Profiling Phospholipids within Atlantic Salmon Salmo salar with Regards to a Novel Terrestrial Omega-3 Oil Source

The development and inclusion of novel oils derived from genetically modified (GM) oilseeds into aquafeeds, to supplement and supplant current terrestrial oilseeds, as well as fish oils, warrants a more thorough investigation into lipid biochemical alterations within finfish species, such as Atlantic salmon. Five tissues were examined across two harvesting timepoints to establish whether lipid isomeric alterations could be detected between a standard commercial diet versus a diet that incorporated the long-chain polyunsaturated fatty acids (LC-PUFA), EPA (eicosapentaenoic acid), and DHA (docosahexaenoic acid), derived from the GM oilseed Camelina sativa. Tissue-dependent trends were detected, indicating that certain organs, such as the brain, have a basal limit to LC-PUFA incorporation, though enrichment of these fatty acids is possible. Lipid acyl alterations, as well as putative stereospecific numbering (sn) isomer alterations, were also detected, providing evidence that GM oils may modify lipid structure, with lipids of interest providing a set of targeted markers by which lipid alterations can be monitored across various novel diets

Effect of salinity on the biosynthesis of n-3 long-chain polyunsaturated fatty acids in silverside Chirostoma estor

The genus Chirostoma (silversides) belongs to the family Atherinopsidae, which contains around 150 species, most of which are marine. However, Mexican silverside (Chirostoma estor) is one of the few representatives of freshwater atherinopsids and is only found in some lakes of the Mexican Central Plateau. However, studies have shown that C. estor has improved survival, growth and development when cultured in water conditions with increased salinity. In addition, C. estor displays an unusual fatty acid composition for a freshwater fish with high docosahexaenoic acid (DHA) : eicosapentaenoic acid (EPA) ratios. Freshwater and marine fish species display very different essential fatty acid metabolism and requirements and so the present study investigated long-chain polyunsaturated fatty acid (LC-PUFA) biosynthesis to determine the capacity of C. estor for endogenous production of EPA and DHA, and the effect that salinity has on these pathways. Briefly, C. estor were maintained at three salinities (0, 5 and 15 ppt) and the metabolism of 14C-labelled 18:3n-3 determined in isolated hepatocyte and enterocyte cells. The results showed that C. estor has the capacity for endogenous biosynthesis of LC-PUFA from 18-carbon fatty acid precursors, but that the pathway was essentially only active in saline conditions with virtually no activity in cells isolated from fish grown in freshwater. The activity of the LCPUFA biosynthesis pathway was also higher in cells isolated from fish at 15 ppt compared to fish at 5 ppt, The pathway was around 5-fold higher in hepatocytes compared to enterocytes, although the majority of 18:3n-3 was converted to 18:4n-3 and 20:4n-3 in hepatocytes whereas the proportions of 18:3n-3 converted to EPA and DHA were higher in enterocytes. The data were consistent with the hypothesis that conversion of EPA to DHA could contribute, at least in part, to the generally high DHA:EPA ratios observed in the tissue lipids of C. estor

Comparative Fatty Acid Composition of Eggs from White Bass Fed Live Food or Commercial Feed

We evaluated the influence of two broodstock feeding practices on fatty acid composition and viability of eggs in white bass Morone chrysops. The two dietary groups tested were (1) white bass females fed a commercially formulated feed (crude protein, 45%; crude fat, 16%) and (2) white bass females maintained on live food (fathead minnow Pimephales promelas and golden shiners Notemigonus crysoleucas). Significant differences existed between the dietary treatments in egg fatty acid levels. Eggs of white bass fed live food contained more 11-octadecenoic acid (18:1[n-7]), α-linolenic acid (18:3[n-3]), arachidonic acid (20:4[n-6]), docosahexaenoic acid (22:6[n-3]), and total n-3 fatty acids than eggs of fish fed formulated feed. Conversely, eggs of fish fed the formulated feed contained more oleic acid (18:1[n-9]), linoleic acid (18:2[n-6]), and total monoeic acids. Female white bass fed live food produced significantly more viable eggs (68.0 ± 2.0%) at 48 ± 2 h posthatch than did females fed the commercial feed (57.0 ± 2.0% [mean ± SD]). We found that the egg fatty acids of white bass are significantly affected by the diet of the female and suggest that the fatty acid composition of eggs contribute to overall reproductive success and viability of progeny. More information on the nutrient requirements of piscivorous broodstock is needed to allow feeds to be formulated to enhance the viability of eggs and fry

Risk assessment of the use of alternative animal and plant raw material resources in aquaculture feeds

A wide range of raw materials are now used routinely in aquaculture feeds throughout the world, primarily to supply protein and energy in the form of lipid from edible oils. Protein meals and oils used can generally be divided into those of plant or animal origin and many have considerable potential to supply the required dietary nutrients required by aquaculture species. However, the use of any raw material introduces a suite of risks that need to be considered to enable the production of safe, sustainable and functional feeds to underpin this sector. A lack of understanding of some of those risks can result in failure of dietary specifications being met and/or negative nutritional elements being introduced (e.g. antinutritional factors). Importantly, it is this feed that when fed to food‐producing animals is such an important element of food safety, and as such any undesirable aspects relating to feed production can also have a negative impact on the rest of the food chain. However, there is some disparity internationally among raw materials that are used and the perceptions surrounding the risk of their use. It is the scientific assessment of these risks that is the basis of this review

Investigation of highly unsaturated fatty acid metabolism in the Asian sea bass, Lates calcarifer

Lates calcarifer, commonly known as the Asian sea bass or barramundi, is an interesting species that has great aquaculture potential in Asia including Malaysia and also Australia. We have investigated essential fatty acid metabolism in this species, focusing on the endogenous highly unsaturated fatty acid (HUFA) synthesis pathway using both biochemical and molecular biological approaches. Fatty acyl desaturase (Fad) and elongase (Elovl) cDNAs were cloned and functional characterization identified them as ∆6 Fad and Elovl5 elongase enzymes, respectively. The ∆6 Fad was equally active towards 18:3n-3 and 18:2n-6, and Elovl5 exhibited elongation activity for C18-20 and C20-22 elongation and a trace of C22-24 activity. The tissue profile of gene expression for ∆6 fad and elovl5 genes, showed brain to have the highest expression of both genes compared to all other tissues. The results of tissue fatty acid analysis showed that the brain contained more docosahexaenoic acid (DHA, 22:6n-3) than flesh, liver and intestine. The HUFA synthesis activity in isolated hepatocytes and enterocytes using [1-14C]18:3n-3 as substrate was very low with the only desaturated product detected being 18:4n-3. These findings indicate that L. calcarifer display an essential fatty acid pattern similar to other marine fish in that they appear unable to synthesize HUFA from C18 substrates. High expression of ∆6 fad and elovl5 genes in brain may indicate a role for these enzymes in maintaining high DHA levels in neural tissues through conversion of 20:5n-3

A detailed NMR study of the solution stereodynamics in tricarbonylrhenium(I) halide complexes of the non-racemic chiral ligand 2,6-bis[(4R,5R)-4,5-dimethyl-1,3-dioxolan-2-yl]pyridine (L¹) and the molecular structure of fac-[ReBr(CO)₃(L¹)]

1 Tricarbonylrhenium(I) halide complexes of the non-racemic chiral ligand 2,6-bis[(4R, 5R)-dimethyl-1,3-dioxan-2-yl]pyridine (L¹), namely fac-[ReX(CO)₃(L¹)] (X = Cl, Br or I), have been prepared. In these complexes the ligand is bound in a bidentate fashion, with the N atom of the pyridine ring and an O atom of one of the acetal rings co-ordinated to the octahedral metal centre. The bidentate mode is confirmed by the X-ray structure of fac-[ReBr(CO)₃(L¹)]. There are four possible diastereoisomers, depending on the configuration at the metal centre and at the acetal-carbon atom of the co-ordinated ring; the X-ray structure of fac-[ReBr(CO)₃(L¹)] shows that the SR diastereoisomer is present in the solid state. In solution, three of the four possible diastereoisomers are observed, namely SR, RR and RS; their relative populations are in the order SR > RR > SS. Above ambient temperature the complexes are stereochemically non-rigid. The fluxional kinetics have been measured by a combination of standard band shape analysis and selective inversion experiments. Two distinct processes are present: an acetal ring flip and exchange of the pendant and co-ordinated acetal rings. The latter process occurs via two independent mechanisms, namely tick-tock and rotation pathways. The activation energies for the stereodynamics are in the ranges 72 – 73 kJ mol⁻¹ (tick-tock), 77 – 78 kJ mol⁻¹ (acetal ring flip) and 83 – 90 kJ mol⁻¹ (rotation) at 298 K

Heritability and mechanisms of n-3 long chain polyunsaturated fatty acid deposition in the flesh of Atlantic salmon

N-3 long chain polyunsaturated fatty acids (n-3LC-PUFA) are essential components of vertebrate membrane lipids and are crucially deficient in modern Western diets. The main human dietary source for n-3LC-PUFA is fish and seafood, particularly oily fish and over 50% of global fish production is currently supplied by aquaculture. However, increasing pressure to include vegetable oils, which are devoid of n-3LC-PUFA, in aquaculture feeds reduces the content of these crucial nutrients in farmed fish flesh. The aim of this study was to measure the heritability and infer mechanisms determining flesh n-3LC-PUFA content in Atlantic salmon. This was achieved by analysing flesh lipid parameters in 48 families of Atlantic salmon, and by measuring differences in hepatic mRNA expression in families with high and low flesh n-3LC-PUFA. The results show that flesh n-3LC-PUFA level is a highly heritable trait (h2 = 0.77±0.14) and indicate the involvement of increased lipid transport, most likely in the form of very low density lipoprotein (VLDL) from liver. This increase in lipid transport may be associated with increased activity of a transcription factor, hepatic nuclear factor 4α (HNF4α), possibly as a result of family differences in transforming growth factor β1 (Tgfβ1) signalling. This study paves the way for identification of quantitative trait loci and gene interaction networks that are associated with levels of n-3LC-PUFA in fish flesh. Such markers can be used to assist the sustainable production of Atlantic salmon and provide optimal levels of critical nutrients for human consumers

Mass Production of Lemna minor and Its Amino Acid and Fatty Acid Profiles

The surface floating duckweed Lemna minor (Lemnaceae) is a potential ingredient to replace the application of fish-meal in the aqua-feed. The culture technique of the duckweed was standardized in outdoor tanks and then applied in the pond. Three consecutive experiments were conducted in tanks (1.2 × 0.35 × 0.3 m). In experiment 1, four different manures were used. In manure 1 (organic manure, OM) and manure 3 (2x OM), cattle manure, poultry droppings, and mustard oil cake (1:1:1) were used; in manure 2 (inorganic fertilizer, IF), urea, potash, triple superphosphate were used; manure 4 (2x OM+IF) was a combination of manure 2 and manure 3. In experiment 2, manure 1 (OM) and manure 2 (IF) were used, and manure 3 (OM+IF) was a combination of both manures. In experiment 3, OM and IF were selected. In pond (20 × 10 × 0.5 m), OM was applied. Fresh duckweed was seeded after 5 days of manure application. In experiments 1 and 3, total production was significantly (P 0.05) difference in production between OM and IF. In pond, relative growth rate (RGR) of duckweed ranged from 0.422 to 0.073 g/g/day and total production was 702.5 Kg/ha/month (dry weight). Protein, lipid, and ash contents were higher in duckweed cultured in OM compared to IF. The duckweed was a rich source of essential (39.20%), non-essential (53.64%), and non-proteinogenic (7.13%) amino acids. Among essential amino acids, leucine, isoleucine, and valine constituted 48.67%. Glutamic acid was 25.87% of total non-essential amino acids. Citrulline, hydroxiproline, taurine, etc. were found in the duckweed. The fatty acid composition was dominated by PUFA, 60–63% of total fatty acids, largely α-linolenic acid (LNA, 18:3n-3) at around 41 to 47% and linoleic acid (LA, 18:2n-6) at 17–18%. The nutritional value of duckweeds and their production potential in the pond conditions were evaluated. Duckweed biomass may thus be used to replace commercial fish-meal that is currently used in aquaculture