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Previously, we reported that methionine intake determined the taurine concentration in the liver of on-growing Atlantic salmon fed plant protein diets. Further, the methionine intake and/or the increased taurine concentration following increased methionine intake affected the liver lipid metabolism. The following study therefore aimed to test whether taurine affected the growth or the type of growth when added in high plant protein diets naturally low in taurine but equal and adequate in dietary methionine. Juvenile Atlantic salmon [initial body weight (BW) of 2 g] were fed plant protein diets (16.5% fishmeal), which were supplemented with taurine or not for a period of 56 days. As a control for growth and normal metabolism, a fishmeal-based commercial diet (68% fishmeal) was used. Supplementation with taurine to high plant protein diets had a slightly negative effect on weight gain, but the final body weight was not different. Interestingly, the pool of free amino acids in the liver and muscle was significantly higher in fish fed the supplemented diet as compared with fish fed the plant protein diet without taurine supplementation. Liver polyamine concentration was higher in fish fed the supplemented diet than in fish fed the similar diet without supplementation. Additionally, juvenile salmon fed the plant-based diet supplemented with taurine had a lower body lipid-to-protein ratio due to a reduced whole-body lipid content, while the whole-body protein content was similar between treatments. Our study thus indicates that the addition of a low concentration of taurine to high plant protein diets interacts with lipid metabolism and storage, concomitantly affecting the general metabolism as the concentrations of the free amino acids and polyamines in the liver were significantly higher. The possible reasons for these changes are discussed. [ABSTRACT FROM AUTHOR]

In the current study, we tested whether the addition of a small amount of crystalline DL-methionine to a ￠shmeal-based diet would a!ect general sulphur metabolism and apparent digestibility in Atlantic almon (Salmo salar). Triplicate tanks of salmon with mean BWof half a kilo were fed a control diet or the control diet supplemented with 0.2wt% DL-methionine (117% methionine relative to control diet) for a period of 3 months. Feed intake and thus nutrient intake did not di!er signi￠cantly between treatments. Fish fed the diet supplemented with DL-methionine had 18% higher mean intake of methionine. The apparent energy digestibility was significantly improved in the salmon fed the methionine- enriched diet as was the methionine digestibility. Salmon fed the methionine-supplemented diet had about 32% higher plasma-free methionine concentration and 25% more total homocysteine 5 h post prandial. No difference was observed in hepaticfree methionine, but hepatic cystathionine (∼ 62%) and taurine (∼ 20%) were signi￠cantlyhigher in ￠sh fed the methionine-enriched diet due to a higher ranssulphuration. In the liver, taurine might be conjugated to bile acids (BAs), and conjugation of BAs increases their solubility and enhances their biliary secretion a!ecting the digestibility. Both faecal and plasma BA concentrations were elevated in ￠sh fed the methionine-enriched diet, although the di!erences did not reach statistical significance. Taken together, our data show that feeding salmon a ￠shmeal-based diet supplemented with a small amount of crystalline DL-methionine increased the apparent energy digestibility, possibly through an increased liver transsulphuration and taurine production, which might enhance BA conjugation and biliary secretion. [ABSTRACT FROM AUTHOR]

It has previously been demonstrated that soya protein, which contains isoflavones and low methionine???glycine and lysine???arginine ratios, has a hypocholesterolaemic effect. In the present study, the hypocholesterolaemic effects of an isoflavone-enriched casein diet (HDI) and a single-cell protein-based diet (SCP) devoid of isoflavones but with low methionine???glycine and lysine???arginine ratios were investigated in obese Zucker rats after 6 weeks of feeding. The control diet contained casein, which has high ratios of methionine???glycine and lysine???arginine. HDI and SCP feeding reduced the concentrations of total cholesterol and cholesteryl esters in plasma and liver, and changed the fatty acid composition of the hepatic cholesteryl esters. Faecal cholesterol and bile acid levels were markedly higher in SCP-fed rats than in controls, whereas HDI feeding had only minor effects. However, both HDI and SCP feeding increased the hepatic gene expression of cholesterol 7?? hydroxylase. In contrast, the hepatic acyl-CoA synthetase and acyl-CoA:cholesterol acyltransferase activities and the gene expression of the LDL receptor were increased by HDI, but not by SCP feeding. The present results suggested that the cholesterol-lowering effect of SCP was related to the enterohepatic circulation, whereas HDI seemed to lower the plasma cholesterol via the circulation. Plasma homocysteine level was reduced in rats fed HDI and SCP compared to rats fed casein. In summary, diets enriched in isoflavones or containing proteins with low methionine???glycine and lysine???arginine ratios lowered the plasma cholesterol and homocysteine levels, changing the plasma profile from atherogenic to cardioprotective. [ABSTRACT FROM PUBLISHER]

Farmed Atlantic salmon (Salmo salar L.) were slaughtered at an average weight of 5.5 kg in May 2001 under either traditional CO2 anaesthesia (denoted high stress) or a two-step iso-eugenol anaesthesia (denoted low stress) before being bled to death in chilled seawater. Product quality analyses were performed on fillets after 5 days on ice and on cutlets after 12 months of frozen storage (-25 °C). In ice-stored fillets, no differences in gaping were observed between the two anaesthetic protocols, but instrumental analyses revealed that the flesh of the salmon exposed to CO2 sedation was softer and slightly redder (higher a*-value, 27.1±0.1, S.E. versus 26.4±0.1, p<0.0004) and more yellowish (higher b*-value, 22.6±0.1 versus 22.0±0.1, p<0.0001) than the salmon anaesthetised using iso-eugenol. Analyses of frozen–thawed cutlets confirmed the fresh fillet results in that salmon anaesthetised using iso-eugenol were firmer and paler (RocheSalmoFan™ score, 23.5±0.4 versus 24.4±0.3, p<0.05) than the salmon anaesthetised using CO2. Furthermore, the frozen and thawed cutlets of iso-eugenol-anaesthetised salmon had a higher muscle pH (6.15±0.01 versus 5.98±0.03, p<0.05) and lower liquid loss (5.1±0.3 versus 7.1±0.3, p<0.05). Individual growth rate, final body weight (BW), final body length, condition factor (CF), sex, gonadosomatic index (GI) were also registered. No significant correlations (p>0.15) between these growth and body conformation variables and gaping or fillet softness were detected.In conclusion, no differences were observed in fillet gaping between the two anaesthetic protocols, but the salmon anaesthetised using iso-eugenol were firmer, paler and had a higher water-holding capacity than salmon exposed to CO2 anaesthesia. [Copyright &y& Elsevier]

A radioactive soluble model protein for studies of protein digestion, absorption and amino acid (AA) metabolism in larval fish was successfully produced in Atlantic salmon by oral administration of uniformly [U]-14C-labelled amino acids followed by blood sample withdrawal (48 h post-administration) and purification. The salmon serum protein (14C-SSP) was characterised in terms of the protein composition and specific activity of its amino acids. Most radioactivity was found in the three most abundant serum proteins, which had apparent molecular weights of 65, 75 and 120 kDa, respectively, of which labelling was found in all the amino acid residues of the SSP that were analysed. The digestibility of the 14C-SSP was tested by in vivo tube feeding using early stages of Atlantic halibut and was found to be more efficiently digested and utilised than the 14C-methylated bovine serum albumin (14C-BSA) that has been used in previous studies. This supports the notion that proteins labelled by 14C-methylation are not suitable as model proteins in metabolic studies due to modification of their 14C-methylated lysine residues. Further studies on the 14C-SSP demonstrated a digestibility of 59±13% in juvenile halibut, while at the pre-metamorphic stage, it was only 25±13%. This supports the hypothesis that there is a significant improvement in the ability to digest and utilise dietary proteins as the digestive system becomes fully developed, including a functional (acid-producing) stomach. [Copyright &y& Elsevier]

A simple and rapid method for the extraction of D-series resolvins (RvD1, RvD2, RvD3, RvD4, RvD5) released into Leibovitz's L-15 complete medium by head kidney cells from Atlantic salmon and the further determination of liquid chromatography triple quadrupole mass spectrometry is proposed. A three-level factorial design was proposed to select the optimal concentrations of internal standards that were used in the evaluation of the performance parameters, such as linear range (0.1–50 ng mL−1), limits of detection and quantification (0.05 and 0.1 ng mL−1, respectively), and recovery values ranging from 96.9 to 99.8%. The optimized method was used to determine the stimulated production of resolvins by head kidney cells exposed to docosahexaenoic acid, and the results indicated that it is possible that the production was controlled by circadian responses. [ABSTRACT FROM AUTHOR]

Future feed for farmed fish are based on untraditional feed ingredients, which will change nutrient profiles compared to traditional feed based on marine ingredients. To understand the impact of oils from different sources on fish health, n-6 and n-3 polyunsaturated fatty acids (PUFAs) were added to salmon head kidney cells, in a fully crossed design, to monitor their individual and combined effects on gene expression. Exposing salmon head kidney cells to single fatty acids, arachidonic acid (AA) or decosahexaenoic acid (DHA), resulted in down-regulation of cell signaling pathway genes and specific fatty acid metabolism genes as well as reduced prostaglandin E2 (PGE2) secretion. Eicosapentaenoic acid (EPA) had no impact on gene transcription in this study, but reduced the cell secretion of PGE2. The combined effect of AA + EPA resulted in up-regulation of eicosanoid pathway genes and the pro-inflammatory cytokine, tumor necrosis factor alpha (TNF-α), Bclx (an inducer of apoptosis) and fatty acid translocase (CD36) as well as increased cell secretion of PGE2 into the media. Adding single fatty acids to salmon head kidney cells decreased inflammation markers in this model. The combination AA + EPA acted differently than the rest of the fatty acid combinations by increasing the inflammation markers in these cells. The concentration of fatty acid used in this experiment did not induce any lipid peroxidation responses. [ABSTRACT FROM AUTHOR]

Abstract: Atlantic salmon were fed a standard extruded dry feed (Control) or the same feed supplemented with 1.5% l-glutamate (Glu) (triplicate net pens per diet) from May 2009 (body weight=105g) to May 2010 (body weight=3.1kg). No significant differences were observed in growth (TGC=3.1) or feed conversion ratio (1.0) between the dietary treatments. Instrumental texture analyses showed that Glu supplementation resulted in significantly (P≤0.05) firmer fillets after ice storage (10.1 vs. 9.1N) and after frozen storage (8.7 vs. 6.3N). Additionally the Glu group had less organ adhesions (score=0.5 vs. 1.1), lower hepato-somatic index (0.91 vs. 0.99%) and less fat accumulated in the livers (1.8 vs. 2.1g). The condition factor, carcass and fillet yield, and cardio- and spleen-somatic indices were unaffected by dietary treatment. Hepatocellular vacuolization, intestinal inflammation and muscle degeneration were observed in the Control (50, 13, and 5%, respectively) and the Glu group (40, 7, and 25%, respectively). No abnormal observations were found in the spleen or kidney. Plasma analyses revealed significantly lower activity of creatine kinase (3.3 vs. 5.8U/mL) and alanine aminotransferase (5.8 vs. 7.5U/L) in the Glu fed group. Muscle pH was significantly higher in the Glu group (6.22 vs. 6.19), but the fat-, protein-, amino acid-, and collagen contents were similar. The Glu group had significantly higher concentrations of saturated fatty acids and docosapentaenoic acid (1.9 vs. 1.7 and 17.4 vs. 17.1% of fatty acids, respectively), and n−3 fatty acids and n−3/n−6 ratio in the muscle tended to be higher (P<0.09). Collagen properties determined as degree of glycation, solubility, thermal behaviour, pyridinoline bonds and structure were similar for both dietary groups. Compared with the Control, the skeletal muscle of salmon fed the Glu supplemented diet showed up-regulation of genes involved in stress response, mitochondrial functions, and amino acid and lipid metabolism, whereas several genes involved in cytoskeletal structure were down-regulated. Glu supplementation resulted in firmer fillets, coinciding with altered energy metabolism and improved health related parameters. It is suggested that optimal dietary amino acid levels for growth may differ from optimal levels for good fish health and flesh quality. [Copyright &y& Elsevier]

Abstract: Cobia (Rachycentron canadum, Actinopterygii, Perciformes;10.5±0.1g) were fed to satiation with three plant-based protein test diets with different lysine (L) to arginine (A) ratios (LL/A, 0.8; BL/A, 1.1; and HL/A, 1.8), using a commercial diet as control for six weeks. The test diets contained 730gkg−1 plant ingredients with 505–529g protein, 90.2–93.9g lipidkg−1 dry matter; control diet contained 550g protein and 95g lipidkg−1 dry matter. Periprandial expression of brain NPY and CCK (npy and cck) was measured twice (weeks 1 and 6). At week one, npy levels were higher in pre-feeding than postfeeding cobia for all diets, except LL/A. At week six, npy levels in pre-feeding were higher than in postfeeding cobia for all diets. cck in pre-feeding cobia did not differ from that in postfeeding for all diets, at either time point. Cobia fed LL/A had lower feed intake (FI) than cobia fed BL/A and control diet, but no clear correlations between dietary L/A ratio and FI, growth and expression of npy and cck were detected. The data suggest that NPY serves as an orexigenic factor, but further studies are necessary to describe links between dietary L/A and regulation of appetite and FI in cobia. [Copyright &y& Elsevier]

Background: DNA methylation has an important role in intergenerational inheritance. An increasing number of studies have reported evidence of germline inheritance of DNA methylation induced by nutritional signals in mammals. Vitamins and minerals as micronutrients contribute to growth performance in vertebrates, including Atlantic salmon (Salmo salar), and also have a role in epigenetics as environmental factors that alter DNA methylation status. It is important to understand whether micronutrients in the paternal diet can influence the offspring through alterations of DNA methylation signatures in male germ cells. Results: Here, we show the effect of micronutrient supplementation on DNA methylation profiles in the male gonad through a whole life cycle feeding trial of Atlantic salmon fed three graded levels of micronutrient components. Our results strongly indicate that micronutrient supplementation affects the DNA methylation status of genes associated with cell signalling, synaptic signalling, and embryonic development. In particular, it substantially affects DNA methylation status in the promoter region of a glutamate receptor gene, glutamate receptor ionotropic, NMDA 3A-like (grin3a-like), when the fish are fed both medium and high doses of micronutrients. Furthermore, two transcription factors, histone deacetylase 2 (hdac2) and a zinc finger protein, bind to the hyper-methylated site in the grin3a-like promoter. An estimated function of hdac2 together with a zinc finger indicates that grin3a-like has a potential role in intergenerational epigenetic inheritance and the regulation of embryonic development affected by paternal diet. Conclusions: The present study demonstrates alterations of gene expression patterns and DNA methylation signatures in the male gonad when Atlantic salmon are fed different levels of micronutrients. Alterations of gene expression patterns are of great interest because the gonads are supposed to have limited metabolic activities compared to other organs, whereas alterations of DNA methylation signatures are of great importance in the field of nutritional epigenetics because the signatures affected by nutrition could be transferred to the next generation. We provide extensive data resources for future work in the context of potential intergenerational inheritance through the male germline. [ABSTRACT FROM AUTHOR]

Redox control seems to be indispensable for proper embryonic development. The ratio between glutathione (GSH) and its oxidized disulfide (GSSG) is the most abundant cellular redox circuit. We used zebrafish harboring the glutaredoxin 1-redox sensitive green fluorescent protein (Grx1-roGFP) probe either in mitochondria or cytosol to test the hypothesis that the GSH:GSSG ratio is strictly regulated through zebrafish embryogenesis to sustain the different developmental processes of the embryo. Following the GSSG:GSH ratio as a proxy for the GSH-dependent reduction potential (E h GSH) revealed increasing mitochondrial and cytosolic E h GSH during cleavage and gastrulation. During organogenesis, cytosolic E h GSH decreased, while that of mitochondria remained high. The similarity between E h GSH in brain and muscle suggests a central regulation. Modulation of GSH metabolism had only modest effects on the GSSG:GSH ratios of newly hatched larvae. However, inhibition of GSH reductase directly after fertilization led to dead embryos already 10 h later. Exposure to the emerging environmental pollutant Perfluorooctane Sulfonate (PFOS) disturbed the apparent regulated E h GSH as well. Mitochondrial and cytosolic GSSG:GSH ratios are almost identical in different organs during zebrafish development indicating that the E h GSH might follow H 2 O 2 levels and rather indirectly affect specific enzymatic activities needed for proper embryogenesis. Our data confirm that vertebrate embryogenesis depends on strictly regulated redox homeostasis. Disturbance of the GSSG:GSH circuit, e.g. induced by environmental pollution, leads to malformation and death. [Display omitted] • No organ specific mitochondrial and cytosolic GSH:GSSG ratios in zebrafish larvae. • Almost no effects of manipulated GSH metabolism on E h GSH in older zebrafish larvae. • Inhibition of GSH reductase in young larvae leads to malformation and death. • The environmental pollutant Perfluorooctane Sulfonate affects E h GSH in larvae. [ABSTRACT FROM AUTHOR]

A full life cycle (parr to harvest) study of growth and performance was conducted in Atlantic salmon fed diets high in plant ingredients supplemented with graded levels of a nutrient premix (NP), containing selected amino acids, taurine, cholesterol, vitamins and minerals to re-evaluate current nutrient recommendations. Triplicate groups were fed one of three NP levels included at 1×, 2× and 4×, where 1× corresponds to recommendations of NRC (2011). Whole body and specific tissue concentrations of nutrients were monitored throughout the experiment as requirement markers. Growth in parr was significantly enhanced in 2xNP, but restricted in 4xNP, while in post-smolts growth was positively correlated with NP level. Spinal deformity decreased linearly with increased NP level in both smolt and post-smolts. When fishmeal and fish oil are present at very low levels, as in the present study, we found beneficial effects with moderate increased levels of the B-vitamins niacin, riboflavin and cobalamin. Further, vitamin C should be increased, based on metabolic responses, although it did not influence growth. Increased Zn and Se affected fish metabolism in a positive manner. Alterations in hepatic transcriptome profiles and expression of specific genes of metabolic pathways were evident in response to micronutrient supplementation level. Collectively, increasing the levels of the micro-nutrient package to a too high level, showed a negative effect and cannot be recommended. NRC (2011) recommendations should therefore be revised for diets in which plant ingredients form the major part of the formulation. • Plant based diets can support optimal growth in Atlantic salmon when micronutrient inclusion levels are increased. • Skeletal health is inversely correlated with dietary micronutrient supplementation level. • NRC 2011 minimum dietary recommendations for Atlantic salmon need to be revised when utilising low marine ingredient diets. • Increased levels of the B-vitamins niacin, riboflavin and cobalamin and the minerals Zn and Se are recommended. [ABSTRACT FROM AUTHOR]

Selenium (Se) supplementation either as inorganic or organic form was evaluated in Atlantic salmon post-smolt in vivo and in vitro. The basal diet was formulated to be low in fish meal and contain 0.24 mg Se kg−1; six other diets with Se inclusion of 0.15, 0.4, 0.7 or 1.1 mg kg−1 as sodium selenite (SS) and 0.15 or 0.4 mg kg−1 as L-selenomethionine (SM) were formulated from the basal diet. The diets were fed to Atlantic salmon post-smolt (mean initial weight, 216 ± 27 g) in triplicate groups (35 fish tank−1) and reared in flow-through seawater (33 ppt) at 10–12 °C for 9 weeks. At the end of the feeding trial, whole fish and tissues were sampled for in vivo assessment; whereas, liver cells and head kidney leukocytes (HKL) were isolated and their primary cultures used for in vitro assessment following exposure to hydrogen peroxide (H 2 O 2), lipopolysaccharide (LPS) or poly I:C (PIC). Growth, feed intake, feed conversion ratio, specific growth rate, hepato-somatic index, proximate composition and mineral concentration of the whole fish (except for Se) were unaffected by dietary Se (p >.05). Hematocrit was significantly higher in fish fed the 0.4 mg Se supplemented feeds, irrespective of the Se source (p =.02). The Se concentration in whole body, liver, muscle, plasma, kidney and liver/kidney Se ratio increased with increasing dietary Se concentration (p <.0001). Level of oxidised glutathione (GSSG) in liver and head kidney followed a quadratic function (p <.05) indicating that the concentrations were lower at intermediate SS supplementation of 0.4 and 0.65 mg Se kg−1 (total Se, 0.65 and 0.87 mg Se kg−1). Impact of Se sources on glutathione redox status was similar. Slope-ratio analysis revealed SM to be more efficient than SS in improving apparent availability, whole body or tissues Se status, Se retention and reducing Se loss to the environment. In vitro , the mRNA expression of p38mapk and aif , in liver cells were affected by the impact of dietary Se, but not by the treatment of H 2 O 2 (p <.05). In the HKL, the LPS and PIC induced pro-inflamatory action of il-1β , cox2 , nfkβ and viperin were attenuated by SM supplementation, but not by SS (p <.001). Dietary Se supplementation required to the basal diet containing 0.24 mg Se kg−1 was 0.41 mg Se as SS (total 0.65 mg kg−1) or 0.17 mg Se as SM (total 0.41 mg kg−1) based on body Se homeostasis or tissue Se status. SM inclusion at 0.4 mg kg−1 diet (total, 0.65 mg kg−1) attenuated LPS or PIC induced pro-inflammatory responses in vitro. Overall, Se requirement of Atlantic salmon post smolt was 0.27 mg kg−1 diet, on availale basis. Dietary Se level required to maintain body Se homeostasis and improved health status of Atlantic salmon fed plant-based diets (0.65 mg kg−1 diet) exceed the existing EU maximum limit of 0.5 mg Se kg−1 diet. SM as the Se source in salmon feeds has the potential to improve salmon health and reduce Se emissions from Norwegan salmon farming by 60 to 70%. • Impact of selenium (Se) nutrition in Atlantic salmon post-smolt fed low fish meal feeds was studied in vivo and in vitro • Se requirement of Atlantic salmon post-smolt was 0.27 ppm based on body or tissue homeostasis, on available basis • Se inclusion at 0.4 ppm as sodium selenite (total Se, 0.65 ppm) satisfied the Se requirement of Atlantic salmon post-smolt • Inflammatory response to LPS or PIC in head kidney leukocytes were attenuated by 0.4 ppm Se inclusion as selenomethionine • Se emission from Atlantic salmon farming can be reduced by 60-70% by using selenomethionine as Se source [ABSTRACT FROM AUTHOR]