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1.
Changes in fatty acid metabolism in Atlantic salmon (Salmo salar) induced by vegetable oil (VO) replacement of fish oil (FO) and high dietary oil in aquaculture diets can have negative impacts on the nutritional quality of the product for the human consumer, including altered flesh fatty acid composition and lipid content. A dietary trial was designed to investigate the twin problems of FO replacement and high energy diets in salmon throughout the entire production cycle. Salmon were grown from first feeding to around 2 kg on diets in which FO was completely replaced by a 1:1 blend of linseed and rapeseed oils at low (14–17%) and high (25–35%) dietary oil levels. This paper reports specifically on the influence of diet on various aspects of fatty acid metabolism. Fatty acid compositions of liver, intestinal tissue and gill were altered by the diets with increased proportions of C18 polyunsaturated fatty acids and decreased proportions of n-3 highly unsaturated fatty acids (HUFA) in fish fed VO compared to fish fed FO. HUFA synthesis in hepatocytes and enterocytes was significantly higher in fish fed VO, whereas β-oxidation was unaltered by either dietary oil content or type. Over the entire production cycle, HUFA synthesis in hepatocytes showed a decreasing trend with age interrupted by a large peak in activity at seawater transfer. Gill cell prostaglandin (PG) production showed a possible seasonal trend, with peak activities in winter and low activities in summer and at seawater transfer. PG production in seawater was lower in fish fed the high oil diets with the lowest PG production generally observed in fish fed high VO. The changes in fatty acid metabolism induced by high dietary oil and VO replacement contribute to altered flesh lipid content and fatty acid compositions, and so merit continued investigation to minimize any negative impacts that sustainable, environmentally-friendly and cost-effective aquaculture diets could have in the future. Abbreviations: FO - fish oil; HUFA - highly unsaturated fatty acids acids (carbon chain length ≥C 20 with ≥3 double bonds); LO - linseed oil; RO - rapeseed oil; VO - vegetable oil. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

2.
To study how hepatic lipid turnover and lipid transport may be affected by complete replacement of dietary fish oil (FO) with a vegetable oil blend (VO) from start feeding until the adult stages, Atlantic salmon (Salmo salar L.) were fed either 100% FO‐ or 100% VO‐based diets (55% rapeseed oil, 30% palm oil and 15% linseed oil) from start feeding until 22 months. Liver and plasma lipoprotein lipid class levels and lipoprotein fatty acid composition were analysed through the seawater phase, whereas liver fatty acid composition, plasma cholesterol, triacylglycerol (TAG) and protein levels were analysed through both freshwater and seawater stages. Further, enzyme activity of liver fatty acid synthetase (FAS), NADH‐isocitrate dehydrogenase, malic enzyme, glucose‐6‐phosphate dehydrogenase and 6‐phosphogluconate dehydrogenase and expression of the gene Peroxisome proliferator‐activated receptor γ (PPARγ) was analysed during both fresh water and seawater stages through the experiment. Dietary VO significantly increased salmon liver TAG and hence total liver lipid stores after 14 and 22 months of feeding. Further, after 22 months of feeding, plasma lipid levels and plasma low‐density lipoprotein (LDL) levels were significantly decreased in VO‐fed salmon compared with FO‐fed fish. The same trend, although not statistically significant, was seen for plasma very low‐density lipoprotein (VLDL). The activity of FAS was generally low throughout the experiment with the VO group having significantly lower activity after 16 months of feeding. The expression of PPARγ in livers increased prior to seawater transfer followed by a decrease, and then another increase towards the final sampling (22 months). Dietary vegetable oil replacement had no impact on PPARγ expression in salmon liver. In summary, liver TAG stores, plasma lipid and LDL levels were affected by dietary vegetable oil replacement in Atlantic salmon during a long–term feeding experiment. Current results indicate that high dietary vegetable oil inclusion increase hepatic TAG stores and decrease plasma lipid levels possible through decreased VLDL synthesis.  相似文献   

3.
Duplicate groups of three genetic strains of Atlantic salmon smolts were cultured on diets containing either fish oil (FO) or a blend of vegetable oils (VO). Fatty acid compositions of liver and peripheral blood leucocytes were compared. The effect of different strains and diets on innate immune parameters and plasma prostaglandin E2 were also measured. Two strains were selected as being either 'fat' or 'lean' in terms of muscle adiposity. The third strain was a commercial stock (MH). Total replacement of dietary FO with VO resulted in reduced docosahexaenoic (DHA; 22:6 n -3) and eicosapentaenoic acids (EPA; 20:5 n -3) in liver, while oleic (18:1 n -9), linoleic (18:2 n -6) and α-linolenic (18:3 n -3) acids were all increased in VO-fed fish. Fatty acid compositions of blood leucocytes showed similar changes. Evaluation of innate immune function showed that in the fat strain, circulating leucocytes were significantly lower in VO fish. The lean strain also had significantly higher serum lysozyme activity than MH fish. Reduced haematocrit was seen in VO lean fish compared with FO lean fish. This study provides evidence of strain-induced differences in liver and leucocyte fatty acid compositions and innate immunity in Atlantic salmon fed either FO- or VO-based diets.  相似文献   

4.
Copepod oil (CO) from the marine zooplankton, Calanus finmarchicus, is a potential alternative to fish oils (FOs) for inclusion in aquafeeds. The oil is composed mainly of wax esters (WE) containing high levels of saturated fatty acids (SFAs) and monounsaturated fatty alcohols that are poorly digested by fish at low temperatures. Consequently, tissue lipid compositions may be adversely affected in salmon‐fed CO at low temperatures. This study examined the lipid and FA compositions of muscle and liver of Atlantic salmon reared at two temperatures (3 and 12 °C) and fed diets containing either FO or CO, supplying 50% of dietary lipid as WE, at two fat levels (~330 g kg?1, high; ~180 g kg?1, low). Fish were acclimatized to rearing temperature for 1 month and then fed one of four diets: high‐fat fish oil (HFFO), high‐fat Calanus oil (HFCO), low‐fat fish oil (LFFO) and low‐fat Calanus oil (LFCO). The fish were grown to produce an approximate doubling of initial weight at harvest (220 days at 3 °C and 67 days at 12 °C), and lipid content, lipid class composition and FA composition of liver and muscle were determined. The differences in tissue lipid composition between dietary groups were relatively small. The majority of FA in triacylglycerols (TAG) in both tissues were monounsaturated, and their levels were generally higher at 3 °C than 12 °C. Polyunsaturated fatty acids (PUFA), particularly (n‐3) PUFA, predominated in the polar lipids, and their level was not significantly affected by temperature. The PUFA content of TAG was highest (~26%) in the muscle of fish fed the HFCO diet at both temperatures. Tissue levels of SFAs were lower in fish‐fed diets containing HFCO than those fed HFFO, LFFO or LFCO, particularly at 3 °C. The results are consistent with Atlantic salmon being able to incorporate both the FA and fatty alcohol components of WE into tissue lipids but, overall, the effects of environmental temperature on tissue lipids were more pronounced in fish fed the CO diets than FO diets.  相似文献   

5.
6.
An experiment was conducted to study dietary fat type (fish oil (FO) vs. vegetable oil) effect on lipid and glucose metabolism in post-smolt Atlantic salmon. Duplicate groups of salmon were fed one of eight diets in which the two fat sources FO (long chain n-3 fatty acids, FA) or linseed oil (LO) (short chain n-3 FA) were combined in a 2 × 4 factorial design with sunflower oil (SO) (rich in n-6 FA) at inclusion levels of 0, 25, 50 and 75% of total added fat. The effects of the diets on plasma metabolites, the activity of selected enzymes involved in lipid metabolism, biometric indices and muscle glucose transporter GLUT4 expression were determined after 12 weeks of feeding. Lower viscero-somatic indices (VSI) and fatty livers were observed in fish fed LO based diets. Increasing inclusion levels of SO affected plasma glucose concentration in fish fed FO based diets, and plasma triglycerides, which decreased in a linear and quadratic pattern in fish fed FO based diets, but increased linearly in fish fed LO based diets. Specific activity of liver carnitine palmitoyl transferase I (CPT I) and glucose-6-phosphate dehydrogenase (G6PD) and plasma nonesterified fatty acids (NEFA) concentration was higher in fish fed LO based diets. Two GLUT4 isoforms I and II have been described in muscle and proved to be differentially expressed related to dietary fatty acids. In summary, dietary fat type affects lipid metabolism in post-smolted Atlantic salmon. In addition, a possibility to interfere on glucose metabolism by means of dietary fat type is discussed.  相似文献   

7.
In order to investigate the capacities of different tissues to oxidize fatty acids, total β-oxidation (mitochondrial and peroxisomal) of [1–14C]palmitoyl-CoA was determined in liver and red- and white muscle from adult and juvenile Atlantic salmon Salmo salar. By including potassium cyanide (KCN) in the assay medium, it was possible to differentiate between mitochondrial and peroxisomal β-oxidation capacities. Mitochondrial β-oxidation dominated in all tissues except in livers from juvenile fish where the peroxisomal β-oxidation dominated. In general, the red muscle possesses the highest fatty acid oxidation capacity, however, by taking into consideration the fact that white muscle occupies approximately 60% of the total body weight, this study demonstrates that the white muscle is an important tissue in the overall fatty acid catabolism.  相似文献   

8.
Adult Atlantic salmon (Salmo salar; approximately 800 g start weight) were fed diets with a high replacement of fish meal (FM) with plant proteins (70% replacement), and either fish oil (FO) or 80% of the FO replaced by olive oil (OO), rapeseed oil (RO) or soybean oil (SO) during 28 weeks in triplicate. Varying the lipid source only gave non‐significant effects on growth and final weight. However, a significantly reduced feed intake was observed in the SO fed fish, and both feed utilization and lipid digestibility were significantly reduced in the FO fed fish. Limited levels of dietary 18:3n‐3, precursor to EPA and DHA, resulted in no net production of EPA and DHA despite increased mRNA expression of delta‐5‐desaturase and delta‐6‐desaturase in all vegetable oil fed fish. Net production of marine protein, but not of marine omega‐3 fatty acids, is thus possible in Atlantic salmon fed 80% dietary vegetable oil and 70% plant proteins resulting in an estimated net production of 1.3 kg Atlantic salmon protein from 1 kg of FM protein. Production of one 1 kg of Atlantic salmon on this diet required only 800 g of wild fish resources (Fish in ‐ Fish out < 1).  相似文献   

9.
The major aim of the current study was to evaluate the effect of substituting fish oil (FO) for a vegetable oil blend (VO) as dietary lipid source on lipid catabolism in Atlantic salmon (Salmo salar L.). The experiment endured from the start of feeding until the salmon reached 2.5 kg. Total and peroxisomal β‐oxidation capacities were determined in red and white muscle and liver. In addition, fatty acid productive value (FAPV) was calculated during the four time periods the experiment was divided into. In all the three tissues, an increased β‐oxidation capacity was found prior to seawater transfer; however, calculating the difference between the peroxisomal β‐oxidation capacity and the total, the peroxisomal β‐oxidation increased more than the mitochondrial β‐oxidation capacity. Hence, in liver and red muscle, 100%and 70%, respectively, of the total β‐oxidation capacity was accounted by peroxisomes prior to seawater transfer, compared with approximately 60% and 3% during the seawater phase. In contrast, white‐muscle mitochondria was the main organelle responsible for oxidizing fatty acids during the entire experiment (>90%). However, during the period of high energy demand (parr‐smolt transformation), fish fed VO exhibited significantly lower β‐oxidation capacity than fish fed FO, coinciding with low FAPV and low specific growth rate (SGR). Further, during periods of high growth rate, fish oxidized even essential fatty acids (18:2n‐6, 18:3n‐3, 20:5n‐3, and 22:6n‐3) when given in surplus. Low dietary levels of essential fatty acids gave significantly higher FAPV of these fatty acids in the whole body. However, the FAPV of 22:1n‐11 was low, indicating that this fatty acid is highly utilized as a substrate for β‐oxidation, irrespective of the dietary levels. There were no differences in whole lipid content between fish fed either FO or VO.  相似文献   

10.
The desaturation and elongation of [1-14C]18:3n-3 was investigated in hepatocytes of the tropical warm freshwater species, zebrafish (Danio rerio) and Nile tilapia (Oreochromis niloticus). The hepatocyte fatty acid desaturation/elongation pathway was assayed before and after the fish were fed two experimental diets, a control diet containing fish oil (FO) and a diet containing vegetable oil (VO; a blend of olive, linseed and high oleic acid sunflower oils) for 10 weeks. The VO diet was formulated to provide 1% each of 18:2n-6 and 18:3n-3, and so satisfy the possible EFA requirements of zebrafish and tilapia. At the end of the dietary trial, the lipid and fatty acid composition was determined in whole zebrafish, and liver, white muscle and brain of tilapia. Both zebrafish and tilapia expressed a hepatocyte fatty acid desaturation/elongation pattern consistent with them being freshwater and planktonivorous fish. The data also showed that hepatic fatty acid desaturation/elongation was nutritionally regulated with the activities being higher in fish fed the VO diet compared to fish fed the FO diet. In zebrafish, the main effect of the VO diet was increased fatty acid Δ6 desaturase activity resulting in the production of significantly more 18:4n-3 compared to fish fed the FO diet. In tilapia, all activities in the pathway were greater in fish fed the VO diet resulting in increased amounts of all fatty acids in the pathway, but primarily eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3). However, the fatty acid compositional data indicated that despite increased activity, desaturation of 18:3n-3 was insufficient to maintain tissue proportions of EPA and DHA in fish fed the VO diet at the same level as in fish fed the FO diet. Practically, these results indicate that manipulation of tilapia diets in commercial culture in response to the declining global fish oil market would have important consequences for fish fatty acid composition and the health of consumers. Scientifically, zebrafish and tilapia, both the subject of active genome mapping projects, could be useful models for studies of lipid and fatty acid metabolism at a molecular biological and genetic level. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

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