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Demand for organic aquaculture is rising, but its viability will depend on the availability of economically viable raw materials to formulate organic diets. In the current work, organic diets were formulated based on different alternative protein sources distinguished by their ecological origin, insect meal (IN), seabass by-products (SB) and Iberian pig by-products (IB) in rainbow trout (Oncorhynchus mykiss) and their effects on growth, efficiency, productivity, and intestinal health. Fish with an initial weight of 67.2 g were fed two times a day until apparent satiation for 150 days. The control diet containing fish meal (FM) originated the highest final weight (298 g). Results obtained in the final body weight and the specific growth rate feed conversion ratio average daily gain indicate that the SB-FM, SB-IB, and SB-IN-IB diets presented a lower performance (272 g, 257 g, and 258 g final weight respectively) and FM-IN and IN-IB diets had the lowest final weight (215 g and 183 g respectively). An improvement in growth performance and nutrient utilization was observed in the SB-FM, SB-IB, and SB-IN-IB diets concerning the FM-IN and IN-IB diets. The lowest retention efficiencies of protein, fat, and essential amino acids were found in the IN-IB diet. The highest apparent digestibility coefficients (ADCs) of protein, energy, calcium, and phosphorus are found in Control and FM-IN diets. Results of enzymes showed that both trypsin and chymotrypsin are relatively low in IN-IB and SB-IN-IB. Fish-fed FM-IN and IN-IB diets showed histological changes in the liver and intestine. Considering the intestinal microbiota composition, the three dominant phyla were Firmicutes (59–89%), Spirochaetota (5–35%), and Proteobacteria (3–16%), but no differences between diets were obtained. No significant differences were observed on the Alpha diversity Shannon index. Therefore, although differences in growth were observed, the high substitution of fishmeal did not imply an alteration of the intestinal microbiota, possibly due to the high dominance of Firmicutes. Nevertheless, from an economic point of view, SB-IB diets gave the lowest economic conversion index and the highest economic profit index. In conclusion, the substitution of fishmeal affected the growth of the animal, registering the best results in the control followed by diets containing fishmeal of marine origin, but the lowest price of animal by-products originated the best economic results. • Organic diets for rainbow trout utilizing eco-friendly sources. • Findings from a 150-day study highlighting performance variations. • Critical insights into nutrient retention guiding the optimization of organic diets. • Despite growth differences, stability was observed in microbiota. • Cost-effective approach for organic aquaculture. [ABSTRACT FROM AUTHOR]

The effects of replacing dietary fishmeal with cottonseed protein concentrate (CPC) on the muscle texture and water holding capacity of large yellow croaker Larimichthys crocea were investigated after a 90-day feeding trial. Results showed that the complete substitution of dietary fishmeal with CPC resulted in a significant reduction in muscle drip loss by decreasing collagen content and increasing heat soluble collagen content, without affecting the texture. Moreover, reduced drip loss is contingent upon diminished muscle salt-soluble protein content by enhancing skeletal muscle degradation (ubiquitin-proteasome system, calpain proteases and lysosomal cathepsins) and decreasing energy levels. In conclusion, the substitution of 30% dietary fishmeal with CPC (i.e., 20.94% of CPC in diet) did not show any significant alterations in muscle quality of large yellow croaker. The complete replacement of dietary fishmeal with CPC (i.e., 69.80% of CPC in diet) reduced the water holding capacity of muscle. • Cottonseed protein concentrate (CPC) can be used as a dietary protein source for large yellow croaker (LYC). • The CPC can replace 30% of dietary fishmeal (i.e., 20.94% of CPC in diet) without compromising the muscle quality of LYC. • Complete replacement of dietary fishmeal with CPC (i.e., 69.80% of CPC in diet) reduced the water holding capacity of muscle. • Excessive dietary CPC decreased the synthesis of collagen and myofibrillar protein in muscle. [ABSTRACT FROM AUTHOR]

Black soldier fly (Hermetia illucens) larvae meal is emerging as an alternative protein source and good substitute of fishmeal (FM). In an 8-week feeding trial, three hundred pangasius (Pangasianodon hypophthalmus ,7.44 ± 0.01 g) fingerlings were randomly allocated over five treatments in triplicate tanks and fed five isoprotein (CP, 35%) and isolipidic (CL, 10%) diets formulated by replacing 0% (FBSFL0), 25% (FBSFL25), 50% (FBSFL50), 75% (FBSFL75) and 100% (FBSFL100) FM with organic acid (formic acid) fermented black soldier fly larvae meal (FBSFL). The inclusion of FBSFL did not affect growth, feed conversion ratio, nutrients utilization and survival rate of pangasius even when FM was completely replaced. The pangasius body protein content increased significantly (P < 0.05) with increasing FBSFL level in the diets while, body lipid content was unaffected (P > 0.05). The haematological indices were not (P > 0.05) affected with the FBSFL inclusion levels. Significantly (P < 0.05) higher and alike protease activity was recorded in FBSFL50, FBSFL75, and FBSFL100 groups. However, activity of amylase and lipase were similar among treatments. The liver antioxidant enzymes (SOD, catalase, and GST) did not show significant (P > 0.05) difference among the treatments. However, pangasius fed with FBSFL75 and FBSFL100 showed significantly higher and similar total antioxidant capacity (T-AOC). The FBSFL in the diet of pangasius did not affect the liver metabolic enzyme (MDH, G-6-PDH and GDH) activities. Relative gene expression of growth hormone (GH1) did not substantially differ among the groups (P < 0.05). No differences were observed in the immune gene expressions of complement (C3) and interleukin-1β (IL-1β) but the expression level of transferrin was up-regulated significantly (P < 0.05) in FBSFL25 group. No damage was observed in hepatic tissues in histomorphometry examination due to the inclusion of FBSFL. The study concludes that formic acid fermented BSFL can be employed as a complete substitute for FM in the pangasius diet, offering additional health benefits without any adverse effects. • Black soldier fly larvae meal (BSFLM), fermented with formic acid, served as a fishmeal (FM) alternative. • Complete replacement of FM with fermented BSFLM did not negatively impact growth and nutrient utilization in pangasius. • The inclusion of fermented BSFLM led to a significant (P < 0.05) increase in protease activity in pangasius. • The use of fermented BSFLM did not induce adverse effects on the hepatic health of pangasius. • Fermented BSFLM showed no negative impact on the immunity of pangasius. [ABSTRACT FROM AUTHOR]

This study investigated the effects of replacing fish meal (FM) with biofloc meal (BM) on the growth, digestion function, protein metabolism, lipid metabolism, immunity, antioxidant capacity and intestinal microbiota of common carp (Cyprinus carpio). The experiment includes two trials (a growth trial and a digestibility trial). In the growth trial, the control diet contained 20% FM. And five isonitrogenous and isolipidic diets were formulated to replace 0% (CK), 20% (BM20), 40% (BM40), 60% (BM60) and 80% (BM80) of the FM protein with BM. The five diets were fed to common carp (3.73 ± 0.01 g) for 56 days. The results indicated that the growth performance [final weight (FW), specific growth rate (SGR) and feed efficiency ratio (FER)] and digestive enzymes activities displayed a noteworthy quadratic trend with the increasing replacement level of FM with BM (P < 0.05), reaching a maximum at the BM40 group and a minimum at the BM80 group. Regression analysis of weight gain rate (WGR) against the substitution level found that the optimal level of BM replacing FM was 34.12%. The appropriate levels of BM could improve protein metabolism and lipid metabolism by regulating the expressions of related genes. Regarding the expression levels of PI3K , mTOR and HSL mRNA, they were the highest in the BM40 group and the lowest in the BM80 group, while the levels of ACC and FAS mRNA were reversed (P < 0.05). Simultaneously, the number of lipid vacuoles in the BM80 group were significantly increased than the CK group. Replacing 40% FM with BM augmented the fish immunity and antioxidant capacity, as showed by elevated the C3, C4 and IgM levels as well as CAT and SOD activities, and reduced the expression levels of NF-κB , TNF-α and Keap1 (P < 0.05). Regarding intestinal microbiota, replacing 40% FM with BM could improve the intestinal microbiota structure. The digestibility trial results showed that the apparent digestibility of protein and lipid in BM of common carp was slightly lower than FM. Conclusively, replacing 40% FM with BM could promote growth, immunity and protein metabolism of common carp, but excessive substitution level (80%) could compromise growth and hepatopancreas health. • Biofloc meal (BM) derived from discard bioflocs is a promising substitute for fish meal (FM). • BM could improve protein metabolism by regulating mTOR signaling pathway, thereby promoting growth. • BM is a new functional protein sources that could regulate immune factors and augment antioxidant capacity. [ABSTRACT FROM AUTHOR]

Bacterial diseases pose significant challenges to sustainable development in aquaculture ponds. Enhancing the intestinal mucosal barrier, serum immunity, and antioxidant capacity are crucial for bolstering the disease resistance of cultured animals. In this study, six types of feed were prepared using soybean meal (SM) and fish meal (FM) as protein sources, namely FM (containing 50% fish meal), SM (containing 50% soybean meal), SM + FM (containing 25% soybean meal and 25% fish meal), SM + FM + C-I20 (containing 25% soybean meal, 25% fish meal, and 0.2% C I20), SM + C-I20 (containing 50% soybean meal and 0.2% C I20), FM + C-I20 (containing 50% fish meal and 0.2% C I20), to study the protective effect of nanopeptide C I20 on bullfrog (Rana catesbeiana) ponds. Throughout a continuous 56-day cultivation cycle, various groups of bullfrogs naturally experience outbreaks of skin rot disease, accompanied by a significant increase in Aeromonas hydrophila load. Surprisingly, the FM + C-I20 group and SM + FM + C-I20 group exhibited a substantial improvement in the overall protection rate of bullfrogs and a reduction in daily mortality rates. Moreover, the addition of C I20 significantly decreased the tissue load of A. hydrophila and mitigated tissue damage. The incorporation of C I20 into FM and SM + FM feeds resulted in increased mucin thickness, goblet cell count, antioxidant activity (T-AOC, TSOD, and GSH-Px), white blood cell count, and lysozyme activity. C I20 effectively established the intestinal mucosal immune barrier, serum immunity, and antioxidant capacity, thereby enhancing the disease resistance of bullfrogs. In conclusion, C I20 biotherapy emerges as an effective strategy for treating bacterial diseases in bullfrogs in a pond system. This study provides a novel and prospective approach for controlling bacterial diseases in aquaculture. • C I20 effectively enhances innate defense systems to resist bacterial diseases. • Oral C I20 significantly decreases morbidity rate and mortality rate. • Oral C I20 markedly reduces bacterial load and tissue damage in cultivation cycle. [ABSTRACT FROM AUTHOR]

Five experimental diets (CTRL, 50FMFO, 50FMFO-50MIC, 0FMFO-50MIC, 0FMFO-100MIC) were formulated to replace wild-caught fishmeal (FM), wild-caught fish oil (FO) and soy protein using fisheries, aquaculture by-products (BP) and microalgae (MIC). Fifty European sea bass juveniles were distributed in 15 tanks (initial body weight 46.66 ± 0.04 g) and reared in a recirculating aquaculture system for 88 days. Temperature, salinity, oxygen and photoperiod were kept constant throughout the experiment (22 ± 0.5 °C, 25 g L−1 and 8.0 ± 1.0 mg L−1, 12:12 light/dark, respectively). Growth, feed intake (FI), proximal composition, nutritional index, apparent digestibility, somatometric indexes, blood plasma biochemistry and digestive enzyme activity were evaluated. Also, gut microbiota composition was assessed through next-generation sequencing. Results showed that growth performance and feed digestibility were not affected by FM, FO and soy replacement using BP and MIC. Dietary replacement of 100% FM and FO with circular substitutes and 50% replacement of soymeal with microalgae increased the activity of alkaline phosphatase and chymotrypsin. Moreover, the inclusion of BP and MIC had positive effects on the gut microbiota richness and abundance. In conclusion, the utilization of BP and MIC represents a valuable alternative to FM and FO as well as soy protein in feed for European sea bass juveniles. • Integration of FM and FO from trimming, with microalgae did not affect overall growth and feed efficiency. • Microalgae as a protein source promotes digestive enzyme activity. • Microalgae positively impact microbiota richness and abundance. [ABSTRACT FROM AUTHOR]

Knowledge of the amino acid (AA) requirements for striped catfish (Pangasianodon hypophthalmus) is very limited. The main objective of the study was to determine maintenance requirements and utilization of digestible methonine (Met) and other essential amino acids (EAA) for growth in juvenile striped catfish. To evaluate the objective, a series of three different trials were carried out. Initially, a 28-d feed deprivation study showed an allometric relationship between energy, protein, or AA losses (y) and geometric body weight (BW), where the relationship was expressed as a power function (y = a BW b ) with the exponent values (b) being 0.84 for energy, 0.83 for protein, and 0.81–0.90 for various EAAs. Next, a digestibility trial was carried out to determine apparent digestibility coefficients of energy, protein and AA from the ingredients, including: fish meal, soybean meal, wheat bran, regular and defatted rice bran. These values were then used in the final trial to formulate two diets on a digestible AA basis with similar crude protein (31%), energy (17.1 kJ g−1) and AA composition - except for digestible Met and Met+Cys, which were 0.47% and 0.90% for Diet A, and 0.61% and 1.05% for Diet B. The diets were fed to quadruplicate groups of fish (∼10 g initial weight; 20 fish per tank) at increasing ration levels (∼ 35%, 55%, 77%, 93% and 100% apparent satiation) for 64 days. One group was deprived of feed for 28 days. The results showed that feeding catfish at increasing ration levels significantly improves the growth performance in both dietary treatments. Additionally, the group fed Diet B showed significantly better weight gain than the corresponding group fed Diet A at 93% and 100% satiation. The maintenance requirement was determined to be 21.77 mg digestible (dig) Met kg−0.83 d−1 and 35.3 mg dig Met+Cys kg−0.83 d−1 based on a linear model and to be 18.8 mg digestible (dig) Met kg−0.83 d−1 and 30.7 mg dig Met+Cys kg−0.83 d−1 based on an exponential fit to the data. The efficiency of digestible Met utilization (k DMet assessed based on Diet B) for growth above maintenance was found to be 63% (including data of all ration levels) or 71% (excluding data of 100% satiation), while that for the Met+Cys (k DM+C) was found to be 46% (including data of all ration levels) or 51% (excluding data of 100% satiation). The efficiency of digestible protein utilization for weight gain with Diet B was found to be higher (66%) than that with Diet A (57%), indicating the importance of balancing striped catfish diets for dietary Met. The study also determined maintenance requirements and utilization efficiency of other EAAs which need to be further improved. These data can be used to derive AA requirements for striped catfish based on a factorial modelling approach which relies on maintenance requirements, growth utilization of AA, and targeted growth or protein deposition. • An allometric relationship (y = a BW b ) was established between energy, protein, or amino acid losses (y) and geometric body weight (BW), with the exponent values (b) being 0.84 for energy, 0.83 for protein, and 0.81–0.90 for various EAAs for striped catfish. • Maintenance requirements (mg kg−0.83 d−1) of digestible Met was determined to be 21.77 mg and 18.8 mg and that of digestible Met + Cys was determined 35.3 mg and 30.7 mg, based on linear and exponential models, respectively. • Growth utilization efficiency of digestible Met was estimated to be 63% (or 71% when excluding data of 100% apparent satiation), while that of digestible Met+Cys was found to be 46% (or 51% when excluding data of 100% apparent satiation). • The study also provided maintenance requirements and utilization efficiency of protein and other essential amino acids. [ABSTRACT FROM AUTHOR]

Methionine is the first-limiting essential amino acid in plant-based diet, and also is the most toxic amino acid. The study aimed to evaluate the tolerance and toxicity of a dipeptide DL -methionyl- DL -methionine (Met-Met) in the diet of common carp Cyprinus carpio. Five iso‑nitrogenous (∼ 380 g kg−1) and isoenergetic (∼185 MJ kg−1) diets were formulated including a positive control diet (100 g kg−1 fish meal, FM) supplemented with 3 g kg−1 DL -Met and four low fish meal diets (40 g kg−1 fish meal), with 0 (M0), 3 (M3), 6 (M6), and 15 (M15) g kg−1 Met-Met being supplemented. The Met-Met supplementation levels of 6 and 15 g kg−1 were designed as the 2- and 5-fold of the optimal level (3 g kg−1) for the tolerance and toxicity assessment, respectively. After 10 weeks of feeding, the lowest growth performance was observed in the M0 group, as evidenced by the lowest weight gain rate and specific growth rate. Contents of protein and amino acid in whole-body, and retentions of nitrogen and amino acid were highest in the M6 group, while these values decreased in M15 group. Fish fed diet M15 showed lower levels of albumin, high density lipoprotein cholesterol (HDL), total cholesterol, alkaline phosphatase, and higher alanine aminotransferase, total bile acid, total antioxidant capacity (T-AOC) compared with M3. Fish fed diet M15 had lower levels of glucose, HDL, and higher T-AOC and malonaldehyde compared to M6. Genes related to bile acid metabolism (cyp8b1 , rxrα , fxr), anti-inflammatory (tgfβ1 , tgfβ2 , il10), proinflammatory (tnfα , il1β , il17) were significantly down-regulated in the M15 group compared to M3. However, caspase-3 expression significantly up-regulated in the M15 group compared with M6. Increased signals of hepatic vacuolation and fibrosis were observed in the M0 and M15 groups. Besides M15 group showed higher expression of apoptosis signal marker, cleaved caspase-3 in hepatopancreas. This study clarified the safety margin of Met-Met was 2× dosage as 6 g kg−1, while 15 g kg−1 Met-Met caused deleterious consequences, manifested as the highly occurred of cholestatic liver disease. • Met-Met is an efficient methionine source to improve growth of common carp. • The safety margin of Met-Met was 6 g kg−1, as 2× of optimal level on common carp. • 5× overdose Met-Met did not negatively affect growth performance. • 5× overdose Met-Met induced high-proportioned cholestatic liver disease with fibrosis. [ABSTRACT FROM AUTHOR]

The intensified aquaculture production and heavy feed use have placed high pressure on the environment due to increasing waste. This study aims to understand how stakeholders along the aquaculture value chain evaluate feed produced from nutrients recovered from waste in aquaculture production. Using a mixed method combining a systematic literature analysis by synthesizing 171 articles and a qualitative analysis with information collected from 45 respondents including fishmeal producers, feed producers, feed traders, hatcheries, farmers, shrimp traders, and shrimp processors cum exporters in an emerging economy of Viet Nam, the study reveals that the stakeholders in the value chain are aware of and willing to accept the feed produced from nutrients recovered from waste in aquaculture production. The motivation of each stakeholder to produce or use the feed is conditional on that of other stakeholders. The findings suggest that the removal of conditional motivation cannot be left to the market and government support is needed. • The stakeholders along the aquaculture value chain are aware of and willing to accept the feed produced from nutrients recovered from waste in aquaculture production. • The motivation of each stakeholder to produce or use the feed is conditional on that of other stakeholders. • Utilizing nutrients recovered from waste in aquaculture production should be effective if there are joint actions of stakeholders in the aquaculture value chain. • The removal of conditional motivation cannot be left to the market. Government support is needed. • A pilot project funded by the government to reveal the values of nutrients recovered from waste in aquaculture production could be an important touchpoint for the stakeholders along the aquaculture value chain. [ABSTRACT FROM AUTHOR]

Essential amino acid (EAA) requirements of aquaculture fish species can be used as a guideline for commercial feed formulation. Several EAA requirements have been quantified in tiger puffer (Takifugu rubripes). However, as the third limiting amino acid (AA) of many plant protein sources, tryptophan requirement of this species has yet to be quantified. This study was conducted to determine dietary tryptophan requirement of tiger puffer, and investigate the effect of dietary tryptophan supplementation on the cannibalism, brain serotonin (5-hydroxytryptpamine, 5-HT) metabolism and serum cortisol levels. Six experimental diets were prepared using fish meal, gelatin and corn protein concentrate as intact protein, and then supplemented with crystalline AA premix. The analyzed tryptophan levels in the experimental diets were 3.5, 4.1, 4.5, 5.5, 7.0 and 11.8 g/kg of dry diet. Experimental diets were randomly fed in triplicate to tiger puffer (initial average weight of 17.5 g) for 58 days. The weight gain (WG), feed conversion ratio (FCR) and protein efficiency ratio (PER) were significantly affected by dietary tryptophan, and the break points were observed at 5.07, 4.82 and 4.99 g/kg of dry diet, respectively. Compared to the basal diet, the cannibalism (the rate of bite mark appearance) was significantly lower and survival rate was significantly higher when fish were given diets containing 7.0 and 11.8 g/kg tryptophan. The concentrations of free tryptophan and phenylalanine in the brain exhibited a nonlinear increase in response to the incremental levels of dietary tryptophan. Brain 5-HT concentration was significantly affected by dietary tryptophan levels, but did not show a significant dose-dependent response. The expression of genes related to 5-HT metabolism (tph1a , ddc and aldh) and serotonin reuptake (sert) in the brain varied significantly and exhibited a nonlinear relationship with the graded levels of dietary tryptophan. In addition, serum cortisol levels showed a decreasing trend till the 5.5 g/kg tryptophan inclusion level, at which point there appeared to be the lowest level. In conclusion, based on nonlinear regression analysis of the WG, FCR and PER, dietary tryptophan requirement of tiger puffer was determined to be range between 4.82 and 5.07 g/kg of dry diet (10.48–11.03 g/kg of dietary protein). Dietary tryptophan supplementation above requirement could mitigate cannibalism and improve the survival of tiger puffer, which may be attributed to regulating the synthesis and catabolism of 5-HT and its availability in the synaptic cleft, and subsequently the reduction of serum cortisol content. • The dietary tryptophan of tiger puffer was determined to range between 4.82 and 5.07 g/kg of dry diet. • Dietary tryptophan supplementation could reduce cannibalistic behavior and improve the survival of tiger puffer. • The mRNA levels of tph1a , ddc , aldh and sert in the brain exhibited a dose-dependent response to dietary tryptophan levels. • Serum cortisol level decreased nonlinearly with the increase of dietary tryptophan. [ABSTRACT FROM AUTHOR]

Yeast culture (YC), a microecological product derived from yeast fermentation, can enhance animal growth, health, and resistance to heat stress. However, its impact on the economically significant crustacean Eriocheir sinensis has not been demonstrated. This study investigated the effects of low-fishmeal YC on the growth, intestinal health, and heat stress resistance of juvenile Chinese mitten crabs. Crabs (0.72 ± 0.01 g) were distributed across 42 tanks, and 40 crabs were randomly maintained per tank in six replicates. The crabs were fed a control diet (35% fish meal) or six YC concentrations (15% fish meal; 0, 0.8, 1.6, 2.4, 3.2, or 4.0 g/kg) for 56 days. After sample collection, the remaining crabs were subjected to a 72-h heat stress challenge at 32 °C. A moderate-yield YC diet significantly improved weight gain, specific growth rate, and digestive enzyme activities (α-amylase, trypsin, and lipase) compared to those of crabs fed a 15% fishmeal diet without YC. Notably, the diet with 3.2 g/kg YC supplementation was performed as well as crabs fed a 35% fishmeal diet. YC also enhanced intestinal morphology in the low-fishmeal diet group and reduced oxidative damage by increasing the expression of genes related to the peritrophic membrane and tight junction proteins. Furthermore, YC supplementation diversified the intestinal microbiota, significantly increased the abundance of Firmicutes and the genus Shewanella , increased acetate and butyrate levels and decreased the abundance of Proteobacteria. Correlation analysis revealed that weight gain and specific growth rate were associated with most digestive activity and intestinal health indicators. Following heat stress challenge, YC protected against oxidative stress and enhanced serum immunity at elevated temperatures. This study indicated that incorporating YC in low-fishmeal diets significantly increases juvenile crab growth, improves intestinal health, and mitigates oxidative stress induced by temperature elevation. The optimal YC concentration was determined to be 2.71 g/kg through regression analysis. [Display omitted] • Dietary 2.71 g/kg yeast culture was optimal for E. sinensis fed low-fishmeal diets. • Yeast culture boosted the growth of E. sinensis fed low-fishmeal diets. • Yeast culture enhanced the intestinal health of E. sinensis. • Yeast culture increased the resistance of E. sinensis to heat stress. [ABSTRACT FROM AUTHOR]

Two concurrent feeding trials was conducted to assess the effects of replacing fishmeal with poultry by-product meal (PBM) and supplementing dried porcine soluble (DPS) in large yellow croaker Larimichthys crocea diets at the optimal dietary protein level. In trial I, the reference diet (F40) contained fishmeal at 400 g/kg, and 40%, 60% and 80% of the fishmeal was substituted with PBM (the diets were termed as F24, F16 and F8). In trial II, the control diet (F16D0) contained fishmeal at 160 g/kg, and DPS was added at 4, 8, 12 and 16 g/kg in F16D0 (the diets were termed as F16D4, F16D8, F16D12 and F16D16). Fish initially weighing 20.0 ± 0.2 g were fed the test diets for 10 weeks. Fishmeal replacement level significantly influenced final body weight (FBW), weight gain, feed conversion ratio, nitrogen and energy retention efficiencies, ratio of fish-in to fish-out (FIFO), feed cost, activity of superoxide dismutase and catalase in plasma and liver, activity of glutathione peroxidase in plasma, and malondialdehyde content in liver. However, neither fishmeal replacement level nor DPS supplementation level resulted in significant change in condition factor, hepatosomatic index and body composition. There were no significant differences in weight gain and FBW either between F40, F24 and F16 or between F40 and F16D0, F16D4, F16D8, F16D12 and F16D16. The FBW of F16 declined by 3.2% relative to F40, while the FBW of F16D12 increased by 10.1% relative to F16D0. This study reveals that dietary fishmeal level for large yellow croaker could be reduced to 160 g/kg by using PBM as a sole substitute, and DPS supplementation could augment dietary fishmeal replacement by PBM. • Fishmeal content in large yellow croaker diet could be reduced to 160 g/kg by inclusion of PBM. • Adding 12 g/kg DPS benefited to augment growth of large yellow croaker fed the diet containing 160 g/kg fishmeal. • Replacement of fishmeal with PBM reduced feed cost, fishmeal reliance and phosphorus waste. [ABSTRACT FROM AUTHOR]

Filamentous fungi have potential as an alternative protein source for use in aquafeeds due to their high protein content and bioactive components. Paecilomyces variotii (PEKILO® mycoprotein) is a β-glucan- and nucleotide-rich filamentous fungi with a crude protein (CP) content of 60–70%. A 9-week feeding trial was conducted to evaluate the effects of P. variotii in diets for Atlantic salmon (initial average body weight of 24 g fish−1) reared in freshwater. Four experimental diets were formulated. Diet 1 was a control diet based on fish meal, soy protein concentrate, and wheat gluten meal. Diets 2, 3, and 4 were formulated so that P. variotii replaced 5, 10, and 20% of the CP content of the diets, respectively. Results showed that dietary inclusion of P. variotii was associated with changes in physical pellet quality, including significant linear (p < 0.0001) and/or quadratic (p < 0.01) decreases in pellet length, width, expansion, and durability. Conversely, significant linear (p < 0.0001) and quadratic (p < 0.025) increases in water activity, bulk density, and water stability index were associated with increasing replacement of the CP content of the diets with P. variotii. There were no significant differences in weight gain, growth rate or feed intake among fish fed the experimental diets (p > 0.05), but a significant linear improvement (p < 0.025) in feed conversion ratio (FCR) with increasing dietary inclusion of P. variotii was observed. The apparent digestibility coefficients for CP and gross energy of the experimental diets decreased linearly (p < 0.01) with increasing dietary levels of P. variotii. Similar results were observed for the essential and non-essential amino acids. Despite reduced digestibility, linear increases in nitrogen (p < 0.01), energy (p < 0.025), and mineral (p < 0.001) retention efficiencies were associated with increasing dietary levels of P. variotii. In the distal intestine, dietary inclusion of P. variotii resulted in significant (p < 0.05) upregulation of several cytokines (ifng , il10 , and tgfb), effector molecules (inos , arg 1 , sod), and transcription factors (irf4), suggesting both activation and control of the inflammatory response in this key mucosa-associated lymphoid tissue. Overall, replacement of 20% of the CP content of the diet with P. variotii reduced digestibility of the experimental diets, but did not affect growth performance and improved FCR and nutrient utilization efficiency of salmon. Thus, P. variotii is a promising ingredient with potential for use in salmonid aquafeeds to improve fish performance and health. • P. variotii can replace 20% of the crude protein content in diets for Atlantic salmon. • Dietary inclusion of P. variotii significantly improved feed conversion ratio. • P. variotii was associated with increases in nutrient utilization efficiency. • P. variotti was associated with improved gut health. • P. variotii exhibited immuno-modulatory capacity in the distal intestine of salmon. [ABSTRACT FROM AUTHOR]

The current research investigated whether gamma (γ)-irradiation could improve the viability of defatted Hermetia illucens larvae (HIL) meal as a fishmeal alternative in black sea bream (Acanthopagrus schlegelii) diets. Three diets were formulated with equal protein (420 g/kg) and lipid (80 g/kg) contents. A diet containing 400 g/kg fishmeal was served as the control diet (C), and 50% of fishmeal in diet C was replaced by either defatted HIL meal or γ-irradiated defatted HIL meal to produce diet HR and diet HR10, respectively. Fish fed diet HR exhibited lower final body weight and weight gain compared to those fed diet C, while no statistically significant differences were found between fish fed diets C and HR10. Additionally, fish fed diet HR10 exhibited significantly lower feed intake, feed conversion rate, nitrogen waste, hepatic malondialdehyde content, relative usage of fishmeal and fish oil, fish-in to fish-out ratio, and economic conversion ratio, and meanwhile significantly higher nitrogen retention efficiency, hepatic total antioxidant capacity, economic profitability index and profitability, than those fed diet C. Fish fed different test diets showed statistically equal alpha diversity of intestinal microbiota, whereas the beta diversity of intestinal microbiota in group HR was far from groups C and HR10. Compared to fish fed diet C, the gut microbiota composition of fish fed diet HR showed significant alterations at both the phylum and genus levels. However, the altered composition of intestinal bacteria was partially restored in fish fed diet HR10. The above findings indicate that treating defatted HIL meal with γ-ray can reduce dietary fishmeal content for black sea bream to 200 g/kg without any adverse effects on growth, proximate composition and intestinal microbial diversity, and meanwhile ameliorates the feed utilization, hepatic antioxidant capacity, and intestinal microbiological composition of black sea bream. Furthermore, feeding γ-irradiated defatted HIL meal enhances the economic profitability, while reduces the waste output and reliance on fishery resource of black sea bream aquaculture. • Gamma (γ)-irradiated defatted Hermetia illucens larvae (HIL) meal replaces more fishmeal in the diet of black sea bream than the defatted HIL meal. • Replacing fishmeal with γ-irradiated defatted HIL improves growth, feed utilization, and economic profitability of black sea bream. • Dietary inclusion of HIL meal reduces the reliance on fishery resources and waste production of carbon, nitrogen, and phosphorus of black sea bream aquaculture. • Fishmeal content in black sea bream diet can be reduced to 200 g/kg by inclusion of γ-irradiated defatted HIL meal at 224 g/kg. [ABSTRACT FROM AUTHOR]

Fish feeding behaviour can be complicated and time consuming to observe, analyse and quantify. The conventional single ballotini X-radiography method was modified to determine the timing of feeding within a meal in farmed fish reared at commercial densities. Feed pellets containing two bead sizes were fed at different times during a single meal, either for the first half or second half of the meal. The two different ballotini sizes were differentiated on X-radiographs by human eye and semi-automated bead counting software was able to count the different bead sizes accurately. This dual ballotini method was used to assess whether fish ate earlier, later or during both halves of the meal and showed that individual fish feeding patterns were similar across two repeated meals. The method was applied to Chinook salmon (Oncorhynchus tshawytscha) , a premium farmed salmonid, to determine the relationship between feed conversion ratio (FCR) and the timing of feeding. Results showed that fish that ate smaller amounts of feed ate most of their meal at the end of the meal. There was no significant difference in when feed efficient or feed inefficient fish ate within the meal but, at the first dual ballotini assessment, there was a relationship between FCR and the timing of feeding where more efficient fish ate later in the meal. However, this relationship was absent at the second time point. Despite this, the dual ballotini method is a promising and versatile alternative method for the characterisation of fish feeding behaviours and can be applied under a range of conditions including higher rearing densities. • Two ballotini bead sizes can be fed. • Timing of feeding was identified. • Feed efficient fish eat later. [ABSTRACT FROM AUTHOR]

Heterobothriosis resistance and high growth performance are major concerns in the tiger pufferfish (Takifugu rubripes) farming. Our previous small-scale study suggested the feasibility of genomic selection (GS) for these traits but also identified an undesired genetic correlation between them, which could hamper simultaneous genetic improvement. Here, we sought to validate these initial findings through larger samples and crosses and also explore the potential of GS for the individuals fed a normal fishmeal diet and a low fishmeal (LFM) diet. We produced three populations: one was fed a normal diet (PopFM: 1100 individuals) and two were fed an LFM diet (PopLFM1: 993 individuals; PopLFM2: 1017 individuals); all three populations were artificially infected with Heterobothrium okamotoi , a monogenean parasite causing heterobothriosis. We recorded standard lengths of the fish after artificial infection (SL EAI) and the number of parasites on the gill cavity wall (HC) and genotyped genome-wide single nucleotide polymorphisms (SNPs) using genotyping by random amplicon sequencing, direct (GRAS-Di) technology for each sample: PopFM, 12 K SNPs; PopLFM1, 19 K SNPs; PopLFM2, 21 K SNPs. Heritability and prediction ability for each trait were estimated for each population using genomic best linear unbiased prediction (GBLUP), Bayes C, and Bayesian ridge regression methods. SNP effects on each trait were estimated by Bayes C, Bayesian ridge regression, and genome-wide association analyses (GWAS) using the same data sets. We observed moderate to high levels of heritability for HC (0.16–0.57) and SL EAI (0.50–0.77), with predictive ability of 0.25–0.55 for HC and of 0.51–0.73 for SL EAI. These values were slightly larger in LFM diet groups. As reported previously, a weak undesired genetic correlation was observed between the traits, and the correlation was more pronounced in the LFM groups. In conclusion, our results indicate that genetic gain in growth and parasite resistance traits can be expected for the tiger pufferfish through GS, especially for individuals reared on an LFM diet. However, close attention should be paid to the extent of the undesirable genetic correlation between the two traits that may be amplified in the populations fed an LFM diet. • Genomic selection can improve growth and heterobothriosis resistance in the tiger pufferfish fed standard or low fishmeal diets • Undesirable genetic correlation between the two traits was evident in the tiger pufferfish populations • Genetic variances for these traits may increase in the tiger pufferfish fed LFM diet [ABSTRACT FROM AUTHOR]

The present study was to investigate the effects of Methylococcus capsulatus protein (MCP) replacing fish meal on the growth performance, immunity, and intestinal health of Chinese soft-shelled turtle (Pelodiscus sinensis). Four isonitrogenous (47.00% crude protein) and isolipidic (6.00% crude lipid) diets were formulated for an 8-week feeding trial. The fish meal group (FM) contained 55% fish meal. MCP was used to replace 10%, 15%, and 20% of the fish meal in the FM group to create MCP10, MCP15, and MCP20 treatment groups. No significant differences were observed in the weight gain, feed conversion efficiency, physical indicators, or muscle amino acid composition among all diet treatments (P > 0.05). The MCP15 group showed the best growth performance. There were no significant differences in serum biochemistry among the groups (P > 0.05), except for aspartate aminotransferase, which exhibited a significant linear increase trend with the increase of MCP replacement level (P = 0.049). In the MCP20 group, the complement C3 content, immunoglobulin M content, and lysozyme activity in serum were significantly lower than those in the FM, MCP10, and MCP15 groups (P < 0.05), showing a quadratic relationship characterized by an initial increase followed by a decrease as the MCP level in the feed increased (P < 0.05). The intestinal morphology in all treatment groups appeared normal and the expression levels of intestinal inflammatory cytokines showed no significant differences (P > 0.05). The community structure of the intestinal microbiota, as well as the phylum and genus composition underwent significant alterations in response to the MCP supplementation. The recommended practice for Chinese softshell turtle diet involves substituting 15% MCP for fish meal, which enhances growth, boosts immune response, and does not adversely affect serum biochemistry, amino acid composition, or intestinal health. • Methylcoccus capsulatus protein (MCP) replacing fish meal (FM) did not affect growth performance of Pelodiscus sinensis. • The intestinal health and muscle amino acid composition were not changed by MCP substitution. • MCP replacing 20% FM tended to suppress immune responses and antioxidant ability. • The intestinal microbial community structure was markedly altered by MCP inclusion. • The MCP induced significant alterations in the phylum and genus of intestinal microbiota. [ABSTRACT FROM AUTHOR]

Probiotics are important for the normal physiological functions of fish and are used as feed additives in many aquatic animals. The purpose of this study is to explore the effects of dietary bacterial culture of fengycin-producing Bacillus subtilis (B. subtilis) on growth performance, intestinal and hepatopancreas health, intestinal microbiota and disease resistance of common carp (Cyprinus carpio). Three diets were formulated with supplementation of bacterial culture of fengycin-producing B. subtilis at 0, 0.3 and 0.5 g/kg levels, and these diets were defined as control, BS0.3 and BS0.5, respectively. After 6-week feeding, the infiltration of inflammatory cells was improved in the BS0.3 and BS0.5 groups. And the anti-inflammatory cytokines (interleukin (IL)-10 and tumor growth factor β (TGF-β) were prominently increased in the hepatopancreas of fish fed with dietary B.subtilis diets (P < 0.05). The activity of lysozyme, the levels of complement component (C) 3 and C4 were remarkably increased in the hepatopancreas and intestine of fish fed with B.subtilis supplemented diets (P < 0.05). Histological (intestinal villi height was increased in BS0.3 and BS0.5 groups) (P < 0.05) and the expression of the gut physical barrier-related genes (Zona occludens-1 (ZO-1) and occludin) were increased in the B.subtilis supplemented groups (P < 0.05). The expression of pro-inflammatory cytokines (IL-1β , IL-6 and tumor necrosis factor α (TNF-α) and anti-inflammatory cytokines (IL-10 and TGF-β) were remarkably up-regulated in the intestine of fish fed with BS0.3 diet (P < 0.05), while the expression of IL-6 was remarkably diminished in the intestine of fish fed with BS0.5 diet (P < 0.05). Besides, the intestinal microbiota analysis illustrated that in the intestine of the fish groups fed with BS0.3 and BS0.5 diets, the abundance of Fusobacteriota and Cetobacterium were prominently increased (P < 0.05). After challenged with Aeromonas veronii Hm091, the survival rate of fish fed with BS0.3 diet was markedly improved (P < 0.05). Based on these results, supplementation of bacterial culture of fengycin-producing B. subtilis at a level of 0.3 g/kg has beneficial effects on immunity, intestinal microbiota, and disease resistance of common carp. • BS0.3 and BS0.5 diets significantly improved the non-specific immunity of common carp. • BS0.3 and BS0.5 diets significantly improved the intestinal and hepatopancreas health. • BS0.3 diet improved the composition of intestinal microbiota, and enhanced the disease resistance of common carp. [ABSTRACT FROM AUTHOR]

Fish meal is commonly used in the diets of fish, but its high cost and sustainability as a feed ingredient raise concerns. In order to reduce dependence on fish meal, proteins from plant sources are increasingly being recommended as an alternative ingredient in fish diets. The paper aims to examine whether risk attitudes and time preferences influence the decision to choose feed protein sources for intensively farmed fish. Using measures based on behavioural economics theories, we elicit risk attitudes and time preferences of 100 Nigerian fish farmers and estimate a double hurdle regression by assuming that fish farmers make their feed protein substitution decisions in two steps. The results indicate that risk-seeking farmers are less likely to substitute (risk-increasing) fish meal for plant-based proteins in fish feed. There is no statistically significant effect of time preference on the decision to substitute fish meal for plant-based proteins. Other results show that a higher level of education and income and a larger farm size positively influenced the decision to substitute fish meal for plant-based proteins, while male farmers were less likely to substitute fish meal for plant-based proteins. These findings suggest that farmers' risk attitudes, education, income, farm size, and gender are critical factors that policymakers and stakeholders should consider in interventions to encourage farmers to transition to more sustainable feed input. • There is a need to reduce dependence on fish meal due to high cost and unsustainability. • The paper extends insights from behavioural economics to aquaculture management. • We posit attitudes to risk and time drive the decision to substitute fish-meal. • Being risk-seeking reduces the probability of substituting fish-meal with plant proteins. • Time preference had no significant effect on the decision to substitute fish meal. [ABSTRACT FROM AUTHOR]

Consumption of fish and shellfish exposed to high levels of pollutants from environmental sources and anthropogenic activities can lead to the accumulation of toxic elements in humans. Mercury (Hg), cadmium (Cd), lead (Pb), and arsenic (As) can cause serious health problems in consumers of all ages. This study examined toxic element levels and associated health risks in gilthead seabream, European seabass, and Mediterranean mussels from aquaculture farms which represent commercially important species exported from Türkiye. Fifty-one samples were analysed for Hg, Cd, Pb, and As. In general, the annual average concentrations of toxic elements in seabream, seabass, and mussel samples were generally below the established limits. On a seasonal basis, it was determined that the limit value for Cd recommended by the EU (0.05 mg/kg) was exceeded for sea bream and sea bass species of only one farm, with values of 0.080–0.088 mg/kg, respectively, in the summer season. The Total Target Hazard Quotients (TTHQ) and Target cancer Risk (TR) indexes were calculated for the European Union (EU) and Turkish populations to assess consumer health and safety. Consequently, fish and mussel samples obtained from aquaculture farms were highly reliable and found to be safe for consumption. The exceeding of Cd levels in fish beyond the established limit in a single season on one farm demonstrates the necessity for regular monitoring of parameters. • Toxic element levels in the aquaculture sector were evaluated. • Risk levels of marine aquaculture species in Türkiye based on consumption were determined. • Health risks evaluated for EU and Turkish consumers. • Aquaculture seafood meets safety standards with a low risk of element accumulation. [ABSTRACT FROM AUTHOR]

Despite the growing use of hybrid catfish (Ictalurus punctatus × I. furcatus) in the aquaculture industry, few studies have compared their physiological performance with more commonly reared channel catfish (I. punctatus) and their other parent stock, blue catfish (I. furcatus). An understanding of metabolic scope and swimming performance, particularly in elevated water temperatures, is important because these metrics directly relate to the overall performance or fitness of an organism. Therefore, metabolic scope, the difference between standard metabolic rate (SMR) and maximum metabolic rate (MMR), and swimming performance in channel, blue, and hybrid catfish were compared using intermittent and swim-flume respirometry coupled with U crit protocols at moderate (23 °C) and high (33 °C) temperatures. It was hypothesized hybrid catfish would have larger metabolic scope and greater swimming performance than channel and blue catfish due to heterosis from hybridization. Hybrid catfish SMR did not differ from blue catfish, while hybrid catfish had higher MMR, larger metabolic scope, and better swimming performance than channel and blue catfish. These results indicate hybrid catfish outperform channel and blue catfish, in terms of swimming performance, presumably due to larger metabolic scope over moderate to high temperatures. • Hybrid catfish outperform channel and blue catfish due to larger metabolic scope. • Hybrid catfish have better swimming performance than channel and blue catfish. • Temperature has a profound effect on metabolic rate but not swimming performance. [ABSTRACT FROM AUTHOR]

To meet the growing demand for aquatic products, the aquaculture sector is expanding, including organic aquaculture. One of the main challenges in this industry is the development of suitable fish feeds. EU regulations have made recommendations, including the incorporation of fishmeal from organic aquaculture trimmings. However, the use of such fish meal may pose issues due to lower protein content and elevated phosphorus concentrations that could conflict with national environmental regulations. Thus, there is a pressing need for innovative research to formulate environmentally friendly feeds for organic aquaculture. This study aims to evaluate the feasibility of utilizing an innovative organic feed derived from trimmings (substitution of 64.3% of dietary fish meal trimmings with fishmeal protein concentrate from trimmings) for rainbow trout (Oncorhynchus mykiss). This study assessed the impact of this innovative diet on rainbow trout welfare over a two-month period in real-farming conditions, using: (i) growth parameters, (ii) external morphological damages, (iii) swimming activity, used as a proxy for energy expenditure, and (iv) blood and liver health and welfare indicators. Given that fish swimming activity was evaluated using surgically implanted accelerometer tags, we also investigated the potential adverse effects of implanting these tags on fish welfare. Our findings indicate that accelerometer implantation did not significantly affect fish welfare, but a 18.6% reduction in specific growth rate was shown in tagged fish compared to their non-tagged counterparts. Importantly, the innovative diet did not impair health and welfare indicators of blood and liver or lead to external morphological abnormalities. An increased energy expenditure in fish fed the innovative diet compared to those on a control diet was, however, shown, but there was no observable impact on growth performance. The use of this innovative diet may offer a viable solution to reduce the release of soluble phosphorus into the environment while maintaining appropriate standards for fish growth and welfare in organic conditions. Nevertheless, long-term consequences should be explored. • We tested the impact of an innovative and environmentally-friendly organic feed. • Rainbow trout welfare was monitored under real farming conditions. • A low impact of implanted accelerometer tags was shown on fish welfare. • The innovative diet did not compromise the health and welfare of the fish. • The novel diet appeared promising, but long-term consequences need to be assessed. [ABSTRACT FROM AUTHOR]

The influence of different diet formulations during gonadal maturation on reproductive efficiency and embryo quality in Atlantic salmon was investigated. Four diets were compared: Diet 1 contained exclusively marine-origin protein and lipid ingredients, Diet 2 involved substituting 65% of the protein and 51% of the lipid by terrestrial animal and vegetable sources, Diets 3 and 4 were commercial diets. The results showed a higher number of spawned females in the groups of fish fed with diets 1 (73.3%) and 2 (66.7%) than those fed with diets 3 (53.3%) and 4 (50%). Spawning weight and total fecundity did not differ between diets, but a strong correlation was found between these variables, independent of diet. There were no significant differences in zootechnical parameters, but the groups of fish fed the commercial diets tended to have greater weight and length. Oocyte diameter did not differ, but percent hydration was statistically different between groups fed diets 2 and 3. Although there was no difference in embryonic malformations between diets, the presence of microphthalmia correlated negatively with oocyte diameter and percent hydration in embryos obtained from the group of fish fed with Diet 3. Blastomere symmetry and survival at 280 ATU showed statistical differences between diets 3 and 4. Using high-nutritional-value marine ingredients (Diet 1) during gonadal maturation improves reproductive performance in female Atlantic salmon. Enhancing fish broodstock nutrition through targeted research can optimize reproductive success, increase yields, and promote sustainable aquaculture practices. • Diet composition has effects on reproduction in Atlantic salmon. • Marine ingredients optimized maturation rates enhancing reproductive efficiency. • Feeding strategies during gonadal maturation improve rate and spawning timing. [ABSTRACT FROM AUTHOR]

Recently identified and characterized in rainbow trout (Oncorhynchus mikyss), the main gustatory receptors for fatty acid, known as free fatty acids receptor (FFAR) 1 and 2, may play a crucial role in nutrient detection and regulation of feeding behavior. However, our understanding of their post-prandial roles remains limited. This study investigates the impact of a single meal (acute effect) with an alternative plant-based diet (vegetal diet, V diet devoid of fish meal and fish oil) on the food detection mechanisms in trout. After 30 days of feeding with commercial-like diet (C diet made up of a mix of fish meal, fish oil and plant ingredients) followed 5 days of fasting, we conducted a post-prandial kinetic experiment after single meal with C or V diet. We assessed the expression pattern of ffar genes, their associated signaling pathways (calcium and indolamine pathways) in the tongue along with the expression pattern of appetite-regulating neuropeptides in the hypothalamus. Additionally, we evaluated central activity through brain activity markers in the telencephalon of trout at various post-meal time points, including 20 min, 2, 6, 10 and 24 h. Our results revealed that the diet nature (C vs V) influences the expression of ffar genes, while some paralogs of ffar2 (ffar2a2 and ffar2b1.2) were early up-regulated by V diet, ffar2b1.1 and ffar1 were latter up-regulated by C diet. Differential regulations in the tongues of V diet fish were also observed on calcium signaling and an early alteration in serotonin turnover. The expression increase of neuropeptide npya from 6 to 10 h after meal, could suggest a greater sensation of hunger in fish fed the C diet. Finally, our findings suggest that rainbow trout exhibit a keen ability to detect a novel feed after a single meal with V diet at the brain level, particularly in areas associated with decision-making and behavior control. Altogether, results not only show that the integrative feeding response appears to be dysregulated by V diet, but also highlight the noteworthy sensitivity of nutrient detection mechanisms in rainbow trout to new food sources. FFARs may play a role in finely discerning diets with varying levels of ω-3 LC-PUFAs in rainbow trout. This heightened detection sensitivity holds the potential to significantly influence the regulation of feeding behavior and food detection in farmed fish. [Display omitted] • Trout possess an oro-sensory nutrient detection mechanism that exhibits significant and distinct responses to a novel diet. • A single meal of a plant-based diet had an early impact on postprandial food detection in rainbow trout. • Free fatty acid receptors could play a role in finely detecting diets with varying levels of ω-3 LC-PUFAs in rainbow trout. [ABSTRACT FROM AUTHOR]

Arachidonic acid (ARA) is becoming increasingly important due to significant reductions in fishmeal (FM) and fish oil (FO), the primary sources of ARA, in aquafeeds. ARA is an essential omega-6 fatty acid in some fish species and plays a wide range of physiological roles. However, studies reported to date have demonstrated contrasting findings concerning the effects of ARA in fish growth and health, regardless of the fish's trophic level. Additionally, limited research has addressed energy allocation during reproduction and growth in sub-adult rainbow trout as they approach reproductive maturity. Therefore, a study was conducted to evaluate the effects of different levels of ARA on growth performance, the fatty acid composition of whole-body and ovary, intestinal inflammatory gene expression, gut histology, antioxidant activity, and non-specific immunity in sub-adult rainbow trout (Oncorhynchus mykiss). Four isonitrogenous (51% crude protein), isolipidic (15% crude lipid), and isocaloric (23 MJ/kg) diets were formulated and supplemented with ARA-enriched oil (40%), resulting in analyzed ARA levels of 0.10 (ARA 0.10), 3.95 (ARA 3.95), 7.67 ARA(7.67), and 14.8% (ARA 14.8) of total fatty acid, respectively. Rainbow trout (307 ± 3.64 g) were fed to apparent satiation three times a day for 12 weeks to assess growth performance, feed utilization, and intestinal inflammatory response. The fish were then exposed to acute stress to evaluate circulating cortisol, prostaglandin E 2 , antioxidant activity, and non-specific immune response. The 12-week growth trial demonstrated that dietary ARA did not affect rainbow trout growth performance and feed utilization during the final grow-out. Whole-body fatty acid profiles reflected those of the diets except for eicosapentaenoic acid (EPA) content being significantly lower in the ARA 14.8 group than in the ARA 0.10 and ARA 3.95 groups. EPA and docosahexaenoic acid (DHA) contents in the ovary were less affected by dietary ARA supplementation, likely reflecting the selective deposition of those fatty acids in embryonic development. The expression of tnf-α was significantly downregulated in ARA 7.67 and ARA 14.8 groups relative to other treatment groups, and only distal intestinal villus height was significantly increased in the ARA 3.95 group, suggesting that dietary ARA supported intestinal health. Plasma superoxide dismutase, catalase, and lysozyme activity significantly increased in both pre- and post-stress groups due to incremental increases in dietary ARA. These results suggest that a moderate level of dietary ARA in low FM and FO-free enhances innate immune function and antioxidant responses while supporting intestinal health in sub-adult rainbow trout. • Dietary ARA did not affect sub-adult trout growth, feed utilization and survival. • Dietary ARA increased antioxidant activities and non-specific immune parameters. • A moderate level of ARA in a low FM/FO-free diet improved intestinal health. [ABSTRACT FROM AUTHOR]

In recent years, the pursuit of sustainable aquaculture practices has focused on alternatives to fisheries-derived ingredients, to avoid economic and environmental unsustainability. Low-trophic organisms, such as polychaetes, could be a suitable alternative to fishmeal due to their high protein content. This study aimed to investigate the feasibility of replacing fishmeal with the polychaete meal (Alitta virens ; PM) in diets for European seabass (Dicentrarchus labrax; Wi, ∼14.5 g). Four isoproteic (51% dry matter, DM) and isolipidic (17% DM) diets were fed to seabass juveniles: a fishmeal-based diet (FM) and three experimental diets with PM at inclusion levels of 2.5% (PM2.5), 5% (PM5), and 10% (PM10), replacing 10%, 20% and 40% of fishmeal, respectively. After 93 days of feeding, the effects of the PM on growth, digestibility, nutrient utilization, plasma metabolites, liver lipogenic activity, and anterior intestine histomorphology were analyzed. The environmental impact of all diets was also assessed. All diets were well-accepted by the fish, and promoted equal growth performance, ensuring high feed efficiency. The muscle EPA + DHA content in all dietary groups exceeded the recommended levels for human consumption. Hepatic lipogenesis and plasma triglyceride and non-esterified fatty acids (NEFA) levels were increased in fish fed PM2.5, suggesting that the PM promoted alterations in lipid metabolism, especially at low inclusion levels. PM2.5 also seemed to enhance the absorption capacity of the anterior intestine by increasing villus length and goblet cells number/area, albeit without impacting nutrient digestibility and growth performance. Furthermore, copper digestibility increased with higher levels of PM inclusion. The assessment of environmental sustainability indicated that the experimental diets incorporating PM present a more sustainable option compared to fishmeal. Overall, this study demonstrated that PM can serve as a sustainable alternative to fishmeal, replacing it by up to 40%, without compromising European seabass growth and nutrient utilization, while guaranteeing a high nutritional quality fillet for human consumption. The best environmental performance could be achieved with a diet comprising 5% to 10% (w /w) PM content. However, further research is needed to understand the underlying mechanisms of PM's effects on intermediary metabolism and its potential as a functional ingredient. • Polychaeta meal (PM) offered a more environmentally sustainable substitute to fishmeal in European seabass diets. • Up to 40% fishmeal replacement by PM had no effect on fish growth or feed efficiency. • Muscle EPA + DHA content in all groups exceeded the recommended levels for human consumption. • PM2.5 led to significant alterations in European seabass lipid metabolism. • PM5-fed fish showed the highest lipid, protein and energy gain among all experimental groups. [ABSTRACT FROM AUTHOR]

The present work aimed at evaluating if a mixture of different fat sources could replace fish oil in diets. Consequently, a mixture of poultry, palm kernel, and microalgae fat sources was blended (25, 71 and 4%) to replace fish oil at four different levels; 0 (Control), 25 (L-Mix), 50 (M-Mix), and 100% (H-Mix). Then, four different diets with defatted poultry by-product meal (PBM) and fish meal (FM), were used to formulate isoproteic and isolipidic diets. Juveniles of Litopenaeus vannamei (2.2 ± 0.3 g) were aleatorily distributed into 12 experimental units (500 L) in a recirculation system (RAS) with temperature controlled (28 °C) and constant aeration. After seven weeks of the experimental procedure, differences were found only in the survival rate and hepatosomatic index. The survival rate was 92% for M-Mix and H-Mix, while 70% was registered in the Control group. The hepatosomatic index was higher in the H-Mix (5.5) than in the rest of the dietary groups, with a minimum amount in the Control group (3.7). Even if no significant differences were found in the feed conversion ratio using an ANOVA (P = 0.5), a significant linear correlation revealed that a lower FCR (1.08) was registered in H-Mix compared to the Control (1.8). The fatty acid analysis demonstrated that those shorter than 14 carbons were efficiently utilized, as lauric acid (12:0) was observed lower in the hepatopancreas than in the supplied diets. In general, the rest of the fatty acids were used as reflected by their content of diets. On the contrary, the arachidonic acid (ARA) was efficiently accumulated in shrimps fed the three experimental diets despite its low concentration in the experimental treatments. In contrast, EPA and DHA were slightly lower than in the corresponding dietary treatments. It is concluded that the fat mixture containing poultry and palm kernel fats, with a DHA source from microalgae, resulted in a better survival rate and equal growth rate to shrimp reared with diets containing fish oil. Notwithstanding study results, it is recommended to research with higher amounts of medium-length fatty acids in diets together with attractants to increase feed ingestion. • The fat mixture (poultry, palm kernel, and DHA), can substitute fish oil with a better feed conversion ratio. • The lauric acid (C:12) is efficiently used than the rest of the fatty acids in the diet. • The fat mixture shows a positive relationship to the hepatosomatic index, resulting in a better reserve of fatty acids. • The fat mixture used shows a positive relationship to the survival rate of shrimp. [ABSTRACT FROM AUTHOR]

This study assessed the impact of replacing fish meal (FM) with a blend of corn gluten meal and meat meal (BCM) at a ratio of 1:2 on the growth performance, digestive enzyme activity, and nonspecific immune response of juvenile black rockfish (Sebastes schlegelii). Seven experimental diets were formulated. The control (BCM0) diet contained 65% FM. Subsequently, 10, 20, 30, 40, 50, and 60% FM in BCM0 diet were replaced with BCM, referred to as the BCM10, BCM20, BCM30, BCM40, BCM50 and BCM60, respectively. Each diet was randomly assigned to triplicate groups of 30 rockfish (initial body weight: 3.6 ± 0.01 g) for 8 weeks. The BCM0–BCM50 diets resulted in no significant differences in final body weight (FBW), weight gain (WG), and specific growth rate (SGR), whereas the BCM60 diet led to the lowest FBW, WG, and SGR. The feed consumption and feed efficiency of rockfish fed BCM10–BCM50 diets did not differ significantly from those of rockfish fed the BCM0 diet. Intestinal trypsin and lipase activities showed a linear decrease with increasing substitution levels of BCM in the experimental diets. Moisture levels increased with elevated BCM replacement in diets, whereas crude protein and lipid levels decreased with increased BCM replacement. Whole-body amino acid profiles of rockfish, except for glycine and proline content, were not significantly affected by diet. However, lysozyme and catalase activities exhibited quadratic responses to increasing dietary BCM levels, and superoxide dismutase activity and glutathione content showed a negative linear response. Overall, these results show that a blend of corn gluten meal and meat meal can replace up to 50% of dietary FM without adversely affecting the growth performance of juvenile rockfish. • A blend of corn gluten meal and meat meal (BCM) in a 1:2 ratio is a good protein source of protein for black rockfish. • Substituting up to 50% FM with BCM did not have adverse effects on growth and feed utilization. • Intestinal trypsin and lipase activities showed a linear decrease with increasing substitution levels of BCM. • With increased dietary BCM, plasma superoxide dismutase activity and glutathione concentration decreased linearly. [ABSTRACT FROM AUTHOR]

In this study, we partially replaced fishmeal (FM) with moringa protein hydrolysate (MPH) in the diet of Nile tilapia, Oreochromis niloticus, in a ten-week feeding trial. We evaluated the consequences of this substitution on the growth, digestive enzyme activity, economic efficiency, immune status, and expression of immune genes, protein transporters, and insulin growth factor-1 (IGF-1). Fish (n = 225, 36.38 ± 0.06 g/fish) were randomly assigned to five groups with five replacement levels of MPH: 0, 15, 30, 45, and 60% (MPH0, MPH15, MPH30, MPH45, and MPH60). The results showed a linear increase in the growth parameters by replacing FM with MPH. A rise in the serum level of growth hormone and a reduction in the leptin hormone and glucose levels were observed with increasing the MPH replacement level. Higher amylase activity was detected with MPH replacement, with the highest activity noticed in the MPH45 group. The protease activity was linearly increased in the MPH45–60 groups. We reported significant up-regulation in the expression of IGF-1 and amino acid and peptide transporters in MPH groups. The immune indices (serum nitric oxide level, lysozyme activity, and phagocytic activity) and immune-related gene expression were linearly up-regulated by MPH replacement up to the 45% replacement level then decreased in the MPH60 group but still higher than the control group. FM replacement with MPH increased the Nile tilapia resistance to Aeromonas sobria challenge. In conclusion, MPH can replace FM up to 60% for good performance and immune status of fish. • Moringa protein hydrolysate (MPH) can replace Fishmeal (FM) in Nile tilapia diets by up to 60%. • The inclusion of MPH increased fish growth and digestive enzyme activity. • MPH improved protein absorption by increasing amino acid expression and peptide transporters. • Dietary MPH improved the non-specific and innate immunity by increasing the NO level, lysozyme, and phagocytic activity. • FM replacement with MPH showed upregulation of the immune-related gene expression and resistance against A. sobria. [ABSTRACT FROM AUTHOR]

The study estimated the effect of substituting fishmeal with cottonseed protein concentrate (CPC) in practical diets on growth performance, flesh quality and metabolomics of largemouth bass (Micropterus salmoides). In a basal diet with fishmeal inclusion of 400 g/kg, five diets were formulated with CPC inclusion to isoproteicly replace 0%, 15%, 30%, 45% and 60% of dietary fishmeal, correspondingly, the fishmeal inclusion was 400 g/kg (FM40), 340 g/kg (FM34), 280 g/kg (FM28), 220 g/kg (FM22), 160 g/kg (FM16), respectively. Then, the five diets were fed to largemouth bass with initial body weight of 75.0 g for 12 weeks. The results showed that 15% and 30% of dietary fishmeal could be successfully replaced by CPC without significant effects on the weight gain (WG) and feed conversion ratio (FCR), while the WG was decreased and FCR was increased when 45% and 60% of dietary fishmeal were replaced by CPC (P < 0.05). With the increase of replaced fishmeal level by CPC, the flesh hardness and the content of heat-insoluble collagen showed a significantly negative linear trend (P < 0.05), while flesh drip loss (at 12th h and 24th h), n-6 polyunsaturated fatty acid, total free amino acids and flavor amino acids contents showed a significantly positive linear trend (P < 0.05). FM22 and FM16 groups showed lower flesh hardness and higher drip loss (24th h) than FM40 group (P < 0.05). In muscle histology and metabolomics, FM16 group presented higher myofiber density and lower myofiber diameter than FM40 group. A total of 97 differential metabolites were detected between FM16 and FM40 groups, which mainly enriched in pathways as biosynthesis of amino acid, protein digestion and absorption, D-arginine and D-ornithine metabolism, histidine metabolism, alanine, aspartate and glutamate metabolism. Conclusively, in a practical diet containing 400 g/kg fishmeal, CPC could replace 30% fishmeal (120 g/kg) without significant impacts on growth, flesh composition, texture, flavor and muscular tissue structure, and high fishmeal replacement (≥ 45%) decreased growth performance and flesh quality of largemouth bass. • Cottonseed protein concentrate could replace 30% dietary fishmeal (120 g/kg) for largemouth bass. • High fishmeal replacement (≥ 45%) by CPC decreased growth and flesh quality. • High replacement of fishmeal with CPC affected amino acid and lipid metabolism. • Dietary CPC inclusion would not cause the deposition of free gossypol in flesh. [ABSTRACT FROM AUTHOR]

Defatted black soldier fly (Hermetia illucens) (DHI) and poultry by-product meal (PBM) were used in tandem to substitute fishmeal in diets for European perch (Perca fluviatilis) in the current study. Four isoproteic (52%), isolipidic (14%), and isoenergetic (22 Mj/kg) diets (abbreviated diets: COM0, COM50, COM75, and COM100) were formulated, in which DHI replaced 0, 50, 75 and 100% fishmeal with the complementarity of PBM, and fed to triplicate groups of European perch (54.43 ± 0.35 g) for 90 days. Dietary treatments had no effect on growth performance indices of final body weight (P = 0.209) and survival (P = 0.155), feed utilization as illustrated by daily feed intake (P = 0.595), feed conversion ratio (P = 0.073), and condition factor (P = 0.209). On the other hand, specific growth rate and weight gain were significantly affected by treatments (P = 0.011 and 0.012, respectively) and were DHI level-dependent (P = 0.006 and 0.010, respectively). Protein digestibility was statistically greater in COM75 and COM50 than in COM100 (P < 0.001). Ash digestibility was DHI-inclusion dependent (P = 0.001). Dietary complementarity significantly impacted the colour (P < 0.05), dripping loss (P = 0.008), moisture (P = 0.022), and docosahexaenoic acid (P < 0.001) of perch fillets. DHI-PBM substitution of 75% fishmeal did not significantly increase nitrogen waste (P > 0.05), but did at 100% replacement (P = 0.03). In contrast, the diet treatments sustained total solid and phosphorus waste relative to the control group (P = 0.18 and 0.107, respectively). Dietary complementary, on the other hand, resulted in a greater impact on global warming potential (P = 0.019) and water use (P < 0.001), but did not affect land use (P = 0.55). The use of DHI and PBM in diets for European perch offered great benefit concerning less reliance of aquaculture on forage fish from marine sources as illustrated by the economic Fish-in Fish-out ratio, which significantly decreased with increasing level of complementarity (P < 0.0001), and reduced food-feed competition. The results from the present study revealed that the combination of DHI and PBM can replace fishmeal at as high as 50% while favoring all metrics relative to the control group. • Black soldier fly (Hermetia illucens) (DHI) and poultry by-product meal (PBM) in diets for European perch (Perca fluviatilis) was investigated. • Dietary complementarity sustained the production performance of perch. • Dietary complementarity did not alter histological indices in liver and intestine of perch. • Dietary complementarity sustained total solid and phosphorus waste relative to the control groupat 75% fishmeal replacement. • Dietary DHI and PBM significantly reduced economic Fish-in Fish-out and food-feed competition. [ABSTRACT FROM AUTHOR]

A 56-day feeding trial was performed to compare the impacts of replacement of dietary fishmeal by soybean meal (SM) or extruded soybean meal (ESM) on the growth performance and muscle quality of olive flounder (Paralichthys olivaceus) (initial weight: 6.32 ± 0.01 g). Nine isonitrogenous and isolipidic diets were prepared by substituting 0% (FM, control), 12% (SM12/ESM12), 24% (SM24/ESM24), 36% (SM36/ESM36) and 48% (SM48/ESM48) of fishmeal with SM or ESM respectively. Results indicated that contents of anti-nutritional factors (trypsin inhibitors, glycinin and β-conglycinin) in ESM were significantly lower than those in SM. The weight gain rate, specific growth rate, feed efficiency ratio, protein efficiency ratio, activities of intestinal trypsin and lipase, as well as expressions of myogenic regulatory factors (myf5 , myod and mrf4) and protein synthesis-related genes (akt , pi3k , tor and s6) in fish muscle decreased linearly and quadratically with increasing replacement levels of dietary fishmeal by SM or ESM. Expressions of mstn and protein degradation-related genes (foxo1 , murf-1 , mafbx , capn2 and ctsl) in muscle showed a trend opposite to growth parameters responding to dietary SM or ESM levels. Significant differences in all the above parameters were observed in the SM36, SM48 and ESM48 groups, accompanied by the declines in contents of most muscle free amino acids. The increase of dietary fishmeal replacement level by SM linearly and quadratically decreased muscle hardness, water holding capacity (WHC), pH and total collagen content. Markedly lower values were found in the SM36 and SM48 groups. However, ESM could replace up to 36% of dietary fishmeal without significantly impacts on above muscle quality parameters. Additionally, reduced myofiber density and sarcomere length were observed in the SM36, SM48, ESM36 and ESM48 groups. However, at the same substitution level, dietary ESM relieved the effects of SM on myofiber morphology to some extent. In conclusion, according to broken-line regression on SGR, the optimal replacing level of fishmeal by SM and ESM for olive flounder was 22.07% and 34.39% respectively. The improved replacement level of fishmeal by ESM, in terms of fish growth, muscle hardness and WHC, may be due to the fact that dietary ESM alleviated the adverse impacts of SM on digestive enzyme activity, muscle growth-related genes expression, muscle pH, collagen content and myofiber morphology of fish. • Effects of dietary soybean meal (SM) or extruded soybean meal (ESM) on olive flounder were compared. • Based on broken-line regression on SGR, optimal replacing level of fishmeal by SM and ESM was 22.07% and 34.39% respectively. • Reduced growth and muscle quality were observed when replacement of fishmeal by SM exceeded 24% or by ESM exceeded 36%. • Dietary ESM alleviated adverse impacts of SM on digestive enzyme and muscle growth-related gene, thus improving fish growth. • ESM alleviated adverse impacts of SM on muscle pH, collagen content and myofiber morphology, thus improving muscle quality. [ABSTRACT FROM AUTHOR]

The effects of dietary Hermetia illucens (HI) larvae meal on growth, plasma biochemistry and gut microbiota was tested in gilthead sea bream. Four isonitrogenous and isolipidic extruded diets (50% protein; 14% lipid) with different levels of HI larva meal (0% CTRL, 5% HI5, 10% HI10, and 15% HI15) in partial substitution to fish meal (FM) were administered to triplicate fish groups over 113 days. Diets were designed to partially replace FM, using FM level for practical application. No significant differences (p > 0.05) were observed in terms of final body weight, specific growth rate (SGR), feed intake (FI), feed conversion rate (FCR) as well as feed efficiency parameters such as protein efficiency ratio (PER), gross protein efficiency (GPE), gross lipid efficiency (GLE). At the end of the trial there were not significant differences on growth, feed intake, feed conversion rate and protein efficiency. Among over 20 plasma parameters analyzed, HI inclusion level reduced iron (Fe), potassium (K), creatinine (CREA), aspartate aminotransferase (AST), alanine amino transferase (ALT), creatine kinase (CK), alkaline phosphatase (ALP), lactate dehydrogenase (LDH). The reduction of AST, ALT and ALP might suggest a potential beneficial role of HI for liver integrity and functionality. Concerning gut microbiome (GM) layout, HI was able to induce a shift in the GM structure at any inclusion level considered compared to the control diet increasing the abundance of Bacillaceae (mainly Bacillus and Oceanobacillus) and Paenibacillaceae (Paenibacillus). Taxa that can be involved in chitin degradation and has been recently recognized as novel probiotics for aquaculture. In conclusion, the results of feed intake, growth, feed utilization and plasma biochemistry indicate that HI larvae meal can be successfully incorporated up to 15% in practical aquafeed diets to partially replace FM without any negative effects on growth and feed efficiency. Beyond being a valid alternative protein source for fish meal replacement in this species, it displays gut health functional properties already at low inclusion level. • Partial replacement of FM with HI larvae meal did not affect growth and feed utilization. • HI was able to induce a shift in the GM structure at any inclusion level. • HI increased the abundance of Bacillus and Paenibacillus. [ABSTRACT FROM AUTHOR]

Yellowtail kingfish have a poor faecal integrity when fed with pelleted diets which may be due to the presence of dietary starch. Moreover, whether dietary starch interacts with plant protein ingredients, is not known. In this study, we investigated the effect of dietary starch level, protein source and their interaction effect on faecal waste production and characteristics (visual appearance, faecal removal efficiency and particle size distribution (PSD)). Four diets were formulated according to a 2 × 2 factorial design (starch level × protein source). The effect of starch level was tested by either including 0% (LS - low starch , 4% starch) or 20% gelatinized wheat flour (HS - high starch, 20% starch). FM diets contained fish meal as protein source, whilst at FM/P diets approximately 65% of the fish meal was replaced by plant protein ingredients. Twelve tanks were stocked with 21 fish (mean initial weight 53 g) and fish performance, nutrient digestibility, faecal waste production and characteristics were evaluated over a 36-day experimental period. Both starch level and protein source affected the organic matter digestibility (p < 0.05). The effects of starch and protein source were additive regarding macro nutrient digestibility indicated by the absence of an interaction effect (p > 0.05). Growth was similar between the FM and FM/P at low starch diets (p < 0.05), but was reduced at the FM/P at high starch inclusion level (p < 0.05). The high starch and FM/P diets resulted in more faecal waste production (p < 0.05). Faecal integrity of yellowtail kingfish was adversely affected by starch inclusion. Fish receiving low starch diets excreted faecal pellets and short strings, while faecal waste collected from fish receiving high starch diets was classified as inconsistent. This was also reflected in a higher faecal removal efficiency and larger faecal PSD for fish receiving the low starch diets compared to the high starch diets (p < 0.05). No protein source or interaction effect was observed for faecal removal efficiency (p > 0.05). Consequently, lowering starch level and excluding plant protein ingredients reduced the amount of non-removed faeces by 71.1% and 30.6%, respectively. In summary, our study showed that the reduction of dietary starch offers possibilities to replace fish meal with plant protein ingredients without limiting growth performance in yellowtail kingfish. Moreover, lowering dietary starch level may have the potential to reduce solid loading in recirculating aquaculture systems for yellowtail kingfish. • Yellowtail kingfish fed high starch diets produce more faecal waste. • High starch diets induce poor faecal integrity in yellowtail kingfish. • Low dietary starch inclusion results in faecal pelleting. • Faecal removal efficiency by settling is reduced by increasing starch level. • Plant protein inclusion does not negatively affect growth at low starch levels. [ABSTRACT FROM AUTHOR]

Spirulina, Arthrospira platensis , contains high levels of protein and lutein. To evaluate nutritional, pigmentation, and antioxidation effects of A. platensis , a total of 900 juvenile yellow catfish (Pelteobagrus fulvidraco) were divided into 18 tanks (3 tanks/treatment, 50 fish/tank) and fed a diet supplemented with A. platensis for 50 days. A. platensis was used in quantities of 0, 57.6, 115.1, 172.7, 230.3, and 287.9 g kg−1 for experimental diets to replace fishmeal protein at levels of 0 (AP0), 20% (AP20), 40% (AP40), 60% (AP60), 80% (AP80), and 100% (AP100). Results revealed that substituting up to 80% of fishmeal by A. platensis biomass did not have a negative effect on fish growth, feed utilization, or apparent digestibility. However, significantly lower growth rates were observed when 100% of the fishmeal was substituted (P < 0.05). A. platensis replacement groups led to an increase in skin yellowness and dose-dependent enrichments of total lutein in dorsal skin, abdominal skin, and liver tissues (P < 0.05). There were similar enhancements observed in glutathione concentrations and glutathione peroxidase activities in plasma and liver (P < 0.05). Analyses based on lutein concentration between abdominal skin and experimental diets revealed that the optimal substitution amount was 72.03% (207.4 g kg−1 of A. platensis), which could ensure growth and pigmentation in yellow catfish. • Arthrospira platensis can be used as alternative source of fish meal in yellow catfish diets. • Arthrospira platensis could increase the lutein contents to enhance the yellowness in skin of yellow catfish. • The quality was improved of yellow catfish because the A. platensis enhanced the pigmentation and antioxidant abilities. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of replacing fish meal (FM) with defatted silkworm pupae meal (SPM) on growth, diet digestibility, antioxidant capacity, hepatopancreas histology and molting process in Pacific white shrimp (Litopenaeus vannamei). A basal diet was formulated to contain 24% FM, then 25, 50, 75 or 100% of FM was substituted with SPM referred to as FM, SPM25, SPM50, SPM75 and SPM100 diets, respectively. Quadruplicate groups (36 shrimp per replicate) of shrimp (0.2 ± 0.02 g) were fed the test diets to apparent satiation three times daily for eight weeks. No significant difference (P >.05) in growth performance could be found among FM and SPM groups. Apparent digestibility coefficients of dry matter, gross energy and phosphorous were significantly improved by SPM inclusion. Serum antioxidant parameters including total antioxidant capacity and malondialdehyde concentration were beneficially influenced by SMP inclusion. Higher number of B-cells and lower number of E-cells were detected in hepatopancreatic tubules of SPM100 group compared to the other groups. Moreover, total replacement of FM triggered separation of basal membrane and greater interstitial spaces between the hepatopancreatic tubules. Molting time significantly decreased when FM was entirely replaced with SPM. Also, chitin deacetylase activity was enhanced in SPM100 group, but β-N-Acetyl- d -glucosaminidase activity, and expression of ecdysteroid receptor and retinoid X receptor remained unchanged. To conclude, the entire replacement of FM with SPM did not influence shrimp growth, and its beneficial impacts were found on diet digestibility, antioxidant capacity and molting time. However, the substitution level is recommended to be restricted to 75% as total replacement led to shrinkage of hepatopancreatic cells. • Total fish meal replacement with silkworm pupae did not hamper shrimp growth. • Silkworm pupae improved diet digestibility and antioxidant capacity. • Entire replacement of fish meal led to significant reduction of molting time. • Substitution level should be limited to 75% due to hepatopancreas tubular damage. [ABSTRACT FROM AUTHOR]

This study was conducted to evaluate effects of replacing fish meal with cottonseed meal protein hydrolysate (CPH) on amino acid metabolism of Megalobrama amblycephala. Fish (38.66 ± 0.08 g) were randomly divided into five groups and fed five isonitrogenous (320 g kg−1 crude protein) and isocaloric (17.8 MJ kg−1 gross energy) diets replacing fish meal by CPH 0% (CPH 0), 1% (CPH 1), 3% (CPH 3), 5% (CPH 5) and 7% (CPH 7). Dietary 3% CPH had no effect on plasma aspartate aminotransferase (AST), alanine aminotransferase (ALT), succinate dehydrogenase (SDH) and xanthine oxidase (XOD) contents and liver SDH and XOD (P > 0.05), but significantly increased hepatic AST and ALT contents (P < 0.05). The plasma threonine (Thr), valine (Val), lysine (Lys), histidine (His), total essential amino acids and total amino acids contents of fish fed CPH5 and CPH7 diets significantly decreased (P < 0.05) compared with the control diet. Meanwhile, threonine (Thr), valine (Val), isoleucine (Ile) and leucine (Leu) contents in muscle significantly decreased (P < 0.05) when fish fed CPH7 diet. Diets with 5% and 7% CPH significantly decreased target of rapamycin (TOR) and S6 kinase-polypeptide 1 (S6K1) mRNA expressions levels in liver and gut, but increased eukaryotic translation initiation factor 4E-binding protein 2 (4E-BP2) mRNA expression levels (P < 0.05), as well as increased hepatic AMP-activated protein kinase α1 (AMPKa-1), AMP-activated protein kinase α2 (AMPKa-2) and sirtuin-1 (SIRT-1) mRNA expressions levels. Furthermore, the AMP-activated protein kinase α (t-AMPKα) and phospho-AMPKα (p-AMPKα) protein contents were increased significantly in fish fed with 5% and 7% CPH over the control group (P < 0.05). Overall, replacing fish meal with CPH at high level (5 and 7%) decreased the amino acid metabolism and growth performance, as well as inhibited ATP consumption via inhibiting TOR signaling pathway and activating AMPK/SIRT1 pathway. • Excess replacement of fishmeal with CPH depressed TOR and S6K1 expressions. • Replacing fishmeal with CPH at appropriate level increased amino acid metabolism. • Replacing fishmeal with CPH at high level decreased amino acid catabolism via activating AMPK/ SIRT1 pathway. • Replacing fishmeal with CPH at high level caused poor growth via inhibiting TOR signaling pathway. [ABSTRACT FROM AUTHOR]

Fish meal is increasingly substituted in diets for gilthead sea bream with ingredients of terrestrial origin which may affect the mineral content and availability. Among these minerals, copper (Cu) is an essential trace element whose excess may have a potential toxic effect. Since ingredients of terrestrial origin have higher Cu levels than marine ones it is important to define the optimal dietary supply of Cu. Therefore, the aim of this study was to evaluate optimal dietary inclusion level of Cu in low FM-FO diets for gilthead sea bream fingerlings. Five practical diets with low FM (10%) and FO (6%) contents were respectively supplemented with 5 levels of CuSO 4 to provide 5.5, 7.4, 9.3, 11.0 and 32.0 mg Cu kg−1 diet. Sea bream fingerlings (12.6 ± 1.4 g, mean ± SD) were distributed in 15 tanks with 30 fish per tank in triplicates and randomly assigned one of the dietary treatments. The fish were fed three times a day until apparent visual satiation for 42 days. Growth was recorded at the end of the trial and samples were taken for biochemical, mineral, histology, X-ray and hepatic gene expression analyses. The results obtained suggest that gilthead sea bream fed practical diets based on plant protein sources that provide at least 5.5 mg Cu kg−1 need no additional Cu supplementation, whereas dietary contents of 11–32 mg Cu kg−1 negatively affected gilthead sea bream performance by reducing growth, increasing oxidative risk and inducing hepatic damage and cholestasis. Dietary Cu levels did not affect body weight, SGR, TGC or FCR, denoting that the level in the non-supplemented diet (5.5 mg Cu kg−1) was enough to cover the requirements for growth. However, increasing dietary Cu levels from 5.5 to 9.3 mg/kg-1 up-regulated cat gene expression. On the contrary elevation of dietary Cu levels up to 11.0 and 32.0 mg Cu kg−1 tended to reduce growth and increased liver steatosis, broken cell margin, peripheral nuclei and sinusoid dilatation which are the markers of hepatic damage and cholestasis denoting potential toxic effects of Cu. • Fish meal replacement by plant ingredients can affect the feed's mineral profile. Copper is one of these minerals whose excess may have a toxic effect. • Little or no Cu supplementation is required in gilthead sea bream practical diets based on plant protein sources that provide at least 5.5 mg Cu kg-1. • Dietary levels of 11-32 mg Cu kg−1 reduced growth, increased oxidative risk and induced hepatic damage and cholestasis in gilthead sea bream juveniles. [ABSTRACT FROM AUTHOR]

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. • Feeding value of DBSFLM for juvenile L. japonicus was determined for the first time in this study. • Replacement of FM with DBSFLM up to 64% did not alter growth performance, hepatic and intestinal histomorphology of L. japonicus. • Replacement of FM with DBSFLM up to 64% was found to decrease serum MDA concentration of L. japonicus. • Dietary supplementation of DBSFLM could inhibit hepatic fat deposition of L. japonicus. [ABSTRACT FROM AUTHOR]

Stocking density is a major factor determining fish production and farm profitability because it directly affects fish survival, growth, behavior, health, water quality, and feeding. The effects of stocking density on water quality, production, body composition and farming profitability of Clarias gariepinus fed a practical marine fish viscera-diet in earthen ponds were studied. Fish (initial weight: 13.0 ± 0.2 g) were stocked in triplicate at densities of 5, 7 or 10 fish m−2 in earthen ponds (3 × 10 × 1 m, each) and hand-fed to apparent satiation twice daily with a diet (43% crude protein, 20 kJ g−1) formulated by mixing 30% of marine fish viscera meal with locally available ingredients, for a period of 90 days. Results indicated strong dependence of water quality parameters on stocking density, with water transparency, dissolved oxygen and zooplankton abundance significantly decreasing with increased stocking density. Similarly, production performance as measured by final weight, specific growth rate, daily weight gain and weight gain were affected by stocking density, and peaked at a stocked density of 7 fish m−2 (p˂0.05). Conversely, total fish yield and annual production increased significantly with increasing stocking density and reached a maximum yield (186.6 ± 3.2 kg are−1) and annual production (756.6 ± 10.7 kg−1are−1 year−1) at the highest density. Profitability analysis indicated that the profitability index (net return per total production cost) was high for all treatments and varied between 2.13 and 2.46, with significant differences between treatments. The highest profitability index was obtained at a density of 7 fish m−2; however, the highest net return was realised at the highest stocking density, but came at the expense of decreased production efficiency and an increased environmental cost, thereby demonstrating the potential trade-offs between maximising shorter term on-farm profits vs. ensuring long term sustainability. The results are useful to guide extensive, pond-based aquaculture practices in Benin, and the work can be expanded in future through synergy-and-trade-off analysis to quantify potential impacts of stocking density on the wider smallholder aquaculture sector in Benin. • Water transparency, dissolved oxygen and zooplankton abundance significantly decreased with increasing stocking density. • The stocking density has significantly increased lipid content and profitability of Clarias gariepinus farming in pond. • The marine fish viscera meal based diet is adapted to the optimal production of Clarias gariepinus in extensive pond systems. • The work establishes an appropriate stocking density for the cultivation of Clarias gariepinus in extensive pond systems. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate if the inclusion of tilapia silage (TS) in diets for Litopenaeus vannamei juveniles and the rearing systems (clear-water and biofloc) could affect the shrimp quality when stored on ice for 15 days post-harvest. The experiment was performed in two experimental systems: biofloc (BF) and clear-water (CW) systems at a shrimp stocking density of 63 shrimp m−2. The treatments were based on the percentage of silage inclusion (control or 0, 1.5, 3.0, 4.5 and 6.0% of inclusion) in each system, totalizing ten treatments and four replicates. Survival was above 80% in all treatments regardless of system or diet. Shrimp final weight and specific growth rate (7.17 g and 2.01% day−1 – BF; 6.35 g and 1.82% day−1 – CW) were statistically influenced by the system but not by the diet. Shrimp quality index and shelf life were not affected by the inclusion of TS in L. vannamei diets rather than rearing system with better results for BF. The results suggest that the substitution of fish meal by fish silage in L. vannamei diet in the presence of biofloc conditions increase the sustainability of intensive shrimp culture and the overall shrimp quality and shelf life. • Tilapia processing waste silage (TS) showed as an alternative ingredient for L. vannamei diets. • Shrimp fed with TS in biofloc had a better growth performance as compared to those in clear-water conditions. • Shrimp quality was not affected by inclusion of TS. [ABSTRACT FROM AUTHOR]

Two trials were carried out to determine the optimal replacement level of fish meal (FM) by soy protein concentrate (SPC) derived from soymilk without supplementation of indispensable amino acids (IAAs) or palatability enhancers and whether phytase supplementation can help to replace more SPC in diet of juvenile red sea bream, Pagrus major. In Trial 1, five isoenergetic diets were formulated: 67% FM as protein source in the control diet (C), and FM was replaced by 60 (SPC60), 70 (SPC70), 80 (SPC80) and 100% (SPC100) by SPC. In Trial 2, diets C and SPC80 were the same as in Trial 1, and phytase was supplemented in SPC80 at 1000 (P1), 2000 (P2), 3000 (P3) and 4000 (P4) FTU/kg diet. Thirty (ca. 23 g) and 20 fish (ca. 21 g) were randomly distributed into each fifteen and eighteen 300 L indoor tanks in Trial 1 and 2, respectively. Fish in both trials were fed two times daily until apparent satiation for 10 weeks. At the end of both trials, feces were collected after feeding with chromic oxide (Cr 2 O 3) mixed diets. In Trial 1, there were no significant differences in final mean weight, specific growth rate (SGR), daily feeding rate (DFR), feed efficiency (FE), condition factor (CF), and retention efficiency of protein, lipid and energy until 70% (SPC70) FM replacement by SPC (P >.05). However, 80% FM replacement significantly reduced final mean weight, FE and lipid retention efficiency compared with group C (P <.05). There were no significant differences in plasma constituents, except total cholesterol level. In Trial 2, phytase was supplemented in SPC80 to determine whether it helps to stimulate growth up to the level of the control group. Fish fed SPC80 once again displayed significantly lower final mean weight, SGR, FE, phosphorus (P) digestibility, and retention efficiency of protein, lipid, energy and P compared with control group (P >.05). Final mean weight, FE, P digestibility, and retention efficiency of protein, lipid and P were significantly improved in fish fed diet P2 (phytase at 2000 FTU/kg diet) compared with those fed diet SPC80. However, phytase supplementation did not stimulate the growth up to the level of group C. The results demonstrated in juvenile red sea bream that 70% of FM can be replaced by SPC derived from soymilk without supplementation of IAAs and palatability enhancers. • The utilization of soy protein concentrate (SPC) from soymilk rather than soybean meal was evaluated in the diet of red sea bream. • SPC derived from soymilk contentedly replaced 70% of FM, which could be beneficial to the aquaculture industry of this species. • Phytase supplementation could not improve the growth performance when SPC from soymilk replaced FM. • The results open a new window to establish a low FM diet for red sea. [ABSTRACT FROM AUTHOR]

A 56-day feeding trial was conducted to evaluate the effects of replacing dietary fish meal (FM) with a complementary mixture of plant protein (PP) consisting of soybean meal (SBM), corn gluten meal (CGM) and cottonseed meal (CSM) on hepatic lipid metabolism and hepatocyte apoptosis in juvenile hybrid grouper, Epinephelus lanceolatus♂ × E. fuscoguttatus♀ (31.64 ± 0.82 g). A basal diet (FM60) with FM as the sole protein source was compared to diets progressively replacing 25% (FM45), 50% (FM30) and 75% (FM15) of FM protein. No significant differences were observed in growth performance and feed utilization when up to 75% of FM protein was replaced by PP sources. The hepatosomatic index (HSI) was markedly increased as dietary PP inclusion increased, but crude lipid content in the liver showed the opposite trend. Plasma cholesterol (CHO), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) of fish fed the PP containing diets were all significantly lower than the control. Liver histological analysis showed a higher levels of hepatocyte vacuolization and nuclear pycnosis occurred as dietary PP inclusion increased, but the amounts of hepatic lipid droplets showed a decreasing trend with increasing PP inclusion levels. Moreover, dietary PP inclusion down-regulated the mRNA levels of lipid metabolism-related genes including peroxisome proliferator-activated receptor alpha (PPARα), carnitine palmitoyltransferase 1 (CPT1), apolipoprotein AI (Apo-AI) and lipoprotein lipase (LPL). On the other hand, dietary PP sources also down-regulated the apoptosis-related genes including caspase-3, caspase-7, caspase-8 and p53. The present study provided new evidence for the PP sources-induced lipid metabolism in carnivorous fish, and provided new insight into the relationship between dietary PP sources and cell apoptosis. • This study provided new evidence for the plant protein sources-induced lipid metabolism in carnivorous fish species. • This study provided new insight into the relationship between dietary plant protein sources and cell apoptosis in fish. • This study showed that a combination of plant protein sources can replace up to 75% of fish meal protein in grouper feed. [ABSTRACT FROM AUTHOR]

Abstract The study was carried out to evaluate wedge wire screen as a potential tool for collecting fish faeces from the tank outlet water. Apparent digestibility (AD) estimates of carbon (AD C), nitrogen (AD N), sulphur (AD S), organic material (AD ORG) and individual amino acids obtained by the wire screen were compared with stripping. Three diets, with fishmeal, soybean meal (SBM) or rapeseed meal (RSM) as main protein source were extruded and fed to triplicate groups of 120-g rainbow trout (Oncorhynchus mykiss). Faeces were obtained by gentle stripping from the distal abdomen, and by collection from a wedge wire screen 15, 30, 60, 120 and 240 min post feeding. AD ORG , AD N and AD S obtained by collection on the screen were significantly (P <.05) higher than those obtained by stripping, except for some values for AD C. Differences in AD between stripping and faeces collected with the wire screen were lower than reported for other methods of collection from water media. Most of the increase in AD of nutrients for wedge wire screen occurred during the first 15 min after defecation. The AD ORG , AD C , AD N and AD S were lowest in the RSM diet. The AD of amino acids followed the same pattern as AD N. AD S in the rapeseed diet was particularly low (54.7%), compared to the fishmeal (72.4%) and SBM diet (70.1%). In addition to AD of cysteine, low digestibility of glucosinolates, its degradation products and other sulfonated components are likely reasons for the low AD S. Faeces from the RSM based diet had higher dry matter (DM) concentration than the SBM based diet. Faecal DM recovery for SBM was lowest among the diets for both collection methods. The low DM recovery for the SBM faeces did not affect AD estimates of faeces at the different time intervals, possibly due to simultaneous leakage of nutrients and indigestible marker. In conclusion, the use of wedge wire screen for collection of faeces represents an interesting supplement to stripping. The AD estimates had low random variation and nutrient leaching during faeces collection were dependent on dietary composition. Highlights • The digestibility estimates from the wire screen had low variation within time points and dietary treatments. • Digestibility results obtained for faeces collected from water should not be used as indicator for fecal nutrient loss • Feed composition and characteristics play a significant role in nutrient loss from faeces. [ABSTRACT FROM AUTHOR]

Abstract Intestinal microbiota plays a vital role in nutrient metabolism, pathogen resistance and development of immune system. Here, an Illumina-based method was employed to investigate the intestinal microbiota in white shrimp fed diets with five replacement levels (0, 10, 20, 30 and 40%) of fishmeal by fermented soybean meal (FSM). The results of growth trail revealed that shrimp fed a diet with 20% replacement of fishmeal by FSM (FSM20) had significantly better growth performance. Based on the sequence analysis, we got a total of 2535 OTUs from all of samples. These OTUs were identified into 22 phyla, among which Proteobacteria was the most abundant one. The richness and diversity of intestinal microbiota were not changed by dietary different levels of FSM (P >.05). Results of functional prediction showed that membrane transport was the most abundant function matching in KEGG database at level 2. In terms of nutrition-related metabolism functions, there was no significant difference in all of dietary groups (P >.05). All the results above showed that dietary appropriate level of FSM (20%) could enhance the growth performance, but not affect intestinal microbiota of shrimp. Highlights • We replaced fishmeal with fermented soybean meal in Litopenaeus vannamei diet. • The intestinal microbiota in L. vannamei was characterized • Growth performance was influenced by dietary fermented soybean meal. • Dietary fermented soybean meal made no difference on intestinal bacterial. [ABSTRACT FROM AUTHOR]

Abstract In order to maximize the output, minimize the waste produced by the fish, and develop nutritionally adequate diets, the digestibility and nutritional value of feed ingredients were evaluated. The objective of this study was to determine apparent digestibility coefficients (ADCs) of dry matter, crude protein, gross energy, phosphorus, and amino acids in feed ingredients for mandarin fish, Siniperca chuatsi with initial average body weight of 31.27 ± 1.64 g. Nine experimental ingredients including white fish meal (WFM), meat and bone meal (MBM), maggot meal (MGM), soybean meal (SBM), fermented soybean meal (FSBM), peanut meal (PNM), corn gluten meal (CGM), cottonseed meal (CSM), and rapeseed meal (RSM) were added to reference diet containing 53% (WFM) at two levels of 15 and 30%. The ADCs of dry matter at the level of 30% were higher than those at the level of 15% in mandarin fish fed with the diet with WFM. In addition, the highest ADCs of dry matter (80.96%) was observed in fish fed with the diet with WFM at the content level of 30%, followed by lower ADC of the ingredients with FSBM, MGM, CGM, SBM, MBM, PNM, CSM, and RSM. However, the ADCs of dry matter in mandarin fish fed with the diet at the level of 15% were higher than those at the level of 30% in MBM, CGM and PNM. The results indicated that ADCs of the experimental ingredients were significantly affected by the ingredient type and the content level. The highest digestion of protein (88.90%) was also observed in WFM at the level of 30%, followed by FSBM (83.93%) and MGM (82.59%) at 30% content level, MGM and FSBM at 15% content level and CGM at 30% content level. Lipid ADCs of WFM, MBM, SBM, FSBM, CGM and CSM ranged from 83.96 to 93.25%, indicating that the lipid of these ingredients was efficiently digested by mandarin fish. The highest digestibility coefficient of energy (88.74%) was registered in WFM at 30% content level, followed by MGM at 30% content level, and the lowest digestibility coefficient of energy (49.24%) was recorded in RSM at 30% content level (P < 0.05). In addition, the apparent digestibility of phosphorus in animal feeds and plant feeds ranged from 35.75 to 63.91% and from 42.21 to 66.77%, respectively. Amino acids digestibility followed a similar pattern to those of ADCs of protein in the animal feeds. Amino acids digestibility in WFM and MGM were generally higher than those in MBM among all the plant feeds. The digestibility of amino acids in FSBM, SBM, and CGM were higher than those in RSM and CSM. In conclusion, these data provide more precise information concerning nutrient and energy utilization of Siniperca chuatsi and will allow ingredient substitutions in practical feed based on levels of available nutrients. Based on the current findings, we propose that FSBM, MGM, SBM, and CGM could be considered for incorporation into formulated diets for mandarin fish. Highlights • The ADCs of dry matter at the level of 30% were higher than WFM at the level of 15%. • The ADCs of the experiment ingredients were significantly affected by the ingredient type and the content level. • The highest digestion of protein (88.90%) was observed in WFM at the level of 30%. • The availability of amino acids in FSBM, SBM, and CGM were higher than those in RSM and CSM. • The high protein ADCs of WFM, MGM and FSBM indicates that they are potentially good protein sources for mandarin fish. [ABSTRACT FROM AUTHOR]

Sec lice infections are recognized as a primary challenge for both salmon farming and adjacent stocks of wild salmon and sea trout, triggering strict regulations at farm sites and in larger coastal production areas. In 2017 the Norwegian government implemented the Traffic Light System (TLS), where green, yellow, and red lights imply that salmon farmers can raise, maintain, or must reduce production quantities depending on estimated sea lice-induced mortality of wild salmonids. Past research has explored the impacts of sea lice on the growth rate of salmon, indicating a possible link between sea lice numbers and harvest practices. This study evaluates the impact of sea lice on salmon farmers' harvest behavior focusing on production quantities and fish sizes while controlling for market prices of salmon and fish meal. We also investigate whether and to what extent the TLS implementation affects harvest behavior. Our empirical results indicate that farmers tend to harvest marginally faster in response to increasing levels of sea lice and slower during delousing operations. The implementation of the TLS strengthened the negative impacts of delousing operations on harvest quantities. Fish sizes at harvest are negatively associated with sea lice levels and delousing operations, regardless of the implementation of the TLS. Control variables, such as seawater temperature, salmon prices, and fish meal prices, also influence harvest quantities and fish sizes. [ABSTRACT FROM AUTHOR]

A 110-day feeding trial was carried out to investigate the impacts of replacing dietary fish meal (FM) with poultry by-product meal (PBM) on growth performance, digestion, gut microbiota, immunity, and disease resistance of abalone Haliotis discus hannai (initial weight: 22.53 ± 0.21 g). The control diet (PBM0) without PBM contained 20% of FM. Based on PBM0, the other four isonitrogenous (about 30% of crude protein) and isolipidic (about 4% of crude lipid) diets were formulated replacing 25, 50, 75 and 100% of FM by PBM (designated as PBM25, PBM50, PBM75 and PBM100), respectively. Every diet was fed to triplicate cages (40 × 35 × 70 cm) with 60 abalones per cage. At the end of the feeding trial, abalones were starved for 3 days and anesthetized with 5% ethanol before sampling. Results indicated that biomass gain of the abalone fed PBM75 (916.71 g) and PBM100 (659.93 g) was significantly lower than that of the abalone fed PBM0 (1222.51 g). Feed conversion ratio of the abalone fed PBM50 (2.93), PBM75 (2.89) and PBM100 (4.04) were significantly higher than that of the abalone fed PBM0 (2.37). The muscle crude protein content of the abalone fed PBM100 (16.01% wet weight) was significantly lower than that of the abalone fed PBM0 (16.67% wet weight). Activities of trypsin and α-amylase in the digestive gland in the PBM100 group (309.21 and 0.064 U/mg prot., respectively) were significantly lower than the PBM0 group (463.57 and 0.078 U/mg prot., respectively). When the substitution levels rose over 50%, expressions of phosphatidylinositol 3 kinase, threonine kinase/protein B, mammalian target of rapamycin and eukaryotic translation initiation factor 4E in muscle were significantly reduced, while 4E binding protein was significantly increased. The most abundant phyla across the abalones' gut were Proteobacteria and Firmicutes. Catalase (from 2.90 to 1.69 U/mL), superoxide dismutase (from 98.93 to 74.39 U/mL), lysozyme (from 345.86 to 247.81 U/mL) and acid phosphatase (from 21.68 to 15.71 U/100 mL) activities in cell-free hemolymph were markedly decreased with substitution level increasing. When the replacement levels rose over 50%, myeloid differentiation primary response gene 88 and tumor necrosis factor α expressions in the digestive gland were markedly upregulated, while β-defensin and mytimacin 6 expressions were markedly downregulated. The cumulative mortality of abalone challenged with Vibrio parahaemolyticus (1.0 × 107 CFU/mL) for 7 days was remarkably increased in the PBM50 (83.49%), PBM75 (89.56%) and PBM100 (100%) groups compared with the PBM0 group (58.82%). In conclusion, 50% of dietary FM could be replaced by PBM without influencing abalone growth. When the replacement level was over 50%, the growth and immunity of abalone were decreased, and the mTOR pathway was negatively affected. • Replacement of dietary fishmeal (FM, 0–20%) by poultry by-product meal (PBM, 0–20.5%) was evaluated in abalone. • The control diet was formulated with 20% of FM and without PBM. • There were no adverse effects on growth when replacement was 50% or less. • Negative effects on growth, immunity and disease resistance were found when PBM replaced more than 50% of FM. • The PBM can be used as an important protein source in the diet for abalone. [ABSTRACT FROM AUTHOR]

Feeding unhydrolyzed protein to the same species from which it came from have caused prion disease in some mammals, but this has not been observed in fish. In this study, we characterized a salmon protein hydrolysate (FPH) for prion content and investigated how partially replacing fish meal with salmon hydrolysate, affected growth, digestibility and gut health of Atlantic salmon (Salmo salar). The salmon hydrolysate was analysed for prion content by shotgun and targeted proteomics, but no prions were found. Atlantic salmon post smolts were fed one of the following: a control diet containing 30% fish meal (FM), a 20% FM with 9% salmon hydrolysate diet (FPH-09) or a 10% FM with 18% salmon hydrolysate diet (FPH-18). Salmon fed the hydrolysate diets had higher specific growth rate over the first 25 days. The FPH-18 diet contained more digestible proteins and amino acids than the FM diet, and the ash digestibility increased linearly with the FPH content, indicating increased mineral uptake. Histological analysis of midgut and hindgut did not reveal any significant differences between the FM and FPH-18 diets, and the intestines were assessed to be normal and healthy. These results imply that salmon hydrolysate is a promising novel feed ingredient for Atlantic salmon, due to its excellent amino acid profile and high digestibility. • Salmon protein hydrolysate (FPH) is a novel feed ingredient for Atlantic salmon. • FPH has an excellent amino acid profile and feed stimulatory properties. • No salmon prions were found by proteomics analysis of the salmon hydrolysate. • Partially replacing fish meal with FPH increased the protein and ash digestibility. • Dietary FPH significantly increased the initial growth rate of post smolts. [ABSTRACT FROM AUTHOR]

In the present study, gilthead sea bream (Sparus aurata) was reared using sustainable feeds containing insect meal from Hermetia illucens larvae. Proteomics and proton nuclear magnetic resonance-based metabolomics analysis were used to assess the metabolic impact of the tested feeds in sea bream liver, whereas the composition of muscle fillets was characterized by means of metabolomics and gas chromatography of fatty acid methyl esters. Including 10% of insect meal while correspondingly reducing fish meal did not substantially alter the metabolism of dietary nutrients, leading to small but significant effects solely on lauric acid content of sea bream fillets. Furthermore, a few alterations in some markers of immune response, such as leukocyte elastase inhibitor-like, granzyme B (G, H)-like, and two associated ortholog groups, serpin B and chymase, were found. In the fish group fed with insect meal, liver morphology analysis showed no structural damage or inflammation and a lower amount of hepatic lipid deposition and accumulation. • Liver morphology, proteomics, metabolomics, and the fatty acid profile of the fillets showed little effect of diet. • Some liver markers of immune response were found to be associated with insect meal use. • A multidisciplinary analytical approach provided new insights into the use of sustainable protein sources in aquafeeds. [ABSTRACT FROM AUTHOR]