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Although aquaculture industry has made great efforts to reduce the levels of fish meal (FM) in aquaculture feeds, further efforts and investigations are still needed to increase aquaculture production, which has more than tripled in the last two decades. This study was implemented to Six replicate groups of fish (24.6 ± 0.1 g) were fed one of the experimental diets to apparent satiety twice daily for 15 weeks; half of them were subjected to a daily net chasing stress for 1 min in the morning, 1 h before feeding. At the end of the feeding trial, fish were challenged with Edwarselia tarda injection. LFM diet resulted in comparable growth and feed efficiency performance to HFM group. However, significant impairments were observed in apparent digestibility coefficients, condition factor, hematocrit and serum super oxide dismutase activity. Fish fed LFM showed much lower resistance to E. tarda challenge. Both TH and SH resulted in enhanced fish nutritional and health performance with significant improvements in growth performance, feed efficiencies, digestibility, serum non-specific immunity and gut morphometric parameters. Fish fed TH and SH also exhibited the highest survival after E. tarda challenge. Principal component analysis (PCA) showed significant differences between stress and dietary groups for dimension 1 (33.3% of the variability), which was mostly characterized by growth and health variables. SH and TH coordinates were significantly higher on dimension 1 compared to HFM and LFM ones. Daily repeated stress affected most of measured performance parameters of all dietary groups with very few interactions. The stressed fish groups fed TH or SH showed lower cortisol levels compared to those fed HFM and LFM (p < 0.01). Strong correlations were observed between feed efficiency and fish gut morphometrics as quantified by villi length, enterocyte height and goblet cell density. Dietary supplementation of aquatic protein hydrolysates such as TH and SH appeared to be essential for maintaining good fish performance when they were subjected to a daily husbandry stressor or to an infectious challenge. • FM reduction may result in an impaired fish health status despite good growth • APH mitigate stress adverse effects • APH help to reduce FM and antibiotic uses [ABSTRACT FROM AUTHOR]

Fishmeal (FM) replacement using cost-effective blends of complementary ingredients is commonly used in carnivorous marine fish diets for economic and sustainable purposes. The use of functional compounds such as prebiotics or functional ingredients is a nutritional strategy in low FM diets to maximize growth and feed utilization, as well as reducing enteropathies caused by plant proteins, in particular soybean meal (SBM) that can induce enteritis in Totoaba macdonaldi juveniles. Therefore, this study was conducted to evaluate the effects of glutamine (Gln) and agavin (AGA) as a novel prebiotic or a combination of both on growth parameters, digestive capacity, whole-body proximate composition, gut health, and sustainable and economic indexes in totoaba juvenile fed low FM (17%) diet for 56 days. Juvenile totoaba with an initial weight of 168 ± 4 g were fed one of four isoproteic and isolipidic diets formulated with poultry by-product meal and FM in a 2:1 ratio and 24% of SBM. For the control basal diet (SBM), no Gln or AGA was added. The other three experimental diets consisted of the basal diet with either 1.5% glutamine (GLN), 1% prebiotic agavin (AGA), or 1.5% glutamine and 1% agavin (Gln + AGA) supplementation. Fish fed the Gln diet significantly improved growth, feed utilization and increased trypsin, total alkaline proteases, and L-aminopeptidase activities. Additionally, an enhanced brush border height (BBH) in the distal intestine was observed in the Gln group, suggesting improved intestinal health compared to the rest of the treatments. However, no significant synergistic effect was observed in fed fish the Gln + AGA diet. Interestingly, no signs of enteritis among the fish fed the four experimental diets was observed. These results suggest that fish with an initial size of 168 g are less susceptible to the adverse effects of SBM compared to previous studies. The inclusion of 1.5% dietary glutamine is recommended in totoaba diets with low FM containing 24% of SBM. Since the fish fed the diet supplemented with glutamine + agavin resulted in intermediate values for the parameters evaluated, it is recommended to evaluate different levels of agavin in combination with glutamine or perform longer bioassays using immunological or environmental challenges to aid in elucidating potential benefits of these functional compounds and their synergistic effects. • Addition of 1.5% glutamine in totoaba diets improved growth, feed utilization, and increased intestinal brush border height. • Combining dietary glutamine with agavin resulted in small synergistic effects and should be further evaluated. • Dietary glutamine increases sustainability by reducing the fishmeal dependency and improving fish intestinal health. • Results suggest totoaba juveniles with larger initial weight are less susceptible to dietary SBM induced adverse effects. [ABSTRACT FROM AUTHOR]

Abstract This study was conducted to examine the effects of fish meal (FM) replacement by rice protein concentrate (RPC) supplemented with xylooligosaccharides (XOS) on the growth, intestinal digestive and absorptive capabilities and amino acid metabolism of blunt snout bream. Fish were randomly divided into six groups, and were fed with the control diet (containing 10% FM), the RPC diet (FM entirely replaced by RPC) and the RPC diet supplemented with 0.5, 1.5, 2.3 and 3% XOS, respectively, for 8 weeks. Fish fed the RPC diet obtained significantly lower values in daily growth index, feed efficiency ratio, nitrogen and energy retention and plasma concentrations of methionine, leucine, phenylalanine, lysine and histidine compared to the control. However, the supplement of 1.5% XOS restored these parameters to the levels similar to the control group. Fish fed the RPC diet showed no statistical difference in intestinal lipase, alkaline phosphatase and Na+K+-ATPase activities compared to the control group, but exhibited lower protease, carboxypeptidase A, aminopeptidase N and γ-glutamyl transpeptidase activities. However, these effects were reserved with the administration of 1.5% XOS. Also, the transmission electron microscopy analysis showed a significantly lower microvilli length in the mid-intestine of fish fed the RPC diet compared to the control, but it improved significantly with the supplementation of XOS. Hepatic activities of alanine transaminase, aspartate aminotransferase and glutamate dehydrogenase were significantly lower in fish fed the RPC diet compared to the control, but they improved with the supplementation of 1.5% XOS. Similarly, fish fed the RPC diet obtained relatively low expression levels of the target of rapamycin (TOR) and ribosomal protein S6 kinase 1 but higher expressions of eukaryotic translation initiation factor 4E-binding protein 2 in the intestine, liver and muscle. Opposite trend was observed in fish fed the RPC diet supplemented with 1.5% XOS. Overall, these results showed that RPC supplemented with 1.5% XOS could completely replace FM in the feed of blunt snout bream without any adverse effect on the growth performance, intestinal enzymes activities, gut morphology, amino acid metabolism and TOR signaling. Highlights • FM replaced by RPC led to a significant reduction in growth, feed utilization and AA metabolism. • The supplementation of 1.5% XOS restored these parameters to the levels similar to the control. • Excessive XOS levels led to compromised growth, feed utilization and AA metabolism. [ABSTRACT FROM AUTHOR]

Abstract An 8-week feeding trial was carried out to evaluate the effects of replacing fish meal (FM) with housefly (Musca domestica) maggot meal (HFMM) on growth, antioxidant capacity, digestive enzymes activity, and gut health of bullfrog Rana (Lithobates) catesbeiana. A basal experimental diet was formulated using FM and soybean meal as the major protein sources, then four other diets were produced by replacing 25, 50, 75 or 100% of FM with HFMM (FM, HFMM25, HFMM50, HFMM75 and HFMM100 diets). Each diet was fed to triplicate groups of bullfrog (34.1 ± 1.10 g) to apparent satiation twice daily. No significant linear or quadratic trends were observed between FM replacement level and growth, feed utilization and survival rate (P > 0.05). A significant negative linear trend was detected between the incremental levels of HFMM and apparent digestibility coefficients (ADCs) of dry matter, protein and lipid, while positive linear and quadratic trends were found in ADC of phosphorous (P < 0.05). A negative linear trend was observed between whole-body ash content and HFMM level. Positive linear and quadratic trends were found between serum aspartate aminotransferase, alkaline phosphatase and lysozyme activities and incremental HFMM levels. Liver superoxide dismutase and catalase activities were increased linearly, and total antioxidant capacity was enhanced both linearly and quadratically by incremental levels of HFMM. In contrast, a negative linear trend was found in liver malondialdehyde concentration. A significant positive quadratic trend was found between intestinal protease, lipase and amylase activities and incremental levels of HFMM. Histological observations revealed a significant negative linear trend between HFMM level and villus height and muscular thickness. Gut microbiota analysis showed no significant changes in the operational taxonomic unit (OTU) diversity and richness indices among treatments. Positive linear and quadratic trends were found between incremental HFMM levels and expression of liver HSP70 and IGF-Ι and intestinal TNF-α, IL-1ß, IL-8 and IL-17 genes. The findings in this study showed that although growth performance was not significantly affected by total replacement of FM with HFMM, nutrients digestibility and gut health could be adversely influenced at higher replacement levels. Highlights • Housefly maggot meal was evaluated as a fish meal replacer in bullfrog diets. • Total replacement of fish meal did not lead to detrimental effects on growth. • Gut health was adversely affected at higher replacement levels. • Housefly maggot meal inclusion enhanced antioxidant capacity and immune response. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the use of novel ingredients such as green pea protein and Ascophyllum nodosum , a brown seaweed for the replacement of fish meal in feeds suitable for organic production. The growth, feed utilization and fillet composition of gilthead seabream were examined under a lab scale trial and based on the results a large-scale field trial was conducted in the facilities of Galaxidi marine farms in order to compare a novel feed with a typical commercial feed suitable for organic production. Final weight, growth rate and somatic indices of the fish fed these alternative ingredients did not show significant differences compared to the control group fed the commercial diet. Muscle protein content was higher in the fish fed the higher inclusion level of green pea protein, whereas lipid content was lower in both experimental diets. Fatty acid composition, in terms of n-3 and n-6 polyusaturated (PUFA), eicosapentanoic (EPA) and docosahexaenoic (DHA) acid content was higher in the muscle of the fish fed the experimental diets. In the case of the liver, the fatty acid profile reflected the feed composition, and the fish fed the diet with an inclusion of 19% green pea protein showed a lower content of protein and a higher content of n-6 PUFA, and monounsaturated fatty acids (MUFA). In view of the results obtained, the ingredients assayed in this study could be used in organic feed formulations as alternatives to fish meal obtained from trimmings since no negative effects were detected neither on fish growth, muscle composition, fish health nor end product quality and nutritional value. • Green Pea Protein can be included up to 25% in organic feeds for gilthead sea bream Sparus aurata • Seabream growth and conversion using this new organic ingredient are similar to those obtained using a commercial feed • The addition of seaweed meal as a supplement can also contribute to the growth, health status and final composition of organic gilthead sea bream. [ABSTRACT FROM AUTHOR]

A 59-days feeding trial was carried out to estimate the effects of fish meal replacement by defatted black soldier fly larvae meal (DBSFLM) on growth performance, antioxidate enzyme activities, digestive enzyme activities, hepatopancreas and intestinal morphology in Jian carp ( Cyprinus carpio var. Jian) juveniles (initial mean body weight, 34.78 g). Five isolipidic (5.29 ± 0.04%) and isoprotein (40.69 ± 0.11%) diets were formulated by replacing 0%, 25%, 50%, 75%, 100% fish meal (FM) protein with graded DBSFLM levels of 0%, 2.6%, 5.3%, 7.9% and 10.6%. Each diet was randomly assigned to triplicate groups of 20 fish per aquarium. Fish were fed three times daily to apparent satiation. The results showed that the growth performance and nutrients utilization of fish in five groups were not different ( P > 0.05). The hepatopancreas lipid and serum cholesterol content of treated groups was significantly lower than that of the control group ( P < 0.05). With increasing dietary DBSFLM level, the activity of the CAT significantly increased. No significant differences in the activity of intestinal protease, lipase and diastase were observed among dietary groups ( P > 0.05). The histological examination of intestine showed that when 75% or more FM protein was replaced, apparent pathological changes for example tissue disruption were observed in intestine, and relative gene expression of HSP70 in hepatopancreas significantly increased ( P < 0.05). The histological examination of hepatopancreas sections showed less vacuolated with lipid deposits in treatment groups compared with control group. These results suggested that the growth of Jian carp was not affected by dietary DBSFLM, while it boosted antioxidant status of Jian carp by higher CAT activity. However, dietary stress and intestinal histopathological damage was observed when the replacement levels exceeded 75%. The study demonstrates that it is suitable to replace up to 50% of dietary FM protein with DBSFLM. [ABSTRACT FROM AUTHOR]

Black soldier fly larvae (BSFL) meal, produced from the larvae of Hermetia illucens, has shown promise as a fish meal (FM) replacement in diets for rainbow trout, catfish and tilapia, but has not been examined as an alternative protein source in shrimp diets. Six isonitrogenous (35% crude protein, as fed) and isoenergetic (16.7 kJ available energy g − 1 of diet) diets containing graded levels of BSFL as replacements for protein from menhaden FM were fed to juvenile (1.24 g ± 0.01; mean ± SE) Pacific white shrimp, Litopenaeus vannamei . Diet 1 (the control) was formulated similar to a commercial shrimp diet containing 25% menhaden FM and 23% soybean meal. Diets 2–6 were formulated as a dose-response series that progressively replaced protein from menhaden FM with BSFL meal at inclusion rates of 7%, 14%, 21%, 28%, and 36% of diet; this equated to progressively replacing 16.5% of dietary protein provided by menhaden FM. Diets were fed to juvenile shrimp stocked into eighteen 110-L saltwater aquaria (30 ppt) (three replicates per dietary treatment) at a density of 15 shrimp per aquarium (50/m 2 ) for 63 days. Nonlinear and spline regression analysis of responses indicated that the maximum level of BSFL meal inclusion varied significantly with the response being modeled. Generally, without modification of the ingredient or replacement diet nutrient profiles, 95% to 100% of most growth responses, i.e., shrimp final weight, weight gain, specific growth rate, and food conversion, could be obtained if replacement of FM by BSFL meal was limited to < 25% of the diet, depending on performance measure. Similarly, 95% or greater of maximum whole-body protein and lipid content could be achieved when BSFL inclusion was restricted to < 29% and 15%, respectively. Comparison of amino acid profiles in the test diets with recent requirement estimates for limiting amino acids in BSFL meal also suggest future strategies for increasing dietary substitution of FM with BSFL. [ABSTRACT FROM AUTHOR]

The aim of the present research was to investigate the potential use of the phototrophic microalgae Phaeodactylum tricornutum ( P. tricornutum ) as a fish meal replacement in diet for Atlantic salmon, Salmo salar . Two experiments were designed with fish meal based control diets and dried whole cells P.tricornutum replacing fishmeal in the ratios 3%, 6% and 12% (experiment one) and 3 and 6% (experiment two). Experiment one was a digestibility study lasting for 21 days, investigating effects of inclining level of P. tricornutum on apparent digestibility (ADC) of nutrients and energy. Experiment two was investigating ADC's of nutrients and energy, growth performance and nutrient retention in salmon fed for 82 days. The results from experiment one showed a linear reduction in ADC of dry matter (DM; P = 0.02), lipid ( P < 0.0001), and protein ( P = 0.04) with increasing level of algae biomass in the diet. The ADC of starch increased ( P < 0.05) with algae inclusion level in both experiments. For experiment two, no effects were observed on digestibility of DM, lipid, protein, energy or ash, with 3 and 6% algae replacing fish meal. Neither was growth or feed conversion affected by 3 and 6% algae replacing fish meal. Increasing inclusion level of algae biomass caused an increase in whole body lipid. The ADC of saturated fatty acids was higher in fish fed 3% alga biomass compared to the 6% group. There was no difference in ADC or retention of n -3 fatty acids. In conclusion, the two experiments showed that P. tricornutum can replace up to 6% of the fish meal without adverse effects on nutrient digestibility, utilization of the feed and growth performance. Statement of relevance Microalgae are potential omega-3-contributing feed ingredients [ABSTRACT FROM AUTHOR]

Four isoproteic/isolipidic plant protein-based diets were formulated to assess the lasting effects of feed additives and low fish meal (FM) and fish oil (FO) diet formulations on gilthead sea bream growth performance. FM was included at 23% in the control diet (D1) and at 3% in the other three diets (D2, D3, D4). Added oil was either FO (D1) or a blend of vegetable oils replacing 58% (D2) and 84% (D3, D4 diets) of FO. A commercial sodium butyrate preparation (NOREL, 70-BP) was added to the D4 diet at 0.4%. Each diet was allocated to triplicate groups of juvenile fish fed to satiety over an 8-month feeding trial (May–December). All fish grew efficiently from 15 g of initial body weight to 296–320 g with an overall feed efficiency (FE) of 0.95–1.01, although fish fed D3 and D4 diets showed transient growth impairments over the course of the first four weeks of the trial. Data on biometric indexes, whole body composition, haematology and blood biochemistry revealed a strong effect of sampling time in fish sampled at mid-summer (August) and late autumn (December). In contrast, the diet effect was mostly reduced to a few blood parameters. Low inclusion levels of FM reduced plasma haemoglobin levels (D2, D3), but these effects were reversed by butyrate supplementation (D4). The same phenomena occurred for total cholesterol with the highest circulating concentration of choline and IGF-I in fish fed the D4 diet during their summer growth spurt. At the transcriptional level, gene expression profiling of liver and skeletal muscle with a PCR-array of 87 growth markers provided additional evidence for an overall well-growth condition in all of the experimental groups. Up to 73 genes were found at detectable levels in the liver tissue, but only 13 were differentially expressed. Likewise, 84 genes were actively transcribed in the skeletal muscle, but only nine were differentially expressed in at least one experimental group. Butyrate supplementation reversed the up-regulated expression of inflammatory cytokines (TNFα) and muscle markers of cellular morphogenesis and protein breakdown (CDH15, CAPN3, PSMA5, PSMB1, UBE2N) in the muscle of fish fed the extreme D3 diet. These results support the use of low FM/FO diets alone or supplemented with feed additives, which have the potential to improve or reverse metabolic steady-states. Statement of relevance Butyrate effect on low fish meal/fish oil diets. [ABSTRACT FROM AUTHOR]

Microalgae exhibit diverse and high nutritional value, and therefore, have a huge potential application as a raw material for the preparation of aquafeeds. This study was conducted to evaluate the effects of low-level replacement of dietary fishmeals by algal meals comprised of Schizochytrium limacinum (SL) and Nannochloropsis salina (NS) individually and in combination in the diet of juvenile largemouth bass (LMB, Micropterus salmoides). Five isonitrogenous, isolipidic, and isoenergetic diets with fishmeal-based diets as control, and four experimental diets with replacement by individual 4% SL (4SL), individual 4% NS (4NS), 2% SL combined with 2% NS (2SL + 2NS) and 4% SL combined with 4% NS (4SL + 4NS) were formulated. Five hundred juvenile fish (average weight 8.72 ± 0.10 g) were evenly distributed to five groups with quadruplicate each, in twenty fiberglass tanks and fed for eight weeks. Our results showed that there were no significant difference in weight gain, special gain rate, hepatosomatic index, viscerasomatic index, conditioning factor, and the whole-body composition among the five groups (p > 0.05). However, feed intake and feed conversion ratio in the 4NS treatment were significantly higher (p < 0.05) compared with the control. Further, lipid content and intraperitoneal fat ratio in the liver of the 4NS and 4NS + 4SL groups were significantly decreased, suggesting that NS may reduce visceral fat accumulation in LMB. The serum superoxide dismutase (SOD) activity of LMB in the 4NS group was significantly increased compared with the control (p < 0.05). However, malondialdehyde (MDA) content in the liver of the 4NS group and intestine of the 4SL + 4NS group was significantly lower than that in the control (p < 0.05). Replacement with 4% SL significantly increased docosahexaenoic acid, polyunsaturated fatty acids (PUFAs), and n-3 PUFA proportions in the liver. Further, SL alone or in combination with NS increased the n-3 to n-6 ratio of PUFAs in the liver and muscle, creating more balanced unsaturated fatty acids. The fillet texture was significantly enhanced by taste and flavor. Nevertheless, the present study verified the successful addition of SL and NS algal meals to fish feed, which exhibited excellent potential to replace fishmeals and fishoil, respectively, as protein and lipid sources. • Effects of fishmeal replacement by algal meals on largemouth bass were evaluated. • Low-level substitution had no negative effect on growth or whole-body composition. • Fishmeal replacement (4%) with Nannochloropsis salina decreased lipid deposition. • Fishmeal replacement (4%) with Schizochytrium limacinum increased docosahexaenoic acid. [ABSTRACT FROM AUTHOR]

Ascorbic acid (Vitamin C - VC) is one of the essential micronutrients required for normal growth and physiology of fish. In this research, the optimum dietary VC requirement of juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂) was evaluated in a comparative feeding trial and subsequent oxidative stress test. Six isoenergetic (340 kcal/kg), isoproteic (49%) and isolipidic (7%) experimental diets were supplemented with graded amounts of L-ascorbyl-2-polyphosphate (analyzed VC concentrations of 76, 86, 104, 126, 137 and 152 mg/kg dry matter) and hand-fed to fish (initial weight of 15 ± 0.1 g/fish (means ± S.D.)) in three replicate cages twice a day (08:00 h and 16:30 h) to apparent satiation for 7 weeks. Percent weight gain (WG%), together with the VC concentrations in liver and head kidney, were elevated with increasing dietary VC contents, reaching a plateau in the VC137 treatment. The optimal dietary VC requirement of hybrid grouper was estimated to be 148 mg/kg dry matter based on broken-line regression analysis of WG%. Serum immunoglobulin M (IgM) concentrations and the relative mRNA expression of hepatic insulin-like growth factor-1 (IGF-1) displayed a similar variation tendency as WG%. At the transcriptional level, the activity of Nrf2-Keap1 pathway was up-regulated by VC supplementations, with the VC104 treatment showing the highest value. In summary, the optimal dietary VC requirement for the highest value of WG% of juvenile hybrid grouper was 148 mg/kg dry matter, and appropriate dietary VC supplementation improved oxidation resistance and serum IgM concentrations of the fish. • VC affects growth and expression of hepatic IGF-1 of hybrid grouper. • At the transcriptional level, the activity of Nrf2-Keap1 pathway was up-regulated by VC supplementations. • Optimal VC requirement of hybrid grouper fed low fishmeal diets was 148 mg/kg. [ABSTRACT FROM AUTHOR]

Abstract: A constraint for the expansion of cobia aquaculture is the availability of high quality formulated diets which reduce or eliminate fish meal (FM) protein. Therefore, the nutritive value of a novel soybean cultivar, Navita™ (Navita, non-genetically modified and selectively bred soy), and regular, commodity soybean meal (SBM, de-hulled, defatted, roasted and solvent-extracted) was evaluated for cobia, Rachycentron canadum via separate digestibility and growth trials. In the first experiment Navita's apparent digestibility coefficients (ADC) were higher than those of SBM for nearly every nutrient evaluated. Crude protein ADCs were 82 and 69% for Navita and SBM, respectively. Apparent DC for amino acids ranged from 68 to 109% for Navita whereas, amino acid ADCs for SBM varied from 42 to 98%. The feeding trial utilized fish of a size that more closely resembles commercial cobia stocking (1.8kg), and was conducted over a 91-day period. Experimental diets (iso-nitrogenous and iso-energetic) were formulated such that 67% of the FM protein in the reference diet was replaced by either a combination of SBM+soy protein concentrate (SPC, Solae Profine®) labeled MXSB-diet, or by a combination of SPC+Navita; Navita-diet, hereafter. A fourth experimental diet had 80% of the FM protein replaced by a combination of Navita+SPC and was identified as Navita-high. No significant differences (P >0.05) were observed in fish fed the experimental diets for feed conversion ratio, protein efficiency ratio, feed efficiency, mean daily intake, gross protein intake, gross energy intake, visceral somatic index, muscle ratio, and hepatosomatic index. Fish fed the Navita-high diet had the lowest fish in:fish out ratio (FIFO) at 0.9±0.16. These results indicate that Navita meal can be incorporated at very high levels in the diet of marine carnivorous fish such as cobia with no detriment to performance, making it a prime candidate for FM replacement in aquafeeds. [Copyright &y& Elsevier]

Abstract: Plant protein sources have been identified to have the greatest potential to replace fish meal protein in aquafeeds. However, plant ingredients contain significant quantities of carbohydrates, and the ability of fish to utilize dietary carbohydrates as energy sources for growth is limited. Included in the carbohydrate group, cellulose is not tolerated by most fish. In the present study, the grass carp, a typical herbivorous fish, fed with duckweed was selected to study the effect of exogenous cellulase on the growth. The results of 2-month feeding experiment showed that the cellulase promoted the growth of grass carp. In addition, the cellulase increased various digestive enzyme activities, such as cellulase, amylase and protease but not the lipase activity. Meanwhile, the polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) analysis indicated that the intestinal microbiota of fish fed with the supplemental cellulase changed in bacteria species and density. Band patterns derived from control and cellulase samples showed a low degree of similarity when analyzed by cluster analysis. Some bands were unique to control samples, whereas other bands were obtained only with samples of the cellulase group. The 16S rRNA gene sequencing identified that Proteobacteria and Firmicutes were the two dominant groups, and the emergence of certain bacterial strains including Bacilli and Sphingomonas may contribute to the digestion of cellulose. The former researches and this paper results suggest that the endogenous cellulase is far from sufficient to fully digest the ingested fiber, so cellulase should be developed as a kind of aquatic additive. [Copyright &y& Elsevier]

Atlantic salmon fed low fish meal feeds supplemented with zinc (Zn) were studied in two feeding trials. In trial I, Atlantic salmon parr were fed six graded Zn levels (40 to 249 mg kg−1 as ZnSO 4) for 8 weeks in freshwater followed by a 4-week seawater phase. In trial II, Atlantic salmon post-smolt were fed for 10 weeks in SW with 10 dietary Zn levels (45 to 280 mg kg−1), either as ZnSO 4 or Zn-glycinate. Growth was unaffected by dietary Zn in both trials. Dietary Zn affected concentration of Na + and K+ ions in plasma, branchial and intestinal expression of sodium potassium ATPase, tissue and body Zn status, and cataracts. Seawater transfer significantly reduced apparent availability, body and tissue levels of Zn due to increased endogenous Zn loss. Atlantic salmon post-smolt in seawater improved body and tissue Zn status with increasing dietary Zn levels, irrespective of the Zn source. Body or tissue saturation of Zn occurred at dietary Zn levels between 137 and 156 mg kg−1 with smolts in freshwater and 181 to 218 mg kg−1 in SW post-smolts. Dietary Zn levels below 180 mg kg−1 in low fish meal feeds compromised the Zn status and welfare of Atlantic salmon in seawater. • Impact of dietary Zn and seawater transfer was studied in Atlantic salmon. • Atlantic salmon in seawater have lower Zn availability and increased endogenous Zn loss than in freshwater. • Dietary Zn affects osmoregulatory responses in Atlantic salmon smolt. • Zinc sulfate and zinc chelate of glycine have similar availability to Atlantic salmon in seawater. • Reduction in maximum dietary Zn levels to 150 ppm in salmon feeds will affect the health and welfare in seawater. [ABSTRACT FROM AUTHOR]

Balantidium ctenopharyngodoni Chen, 1955 is an intestinal ciliate identified from the hindgut of grass carp (Ctenopharyngodon idella). Although it was described quite a long time ago, its epidemiologic features and growth characteristics remain poorly understood. In the present study, the investigation of B. ctenopharyngodoni presence was conducted in different age groups of grass carp, and we also developed a self-made medium (BCM medium) to cultivate B. ctenopharyngodoni in vitro. In the grass carp fed on plant-based diets, balantidia were not identified before the age-1, whereas they were identified in fish above the age-1. In the fishes fed on the granular fish meal we did not identify any balantidia regardless of the age of the fish (age-1+ or age-2). BCM medium was effective for in vitro cultivation of B. ctenopharyngodoni , and polysaccharides were an essential nutrient for its growth. We also proposed potential infection mechanisms of B. ctenopharyngodoni in the grass carp above two summers of age. • The prevalence and intensity of Balantidium ctenopharyngodoni in grass carp (juvenile to adult) were investigated. • B. ctenopharyngodoni can be cultivated in the BCM medium, which mainly contains starch, serum and intestinal bacteria. • The potential infection mechanisms of B. ctenopharyngodoni were proposed. [ABSTRACT FROM AUTHOR]

Largemouth bass is a carnivorous fish commercially important for freshwater aquaculture worldwide, however, the optimal feeding regime for the fish reared in pond has not been established. The present study examined feed intake, growth, feed utilization, body composition and waste outputs of largemouth bass fed at different feeding frequencies in pond and in-pond-raceway (IPR). Two 10-week feeding trials (I and II) were conducted simultaneously. Fish were fed at 1, 2, 3 or 4 meal d−1 in pond (trial I), and were fed at 2 or 3 meal d−1 in either pond or IPR (trial II). The initial body weight was 43.0 ± 0.2 g fish−1. In trial I, weight gain increased with increasing feeding frequency from 1 to 3 meal d−1, but no significant difference was found in weight gain between fish fed at 2, 3 and 4 meal d−1. The lowest retention efficiencies of nitrogen (NRE) and phosphorus (PRE) and the highest feed intake and phosphorus waste occurred in fish fed at 4 meal d−1. In trial II, no significant difference was found in weight gain between fish fed at 2 and 3 meal d−1 in IPR, while NRE, PRE and energy retention efficiency (ERE) were lower in fish fed at 3 meal·d−1 than in fish fed at 2 meal d−1. Weight gain, NRE, PRE and ERE were lower, while feed intake, body lipid content, wastes of nitrogen, phosphorus and carbon were higher, in fish reared in IPR than in fish fed at the same feeding frequency in pond. The present study indicates the optimal feeding frequency was 3 meal d−1 for largemouth bass reared in pond, and 2 meal d−1 for the fish reared in IPR. According to production performance, the IPR should not be an appropriate grow-out system for commercial largemouth bass farming. • The optimal feeding frequencies for largemouth bass reared in pond and IPR were determined. • Growth, feed utilization efficiency and waste outputs of the fish reared in pond and IPR were evaluated. • IPR should not be an appropriate system for commercial largemouth bass farming. [ABSTRACT FROM AUTHOR]

Largemouth bass is a carnivorous fish commercially important for freshwater aquaculture worldwide, however, the optimal feeding regime for the fish reared in pond has not been established. The present study examined feed intake, growth, feed utilization, body composition and waste outputs of largemouth bass fed at different feeding frequencies in pond and in-pond-raceway (IPR). Two 10-week feeding trials (I and II) were conducted simultaneously. Fish were fed at 1, 2, 3 or 4 meal d−1 in pond (trial I), and were fed at 2 or 3 meal d−1 in either pond or IPR (trial II). The initial body weight was 43.0 ± 0.2 g fish−1. In trial I, weight gain increased with increasing feeding frequency from 1 to 3 meal d−1, but no significant difference was found in weight gain between fish fed at 2, 3 and 4 meal d−1. The lowest retention efficiencies of nitrogen (NRE) and phosphorus (PRE) and the highest feed intake and phosphorus waste occurred in fish fed at 4 meal d−1. In trial II, no significant difference was found in weight gain between fish fed at 2 and 3 meal d−1 in IPR, while NRE, PRE and energy retention efficiency (ERE) were lower in fish fed at 3 meal·d−1 than in fish fed at 2 meal d−1. Weight gain, NRE, PRE and ERE were lower, while feed intake, body lipid content, wastes of nitrogen, phosphorus and carbon were higher, in fish reared in IPR than in fish fed at the same feeding frequency in pond. The present study indicates the optimal feeding frequency was 3 meal d−1 for largemouth bass reared in pond, and 2 meal d−1 for the fish reared in IPR. According to production performance, the IPR should not be an appropriate grow-out system for commercial largemouth bass farming. • The optimal feeding frequencies for largemouth bass reared in pond and IPR were determined. • Growth, feed utilization efficiency and waste outputs of the fish reared in pond and IPR were evaluated. • IPR should not be an appropriate system for commercial largemouth bass farming. [ABSTRACT FROM AUTHOR]

Abstract: The nutritional contribution of the dietary nitrogen, carbon and total dry matter supplied by fish meal (FM), soy protein isolate (SP) and corn gluten (CG) to the growth of Pacific white shrimp Litopenaeus vannamei was assessed by means of isotopic analyses. As SP and CG are ingredients derived from plants having different photosynthetic pathways which imprint specific carbon isotope values to plant tissues, their isotopic values were contrasting. FM is isotopically different to these plant meals with regards to both, carbon and nitrogen. Such natural isotopic differences were used to design experimental diets having contrasting isotopic signatures. Seven isoproteic (36% crude protein), isoenergetic (4.7kcal g−1) diets were formulated; three diets consisted in isotopic controls manufactured with only one main ingredient supplying dietary nitrogen and carbon: 100% FM (diet 100F), 100% SP (diet 100S) and 100% CG (diet 100G). Four more diets were formulated with varying mixtures of these three ingredients, one included 33% of each ingredient on a dietary nitrogen basis (diet 33FSG) and the other three included a proportion 50:25:25 for each of the three ingredients (diets 50FSG, 50SGF and 50GFS). At the end of the bioassay there were no significant differences in growth rate in shrimps fed on the four mixed diets and diet 100F (k =0.215–0.224). Growth rates were significantly lower (k =0.163–0.201) in shrimps grown on diets containing only plant meals. Carbon and nitrogen stable isotope values (δ13C and δ15N) were measured in experimental diets and shrimp muscle tissue and results were incorporated into a three-source, two-isotope mixing model. The relative contributions of dietary nitrogen, carbon and total dry matter from FM, SP and CG to growth were statistically similar to the proportions established in most of the diets after correcting for the apparent digestibility coefficients of the ingredients. Dietary nitrogen available in diet 33FSG was incorporated in muscle tissue at proportions representing 24, 35 and 41% of the respective ingredients. Diet 50GSF contributed significantly higher amounts of dietary nitrogen from CG than from FM. When the level of dietary nitrogen derived from FM was increased in diet 50FSG, nutrient contributions were more comparable to the available dietary proportions as there was an incorporation of 44, 29 and 27% from FM, SP and CG, respectively. Nutritional contributions from SP were very consistent to the dietary proportions established in the experimental diets. [Copyright &y& Elsevier]

Abstract: The role of dietary protein source on growth performance and lipid metabolism in European sea bass (Dicentrarchus labrax) was investigated, by the evaluation of fat content in different tissues, plasma metabolites, liver lipogenic activity and fatty acid composition of dorsal muscle tissue. Five isonitrogenous (490gkg−1 crude protein dry-matter basis) and isolipidic (170gkg−1 lipid dry-matter basis) diets with graded levels of wheat gluten, soybean and pea meal in substitution of fish meal were evaluated in European sea bass (initial body weight 23.9±0.1) for 96days. There was a significant difference (p<0.05) in dorsal muscle and liver lipid contents. Plasma glucose and cholesterol levels decreased significantly (p<0.05) as diet included soybean and wheat gluten meal (p<0.05). The composition of fatty acids in muscle triacylglycerols and phospholipids was affected by vegetable sources as n−6 PUFA percentage was significantly increased and n−3 PUFA percentage was significantly decreased (p<0.05), without modifying EPA/DHA ratio, when wheat gluten and pea meal were included in the diet. The results confirm that the quality and quantity of vegetable protein source could affect lipid metabolism and lipid content in the dorsal muscle of the European sea bass and suggest the possibility of manipulation of the diet for commercial purpose. [Copyright &y& Elsevier]

Abstract: The development of cost-effective and growth-promoting diets for Florida pompano (Trachinotus carolinus L.) is necessary for a feasible pompano aquaculture industry in the United States. However, research efforts to reduce the utilization of marine ingredients in aquatic feeds are needed to accomplish such a goal. Three independent growth trials were conducted to evaluate the replacement of fishmeal in the diet of Florida pompano. The basal diets were formulated to contain 40% crude protein and 10% lipid using solvent extracted soybean meal and corn gluten as the primary and fixed protein sources. In Trial I (10weeks) the basal diet containing 15% fishmeal (FM15) was modified by the isonitrogenous replacement of fishmeal with poultry by-product meal resulting in diets containing 10% (FM10), 5% (FM5) and 0% (FM0) fishmeal. In Trial II (12weeks), the FM0 diet was supplemented with methionine (M), lysine (L), and taurine (T), serving as the basal diet (MLT) for the evaluation of potential limitations in these amino acids. By deleting individual amino acids, test diets without methionine (LT), lysine (MT) or taurine (ML) supplements were formulated. In Trial III (8weeks), the FM0 diet from Trial I served as the basal diet (0% Tau) for the evaluation of potential limitations in taurine. Fish in replicate tanks (n=3) were fed one of the randomly assigned test diets two times daily. The total replacement of fishmeal in Trial I resulted in depression of fish performance while the performance of fish offered test diets with 5–15% fishmeal did not differ significantly. Reductions in weight gain (from 338.1 to 260.4%), feed efficiency (from 0.53 to 0.40), protein and energy retention (from 19.6 to 12.4% and from 20.4 to14.2%, respectively) were observed in fish fed the FM15 and FM0 diets, respectively (P<0.05). In Trial II, growth performance of pompano did not change (P>0.05) by the removal of supplemental methionine, lysine or taurine from the FM0 diet albeit, numerically the removal of taurine produced the smallest fish. In Trial III, the supplementation of taurine to the FM0 diet at 0.75g/100 (0.75% Tau) improved the weight gain (from 587.7 to 773.3%), feed efficiency (from 0.50 to 0.64), and protein retention (from 20.5 to 24.3%) of pompano (P<0.05). Based on these results, we concluded that poultry by-product meal is a good alternative ingredient for fishmeal in the diet of Florida pompano and that this species appears to have a minimum dietary requirement for taurine. [Copyright &y& Elsevier]

Abstract: The intention of this study is to investigate the effect of fish meal soluble protein quality on growth and protein utilisation of Atlantic salmon fed very low fish meal diets. For this purpose stickwater (SW) was separated during herring meal production, fractionated following successive micro- ultra- and nano-filtration steps and reintroduced in the press cake (PC) in order to produce 4 reconstituted fish meals containing different molecular size soluble protein mixes. The SW fractions used for the production of the experimental fish meals were: 1) the micro-filtration (MF) retentate, 2) the ultra-filtration (UF) retentate, 3) the nano-filtration (NF) retentate and 4) the nano-filtration permeate. Four very low fish meal experimental diets were prepared containing 25gkg−1 super prime fish meal and 50gkg−1 diet of one of the 4 experimental fish meals produced. A positive control diet was prepared containing 300gkg−1 diet super prime fish meal. Three more diets were prepared containing 25gkg−1 diet super prime fish meal and 50gkg−1 diet PC. Two of them were supplemented with either crystalline taurine, or crystalline hydroxyproline, up to the levels present in the high fish meal control diet. The experimental diets with the SW fractions contained similar levels of water soluble protein (WSP), which were higher than in the PC diets and lower than in the control. All diets were iso-nitrogenous, iso-lipidic and iso-energetic and were fed to 8 triplicate groups of salmon (80 fish per group of initial body weight 133g), for 69days. High growth rates and low fish in-fish out ratios (FIFO) were achieved in salmon fed all the very low fish meal diets. Feed intake, fish body growth, whole body protein content, protein gain and morphometry were significantly affected by the inclusion of the different SW fractions in the low fish meal diets. The medium size peptides (UF retentate) induced significant increase in feed consumption in salmon and supported higher fish growth compared to the highest (MF retentate) or the lowest molecular weight peptides (NF permeate) where both feed intake and fish growth were reduced. The fish fed the diet containing the NF permeate had significantly lower growth compared to the diets containing the other SW fractions. We did not find any benefits for salmon performance by the supplementation of taurine or hydroxyproline alone to the low WSP PC diets. The present work gives evidence on the multi-dimensional effects of the different marine water soluble components on fish performance. In order to identify novel, high added-value, water soluble marine compounds, advanced large scale separation technologies must be further developed and applied in studies investigating specific functional effects that these compounds may have on fish and other organisms. [Copyright &y& Elsevier]

Abstract: The use of carob seed germ meal (CG) as a substitute for fish meal was evaluated in fingerlings (average weight 10g) of gilthead sea bream fed isonitrogenous (46% Crude Protein, CP) and isolipidic (19.5% Crude Lipid, CL) diets containing four CG levels (0, 17, 34 and 52%). The duration of the trial was 83days. The diets were tested in triplicate, and the fish were fed to satiation twice daily. The apparent protein and energy digestibility coefficients decreased in response to the dietary inclusion of CG. The decreases in the values of the ADC ranged from 93% for the 0 diet to 80% for the 52 diet. The amount of digestible Arg in the diets increased with the inclusion of CG, from 3.2g Arg 100g−1 in the 0 diet to 4.81g Arg 100g−1 in the 52 diet. The digestible Arg content increased in the diets because the amounts of the remaining digestible amino acids decreased. The fish reached weights of 72, 72, 69 and 53g on the 0, 17, 34 and 52 diets, respectively. The 52 diet gave the lowest specific growth rate (SGR, 1.95%day−1) relative to those found for the other three diets (2.32%day−1). The 52 diet produced the least satisfactory results for feed intake (FI) and the food conversion ratio (FCR) (2.23g 100gfish−1 day−1 and 1.38, respectively). The efficiency of retention of His, Phe and Leu in the fish fed the 52 diet showed the lowest values (17.3, 25.5 and 28.5%, respectively), but the efficiency of retention of Met in the fish fed the 52 diet showed the highest value (48.2%). In the distal intestine and liver, histological alterations were found in the fish fed the 34 and the 52 diets. In fish fed the 52 diet, the mucosal fold was significantly shorter and thinner and exhibited a smaller number of goblet cells. These changes could affect nutrient uptake by modifying the digestibility of the diet. The histology of the liver did not show severe degradation in any treatment. The results of the present experiment demonstrated that CG can be included at levels up to 34% in diets for short term feeding of gilthead sea bream without any adverse effects on fish growth and nutritive parameters. [Copyright &y& Elsevier]

Abstract: The objective of the experiment was to evaluate the effects of ingredient, extrusion temperature, and the conjugated acid salt sodium diformate (HCOOH··HCOO-Na; NaDF) on apparent nutrient digestibility and physical quality of diets for rainbow trout. The experiment had a 23 factorial design with two dietary ingredient sources (fish meal [FM] and barley protein concentrate [BPC]), two extruder temperatures (110 and 141°C), and two levels of NaDF supplementation (0 and 10.6gkg−1). The results from the digestibility trial showed that inclusion of BPC significantly increased the digestibility of crude protein and several non-essential amino acids (NEAAs), but significantly reduced the digestibility of crude lipid, starch, and all essential amino acids (EAAs). Extrusion at 141°C significantly increased the digestibility of starch, crude protein, arginine, and several NEAAs, but significantly reduced the digestibility of phenylalanine compared to extrusion at 110°C. Addition of NaDF significantly increased the digestibility of most major nutrients and individual amino acids. Diets with BPC had significantly higher hardness, expansion ratio, and durability, but significantly lower water stability compared to diets based on FM. Extrusion temperature only affected pellet durability, which was significantly higher for the highest temperature. Addition of NaDF to diets significantly increased the expansion ratio, durability, and water stability compared to diets without NaDF. This experiment showed that BPC is a promising alternative protein source to FM with regard to nutrient digestibility and physical quality of extruded diets. The use of high extrusion temperature (141°C) and inclusion of NaDF improved both nutrient digestibility and physical quality of diets for rainbow trout. [Copyright &y& Elsevier]

Abstract: Long-term effects of feeding high-energy, low-fishmeal feeds on growth and flesh characteristics were investigated in ~1–4.5kg Atlantic salmon (Salmo salar). Feeds were a high-fishmeal control (HFM; 20% fishmeal of total feed ingredients), medium-fishmeal (MFM; 15%), and low-fishmeal (LFM; 10%). Growth and feed utilisation were assessed regularly over a 9month growth trial, and flesh characteristics (fillet fat, pigment concentration, visual colour) were monitored at ~1kg weight intervals. These were expanded to include instrumental colour and texture analyses and sensory evaluation in harvest-size (ca. 4.5kg) salmon. There were no significant differences between feed treatments with respect to growth, feed utilisation, mortality and flesh characteristics; confirmed by a lack of cluster formation in a multivariate principal component analysis (PCA). The most pronounced correlations were found between flesh pigment and a*-value, SalmoFan, hue and intensity, between muscle fat and pigment, and between fat and sensory attributes (odour, taste, flavour, texture and colour). This study demonstrates that dietary fishmeal levels can be substantially reduced from present commercial levels without compromising growth performance or flesh quality of harvest-size salmon. [Copyright &y& Elsevier]

Abstract: Defatted and heat-treated soybean meal (SBM) was fermented using compound bacteria predominantly Bacillus spp. under two different fermentation conditions until the material temperature reached 80°C: initial water addition of 30% (fermented for 7h, FSBM-1) and 45% (10h, FSBM-2). A fish meal-based diet and three non-fish meal diets containing SBM, FSBM-1 or FSBM-2 each at a 47.6% level with a 21.0% level of corn gluten meal were fed to rainbow trout (initial BW, 14.7g) for 10weeks. The growth and feed efficiency ratio of fish fed SBM diet and FSBM-1 diet were inferior to those of fish fed FM diet and FSBM-2 diet. Lower digestibility values of carbohydrates and lipids, especially of polar lipids observed in fish fed SBM diet were improved by the fermentation (SBM

Abstract: Triplicate groups of 150g Atlantic cod juveniles (Gadus morhua) previously fed a phosphorus (P) depleted diet for 19days, were fed 1 of 6 experimental diets with variable P and calcium (Ca) supplementation levels for 91days. Fish muscle meal, low in P and Ca, was used as basal protein raw material in the diets, whereas additional P and Ca were supplemented as soluble minerals (KH2PO4, NaH2PO4, CaSO4). Diets 1 (D1) and 2 (D2) were not supplemented with P. Diet 3 (D3) was supplemented with 0.3% P and diets 4 (D4) and 5 (D5) with 0.6% P. D2, D3 and D4 were supplemented with 0.88% Ca. Fish from all diets at least doubled their weight during the experiment, but no significant differences in daily growth or feed intake were found among the different treatments (P>0.05). With increasing dietary supplementation of P, significant increase in fork length (P<0.05) and a tendency for higher growth rate and improved feed efficiency was observed. Calcium supplementation had no effect on growth rates, feed efficiency or P utilisation efficiency. Dietary P and Ca supplementations significantly affected whole body and vertebrae proximate composition, fish morphometrics and apparent digestibility coefficients (ADC) of protein, lipid, energy, P, Mn, Fe, Ca and Se (P<0.05) and further significantly affected macro- and micro-mineral status in whole body and vertebrae, but not in plasma. A large number of deformed fish were identified by radiography, but there were no significant differences in the occurrence of vertebral deformities between dietary groups. However, it was obvious from the X-rayed fish that all fish fed the P deficient diets had poor bone mineralisation status whereas all those fed the P supplemented diets had apparently adequate bone mineralisation status. [ABSTRACT FROM AUTHOR]

Abstract: Intestinal microbiota and host inflammatory marker gene expression were characterized in rainbow trout (Oncorhynchus mykiss) during a feeding trial designed to determine the digestibility of soybean meal and fish meal. The trial was conducted in a freshwater, biofiltered recirculating aquaculture system in Saskatoon, Canada. Intestinal contents and tissue were collected from nine fish on each of the two experimental diets and a synthetic, casein-based reference diet. Total DNA from contents of each group was pooled to create template for PCR and construction of libraries of cloned cpn60 universal target sequences. A total of 3357 sequences were produced. The most frequently observed sequences were similar to Firmicutes (particularly Carnobacterium maltaromaticum) and Gamma Proteobacteria, including enterobacteria genera Hafnia, Pseudomonas and Aeromonas. The fish meal diet associated microbiota was balanced between Gamma Proteobacteria and Firmicutes while the soybean meal diet associated microbiota was less diverse and dominated by C. maltaromaticum. Species-specific qPCR of several bacterial species revealed a large amount of variation in target abundance between individual fish. Analysis of inflammatory marker genes including proliferating cell nuclear antigen (PCNA), immunoglobulin M (IgM), and interleukin-1 beta (IL-1β) showed a significantly higher level of PCNA associated with the reference diet and a non-significant trend of elevated IL-1β, suggesting that the semi-purified reference diet may be associated with sub-acute intestinal damage. A high level of variation between individual animals was also observed in the gene expression analysis. An examination of correlations within the combined results support the model that diet effects on the fish intestine include indirect effects mediated through modifications of the intestinal microbiota. These results illustrate the benefits of collecting experimental data from individual fish to increase the analytical power of results. [Copyright &y& Elsevier]

Abstract: The sustainable composition of diets of high nutritional value is of the utmost importance for intensive aquaculture. Digestion and absorption of nutrients depend on the activity of the digestive enzymes, in particular those located in the brush border membrane of enterocytes, which are responsible for the final stages of breaking down and absorption of nutrients. In the present study, the substitution of fish meal by lupin or rapeseed meal in the diet was evaluated on gilthead sea bream (Sparus aurata) and goldfish (Carassius auratus). The objectives were to compare the activities of intestinal brush border enzymes in both species fed the control and experimental diets. When gilthead sea bream were fed the vegetable diets, significantly lower activities compared with the control group were observed for alkaline phosphatase and γ-glutamyl transpeptidase, but these differences were not significant in goldfish. Maltase activity was found decreased in the group fed lupin meal, both in sea bream and in goldfish. However, in spite of these differences in enzyme activities, growth characteristics of the fishes were similar with the three diets. It seemed that both fish were able to adapt to partial substitution of fish meal, but it remains to investigate the mechanism for compensating the decrease in specific enzymatic activity in the enterocytes of carnivorous gilthead sea bream. [Copyright &y& Elsevier]

Abstract: Three forms of pea seed meal (native - NAT Diet, autoclaved - AC Diet and dry cooked - DC Diet) were evaluated in balanced diets for common carp fry (Cyprinus carpio L.) replacing solvent extracted soybean meal protein in a fish meal / soybean meal based control diet (CTR Diet). After a 49- day growth trial, weight gain, feed conversion ratio, protein efficiency ratio and apparent net nitrogen utilization of fish fed the fish meal / soybean meal diet (CTR Diet) and of that fed the pea seed meal subjected to different thermal treatments were determined. Significant differences (P<0.05) were found in the mean final weight (MFW) and specific growth rates (SGR) between fish fed the CTR and NAT Diets (i.e., mean final weight: 30.69 and 25.70g, respectively; SGR: 2.84 and 2.51g, respectively). The mean final weight of carp fed the autoclaved pea seed meal diet (MFW 28.40g, AC Diet) and the group fed the dry cooked pea seed meal diet (MFW 29.34g, DC Diet) were not deemed significantly (P>0.05) different to those of carp fed the fish meal / soybean meal control diet. A sequential digestibility study was also undertaken to complement the growth trial. Apparent nutrient and energy digestibility coefficients (ADCs) reflected a similar trend as results in the first trial. Apparent nutrient and energy digestibility coefficients were found to be highest when fish were fed the CTR Diet. Apparent digestibility coefficients of carp fed the AC and DC Diets were generally higher than that of the NAT Diet. Overall, ADC''s of fish fed the DC Diet were generally higher than that of the AC Diet. It can be concluded that thermal treatment can nutritionally modify pea seed meal to some extent: the dry heating treatment proved to be slightly more effective than the moist heat treatment in terms of growth performance, feed utilization efficiency and apparent digestibility in common carp. [Copyright &y& Elsevier]

Abstract: We report performance of rainbow trout (Oncorhynchus mykiss) fed a balanced dietary mix of plant proteins supplemented with either fish bone meal (FBM) derived from Alaskan seafood processing byproducts or dicalcium phosphate. Seven experimental diets were formulated to contain two levels of dicalcium phosphate or two levels of two different kinds of FBM in all plant-protein (APP) based diets as follows: Diet 1, FM based; Diets 2 and 3, APP diets with low or high dicalcium phosphate; Diets 4 and 5, APP diets with 4% or 8% low phosphorus FBM; and Diets 6 and 7, APP diets with 2.7% or 5.4% high phosphorus FBM. The limiting amino acids methionine and lysine, as well as the amino sulfonic acid taurine, were added to the APP diets at appropriate concentrations. Triplicate groups of juvenile rainbow trout (average weight 31.5g) were fed one of the seven experimental diets for 12weeks. Negative effects on growth performance and feed utilization were observed in the fish fed both kinds of FBM or the low level of dicalcium phosphate supplemented to APP diets. Fish fed high levels of dicalcium phosphate showed growth performance and feed utilization that was not significantly different from the control group indicating that FM may be completely replaced by plant proteins with appropriate dietary supplements. Significantly decreased ash levels and increased lipid content were observed in fish fed diets supplemented with FBM or dicalcium phosphate at low levels. Whole-body phosphorus level was not significantly different between controls and fish fed APP diets supplemented with dicalcium phosphate whereas phosphorus levels were significantly lower in FBM fed fish. The apparent digestibility coefficients (ADC) of protein and phosphorus were lower in the control diet than diet 3. The digestibility of the two kinds of FBM was not different. Therefore, the results indicate that total replacement of dietary FM solely by plant proteins could be possible in rainbow trout with no apparent reduction in growth performance or feed utilization when a balanced mix of plant protein ingredients is properly supplemented with highly available inorganic phosphate, limiting amino acids and taurine. Maintenance of the body Ca/P ratio close to 1 was also found in rainbow trout although the differences in diets were considerable. Alaskan FBM could be used in fish feeds as a supplemental calcium source but not as the primary source of phosphorus because of the low bioavailability of phosphorus to fish in these diets. [Copyright &y& Elsevier]

Abstract: Two five-week growth trials were conducted using mixture methodology to optimize a reference diet for Pacific white shrimp, Litopenaeus vannamei, (0.47g and 0.41g initial weight in Trial 1 and Trial 2, respectively) using krill meal (Trial 1 only), menhaden fishmeal, squid meal, and soy protein isolate (SPI). In Trial 1, the combination of ingredients yielding the highest final weight was fish:squid:SPI:krill 34.1:44.9:20.2:0.8. Because of its relative ineffectiveness, krill meal was removed in Trial 2. The optimum combination of ingredients was fish:squid:SPI 0.0:80.6:19.4%. Increasing SPI beyond 20% relative inclusion rapidly reduced final weight. Both trials indicated that a blend of marine ingredients and SPI base mixes at a ratio of approximately 4:1 optimized the final weight of the shrimp. In Trial 2, fishmeal was found to be marginally lower in nutritional quality than that of squid meal. These results indicate that mixture methodology is effective in optimizing diets for shrimp. [Copyright &y& Elsevier]

Abstract: Aquaculture feeds for carnivorous finfish species have been dependent upon the use of fish meal as the major source of dietary protein; however, the increasing demands upon the finite quantity of this high-quality protein source requires that feeds become increasingly comprised of alternative plant and/or animal protein. Soybean meal has been has been used to partially replace fish meal in the diets of several fish but it is known to cause enteritis in Atlantic salmon, Salmo salar. We have compared two groups of juvenile (207.2±6.6g) Atlantic halibut, Hippoglossus hippoglossus, L., fed diets containing fish meal (FM; control) or 30% soybean meal (SBM; experimental) as a protein source for 3weeks. No detectable difference in feed intake or palatability was evident with the SBM diet relative to the FM diet. Histological examination of the distal intestine was performed to examine leukocyte infiltration of the lamina propria and other changes in morphology commonly observed with soybean-induced enteritis of salmonids. No significant difference was found between fish fed the FM and SBM diets. Global gene expression profiling performed using a high-density oligonucleotide microarray containing 9260 unique features, printed in quadruplicate, from Atlantic halibut revealed subtle underlying changes in the expression of several immune genes and genes involved in muscle formation, lipid transport, xenobiotic detoxification, digestion and intermediary metabolism. These results indicate that SBM can be used successfully as a replacement for animal protein in diet for juvenile Atlantic halibut, although long-term effects on the immune system may ensue. [Copyright &y& Elsevier]

Abstract: The suitability of sunflower meal (SFM) as a substitute for fish meal was evaluated in sharpsnout sea bream fingerlings (14g) by feeding diets in which 0, 10, 20 or 30% of crude protein provided by fish meal was substituted with SFM. The experiment lasted 125days and survival at the end of the experiment was 95%. The effect of SFM level on growth parameters were not significant (P <0.05). Fish were hand-fed to apparent satiation and feed intake ratio was not affected by SFM inclusion in the diet. Final live weight was 100g for all fish fed all diets. Nutritional and biometric parameters were not affected by SFM substitution, but in body composition fish fed the diet with 20% of crude protein replaced by SFM substitution showed the lowest crude lipid level and the highest moisture content. Crude protein efficiency, gross energy efficiency and amino acid composition and retention of fish fed the various diets did not reach statistical differences. No histological alteration were found in liver, but an increment in goblet cells was observed in mucosa folds, perhaps as a consequence of SFM substitution or due to the high content of arginine and aspartate, known to be responsible for some immune responses. The results of this experiment demonstrated that SFM can supply up to 30% of crude protein in diets for feeding sharpsnout sea bream juveniles without any adverse effect on fish growth, liver and gut histology and amino acid composition and retention. [Copyright &y& Elsevier]

As a kind of biologically active molecule, hydroxyproline (Hyp) is abundant in fish meal (FM) but not in plant protein sources. It remains very challenging to replace FM with plant protein sources, particularly for carnivorous fish. This study aims to investigate the effect of dietary Hyp supplementation on Chinese perch (Siniperca chuatsi) fed with FM partially replaced by fermented soybean meal (FSM), with 46% FM as the positive control and 31% FM plus 15% FSM as the negative control. Based on the negative control diet, 0.5%, 1%, 1.5% and 2% of dietary crystal L-Hyp was supplemented to formulate four experimental diets, respectively. Although the replacement of 15% FM with FSM in the feed resulted in a significant decline in growth performance of Chinese perch, dietary supplementation of 1% Hyp could improve the growth performance with high mRNA levels of the gh and igf1 genes. Piecewise regression analysis revealed that a dietary level of 2.27% Hyp could achieve the maximum weight gain rate. With high mRNA levels of orexigenic genes (npy and agrp in the brain, and ghrelin in the gut) and low mRNA levels of anorexigenic genes (pomc and cart in the brain, and leptin-A in the liver), an appropriate level of Hyp could be added to the diet of Chinese perch as a food attractant to promote the appetite and increase food intake. Besides, partial replacement of FM with FSM might promote the deposition of amino acids in the muscle, which may not be affected by dietary supplementation of Hyp. Furthermore, dietary supplementation of Hyp affected the activity of prolyl hydroxylase (PHD) and the mRNA levels of type I collagen regulatory genes and coding genes of three prolyl 4-hydroxylase (P4H) isozymes in the muscle of Chinese perch to some extent. In addition, supplementation of an appropriate level of Hyp could significantly improve the collagen content and muscle quality (hardness, chewiness and springiness) of Chinese perch, which may greatly enhance its edible and nutritional values. • Dietary 1% Hyp supplementation can improve the growth performance and promote the appetite of Chinese perch, which may counteract the negative effect of FSM replacement. • An appropriate amount of Hyp may be added to the diet of Chinese perch as a food attractant with the regulation of appetite genes. • Dietary supplementation of an appropriate amount of Hyp may significantly improve the collagen content and muscle quality of Chinese perch. [ABSTRACT FROM AUTHOR]

A sustainable growth of the aquaculture sector implies the use of sustainable novel raw materials as replacers of the traditional fishmeal (FM) and fish oil (FO) ingredients. This fact has led to the development of sustainable and functional diets as part of a management strategy to reduce the effects on fish growth performance and health derived from low FM/FO dietary contents. In this sense, Antarctic krill (Euphausia superba) is considered a potential candidate in dietary inclusions to potentiate fish growth and health status. In this study, European sea bass (Dicentrarchus labrax) were fed a practical diet with either a 15% fishmeal content (KM0; control diet) or the same diet substituted by 30% (KM5; 50 g KM/kg diet) or 50% (KM7.5; 75 g KM/kg diet) Antarctic krill meal (KM) for 12 weeks in triplicates. At the end of the feeding trial, growth performance, liver morphology, liver proximate composition, lipid classes and fatty acid profiles, as well as the expression of hepatic genes related with lipid metabolism were evaluated. Fish fed KM-based diets presented higher (p < 0.05) final weight, protein and lipid efficiency ratios, specific growth rate (SGR) and improved feed conversion ratio (FCR), irrespective of the KM dietary level. Whole body and muscle proximate composition and fatty acid profiles were similar among dietary groups. Livers of European sea bass fed the experimental diets presented similar (p > 0.05) biochemical composition and fatty acid profile. However, smaller hepatocellular area and lower grade of cytoplasm vacuolization as well as a better alignment around sinusoidal spaces were found. The analyses of liver lipid classes revealed a positive correlation between the level of dietary KM and the pigmented material such as astaxanthin and free fatty acid content, as well as a negative correlation with the cholesterol levels. The expression of hepatic genes studied demonstrated a downregulation of 3 -hydroxy-3-methylglutaryl-coenzyme A reductase (hmgr) and delta-6-desaturase (fads2) expression levels in fish fed KM-based diets. Besides, gene expression levels of fatty acid binding protein 7 (fabp7) and lipoprotein lipase (lpl) were significantly correlated with KM dietary levels. Altogether, these results profile KM as a potential promoter of growth and liver health in European sea bass fed low fish meal and oil diets. • Dietary krill meal (KM) enhances D. labrax growth performance and feed efficiency. • Dietary KM reduces D. labrax hepatocytes size and cytoplasmatic vacuolization. • Dietary KM reduces liver cholesterol and increases free fatty acid contents. • Dietary KM did not affect muscle proximate and fatty acid composition. • Dietary KM as FM replacer downregulates hmgr and fads2 liver gene expression. [ABSTRACT FROM AUTHOR]

Four growth trials were conducted to evaluate the effects of fishmeal replacement with various levels of soybean meal (SBM) and poultry byproduct meal (PBM) on growth performance in practical diets for juvenile and sub-adult red snapper, Lutjanus campechanus. In addition, the need for taurine and palatability enhancement (krill meal) were evaluated in the high SBM, low fishmeal diet. Across the trials, ten diets were formulated to contain 36% protein and 10% lipids. All diets except for one included a taurine supplement of 1%. A supplement of 5% krill meal was added as an attractant to one of the low fishmeal and high SBM diets to explore potential palatability issues associated with plant-based proteins. No statistically significant differences were found between the performance of the basal diet and the PBM replacement diets, indicating that PBM is a suitable replacement for fishmeal in red snapper diets. On the contrary, a clear negative linear relationship was observed with increasing levels of SBM replacement. The reduced growth performance of high SBM inclusion diets is unlikely to be due to palatability issues, as no significant difference was observed between the performance of the high SBM diet with krill meal and an identical diet without krill meal. The significant reduction in growth observed in snapper fed a diet lacking a taurine supplement indicates that red snapper have a taurine requirement that is limiting at low (0.2%) levels. Gut samples were taken from fish that received the SBM diets to determine if reduced growth performance could be attributed to inflammation. However, no statistically significant difference was observed, indicating that reduced growth was not necessarily the result of a hypersensitivity reaction. Further investigation will be necessary to determine the optimal taurine requirement and required dietary supplements to improve the performance of low fishmeal feed formulations. • Fishmeal was replaced with soybean meal (SBM) and poultry by-product meal (PBM). • 100% fishmeal replacement with PBM showed no difference in growth of red snapper. • Negative linear relationships between growth and increasing levels of SBM in diets • The addition of krill meal as an attractant did not improve growth performance. • Red snapper have a taurine requirement. [ABSTRACT FROM AUTHOR]

Two trials were conducted to test the effect of partial replacement of fishmeal by two brewery industry by-products, yeast and spent grain, included in isoproteic and isolipidic diets for gilthead sea bream (Sparus aurata), having in mind the commercial availability of these by-products. According to the obtained results, the inclusion of up to 30% brewers' spent yeast and 15% spent grain in the feed for gilthead seabream gave similar results in terms of growth, food conversion and fillet final composition to a feed with fish meal as the main protein source and show a protein digestibility of 89–95%. Taking into account that these by-products are produced in large quantities in Europe, they can be a potential source of protein to reduce the use of plant proteins or fish/animal by-products (trimmings) and increase the sustainability of both sectors, brewery industry and aquaculture. • Spent yeast and spent grain are highly digestible by seabream and can be included up to 30% and 15%, respectively. • Seabream growth and conversion using these by-products are similar to those obtained using a commercial feed. • Final fillet quality of gilthead seabream is similar to that obtained using a commercial feed. [ABSTRACT FROM AUTHOR]

Polyphenols are well known for its benefits to improve the antioxidant capacity and inflammation response in human but their positive response and underlying mechanism is not yet well established in fish. Therefore, a 60-day feeding trial was conducted to explore the effects of apple polyphenols (AP) for improving the health of grass carp. Fish were fed with plant protein based diets supplemented with 0, 1, 5, and 10 g of AP per kg. Results of the study showed that highest (10 g/kg) supplementation of AP exhibited lower growth of fish compared to other groups. Dietary inclusion of AP exhibited hepatoprotective effects via decreasing the activities of serum alanine aminotransferase, aspartate aminotransferase and γ-glutamyl transaminase (P < 0.05), and hypocholesterolemic effects. AP supplementation improved the antioxidant status in terms of high level of antioxidant parameters in serum and intestine tissue, followed by a reduction in malondialdehyde content (P < 0.05). Antioxidant capacity was improved by AP via activation of Nrf2, and over expression of catalase and copper/zinc superoxide dismutase (P < 0.05). Additionally, AP supplementation exerted an anti-inflammation effect through the inhibition of TLR4 signaling pathway, followed by a notable decrease in the transcription of pro-inflammatory cytokines like IL-1β, IL-6, and TNF-α (P < 0.05). Thereafter, an enhancement of intestinal barrier function was observed in AP1, AP5 and AP10 groups in terms of overexpression of junction proteins such as ZO1, ZO2, ZO3, and Occludin (P < 0.05). These results documented that AP exhibited beneficial impacts on the health of grass carp through improving antioxidant capacity, suppression of inflammatory responses, and enhancement of intestinal barrier function. Overall, optimal dose of AP for grass carp is 5 g/kg diet. • β-Glucan, inulin and emodin displayed hepatoprotective effects on grass carp. • Three additives significantly improved antioxidant capacity via Nrf2 activation. • Three additives attenuated the intestinal inflammatory responses. [ABSTRACT FROM AUTHOR]

A trial was conducted to test the effect of partial replacement of fishmeal by two brewery industry byproducts, yeast and spent grain, included in isoproteic (41% CP) and isolipidic (22% CL) diets for gilthead sea bream (Sparus aurata) and rainbow trout (Oncorhyncus mykiss), having in mind the availability of these byproducts. A first step before an ingredient is included in a commercial feed is to evaluate the nutritional quality of these raw materials by measuring their digestibility. Thus, the apparent digestibility coefficients of the diets and ingredients were determined after a 30 days feeding trial and faecal collection. Apparent digestibility coefficients of these by products in the case of rainbow trout varied between 75 and 88% whereas for gilthead seabream was between 71 and 88%. According to the results obtained, the inclusion of 20–30% of brewers' spent yeast and spent grain in the feed for carnivorous fish either from fresh (rainbow trout) or marine (gilthead seabream) gave similar results to a feed with fish meal as the main protein source and show a good protein, lipid and amino acid digestibility. Taking into account that these by-products are produced in large quantities in Europe, they can be a potential source of protein to reduce the use of plant proteins or fish/animal byproducts (trimmings) and increase the sustainability of both sectors, brewery industry and aquaculture. • Brewery byproducts (spent yeast and spent grain) can be used for the formulation of aquafeeds. • Digestibility of spent yeast and spent grain was good enough to be considered new protein ingredients. • New trials with different inclusion levels of brewery byproducts are envisaged. [ABSTRACT FROM AUTHOR]

Recognizing the importance of reducing fish meals in fish feeds to ensure the economic and environmental sustainability of aquaculture operations, there have been growing interests in using insect meals as a protein source in aquaculture feeds. Increasing number of studies have been conducted to test the effects of insect meals as substitutes of fish meals in feeds of various fish species with varying degrees of success. A meta-analysis was carried out to quantify the effects of insect meals on growth performance of fish. The meta-analysis indicated that in general low or moderate dietary incorporation levels of insect meals did not affect the growth of fish in comparison to fish meal-based diets. High dietary inclusion levels of different insect species appeared to have divergent effects on fish growth. While higher than 29% (±3%) dietary inclusion levels of black solider fly meals depressed the growth performance, yellow mealworm seemed to be well tolerated by fish. Full-fat and defatted black soldier fly meals did not seem to differ in their effects on fish growth performance but this should be viewed as inconclusive due to varying degrees of defatting and highly variable nutrient compositions of the insect meals. Overall the results suggest that insect meals are promising novel protein sources for aquaculture feeds. More research is warranted to further elucidate the various influencing factors on the effectiveness of the dietary inclusions of insect meals in aquaculture feeds, as well as to integrate and translate this information into practical feed formulations. • The effects of dietary inclusion levels of insect meals on fish growth performance were quantified through a meta-analysis. • Fish can utilize moderate levels of insect meals to support growth performance comparable to fish meal-based diet. • The effects of high levels of insect meals seem to be largely dependent on the insect species. [ABSTRACT FROM AUTHOR]

The present study evaluated the replacement of fishmeal (FM) by blends of alternative protein sources in diets for juvenile (8.0 ± 0.5 g) Totoaba macdonaldi. Using a FM-based control diet containing 53% crude protein and 13% crude fat, a 3 × 3 factorial experiment was conducted replacing FM, at levels of 33, 66 and 100% by weight, with three blends of the test ingredients, as follows: 1) Arthrospira meal blend: 70% Arthrospira sp. meal, 15% blood meal, 15% soy protein concentrate (SPC); 2) blood meal blend: 70% blood meal, 15% Arthrospira sp. meal, 15% SPC; and 3) SPC blend: 70% SPC, 15% blood meal, 15% Arthrospira sp. meal. At the end of the 6-week feeding trial, significant effects of the alternative protein blends were detected, in which fish fed the Arthrospira meal and SPC blends had significantly (P <.05) better performance than fish fed the blood meal blend across all growth parameters (percent weight gain and thermal growth coefficient) and feed utilization indices (feed efficiency and protein efficiency ratio). Also, fish fed the former two blends deposited more crude protein and fat in whole body and muscle tissues, concurring with the growth response observed. However, the effects of protein blend on body condition indices (hepatosomatic index, condition factor, and muscle ratio) and on the concentrations of trypsin and chymotrypsin in anterior intestine and pyloric caeca, did not depict clear trends. A correspondence between levels of dietary amino acids (AA) in blends and accumulated AA in muscle, was not observed. However, significant effects of the level of FM replacement were also detected, in which the responses in growth, feed utilization, most body condition indices, and proximate composition of fish whole body, deteriorated as the level of FM replaced increased. All things considered, results indicate that the Arthrospira meal and SPC blends, but not the blood meal blend, can be used to replace at least 33% FM in the diet for totoaba, without adversely affecting growth and survival. The possible reasons for the decreased performance of fish fed the blood meal blend, or when fed any of the blends at levels higher than 33%, are discussed. • Alternatives for fishmeal (FM) were evaluated in diets for Totoaba macdonaldi. • Arthrospira meal, blood meal, and soy protein concentrate (SPC) were tested. • Partial replacement was achieved using Arthrospira meal and SPC. • Up to 33% FM was replaced without adversely affecting fish growth and survival. [ABSTRACT FROM AUTHOR]

As diets fed to juvenile steelhead (progeny of anadromous rainbow trout, Oncorhynchus mykiss) reared in conservation hatcheries contain relatively high levels of protein and lipid supplied primarily by fish meal and fish oil, a 12-week feeding trial was conducted to evaluate alternative ingredients for this species. Using a factorial design, Spirulina meal and a plant oil mixture were evaluated as partial or complete replacements of dietary fish meal and fish oil, respectively. Thus, two diets containing 0 or 50% substitution of Spirulina for fish meal were extruded and top-coated with fish oil or a 63:37 mixture of canola and flaxseed oils. Each of the four dietary treatments was fed to quadruplicate groups of 100 steelhead initially weighing 12.4 g/fish. Steelhead growth rate and feed efficiency were not significantly affected by partial replacement of dietary fish meal with Spirulina , but growth responses were significantly reduced by replacement of dietary fish oil with plant oil. Lipid and protein apparent digestibility coefficients (ADC) were significantly higher in steelhead fed the fish meal diets compared with fish fed the Spirulina diets and significantly higher in steelhead fed the plant oil diets compared with fish fed the fish oil diets. Whole body fatty acid profiles generally reflected those of the diets such that percentages of 18:2n-6 were significantly higher and n-3 polyunsaturated fatty acids (PUFA), including 20:5n-3 and 22:6n-3, were significantly lower in fish fed the Spirulina and plant oil diets compared with those fed the fish meal and fish oil diets. Plasma total cholesterol concentration was significantly reduced in fish fed the Spirulina diets and in fish fed the plant oils diets. Growth results suggest Spirulina is a suitable replacement for 50% of dietary fish meal for steelhead whereas a mixture of canola and flaxseed oil is not suitable as a complete replacement for fish oil in diets for this species. • A feeding trial was conducted to evaluate partial replacement of fish meal with Spirulina meal and complete replacement of fish oil with plant oil. • Growth responses indicated Spirulina was a suitable replacement for 50% of fish meal. • Complete replacement of fish oil with plant oil resulted in significantly lower weight gain and feed efficiency. • Dietary Spirulina and plant oil altered whole body fatty acid percentages resulting in higher 18:2n-6 and lower n-3 PUFA percentages in steelhead. [ABSTRACT FROM AUTHOR]

Selenium (Se) supplementation either as inorganic or organic form was evaluated in Atlantic salmon post-smolt in vivo and in vitro. The basal diet was formulated to be low in fish meal and contain 0.24 mg Se kg−1; six other diets with Se inclusion of 0.15, 0.4, 0.7 or 1.1 mg kg−1 as sodium selenite (SS) and 0.15 or 0.4 mg kg−1 as L-selenomethionine (SM) were formulated from the basal diet. The diets were fed to Atlantic salmon post-smolt (mean initial weight, 216 ± 27 g) in triplicate groups (35 fish tank−1) and reared in flow-through seawater (33 ppt) at 10–12 °C for 9 weeks. At the end of the feeding trial, whole fish and tissues were sampled for in vivo assessment; whereas, liver cells and head kidney leukocytes (HKL) were isolated and their primary cultures used for in vitro assessment following exposure to hydrogen peroxide (H 2 O 2), lipopolysaccharide (LPS) or poly I:C (PIC). Growth, feed intake, feed conversion ratio, specific growth rate, hepato-somatic index, proximate composition and mineral concentration of the whole fish (except for Se) were unaffected by dietary Se (p >.05). Hematocrit was significantly higher in fish fed the 0.4 mg Se supplemented feeds, irrespective of the Se source (p =.02). The Se concentration in whole body, liver, muscle, plasma, kidney and liver/kidney Se ratio increased with increasing dietary Se concentration (p <.0001). Level of oxidised glutathione (GSSG) in liver and head kidney followed a quadratic function (p <.05) indicating that the concentrations were lower at intermediate SS supplementation of 0.4 and 0.65 mg Se kg−1 (total Se, 0.65 and 0.87 mg Se kg−1). Impact of Se sources on glutathione redox status was similar. Slope-ratio analysis revealed SM to be more efficient than SS in improving apparent availability, whole body or tissues Se status, Se retention and reducing Se loss to the environment. In vitro , the mRNA expression of p38mapk and aif , in liver cells were affected by the impact of dietary Se, but not by the treatment of H 2 O 2 (p <.05). In the HKL, the LPS and PIC induced pro-inflamatory action of il-1β , cox2 , nfkβ and viperin were attenuated by SM supplementation, but not by SS (p <.001). Dietary Se supplementation required to the basal diet containing 0.24 mg Se kg−1 was 0.41 mg Se as SS (total 0.65 mg kg−1) or 0.17 mg Se as SM (total 0.41 mg kg−1) based on body Se homeostasis or tissue Se status. SM inclusion at 0.4 mg kg−1 diet (total, 0.65 mg kg−1) attenuated LPS or PIC induced pro-inflammatory responses in vitro. Overall, Se requirement of Atlantic salmon post smolt was 0.27 mg kg−1 diet, on availale basis. Dietary Se level required to maintain body Se homeostasis and improved health status of Atlantic salmon fed plant-based diets (0.65 mg kg−1 diet) exceed the existing EU maximum limit of 0.5 mg Se kg−1 diet. SM as the Se source in salmon feeds has the potential to improve salmon health and reduce Se emissions from Norwegan salmon farming by 60 to 70%. • Impact of selenium (Se) nutrition in Atlantic salmon post-smolt fed low fish meal feeds was studied in vivo and in vitro • Se requirement of Atlantic salmon post-smolt was 0.27 ppm based on body or tissue homeostasis, on available basis • Se inclusion at 0.4 ppm as sodium selenite (total Se, 0.65 ppm) satisfied the Se requirement of Atlantic salmon post-smolt • Inflammatory response to LPS or PIC in head kidney leukocytes were attenuated by 0.4 ppm Se inclusion as selenomethionine • Se emission from Atlantic salmon farming can be reduced by 60-70% by using selenomethionine as Se source [ABSTRACT FROM AUTHOR]

Rigid cell walls of microalgae lower the digestibility and nutrient bioavailability in carnivorous fish. Extrusion is a thermo-mechanical process and a scalable technology that may break cell walls and improves nutrient utilization. It can be hypothesized that certain feed additives may further improve microalgae nutrient digestibility and feed utilization by fish. The aim of the current study was to investigate i) the effect of incorporation of 10% pre-extruded Nannochloropsis oceanica on nutrient digestibility, growth and feed utilization of Atlantic salmon post smolts, and ii) the ability of feed additives in improving the feed utilization. Four low fish meal feeds were formulated; a control without the microalga N. oceanica (CO), a feed containing 10% of the pre-extruded microalga (NC), and two feeds containing 10% of the pre-extruded microalga and supplemented with either 0.06% Digestarom® (ND) or 1% ZEOFeed (NZ). Fish (initial average weight of 227.3 ± 3.4 g) in 5 replicate tanks of each of the study groups were fed one of the experimental feeds for 68 days. The apparent digestibility of dry matter in the NC and NZ groups were significantly higher compared to the control group (CO). The digestibility of lipid was significantly lower, and digestibility of ash was higher in the alga-fed groups (NC, ND and NZ) compared to the control group (CO). The incorporation of 10% pre-extruded N. oceanica in plant-based commercial-like feeds did not affect the growth, feed utilization and whole body proximate composition of salmon. No effects of the feed additives were observed on growth, feed utilization and histomorphology of distal intestine of salmon, but cell proliferation (PCNA) was higher for fish fed the alga alone as well as the alga-ZEOfeed combination. There were no differences in polyunsaturated fatty acids in whole body of fish fed the different feeds. It is noteworthy that whole-body EPA + DHA levels of fish fed the algae feeds were maintained at the same levels as fish fed the control feed that contained 50% more fish meal and 10% more fish oil. • Extrusion was used as pre-processing to improve utilization of Nannochloropsis oceania in plant-based feeds • Digestibility of DM and ash was improved with inclusion of microalgae in plant-based feeds. • Lipid digestibility was reduced in feeds with 10% of microalgae in the feed. • Feed additives Digestarom® and ZEOfeed did not improve utilization of microalgae incorporated feeds. [ABSTRACT FROM AUTHOR]

This study evaluated the dose response to dietary exogenous protease enzyme or malic acid inclusion in plant-based diets on the growth, digestive enzymes and haemato-immunological indices in Nile tilapia, Oreochromis niloticus. Nine isonitrogenous (293 g kg−1 crude protein) and isocaloric (14.80 MJ kg−1 metabolizable energy) diets were formulated to feed juvenile tilapia (average initial weight, 7.56 ± 0.06 g) in a 3 × 3 factorial feeding trial for 84 days. Diets were formulated to contain three levels of exogenous protease (0, 2500 and 5000 U kg−1), and each level was supplemented with three levels of malic acid (0, 5 or 10 g kg−1 diet). The lowest pH level of the stomach and gut was recorded in fish fed diet containing 2500 and 5000 U protease kg−1 at 10 g malic acid. Both protease enzyme and malic acid significantly improved (P <.05) the growth responses of fish. Additionally, the activity of intestinal chymotrypsin, trypsin and lipase were significantly (P <.05) higher in experimental diets containing 2500 or 5000 U protease kg−1 at 5 g kg−1 malic acid. The highest hemoglobin, hematocrit, red blood cells, serum total protein, albumin and globulin values were observed in fish fed diets containing 2500 or 5000 U protease kg−1 at 5 g malic acid kg−1. The optimal activity of alanine and aspartate aminotransferase and alkaline phosphatase was detected in fish fed either 2500 or 5000 U protease kg−1 at 5 g malic acid kg−1. Data suggests that adding exogenous sources of protease enzymes in combination with malic acid at 5 g kg−1 in plant protein-based diet improved growth performance; feed utilization efficiency, digestive enzymes and health status of Nile tilapia. • Malic acid supplementation increased the activity of exogenous protease. • Dietary exogenous enzymes at 5 g kg−1 malic acid increased growth performance and feed utilization. • Dietary exogenous enzymes at 5 g kg−1 malic acid improved digestive enzymes. • Dietary exogenous enzymes at 5 g kg−1 malic acid increased beneficial gut bacterial community. [ABSTRACT FROM AUTHOR]

Fatty acid ethyl esters (FAEE) are a potential alternative to fish oil as a source of polyunsaturated fatty acids in fish feeds. This investigation examined the growth performance, lipid composition, and intestinal and liver histology of rainbow trout (Oncorhynchus mykiss) fed experimental starter diets with graded levels of FAEE and fish oil. Five experimental diets were formulated with 20% total lipid content and 0%, 25%, 50%, 75%, and 100% replacement of Alaskan Pollock oil with FAEE oil, and they were formulated with analogous fatty acid levels. The five diets used defatted fish meal as the primary protein source, and a sixth diet was included that used full-fat fish meal and extracted fish oil. Triplicate groups of rainbow trout (144 ± 20 mg initial weight) were fed experimental diets for 62 days on a restricted feeding regime (4–5.5% biomass/day). The group fed the full-fat fish meal diet had faster growth and a lower feed conversion ratio than the defatted fish meal diet groups after 31 and 62 days of feeding. The growth rate and feed conversion ratios of fish were significantly different between the FAEE-containing diet groups in the first 31 days of feeding, but were not significant from 32 to 62 days of feeding. Fatty acid analysis showed similarity between the fatty acid profiles in experimental diets and in fish muscle and liver tissues at the end of the experiment (all groups mean weight ~3.6 g/fish). Satiation feed intake for a single day was measured at 31 days of feeding, and feed intake was higher in the 100% FAEE diet than the control (8.3 ± 1.1% vs 6.4 ± 0.3% daily satiation ratio). This result suggests that FAEE has a positive effect on voluntary feed intake. Histological analysis of posterior intestine enterocytes and hepatocytes showed a significant reduction in lipid vacuole size in the 100% FAEE group, relative to the defatted and full-fat fish meal control groups. These results suggest that rainbow trout had utilized diet with ≥50% FAEE less efficiently in the first feeding phase, likely due to reduced fatty acid absorption, but that these trends were diminished as fish grew to a larger size. • Test diets were created using Alaskan pollock oil and/or fatty acid ethyl ester (FAEE) oil with analogous fatty acid levels. • Voluntary feeding was greater in the 100% FAEE diet than the control diet (8.3 ± 1.1% vs 6.4 ± 0.3% daily satiation ratio). • Liver and posterior intestine histology results suggest that FAEE oil is not absorbed as efficiently as Alaskan pollock oil. • Up to 25% of fish oil can be replaced with FAEE oil in trout starter feeds without significantly effecting growth rates. [ABSTRACT FROM AUTHOR]

High-quality flesh plays crucial roles in affecting the acceptance and market value of the fish products. In previous study, (2-carboxyethyl)dimethylsulfonium Bromide (Br-DMPT) supplementation enhanced the growth and digestive capacity of fish fed non-fish meal diet, whereas its impacts on fish flesh quality remain unknown. Here, we examined whether dietary supplementation with Br-DMPT could improve muscle nutritive value, flesh flavor, healthy fatty, acids physical properties and antioxidant status in on-growing grass carp (Ctenopharyngodon idella), which fed a fish meal (FM) diet group and five non-fish meal (NFM) diets supplemented with graded Br-DMPT concentrations group (0, 130.0, 260.0, 390.0, 520.0 mg/kg Br-DMPT diet group), respectively. After 60 days feeding trial, we observed that NFM diets with supplementing appropriate Br-DMPT: (1) improved muscle nutritive value and flesh flavor by increasing protein and lipid contents, healthcare fatty acids (docosahexaenoic acid and eicosapentaenoic acid), umami and sweet related amino acids (Aspartic acid, Glutamic acid, Serine, Alanine and Glycine)；(2) accelerated muscle physical properties by increasing tenderness, water holding capacity and pH, and decreasing cathepsin (B and L) activities and lactate content; (3) increased muscle antioxidant status by increasing the activities and gene expression levels of antioxidant enzymes, which appears to be associated with nuclear factor-erythroid 2-related factor 2 (Nrf2) signalling pathway. Importantly, no noticeable difference was observed between 260.0 mg/kg Br-DMPT diet group and FM diet group with respect to the most of above these parameters. Overall, dietary Br-DMPT supplementation improved muscle nutritive values, flesh flavor, healthy fatty acids and enhanced physical properties, antioxidant status of fish. Furthermore, this study further demonstrated that it is feasible for achieving non-fish meal diet application in aquafeeds and also provided a practical data for the non-fish meal diet formulation for aquaculture industry. • Br-DMPT enhanced muscle nutritive value and flesh flavor quality in fish. • Br-DMPT accelerated muscle physical properties in fish. • Br-DMPT enhanced antioxidant capacity in the muscle of fish by modulation of Nrf2 signaling. • The appropriate level of Br-DMPT supplementation for fish flesh quality was estimated to be 298.62-311.74 mg/kg diet. • This study provided a reference for the non-fish meal diet formulation for aquaculture industry. [ABSTRACT FROM AUTHOR]

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

Limited availability of sustainable feed ingredients is a significant concern in salmon aquaculture. Insects may become an important, sustainable resource for expanding the raw material repertoire. Herein, we present data from a 16-week seawater feeding trial with Atlantic salmon (initial body weight, 1.4 kg) fed either a reference diet with a combination of fish meal, soy protein concentrate, pea protein concentrate, corn gluten and wheat gluten as protein source, or a test diet wherein all the fish meal and most of the pea protein concentrate were replaced by black soldier fly larvae meal. The gut health of fish was evaluated using endpoints including organ and tissue indices, histopathology variables and gene expression indicative of lipid metabolism, immune responses, barrier functions and detoxification/stress responses. A higher relative weight of distal intestine was found in fish fed the insect meal diet. Steatosis of enterocytes was observed in the proximal and mid intestine in both diet groups, albeit, less severe in the proximal intestine of fish fed the insect meal diet. Inflammatory morphological changes, similar to those induced in the distal intestine by standard soybean meal, were present in all the examined intestinal segments, with a higher degree of submucosa cellularity in the proximal intestine of insect meal diet fed fish, the only notable diet effect. Few differentially expressed genes were identified in the proximal or distal intestine. In summary, total replacement of fish meal with black soldier fly larvae meal did not compromise the gut health of Atlantic salmon. • Replacement of fish meal with insect meal does not compromise gut health of seawater phase Atlantic salmon. • Reduced enterocyte steatosis in the proximal intestine of fish fed insect meal diet. • Increased relative weight of distal intestine in fish fed insect meal diet. [ABSTRACT FROM AUTHOR]

Modern aquaculture requires the reduction of the feeds cost, which can partly be achieved by minimal use of dietary animal protein. Therefore, this experiment assessing the nutritional potential of using high protein distillers dried grains (HP-DDG) in formulation of affordable striped catfish, Pangasianodon hypophthalmus , diet for more sustainable development of aquaculture. Four diets containing 0, 25, 50 and 75% HP-DDG as partial replacement of fish meal were fed to P. hypophthalmus (108.58 ± 0.17 g fish−1) reared in circular fibreglass tanks (1 m3 adjusted to 0.8 m3; three replicates treatment−1) at an intial stocking density of 30 fish tank−1. The experiment lasted 14 weeks. The results indicated a significant negative linear regression of growth response (SGR and FCR) with increasing fish meal replacement with HP-DDG according to these formula Y = -0.00444*X + 0.724 and Y = 0.00952*X + 1.583, respectively. The reduction of SGR was 16.44 and 32.88%, and the increasing of FCR was 13.66 and 21.74% by 25 and 50% HP-DDG replacement, respectively compared to the control. The whole-body protein content was significantly decreased and lipids increased with the highest HP-DDG inclusion level. The plasma proteins tended to decrease with increasing HP-DDG (%). Therefore, replacing 25% of fish meal by HP-DDG is acceptable for growth and feed utilization. However, the economic revenue indicated the visibility of replacing 50% of fish meal using HP-DDG as determined by feed cost kg−1 gain (Y = 0.0396*X + 12.84) and net income (Y = -0.2908*X + 47.02). Unlabelled Image • This study evaluated the effect of replacing fish meal by high protein distiller dried grains (HP-DDG). • The HP-DDG can replace fish meal partially without disrubting growth performance. • The HP-DDG is an economical alternative to fish meal in the diet of striped catfish. • This work force the sustainable aquaculture production via utilization of industrial ethanol by-product as protein source. [ABSTRACT FROM AUTHOR]