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The present study investigated the effects of nutritional programming through parental feeding on offspring performance and expression of selected genes related to stress resistance in a marine teleost. Gilthead seabream broodstock were fed diets containing various fish oil (FO)/vegetable oil ratios to determine their effects on offspring performance along embryogenesis, larval development and juvenile on-growing periods. Increased substitution of dietary FO by linseed oil (LO) up to 80 % LO significantly reduced the total number of eggs produced by kg per female per spawn. Moreover, at 30 d after hatching, parental feeding with increasing LO up to 80 % led to up-regulation of the fatty acyl desaturase 2 gene (fads2) that was correlated with the increase in conversion rates of related PUFA. Besides, cyclo-oxygenase 2 (cox2) and TNF-α (tnf-α) gene expression was also up-regulated by the increase in LO in broodstock diets up to 60 or 80 %, respectively. When 4-month-old offspring were challenged with diets having different levels of FO, the lowest growth was found in juveniles from broodstock fed 100 % FO. An increase in LO levels in the broodstock diet up to 60LO raised LC-PUFA levels in the juveniles, regardless of the juvenile’s diet. The results showed that it is possible to nutritionally programme gilthead seabream offspring through the modification of the fatty acid profiles of parental diets to improve the growth performance of juveniles fed low FO diets, inducing long-term changes in PUFA metabolism with up-regulation offads2expression. The present study provided the first pieces of evidence of the up-regulation of immune system-related genes in the offspring of parents fed increased FO replacement by LO.

Hydroxyproline (L-Hyp) is amply present in fishmeal but limited in plant-protein sources. This study was conducted to evaluate the effects of supplementation with dietary L-Hyp on the distribution of collagen types in the muscle, and on the texture, survival rate, growth rate, feed utilization, body composition as well as the expression of the gene that encodes the pro-alpha2 chains of type I collagen (Col Iα2) of large European sea bass (initial body weight 609.21 ± 75.39 g) from high plant-protein diets. Four isoproteic (42 % crude protein) and isolipidic (20 % crude lipid) experimental diets were formulated adding 0.6 (HL diet), 1.2 (HM diet), and 2% (HH diet) L-Hyp, respectively. Three periods of feeding of 45, 99 and 143 days were studied. L-Hyp supplementation at 1.2 % and 2 % significantly improved specific growth rate (SGR) and feed conversion ratio (FCR). In the white muscle, type I, IV collagen and trichromic stain were significantly higher in HH feed than the control diet. In the red muscle, only type I collagen was higher. HH diet, also increases Col Iα2 mRNA levels in muscle significantly. It can be concluded that the addition of crystalline l-Hyp at 1.2 % or 2 % in high plant-protein diets indicates positive effects on growth performance of adult European sea bass and increase in muscle total collagen deposition. info:eu-repo/semantics/publishedVersion

Modern aquaculture feeds tend to contain lower levels of fish based ingredients, while increasing the content of plant ingredients. However, this may alter the vitamin profile of the feeds, leading to unbalanced vitamin supply. Requirements for several vitamins have been established for species such as carps and salmonids, but adequate levels for gilthead sea bream are yet unknown. Vitamin D is mainly involved in Ca homeostasis by regulating Ca uptake and liberation from bone intervening in bone remodeling. Fish are unable to synthesize vitamin D and so require absorbing it directly from the diet, thus, it is considered essential for fish. A practical plant-based diet containing 10% fish meal and 6% fish oil containing five levels of vitamin D3 (0.15, 0.43, 0.50, 0.55 and 0.65 mg kg− 1 or 5.8, 17.0, 20.0, 22.0 and 26.0 IU g− 1 ) were formulated to identify the optimum levels for gilthead seabream juveniles. Feeding juveniles of gilthead seabream with a range of vitamin D3 levels between 5.8 and 26.0 IU g− 1 for 70 days did not markedly alter growth. Increase dietary vitamin D3 significantly raised the liver contents in vitamin D3 in a dose-dependent manner following a potential regression. Increased dietary vitamin D3 levels up to 11.6 IU g− 1 may reduce the incidence of skeletal anomalies, particularly caudal and maxillary anomalies, whereas further elevation of dietary vitamin D3 levels increased the concentration of vitamin D3 in liver as well as skeletal anomalies in association to the up-regulation of alp and bmp2 gene expression. The occurrence of myocarditis signs in fish fed vitamin D3 levels of 20.0 IU g− 1 or more denote the toxic effects of these dietary levels. These results, together with the increased occurrence of skeletal anomalies in seabream fed the highest dietary vitamin D3 levels, suggest initial signs of hypervitaminosis D. Thus, the recommended level for vitamin D3 for gilthead seabream juveniles fed diets containing high levels of plant ingredients was suggested to be 11.6 IU g− 1.

The present work investigated how the combination of poultry oil with microalgae oils, rich in eicosapentaenoic acid and docosahexaenoic acid (ED diets) or n-6 docosapentaenoic acid and n-3 docosahexaenoic acid (DD diets) modulates hepatic lipid metabolism in gilthead sea bream juveniles. Diets were tested using two different fishmeal contents (15% and 7.5%) and compared against a fish oil-based diet (CTRL) and two negative control diets based on poultry oil as lipid source (PO diets). After 74 days of feeding, sea bream fed 15% FM ED or DD diets showed similar daily growth index to those fed CTRL, while those fed PO diets caused reduced growth. Fish livers reflected the highest contents in n-3 long-chain polyunsaturated fatty acids when fed CTRL, ED or DD diets, which down-regulated fas, scd-1a, fads2, lpl and cpt1, reducing hepatic lipid accumulation and hepatocytes size. In contrast, fish fed PO diets showed the lowest deposition of n-3 long-chain polyunsaturated fatty acids and the highest oleic acid in liver, leading with the highest hepatosomatic index due to increased liver lipids. Therefore, these fish revealed a severe hepatic steatosis associated with an increased expression of lipogenesis-related genes, particularly fas, lpl and sbrep1. Furthermore, PO diets seemed to activate desaturation pathways in fish livers, reflected by the highest accumulation of fatty acids that are products from desaturases and the highest fads2 and scd-1a expressions. The reduction of the dietary fishmeal content to 7.5% lowered fish growth, although hepatic lipid metabolism seemed to be more affected by FO replacement than FM replacement. Combining microalgae with poultry oil could be an alternative lipid and essential fatty acid source to fish oil in marine fish diets.

Simple Summary The present study was on the gene expression of a rate-limiting enzyme in long chain polyunsaturated fatty acids (LC-PUFAs), fatty acyl desaturase 2 (fads2), throughout the embryonic development of a gilthead sea bream. The results showed a maternal transfer of fads2 mRNA to the developing oocyte. The embryonic fads2 expression might start after the neurula stage. No effect was found in fads2 expression in developing eggs from broodstock fed with a diet rich in rapeseed oil or fish oil. The present study provides information on the change of LC-PUFA biosynthesis during embryogenesis. Abstract Previous studies have shown that it is possible to increase the ability of marine fish to produce long-chain polyunsaturated fatty acid from their 18C precursors by nutritional programming or using broodstock with a higher fatty acyl desaturase 2 (fads2) expression. However, those studies failed to show the effect of these interventions on the expression of the fads2 gene in the developing egg. Moreover, there were no studies on the temporal expression of the fads2 during ontogeny in the gilthead sea bream (Sparus aurata). In order to determine the changes in expression of fads2 during ontogeny, gilthead sea bream broodstock with a high (HRO) or low (LRO) fads2 expression fed a diet previously used for nutritional programming, or a fish oil-based diet (LFO) were allowed to spawn. The samples were taken at the stages of spawning, morula, high blastula, gastrula, neurula, heart beating, hatch and 3 day-old first exogenous feeding larvae to determine fads2 expression throughout embryonic development. The results showed the presence of fads2 mRNA in the just spawned egg, denoting the maternal mRNA transfer to the developing oocyte. Later, fads2 expression increased after the neurula, from heart beating until 3-day-old larvae, denoting the transition from maternal to embryonic gene expression. In addition, the eggs obtained from broodstock with high fads2 expression showed a high docosahexaenoic acid content, which correlated with the downregulation of the fads2 expression found in the developing embryo and larvae. Finally, feeding with the nutritional programming diet with the partial replacement of fish oil by rapeseed oil did not affect the long chain polyunsaturated fatty acid (LC-PUFA) contents nor fads2 expression in the gilthead sea bream developing eggs.

The principle aim of this study is to elucidate the relationship between the fatty acid desaturase 2 gene (fads2) expression pattern in peripheral blood cells (PBCs) and liver of gilthead seabream (GSB), Sparus aurata broodstock in order to determine the possible use of fads2 expression as a potential biomarker for the selection of broodstock. This selection could be utilized for breeding programs aiming to improve reproduction, health, and nutritional status. Passive Integrated Transponder (PIT)-tagged GSB broodstock (Male-1.22 &plusmn, 0.20 kg, 44.8 &plusmn, 2 cm and female-2.36 &plusmn, 0.64 kg, 55.1 cm) were fed a diet containing low levels of fish meal and fish oil (EPA 2.5, DHA 1.7 and n-3 LC-PUFA 4.6% TFA) for one month. After the feeding period, fads2 expression in PBCs and liver of both male and female broodstock were highly significantly correlated (r = 0.89, p &lt, 0.001). Additionally, in male broodstock, liver fads2 expression was significantly correlated (p &lt, 0.05) to liver contents in 16:0 (r = 0.95, p = 0.04) and total saturates (r = 0.97, p = 0.03) as well as to 20:3n&ndash, 6/20:2n&ndash, 6 (r = 0.98, p = 0.02) a Fads2 product/precursor ratio. Overall, we found a positive and significant correlation between fads2 expression levels in the PBCs and liver of GSB broodstock. PBCs fads2 expression levels indicate a strong potential for utilization as a non-invasive method to select animals having increased fatty acid bioconversion capability, better able to deal with diets free of fish meal and fish oil.

The negative effects of oxidative damage on larval development, growth and survival are among the factors markedly affecting marine fish larvae production success. Whereas α-tocopherol (vit E) and l -ascorbic acid (vit C) are strong antioxidants, the potential antioxidant role of taurine (Tau) in fish diets and its relation with other antioxidant nutrients needs further clarification. The present study aimed to determine the potential interactions between the dietary levels of vit E plus vit C and Tau on survival, growth, bone development and oxidative metabolism in gilthead seabream larvae. Six micro-bound diets containing two levels of Tau combined with three levels of vit E plus vit C were manually fed 24 times/day to 16 dph larvae for 15 days. Elevation of dietary vit E and vit C over 3000 mg/kg, led to unbalanced body vit C/vit E ratio and up-regulation of genes coding for antioxidant enzymes, the highest incidence of bone anomalies and the lowest larval survival. Increase in dietary vit C + vit E up to 1800 mg/kg, down-regulated GPX expression, up-regulated OC expression and reduced maxillary bone anomalies. Increase in dietary Tau up to 7.1 g/kg significantly improved larval growth, down-regulated antioxidant enzyme genes and reduced the incidence of bone anomalies. Moreover, the pro-oxidative effects of the high supplementation of vit C and E where mitigated by increase in dietary Tau levels. Finally, increase in dietary vit E, vit C and Tau up to 1783 mg/kg, 1921 mg/kg and 7 g/kg lead to the highest larval survival and growth, the highest OC gene expression and the lowest incidence of bone anomalies, including lordosis, kyphosis, branchiostegal and maxillary bones anomalies.

Nutrition during periconception and early development can modulate metabolic routes to prepare the offspring for adverse conditions through a process known as nutritional programming. In gilthead sea bream, replacement of fish oil (FO) with linseed oil (LO) in broodstock diets improves growth in the 4-month-old offspring challenged with low-FO and low-fishmeal (FM) diets for 1 month. The present study further investigated the effects of broodstock feeding on the same offspring when they were 16 months old and were challenged for a second time with the low-FM and low-FO diet for 2 months. The results showed that replacement of parental moderate-FO feeding with LO, combined with juvenile feeding at 4 months old with low-FM and low-FO diets, significantly (Pα-linolenic acid and linoleic acid in broodstock diets lead to a significant down-regulation of hepatic lipoprotein lipase (PPn-3, 18 : 3n-6, 20 : 5n-3, 22 : 6n-3 and 22 : 5n-6. Thus, this study demonstrated the long-term nutritional programming of gilthead sea bream through broodstock feeding, the effect of feeding a ‘reminder’ diet during juvenile stages to improve utilisation of low-FM/FO diets and fish growth as well as the regulation of gene expression along the fish’s life-cycle.

Environmental factors such as nutritional interventions during early developmental stages affect and establish long-term metabolic changes in all animals. Diets used during the spawning period causes a nutritional programming effect in offspring of gilthead sea bream and affects long-term metabolism. Studies showed modulation of genes such as fads2 which is considered to be a rate-limiting step in the synthesis of n-3 long chain polyunsaturated fatty acids (n-3 LC-PUFA). However, it is still unknown whether this adaptation is related to the presence of precursors or limitations in the pre-formed products, n-3 LC-PUFA, contained in the diets used during nutritional programming. This study investigates the combined effects of nutritional programming through broodstock diets during the spawning period and broodfish showing higher or lower fads2 expression levels in the blood after 1-month feeding with a diet containing high levels of plant protein sources and vegetable oils (VM/VO). Broodfish showing high fads2 expression had a noticeable improvement in the spawning quality parameters as well as on the growth of 6 months old offspring when challenged with a high VM/VO diet. Further, nutritional conditioning with 18:3n-3 rich diets had an adverse effect in comparison to progeny obtained from fish fed high fish meal and fish oil (FM/FO) diets, with a reduction in growth of juveniles. Improved growth of progeny from the high fads2 broodstock combined with similar muscle fatty acid profiles is an excellent option also for tailoring and increasing the flesh n-3 LC-PUFA levels to meet the recommended dietary allowances for human consumption.

Polyunsaturated fatty acids (PUFA) in parental diets play a key role in regulating n-3 LC-PUFA metabolism of the offspring. However, it is not clear whether this metabolic regulation is driven by the precursors presented in the diet or by the parental ability to synthesize them. To elucidate this, broodstocks of gilthead sea bream with different blood expression levels of fads2, which encodes for the rate-limiting enzyme in the n-3 LC-PUFA synthesis pathway, were fed either a diet supplemented with alpha-linolenic acid (ALA, 18:3n-3) or a control diet. The progenies obtained from these four experimental groups were then challenged with a low LC-PUFA diet at the juvenile stage. Results showed that the offspring from parents with high fads2 expression presented higher growth and improved utilization of low n-3 LC-PUFA diets compared to the offspring from parents with low fads2 expression. Besides, an ALA-rich diet during the gametogenesis caused negative effects on the growth of the offspring. The epigenetic analysis demonstrated that methylation in the promoter of fads2 of the offspring was correlated with the parental fads2 expression levels and type of the broodstock diet., This work has been (partly) funded under the EU Horizon 2020 programme by the PERFORMFISH project no. 727610: Consumer driven production: Integrating innovative approaches for competitive and sustainable performance across the Mediterranean aquaculture value chain.

The concept of nutritional programming raises the interesting possibility of directing specific metabolic pathways or functions in juvenile fish, for example, to improve the use of substitutes to fishmeal and oil, and hence to promote sustainability in aquaculture. The aim of the study was to determine effects of early nutritional stimuli of gilthead seabream larvae and check if nutritional programming of gilthead sea bream is possible between 16 days post hatching (dph) and 26 dph. A trial was conducted to determine the effects of early nutritional stimuli of gilthead seabream larvae. Five experimental microdiets (pellet size

The decreased availability of fish oil, traditionally used as oil source in marine aquafeeds, has lead to the search for alternatives oils. Vegetable oils (VO) are being extensively used as lipid sources in marine fish diets, inducing an imbalance on certain dietary fatty acids. Alteration on the dietary ratio of w-6/w-3 has been described to have detrimental effects on fish immunity. Senegalese sole has high susceptibility to stress and diseases, and little is known on the effects of dietary VO on its immunity. In this study, Senegalese sole juveniles were fed diets (56% crude protein, 12% crude lipid) containing linseed (100LO), soybean (100SO) or fish (100FO) oils as unique oil source. Growth, cortisol and intestinal fatty acid composition were determined after 90 days. Moreover, at the final of the experiment a stress test (5 min of net chasing) was carried out. To evaluate the effect of diets and stress on intestine immunology, expression profiles of a set of 53 immune-related genes using RT-qPCR was also performed. The use of VO did not induced changes in fish growth, but affected fatty acid profile of intestine and expression of immune-related genes. The use of SO (rich in n-6 fatty acids) induced an over-expression of those genes related to complement pathway, recognizing pathogen associated to molecular patterns, defensive response against bacteria, defensive response against viruses, antigen differentiation, cytokines and their receptors. This general over-expression could indicate an activation of inflammatory processes in fish gut. When a stress was applied, a decrease of mRNA levels of different immune-related genes with respect to the unstressed control could be observed in fish fed 100FO. However, fish fed 100LO, with a higher ALA/LA ratio, seemed to ameliorate the effects of combined effects of FO substitution plus stressful situation whereas fish fed 100SO did not show this type of response.

Substituting fishmeal (FM) with vegetable meal (VM) can markedly affect the mineral composition of feeds, and may require additional mineral supplementation. Their bioavailability and optimal supplementation levels depend also on the form of delivery of minerals. The aim of the study was to determine the effect of different delivery forms of three major trace elements (Zn, Mn and Se) in a marine teleost. Gilthead sea bream juveniles of 22.5 g were fed a VM-based diet for 12 weeks that was either not supplemented with these minerals or supplemented with inorganic, organic, or encapsulated inorganic forms of minerals in triplicate and compared to a FM-based diet. Our results showed that mineral delivery form significantly affected the biochemical composition and morphology of posterior vertebrae. Supplementation of VM-based diets with inorganic forms of the target minerals significantly promoted growth, increased the vertebral weight and content of ash and Zn, enhanced bone mineralization and affected the vertebral shape. Conversely, encapsulation of inorganic minerals reduced fish growth and vertebral mineral content, whereas supplementation of organic minerals, enhanced bone osteogenesis by upregulating bone morphogenetic protein 2 (bmp2)gene and produced vertebrae with a larger length in relation to height. Furthermore, organic mineral forms of delivery downregulated the expression of oxidative stress related genes, such as Cu/Zn superoxide dismutase (Cu/Znsod) and glutathione peroxidase 1 (gpx-1),suggesting thus that dietary minerals supplemented in the organic form could be reasonably considered more effective than the inorganic and encapsulated forms of supply.

The objective of the present study was to compare the effectiveness of dietary marine phospholipids (MPL) obtained from krill and soybean lecithin (SBL) on the rearing performance and development of seabream (Sparus aurata) larvae. Larvae were fed from 16 to 44 day posthatching (dph) five formulated microdiets with three different levels (50, 70 and 90 g kg–1) of phospholipids (PL) obtained either from an MPL or from a SBL source. Larvae-fed MPL show a higher survival, stress resistance and growth than those-fed SBL, regardless the dietary PL level. Overall, the increase in MPL up to 70 g kg–1 total PL in diet was enough to improve larval gilthead seabream performance, whereas even the highest SBL inclusion level (90 g kg–1 PL) was not able to provide a similar success in larval growth or survival. Inclusion of SBL markedly increased the peroxidation risk as denoted by the higher TBARs in larvae, as well as a higher expression of CAT, GPX and SOD genes. Moreover, SBL tends to produce larvae with a lower number of mineralized vertebrae and a lower expression of osteocalcin, osteopontin and BMP4 genes. Finally, increasing dietary MPL or SBL lead to a better assimilation of polyunsaturated fatty acids in the larvae, n-3HUFA (especially 20:5n-3) or n-6 fatty acids (especially 18:2n-6), respectively. In conclusion, MPL had a higher effectiveness in promoting survival, growth and skeletal mineralization of gilthead seabream larvae in comparison with SBL.

Although dietary marine phospholipids are able to improve culture performance of marine fish larvae in a further extend than soybean lecithin, both types of phospholipids (PL) markedly increase oxidative risk. The inclusion of a fat-soluble antioxidant such as the vitamin E α-tocopherol could allow a better control of oxidative stress. The objective of this study was to determine the combined effect of graded levels of α-tocopherol with different levels and sources of krill phospholipids (KPL) and soybean lecithin (SBL) on growth, survival, resistance to stress, oxidative status, bone metabolism-related genes expression and biochemical composition of sea bream larvae. Sea bream larvae were completely weaned at 16 dph and fed for 30 days seven microdiets with three different levels of PL (0, 40 and 80 g kg−1 diet) and two of α-tocopherol 1500 and 3000 mg kg−1 diet. Sea bream larvae fed diets without PL supplementation showed the lowest survival, growth and stress resistance, whereas increase in PL, particularly KPL, markedly promoted larval survival and growth. However, feeding SBL markedly increased TBARs and GPX gene expression increasing the peroxidation risk in the larvae. Besides, KPL inclusion improved incorporation of n-3 HUFA and, particularly, EPA into larval tissues, these fatty acids being positively correlated with the expression of BMP-4, RUNX 2, ALP, OC and OP genes and to bone mineralization for a given larval size class. The increase in dietary α-tocopherol tends to improve growth in relation to the n-3 HUFA levels in the diet, denoting the protective role of this vitamin against oxidation. Indeed, dietary α-tocopherol decreased the oxidative stress in the larvae as denoted by the reduction in larval TBARs contents and gene expression of SOD and CAT, but not GPX. Thus, increase in dietary α-tocopherol effectively prevented the formation of free radicals from HUFA, particularly EPA, but did not affect the incidence of bone anomalies or the expression of genes related to osteogenetic processes.

The inclusion of complementary antioxidative factors, such as selenium (Se), could counteract the high oxidation risk in early weaning diets high in polyunsaturated fatty acids (PUFA). The present study investigated the effects of graded levels of Se derived yeast with krill phospholipids (KPL) on skeletal development, survival, stress resistance, oxidative status and biochemical composition of seabream larvae. Seabream larvae were completely weaned at 16 dph and fed five microdiets for 30 days with different levels of Se: 2SE, 4SE, 6SE, 8SE and 12SE (1.73, 3.91, 6.41, 8.47, 11.65 mg kg− 1 dietary dry weight, respectively). Increases in Se up to 11.65 mg kg− 1 dietary dry weight significantly improved survival rate (54%) and stress resistance, but did not affect larval growth. Seabream larvae fed diets supplemented with 12SE (11.65 mg kg− 1) showed a gradual increase in this mineral according to dietary Se levels, denoting the progressive absorption of this nutrient. The degree of larval lipid oxidation, as indicated by malondialdehyde (MDA) content and antioxidant enzyme (AOE) gene expression, was significantly lower in larvae fed 8SE and 12SE diets compared to those fed 2SE and 4SE diets. Furthermore, a reactive response as a result of Se inclusion was observed by the increase in osteocalcin, osteonectin, osteopontin, alkaline phosphatase and matrix gla protein gene expression in larval tissues, suggesting a well skeletal development. These results denoted the high efficiency of Se as an antioxidant factor and the importance of the inclusion of adequate levels (11.65 mg Se kg− 1 diet) in early weaning diets.

This study reports for the first time on European sea bass, Dicentrarchus labrax (L.), larvae, the effect of different levels of dietary arachidonic acid (ARA; 20:4n-6) on the expression of genes related to the fish stress response. Copies of mRNA from genes related to steroidogenesis [StAR (steroidogenic acute regulatory protein), c-Fos, and CYP11β (11β-hydroxylase gene)], glucocorticoid receptor complex [GR (glucocorticoid receptor) and HSP (heat shock proteins) 70 and 90) and antioxidative stress (catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase] were quantified. Eighteen day-old larvae were fed for 14 days with three experimental diets with increasing levels of ARA (0.3, 0.6 and 1.2 % d.w.) and similar levels of docosahexaenoic (22:6n-3) and eicosapentaenoic (20:5n-3) acids (5 and 3 %, respectively). The quantification of stress-related genes transcripts was conducted by One-Step TaqMan real time RT-PCR with the standard curve method (absolute quantification). Increase dietary levels of ARA induced a significantly (p

Dietary fatty acids have been shown to exert a clear effect on the stress response, modulating the release of cortisol. The role of fatty acids on the expression of steroidogenic genes has been described in mammals, but little is known in fish. The effect of different fatty acids on the release of cortisol and expression of stress-related genes of European sea bass (Dicentrarchus labrax) head kidney, induced by a pulse of adenocorticotrophin hormone (ACTH), was studied. Tissue was maintained in superfusion with 60 min of incubation with EPA, DHA, arachidonic acid (ARA), linoleic acid or α-linolenic acid (ALA) during 490 min. Cortisol was measured by RIA. The quantification of stress-related genes transcripts was conducted by One-Step TaqMan real-time RT-PCR. There was an effect of the type of fatty acid on the ACTH-induced release of cortisol, values from ALA treatment being elevated within all of the experimental period. The expression of some steroidogenic genes, such as the steroidogenic acute regulatory protein (StAR) andc-fos, were affected by fatty acids, ALA increasing the expression of StAR after 1 h of ACTH stimulation whereas DHA, ARA and ALA increased the expression ofc-fosafter 20 min. ARA increased expression of the 11β-hydroxylase gene. Expression of heat shock protein 70 (HSP70) was increased in all the experimental treatments except for ARA. Results corroborate previous studies of the effect of different fatty acids on the release of cortisol in marine fish and demonstrate that those effects are mediated by alteration of the expression of steroidogenic genes.

The study assesses the effects of dietary concentrated mannan oligosaccharides (cMOS) on fish performance, biochemical composition, tissue fatty acid profiles, liver and posterior gut morphology and gen expression of selected parameters involved on the intestinal immune response and liver lipid metabolism of European sea bass ( Dicentrarchus labrax ). For that purpose, specimens of 20 g were fed during 8 weeks at 0 and 1.6 g kg −1 dietary cMOS of inclusion in a commercial sea bass diet. Dietary cMOS enhanced fish length, specific and relative growth without affecting tissue proximate composition. However, cMOS supplementation altered especially liver and muscle fatty acid profiles by reducing levels of those fatty acids that are preferential substrates for β-oxidation in spite of a preferential retention of long chain polyunsaturated fatty acids (LC-PUFA), such as 20:4n-6 or 22:5n-6, in relation to the down-regulation of delta 6/5 desaturase gene expression found in liver. Besides, dietary cMOS supplementation reduced posterior gut intestinal folds width and induced changes on the gene expression level of certain immune-related genes mainly by down regulating transforming growth factor β (TGFβ) and up-regulating immunoglobulin (Ig), major histocompatibility complex class II (MHCII), T cell receptor β (TCRβ) and Caspase 3 (Casp-3). Thus, dietary cMOS inclusion at 0.16% promoted European sea bass specific growth rate and length, stimulated selected cellular GALT-associated parameters and affected lipid metabolism in muscle and liver pointing to a higher LC-PUFA accumulation and promoted β-oxidation.

One of the factors that limits the replacement of fish meal (FM) and fish oil (FO) by plant ingredients in diets for marine fish, is their lack of long chain-polyunsaturated fatty acids (LC-PUFA). LC-PUFA are essential fatty acids for these fish species, which lack sufficient fatty acyl desaturase 2 (Fads2) activity to synthesize them. Nutritional programing or the use of broodstock with a higher Fads2 activity could improve marine fish ability to synthesize LC-PUFA and their ability to use low FM and FO diets. The aim of this study was to determine the effect of gilthead seabream broodstock with inherently high or inherently lowfads2gene expression and nutritional programing with broodstock diets rich in FO or rapeseed oil (RO) on the progeny growth performance, liver morphology, biochemical composition and expression of selected genes. Sea bream juveniles (2.31± 0.01g initial body weight, mean ± SD) obtained from broodstock with either high (H) or low (L)fads2expression and fed a broodstock diet based on FO or RO were randomly distributed into 12×250L tanks and nutritionally challenged for 45days with a diet containing only 7.5% FM and no FO. The highest growth was found in juveniles from broodstock with a highfads2expression and fed the RO diet, whereas the lowest growth was obtained in those from broodstock with a lowfads2expression and fed the RO diet. Juveniles from broodstock with highfads2expression showed significantly higherfads2expression in liver and increased PUFA contents in liver and muscle. Replacement of FO by RO in broodstock diets led to a significantly increased hepatic 18:3n-6/18:2n-6 ratio and reduction in the viscerosomatic index of the progeny juveniles, the hepatocyte size and theghr-1/ghr-2expression in muscle. Overall, the results showed significant trans-generational effects of both the broodstockfads2expression and the type of lipid in the broodstock diet on the metabolism and performance of the juvenile progeny challenged with a diet low in FM and FO.