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Compounds from woody biomass are promising candidates as feed additives to improve fish health and welfare of Atlantic salmon (Salmo salar) during the productive cycleng. Thus, conidendrin- and isorhapontin-based extracts (NSEs) from Norway spruce (Picea abies) were evaluated at different levels in a four-week trial. A commercial-like diet (D1) was supplemented with 0.2% of a commercial β-glucan (D2) or with NSEs at 0.02%, 0.1% and 0.2% (D3-D8). No significant differences were found in growth, intestinal morphometry and microbiota at the genus level. Immune-related biomarkers in distal intestine from D5 and D6 indicated an activation of a pro-inflammatory response by the up-regulation of il1b, as in D2. Interestingly, isorhapontin-based extract at higher inclusion level (D8), showed a down-regulation of both pro- and anti-inflammatory- genes, suggesting maintenance of homeostasis. These results showed the importance of source and inclusion levels of bioactive compounds on the regulatory balance associated with fish immune response.

Simple Summary: To promote sustainability in aquaculture, the black soldier fly deserves special attention as an alternative ingredient for aquafeed formulation. The present study proposed the inclusion of spirulina in the growth substrate of black soldier fly prepupae to enrich their final biomass in terms of polyunsaturated fatty acids and antioxidant molecules. The obtained prepupae meal was used as a replacer of unsustainable marine-derived ingredients in diets intended for rainbow trout during a 6-week feeding trial. The results showed that fish zootechnical performances, gut and liver health status, and marketable characteristics were not negatively affected by the experimental diets. In the present study, an organic substrate (coffee silverskin) enriched with spirulina (Arthrospira platensis; 15% w/w), as a source of lipids and bioactive molecules, was used to rear the black soldier fly (Hermetia illucens) prepupae. Three grossly isonitrogenous, isoproteic, isolipidic and isoenergetic experimental diets for rainbow trout (Oncorhynchus mykiss) juveniles were then produced: a control diet (HM0) mostly including fish meal and fish oil, and two other test diets named HM3 and HM20, in which 3 or 20% of the marine ingredients were substituted with full fat black soldier fly prepupae meal (HM), respectively. Experimental diets were provided for 6 weeks, and at the end of the trial the physiological responses and marketable traits of the fish were investigated using a multidisciplinary approach. Generally, all test diets were well accepted, and fish growth, gut and liver health status, and marketable characteristics were not impaired by the experimental diets. However, an increased immuno-related gene expression along with a slight reduction of fillet redness and yellowness was evident in fish from the HM20 group. [ABSTRACT FROM AUTHOR]

Plant-based protein sources, such as soybean, are widely used in fish nutrition due to their market availability, wide distribution and acceptable nutritional quality. However, in some fish species, soybean meal-based diets cause gut inflammation, decreasing both nutrient absorption and growth rates. A suitable alternative to avoid these problems could be the application of additives with anti-inflammatory activity to the diet. In this study, an Aloe vera (Aloe barbadensis Miller, AV) extract was analyzed as a dietary additive to reduce the gut inflammation in Atlantic salmon (Salmo salar) fed with soybean meal (SBM) diet. Fish were distributed in four duplicated groups and fed 28 days with fish meal control diet (FM), AV inclusion diet (AV), FM diet supplemented with AV (FM+AV), SBM diet to induce enteritis and SBM+AV. The fish gut response to these treatments was analyzed in distal intestine by histopathological scores, tissue morphometric measurements and immune gene expression parameters. The score results in fish fed with SBM-based diet clearly showed enteritis, meanwhile fish fed with AV supplemented diet significantly reduced the intestinal SBM signs of damage. These findings were associated to reduction of goblet cells number, lamina propria thickness and sub-epithelial mucosa size, with a significant decrease on pro-inflammatory cytokine il-1β to basal levels, similar to those present in fish fed FM diets. In conclusion, the administration of AV in salmon diet showed a protective intestinal activity against the detrimental effects of SBM, opening the possibility to improve its use as a feed additive in aquafeeds.

The global increase of aquaculture production has caused an escalating demand for alternative protein feed ingredients. Agro-industrial by-products such as sunflower meal are relatively abundant and cheap, but the content of antinutritional factors and fiber in the raw products reduce nutritional value and limit the inclusion levels in the feed for nutritionally demanding species, including salmonids. Solid-state fermentation is a microbial processing method with the potential to reduce the content of fiber and antinutritional factors and improve nutritional value in plant protein raw materials. In this study, Atlantic salmon (Salmo salar) at two commercial-like fish farms were fed experimental diets containing either 5 % non-fermented sunflower meal (as a control diet), 5 % fermented sunflower meal or 10 % fermented sunflower meal. The aim was to compare the effects of fermented sunflower meal on growth performance, gut microbiota, distal intestine histology and gene expression of Atlantic salmon under different environmental conditions. The field trial lasted for 8 and 11 months in a coastal and fjord location, respectively. The findings revealed that diets with fermented sunflower meal sustained growth performance, improved intestinal health by reducing the prevalence of prominent inflammation and ectopic goblet cells, as well as down-regulated the expression of physiological pathways related to tissue damage and cell division. Additionally, 10 % fermented sunflower meal promoted the relative abundance of gut lactic acid bacteria Lactiplantibacillus and Lactobacillaceae after long-term feeding. Our results suggest that fermented sunflower meal is a suitable protein source for Atlantic salmon when included at a level of up to 10 % in the diet. • Fermented sunflower meal reduced prominent distal intestine inflammation. • Fermented sunflower meal reduced the number of distal intestine ectopic goblet cells. • Technical pellet quality was not adversely affected by fermented sunflower meal. • 10 % fermented sunflower meal supported high growth performance under field conditions. • Fish fed fermented sunflower meal had increased gut lactic acid bacteria. [ABSTRACT FROM AUTHOR]

Stress related to salmon aquaculture practices (handling, sub-optimal nutrition, diseases, and environmental problems) may compromise fish welfare. This study describes the effects of two hydrolyzed Debaryomyces hansenii yeast-based products (LAN4 and LAN6) on physiological and immune responses of Atlantic salmon (Salmo salar) parr exposed to short hypoxia stress. A commercial-like diet (control diet: CD) and two experimental diets (CD supplemented with 0.1% of either component LAN4 or LAN6) were fed to fish for 8 weeks. At the end of the feeding experiment, fish were exposed to 1-min hypoxia and samples were collected at 0, 1, 3, 6, 12, and 24 h post-stress. Results showed that plasma cortisol reached a peak at 1 h post-stress in CD and LAN6 groups, whereas no significant increase in cortisol levels was detected in the LAN4 group. Moreover, the LAN6 group enhanced IL-10 responses to hypoxia, when compared to the control and LAN4 group. This suggests a regulation of immunosuppressive profiles in fish fed LAN4. Hypoxia stress increased TNFα in all groups, which indicates that fish may compensate for the short-term stress response, by modulating innate immune molecules. The apparent suppression of hypoxia responses in the LAN4 group coincided with the detection of differences in goblet cells size and Muc-like proteins production in DI; and upregulation (1 h post-stress) of pathways related to oxygen transport, hemoglobin complex, and glutathione transferase activity and the downregulation of fatty acid metabolism (6 h post-stress) in gills. To conclude, a 1-min hypoxia stress exposure affects the response to stress and immunity; and D. hansenii -based yeast products are promising components in functional aquafeeds for salmon due to their ability to counteract possible consequences of hypoxic stress. [ABSTRACT FROM AUTHOR]

Stress related to salmon aquaculture practices (handling, sub-optimal nutrition, diseases, and environmental problems) may compromise fish welfare. This study describes the effects of two hydrolyzed Debaryomyces hansenii yeast-based products (LAN4 and LAN6) on physiological and immune responses of Atlantic salmon (Salmo salar) parr exposed to short hypoxia stress. A commercial-like diet (control diet: CD) and two experimental diets (CD supplemented with 0.1% of either component LAN4 or LAN6) were fed to fish for 8 weeks. At the end of the feeding experiment, fish were exposed to 1-min hypoxia and samples were collected at 0, 1, 3, 6, 12, and 24 h post-stress. Results showed that plasma cortisol reached a peak at 1 h post-stress in CD and LAN6 groups, whereas no significant increase in cortisol levels was detected in the LAN4 group. Moreover, the LAN6 group enhanced IL-10 responses to hypoxia, when compared to the control and LAN4 group. This suggests a regulation of immunosuppressive profiles in fish fed LAN4. Hypoxia stress increased TNFα in all groups, which indicates that fish may compensate for the short-term stress response, by modulating innate immune molecules. The apparent suppression of hypoxia responses in the LAN4 group coincided with the detection of differences in goblet cells size and Muc-like proteins production in DI; and upregulation (1 h post-stress) of pathways related to oxygen transport, hemoglobin complex, and glutathione transferase activity and the downregulation of fatty acid metabolism (6 h post-stress) in gills. To conclude, a 1-min hypoxia stress exposure affects the response to stress and immunity; and D. hansenii-based yeast products are promising components in functional aquafeeds for salmon due to their ability to counteract possible consequences of hypoxic stress.

In the present study, an organic substrate (coffee silverskin) enriched with spirulina (Arthrospira platensis; 15% w/w), as a source of lipids and bioactive molecules, was used to rear the black soldier fly (Hermetia illucens) prepupae. Three grossly isonitrogenous, isoproteic, isolipidic and isoenergetic experimental diets for rainbow trout (Oncorhynchus mykiss) juveniles were then produced: a control diet (HM0) mostly including fish meal and fish oil, and two other test diets named HM3 and HM20, in which 3 or 20% of the marine ingredients were substituted with full fat black soldier fly prepupae meal (HM), respectively. Experimental diets were provided for 6 weeks, and at the end of the trial the physiological responses and marketable traits of the fish were investigated using a multidisciplinary approach. Generally, all test diets were well accepted, and fish growth, gut and liver health status, and marketable characteristics were not impaired by the experimental diets. However, an increased immuno-related gene expression along with a slight reduction of fillet redness and yellowness was evident in fish from the HM20 group.

In this study, we aimed to investigate the inclusion effect of hydrolyzed salmon meal (HSM) in combination with enzyme-treated soybean meal (ESBM) with or without pH adjustment to completely replace dietary FM on the growth, body composition, and the distal intestine condition of the fish. For that purpose, four experimental diets were formulated to be iso-nitrogenous and iso-lipidic and to contain 400 g kg−1 crude protein and 80 g kg−1 lipid. A reference diet contained 150 g kg−1 FM, 450 g kg−1 soybean meal (SBM), and 39.5 g kg−1 ESBM, and the second diet was formulated replacing FM with 190.6 g kg−1 ESBM. The third diet was produced by supplementing 40 g kg−1 hydrolyzed salmon meal (4% HSM) into the diet formulation at the expense of ESBM, and the fourth diet was produced similar with the third diet, but the pH of the diet was adjusted to match the value in the reference diet (4% HSMA). All test diets were supplemented with taurine at the level of 5 g kg−1. Diets were fed to apparent satiation to triplicate groups of Florida pompano juveniles (mean weight 11.88 ± 0.18 g). After 8 weeks of growth, there were no significant differences in the final weight, percentage weight gain, thermal growth coefficient, feed intake, survival rate, and feed conversion ratio in fish offered the various diets. Nor were significant differences observed in the dry matter composition of the fish in all treatments and only minor changes in the histomorphological of distal intestine as the FM was replaced by plant ingredients. Overall, the adjustment of pH level of the diet containing 4% HSMA did not have any significant effect on the growth and physiological function of fish compared to the group of fish fed with diet without pH adjustment. [ABSTRACT FROM AUTHOR]

Nutrient digestibility, growth, and mucosal barrier status of fish skin, gills, and distal intestine were studied in Atlantic salmon fed feeds based on marine or plant-derived ingredients. The barrier status was assessed by considering the expression of four mucin genes, five genes that encode antimicrobial proteins, distal intestine micromorphology, and design-based stereology of the midgut epithelium. In addition, the head kidney leukocytes were examined using flow cytometry; to understand the differences in their counts and function. Five experimental feeds containing the main components i) fishmeal and fish oil (BG1), ii) soybean meal (BG2; to induce enteritis), iii) fishmeal as the main protein source and rapeseed oil as the main lipid source (BG3), iv) a mix of plant protein concentrates as the protein sources and fish oil as the lipid source (BG4), and v) plant and marine ingredients in the ratio 70:30 (BG5) were produced for the study. Atlantic salmon with initial weight 72.7 ± 1.2 g was offered the experimental feeds for 65 days. The results revealed that the weights of all fish groups doubled, except for fish fed BG2. Fish fed the BG2 diet had lower blood cholesterol concentration, developed enteritis, had lower expression of muc2 in the distal intestine, and had a compromised barrier status in the intestine. Expression of both the mucin genes and genes that encode antimicrobial peptides were tissue-specific and some were significantly affected by diet. The fish fed BG1 and BG3 had more head kidney lymphocyte-like cells compared to BG5-fed fish, and the phagocytic activity of macrophage-like cells from the head kidney was the highest in fish fed BG1. The intestinal micromorphology and the mucosal mapping suggest two different ways by which plant-based diets can alter the gut barrier status; by either reducing the mucous cell sizes, volumetric densities and barrier status (as noted for BG2) or increasing volumetric density of mucous cells (as observed for BG4 and BG5). The results of the compromised intestinal barrier in fish fed plant ingredients should be further confirmed through transcriptomic and immunohistochemical studies to refine ingredient composition for sustainable and acceptable healthy diets. [ABSTRACT FROM AUTHOR]

The use of low fishmeal/fish oil in marine fish diets affects dietary essential fatty acids (EFAs) composition and concentration and, subsequently, may produce a marginal deficiency of those fatty acids with a direct impact on the fish intestinal physiology. Supplementation of essential fatty acids is necessary to cover the requirements of the different EFAs, including the ones belonging to the n-6 series, such as arachidonic acid (ARA). ARA, besides its structural role in the configuration of the lipid classes of the intestine, plays an important role in the functionality of the gut-associated immune tissue (GALT). The present study aimed to test five levels of dietary ARA (ARA0.5 (0.5%), ARA1 (1%), ARA2 (2%), ARA4 (4%), and ARA6 (6%)) for European sea bass (Dicentrarchus labrax) juveniles in order to determine (a) its effect in selected distal intestine (DI) lipid classes composition and (b) how these changes affected gut bacterial translocation rates and selected GALT-related gene expression pre and post challenge. No differences were found between distal intestines of fish fed with the graded ARA levels in total neutral lipids and total polar lipids. However, DI of fish fed with the ARA6 diet presented a higher (P < 0.05) level of phosphatidylethanolamine (PE) and sphingomyelin (SM) than those DI of fish fed with the ARA0.5 diet. In general terms, fatty acid profiles of DI lipid classes mirrored those of the diet dietary. Nevertheless, selective retention of ARA could be observed in glycerophospholipids when dietary levels are low (diet ARA0.5), as reflected in the higher glycerophospholipids-ARA/dietary-ARA ratio for those animals. Increased ARA dietary supplementation was inversely correlated with eicosapentaenoic acid (EPA) content in lipid classes, when data from fish fed with the diets with the same basal composition (diets ARA1 to ARA6). ARA supplementation did not affect intestinal morphometry, goblet cell number, or fish survival, in terms of gut bacterial translocation, along the challenge test. However, after the experimental infection with Vibrio anguillarum, the relative expression of cox-2 and il-1β were upregulated (P < 0.05) in DI of fish fed with the diets ARA0.5 and ARA2 compared with fish fed with the rest of the experimental diets. Although dietary ARA did not affect fish survival, it altered the fatty acid composition of glycerophospholipids and the expression of pro-inflammatory genes after infection when included at the lowest concentration, which could be compromising the physical and the immune functionality of the DI, denoting the importance of ARA supplementation when low FO diets are used for marine fish. [ABSTRACT FROM AUTHOR]

The present study was conducted to investigate the effects of sodium butyrate (SB) on the physical barrier function, pro‐inflammatory response and possible underlying mechanisms in the distal intestine (DI) of yellow drum when fed a high‐SBM diet. Three iso‐proteic and iso‐lipidic diets were formulated with fish meal (FM, the control), 45% fish meal protein replaced by SBM (SBM) and 45% fish meal protein replaced by SBM but supplemented with 0.15% SB (SBM + SB). Fish were fed twice daily for 10 weeks. Results indicated that SB supplementation significantly increased the specific growth rate (SGR) and feed efficiency ratio (FER) and methionine content of muscle when compared with those of fish fed the SBM diet (p < .05). The morphologic histology results showed that SB dramatically improved the physical barrier structure, characterized as increases of fold height (FH) and muscular thickness (MT) (p < .05). RT‐qPCR data were accordant with morphologic histology results, in which claudin 3, claudin 4 and occludin were increased while claudin 7 and myosin light chain kinase (MLCK) mRNA expression levels were decreased (p < .05). Sodium butyrate also exerted anti‐inflammatory function, which may be attributed to the suppression of nucleus p65 protein expression. Results suggest SB can be incorporated in high‐SBM diets to ameliorate the negative consequences of alternative dietary ingredients on yellow drum physiology. [ABSTRACT FROM AUTHOR]

Two trials were conducted to evaluate the efficacy of commercial enzyme‐treated soy (ESBM) to replace the use of fish meal (FM) in practical diets for Florida pompano Trachinotus carolinus. The reference diet which has been run in numerous trials for Florida pompano was formulated using 150, 466 and 80 g/kg of FM, soybean meal and corn protein concentrate respectively. In trial 1, test diets were produced by replacing FM with 30.8, 61.4 and 92.1 g/kg of ESBM. In trial 2, test diets were produced by replacing FM with 28.9, 89.8, 120.1 g/kg of ESBM. Triplicate group of fish in trial 1 (mean weight = 13.05 ± 0.34 g) and trial 2 (mean weight = 18.45 ± 0.49 g) was fed these diets to apparent satiety for 8 weeks. Growth performance was affected as the dietary FM was replaced with ESBM. In trial 1, final weight (FW), percentage weight gain and thermal growth coefficient were lower in 6 g/kg of FM compared to 15 g/kg, while feed conversion ratio significantly higher in fish fed the lowest inclusion level of FM (6 g/kg). In trial 2, FW was significantly lower when FM completely replaced by ESBM and no significant differences in other growth parameters. In all trials, no significant differences were observed in terms of crude protein, moisture, fat, crude fibre, dry matter and ash content of the fish. No significant differences in serum levels of total protein, albumin, alkaline phosphatase, alanine transaminase, aspartate transaminase, glucose and bile acids were observed in either trial. However, in trial 1, serum cholesterol level was higher in fish fed 150 g/kg FM compared to other dietary treatments. The histomorphological structure of liver and distal intestine was slightly affected by lower inclusion level of FM. Overall, there was a decreasing trend in pompano growth performance as the inclusion of FM decreased. All parameters indicated that ESBM could be used to reduce the inclusion of FM from 150 to 90 g/kg. [ABSTRACT FROM AUTHOR]

The present study was designed to investigate the effects of diets containing advanced soy products (enzyme‐treated soy and fermented soy) or corn protein concentrate (CPC) in combination with porcine meal (PM) to completely replace poultry byproduct meal (PBM) on growth performance, body composition, and distal intestine histology of Florida pompano, Trachinotus carolinus. Four experimental diets were formulated to be isonitrogenous and isolipidic, to contain 400 g/kg crude protein and 80 g/kg lipid. A reference diet (PBM diet [PBMD]) contained 150 g/kg PBM and 495 g/kg soybean meal (SBM), and three test diets were formulated replacing PBM with 15 g/kg of CPC (CPC diet [CPCD]) or replacing all SBM and PBM with 535 g/kg fermented soy (fermented soybean meal diet [FSBMD]) or 451.3 g/kg enzyme‐treated soy (enzyme‐treated soybean meal diet [ESBMD]). All three test diets were supplemented with 38 g/kg of PM. Diets were fed based on a percentage of bodyweight adjusted after sampling the fish every 2 weeks to triplicate groups of Florida pompano juveniles (mean weight 8.06 ± 0.22 g). After 8 weeks of feeding, fish fed CPCD and ESBMD performed equally well in terms of final body weight, thermal growth coefficient, and percentage weight gain in comparison to fish fed PBMD. In all cases, feeding FSBMD resulted in poor feed conversion and lower feed intake compared to other treatments. Protein retention efficiency, whole‐body proximate composition, phosphorus, sulfur, potassium, magnesium, calcium, sodium, and zinc contents were not significantly influenced by the dietary treatments. The results obtained in the present histological study showed no significant differences in the thickness of serous layer, muscular layer, and submucosal layer of the intestine among treatments. Fish fed CPCD showed a significant widening of the lamina propria with an increase of cellular infiltration and higher presence of goblet cells compared to other dietary treatment. Based on these results, 451 g/kg ESBM or combination of 150 g/kg of CPC and 495 g/kg SBM supplemented with 38 g/kg PM can be utilized to develop a practical diet for juvenile Florida pompano without impacting growth, nutritive parameters, and several distal intestine health parameters. [ABSTRACT FROM AUTHOR]

Abstract Black soldier fly (Hermetia illucens) meal is a potential alternative to fishmeal and plant proteins in diets for farmed fish since it can be produced on organic waste substrates, requires little energy and water inputs and contains high levels of essential amino acids. Recent studies have partially replaced fishmeal with black soldier fly meal, however, research on their impact on gut microbiota of fish is limited. In a five week experiment, juvenile rainbow trout (Oncorhynchus mykiss) were fed either a reference diet based on fishmeal or three diets with 30% inclusion of black soldier fly meals in the form of pre-pupae, larvae or defatted-larvae. The combined luminal content and mucosa were collected from the distal intestine of three fish per tank with four tanks per diet (n = 12) and 16S rRNA gene amplicons were sequenced using the Illumina MiSeq platform. Feeding the insect-based diets increased the alpha-diversity of bacteria and abundance of lactic acid bacteria, which may be due to the addition of dietary chitin. Compared with fishmeal, feeding insects resulted in higher abundance of phyla Firmicutes and Actinobacteria with lower abundance of Proteobacteria. Fish fed the full-fat meals had higher abundance of Corynebacterium that was attributed to its ability to produce lipase and the high content of dietary lipids as a substrate. Bacillaceae was increased in fish fed both larvae diets and unchanged in the pre-pupae diet, which indicated that life-cycle stage of the insect influenced the gut microbiota. Based on these results, we found that feeding black soldier flies increased diversity and altered the composition of gut bacteria of rainbow trout, which were further influenced by life-cycle stage and lipid content of the insect meal. Highlights • Gut bacteria of rainbow trout fed BSF meals were identified using high-throughput sequencing for the first time • Feeding larvae, pre-pupae and defatted larval meals resulted in three different gut bacteria profiles in rainbow trout • Results indicating that BSF life stage and lipid content are decisive factors influencing gut microbiota in rainbow trout • All BSF diets increased bacterial diversity and lactic acid bacteria that may indicate improved gut health of rainbow trout [ABSTRACT FROM AUTHOR]

[Display omitted] • NSE1 (0.2%) and NSE2 (0.2%) increased il1β expression in distal intestine (DI). • NSE2 (0.02%) caused a down-regulation of immune biomarkers in DI. • NSEs did not adversely impact fish weight or DI morphometry and microbiota. Compounds from woody biomass are promising candidates as feed additives to improve fish health and welfare of Atlantic salmon (Salmo salar) during the productive cycleng. Thus, conidendrin- and isorhapontin-based extracts (NSEs) from Norway spruce (Picea abies) were evaluated at different levels in a four-week trial. A commercial-like diet (D1) was supplemented with 0.2% of a commercial β-glucan (D2) or with NSEs at 0.02%, 0.1% and 0.2% (D3-D8). No significant differences were found in growth, intestinal morphometry and microbiota at the genus level. Immune-related biomarkers in distal intestine from D5 and D6 indicated an activation of a pro-inflammatory response by the up-regulation of il1b , as in D2. Interestingly, isorhapontin-based extract at higher inclusion level (D8), showed a down-regulation of both pro- and anti-inflammatory- genes, suggesting maintenance of homeostasis. These results showed the importance of source and inclusion levels of bioactive compounds on the regulatory balance associated with fish immune response. [ABSTRACT FROM AUTHOR]

The effects of a dietary soy protein concentrate (SPC) as a fish meal (FM) substitute, on selected innate immune responses, the oxidative status, hepatic and intestinal morphology of gilthead sea bream, Sparus aurata, were evaluated after a three-month feeding trial. Isonitrogenous (45% crude protein) and isoenergetic (23 kJ/g gross energy) diets with 20% (SPC20), 40% (SPC40) and 60% (SPC60) of SPC inclusion, supplemented with methionine and phosphate, were evaluated against a diet containing FM as the sole protein source. Diets were allocated in triplicate groups of 26-g fish (8 kg m −3 /tank) and administered for three months. Immune responses were evaluated by performing immunological assays in blood (respiratory burst activity) and serum (myeloperoxidase content, bacteriolytic and lysozyme activity), as well as by gene expression analysis of immune-associated genes (MHCIIα, β2m, CSF-1R, NCCRP-1, TGF-β1, HSP70) in the head kidney and distal intestine. In addition, oxidative stress was evaluated by measuring the activity of liver enzymes associated with the antioxidant system. The respiratory burst activity of blood was significantly decreased in the SPC40 group, while serum myeloperoxidase content and bacteriolytic and lysozyme activities were affected. Significantly higher expression levels of NCCRP-1 and HSP70 were found in SPC60 head kidneys, while increased intestinal MHCIIα and NCCRP-1 transcripts were observed in SPC40. Hepatic antioxidant enzyme activity of glutathione reductase and glutathione-S-transferase was significantly enhanced in the SPC40 and SPC60 groups, while superoxide dismutase activity was increased only in the SPC40 group. Moreover, increased lipid accumulation in the enterocytes of the distal intestine was observed in the SPC60 group. Overall, a three-month feeding period with diets over 40% of dietary SPC inclusion as a FM substitute, indicated increases on immune and antioxidant enzyme responses, suggesting the dietary SPC levels that gilthead sea bream can tolerate. [ABSTRACT FROM AUTHOR]

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Legumes such as soybean, peas and lupin have attracted considerable interest as potential sources of protein to replace finite and limiting supplies of marine fishmeal (FM) as major ingredients for aquafeeds. In this respect, faba beans ( Vicia faba ) represent a widespread and relatively unexploited legume crop in Europe with potentially favourable characteristics. However, for carnivorous species such as Atlantic salmon ( Salmo salar ), protein levels in legumes are generally too low and require to be concentrated to be direct replacements for FM. Previously we showed that a faba bean protein concentrate, produced by air classification, containing 55% protein could partially replace FM and/or soy protein concentrate (SPC) in feeds for parr and post-smolt salmon. In the present study, a faba bean protein isolate (BPI), produced by a wet process, with almost ~ 80% crude protein was investigated in feeds for Atlantic salmon in seawater. Four dietary treatments were tested including one with high inclusion of FM (400 g kg − 1 ) and three with low FM (216 g kg − 1 ) and increasing inclusions of BPI (0, 70 and 140 g kg − 1 ) substituting for SPC (236, 125 and 45 g kg − 1 ). Growth performance in fish was unaffected with the lower level of dietary BPI, but was reduced in fish fed the higher level, mainly due to feed intake being reduced initially. Histological analysis of the distal intestine showed inflammation in fish fed both diets containing BPI, but especially at 140 g kg − 1 . The high dietary level of BPI affected the transcriptome of pyloric caeca with almost 2000 differentially expressed genes (DEG) compared to fish fed FM, whereas fish fed SPC or the lower level of BPI showed no DEG compared to fish fed FM. In contrast, the liver transcriptome was generally affected similarly by both BPI and SPC. The combined data suggested that the BPI utilised contained a factor that was detrimental above a certain threshold and, although this factor could be an artefact of the protein isolation method, an effect of a known ANF could not be excluded with saponin the most likely candidate. Overall, however, the results of the present study confirmed that protein concentrates or isolates derived from faba beans can replace FM and/or SPC up to a certain level in feeds for Atlantic salmon. Statement of relevance A study testing novel raw materials for fish feed. [ABSTRACT FROM AUTHOR]

The inclusion of plant meals in diets of farmed Atlantic salmon can elicit inflammatory responses in the distal intestine (DI). For the present work, fish were fed a standard fish meal (FM) diet or a diet with partial replacement of FM with solvent-extracted camelina meal (CM) (8, 16, or 24 % CM inclusion) during a 16-week feeding trial. A significant decrease in growth performance was seen in fish fed all CM inclusion diets (Hixson et al. in Aquacult Nutr 22:615-630, ). A 4x44K oligonucleotide microarray experiment was carried out and significance analysis of microarrays (SAM) and rank products (RP) methods were used to identify differentially expressed genes between the DIs of fish fed the 24 % CM diet and those fed the FM diet. Twelve features representing six known transcripts and two unknowns were identified as CM responsive by both SAM and RP. The six known transcripts (including thioredoxin and ependymin), in addition to tgfb, mmp13, and GILT, were studied using qPCR with RNA templates from all four experimental diet groups. All six microarray-identified genes were confirmed to be CM responsive, as was tgfb and mmp13. Histopathological analyses identified signs of inflammation in the DI of salmon fed CM-containing diets, including lamina propria and sub-epithelial mucosa thickening, infiltration of eosinophilic granule cells, increased goblet cells and decreased enterocyte vacuolization. All of these were significantly altered in 24 % CM compared to all other diets, with the latter two also altered in 16 % CM compared with 8 % CM and control diet groups. Significant correlation was seen between histological parameters as well as between five of the qPCR analyzed genes and histological parameters. These molecular biomarkers of inflammation arising from long-term dietary CM exposure will be useful in the development of CM-containing diets that do not have deleterious effects on salmon growth or physiology. [ABSTRACT FROM AUTHOR]

Abstract: In the present study full-length cDNAs corresponding to three isoforms of intestinal fatty acid binding protein (fabp2) in Atlantic salmon were cloned and characterized. Gene expression of fabp2 was observed in all tissues investigated, although differences were observed between isoforms. The highest fabp2a1, fabp2a2, and fabp2b expression was in the intestine. A 15kDa protein, corresponding to putative Fabp2 protein, was identified by immunoblotting using anti-human Fabp2 antibody. Immunoblotting and immunohistochemistry confirmed that Fabp2 protein was present in most Atlantic salmon tissues. Similar to gene expression, intestinal tissues had the highest Fabp2 protein levels, decreasing gradually from proximal to distal intestine. During development of distal intestinal inflammation caused by dietary soybean meal from 0 to 21days, Fabp2 decreased significantly on both transcriptional and protein levels. The reduction in Fabp2 was preceded by a down regulation of peroxisome proliferator activated receptor (ppar) alpha and gamma, fabp2''s presumed regulatory proteins, and followed by a progressive increase in proliferating cell nuclear antigen (Pcna) staining. Results illustrate that the early decline of distal intestinal fabp2 was likely caused by a down regulation of their regulatory proteins, but at later time points reduced Fabp2 may largely be due to a less mature enterocyte population resulting from rapid cell turnover. [Copyright &y& Elsevier]

To investigate the influence of dietary soy protein size on the bile acid status and the distal intestinal morphology in rainbow trout Oncorhynchus mykiss, diets based on soybean meal (SBM), soy protein isolate (SPI) and 4 soy peptide products having different molecular sizes were fed to trout (initial BW, 19 g) for 10 weeks. A diet based on fish meal (Cont) and a diet including the smallest-peptide and low-saponin product (Hi-Nute AM) and supplemented with soya saponin (AMS) were also fed. In fish fed diets SBM and SPI, the gallbladder was atrophied, the proportion of biliary cholyltaurine decreased, and highly vacuolated epithelial cells of mucosal folds and proliferation of connective tissues in the submucosa of the distal intestine were observed. These parameters tended to improve in fish fed soy peptide diets and especially those of fish fed diet AM were similar to fish fed diet Cont. Although the gallbladder of fish fed diet AMS was smaller than fish fed the unsupplemented diet AM, no morphological abnormalities were observed in the distal intestine. These results suggest that soy proteins/peptides with relatively large sizes and with soya saponin affect the bile acid status and distal intestinal morphology of rainbow trout. [ABSTRACT FROM AUTHOR]

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

The objective of the current study was to examine the effects of yeasts on intestinal health and transcriptomic profiles from the distal intestine and spleen tissue of Atlantic salmon fed SBM-based diets in seawater. Cyberlindnera jadinii (CJ) and Wickerhamomyces anomalus (WA) yeasts were heat-inactivated with spray-drying (ICJ and IWA) or autolyzed at 50 °C for 16 h (ACJ and AWA), followed by spray-drying. Six diets were formulated, one based on fishmeal (FM), a challenging diet with 30% soybean meal (SBM) and four other diets containing 30% SBM and 10% of each of the four yeast fractions (i.e., ICJ, ACJ, IWA and AWA). The inclusion of CJ yeasts reduced the loss of enterocyte supranuclear vacuolization and reduced the population of CD8α labeled cells present in the lamina propria of fish fed the SBM diet. The CJ yeasts controlled the inflammatory responses of fish fed SBM through up-regulation of pathways related to wound healing and taurine metabolism. The WA yeasts dampened the inflammatory profile of fish fed SBM through down-regulation of pathways related to toll-like receptor signaling, C-lectin receptor, cytokine receptor and signal transduction. This study suggests that the yeast species, Cyberlindnera jadinii and Wickerhamomyces anomalus are novel high-quality protein sources with health-beneficial effects in terms of reducing inflammation associated with feeding plant-based diets to Atlantic salmon. [ABSTRACT FROM AUTHOR]

In the current experiment, RNA was isolated from the distal intestine (DI) of Atlantic salmon-fed fishmeal-based diets containing either genetically modified (GM) maize (Bt maize, Mon810®, Monsanto Company, St. Louis, Missouri, USA) or its conventional near-isogenic parental line (non-GM) for 82 days, both at 300 g kg−1 inclusion. From a suppression subtractive hybridization (SSH) cDNA library, 192 clones with similarity to both known and novel Atlantic salmon sequences were identified. Real-time PCR was used to study the differential expression of 10 clones between the dietary groups. Expression of a clone showing high protein similarity to proton-dependent high-affinity oligopeptide transporter was significantly upregulated in fish-fed GM maize compared with fish-fed non-GM maize. No significant differences in expression were observed for the nine other clones showing similarity to the following proteins: heat shock protein 90B, procathepsin B, interferon gamma-inducible protein 30, ferritin heavy subunit, serum lectin isoform/C-type mannose-binding lectin, fatty acid-binding protein/gastrotropin, ATP synthase [H+ transporting, mitochondrial F0 complex, subunit c (ATPSYNT)], sonic hedgehog and translationally controlled tumour protein. In conclusion, only minor differences in DI transcriptional gene expression was observed between fish fed the GM and non-GM maize diets. [ABSTRACT FROM AUTHOR]

Soybean meal-induced enteritis was characterized by the disappearance of the supranuclear vacuoles (SNV) in the enterocytes of the distal intestine of Atlantic salmon Salmo salar. The loss of SNV was correlated with an endocytosis uptake block as shown with ferritin as a marker molecule. [ABSTRACT FROM AUTHOR]

Abstract: The development of soybean meal (SBM) induced enteritis in the hindgut of the omnivorous common carp (Cyprinus carpio L.). The developed condition was assessed when carp, continuously fed on animal protein, were transferred to a diet in which 20% of the protein was replaced by SBM. After week 1, most of the inflammation parameters were already present, but at week 3, a strong aggravation of the condition was observed which included a shortening of the mucosal folds, the disappearance of the supranuclear vacuoles, an increased number of goblet cells, a thickened lamina propria and sub-epithelial mucosa with increased numbers of basophilic granulocytes as well as a decreased uptake capacity of enterocytes (impaired endocytosis and microvilli). Contrary to previous observations made with respect to Atlantic salmon, common carp start to recover from the fourth to the fifth week after switching to SBM feeding. At this stage, the supranuclear vacuoles refill and most of the parameters revert to basal levels. During the enteritis process, a real-time quantitative PCR analysis was conducted to measure the expression of inflammatory and anti-inflammatory cytokine genes in the isolated intraepithelial lymphocytes (IEL). The pro-inflammatory interleukin 1β (IL-1β) and tumour necrosis factor α1 (TNF-α1) genes were up-regulated during the inflammation process while the anti-inflammatory interleukin 10 (IL-10) was down-regulated after an initial up-regulation at week 1. Transforming growth factor β (TGF-β) expression showed an up-regulation from week 3 onwards despite the high Ct value and the low primer efficiency shown. This study confirms the contribution of IEL (mainly T-like cells) and basophils in the enteritis process. In addition, the results show a clear involvement of up- and down-regulated cytokine genes in both the onset and recovery of the SBM-induced enteritis in the hindgut of carp. [Copyright &y& Elsevier]

This study evaluates the effect of temperature on the development of intestinal disorders when Atlantic salmon are fed soybean meal (SBM). In this study 20% of the dietary fishmeal was replaced by solvent-extracted Hipro SBM. Atlantic salmon reared at two different water temperatures (8 °C and 12 °C), were fed a control diet and an experimental diet for 20 days. Samples were taken at days 7 and 20. The extent of the morphological changes was assessed using a semi-quantitative scoring system developed for this purpose. The study demonstrates that enteritis is affected by temperature. The intestinal disorders were more severe in fish reared at 12 °C compared with those reared at 8 °C. It can be concluded from this study that temperature changes the speed but not the type of SBM-induced enteritis expressed as a delay on the response when Atlantic salmon are kept at lower temperatures. [ABSTRACT FROM AUTHOR]

Limited availability of fishmeal leads to exploration of alternative protein sources like soybean meal (SBM). During the last decade, genetically modified (GM) plants have been introduced to the production of soybean crops. In the current experiment RNA was isolated from the distal intestinal section of Atlantic salmon fed either GM SBM or its near-isogenic parental line (non-GM), both at 30% inclusion. From a suppression subtractive hybridization cDNA library, 95 clones were sequenced. Clones with similarity to both known Atlantic salmon genes and novel Atlantic salmon sequences were identified. Real-time polymerase chain reaction was used to study differential expression of seven clones between the dietary groups. The clones were selected based on their relevance to intestinal immune responses and nutrient metabolism. Expression of a serum lectin-like clone was down-regulated in the GM group compared with the non-GM group. No differential expression was observed for six other clones with similarity to actin-related protein 2/3 complex-subunit 3, cysteine-rich intestinal protein, fatty acid binding protein/gastrotropin, ferritin heavy subunit, anterior gradient protein and peptide transporter. In conclusion, only minor differences in distal intestine transcriptional gene expression were observed between fish fed the diets with the non-GM and GM varieties. [ABSTRACT FROM AUTHOR]

Juvenile cobias, Rachycentron canadum, were fed extruded diets containing toasted defatted soybean meal (SBM) or untoasted defatted SBM [white flakes (WF)] to study growth and feed conversion, and to study if SBM induces morphological changes in the gastrointestinal (GI) tract. Three diets were produced: a fish meal-based control diet (FM diet) with 558 g FM kg−1, and two diets with 335 g FM and either 285 g SBM kg−1 (SBM diet) or 285 g WF kg−1 (WF diet). The diets were extruded at approximately 120°C with 280 g kg−1 moisture. Triplicate groups of cobias (mean weight: 25.9 g) were fed the diets during 6 weeks. Feed intake of the FM and SBM diets were not significantly different, whereas the cumulative feed intake of cobias fed the WF diet was lower ( P < 0.05) than that of cobias fed the FM and SBM diets after the first 21-day period. Specific growth rate and feed conversion ratio were not significantly different between cobias fed the FM and SBM diets, but significantly poorer results were obtained in cobias fed the WF diet. No morphological differences in the GI tract could be attributed to the diets, and cobias fed soy did not develop enteritis in the distal intestine. [ABSTRACT FROM AUTHOR]

Abstract: An experiment was carried out to study the nutritional value of solvent extracted, toasted soybean meal (SBM) and solvent extracted, untoasted soy “white flakes” (WF) partly replacing high-quality fish meal (FM) in extruded diets for rainbow trout. Particularly, we wanted to find out if feed extrusion provides sufficient heat to reduce the soybean trypsin inhibitor activity (TIA) to a tolerable level in diets for trout. Three diets were produced: a control diet with 490g FM kg−1 (FM diet), a diet with 290g FM and 250g SBM kg−1 (SBM diet), and a diet with 290g FM and 250g WF kg−1 (WF diet). Each diet was fed to three groups of trout for 63 days. The TIA levels in the SBM and WF diets after extrusion were 0.6 and 2.1mg (g dry matter)−1, respectively. Feed intake was lower (P <0.05) in trout fed the SBM and WF diets than in those fed the FM diet, resulting in reduced growth and poorer feed conversion. The diets did not significantly affect whole-body content of dry matter, protein and fat, or carcass yield, total gut weight, or weight of pyloric, mid and distal intestine. Trout fed the WF diet had higher stomach weight than trout fed the FM diet. Liver weight, plasma cholesterol and triacylglycerol were lower in trout fed the SBM and WF diets than in those fed the FM diet. Apparent digestibility of nitrogen was lower for the WF diet than for the FM diet and intermediate for the SBM diet. The SBM and WF diets caused lower digestibility of fat and most amino acids and lower nitrogen retention than the FM diet. Moderate morphological abnormalities were found in the distal intestine of trout fed the SBM and WF diets. Bile acid concentration in chyme was lower in fish fed the SBM and WF diets than in fish fed the FM diet, except for the proximal pyloric region and the posterior distal intestine. Trypsin activity in chyme of the distal intestine was higher and leucine amino peptidase activity in intestinal wall tissue was lower in trout fed the SBM and WF diets than in trout fed the FM diet. In conclusion, both SBM and WF had a negative influence on growth and feed conversion compared with the FM diet. Extrusion did not influence soy-related challenges such as reduced fat digestibility, and morphological and enzymatic changes. However, extrusion was sufficient to lower TIA in the diets to an acceptable level for rainbow trout. [Copyright &y& Elsevier]

Brush border membrane vesicles (BBMV) enriched in sucrase, maltase and alkaline phosphatase, and impoverished in Na+-K+-ATPase, were isolated from proximal and distal intestine of the gilthead sea bream (Sparus aurata) by a MgCl2 precipitation method. Vesicles were suitable for the study of the characteristics ofD-glucose apical transport. Only oneD-glucose carrier was found in vesicles from each intestinal segment. In both cases, theD-glucose transport system was sodium-dependent, phlorizin-sensitive, significantly inhibited byD-glucose,D-galactose, a-methyl-D-glucose, 3-O-methyl-D-glucose and 2-deoxy-D-glucose, and showed stereospecificity. Apparent affinity constants ofD-glucose transport (Kt) were 0.24 ± 0.03 mM in proximal and 0.18 ± 0.03 mM in distal intestine. Maximal rate of influx (Jmax) was 47.3 ± 2.2 pmols. mg-1 protein for proximal and 27.3 ± 3.6 pmols. mg-1 protein for distal intestine. Specific phlorizin binding and relative abundance of an anti-SGLT1 reactive protein were significantly higher in proximal than in distal BBMV. These results suggest the presence of the sameD-glucose transporter along the intestine, with a higher density in the proximal portion. This transporter is compatible with the sodium-dependentD-glucose carrier described for other fish and with the SGLT1 of higher vertebrates. [ABSTRACT FROM AUTHOR]

Duplicate tanks of c.280 g Atlantic salmon ( Salmo salar L.) were fed for 60 days on diets in which fishmeal was substituted with graded levels of extracted soybean meal (SBM) comprising 0%, 10%, 15%, 20%, 25% or 35% of total protein. The effects on feed intake, growth, feed conversion, apparent digestibility and utilization of macronutrients and energy, pathohistological response of the distal intestine (DI), activities of digestive enzymes in the mid and distal intestinal mucosa, and faecal trypsin and plasma insulin concentrations were studied. A negative, dose-dependent effect of SBM was observed on nearly all performance parameters with a notable exception of feed intake. The lowest SBM inclusion level of 10% resulted in moderate pathohistological changes in the DI. Each subsequent increase in SBM level increased the number of fish displaying severe changes. In contrast to the mid-intestine (MI), all enzyme activities in the distal intestinal mucosa decreased dose-dependently with increasing SBM inclusion. Faecal trypsin increased up to an SBM inclusion level of 20% and then levelled off. Plasma insulin increased from 0% to 15% SBM inclusion and then decreased. The results suggest that caution should be exercised in the use of even low levels of extracted SBM in salmon feeds. [ABSTRACT FROM AUTHOR]

Two trials were initiated to investigate the consequences of including various soybean products in diets for Atlantic salmon Salmo salar L. on (1) mortality following infection by Aeromonas salmonicida ssp. salmonicida during a cohabitation challenge, and (2) the lysozyme and IgM content of the intestinal mucosa. Groups of salmon were fed control diets containing fishmeal as the sole protein source (Contr1 and Contr2, respectively), soy concentrate-containing diets (SoyConc1 and SoyConc2, respectively), or diets containing either solvent-extracted soybean meal (SoyMeal, trial 1) or soybean molasses (SoyMol, trial 2), an alcohol extract of soybean meal. Both SoyMeal and SoyMol caused enteritis-like changes in the distal intestine, which were not observed in fish fed the Contr1, Contr2, SoyConc1, or SoyConc2 diets. There were significant differences (P < 0.05) in mortality between feeding groups following the A.s. salmonicida challenge: these differences were greatest in fish fed SoyMeal (65.6%), least in fish fed SoyConc1 (60.5%), and intermediate in the fish fed the Contr1 diet (62.9%). The SoyMol diet caused significantly (P < 0.0001) increased levels of both lysozyme and IgM in the mid and distal intestinal mucosa. It is concluded that components of soybean meal and soybean molasses cause an inflammatory response in the distal intestine that may lead to increased susceptibility to furunculosis. [ABSTRACT FROM AUTHOR]

Ensuring salmon health and welfare is crucial to maximize production in recirculation aquaculture systems. Healthy and robust mucosal surfaces of the skin and intestine are essential to achieve this goal because they are the first immunological defenses and are constantly exposed to multistressor conditions, such as infectious diseases, suboptimal nutrition, and environmental and handling stress. In this work, Atlantic salmon, split from a single cohort, were subjected to acute hypoxia stress or 15-min crowding stress and observed over a 24-h recovery period. Samples were collected from fish at 0, 1, 3, 6, 12 and 24 h post-stress to analyze plasma-circulating markers of endocrine function (cortisol), oxidative stress (glutathione peroxidase) and immune function (interleukin 10 (IL-10), annexin A1). In addition, mucosal barrier function parameters were measured in the skin mucus (Muc-like protein and lysozyme) and distal intestine (simple folds, goblet cell size and goblet cell area). The results showed that both acute stress models induced increases of circulating cortisol in plasma (1 h post-stress), which then returned to baseline values (initial control) at 24 h post-stress. Moreover, the hypoxia stress was mostly related to increased oxidative stress and IL-10 production, whereas the crowding stress was associated with a higher production of Muc-like protein and lysozyme in the skin mucus. Interestingly, in the distal intestine, smaller goblet cells were detected immediately and one hour after post-hypoxia stress, which could be related to rapid release of the cellular content to protect this organ. Finally, the correlation of different markers in the hypoxic stress model showed that the circulating levels of cortisol and IL-10 were directly proportional, while the availability of Muc-like proteins was inversely proportional to the size of the goblet cells. On the other hand, in the crowding stress model, a proportional relationship was established between plasma cortisol levels and skin mucus lysozyme. Our results suggest key differences in energy partitioning between the two acute stress models and support the need for further investigation into the interplay of multistressor conditions and strategies to modulate immunological aspects of mucosal surfaces. [ABSTRACT FROM AUTHOR]

This study investigated the effects of dietary terrestrial animal and plant proteins on the intestinal transcriptomes of yellowtail kingfish (YTK), Seriola lalandi, an ecologically and economically important marine species in Australia. Five diets containing fish meal (FM), poultry by-product meal (PBM), blood meal (BLM), faba bean meal (FBM) and corn gluten meal (CGM) were formulated and fed over a period of 4 weeks. The Illumina RNA-sequencing (RNA-Seq) results identified a suite of differentially expressed genes involved in nutrient metabolism and protein digestion pathways, reinforced by quantitative polymerase chain reaction (qPCR) results. These findings provide molecular support to the notion that PBM and FBM are useful raw materials in commercial diets for YTK. Using the same evidence, we have demonstrated that BLM and CGM may be less useful and their incorporation into commercial aquafeeds for this species should be done cautiously. The differentially expressed genes showed a subtle difference and high correlation with apparent nutrient digestibility of raw materials. Further, our results indicate that transcriptome profiling provides a useful tool to evaluate alternative protein sources for use in aquaculture feeds. [ABSTRACT FROM AUTHOR]