scophthalmus maximus L.)

In the present study, Lactobacillus plantarum P8 was used to ferment soybean meal (SBM), resulting in a significant reduction in the indigestible oligosaccharides (sucrose, raffinose, and stachyose) and anti-nutritional factors (tannin, trypsin inhibitors, glycinin, and β-conglycinin) in SBM. Nine isonitrogenic and isoenergetic experimental diets were formulated in which SBM or L. plantarum P8 fermented SBM (LPFSBM) replaced fish meal (FM) protein with 0 (control); 15% by SBM (Diet 1), 30% by SBM (Diet 2), 45% by SBM (Diet 3), 60% by SBM (Diet 4), 15% by LPFSBM (Diet 5), 30% by LPFSBM (Diet 6), 45% by LPFSBM (Diet 7), and 60% by LPFSBM (Diet 8). Triplicate groups of 30 fish were fed to apparent satiation twice daily for 66 d in an indoor recycling seawater system. No significant differences were found in survival rate among the different groups. However, 45% SBM, 60% SBM, and 60% LPFSBM (Diets 3, 4, and 8) diets significantly reduced growth performance and feed utilization. The LPFSBM diets did not affect moisture, crude protein, crude lipid, or crude ash contents of whole-body measurements. However, 60% SBM (Diet 4) significantly decreased crude protein and lipid content while increasing moisture and crude ash contents of the whole-body. The activity of serum lysozyme was significantly decreased in the group fed with 60% SBM (Diet 4). Total antioxidant capacity was significantly increased in the group fed the 45% LPFSBM (Diet 7). Apparent digestibility coefficient (ADC) of protein was significantly lower in fish fed diets with 45% and 60% of protein from SBM and 60% of protein from LPFSBM than in the control group. When the substitution level of SBM was equal to or above 45%, the activities of protein metabolism enzymes (alanine aminotransferase, ALT and aspartate aminotransferase, AST) were significantly lower than those in the control group. The level of LPFSBM did not affect the activities of ALT and AST. SBM-induced pathological changes seen in the distal intestine of fish fed 45% and 60% SBM (Diets 3 and 4) were not pronounced in groups fed LPFSBM. The results of the present study suggest that protein from SBM could substitute up to 30% of FM protein, with protein from LPFSBM being able to replace up to 45% of FM protein. Statement of relevanceThe present study was conducted to investigate the effects of Lactobacillus plantarum P8 fermentation on soybean meal and evaluate LPFSBM as a partial replacement for fish meal in diets of turbot by examining growth, activities of protein metabolism enzymes, intestinal morphology, and immune responses. Our results would be helpful to develop cost effective and sustainable dietary formulations for turbot.The results of this study indicate that LPFSBM could replace up to 45% of fish meal protein in juvenile turbot diet. The ANFs are important factors that affect the growth performance of turbot, damaging the normal structure of intestine and a depression of digestion and absorption function. LPFSBM reduced SBM-induced pathomorphological changes in the distal intestine which partly accounted for the L. plantarum P8 fermentation reduces indigestible oligosaccharides and anti-nutritional factors in soybean meal and enhanced the apparent digestibility coefficients (ADCs) of dry matter and crude protein of soybean meal. The results are reliable and of both theoretical and practical importance.The work described has not been submitted elsewhere for publication, in whole or in part, and all the authors listed have approved the manuscript that is enclosed. I have read and have abided by the statement of ethical standards for manuscript submitted to Aquaculture.

Effects of Replacing Fish Meal with Soybean Meal or Fermented and Phytase-Treated Soybean Meal Respectively, on Growth Performance, Feed Utilization, and Apparent Digestibility in Juvenile Turbot (Scophthalmus maximus L.)

The objective of this study was to evaluate the effect of fish meal (FM) substitution with gradient soybean meal (SBM) or fermented and phytase-treated soybean meal (PHSBM) in the diets of turbot (Scophthalmus maximus). A 9 week feeding trial was conducted using juvenile turbots (Scophthalmus maxima) fed seven experimental diets. The seven isonitrogenous (approximately 50% crude protein) and isoenergetic (approximately 21.0 kJ/g diet of gross energy) diets were formulated to include FM protein substitution with corresponding amounts of protein from soybean meal and phytase-treated soybean meal sources. Results showed that survival rate and feed intake did not differ significantly between the FM diet and any plant protein incorporated diets. Compared with the FM diet, final body weight and SGR were significantly reduced by the SBM2, SBM3, and PHSBM3 diets. Except for the PHSBM1 diet, feed efficiency ratio in the other SBM or PHSBM incorporated diets was much lower than in the FM diet. Body ash content was not affected by gradient PHSBM incorporated diets compared with the FM diet, while SBM incorporated diets (SBM2 and SBM3) showed a higher ash content than the FM diet (P&lt;0.05). Body crude protein was significantly reduced when fishmeal protein was replaced by soybean meal up to 60% (SBM3). There was no significant difference in the crude lipid and moisture contents among different treatments. Fish meal replaced by gradient PHSBM did not affect the apparent digestibility coefficients (ADC) of dry matter and crude protein, while the ADC of dry matter was markedly reduced in all the soybean meal incorporated diets compared with the FM diet. These results show that 30% fish meal protein could be replaced by soybean meal in the diet of turbot, while PHSBM could be substituted for up to 45% dietary fish meal.

Effect of Partial Substitution of Fish Meal with Sunflower Meal on Feed Utilization, Intestinal Digestive Enzyme, Hematological Indexes, Intestinal, and Liver Morphology on Juvenile Turbot (Scophthal musmaximus L.)

A 70-day feeding trial was conducted to evaluate effects of partial substitution of fish meal (FM) by sunflower meal (SFM) on juvenile turbot (Scophthal musmaximus L.). Five isonitrogenous and isoenergetic diets were formulated with 0%, 15%, 25%, 35%, and 45% replacement of FM protein with protein from SFM. Triplicate groups of juvenile turbot (30 fish per group), were hand-fed twice daily to apparent satiation. Final body weight (FBW), specific growth rate (SGR), and weight gain rate (WGR), were not significantly influenced by type of plant protein at the 15% level (P&gt;0.05), while higher levels showed significant reduction of FBW, SGR, WGR. Feed efficiency ratio (FER) and feed intake (FI) were significantly influenced when FM protein was replaced up to 45% (P&lt;0.05). Body composition parameters were not affected by SFM substitution but body crude lipid was lowest and ash was highest at 45% (P&lt;0.05). Trypsin and diastase values did not vary with experimental diets but lipase activity was significantly reduced (P&lt;0.05). Catalase (CAT) values were significantly lower than the control (P&lt;0.05) when substitution level reached or exceeded 35%; no significant differences were observed in total antioxidant capacity (T-AOC) and malondialdehyde (MDA) values (P&gt;0.05). In the SFM diet groups, all superoxide dismutase (SOD) values were significantly higher than the control (P&lt;0.05); villi length and enterocytes were significantly reduced (P&lt;0.05), but there was no significant difference (P&gt;0.05) in microvilli height between diets; parenchyma structure of liver was severely damaged; smaller hepatocyte areas and areas with high levels of hepatocyte vacuolization and disorganization were present. All results indicated that SFM protein can partially replace FM protein in juvenile turbot diets without adverse effects.

Graded levels of fish protein hydrolysate in high plant diets for turbot (Scophthalmus maximus): effects on growth performance and lipid accumulation

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±0.01g). 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 RelevanceThis 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.

A combination of corn gluten and soybean meal as a substitute for fishmeal in diets of turbot (Scophthalmus maximusLinnaeus, 1758) in brackish water

This study was conducted to test the replacement of fishmeal (FM) with a combination of corn gluten meal (CGM)-soybean meal (SBM) (at a ratio of 58 : 42, respectively) fortified with lysine, taurine and monocalcium phosphate (MCP) in turbot (Scophthalmus maximus) diets. FM as the main protein source in the control diet (FM100) was replaced in 15% decrements while increasing the combination of replacement material: 85% FM (FM85), 70% FM (FM70), 55% FM (FM55) and 40% FM (FM40). The diets were fed to triplicate groups (n = 25 per group) for 9 weeks (water temperature, dissolved oxygen, pH and salinity of 18.59 ± 0.06°C, 7.32 ± 0.02 mg L−1, 7.73 ± 0.01 and 8.46 ± 0.04 g L−1, respectively). Initial weight of fish was 286.1 ± 0.1 g. At the end of the experiment, growth, feed and nutrient utilization performance of fish fed FM85 and FM70 were similar to FM100, but a further increase in plant protein led to a significant reduction of these parameters. Whole body, fillet, viscera and liver nutrient compositions were not affected significantly; however, whole body lipid levels were significantly lower in fish on FM55 and FM40 than those on FM100. The fish in–fish out ratio in the diets decreased from 2.12 in FM100 to 1.00 in FM40. The results suggest that the FM level could be reduced by 30% with a combined use of CGM-SBM supplemented with lysine, taurine and MCP.