The effect of micronutrient supplementation on growth and hepatic metabolism in diploid and triploid Atlantic salmon (Salmo salar) parr fed a low marine ingredient diet
ABSTRACT: Current commercially available feeds for salmon are predominantly made of plant ingredients, with consequent changes to the composition and contents of a range of nutrients and other components in the diet. There are concerns that, with these major changes in raw materials, new feeds will affect not only the composition and contents of nutrients, but also the bioavailability and, combined with the limited knowledge of micronutrient requirements for Atlantic salmon, this might impact growth performance and health of the fish. The present study investigated the effects of graded levels of a micronutrient package supplemented to feeds formulated with low levels of marine ingredients and fed to diploid and triploid Atlantic salmon throughout the freshwater phase. Specifically, fish were fed three diets containing low levels of FM and FO and identical in formulation other than being supplemented with 3 levels (L1, 100 %; L2, 200 % and L3, 400 %) of a micronutrient mix formulated as a modification of current nutrient levels reported for salmon. Duplicate groups of diploid and triploid parr were fed the experimental diets from around 30 g to seawater transfer and the effects on growth performance, feed efficiency, biochemical composition, liver histology, hepatic gene expression (transcriptome) and smoltification efficiency determined. Microarray analysis revealed that the hepatic transcriptome profile of diploid fish fed diet L2 was more similar to that observed in triploids fed diet L3 than to those fed L2, suggesting that micronutrient requirements of triploid salmon may differ from levels accepted in diploid salmon. Different levels of micronutrient supplementation affected the expression of key genes involved in lipid metabolism. In particular sterol biosynthesis pathways (steroid and terpenoid backbone synthesis) were down-regulated in both L2-fed diploids and L3-fed triploids when compared with diet L1-fed diploids and triploids, respectively. Gene sets analysis showed an up-regulation of genes involved in immune processes in triploid salmon fed diet L3. Another biological category affected by diet in triploid salmon was genetic information processing. In fish fed diet L3 down-regulation of RNA degradation, proteasome, RNA polymerase, spliceosome and ribosome was observed, suggesting a decrease in protein turnover in this group, which may indicate a decrease in energy expenditure. In addition, one-carbon metabolism was affected by diet in diploid and triploid salmon.
Project description:To ensure sustainability of aquaculture, plant-based ingredients are being used in feeds to replace marine-derived products. However, plants contain secondary metabolites which can affect food intake and nutrient utilisation of fish. The application of nutritional stimuli during early development can induce long-term changes in animal physiology. Recently, we successfully used this approach to improve the utilisation of plant-based diets in diploid and triploid Atlantic salmon. In the present study we explored the molecular mechanisms occurring in the liver of salmon when challenged with a plant-based diet in order to determine the metabolic processes affected, and the effect of ploidy. Microarray analysis revealed that nutritional history had a major impact on the expression of genes. Key pathways of intermediary metabolism were up-regulated, including oxidative phosphorylation, pyruvate metabolism, TCA cycle, glycolysis and fatty acid metabolism. Other differentially expressed pathways affected by diet included protein processing in endoplasmic reticulum, RNA transport, endocytosis and purine metabolism. The interaction between diet and ploidy also had an effect on the hepatic transcriptome of salmon. The biological pathways with the highest number of genes affected by this interaction were related to gene transcription and translation, and cell processes such as proliferation, differentiation, communication and membrane trafficking. The present study revealed that nutritional programming induced changes in a large number of metabolic processes in Atlantic salmon, which may be associated with the improved fish performance and nutrient utilisation demonstrated previously. In addition, differences between diploid and triploid salmon were found, supporting recent data that indicate nutritional requirements of triploid salmon may differ from those of their diploid counterparts.
Project description:This study investigated firstly, the impact of ploidy on growth performance and whole body composition of Atlantic salmon at different early freshwater stages (34 dph (days post-hatching) alevin; 109 dph; fry and 162 dph parr;) and secondly, whether phenotypic differences at these stages were reflected in protein samples collected from whole fish, white muscle or liver tissue. Female diploid and triploid Atlantic salmon (n = 3) were first fed at 35 dph and then maintained by feeding to satiation on commercial feeds. NOTE on file nomenclature - T/D refer to triploid/diploid; E* refers to sequential protein extract (1 or 2) and S3 refers to sampling time point #3 (all other files with either no suffix or long suffix are sampling time point #2)
Project description:This study investigated firstly, the impact of ploidy on growth performance and whole body composition of Atlantic salmon at different early freshwater stages (34 dph (days post-hatching) alevin; 109 dph; fry and 162 dph parr;) and secondly, whether phenotypic differences at these stages were reflected in the protein samples collectedproteome from whole fish, white muscle or liver tissue. Female diploid and triploid Atlantic salmon (n = 3) were first fed at 35 dph and then maintained by feeding to satiation on commercial feeds.
Project description:This study investigated firstly, the impact of ploidy on growth performance and whole body composition of Atlantic salmon at different early freshwater stages (34 dph (days post-hatching) alevin; 109 dph; fry and 162 dph parr;) and secondly, whether phenotypic differences at these stages were reflected in protein samples collected from whole fish, white muscle or liver tissue. Female diploid and triploid Atlantic salmon (n = 3) were first fed at 35 dph and then maintained by feeding to satiation on commercial feeds.
Project description:A common-garden experiment was carried out to compare two genetically distinct strains of Atlantic salmon (Salmo salar) fed diets formulated with either high (CHO) or low (NoCHO) carbohydrate (starch). Twenty salmon from either a commercial farmed strain or a land-locked population were placed in two tanks (10 fish of each population in each tank) and fed either CHO or NoCHO feeds for 32 days. At the end of the experimental period fish were fasted for 8 h, euthanized and samples of blood and liver collected. Both diet and population had an effect on circulating glucose levels with land-locked salmon showing hypoglycaemia and dietary starch increasing this parameter. In contrast, land-locked salmon showed increased plasma triacylglycerol levels regardless of dietary treatment. This enhanced ability to metabolise dietary starch in land-locked compared to farmed salmon stock was also reflected at a molecular (gene) level as most of the metabolic pathways evaluated in the present study were mainly affected by the factor population rather than by diet. In particular, lower expression of genes for mitochondrial metabolism in land-locked salmon reflects drastic differences in energy metabolism between the populations. The liver transcriptome analysis highlighted some new gene candidates such as elovl6 to evaluate in future studies assessing the capacity of salmonids to cope with feeds containing higher levels of dietary starch.
Project description:Liver transcriptomes of Atlantic salmon families with contrasting flesh n-3 LC-PUFA profiles, and all fed the same 100% vegetable oil replacement diet, were compared by microarray analysis (Agilent oligoarray platform). The objective was to identify gene pathways and molecular mechanisms which might explain differences in flesh n-3 LC-PUFA content, independent of total lipid deposition, when salmon families are fed the same LC-PUFA deficient diet. A factorial design was chosen in which families containing higher and lower n-3 LC-PUFA relative levels were compared at similar total lipid percentages in flesh.
Project description:As part of a study investigating the effects of genotype on responses to sustainable feeds in Atlantic salmon, a microarray analysis of the intestine transcriptome of two family groups, identified as 'Lean' or 'Fat' (based on flesh lipid content), which were fed a diet containing either 100% fish oil (FO) or 100% vegetable oil (VO) was undertaken.
Project description:There is an increasing drive to replace fish oil (FO) in finfish aquaculture diets with vegetable oils (VO), driven by the short supply of FO derived from wild fish stocks. Little is known of the consequences for fish health after such substitution. The effect of dietary VO on hepatic gene expression was determined in Atlantic salmon (Salmo salar) byg a cDNA microarray analysis. Post-smolt farmed salmon were reared for x weeks on diets where the FO component of the feed was replaced with one of three different VOs - rapeseed (RO), soybean (SO) or linseed (LO). RNA from five fish fed on each diet was extracted. A total of 20 cDNA microarray hybridisations - TRAITS / SGP Atlantic salmon 17k feature cDNA microarray - were performed - 4 diets (three VO + FO control) x 5 individuals - using a common pooled reference control design. Data were obtained from 19 of the 20 hybridisations.
Project description:New de novo sources of omega 3 (n-3) long chain polyunsaturated fatty acids (LC-PUFA) are required as alternatives to fish oil in aquafeeds in order to maintain adequate levels of the beneficial fatty acids, eicosapentaenoic and docosahexaenoic (EPA and DHA, respectively). The present study investigated the use of an EPA+DHA oil derived from a transgenic Camelina sativa in feeds for Atlantic salmon (Salmo salar) containing low levels of fishmeal (35 %) and fish oil (10 %), reflecting current commercial formulations, to determine the impacts on intestinal transcriptome, tissue fatty acid profile and health of farmed salmon. Post-smolt Atlantic salmon were fed for 12-weeks with one of three experimental diets containing either a blend of fish oil/rapeseed oil (FO), wild-type camelina oil (WCO) or transgenic camelina oil (DCO) as added lipid source. The DCO diet did not affect any of the fish performance or health parameters studied. Analyses of the mid and hindgut transcriptomes showed only mild effects on metabolism. Flesh of fish fed the DCO diet accumulated almost double the amount of n-3 LC-PUFA than fish fed the FO or WCO diets, indicating that these oils from transgenic oilseeds offer the opportunity to increase the n-3 LC-PUFA in farmed fish to levels comparable to those found twelve years ago.
Project description:Vegetable oils (VO) are possible substitutes for fish oil in aquafeeds but are limited by their lack of omega-3 (n-3) long-chain polyunsaturated fatty acids (LC-PUFA). However, oilseed crops can be modified to produce n-3 LC-PUFA such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, representing a potential option to fill the gap between supply and demand of these important nutrients. Camelina sativa was metabolically engineered to produce a seed oil with around 15 % total n-3 LC-PUFA to potentially substitute for fish oil in salmon feeds. Post-smolt Atlantic salmon (Salmo salar) were fed for 11-weeks with one of three experimental diets containing either fish oil (FO), wild-type Camelina oil (WCO) or transgenic Camelina oil (DCO) as added lipid source to evaluate fish performance, nutrient digestibility, tissue n-3 LC-PUFA, and metabolic impact determined by liver transcriptome analysis. The DCO diet did not affect any of the performance or health parameters studied and enhanced apparent digestibility of EPA and DHA compared to the WCO diet. The level of total n-3 LC-PUFA was higher in all the tissues of DCO-fed fish than in WCO-fed fish with levels in liver similar to those in fish fed FO. Endogenous LC-PUFA biosynthetic activity was observed in fish fed both the Camelina oil diets as indicated by the liver transcriptome and levels of intermediate metabolites such as docosapentaenoic acid, with data suggesting that the dietary combination of EPA and DHA inhibited desaturation and elongation activities. Expression of genes involved in phospholipid and triacylglycerol metabolism followed a similar pattern in fish fed DCO and WCO despite the difference in n-3 LC-PUFA contents.