The green seaweed Ulva: tomorrow's "wheat of the sea" in foods, feeds, nutrition, and biomaterials.

Ulva, a genus of green macroalgae commonly known as sea lettuce, has long been recognized for its nutritional benefits for food and feed. As the demand for sustainable food and feed sources continues to grow, so does the interest in alternative, plant-based protein sources. With its abundance along coastal waters and high protein content, Ulva spp. have emerged as promising candidates. While the use of Ulva in food and feed has its challenges, the utilization of Ulva in other industries, including in biomaterials, biostimulants, and biorefineries, has been growing. This review aims to provide a comprehensive overview of the current status, challenges and opportunities associated with using Ulva in food, feed, and beyond. Drawing on the expertise of leading researchers and industry professionals, it explores the latest knowledge on Ulva's nutritional value, processing methods, and potential benefits for human nutrition, aquaculture feeds, terrestrial feeds, biomaterials, biostimulants and biorefineries. In addition, it examines the economic feasibility of incorporating Ulva into aquafeed. Through its comprehensive and insightful analysis, including a critical review of the challenges and future research needs, this review will be a valuable resource for anyone interested in sustainable aquaculture and Ulva's role in food, feed, biomaterials, biostimulants and beyond.

Long-term regulation of fat sensing in rainbow trout (Oncorhynchus mykiss) fed a vegetable diet from the first feeding: focus on free fatty acid receptors and their signalling.

Taste plays a fundamental role in an animal's ability to detect nutrients and transmits key dietary information to the brain, which is crucial for its growth and survival. Providing alternative terrestrial ingredients early in feeding influences the growth of rainbow trout (RT, Oncorhynchus mykiss). Thus, the present study aimed to assess the influence, via long-term feeding (from the first feeding to 8 months), of alternative plant ingredients (V diet for vegetable diet v. C diet for a control diet) in RT on the mechanism of fat sensing at the gustatory level. After the feeding trial, we studied the pathways of the fat-sensing mechanism in tongue tissue and the integrated response in the brain. To this end, we analysed the expression pattern of free fatty acid receptors (ffar) 1 and 2, markers of calcium-signalling pathways (phospholipase Cß, Orai, Stim or Serca), the serotonin level (a key neurotransmitter in taste buds) and the expression pattern of appetite-regulating neuropeptides in the hypothalamus (central area of appetite regulation). The results revealed that the V diet modified the expression pattern of ffar1 and paralogs of ffar2 genes in tongue tissue, along with differential regulation of calcium-signalling pathways and a defect in serotonin level and brain turnover, without influencing neuropeptide expression. This study is the first to support that changes in feeding behaviour of RT fed a V diet could be due to the difference in nutrient sensing and a decrease in hedonic sensation. We revealed that RT have similar fat-detection mechanisms as mammals.

Insect meal in aquafeeds: A sustainable path to enhanced mucosal immunity in fish.

The mucosal surfaces of fish, including their intestines, gills, and skin, are constantly exposed to various environmental threats, such as water quality fluctuations, pollutants, and pathogens. However, various cells and microbiota closely associated with these surfaces work in tandem to create a functional protective barrier against these conditions. Recent research has shown that incorporating specific feed ingredients into fish diets can significantly boost their mucosal and general immune response. Among the various ingredients being investigated, insect meal has emerged as one of the most promising options, owing to its high protein content and immunomodulatory properties. By positively influencing the structure and function of mucosal surfaces, insect meal (IM) has the potential to enhance the overall immune status of fish. This review provides a comprehensive overview of the potential benefits of incorporating IM into aquafeed as a feed ingredient for augmenting the mucosal immune response of fish.

Insights into the functional properties of a natural free amino acid mix: Effect on growth performance, nutrient metabolism, and immune response in a carnivorous fish, Asian seabass (Lates calcarifer).

Dietary supplements containing a functional feed additive have been shown to be beneficial to fish and shellfish aquaculture. However, the functional properties of aquafeed formulations have rarely been reported in fish. This study aimed to investigate the effects of natural free amino acid mix (FAAM) supplementation as a functional solution on the growth performance and nutrient utilization in a carnivorous fish, Asian seabass (Lates calcarifer). Five isonitrogenous and isolipidic diets were prepared with graded supplementation levels of FAAM at 0 % (control group), 0.25 %, 0.50 %, 0.75 %, and 1.0 %, denoted as FAAM0, FAAM0.25, FAAM0.5, FAAM0.75, and FAAM1.0, respectively. The experimental fish were fed different dietary FAAM supplementations to apparent satiation twice daily for eight weeks. Significant improvements were observed in the growth performance of fish among the five groups (P < 0.05). Fish fed with FAAM0.75 displayed significantly increased activities of lysozyme, myeloperoxidase, catalase, and glutathione peroxidase (P < 0.05). The activities of digestive enzymes, including amylase, protease, and lipase, were enhanced by the supplementation of FAAM in the feed (P < 0.05), especially for the groups that contained more than 0.5 % FAAM in the feed. Furthermore, the morphological profile of the intestinal tract, including the mucosal fold height, width, thickness, and goblet cell, increased in fish fed with FAAM at 1.0 % (P < 0.05). Moreover, FAAM supplementation in diets not only modulated the expression of immune-related genes (glutathione peroxidase (GPx), complement (C)3, C4, and C-reactive protein) in the liver but also positively impacted the growth-ralated genes, including growth hormone (GH), GH receptor (GHR), insulin-like growth factor I (IGF-I), and IGF-II. In addition, the amounts of monounsaturated fatty acids (mainly oleic acid (C18:1n9c)) and polyunsaturated fatty acids-especially γ-linolenic acid (C18:3 n6) and α-linolenic acid (C18:3n3)-increased in fish fed with diets containing FAAMs (P < 0.05). Interestingly, the diets supplemented with FAAMs also had a positive effect on the economic indices in terms of revenue-to-cost ratios. These findings provide a scientific basis for the application of FAAMs as a functional solution that can be used in feed formulations for Asian seabass.

Effect of digestible protein on intermediate metabolism, hepatic enzyme activities, energy reserves, and growth performance of pacu (Piaractus mesopotamicus) in the finishing growth phase.

This study investigated the effect of different levels of digestible protein (DP) on blood metabolites, hepatic enzyme activity of glycolysis and amino acid metabolism, energy reserves, and the production characteristics of pacu (Piaractus mesopotamicus) during the finishing growth phase. Six semi purified and isoenergetic diets, containing 16.3, 20.1, 23.8, 27.2, 31.5, and 34.8% of balanced DP, provided with essential amino acid balance, were hand-fed to pacu (1100.0 ± 10.3 g, initial weight) three times daily for 7 weeks. The experiment consisted of six treatments, with three randomly arranged replicates (tanks) per treatment. The data obtained from this experiment were analyzed by one-way analysis of variance (ANOVA), and significant differences (p < 0.05) between treatments were determined using Tukey's test. Blood metabolites, except serum ammonia and the hepatic enzymes activities of glycolysis and amino acid metabolism, except hexokinase activity were affected (p < 0.05) by balanced DP. The energy reserve indices, except hepatic total lipid content, were also found associated (p < 0.05) with balanced DP. The test diets significantly (p < 0.05) affected growth performance parameters. Higher dietary proteins led to a greater energy uptake by fish from the protein in feed. Overall, fish fed the intermediate level (23.8%) of balanced DP with digestible energy of 17.95 MJ kg-1 showed better production traits and physio-biochemical health markers. This information could help nutritionists and farmers to develop nutritionally balanced and economically and environmentally sustainable aquafeed for promoting healthy and sustainable production of pacu in intensive culture systems.

Influence of dietary bitter orange peel powder on growth, body composition, blood parameters, gut morphometry, and thermal tolerance of Nile tilapia (Oreochromis niloticus).

The potential of bitter orange peel powder (BOPP) as a nutritional strategy for fish was investigated in Nile tilapia. A total of 120 juveniles with an average initial weight of 9.8 ± 0.7 g were divided into four groups, replicated three times, resulting in 12 experimental units (60 L each) at a stocking density of 1.63 g of fish per liter. Productive parameters, whole-body composition, blood biochemistry, erythroid morphometry, intestinal histology, and heat tolerance were assessed in the juveniles subjected to one of the following treatments: non-supplemented basal diet (control group); basal diet with BOPP at 10 g/kg (BOPP10 group); basal diet with BOPP at 20 g/kg (BOPP20 group); and basal diet with BOPP at 40 g/kg (BOPP40 group). The BOPP additive had a positive influence on Nile tilapia growth, as final weight and weight gain were greater in all BOPP-treated fish, despite the reduction in crude protein in BOPP10 and BOPP20 groups. Fish receiving BOPP40 had an increase in total lipids and showed the highest levels of triglycerides and total cholesterol. Villi development was greater in the tilapia given BOPP10. It may be concluded that BOPP presented the most promising results for Nile tilapia juveniles when used at 10 g/kg diet. Regarding the erythroid morphometry, there was a general increase in nuclear and cytoplasmic areas in BOPP-fed tilapia; this seems to be the first report on the direct impact of the inclusion of functional additives in fish diet upon such parameters. As concerns the thermal tolerance evaluated at the end of the feeding trial, no differences were registered among the experimental groups. Thus, BOPP represents a feasible alternative ingredient to be explored in fish nutrition, since orange peel is a natural low-cost source of essential nutrients and valuable bioactive compounds.

Effect of dietary gamma aminobutyric acid (GABA) modulated the growth performance, immune and antioxidant capacity, digestive enzymes, intestinal histology and gene expression of Nile tilapia (Oreochromisniloticus).

Dietary GABA plays an important role in a variety of physiological functions in animals, but this has been rarely reported in fish. This study investigated the effects of dietary supplementation with GABA on growth, serum antioxidant indicators, digestive enzyme activities, intestinal morphology, and the gene expression of Nile tilapia. Diets containing three different GABA concentrations, 0 (control), 200 mg/kg (GABA200), and 500 mg/kg (GABA500), were fed to Nile tilapia (6.97 ± 0.34 g) for 56 days. The present study found that increasing dietary GABA content could increase the fish growth performance including final body weight, weight gain, specific growth rate, average daily gain, protein efficiency ratio, and feed efficiency compared to the control diet. Interestingly, the feed conversion ratio was improved by dietary GABA supplementation. The antioxidant enzyme activities against ammonia stress of fish fed the GABA diets were significantly higher than the corresponding control group throughout the 96-h ammonia exposure. Moreover, significant increases in digestive enzyme activities including protease, amylase and lipase were found in fish fed the GABA diets. Intestinal morphology analysis revealed increased heights and widths of intestinal villi as well as thickness of the intestinal muscularis in fish fed the GABA diets compared to the control diet. The supplementation of diets with GABA significantly increased the expression level of immune- and growth-related genes. The above results indicate that dietary GABA can modulate the growth, improve their immune response and antioxidant status, gut health and morphology and gene expression of Nile tilapia. Therefore, GABA is a promising feed additive for Nile tilapia aquaculture.

Projecting global mariculture production and adaptation pathways under climate change.

The sustainability of global seafood supply to meet increasing demand is facing several challenges, including increasing consumption levels due to a growing human population, fisheries resources over-exploitation and climate change. Whilst growth in seafood production from capture fisheries is limited, global mariculture production is expanding. However, climate change poses risks to the potential seafood production from mariculture. Here, we apply a global mariculture production model that accounts for changing ocean conditions, suitable marine area for farming, fishmeal and fish oil production, farmed species dietary demand, farmed fish price and global seafood demand to project mariculture production under two climate and socio-economic scenarios. We include 85 farmed marine fish and mollusc species, representing about 70% of all mariculture production in 2015. Results show positive global mariculture production changes by the mid and end of the 21st century relative to the 2000s under the SSP1-2.6 scenario with an increase of 17%±5 and 33%±6, respectively. However, under the SSP5-8.5 scenario, an increase of 8%±5 is projected, with production peaking by mid-century and declining by 16%±5 towards the end of the 21st century. More than 25% of mariculture-producing nations are projected to lose 40%-90% of their current mariculture production potential under SSP5-8.5 by mid-century. Projected impacts are mainly due to the direct ocean warming effects on farmed species and suitable marine areas, and the indirect impacts of changing availability of forage fishes supplies to produce aquafeed. Fishmeal replacement with alternative protein can lower climate impacts on a subset of finfish production. However, such adaptation measures do not apply to regions dominated by non-feed-based farming (i.e. molluscs) and regions losing substantial marine areas suitable for mariculture. Our study highlights the importance of strong mitigation efforts and the need for different climate adaptation options tailored to the diversity of mariculture systems, to support climate-resilient mariculture development.

Recent advances in the application of microalgae and its derivatives for preservation, quality improvement, and shelf-life extension of seafood.

Seafood is a highly perishable food product due to microbiological, chemical, and enzymatic reactions, which are the principal causes of their rapid quality deterioration. Therefore, ever-increasing consumers' demand for high-quality seafood along with a negative perception of synthetic preservatives creates opportunities for natural preservatives such as microalgae extracts. They are potential alternatives to reduce microbial growth, increase oxidative stability, and protect the sensorial properties of seafood. Research has shown that the inclusion of microalgae extracts into the aquatic animal's diet could enhance their meat quality and increase production. This review focuses on the direct application of various microalgae extracts as seafood preservative, and their functional properties in seafood, such as antioxidant and antimicrobial activities. Besides, the potential nutritional application of microalgae extracts as an alternative in aqua-feed and their impact on seafood quality (indirect application) are also presented. The safety aspects and regulatory issues of products from microalgae are highlighted.

Optimum dietary sources and levels of selenium improve growth, antioxidant status, and disease resistance: re-evaluation in a farmed fish species, Nile tilapia (Oreochromis niloticus).

The objective of this study was to investigate the effects of sources and levels of selenium (Se) on juvenile Nile tilapia (Oreochromis niloticus). A completely randomized design involving a 2 × 3 factorial arrangement of treatments was used in this study. Organic Se (L-selenomethionine; SeMet) and inorganic Se (sodium selenite; Na2SeO3) were each added to the basal diet at 1, 3 and 5 mg Se/kg. The basal diet, without Se supplementation, was used as a control. There was a total of 7 experimental diets, and each was fed in triplicate to groups of fish with an initial average body weight of 13.5 g for 8 weeks. The results showed that growth performance was significantly affected by dietary sources and levels of Se (P < 0.05). Fish fed diets supplemented with SeMet of 1.0 mg Se/kg resulted in higher growth performance compared to basal diet (P < 0.05), but Na2SeO3 supplementation did not affect growth. The feed conversion ratio was significantly decreased as dietary sources of SeMet (P < 0.05). Interestingly, fish fed diets supplemented with both forms of Se had lower cholesterol levels than those fed the basal diet (P < 0.05). Moreover, dietary sources and levels of Se significantly increased (P < 0.05) the antioxidant enzyme activities such as lysozyme, catalase, myeloperoxidase, superoxide dismutase and glutathione peroxidase. Dietary sources and levels of Se significantly could enhance the Nile tilapia resistance against Streptococcusagalactiae infection (P < 0.05). Overall, it can be concluded that the inclusion level of 1.0 mg Se/kg of organic Se in the diet is suggested to be the optimal level for the growth performance and immune response of Nile tilapia. Therefore, dietary supplementation with Se is useful for improving growth, antioxidant status, immune response, and disease resistance.

Impacts of Aegle marmelos fruit extract as a medicinal herb on growth performance, antioxidant and immune responses, digestive enzymes, and disease resistance against Streptococcus agalactiae in Nile tilapia (Oreochromis niloticus).

An experiment was conducted to investigate the effects of Aegle marmelos fruit (AMF) extract on the growth performance, biochemical parameters, immune response, antioxidative capacity, and digestive enzyme activity of Nile tilapia (Oreochromis niloticus). Fish were fed a diet supplemented with AMF at concentrations of 0 (AMF0; control), 5 (AMF5), 10 (AMF10), 15 (AMF15), or 20 (AMF20) g/kg for 8 weeks. The results show that the final body weight, weight gain, specific growth rate, average daily gain, and feed conversion ratio were significantly higher in fish fed AMF15 and AMF20 compared to those fed the control diet (P < 0.05). Moreover, significant increases in antioxidant enzyme activities and non-specific immune responses were observed in groups fed AMF15 and AMF20. Interestingly, the level of cholesterol decreased with increasing AMF concentrations in the diet. As dietary AMF levels increased, digestive enzyme activities significantly improved. After the feeding trial, fish were injected intraperitoneally with Streptococcus agalactiae, and the 14-day cumulative mortality was calculated. A high survival rate after challenge with S. agalactiae was observed in all groups that received AMF-supplemented feed. Therefore, the present study suggests that supplementing the diet of Nile tilapia with AMF at a concentration of 20 g/kg could encourage their growth, improve their immunity and antioxidant status, and provide strong protection against S. agalactiae.

Seaweed Phenolics as Natural Antioxidants, Aquafeed Additives, Veterinary Treatments and Cross-Linkers for Microencapsulation.

Driven by consumer demand and government policies, synthetic additives in aquafeed require substitution with sustainable and natural alternatives. Seaweeds have been shown to be a sustainable marine source of novel bioactive phenolic compounds that can be used in food, animal and aqua feeds, or microencapsulation applications. For example, phlorotannins are a structurally unique polymeric phenolic group exclusively found in brown seaweed that act through multiple antioxidant mechanisms. Seaweed phenolics show high affinities for binding proteins via covalent and non-covalent bonds and can have specific bioactivities due to their structures and associated physicochemical properties. Their ability to act as protein cross-linkers means they can be used to enhance the rheological and mechanical properties of food-grade delivery systems, such as microencapsulation, which is a new area of investigation illustrating the versatility of seaweed phenolics. Here we review how seaweed phenolics can be used in a range of applications, with reference to their bioactivity and structural properties.

An overview on microalgae as renewable resources for meeting sustainable development goals.

The increased demands and dependence on depleted oil reserves, accompanied by global warming and climate change have driven the world to explore and develop new strategies for global sustainable development. Among sustainable biomass sources, microalgae represent a promising alternative to fossil fuel and can contribute to the achievement of important Sustainable Development Goals (SDGs). This article has reviewed the various applications of microalgal biomass that includes (i) the use in aquaculture and its sustainability; (ii) commercial value and emerging extraction strategies of carotenoids; (iii) biofuels from microalgae and their application in internal combustion engines; (iv) the use and reuse of water in microalgae cultivation; and (v) microalgae biotechnology as a key factor to assist SDGs. The future prospects and challenges on the microalgae circular bio economy, issues with regard to the scale-up and water demand in microalgae cultivation are also highlighted.

Surviving of production probiotic strains in a selected application form.

Research in probiotics for aquaculture is at an early stage of development and much work is still needed. Lactiplantibacilli belong to the microorganisms most frequently used to prepare the probiotics. The available information is inconclusive, since few experiments with sufficiently robust design have been conducted to permit critical evaluation. The development of probiotics applicable to commercial use in aquaculture is a multistep and multidisciplinary process requiring both empirical and fundamental research, full-scale trials, and an economic assessment of its use. The aim of the study was to prepare a probiotic aquafeed via excipients and subsequently to observe the survival of probiotic bacterial cells in the feed during the nine months storage period at a refrigerator (4 °C) or room temperature (22 °C). The strain Lactobacillus plantarum R2 Biocenol (CCM 8674) (according to the new taxonomy Lactiplantibacillus plantarum), potentially usable as a probiotic in aquaculture, was administered to prepare the aquafeed. Better survival of probiotic bacterial cells was recorded in a samples of pellets A (Aquatex 41 HMD) compared to the samples of probiotic pellets B (Inicio 918-2). Since oxidation of fatty acids in feed affects the nutritional quality of individual feed components, we assume that higher amounts of oil in feed B negatively affected the survival of probiotic bacterial cells. The highest numbers of viable probiotic bacteria cells were recorded at 4 °C storage of probiotic feed samples. The number of lactiplantibacilli dropped from 7.30 log10CFU . g-1 to 5.57 log10CFU . g-1 after the nine months storage period of feed samples A at 4 °C. Temperature is considered as a critical factor influencing probiotic viability and survival during storage period.

Potential use of macroalgae Gracilaria gracilis in diets for European seabass (Dicentrarchus labrax): Health benefits from a sustainable source.

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.

The influence of coconut oil on the growth, immune, and antioxidative responses and the intestinal digestive enzymes and histomorphometry features of Nile tilapia (Oreochromis niloticus).

The trials of finding non-conventional and alternative aquafeed ingredients are increasing. In this sense, this study evaluated the influence of coconut oil on the growth, feed utilization, immune, and antioxidative responses of Nile tilapia. Five test diets were formulated by mixing coconut oil with the other ingredients at 0, 1, 2, 3, and 4% of the total ration and presented for tilapia for 60 successive days. The final weight, SGR, weight gain (WG), and feed intake were superior in fish delivered 2% of coconut oil (P < 0.05). Concurrently, fish that received 2% coconut oil had lower FCR and higher PER than fish of the control and 4% groups (P < 0.05). Higher lipase activity was observed in fish of 2% and 3% levels than the remaining groups (P < 0.05). Besides, the amylase and protease activities of fish in 1%, 2%, and 3% groups were higher than the 0% level (P < 0.05). The total blood cholesterol, RBCs, and PCV showed higher values in Nile tilapia fed 2% and 3% coconut oil (P < 0.05). The lysozyme and phagocytic activities were higher in fish fed 2% and 3% levels than the control (P < 0.05), while the phagocytic index in 2% and 3% levels was higher than 0% and 4% levels. Furthermore, SOD and CAT were higher in fish fed 1%, 2%, and 3% than fish fed 0% and 4% levels while GSH was higher in fish of 1%, 2%, and 3% than fish fed 0% level (P < 0.05). However, the MDA level was markedly lower in fish fed 25, 3%, and 4% coconut oil than the 0% level (P < 0.05). The intestine's histological structure in all groups appeared normal, forming of intestinal villi projecting from the intestinal wall. Also, the structure of the hepatopancreas had a normal architecture in all groups. To sum up, the inclusion of coconut oil at 2 to 3% is recommended as a replacer for fish oil in Nile tilapia diets.

Effects of dietary multi-strain probiotics supplementation in a low fishmeal diet on growth performance, nutrient utilization, proximate composition, immune parameters, and gut microbiota of juvenile olive flounder (Paralichthys olivaceus).

A 12-week feeding trial was conducted to evaluate the effects of multi-strain probiotics (MSP) in a low fish meal (FM) diet on overall performance, gut microbiota, selected non-specific immune responses and antioxidant enzyme activities of olive flounder (Paralichthys olivaceus) juveniles. A total of 225 healthy olive flounders (initial mean body weight, 13.5 ±â€¯0.01 g) were randomly separated into 3 groups of 75 fish, each group having three replicates of 25 fish; first group was fed with a FM-based control diet (Con), 2nd group was fed with a low-FM diet containing a blend of plant and animal protein meals replacing 30% of the FM protein (FM30), and 3rd group was fed with the FM30 diet supplemented with 108-109 CFU kg-1 of the MSP (Pro). With the exception of lipid retention, which was significantly lower in fish fed the FM30 diet compared to the other two treatments, no other statistically significant differences were recorded with respect to any of the other growth and nutrient utilization parameters. Myeloperoxidase and lysozyme activities of fish fed the Pro diet were much higher and significantly different than those of fish fed the FM30 diet. Glutathione peroxidase activity was significantly higher in Pro- than in Con-fed fish, which, in turn, was significantly higher than FM30-fed fish. Expression of immune-related genes including IL-1ß, IL-6, and TNF-α was markedly upregulated in livers of the fish fed Pro diet compared to those fed the Con and FM30 diets. Furthermore, supplementation of MSP in FM30 diet enriched the Lactobacillus abundance in the fish gut as well as predictive gene functions in relation to lipid and carbohydrate metabolisms. These data suggested that the MSP could reduce the potential adverse effects of the low-FM diet and might be used as a healthy immunostimulant for olive flounder.

A Multi-screening Evaluation of the Nutritional and Nutraceutical Potential of the Mediterranean Jellyfish Pelagia noctiluca.

The phylum Cnidaria is one of the most important contributors in providing abundance of bio- and chemodiversity. In this study, a comprehensive chemical investigation on the nutritional and nutraceutical properties of Mediterranean jellyfish Pelagia noctiluca was carried out. Also, compositional differences between male and female organisms, as well as between their main anatomical parts, namely bell and oral arms, were explored in an attempt to select the best potential sources of nutrients and/or nutraceuticals from jellyfish. With the exception of higher energy densities and total phenolic contents observed in females than males, no statistically significant differences related to the specimen's sex were highlighted for the other compound classes. Rather, the distribution of the investigated chemical classes varied depending on the jellyfish's body parts. In fact, crude proteins were more abundant in oral arms than bells; saturated fatty acids were more concentrated in bells than oral arms, whereas polyunsaturated fatty acids were distributed in the exact opposite way. On the other hand, major elements and trace elements demonstrated an opposite behavior, being the latter most accumulated in oral arms than bells. Additionally, important nutraceuticals, such as eicosapentaenoic and docosahexaenoic acids, and antioxidant minerals, were determined. Overall, obtained data suggest the potential employment of the Mediterranean P. noctiluca for the development of natural aquafeed and food supplements.

Coping with exposure to hypoxia: modifications in stress parameters in gilthead seabream (Sparus aurata) fed spirulina (Arthrospira platensis) and brewer's yeast (Saccharomyces cerevisiae).

This study aimed to investigate the stress response of Sparus aurata specimens fed with nutraceutical aquafeed brewer's yeast (Saccharomyces cerevisiae) and spirulina (Arthrospira platensis). For that purpose, 96 (169.0 ± 2.8 g) animals were distributed randomly in 12 tanks (8 fish per tank, 4 replicates) and divided in 3 groups (D1, casein/gelatin, control; D2, brewer's yeast; D3, spirulina) and fed for 30 days. At the end of this period, fish from two replicates of each experimental diet were submitted to air exposure for 60 s while the fish from the other two replicates were maintained undisturbed (control). Afterwards, samples of blood, skin mucus, and head kidney were collected. The results revealed that after air exposure, cortisol, and glucose levels increased in the groups fed D1 (18.5 ± 2.6 mg/mL; 7.3 ± 0.6 mmol/L, respectively) and D2 (20.0 ± 6.2 mg/mL; 7.7 ± 0.6 mmol/L), but glucose not increased in fish fed D3 (13.7 ± 2.6 mg/mL; 5.5 ± 0.3 mmol/L). Lactate levels increased in all stressed groups, but in D1, its levels were significantly higher. After stress procedure, immunoglobulin M (IgM) levels in mucus increased only in fish fed D3 (0.1901 ± 0.0126 U/mL). Furthermore, there was a reduction in the expression of some genes involved in stress response (coxIV, prdx3, csfl-r, ucp1, and sod in fish fed D2 and D3). csf1 decreased only in stressed fish fed D2. However, cat increased in fish fed with D3. In summary, these findings points to the beneficial effects of spirulina and brewer's yeast to improve stress resistance in aquaculture practices of gilthead seabream.

Dietary aquaculture by-product hydrolysates: impact on the transcriptomic response of the intestinal mucosa of European seabass (Dicentrarchus labrax) fed low fish meal diets.

BACKGROUND: Aquaculture production is expected to double by 2030, and demands for aquafeeds and raw materials are expected to increase accordingly. Sustainable growth of aquaculture will require the development of highly nutritive and functional raw materials to efficiently replace fish meal. Enzymatic hydrolysis of marine and aquaculture raw materials could bring new functionalities to finished products. The aim of this study was to determine the zootechnical and transcriptomic performances of protein hydrolysates of different origins (tilapia, shrimp, and a combination of the two) in European seabass (Dicentrarchux labrax) fed a low fish meal diet (5%), for 65 days. RESULTS: Results were compared to a positive control fed with 20% of fish meal. Growth performances, anterior intestine histological organization and transcriptomic responses were monitored and analyzed. Dietary inclusion of protein hydrolysates in the low fish meal diet restored similar growth performances to those of the positive control. Inclusion of dietary shrimp hydrolysate resulted in larger villi and more goblet cells, even better than the positive control. Transcriptomic analysis of the anterior intestine showed that dietary hydrolysate inclusion restored a pattern of intestinal gene expression very close to the pattern of the positive control. However, as compared to the low fish meal diet and depending on their origin, the different hydrolysates did not modulate metabolic pathways in the same way. Dietary shrimp hydrolysate inclusion modulated more metabolic pathways related to immunity, while nutritional metabolism was more impacted by dietary tilapia hydrolysate. Interestingly, the combination of the two hydrolysates enhanced the benefits of hydrolysate inclusion in diets: more genes and metabolic pathways were regulated by the combined hydrolysates than by each hydrolysate tested independently. CONCLUSIONS: Protein hydrolysates manufactured from aquaculture by-products are promising candidates to help replace fish meal in aquaculture feeds without disrupting animal metabolism and performances.