Reduction of Anisakis Allergenicity in Gilthead Seabream (Sparus aurata) Fed with Fish Viscera Silage-Based Diets

Simple SummaryDietary hydroxy-selenomethionine (OH-SeMet) reduces oxidative stress and modulates immune response against bacterial infection in fish. However, the effect of OH-SeMet on essential fatty acids with a high oxidation risk or on the response against viral infection has not been sufficiently studied. This study aimed to assess the impact of dietary OH-SeMet supplementation on whole-body fatty acid profiles and response against viral infection. Gilthead seabream (Sparus aurata) juveniles were fed for 91 days with three experimental diets, a control diet without Se supplementation (0.29 mg Se kg diet−1) and two diets supplemented with OH-SeMet (0.52 and 0.79 mg Se kg diet−1). Afterwards, a crowding stress challenge and an anti-viral response challenge were conducted. Selenium (Se), proximate and fatty acid composition of diets and body tissues were analyzed, as well as plasma cortisol and the antiviral response protein Mx gene expression. Elevation in dietary Se (from 0.29 to 0.79 mg kg−1) proportionally raised Se contents in body tissues (from 0.79 to 1.35 mg kg−1), increased lipid contents in whole body (from 9.46 to 10.83%), and promoted the retention and synthesis of n-3 polyunsaturated fatty acids (from 44.59 to 72.91%), reducing monounsaturated (from 44.07 to 42.00 %) and saturated fatty acids (29.77 to 26.92 %) contents in whole-body lipids. Additionally, it increased 2 h post-stress plasma cortisol levels and after poly I:C injection up-regulated Mx and other immune response related genes, showing, for the first time in gilthead seabream, the importance of dietary Se levels on antiviral defense.The supplementation of fish diets with OH-SeMet reduces oxidative stress and modulates immune response against bacterial infection. However, despite the importance of essential polyunsaturated fatty acids in fish nutrition and their high risk of oxidation, the potential protective effect of OH-SeMet on these essential fatty acids has not been studied in detail. Moreover, while viral infection is very relevant in seabream production, no studies have focused the Se effects against viral infection. The aim of the present study was to assess the impact of dietary supplementation with OH-SeMet on gilthead seabream fatty acid profiles, growth performance and response against viral infection. Gilthead seabream juveniles (21.73 ± 0.27 g) were fed for 91 days with three experimental diets, a control diet without supplementation of Se (0.29 mg Se kg diet−1) and two diets supplemented with OH-SeMet (0.52 and 0.79 mg Se kg diet−1). A crowding stress test was performed at week 7 and an anti-viral response challenge were conducted at the end of the feeding trial. Selenium, proximate and fatty acid composition of diets and body tissues were analyzed. Although fish growth was not affected, elevation in dietary Se proportionally raised Se content in body tissues, increased lipid content in the whole body and promoted retention and synthesis of n-3 polyunsaturated fatty acids. Specifically, a net production of DHA was observed in those fish fed diets with a higher Se content. Additionally, both monounsaturated and saturated fatty acids were significantly reduced by the increase in dietary Se. Despite the elevation of dietary Se to 0.79 mg kg−1 not affecting basal cortisol levels, 2 h post-stress plasma cortisol levels were markedly increased. Finally, at 24 h post-stimulation, dietary OH-SeMet supplementation significantly increased the expression of the antiviral response myxovirus protein gene, showing, for the first time in gilthead seabream, the importance of dietary Se levels on antiviral defense.

Effect of water temperature and dietary starch on growth and metabolic utilization of diets in gilthead sea bream ( Sparus aurata) juveniles

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The total substitution of fishmeal (FM) and fish oil (FO) with sustainable feed ingredients, while maintaining acceptable growth performances and fish composition, is a challenge. Mussels have a high protein content, with essential amino acid and fatty acid (FA) profiles similar to those of FM. This study aimed to assess the potential to rear gilthead seabream (Sparus aurata) on a plant-based feed (without FM and FO) to which mussels were added. Subsequent effects on growth performance, protein content, and FA concentrations were studied. Juvenile gilthead seabream were reared for 46 days in water temperature of 21°C, in a recirculated aquaculture system composed of three fish tanks, each corresponding to one treatment: in the FMFO treatment, 342 fish were fed a commercial feed that contained FM and FO; in the plant-based feed (PBF) treatment, 345 fish were fed an experimental feed that contained only plant-based ingredients; in the mussel feed (MF) treatment, 342 fish were fed the feed from PBF supplemented with fresh mussel flesh from which the shells had been removed. Fish weighed a mean of 6.7 ± 1.3 g at stocking in each treatment. At harvest, the mean weight of fish from FMFO and MF were significantly different (23.1 ± 4.3 and 23.1 ± 5.2 g, respectively) than that from PBF (15.5 ± 3.6 g) (p < .05). Compared to the feed from FMFO, the feed from PBF decreased the percentages of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and saturated FA (14:0, 16:0) in fish, but increased those of 18:1, 18:2 n-6 and 18:3 n-3 FA. Compared to the feed from PBF, the feed from MF increased the EPA+DHA concentration in fish by 21%. Thus, adding fresh mussels to a plant-based feed yielded similar growth performances and survival rate as a commercial feed. It also improved the FA composition of fish compared to that of fish fed a plant-based feed.

Dietary arginine surplus does not improve intestinal nutrient absorption capacity, amino acid metabolism and oxidative status of gilthead sea bream (Sparus aurata) juveniles

Effects of black soldier fly larvae oil on lipid metabolism, liver fatty acid composition, and plasma metabolite profiles in gilthead seabream juveniles.

The effect of dietary carbohydrate complexity on growth, feed utilization and activity of selected key liver enzymes of intermediary metabolism were studied in gilthead sea bream juveniles. Four isonitrogenous (50% crude protein) and isolipidic (16% crude lipids) diets were formulated to contain 20% of pregelatinized maize starch, dextrin, maltose or glucose. Triplicate groups of fish (117g initial weight) were fed each diet to near satiation during 6weeks. No effect of dietary carbohydrate on growth was noticed. Feed efficiency was lower in fish fed the glucose diet than the maltose and dextrin diets. The lowest protein efficiency ratio was observed in fish fed the glucose diet. Six hours after feeding, glycemia was higher in fish fed the glucose diet than the maltose and starch diets. Liver glycogen content was unaffected by dietary carbohydrate complexity. Hepatic glucokinase (GK) activity was higher in fish fed the glucose and the maltose diets, while higher pyruvate kinase (PK) activity was recorded in fish fed the glucose diet than in fish fed the starch diet. Fructose-1,6-bisphosphatase (FBPase) and glucose-6-phosphate dehydrogenase (G6PD) activities were higher in fish fed the starch diet compared to dextrin and glucose diets. Data suggest that dietary glucose and maltose are more effective than complex carbohydrates in enhancing liver glycolytic activity. Dietary glucose also seems to be more effective than starch in depressing liver gluconeogenic and lipogenic activities. Overall, dietary maltose, dextrin or starch was better utilized than glucose as energy source by gilthead sea bream juveniles.

A nutritional strategy to promote gilthead seabream performance under low temperatures

Effects of dietary use of two lipid extracts from the microalga Nannochloropsis gaditana (Lubián, 1982) alone and in combination on growth and muscle composition in juvenile gilthead seabream, Sparus aurata

Growth performance, feed utilization and non-specific immune response of gilthead sea bream (Sparus aurata L.) fed graded levels of a bioprocessed soybean meal

The expansion of aquaculture and the rising cost of fishmeal have driven research into fish gut health and the replacement of marine-derived ingredients with alternative protein sources, within sustainable strategies aligned with the Blue Transformation. In this sense, the objective of this study was to evaluate the effect of including a functional ingredient based on hydrolyzed microalgae and grape marc extracts in feeds with high proportion of plant protein sources on growth, muscle composition, oxidative status, intestinal microbiota, and digestive functionality in gilthead seabream juveniles ( Sparus aurata ). Three experimental diets were formulated, all isoproteic (47%) and isolipidic (18%), namely: CT (control diet - a diet mimicking the commercial aquafeeds used for this species based on 20% fishmeal); PP (a plant-based diet replacing 60% of fishmeal with hydrolyzed vegetable protein); and PP-GG (the same PP diet supplemented with 2% of the microalgal-grape marc based nutraceutical, LB-Green Grape ). Results indicated a trend for improved growth performance and FCR in fish fed the PP-GG diet compared to PP group, although differences were not statistically significant. The inclusion of plant protein ingredients reduced muscle protein content, however, supplementation with microalgae and grape marc extract in the PP-GG diet partially mitigates this loss. Fishmeal replacement with vegetable proteins also affected lipid composition, with higher mono-unsaturated fatty acid content and increased poly-unsaturated fatty acid retention in PP and PP-GG groups. Additionally, PP diet posed an oxidative challenge, evidenced by higher lipid peroxidation, while this was significantly reduced in the PP-GG group, confirming the antioxidant effect of the nutraceutical ingredient. Digestive enzyme activities significantly increased in pancreatic enzymes of PP-GG group. Finally, although no significant differences in intestinal microbiota composition were observed, PP group showed increased bacterial diversity. In conclusion, dietary fortification with the nutraceutical based on microalgae and grape marc extracts improved growth, reduced oxidative damage, and enhanced digestive capacity in gilthead seabream juveniles, highlighting its potential as a nutritional strategy for sustainable aquaculture.

The efficacy of using cottonseed oil (CSO) as a fish oil (FO) substitute in gilthead seabream (Sparus aurata) juveniles feed was evaluated. Fish (BWi 4.0 ± 2.9 g) were fed one of four isoproteic (~48% CP) and isolipidic (~18% L) diets for 9 weeks. Added oil was either FO (control diet, CTRL) or CSO, replacing 50% (CSO50 diet), 60% (CSO60 diet) and 70% (CSO70 diet) of dietary FO. Results indicated that FO replacement by CSO up to 60% level had no detrimental effects on growth or nutritive utilization and composition in fish muscles. Higher CSO intake (CSO70 diet, 56 g kg−1) led to a 16% reduction in weight gain, 14% in feed utilization (FCR) and 57% in muscle n-3 long-chain polyunsaturated fatty acids (lc PUFA) as compared with CTRL and to abundant accumulation of lipid within the hepatocytes. Use of CSO altered fatty acid (FA) profiles of muscle and liver. Data suggested utilization of linoleic acid (LOA) by fish and retain of docosahexaenoic acid (DHA) in muscles. Therefore, limits of CSO inclusion as the main source of supplementary dietary lipid, with no negative effects on fish performance or nutritive composition and utilization in muscles, are: 40–48 g kg−1 feed for gilthead seabream juveniles.

Poultry by-product meal as an alternative to fish meal in the juvenile gilthead seabream (Sparus aurata) diet

This study investigated the effects of replacement of fish meal (FM) with poultry by-product meal (PBM) at 55%, 65% and 75% on growth performance and amino acid metabolism of juvenile gilthead seabream (Sparus aurata) with an initial weight of 35.01±0.11 g for 120 days. The study also evaluated protein and amino acid digestibility to determine their influence on protein metabolism in juvenile seabream. The results indicated that partial replacement of FM with PBM in diets of juvenile gilthead seabream is feasible up to 65% without compromising their growth performance, feed consumption and digestibility (P&gt;0.05). Additionally, hepatosomatic (HSI) showed no significant differences between all groups (P&gt;0.05). The viscerosomatic index (VSI) level was at the highest value, whereas the condition factor (K) was at the lowest value in CTRL (P&lt;0.05). The highest feed conversion ratio (FCR) value was in the 75PBM group (P&lt;0.05). However, there was no statistically significant difference between CTRL and the other PBM groups (P&gt;0.05). Similarly, feed intake and whole-body protein content did not significantly differ among dietary groups (P&gt;0.05). The protein efficiency ratio (PER) values suggest that replacing FM with PBM (up to 65%) in diets of juvenile gilthead seabream is effective and produces diets with high-quality proteins and digestibility coefficients comparable to those of the control group (P&gt;0.05). Additionally, amino acid profiles of juvenile gilthead seabream fed with diets containing up to 75% PBM showed no deficiencies in essential amino acids. Nevertheless, we can suggest that 75% PBM substitution for FM can be used in the diets of gilthead seabream, although it causes a slight decrease in growth, FCR and protein digestibility. These results suggest that partial replacement of FM with PBM can be a viable strategy for feeding juvenile gilthead seabream, offering a sustainable advantageous alternative.

This work aimed to evaluate the digestibility of defattedHermetia illucens larvae meal (HM), and its effects as fishmeal (FM) replacement on growth performance, feed and nutrient utilisation, and whole-body composition of gilthead seabream (Sparus aurata) juveniles. To assess apparent digestibility coefficients (ADC) of defatted HM, a reference-diet (43% crude protein (CP); 17% crude lipid (CL)) and a test-diet, in which 30% of the reference diet was replaced with defatted HM, were formulated. To assess the effect of dietary FM replacement, four isonitrogenous (43% CP) and isolipid (18% CL) diets were formulated to include defatted HM at 0 (HM0), 15 (HM15), 30 (HM30), and 45% (HM45), replacing FM at 0, 22, 60, and 100%, respectively. Triplicate groups of fish (initial body weight of 32 g) were randomly assigned to the experimental diets and the growth trial lasted for 67 days. The digestibility trials were conducted in a digestibility system, and each diet was tested in triplicate. Protein, lipid, and energy digestibility of defatted HM were high (&gt;74%). Replacement of FM by defatted HM did not compromise the ADC of protein and lipid, while ADC of dry matter and energy increased. Complete dietary replacement of FM by defatted HM had no negative effects on growth performance, feed efficiency, whole-body composition, and protein utilisation of gilthead seabream juveniles, establishing the potential of defatted HM as an alternative ingredient for aquafeeds.