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This study aimed at assessing the effect of short-chain fructooligosaccharides (scFOS), xylooligosaccharides (XOS), and galactooligosaccharides (GOS) on European sea bass juveniles gut microbiota. Four practical diets were formulated with fish meal (FM) and plant feedstuffs (PF) as protein sources (circa 30:70 of protein from FM:PF) and to include 1% of α-cellulose (control diet, CTR), or 1% of scFOS, XOS, or GOS (diets FOS, XOS, and GOS, respectively). Triplicate groups of fish with 79 g were fed with the experimental diets during 30 days. Gut content was sampled at days 7 and 30 for allochthonous microbiota characterization. Lactobacillus, Pseudomonas, Vibrio, and Burkholderia were the main genera found in fish gut. Gut allochthonous microbiota presented an increased number of operational taxonomic units (OTUs) and a higher Margalef index of bacterial richness in fish fed scFOS and XOS. Gut allochthonous microbial OTUs, Margalef species richness index, Shannon's diversity index, and SIMPER similarity were unaffected by sampling day. In conclusion, scFOS and XOS modulated European sea bass gut microbial community and this effect persisted throughout time. These changes in gut microbiota composition contribute to explain the positive effects on growth performance, immune status, and lipid and glucose metabolism previously reported in European sea bass fed with scFOS and XOS. [ABSTRACT FROM AUTHOR]

Recreational shore angling in the Atlantic Ocean between Moledo and Aveiro (Portugal) was examined using roving creel surveys (March/September 2001). Cooperation was high (90% of 2310 anglers approached). At least 39 species of fish were caught at a rate of approximately 0.5 fish angler h−1. An estimated 7319 kg of Dicentrarchus labrax (L.), with 45.6% below the minimum legal size, and 2040 kg of sea breams (genus Diplodus), correspond to 5.75% and 1.19% of the commercial landings in the same geographical area, respectively. The results shed light on a number of issues relevant to integrated coastal management, including temporal and spatial distribution of fishing effort, species caught, sizes of fish, catch rates, and factors influencing catches and angler satisfaction. Whilst the results suggest that the catches of sea breams and sea bass by day-time recreational shore angling in northern Portugal are small compared with commercial fishing, other recreational activities, such as boat fishing and spear-fishing, must be assessed. [ABSTRACT FROM AUTHOR]

In jawed vertebrates, adaptive immune responses are enabled by T cells. Two lineages were characterized based on their T cell receptor (TcR) heterodimers, namely αβ or γδ peptide chains, which display an Ig domain-type sequence that is somatically rearranged. γδ T cells have been less extensively characterized than αβ and teleost fish, in particular, suffer from a severe scarcity of data. In this paper, we worked on the well-known model, the European sea bass Dicentrarchus labrax, to broaden the understanding of teleost γδ-T cells. The T cell receptor chain (TR) γ transcript was expressed at a later developmental stage than TRβ, suggesting a layered appearance of fish immune cells, and the thymus displayed statistically-significant higher mRNA levels than any other organ or lymphoid tissue investigated. The polyclonal antibody developed against the TRγ allowed the localization of TRγ-expressing cells in lymphoid organs along the ontogeny. Cell positivity was investigated through flow cytometry and the highest percentage was found in peripheral blood leukocytes, followed by thymus, gut, gills, spleen and head kidney. Numerous TRγ-expressing cells were localized in the gut mucosa, and the immunogold labelling revealed ultrastructural features that are typical of T cells. At last, microalgae-based diet formulations significantly modulated the abundance of TRγ+ cells in the posterior intestine, hinting at a putative involvement in nutritional immunity. From a comparative immunological perspective, our results contribute to the comprehension of the diversity and functionalities of γδ T cells during the development of a commercially relevant marine teleost model. [ABSTRACT FROM AUTHOR]

(1) Background: This study aimed to evaluate the potential of short-chain fatty acids as functional ingredients to improve the immune status and disease resistance of European seabass (Dicentrarchus labrax) juveniles. (2) Methods: For that purpose, triplicate groups of fish with an initial body weight of 15.2 ± 0.03 g were fed isoproteic (43% crude protein) and isolipidic (18% crude lipids) diets supplemented with sodium acetate (SA), sodium propionate (SP), and sodium butyrate (SB) at two inclusion levels: 0.25% and 0.50%. An unsupplemented diet was used as a control. After 56 days of feeding with the experimental diets, fish were intraperitoneally (i.p.) injected with 100 µL of Vibrio anguillarum (1.2 × 107 Colony Forming Units (CFU)/mL) and mortality was recorded for 3 weeks. At the end of the trial, there were no differences in survival between the treatment groups and the control, but survival was higher in fish fed the diet supplemented with SB 0.50 than SP 0.25 (93.3 vs. 66.7%). Compared to the pre-challenge values, and regardless of diet composition, all hematological parameters (hemoglobin, hematocrit, red blood cells, white blood cells) measured decreased after 4 h of bacterial challenge, except for neutrophils which were increased. Independently of diet composition, lysozyme and nitric oxide decreased at 4 and 24 h post infection. Compared to the control, diets supplemented with SA and SP promoted an up-regulation of both pro- and anti-inflammatory cytokines at 4 h after the challenge, while the diets supplemented with SB promoted an up-regulation of pro- and anti-inflammatory cytokines at 24 h after the challenge. (3) Conclusions: Overall, present results suggest that SA and SP provide a fast response to a bacterial challenge in European sea bass juveniles, while SB provides increased survival. [ABSTRACT FROM AUTHOR]

Simple Summary: After a decade of research about the use of insects as fish feed, this paper reports the results of a large-scale trial on European sea bass (Dicentrarchus labrax) farmed under commercial conditions. Fish were fed an experimental diet containing 10% Hermetia illucens larva meal, 30% poultry by-product meal, and <5.5 g/100 g of feed of marine proteins. The results highlight that fish growth performances and the flesh quality of sea bass fed the experimental diet were similar to those of fish fed a commercial diet containing fish meal and fish oil. This study suggests that a diet rich in plant proteins, in which H. illucens and poultry by-products are also included, may be a viable alternative to existing aquafeeds for marine species. Protein meals from insects in combination with poultry by-product meal appear to be promising ingredients for replacing conventional proteins in the diets of carnivorous fish. The present study explored the effects on growth performance, hepatic enzymatic activity, and fillet physical and nutritional characteristics during a 66-day feeding trial performed on European seabass. A total of 3000 fish were distributed into three tanks, where the control group was fed with a commercial diet (CG) and a second group was fed in duplicate with the experimental diet (SSH) containing 10% Hermetia illucens larva meal, 30% poultry by-product meal, and <5.5 g/100 g of feed of marine origin proteins. All fish showed good growth performance. Glucose-6-phosphate dehydrogenase, aspartate aminotransferase, and 3-hydroxyacyl-CoA dehydrogenase activities were higher in the SSH group than in the CG group. The fillet fatty acid profile was largely unaffected by diet, except for a few fatty acids. Fish fed the SSH diet had a lower C22:1n-11 content than CG, thus suggesting an increased β-oxidation. The oxidative status of muscle lipids was not affected by the diet. In conclusion, the present study showed that European seabass can be successfully fed the SSH diet for two months in a commercial setting. [ABSTRACT FROM AUTHOR]

Simple Summary: SCFAs are considered functional ingredients as they promote the growth and health of fish. This work aimed to assess the effect of short-chain fatty acids (SCFAs) on the immune status of the European sea bass gut through the ex vivo use of intestinal explants. The ex vivo technique significantly reduces the number of animals to be used, according to the guidelines of the 3Rs. The present results are important to understand how European sea bass respond to a bacterial infection after the administration of SCFAs and for the evaluation of functional ingredients used in aquaculture. This study aimed to evaluate the intestinal interactions between three short-chain fatty acids (SCFA), namely, acetate, propionate, and butyrate, and pathogenic bacteria (Vibrio anguillarum) in intestinal explants of European sea bass (Dicentrarchus labrax) juveniles. The anterior intestine of 12 fish with an average weight of 100 g (killed by excess anesthesia with 2-phenoxyethanol) were sampled and placed in 24-well plates. The experimental treatments consisted of a control medium and a control plus 1 mM or 10 mM of sodium acetate (SA), sodium butyrate (SB), and sodium propionate (SP). After 2 h of incubation, the explants were challenged with Vibrio anguillarum at 1 × 107 CFU/mL for 2 h. After the bacterial challenge, and regardless of the SCFA treatment, the oxidative stress-related genus catalase (cat) and superoxide dismutase (sod) were down-regulated and glutathione peroxidase (gpx) was up-regulated. Furthermore, the immune-related genes, i.e., the tumor necrosis factor (TNF-α), interleukin 8 (IL-8), transforming growth factor (TGF-β), and nuclear factor (NF-Kβ) were also up-regulated, and interleukin 10 (IL-10) was down-regulated. During the pre-challenge, sodium propionate and sodium butyrate seemed to bind the G-protein coupled receptor (grp40L), increasing its expression. During the challenge, citrate synthase (cs) was down-regulated, indicating that the SCFAs were used as an energy source to increase the immune and oxidative responses. Overall, our results suggest that sodium propionate and sodium butyrate may boost European sea bass immune response at the intestine level. [ABSTRACT FROM AUTHOR]

Immune nutrition is currently used to enhance fish health by incorporating functional ingredients into aquafeeds. This study aimed to investigate the connections between tryptophan nutrition and the network that regulates the communication pathways between neuroendocrine and immune systems in European seabass (Dicentrarchus labrax). When tryptophan was supplemented in the diet of unstressed fish, it induced changes in the hypothalamic-pituitary-interrenal axis response to stress. Tryptophan-mediated effects were observed in the expression of anti-inflammatory cytokines and glucocorticoid receptors. Tryptophan supplementation decreased pro-opiomelanocortin b-like levels, that are related with adrenocorticotropic hormone and cortisol secretion. When stressed fish fed a tryptophan-supplemented diet were subjected to an inflammatory stimulus, plasma cortisol levels decreased and the expression of genes involved in the neuroendocrine response was altered. Modulatory effects of tryptophan dietary intervention on molecular patterns seem to be mediated by altered patterns in serotonergic activity. [ABSTRACT FROM AUTHOR]

Simple Summary: The production of halophyte plants, like Salicornia ramosissima, is increasing as they are highly valued for human consumption and due to their ability to grow in unutilized cultivation areas, like saline soils. However, only the green tips are commercialized, while the remaining plant is considered a residue. This study aimed to explore the potential of these salicornia by-products to be included in aquafeeds for juvenile European seabass, partially replacing wheat meal. The results obtained indicate that this substitution is possible with no apparent adverse effects on the fish and on the economic viability of the feeds. Additionally, the inclusion of salicornia in the diets was related to the decrease in compounds in fish muscle usually used as stress biomarkers and with the increase in DHA levels, one of the most relevant Omega-3 fatty acids for human nutrition. Therefore, data from this study suggest that salicornia by-products are a viable alternative to partially replace wheat meal in diets for juvenile European seabass, allowing salicornia farmers to valorize a residue and to implement the principles of circular economy in halophyte farming and the aquaculture industry. The green tips of Salicornia ramosissima are used for human consumption, while, in a production scenario, the rest of the plant is considered a residue. This study evaluated the potential of incorporating salicornia by-products in diets for juvenile European seabass, partially replacing wheat meal, aspiring to contribute to their valorization. A standard diet and three experimental diets including salicornia in 2.5%, 5% and 10% inclusion levels were tested in triplicate. After 62 days of feeding, no significant differences between treatments were observed in fish growth performances, feeding efficiency and economic conversation ratio. Nutrient digestibility of the experimental diets was unaffected by the inclusion of salicornia when compared to a standard diet. Additionally, salicornia had significant modulatory effects on the fish muscle biochemical profiles, namely by significantly decreasing lactic acid and increasing succinic acid levels, which can potentially signal health-promoting effects for the fish. Increases in DHA levels in fish fed a diet containing 10% salicornia were also shown. Therefore, the results suggest that salicornia by-products are a viable alternative to partially replace wheat meal in diets for juvenile European seabass, contributing to the valorization of a residue and the implementation of a circular economy paradigm in halophyte farming and aquaculture. [ABSTRACT FROM AUTHOR]

Simple Summary: The effects of increasing temperature and dietary lipid level on the body composition, growth performance, and freshness profile of the European seabass (Dicentrarchus labrax) were evaluated through a fish trial lasting 56 days. Findings demonstrated that fish reared at 24 °C presented a lower lipid level and a higher daily growth index than those reared at 20 °C. On the other hand, the sea bass condition index did not change among treatments. Additionally, sensory analysis (the Quality Index Method) and microbiological analysis revealed that fish reared at 24 °C showed better freshness conditions than those at 20 °C. Nevertheless, the dietary lipid level did not have any influence on fish freshness conditions. Therefore, our data suggest that the increase in temperature to 24 °C is beneficial for the growth and freshness profile of this particular species in aquaculture. A fish trial was carried out to evaluate the combined effects of temperature and dietary lipid level on the body composition, growth performance, and freshness profile of the European seabass (Dicentrarchus labrax). Fish were kept for 56 days at 20 °C and 24 °C and fed on two diets, with 16% and 20% lipid. At the end of the trial, fish were euthanized at two temperature conditions (0.6 °C or −0.6 °C) and kept on ice for 10 days at 4 °C to evaluate their freshness condition. Findings demonstrated that fish reared at 24 °C presented a lower lipid level and a higher daily growth index than those at 20 °C. Additionally, sensory analysis (Quality Index Method—QIM) and microbiological analysis revealed that fish reared at 24 °C showed better freshness conditions than those at 20 °C. However, the 16S rRNA metabarcoding analyses revealed a higher proliferation of genera associated with fish-spoiling bacteria in the skin microbiome of fish reared at 24 °C, i.e., Vibrio and Acinetobacter, which was not observed in the skin microbiome of fish reared at 20 °C. Nevertheless, the dietary lipid level did not have any influence on fish freshness. Therefore, our data suggest that the increase in temperature to 24 °C is beneficial for the growth and freshness profile (lower QIM and lower CFUs/cm2) of this particular species. Additionally, the lower euthanasia temperature (−0.6 °C) seems to lead to higher fish freshness than the normal temperature (0.6 °C). [ABSTRACT FROM AUTHOR]

Aquaculture requires new, economical, and eco-friendly protein sources to replace traditional fisheries and plant ingredients. Using agriculture by-products as protein sources would reduce land-based feed production pressure and waste production, promoting a circular economy and sustainable aquaculture. Distiller's dried grains with solubles (DDGS) is the main by-product of bioethanol production. Corn DDGS has a high protein level, but its high fiber content limits its use as a feed ingredient, particularly for carnivorous fish. Solid-state fermentation (SSF) uses lignocellulosic-rich substrates, such as DDGS, for microbial growth in the near absence of water, promoting enzyme production that degrades the lignocellulosic matrix, increasing free reducing sugars, protein, and antioxidant levels of the substrate. In the present work, the SSF of corn DDGS with Aspergillus carbonarius, A. ibericus, and A. uvarum was tested. Then, the digestibility of the most promising fermented DDGS (in terms of upgraded nutritional composition) was tested by including it in a reference diet (70% of a reference diet; 48% crude protein; 15% crude lipids) for European seabass (Dicentrarchus labrax) juveniles (171 g averaged weight; trial duration of 52 days). Among the fungi tested, Aspergillus ibericus led a generally higher upgrading of the DDGS nutritional composition, leading to a high amount of protein (from 42.7 to 49.7 g N/kg DM), phenolic compounds (1.49 to 4.86 mg/g caffeic acid equivalents), free sugars (9.5 to 31.9 mg/g), and enzyme production (45 U/g and 68 U/g of cellulase and xylanase, respectively), and a high reduction in acid detergent fiber and neutral detergent fiber content (up to 29 and 43%, respectively). Compared to the unfermented DDGS, fermented DDGS presented increased protein, lipids, starch, and energy digestibility, while phosphorous digestibility was similar. Compared to the reference diet, dietary inclusion of unfermented or fermented DDGS increased trypsin and chymotrypsin activities. The activity of digestive enzymes was not affected by the inclusion of fermented DDGS, except for amylase activity, which was lower with the fermented DDGS than with the unfermented DDGS diet. In conclusion, SSF of DDGS enhanced its nutritional value, increasing DDGS digestibility when included in diets for European seabass juveniles. [ABSTRACT FROM AUTHOR]

Simple Summary: The effect of feeding and feed deprivation on the regulation of feed intake in European seabass was evaluated. European seabass possess feed intake regulation mechanisms similar to those found in mammals and fish. Fasting and feeding conditions induce different responses in feed intake regulation mechanisms in European seabass. The present results are important to identify and understand the mechanisms of appetite regulation of European seabass, and therefore contribute to feeding optimization processes, ensuring the growth and sustainability of the aquaculture industry. The present study aimed to evaluate the effects of feeding or feed deprivation on the orexigenic and anorexigenic responses at the central (whole brain) and peripheral (anterior and posterior intestine, stomach, and liver) system levels in European seabass. For this purpose, a group of fish (208 g) was fed a single meal daily for 8 days (fed group) and another group was feed-deprived for 8 days (unfed group). Compared to the fed group, in the whole brain, feed deprivation did not induce changes in npy, agrp1, and cart2 expression, but increased agrp2 and pomc1 expression. In the anterior intestine, feed deprivation increased cck expression, while in the posterior intestine, the npy expression increased and pyyb decreased. In the stomach, the ghr expression decreased regardless of the feeding status. The hepatic lep expression increased in the unfed fish. The present results suggest a feed intake regulation mechanism in European seabass similar to that observed in other teleosts. [ABSTRACT FROM AUTHOR]

Simple Summary: The ever-growing human population is increasingly demanding more fish. As a response, aquaculture has become the fastest growing industry in its sector. Alternatives to fish meal, an unsustainable commodity used as the main protein source for carnivorous species, are urgently needed in aquafeeds. Recently, in Europe, seven insect species have been approved as potential ingredients for animal feeds, including fish feed. However, chitin, one of the components of an insect's exoskeleton, is indigestible for several economically valuable fish species, decreasing fish performance upon inclusion. This work aimed to isolate, from the European sea bass gastrointestinal tract, probiotic bacteria capable of producing chitinases to improve the use of diets containing high levels of insect meal. Based on the enhanced adaptability of gut microbial communities and the selective pressure of chitin-enriched diets on fish gut microbiota, bacteria were first isolated from the gastrointestinal tract of European sea bass fed chitin-enriched diets. Isolates were then comprehensively screened in vitro for important traits such as their ability to utilize chitin, gut-survival aptitude, and biosafety-related issues required to be considered eligible as probiotics by the European Food Safety Authority (EFSA). Insect meal (IM), recently authorized for use in aquafeeds, positions itself as a promising commodity for aquafeed inclusion. However, insects are also rich in chitin, a structural polysaccharide present in the exoskeleton, which is not digested by fish, resulting in lower fish performance. Through the application of a dietary pressure, this study aimed to modulate European sea bass gut microbiota towards the enrichment of chitinolytic bacteria to allow the isolation of novel probiotics capable of improving the use of IM-containing diets, overcoming chitin drawbacks. Five isoproteic (44%) and isolipidic (18%) diets were used: a fish meal (FM)-based diet (diet CTR), a chitin-supplemented diet (diet CHIT5), and three diets with either 25% of Hermetia illucens and Tenebrio molitor larvae meals (HM25 and TM25, respectively) or H. illucens exuviae meal (diet HEM25) as partial FM substitutes. After an 8-week feeding trial, the results showed a clear modulatory effect towards spore-forming bacteria by HM25 and HEM25 diets, with the latter being responsible for the majority of the chitinolytic fish isolates (FIs) obtained. Sequential evaluation of the FI hemolytic activity, antibiotic resistance, total chitinolytic activity, sporulation, and survival in gastrointestinal-like conditions identified FI645 and FI658 as the most promising chitinolytic probiotics for in vivo application. [ABSTRACT FROM AUTHOR]

Sardine cooking wastewaters are by-products of the canning industry with great potential for valorisation. We have hypothesized that they can be a source of aromas to enhance appetite when added to plant-based diets. The poor palatability of such diets often described in carnivorous species poses a recurring problem in fish farming, with harsh consequences on fish growth performance and flesh quality. Aromas from sardine cooking wastewaters were collected without processing (CW-A), processed through vacuum distillation (VD-A), or processed through liquid/liquid extraction with soybean oil (LLE-A) into plant-based diets. Each aroma was added to a plant-protein based diet for European seabass, at a concentration of 2 μg of 1-penten-3-ol/g diet, resulting in 3 experimental diets (CW, VD and LLE). A non-supplemented diet was used as a control. Each diet was assigned to triplicate fish groups (initial weight 95.7 g), that were hand-fed twice daily until apparent satiation in a recirculating saltwater system at 21 °C. After 18 weeks, fish growth performance and nutrient utilisation were evaluated. The expression in the brain of neuropeptides involved in feed intake regulation was also analysed. Moreover, flesh colour and texture were assessed instrumentally and by sensory analysis using a consumer panel. Fish fed LLE displayed a significantly higher feed intake than those fed CW which was correlated with an increased neuropeptide Y expression in the hypothalamus. However, LLE slightly hindered lipid metabolism, leading to lower available glucose and resulting in statistically similar final weights among diets. Despite variations in fillet hardness, the sensory panel revealed similar overall liking across all treatments. The findings indicate that aromas from sardine cooking wastewaters can modulate feed intake, but further refinement in processing or incorporation levels is required to potentiate their efficacy. • Aromas from canning wastewaters were added to a plant-protein based diet. • The highest intake of fish fed LLE diet was correlated with hypothalamus neuropeptide Y expression. • Growth remained unaffected in all treatments, but LLE increased feed conversion ratio. [ABSTRACT FROM AUTHOR]

In a previous study, it was shown that dietary supplementation with a carbohydrases and antioxidant-enriched extract (BSG-extract) produced by solid-state fermentation of brewer's spent grain (BSG) improved nutrients digestibility, feed, and protein utilization of European seabass juveniles. This work aims to investigate the effect of this BSG-extract on liver and intestine oxidative status and muscle lipid peroxidation (LPO) of European seabass. A plant-based diet (55.4% plant feedstuffs; PF) was used as a control. Four test diets were formulated by supplementing the control diet with the BSG-extract (0.4 or 0.8% diet), added directly to the diet (BSG4 and BSG8 diets), or used to pre-treat the PF mixture of the control diet (PreBSG4 and PreBSG8 diets). European seabass juveniles (IBW 22 ± 1 g) were fed the experimental diets for 66 days until apparent satiety. In fish fed BSG-extract diets, compared to the control diet, intestinal LPO was reduced up to 29-40% (p < 0.05); GPX, GR, and G6PD activities were increased compared to the control (p < 0.05). In the liver, LPO was similar among diets, but except for catalase and G6PD, fish fed BSG-extract diets had higher antioxidant enzyme activities than the control (p < 0.05). Except for the liver SOD activity, hepatic and intestinal antioxidant capacity was not affected by the dietary BSG-extract incorporation mode (p > 0.05). After 72 h of storage at 4°C, muscle LPO was higher than at time 0 h. Compared to the control, BSG-extract reduced muscle LPO levels up to 30% at time 0 h in fish fed diets BSG4, BSG8, and PreBSG8 (p < 0.008). Results indicate that dietary supplementation with BSG-extract increased the antioxidant level of diets, improved the intestine antioxidant capacity, and decreased LPO in European seabass juveniles' muscle. [ABSTRACT FROM AUTHOR]

The early host–pathogen interaction between European seabass (Dicentrarchus labrax) and Betanodavirus was examined by using juvenile fish infected intramuscularly with RGNNV (red-spotted grouper nervous necrosis virus). The time course selected for sampling (0–144 h post-infection (hpi)) covered the early stages of infection, with hematological, antioxidant and immunological responses examined. Early activation of the host's immune system was seen in the first few hours post-infection (6 to 9 hpi), as evidenced by an increase in tnfα, cd28 and c3 expression in the head kidney of infected fish. Most hematological parameters that were examined showed significant differences between sampling times, including differences in the number of thrombocytes and various leukocyte populations. The plasma lysozyme concentration decreased significantly over the course of the trial, and most antioxidant parameters examined in the liver showed significant differences over the infection period. At 144 hpi, peak expression of tnfα and il-1β coincided with the appearance of disease symptoms, peak levels of virus in the brain and high levels of fish mortality. The results of the study show the importance of analyzing the early interactions between European seabass and Betanodavirus to establish early indicators of infection to prevent more severe outcomes of the infection from occurring. [ABSTRACT FROM AUTHOR]

Seaweeds still possess a large undisclosed potential, mainly due to their constituent's richness, which may have several uses for society. In aquaculture, they may play a role as an ecological sustainable aquafeed supplement to increase overall health and fight pathogenic outbreaks. This study aimed to evaluate the general health modulation that the inclusion of Gracilaria gracilis could accomplish in the diet of Dicentrarchus labrax. Dried algae at 2.5% and 5% and algal extract at 0.35% inclusion levels were supplemented to seabass diet to evaluate possible growth, haematological, immunological, antioxidant, metabolic, and intestinal morphological modulations. The supplementations did not impact growth or feed utilization, and barely affected the haematological profile and some metabolic parameters. Nevertheless, it caused a marked outcome on lysozyme, some oxidative stress biomarkers, and intestine morphology, suggesting beneficial consequences from the algal inclusion. Dried algae powder, with a 2.5% inclusion, boosted immune response, with higher plasmatic lysozyme and intestinal acid goblet cells and protected against oxidative damages by improved enzymatic and non-enzymatic responses. Thus, we provide evidence that dietary seaweed application may be a path towards a more sustainable aquaculture industry. • Gracilaria gracilis in different percentages of supplementation plays distinct immunostimulant roles in Dicentrarchus labrax. • Oxidative stress is reduced in fish when the seaweed is provided as a 2.5% supplement. • Intestinal morphology and health may be modulated by G. gracilis supplementation. • Not all percentages of inclusion or ways of employment of the supplement are equally suitable for the fish diet. [ABSTRACT FROM AUTHOR]

A healthy gastrointestinal microbiota is essential for host fitness, and strongly modulated by host diet. In aquaculture, a current challenge is to feed carnivorous fish with plant-feedstuffs in substitution of fish meal, an unsustainable commodity. Plants have a limited nutritive value due to the presence of non-starch polysaccharides (NSP) which are not metabolized by fish. In this work we assessed the effects of NSP-enriched diets on European seabass gut microbiota and evaluate the selective pressure of plant feedstuffs towards gut microbes with NSP-hydrolytic potential, i.e. capable to convert indigestible dietary constituents in fish metabolites. Triplicate groups of European seabass juveniles were fed a fish meal-based diet (control) or three plant-based diets (SBM, soybean meal; RSM, rapeseed meal; SFM, sunflower meal) for 6 weeks, before recovering intestinal samples for microbiota analysis, using the Illumina's MiSeq platform. Plant-based diets impacted differently digesta and mucosal microbiota. A decrease (p = 0.020) on species richness, accompanied by a decline on the relative abundance of specific phyla such as Acidobacteria (p = 0.030), was observed in digesta samples of SBM and RSM experimental fish, but no effects were seen in mucosa-associated microbiota. Plant-based diets favored the Firmicutes (p = 0.01), in particular the Bacillaceae (p = 0.017) and Clostridiaceae (p = 0.007), two bacterial families known to harbor carbohydrate active enzymes and thus putatively more prone to grow in high NSP environments. Overall, bacterial gut communities of European seabass respond to plant-feedstuffs with adjustments in the presence of transient microorganisms (allochthonous) with carbohydrolytic potential, while maintaining a balanced core (autochthonous) microbiota. [ABSTRACT FROM AUTHOR]

Although the benefits of oleic acid (OA) have been established in mammals, its effects on fish remain understudied. The aim of this study was to evaluate the antioxidant potential of OA in the liver, intestine, and muscle of European sea bass juveniles fed diets containing different lipid levels. For that purpose, six diets with 16 or 22% lipids and 0, 1, and 2% OA were formulated and triplicate groups of European sea bass juveniles (21.4 g) were fed with these experimental diets for 9 weeks. Increasing dietary lipid levels or OA supplementation did not affect antioxidant enzyme activity in the liver and muscle. Superoxide dismutase (SOD) activity in the intestine increased with both the dietary lipid and OA levels, while glucose 6 phosphate dehydrogenase (G6PDH) activity increased only with dietary OA supplementation. Reduced glutathione (GSH) and total glutathione (tGSH) content were higher in the liver and intestine of fish fed the low-lipid diets, while in the high-lipid diets it was lower in the muscle than in the liver and intestine. Present findings suggest that OA plays a role in the antioxidant defense mechanisms of European sea bass, particularly at the intestine level, but additional research is required to further assess the potential benefits of incorporating OA into the diets. [Display omitted] • Oxidative stress in European sea bass is influenced by dietary composition in a tissue-related manner. • Oxidative status in the liver and muscle of European sea bass was not affected by dietary composition. • In the intestine, SOD activity was higher in fish-fed-high-lipid diets, supplemented with OA. • Intestinal G6PDH activity increased only with dietary OA supplementation. [ABSTRACT FROM AUTHOR]

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

Insect meals (IM) are being pointed out as a promising sustainable protein source. However, chitin in IM may negatively interfere with fish performance and nutrient availability. Given that carnivorous fish have a low or inexistent ability to digest chitin, novel strategies are needed to overcome chitin-imposed bottlenecks. Carbohydrolytic sporeforming probiotics offer a competitive industrial approach, being able to resist the harsh feed manufacturing process, transport, storage, and animal's gastrointestinal tract, while being able to increase the digestibility of otherwise indigestible components. Aiming to increase IM chitin digestibility, two chitinolytic sporeforming fish isolates (Fish isolates 645 (FI645) and 658 (FI658)), closely related to Bacillus licheniformis , were isolated from European sea bass (ESB) gastrointestinal tract, and incorporated (individually or as a mixture) in ESB diets with high defatted Hermetia illucens larvae meal (HM) levels (30% inclusion). FI were evaluated regarding their effects on ESB growth performance and digestibility. The spores were able to maintain their viability throughout the 180 days of diet storage at room temperature. Dietary inclusion of FI645 led to higher chitin digestibility. Concomitantly, the digestibility of dry matter, protein, and energy increased, overall leading to higher feed efficiency and protein efficiency ratio. Dietary inclusion of FI645 led to increased plasma N -acetylglucosamine (GlcNAc) levels. This is the first evidence for diet-mediated modulation of plasma GlcNAc concentrations. Dietary inclusion of FI645 also increased the expressions of the genes coding for N -acetylglucosamine kinase (nagk) and GlcNAc phosphomutase (pgm3) , key enzymes from the GlcNAc salvage pathway and the hexosamine biosynthetic pathway (HBP). On the other hand, no differences were found for the expression of N -acetyl-D-glucosamine-6-phosphate deacetylase (amdhd2) , a precursor enzyme for GlcNAc redirection to glycolysis. These results hint that free GlcNAc resulting from increased chitin digestibility might be preferentially redirected to protein O-GlcNAcylation processes through HBP in fish cells. Additionally, when challenged with Vibrio anguillarum , and after being feed for one month with the same diets, D645 also increased ESB survival from 52.5% to 77.5%, when compared to the control. Together, these results establish the potential of using FI645 as a probiotic for enhancing chitin digestion and acting as a prophylactic agent for ESB protection against V. anguillarum infection. This strategy opens novel possibilities for using commodities, including high chitin levels in aquafeeds, and reducing the use of antibiotics in aquaculture. • Fish isolate 645 increases chitin, protein, and energy digestibility and feed efficiency. • Increase in chitin digestibility increased N -acetylglucosamine in plasma. • The hexosamine biosynthetic pathway is potentially modulated by N -acetylglucosamine. • Fish isolate 645 increases European sea bass survivability to Vibrio anguillarum. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of taurine (tau) supplementation to low fishmeal (FM) diets on growth performance, oxidative status, and immune response of European seabass juveniles. Four isoproteic (46% crude protein) and isolipidic (19% crude lipid) diets were formulated to contain either 25 or 12.5% FM and a mixture of plant feedstuffs, supplemented or not with 1% tau. Twelve groups of 20 fish (IBW = 9.4 g) were fed each diet for 9 weeks. Reduction of dietary FM from 25 to 12.5% impaired growth performance, feed efficiency, and protein efficiency ratio but had no effect on nitrogen retention (% N intake). Independently of FM level, dietary tau supplementation improved growth performance and nitrogen retention without affecting feed efficiency. Dietary FM level reduction increased liver G6PDH activity, but did not affect lipid peroxidation or activities of redox key enzymes. Contrarily, dietary tau supplementation decreased hepatic G6PDH and GPX activities and lipid peroxidation. Gene expression COX-2 was not affected either by FM or tau levels but TNF-α increased with the reduction of FM level but not with the tau level. Dietary tau supplementation decreased Casp3 and Casp9 expression regardless of dietary FM level. Overall, this study evidenced that dietary tau supplementation improved growth performance and antioxidant response and reduced intestine inflammatory and apoptosis processes. [ABSTRACT FROM AUTHOR]

Abstract Viral necrosis virus (NNV) or nodavirus causes fish viral encephalopathy and retinopathy worldwide. In some cases, mortalities in aquaculture industry can reach up to 100%, some species being especially sensitive as is the case of European sea bass (Dicentrarchus labrax), one of the main cultured species in the Mediterranean, with the consequent economical loses. Development of new vaccines against NNV is in the spotlight though few researches have focused in European sea bass. In this study we have generated a recombinant NNV (rNNV) vaccine produced in Escherichia coli expressing the capsid protein and administered it to European sea bass juveniles by two different routes (intraperitoneal and oral). The last being considered non-stressful and desired for fish farming of small fish, which in fact are the most affected by NNV. Oral vaccine was composed of feed pellets containing the recombinant whole bacteria, and injected vaccine was composed of recombinant bacteria previously lysed. Our results revealed production of specific anti-NNV IgM following the two vaccination procedures, levels that were further increased in orally-vaccinated group after challenge with NNV. Genes related to interferon (IFN), T-cell and immunoglobulin markers were scarcely regulated in head-kidney (HK), gut or brain. Vaccination by either route elicited a relative survival response of 100% after NNV challenge. To our knowledge, this is the first report of a recombinant vaccine followed by no purification steps which resulted in a complete protection in European sea bass when challenged with NNV. Highlights • A nodavirus recombinant vaccine was generated in Escherichia coli. • Oral and intraperitoneal vaccination without any purification elicited specific antibodies. • Vaccines produced 100% RPS. • The two routes were similarly effective, being oral vaccination preferred. [ABSTRACT FROM AUTHOR]

Abstract Rendered fats can be sustainable alternatives to fish oil due to their lower price and wider availability. This study evaluates the effects of replacing fish oil by increasing levels of poultry fat (PF) on the nutrient utilization, growth performance, tissue composition and lipid metabolism of European seabass (Dicentrarchus labrax) juveniles. Homogeneous groups of 20 fish (19.1 ± 2.6 g) were subjected to a 12-h light/12-h dark photoperiod regime and kept in a recirculating saltwater system (salinity 35‰, 21 ± 1 °C) for 16 weeks. Triplicate groups of fish were fed a commercial-based diet as control (FO) and four isonitrogenous experimental diets, with 25 (25PF), 50 (50PF), 75 (75PF) and 100% (100PF) fish oil replacement. Soy lecithin was also tested in the diet with 100% PF (100PFL) as an emulsifier agent. The inclusion of PF did not affect nutrient's digestibility nor plasma metabolites at 24 h post-feeding. Final body weight (62–67 g), feed intake, feed conversion ratio, protein efficiency ratio and whole-body composition were similar among experimental diets. Selected lipogenic enzymes' activities were similar among FO and PF diets. The fatty acids profile of muscle, liver and heart reflected the dietary lipid source, decreasing PUFA and increasing MUFA contents with PF inclusion. Fish fed 25PF and 50PF were still able to provide the EPA and DHA muscle levels recommended for human consumption, but 100PF resulted in increased liver lipid accumulation and reduced muscle omega-3 levels. Including soy lecithin could significantly attenuate liver lipid content in fish fed PF-based diets. Highlights • The inclusion of poultry fat (PF) did not affect seabass nutrient's digestibility or plasma metabolites at 24 h post-feeding. • Growth performance, nutrient gain and whole-body composition remained similar in all fish. • High dietary n -6 PUFA were preferentially hydrolyzed and n -3 PUFA mainly deposited in muscle regardless their dietary level. • PF inclusion resulted in increased MUFA but decreased n -3 PUFA in muscle and liver, while the heart was less affected. • Total FO replacement by PF increased liver lipid accretion and HSI but soy lecithin supplementation attenuated this effect. [ABSTRACT FROM AUTHOR]

Abstract This study aims to understand the interactive effects of high dietary vegetable oils (VO) and carbohydrate (CH) content in European seabass cellular, humoral, and molecular innate immune responses to an acute stress. For that purpose, European sea bass juveniles (74.0 ± 1.5 g) were fed four diets differing in lipid source (fish oil (FO) or a blend of vegetable oils (VO)) and carbohydrate content (0% (CH–) or 20% (CH+) gelatinized starch). Nine fish per dietary treatment were sampled after 73 days of feeding and used as control whereas the remaining fish were subjected to an acute stress (netting, 1 min air exposure, and transfer to smaller tanks). Those fish were then sampled after 1 h and considered the stressed group. In the present study, dietary VO incorporation affected fish humoral immune parameters with a decrease of haematocrit, plasma peroxidase activity, and head-kidney mc2r and gr1 mRNA expression levels. Regardless of dietary treatment, higher cortisol levels were accompanied by an increase of several haematological, cellular, and humoral parameters in response to an acute stress. Dietary VO incorporation led to lower neutrophil numbers, plasma antiproteases activity, and head-kidney cox2 expression level in stressed fish. Fish fed CH+ diets showed a reduction of head-kidney mc2r expression levels in response to stress, while plasma cortisol remained unchanged, plasma NO decreases and antiproteases activity increased. In fish fed the VO diets, CH+ led to a decrease of plasma bactericidal activity compared to that of group CH-, while the opposite pattern was observed for plasma peroxidase. In conclusion, dietary substitution of FO by VO in CH– diet negatively affected the immune response in both undisturbed and stressed fish, while the effect of dietary CH incorporation in VO diet was not clear. Highlights • The interactive effects of high dietary vegetable oils (VO) and carbohydrate were tested in response to an acute stress. • Dietary fish oil replacement by vegetable oil negatively affected the immune response in undisturbed and stressed fish. • Dietary carbohydrate inclusion reduced NO plasma concentration and mc2r expression in head-kidney, regardless lipid source. [ABSTRACT FROM AUTHOR]

The current study evaluated the effects of dietary seaweed supplementation in European seabass juveniles (Dicentrarchus labrax) subjected to rearing temperature and salinity oscillations, simulating natural variations in pond aquaculture conditions. Two experimental diets where formulated: a control diet (CTRL) with no supplementation and one supplemented with 7.5% seaweed mix (SW 2.5% Fucus sp., 2.5% Gracilaria sp. and 2.5% Ulva sp.). Seabass from both dietary groups (40.7 g initial body weight) was subjected to either combined salinity and temperature oscillations, or to fixed conditions. Growth performance, innate immune, and oxidative stress responses were evaluated. Results showed that seaweed supplementation had no significant effect on the analyzed parameters. However, environmental oscillations revealed significant effects on growth performance and oxidative stress response. Fish subjected to salinity and temperature oscillations had a significantly lower weight gain and daily growth index than those subjected to fixed conditions, regardless of dietary treatment. Total glutathione, oxidized glutathione, and catalase increased in fish subjected to oscillatory conditions. Lysozyme and peroxidase were not influenced by either diet or environmental conditions. In conclusion, this particular dietary seaweed mix supplementation did not mitigate the negative effects of environmental oscillations on growth performance and innate immune responses in European seabass. [ABSTRACT FROM AUTHOR]

Diets with high-lipid levels may reduce fish growth, feed intake and increase fat deposition, jeopardizing fillet quality and shelf-life, which may be of major concern for the final consumer. To mitigate these potentially harmful effects, several nutritional strategies have been applied, including the use of functional ingredients. In this study, European sea bass (initial body weight 21.4 g) were fed six isonitrogenous (45% crude protein) diets with 16% and 22% lipid levels and supplemented with oleic acid (OA) at 0, 1, and 2% as a functional ingredient. Increasing dietary lipid levels did not affect fish growth performance, feed intake, and feed utilization. Independently of lipid level, dietary OA supplementation decreased feed intake and increased feed efficiency and Nitrogen (N) retention (% N Intake). Whole-body composition, hepatosomatic and visceral somatic indexes were not affected by dietary composition. The liver and muscle lipid contents were also not affected by dietary composition. The liver fatty acid profile was not affected by dietary lipid level, but monounsaturated fatty acid (MUFA) content decreased while polyunsaturated fatty acid (PUFA) content decreased with dietary OA supplementation. In the muscle, PUFA content decreased with dietary lipid levels, particularly C18:2n-6 (LA) and C20:2n-6. Dietary OA supplementation increased muscle MUFA, particularly OA (C18:1n-9), and reduced PUFA content. Compared to fish fed with 1OA diets, fish fed with 2OA diets presented a decreased area covered by lipids in the liver. Dietary OA supplementation increased hepatic glucose-6-phosphate dehydrogenase (G6PDH) activity and decreased malic enzyme (ME) activity, while no differences were observed in the activity of fatty acid synthase (FAS) and enzymes related to β-oxidation. Moreover, dietary OA supplementation decreased mechanistic target of rapamycin (mTOR) protein levels, while protein kinase B (Akt) and the phosphorylated state levels of both Akt and mTOR were not affected by dietary composition. Overall, dietary OA supplementation decreased feed intake and improved feed efficiency, without affecting growth performance, contributing to mitigate the potentially harmful effects of high-lipid diets in European sea bass. • Growth performance and feed utilization were not affected by dietary lipid levels. • OA supplementation decreases FI and improves FE and NR (% NI). • Dietary OA supplementation increased MUFA but decrease PUFA content in the liver. • Dietary OA supplementation decreased mTOR protein levels. [ABSTRACT FROM AUTHOR]

Plastic particles (PLs) are ubiquitous in aquatic ecosystems, and aquaculture production is susceptible to contamination from external or endogenous sources. This study investigated PL presence in water, fish feed and body sites of 55 European seabass produced in a recirculating aquaculture system (RAS). Fish morphometric parameters and health status biomarkers were determined. A total of 372 PLs were recovered from water (37.2 PL/L), 118 PLs from feed (3.9 PL/g), and 422 from seabass (0.7 PL/g fish; all body sites analysed). All 55 specimens had PLs in at least two of the four body sites analysed. Concentrations were higher in the gastrointestinal tract (GIT; 1.0 PL/g) and gills (0.8 PL/g) than in the liver (0.8 PL/g) and muscle (0.4 PL/g). PL concentration in GIT was significantly higher than in muscle. Black, blue, and transparent fibres made of man-made cellulose/rayon and polyethylene terephthalate were the most common PLs in water and seabass, while black fragments of phenoxy resin were the most common in feed. The levels of polymers linked to RAS components (polyethylene, polypropylene, and polyvinyl chloride) were low, suggesting a limited contribution to the overall PL levels found in water and/or fish. The mean PL size recovered from GIT (930 μm) and gills (1047 μm) was significantly larger than those found in the liver (647 μm) and dorsal muscle (425 μm). Considering all body sites, PLs bioconcentrated in seabass (BCF Fish >1), but their bioaccumulation did not occur (BAF Fish <1). No significant differences were observed in oxidative stress biomarkers between fish with low (<7) and high (≥7) PL numbers. These findings suggest that fish produced in RAS are mainly exposed to MPs through water and feed. Further monitoring under commercial conditions and risk assessment are warranted to identify potential threats to fish and human health and define mitigating measures. [Display omitted] • All fish had plastic particles (PLs) in at least two body sites (0.7 ± 0.4 PL/g). • Mean PL/g in gastrointestinal tract (GIT) was higher than liver, gills and muscle. • PLs in GIT and gills were significantly larger than those found in internal organs. • Man-made cellulose and PET were the most predominant polymer types. • Polymers common in RAS components had low occurrence levels. [ABSTRACT FROM AUTHOR]

A growth trial was conducted to determine the dietary taurine requirement for European sea bass juveniles fed plant feedstuffs-based diets. Eight isoproteic (45% crude protein) and isolipidic (18% crude lipid) diets were formulated containing a mixture of plant feedstuffs and fish meal (corresponding to 80% and 20% of total dietary protein, respectively) and taurine (Tau) levels ranging from 0.2 to 1.7% (diets 0.2Tau; 0.3Tau; 0.4Tau; 0.5Tau; 0.7Tau; 0.9Tau; 1.2Tau; 1.7Tau). Triplicate groups of 12 fish (IBW = 55 g) were fed each diet for 10 weeks. Dietary Tau level up to 0.7% improved growth performance while maximum feed efficiency and protein efficiency ratios were obtained with a dietary Tau level of 1.2%. Whole-body lipid content of fish fed the 1.2 and 1.7% Tau diets was lower than in the other groups, while whole-body protein and ash contents, and hepatosomatic and visceral indexes were not affected by diet composition. Daily growth index, nitrogen retention, and feed efficiency were fitted to Tau levels using different models. The five-saturation kinetics model was selected as the more parsimonious model, and based on this model the dietary Tau requirement for European sea bass juveniles under the present experimental conditions was estimated to be 0.47–0.50% DM. [ABSTRACT FROM AUTHOR]

Animal fats of terrestrial origin are often by-products from agro-food industries that could be valuable sustainable sources of lipids for aquafeeds. Four diets were hence tested in European seabass ( Dicentrarchus labrax ) juveniles (initial body weight, 20 g): a control diet with fish oil (FO) and three diets where a blend of poultry and mammal fats (50:50) replaced 50, 75 and 100% of the supplemental fish oil (50PFMF, 75PFMF and 100PFMF). All diets were isoproteic (51% dry matter, DM) and isoenergetic (23 kJ g − 1 DM). After 114 days of feeding the experimental diets, the apparent digestibility coefficients (ADCs) of nutrients were determined and fish growth performance evaluated. Postprandial plasma metabolites and muscle fatty acid profile were determined. Liver was also sampled for histologic evaluation and determination of lipogenic enzymatic activity. Protein and energy ADCs were not affected by the dietary treatments, but lipid ADC was lowest in the diet devoid of fish oil (100PFMF). Replacement of fish oil by a blend of land animal fats did not affect daily growth index, feed conversion ratio or nutrient utilization. Whole body composition remained unaffected by dietary treatments, but there was a significant increase in the hepatosomatic index of fish fed 100PFMF. Total replacement of fish oil by PFMF resulted in increased hepatic vacuolation, apparent steatosis and compromised glycogen deposition. Malic enzyme activity was lowest in fish fed 100PFMF. A significant reduction of muscle eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) content was observed with decreasing levels of dietary fish oil. Results indicate that juvenile seabass can effectively use diets with high levels of land animal fats as alternative lipid source, up to 75% fish oil replacement, without impairing nutrient intake, growth performance and nutrient utilization. Despite alteration in the muscle fatty acid profile, European seabass fed up to 75% PFMF can still retain high levels of EPA + DHA in the muscle (> 0.3 g/100 g). [ABSTRACT FROM AUTHOR]

Infections with myxozoan parasites are a source of concern for fish farm owners, as they can lead to significant economic losses. Owing to such potential detrimental impact, a comprehensive body of knowledge on myxozoans is required and, in this regard, elucidating different aspects of their ecology at the micro- and macroenvironment-level scales is crucial. The present study addresses the correlates of infections at both level-scales, for species of myxozoans occurring in Dicentrarchus labrax (Teleostei: Moronidae), an economically important species of fish for the aquaculture industry. Infection data for Sphaerospora dicentrarchi and S . testicularis (Myxozoa: Sphaerosporidae), and Ceratomyxa diplodae and C . labracis (Myxozoa: Ceratomyxidae), obtained from a total of 764 fish from wild ( N = 373) and cultured ( N = 391) environments, were used in the analyses. The mean prevalences of infection were 79.8% for S . dicentrarchi , 6.2% for S . testicularis and 21.7% for Ceratomyxa spp. At the microenvironment-level scale, a significant relationship was detected between the host sex, age, total weight and length and the prevalences of infection. At the macroenvironment-level scale, the prevalence of S . dicentrarchi was higher in wild than in cultured fish, contrary to that observed for Ceratomyxa spp. The results obtained from the Generalized Linear Model analysis suggest that, the control of the environmental variables which influence the occurrence of infection constitutes a crucial prophilatic measure in the minimization of economic losses occurring in fish farming systems. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the hypothalamus fatty acid (FA)-sensing mechanisms response to different FA in European sea bass. For that purpose, fish (body weight of 90 g) were intraperitoneally (IP) injected (time 0 h) with five long-chain unsaturated fatty acids, namely, docosahexaenoic acid (DHA; C22:5n3); eicosapentaenoic acid (EPA; C20:4n3); α-linolenic (ALA; C18:3n3); linoleic acid (LA; C18:2n6) and oleic acid (OA; C18:1n9) at a dose of 300 μg kg−1, or with 0.9% saline solution (control). Feed intake (FI) was recorded at 3, 6, and 24 h after the IP injection. One week later, fish were IP injected with the same FA, and the hypothalamus was collected 3 h after the IP injection for measurement of molecules related to FI regulation and FA-sensing mechanisms. Cumulative FI (g/kg/day) was not affected by treatments. However, compared to the control, FI increased with the OA treatment at 6 h after the IP injection. FI decreased with mealtime in the DHA and LA groups. Gene expression of orexigenic (npy / agrp) and anorexigenic (cart2 / pomc1) neurons was not affected by the FA treatments. Attending the enzymes involved in the FA-sensing mechanisms activation, compared to the control carnitine palmitoyltransferase I (CPT1) and ATP citrate lyase (ACLY) activity were not affected by FA treatments. Contrarily the key enzymes of lipid metabolisms, malic enzyme and hydroxyacylCoA dehydrogenase was higher in fish that received the EPA and OA treatment, than fish treated to the control. Overall, the results of the present study indicate that gene expression of orexigenic and anorexigenic neurons was not affected at 3 h after IP injection with different FA. However, the activity of key enzymes of lipid metabolism was differently affected by circulating FA, indicating that FA-sensing mechanisms respond to different FA. Further studies are required involving different sampling times to further characterize the response of FA-sensing mechanisms to FA. These findings may be of relevance to the aquaculture industry in an era where alternative lipid sources are being increasingly used. [Display omitted] • Fatty acid sensing mechanisms were evaluated for the first time in European seabass • IP injection with DHA and LA increased FI 3 h after the treatment • OA increased FI of European seabass 6 h after the IP injection • FA treatments did not affect npy, agrp1/2, pomc1 , and cart2 gene expression in the hypothalamus • EPA treatments modulate lipogenesis and β-oxidation in the hypothalamus of European seabass [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effects of dietary methionine (Met) and taurine (Tau) supplementation on growth performance, feed utilization, and oxidative status of European sea bass juveniles. For that purpose, a 12-week growth trial was performed to test four isolipidic (18%) and isonitrogenous (6.7%) practical diets, containing 82% of the protein from plant origin and 18% from fish meal. Diets were formulated to have a Met level below (LMet) or above (HMet) requirements and were supplemented or not with 1% Tau (LMetTau and HMetTau). No dietary Met or Tau effects were observed on growth, feed utilization, and whole-body composition. Increasing dietary Met level led to increased catalase (CAT) and glutathione peroxidase (GPX) activities in the liver and total (tGSH) and reduced (GSH) glutathione in the intestine, while decreasing glutathione reductase (GR) and GPX activities in the intestine. Most of these effects were only observed in fish fed diets not supplemented with Tau. Dietary Tau supplementation decreased intestinal tGSH, GSH and oxidised (GSSH) glutathione content, the activity of GPX both in liver and intestine, and glucose-6-phosphate dehydrogenase (G6PDH) activity in the liver. Dietary Tau supplementation also affected hepatic CAT and intestinal GR activities, but effects were dependent of the dietary Met level. Overall, European sea bass seems to cope well with a plant-protein rich diet without Met or Tau supplementation. Both dietary Met and Tau were shown to modulate fish antioxidant response but without altering the oxidative damage level. [ABSTRACT FROM AUTHOR]

A feeding trial was carried out to assess the effect of partially replacing fish meal (FM) by Black soldier fly pre-pupae meal (HM) in diets for European seabass Dicentrarchus labrax juveniles. A FM-based diet was used as a control and three other diets were formulated to include 6.5%, 13%, and 19.5% of HM, replacing 15%, 30% and 45% of FM respectively. Each diet was fed to triplicate groups of fish (initial weight: 50 g) for 62 days. At the end of the trial, there were no differences among groups in growth performance or feed utilization. Plasma metabolic profiles also remained unaffected, except that plasma cholesterol was reduced with dietary HM inclusion. The apparent digestibility coefficients (ADC) of protein, lipids, dry matter, organic matter, and energy were generally high, and not affected by the dietary treatment. The ADC of arginine, histidine, and valine were higher in HM diets when compared to the control. Amylase and protease activities were not affected by dietary HM, while lipase activity was lower in HM 6.5 diets than in the control and HM 19.5 diets. In conclusion, up to 19.5% of HM, corresponding to 22.5% of total dietary protein, may successfully replace FM in diets for juvenile European seabass, without adverse effects on growth performance, feed utilization or digestibility. [ABSTRACT FROM AUTHOR]

The effects of replacing fishmeal by increasing levels of hydrolyzed feather meal (HF) on the nutrient utilization, growth performance and muscle fatty acid composition of European seabass ( Dicentrarchus labrax ) juveniles were evaluated. The humoral non-specific immune parameters were also evaluated in plasma. A growth trial was conducted for 18 weeks, using a practical feed formulation with 32% fishmeal and no HF added, as control (FM). Three experimental diets were formulated with the inclusion of 5 (HF5), 7.5 (HF7.5) and 12.5% HF (HF12.5), leading to a replacement of about 28, 55 and 76% fishmeal compared to the FM diet. The protein apparent digestibility coefficient (ADC) was lowest in the HF12.5 diet and was associated with higher nitrogen fecal losses, but N gain was similar among diets. Phosphorus ADC was significantly improved with the dietary incorporation of HF, decreasing fecal P losses into the environment. Fish fed the diets containing HF grew as well as those fed the FM diet. The feed intake, feed conversion ratio and protein efficiency ratio were statistically similar among dietary treatments. The protein and lipid whole body composition, as well as the muscle long-chain omega-3 fatty acid profile, remained unaffected by the fishmeal replacement. The immunological parameters assessed (lysozyme, peroxidase and ACH50) were not affected by the HF inclusion. The present study shows that an inclusion of up to 12.5% HF (76% fishmeal replacement) is possible in European seabass without impairing feed intake, growth, immune response or EPA and DHA levels in the muscle. Although energy and protein apparent digestibility coefficients (ADC) were lowest in the HF12.5 diet, energy and nutrient gain remained similar among dietary treatments. Altogether results suggest that HF is an interesting ingredient to be used in practical feed formulations for this species. [ABSTRACT FROM AUTHOR]

The nutritional value of whole wheat, corn, rye and barley was evaluated for European sea bass. Four isoproteic and isolipidic diets containg 30% of each whole cereal meal were formulated. A growth trial and a digestibility trial were conducted and fish performance was evaluated in terms of growth, feed intake, feed utilization, macronutrients digestibility, liver composition, glycaemia and cholesterolemia levels and gut histomorphology. Growth and feed utilization ranged from 1.43 to 1.46 and from 0.55 to 0.58, respectively, and were similar among experimental groups. Whole body and liver composition, hepatosomatic and visceral indexes were also not affected by dietary composition. Corn diet revealed the lower dry matter (62.9) and starch (55.5) apparent digestibility coefficients. Protein digestibility in fish fed the rye diet was the lowest of all groups (91.3) and differed from that of wheat diet group (93.2), which might be due to antinutritional factors present in this feedstuff. Plasmatic glucose levels suggested a slower absorption rate in fish fed barley and corn diets. No signs of enteropathy related to the whole cereal meals were observed. Among cereals tested, rye seemed to be the less tolerated by sea bass, although all diets were well accepted and sea bass performed equally well with all diets. [ABSTRACT FROM AUTHOR]

This study evaluated the impact of replacing 50 and 100% fishmeal protein by defatted (d-) Tenebrio molitor (TM) in diets for market-sized European sea bass. Growth performance, nutrient utilization and fillet nutritional, organoleptic and sensory quality traits were assessed after 16 weeks of feeding. The substitution of 50% fishmeal protein by d TM significantly improved feed efficiency without affecting fish growth performance. Muscle fat and n-3 PUFA content remained similar among fish, resulting in EPA and DHA levels above the recommended daily intake of 250 mg for human consumption. Despite some differences in the muscle histomorphometric and instrumental texture measurements, consumers could not perceive differences between muscle samples of fish fed the control or d TM diets. All samples were characterized by their soft and pleasant texture, and d TM samples were also associated with a "juicy texture". • Total FM replacement by d TM does not compromise sea bass growth. • Muscle EPA + DHA levels of sea bass fed d TM were above 250 mg 100 g−1 WW. • PUFA/SFA above 0.45 is assured in the muscle of sea bass fed d TM. • Rates of consumer-liking are equally high for sea bass fed CTRL and those fed d TM. • Muscle of sea bass fed d TM is associated with a juicy texture. [ABSTRACT FROM AUTHOR]

Hydrolysates from high-protein coproducts are rich in bioactive peptides (small amino acid chains with properties beyond their nutritional value). When included in aquafeeds, they may promote fish robustness while increasing animal blood value and minimizing waste, contributing to a circular economy. This work assessed how innovatively produced blood hydrolysates (BH) included in plant-based diets for European seabass (Dicentrarchus labrax) affected growth performance and resistance to Tenacibaculum maritimum infection. Three fractions of swine BH obtained by autohydrolysis (AH) or enzymatically were selected. AH fraction was oven-dried, whilst the enzymatically obtained BH were further submitted to a micro (RMF) and nanofiltration (RNF) and the respective retentates freeze-dried. A commercially based diet was formulated, where 50% of fishmeal was replaced by vegetable proteins, and used as negative control (NC). Each BH fraction was then added at 3% to the NC and further compared to a fishmeal-based diet (positive control, PC); all diets remained isolipidic and isoproteic. Diets were assigned to triplicate groups of European seabass juveniles (12.3 ± 1.4 g) and fed three times daily until apparent satiation in a recirculating saltwater system. After a 12-week growth trial, fish were bath challenged with T. maritimum and cumulative mortality followed for 8 days. A digestibility trial was also performed in parallel. Hydrolysates-containing diets had a significantly lower apparent digestibility coefficient (ADC) of dry matter compared to the PC, but RNF did not differ from the NC. RMF and AH had lower lipid ADCs than both controls, while the RNF only differed from the PC. Mineral ADCs of PC, NC and RNF were similar. Calcium ADC in RMF and AH was significantly lower than all other diets; RMF also displayed lower copper and potassium ADCs. Fish fed PC had the highest final weight, followed by NC and RNF. Daily growth index and feed conversion ratio (FCR) of RNF was similar to both controls. RMF induced the lowest final weight, highest FCR and reduced villus length in anterior intestine. This diet has also resulted in increased plasmatic peroxidase, but lower lysozyme, compared to all other treatments, showing the lowest disease resistance. Results clearly show that the RNF was the only test diet that significantly reduced European seabass mortality after T. maritimum infection, without affecting fish growth in relation to a practical plant-protein based diet, highlighting its high potential for aquafeeds supplementation. • Fractions of swine blood hydrolysates were obtained from an industrial by-product. • Hydrolysates were included in plant-based diets for European seabass. • One fraction (RNF) improved fish survival post T. maritimum infection. • Growth and feed conversion ratio of RNF was similar to CTRL diets [ABSTRACT FROM AUTHOR]

This work was focused on evaluating the occurrence of endocrine-disrupting compounds (EDCs) in fish muscles, such as bisphenol analogues, personal care products, including some UV-filters and musk fragrances, and selected pesticides. A total of 238 muscle samples of three fish species (Platichthys flesus , Mugil cephalus, and Dicentrarchus labrax) of an important estuary ending in the North East Atlantic Ocean (Douro River estuary, Portugal), in different seasons of the year, was analysed. M. cephalus was the species with a greater occurrence of contaminants, mainly in fishes collected during the spring. Bisphenol A was the main bisphenol analogue detected with an average content of 23.1 μg/kg wet weight (w.w.). Among chemicals used in personal care products, galaxolide, tonalide, and 2-ethylhexyl salicylate, were the most often found, being present in 15.9% (2.2–538.4 μg/kg w. w.), 4.6% (1.1–57.8 μg/kg w. w.) and 3.4% (3.9–56.1 μg/kg w. w.) of the samples, respectively. About 14% of the samples contained residues of at least one pesticide, being alachlor, aldrin, p,p' -DDT, permethrin, and prochloraz the main chemicals observed, varying from 0.1 μg/kg w. w. (p,p' -DDT) to 37.8 μg/kg w. w. (prochloraz). The daily intake estimates of the most frequent EDCs found in the fish muscles suggested that there are no health concerns, based on the recommended weekly consumption of fish for adults. • Levels of EDCs in fishes collected during one year in the Douro River estuary. • About 25% of the samples (n = 238) contained at least one endocrine disruptor. • Galaxolide, tonalide, and p,p' -DDT were frequently detected in fish muscles. • There are no health concerns at the dietary exposure levels estimated for the EDCs. [ABSTRACT FROM AUTHOR]

Understanding the underlying mechanisms responsible for regulation of food intake in fish is crucial for proper formulation of aquafeeds and consequently ensure the best growth performance of fish. Over the last decade, the study of the impact of insect meal-based diets on growth performance and voluntary feed intake of several fish species has emerged, but little is known about their influence on anorexigenic potential. This is the first study evaluating short- and mid-term responses of European sea bass (Dicentrarchus labrax) fed diets not only with partial, but also with total fishmeal (FM) replacement by defatted Tenebrio molitor larvae meal (d TM). A fishmeal-based diet was used as a control (CTRL) and two other diets were formulated to include 20% and 40% of d TM, replacing 50% and 100% of fishmeal (FM), respectively. The short-term response was evaluated after the first exposure to the experimental diets, whereas the mid-term response was evaluated after 7 days of feeding. In both short- and mid-term trials, food intake was registered. Hepatic and plasmatic metabolites and the expression of hypothalamic and telencephalic neuropeptides involved in food intake were assessed 2 and 24 h post-feeding. No differences occurred in food intake levels, neither in the short- nor mid-term. In the short-term, plasmatic glucose levels increased in fish fed TM100, regardless post-feeding sampling time. In the mid-term, fish fed TM100 had the highest levels of triglycerides in liver and the lowest levels of α-amino-acids in plasma, irrespective of post-feeding sampling time. At central level, dietary treatment did not alter the expression of neuropeptide Y (npy), agouti-related protein 2 (agrp2), pro-opio melanocortin a (pomca) or cocaine- and amphetamine-related transcript 2 (cartpt2) in hypothalamus and telencephalon. The obtained results suggest that partial and total FM replacement by d TM does not influence short- and mid-term regulation of food intake in European sea bass. Nonetheless, changes observed in hepatic and plasmatic metabolite levels of fish fed TM100 may indicate alterations of intermediary metabolism in the long-term. • First time assessment of impact of IM on food intake regulation in fish at short- and mid-term. • Total FM replacement by d TM did not affect food intake. • Total FM replacement by d TM did not affect mRNA abundance of neuropeptides • regulating food intake. • Total FM replacement induce changes in hepatic and plasmatic metabolites. [ABSTRACT FROM AUTHOR]

The main goal of this work was to compare the dietary inclusion of poultry fat with mammal fat, and to understand the possible beneficial effects of an emulsifier in commercial-based diets for European sea bass (Dicentrarchus labrax) tested under an industrial scale, without control of environmental conditions. Effects on growth performance and muscle quality in terms of fatty acid (FA) profile, textural properties and colour, were evaluated. For this purpose, four isoproteic (45%) and isolipidic (21%) diets were formulated using the same protein sources. The lipid fraction of the diets varied, and comprised 55% fish oil and either 45% poultry fat or mammal fat, with or without an emulsifier. A 12 weeks' growth trial was carried out with commercial-sized juveniles (255.7 ± 15.2 g) in an open-through aquaculture system. All diets were equally well-accepted by the fish, with no differences in terms of feed efficiency and growth. The inclusion of the emulsifier led to increased whole body lipids and energy contents, regardless of the type of fat. Fish fed with the mammal fat diet had a higher muscle lipid content, but lower n-6 PUFA, without changes in the n-3 PUFA and in the n-3/n-6 PUFA ratio. The dietary inclusion of mammal fat, contrarily to poultry fat, resulted in increased amounts of EPA and DHA in the muscle which were within the recommended levels for human consumption to decrease the risk of cardiovascular diseases (> 0.25 g 100 g−1). Fish fed mammal fat also demonstrated an increase of muscle instrumental lightness and hardness. These results indicate that terrestrial animal fats can be promising sources of lipids for aquafeeds, highlighting mammal fat as a viable by-product to include in European sea bass diets. • Dietary inclusion of 45% MF or PF does not compromise sea bass growth or efficiency. • The emulsifier led to increased whole body lipids and energy content. • The highest muscle total lipids were observed in fish fed MF. • Fish fed MF had lower muscle n-6 PUFA without changes in n-3 PUFA and n-3/n-6 ratio. • MF assured muscle EPA + DHA recommended levels (> 0.25 g 100 g−1) for human consumption. [ABSTRACT FROM AUTHOR]

Aquafeed is one of the main costs in aquaculture and major efforts are being made to find sustainable ingredients that could improve production sustainability and efficiency. Our research focused on the inclusion of glycerol in the feed of European seabass (Dicentrarchus labrax), as it is a cheap carbon substrate expected to enter metabolism through the glycolytic pathway. The Nuclear Magnetic Resonance (NMR) spectroscopy provides accurate and high-throughput metabolic profiles, allowing quantification and evaluation of the effects of experimental diets in the context of fish nutrition. The aim of the present study was to assess the applicability of the automated online profiling routine Bayesil to fish blood plasma and compare with the manual targeted metabolite profiling approach. After a 60-day feeding trial (0%, 2.5%, 5.0% glycerol supplemented diets), fish were sacrificed at 6 h and 24 h after last meal and blood was sampled. Filtered plasma samples were analysed by NMR, followed by two metabolite-profiling approaches: i) an automated spectral profiling provided by the Bayesil platform, and ii) a manual metabolite profiling. Spectra were analysed with the automated Bayesil routine, identifying and quantifying 51 metabolites, in a reproducible, fast and user-independent method. On the other hand, the manual approach only managed to quantify 20 metabolites. However, under supraphysiological concentrations of glycerol, namely in the 5.0% diet, the Bayesil algorithm was not able to properly integrate the glycerol and glycine signals. The Bland-Altman and PLS-DA analysis revealed differences; nonetheless, with the exception of acetic acid, creatinine, formate, glutamine and threonine, all other metabolites presented a low bias and/or a strong correlation coefficient. Overall, it is expected a reasonable tradeoff between the accuracy in metabolite quantification and the increase of variables. The automated Bayesil database may be applied as a useful tool for systematic monitoring of fish plasma profile in aquaculture research and industrial quality control analysis, to generate robust variance-based multivariate statistical models. To our knowledge, this is the first time a NMR-based high-throughput automated routine is evaluated for aquaculture research. • Semi-automated (Bayesil) 1H NMR analysis of fish plasma quantified 51 metabolites. • User-curation required in specific nutritional studies (supraphysiological glycerol levels). • New tool for systematic monitoring of fish plasma for fish aquaculture research [ABSTRACT FROM AUTHOR]

This work aimed to evaluate the potential of a carbohydrases-rich extract produced by SSF of BSG to enhance the nutritional value of plant-based diets for European seabass (Dicentrarchus labrax) juveniles. BSG was fermented by A. ibericus (MUM 03.49) to obtain an aqueous enzymatic extract (1178 and 8317 U g−1 cellulase and xylanase activity, respectively). A control (50% protein; 18% lipids) diet was formulated with 55% DM of plant feedstuffs (PF), and four other diets were formulated similarly to the control but including 0.4% and 0.8% DM of lyophilized extract (BSG-extract), corresponding to 4000 and 8000 U of cellulase kg−1 of diet, directly included in the diet (BSG4 and BSG8 diets) or used to pre-treat the PF mixture of the control diet (PreBSG4 and PreBSG8 diets). Pre-treatment of PF with BSG-extract increased three-fold the dietary reducing sugars content and two-fold the antioxidant activity than the control diet. Cellulase and xylanase activities were highest in diets including BSG-extract directly added than pre-treated PF diets. These diets were fed to European seabass (IBW = 22 ± 1 g) for 66 days. Dietary supplementation with BSG-extract, mixed in the diet or used as a pre-treatment of PF, did not affect growth performance and whole-body composition (p>0.05) of European seabass but increased feed efficiency (up to 18%; p <0.05) and protein utilization (up to 22%; p <0.05). Nitrogen retention and total alkaline proteases activity were higher in fish fed with the PreBSG4 and PreBSG8 diets (p <0.01) than with the BSG4 and BSG8 diets. In contrast, BSG4 and BSG8 diets increased plasma glucose and decreased cholesterol levels compared to the control (p <0.05). In conclusion, this work showed the effectiveness of an extract produced by SSF of BSG, with high carbohydrases activity, to enhanced feed and protein utilization by European seabass, without affecting growth performance. Moreover, using BSG-extract to pre-treat PF seems to be more effective in improving protein utilization than adding it directly to the diet. This study demonstrated the feasibility of BSG valorization through SSF to produce a functional additive for aquafeeds. The novel produced BSG-extract simultaneously contributes to the sustainability of resources in a circular economy approach and increases the nutritional value of plant feedstuffs. • Solid-state fermentation of brewer's spent grain produced highly effective carbohydrases. • Pre-treatment with BSG-extract efficiently disrupted the lignocellulosic structure of plant-feedstuffs. • Feed and protein utilization improved up to 18% and 22%, respectively, in European seabass juveniles fed the BSG-extract diets. • Plant feedstuffs pre-treatment increased feed efficiency, protein retention, and intestinal proteases activity. [ABSTRACT FROM AUTHOR]

The homeostatic regulation of food intake in fish has been thoroughly studied in the last years with dietary nutrient composition is one of the factors involved. Despite several studies addressed the impact of insect meal-based diets in food intake of fish, there is no knowledge about their impact in mechanisms of food intake regulation. This study aimed to explore underlying mechanisms through evaluation of dietary fishmeal (FM) replacement by defatted (d-) Tenebrio molitor (d TM) larvae meal in European sea bass. Fish (55 ± 2 g) fed a FM-based diet (CTRL) were compared with those fed two experimental diets containing increasing levels of d TM to replace 40 and 80% of FM (TM40 and TM80, respectively). After ten weeks of feeding, fish food intake was calculated; samples of plasma and different brain areas (hypothalamus and telencephalon) were collected at different post-prandial times (2, 6 and 24 h after feeding) to evaluate circulating metabolites and mRNA abundance in hypothalamus and telencephalon of neuropeptides involved in food intake regulation. No differences occurred in food intake and weight gain among diets. Plasma cholesterol levels decreased 24 h after feeding in fish fed TM40; fish fed d TM diets had higher cholesterol levels, 2 and 6 h after feeding, than those fed CTRL diet. Increased non-esterified fatty acids (NEFA) levels occurred in plasma of fish fed TM80, regardless of the sampling time. At central level, no changes occurred in the mRNA abundance of neuropeptide Y (npy), agouti-related protein 2 (agrp2), pro-opio melanocortin a (pomca) or cocaine- and amphetamine-related transcript 2 (cartpt2). The obtained results suggest that dietary FM replacement by d TM up to 80% in European sea bass does not affect food intake or its central homeostatic regulation, supporting the use of d TM as FM replacement in diets for European sea bass. • First time assessment of impact of IM-based diets on food intake regulation in fish. • 80% FM replacement by d TM did not affect food intake and growth. • 80% FM replacement by d TM did not affect mRNA abundance of neuropeptides regulating food intake. [ABSTRACT FROM AUTHOR]

Considering the increasing demand towards "ready-to-cook" processed seafood products, recognised as being potential contributors to high sodium (Na) intake by consumers, this study aimed to assess the effect of sodium chloride (NaCl) reduction on physicochemical, microbiological and sensory properties of European seabass (Dicentrarchus labrax) sausages stored in chilling conditions during 5 weeks. Three formulations were tested in comparison with a control (100% NaCl, CTR): (i) 50% NaCl+50% ME (oleoresins microcapsules) (F1); (ii) 50% NaCl+50% KCl (F2); and (iii) only 50% NaCl (F3). The NaCl reduction mainly affected the texture and the salty taste, resulting in softer and perceived as less salty sausages after processing. However, hardness differences disappeared after 5 weeks. It seems that an antioxidant protection was obtained in sausages formulated with oleoresins microcapsules. No or low growth of psychrotrophic and mesophilic bacteria was observed (≤2.40 log CFU/g). Decreasing NaCl content and/or partially replacing it (50%) by KCl or oleoresins microcapsules seem to be suitable solutions to reduce Na (30.9–36.3%) levels, while maintaining the chilled sausages quality for 5 weeks. The partial replacement of NaCl by KCl also allows obtaining a product richer in K (997.2 mg/100 g), which ingestion may contribute for a cardiovascular protective effect. • 50% NaCl replacement by KCl and oleoresins microcapsules was investigated. • 50% NaCl reductions mainly affected the texture and the salty taste. • Oleoresins microcapsules also seemed to confer an antioxidant protection. • High potassium nutritional contribution was achieved (≥42.7%). • Such solutions seem to be suitable to reduce sodium levels. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the effect of dietary taurine (Tau) in intermediary metabolism, oxidative status, and Tau biosynthesis capacity in European seabass juveniles. For that purpose, four diets (45% protein and 18% lipid) were formulated with increasing levels of Tau (0.2, 0.5, 0.7, and 1.2% of DM) and fed to triplicate groups of fish (IBW 55g) until apparent visual satiety for 10 weeks. Total bile acid content in the liver increased as dietary Tau supplementation increase, while the opposite occurred in the plasma. Plasma glucose, total cholesterol, HDL, and LDL cholesterol decreased, while total and indirect bilirubin increased with the increase of dietary Tau level. The activity of the key intermediary enzymes measured decreased with the increase of dietary Tau up to 0.7%. Regarding the antioxidant-related enzymes, dietary Tau supplementation decreased hepatic catalase, glutathione peroxidase, glutathione reductase, and superoxide dismutase activities with the maximum effects being observed as dietary Tau increased from 0.2 to 0.5%. Overall, there was a decreasing trend of hepatic lipid peroxidation with the increase of dietary Tau. This study is the first to demonstrate that in European seabass juveniles the capacity of expressing cysteine dioxygenase, an enzyme involved in the cysteine sulfinate pathway for Tau synthesis, although its expression was not affected by Tau levels in the diet. This study indicates that dietary Tau levels affect intermediary metabolism, namely carbohydrates and lipidic metabolism, and improve the antioxidant status of European seabass juveniles. Furthermore, although CDO expression was detected, European seabass seems unable to regulate its activity, these results supporting the essentiality of Tau for this species. • Tau appears to have a hypocholesterolemic and hypoglycemic effect in European seabass • Dietary Tau supplementation decreased enzymes activity involved in oxidative status, indicating the antioxidant action of Tau • European seabass express cysteamine dioxygenase but do not to regulate its activity. [ABSTRACT FROM AUTHOR]

This study assessed both the effectiveness of a physical-mechanical rupture method and the ability of feed additives (phytogenic compounds, alginate oligosaccharide and nucleotides) to enhance the utilization of G. gracilis by European seabass. A commercial-based diet was used as control diet (CTRL) and compared with five isoproteic (53.5% Dry matter, DM) and isolipidic (14.9% DM) diets containing 8% of G. gracilis. This seaweed was either unprocessed (diet GRA) or subjected to physical processing (diet GRAP). The three additive-containing diets were formulated by supplementing the GRA diet with either 0.02% phytogenic compounds (PHY), 2.5% oligo-alginate (OAS) or 0.08% free nucleotides (NUC). Triplicate groups of nineteen fish (29.7 ± 0.02 g) were distributed by 50 L tanks (11.3 kg m−3) and fed the experimental diets to satiety during 106 days. By the end of the trial, growth performance and nutrient utilization (specific growth ratio, feed conversion ratio, apparent digestibility coefficients, nutrient balance, intestinal brush border membrane enzyme activities and plasma metabolic parameters), gut histomorphology, antioxidant and immunological status of fish were evaluated. The ability of fish to digest seaweed-rich diets was largely improved by the technological processing of G. gracilis, albeit nil effect on fish specific growth rate (1.0 in all groups). This major achievement was associated with increased ability of GRAP to digest protein (84 vs 68% in GRA) and energy (64 vs 38% in GRA). The use of feed additives in Gracilaria -rich diets was less efficacious in improving European sea bass nutrient and energy ADCs, but have still improved the overall digestibility of those diets. Fish fed alginate oligosaccharide was mainly associated with increased activity of anterior intestine enzymes, particularly intestinal alkaline phosphatase (IAP; 174.4 vs 104.7–120.6 μm min−1 g−1 in Gracilaria -rich diets). Moreover, the algae technological processing and both the nucleotides and the alginate oligosaccharide seem to have positively affected the intestinal villus width compared to the negative impact seen in fish fed GRA. The tested additives had limited impact on oxidative stress, although glutathione peroxidase (GPx; 2.1 μmol min−1 mg protein−1) and catalase (CAT; 35 μmol min−1 mg protein−1) activities were lowest in fish fed NUC and PHY, respectively. It can be concluded that the physical processing of Gracilaria sp. or the addition of either oligo-alginate or nucleotides can effectively increase the nutritional value of this seaweed for European seabass diets. • Physical processing of G. gracilis improves the ability of fish to digest diets containing 8% seaweed. • Algae technological processing affected gut histomorphology significantly increasing villus width. • Alginate oligosaccharide supplementation increased intestinal alkaline phosphatase activity of anterior intestine. • The tested additives had limited impact on oxidative stress indicators (LPO, TG, GPx, GST, GR and CAT). [ABSTRACT FROM AUTHOR]

• Occurrence of 7 bisphenols in fish from NE Atlantic Ocean was investigated. • Levels of bisphenols in internal tissues correlated with higher microplastic intake. • Microplastics (MP) may be a source of bisphenols to wild fish. • Exposure assessment of bisphenols through fish consumption was performed. • The consumption of fish contaminated with MP may lead to a higher risk of exposure to bisphenols. In the present study, the levels of bisphenol A (BPA) and analagous compounds in muscle and liver of fish (Dicentrarchus labrax, Trachurus trachurus, Scomber colias) from the North East Atlantic Ocean were determined and the risk of their consumption by humans was assessed. The potential relationship between bisphenol concentrations and microplastic (MP) contamination of fish was also investigated. Fish from all the species had BPA in the liver and muscle, and bisphenol B (BPB) and bisphenol E (BPE) in the muscle. The highest concentration of BPA in the liver (302 ng/g dry weight - dw) was found in S. colias and the lowest one (5 ng/g dw) in T. trachurus. In the muscle, the bisphenol with the highest concentration was BPE in S. colias (272 ng/g dw). Fish with microplastics had significantly higher concentrations of bisphenols than fish where no microplastics were found, suggesting a relation between MP and bisphenol contamination in fish. In all species, the concentration of bisphenols was correlated with higher MP intake. Regarding human food safety, the estimated daily intake (EDI), target hazard quotient (THQ) and hazard index (HI) of bisphenols were higher than those established by the European Food Safety Authority suggesting hazardous risk for human consumers. These findings highlight the need of more research on fish contamination by MP and associated chemicals and inherent human food safety risks. [ABSTRACT FROM AUTHOR]

Apparent digestibility coefficients (ADCs) of five commercially available insect larvae meals, H. illucens (HI and HId), T. molitor (TM and TMd) and a locust meal (LM), obtained from different producers, were assessed in European sea bass (Dicentrarchus labrax) juveniles. Each experimental diet was obtained by replacing 20% of a commercial-based diet used as reference (DREF), with 1% of chromic oxide added, by a test ingredient. Each diet was fed to quadruplicate groups of fish (initial weight: 33 ± 1 g) and, after an acclimatization period, daily collection of faeces was performed during 12 days. Dry matter ADC was highest in TM (85%) and lowest in LM (40%). Protein ADC was high in TMd (93%); intermediate in HId and TM (87 and 89%, respectively); and moderate in LM and HI (74 and 76%, respectively). Overall, the ingredient with highest digestible total essential amino acids (EAAs) content was TMd, followed by TM which was higher than HId; HI had a moderate amount of digestible EAAs, and LM had the lowest values. Fat ADC was highest for HId, TMd and TM (93%–95%). Energy and phosphorus ADC were highest in TMd (84% and 91%, respectively) and lowest in LM (53% and 27%, respectively). In conclusion, the high protein level, high protein digestibility and high amount of digestible EAAs of TM and TMd (> 89%) suggests that Tenebrio molitor larvae meals are the most promising protein sources tested for European sea bass, with potential to replace fishmeal without impairing nutrient digestibility. • Protein digestibility of TMd > TM ≥ HId>HI ≥ LM. • Dry matter and fat digestibilities were highest in TM. • The highest protein, P and energy ADCs were observed in TMd. • TMd content of digestible EAA was highest followed by TM and HId. • Digestible lysine and methionine of TMd, HI and HId meet D. labrax requirements. [ABSTRACT FROM AUTHOR]