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1.
Three practical-type diets utilizing fishmeal and casein as the protein sources and containing fish oil (FO), safflower oil (SO) or linseed oil (LO) were fed to duplicate groups of juvenile turbot (Scophthalmus maximus) of initial weight 1.2 g for a period of 12 weeks. No differences in final weight, mortality or development of pathological lesions were evident either between duplicate tanks or between dietary treatments over this period. Fish fed diets containing SO and LO contained significantly greater amounts of liver triacylglycerol compared to fish fed FO. The major C18 polyunsaturated fatty acids (PUFA) in SO and LO diets, 18:2(n-6) and 18:3(n-3) respectively, were readily incorporated into both total lipid and individual phospholipids of turbot tissues. There was no accumulation of the Δ6-desaturation products of these fatty acids, namely 18:3(n-6) and 18:4(n-3), in any of the tissues examined. The products of elongation of 18:2(n-6) and and 18:3(n-3), 20:2(n-6) and 20:3(n-3) respectively, accumulated in both total lipid and phospholipids with the highest levels of 20:2(n-6) in liver PC and 20:3(n-3) in liver PE. Eicosapentaenoic acid [EPA, 20:5(n-3)] levels exceeded those of arachidonic acid [AA, 20:4(n-6)] in phosphatidylinositol (PI) from liver and gill of fish fed LO. EPA levels in liver PI from fish fed LO were 3-fold and 2-fold greater than SO-fed and FO-fed fish, respectively. Fish fed diets containing SO and LO had significantly reduced levels of AA in liver and muscle total lipid and lower AA in individual phospholipid classes of liver and gill compared to FO-fed fish. The concentration of thromboxane B2 was significantly reduced in plasma and isolated gill cells stimulated with calcium ionophore A23187 of fish fed SO and LO compared to those fed FO. Prostaglandin E produced by isolated gill cells stimulated with A23187 was significantly reduced in fish fed both SO and LO compared to fish fed FO.  相似文献   

2.
The static or declining supply of fish oil from industrial fisheries demands the search of alternatives, such as plant (vegetable) oils, for diets in expanding marine aquaculture. Vegetable oils are rich in C18 polyunsaturated fatty acids but devoid of the n-3 highly unsaturated fatty acids in fish oils. Previous studies, primarily with salmonids, have shown that including vegetable oils in their diets increased hepatocyte fatty acid desaturation. In the present study, we have investigated the effects of dietary partial substitution of fish oil (FO) with rapeseed oil (RO), linseed oil (LO) and olive oil (OO) on the desaturation /elongation and, -oxidation capacities of [1-14C]18:3n-3 in isolated hepatocytes from European sea bass (Dicentrarchus labrax L.), in a simultaneous combined assay. Fish were fed during 34 weeks with diets containing 100% FO, or RO, LO and OO, each included at 60% with the balance being met by FO, with no detrimental effect upon growth or survival. The highest total desaturation rates were found in hepatocytes of fish fed FO diet (0.52±0.08 pmol/h/mg protein) and OO diet (0.43±0.09 pmol/h/mg protein), which represented 3.2% and 2.7% of total [1-14C]18:3n-3 incorporated, respectively. In contrast, lowest desaturation rates were presented by hepatocytes of fish fed LO and RO diets (0.23±0.06 and 0.14±0.05 pmol/h/mg protein, respectively) represented 1.4% and 0.9% of total [1-14C]18:3n-3 incorporated, respectively. The rates of [1-14C]18:3n-3 β-oxidized were between 11-fold and 35-fold higher than desaturation. However, no significant differences were observed among β-oxidation activities in hepatocytes of fish fed any of the diets. The present study demonstrated that the European sea bass, as a carnivorous marine fish, presented a ‘marine’ fish pattern in the metabolism of 18:3n-3 to 20:5n-3 and 22:6n-3. This species appeared to have all the enzymic activities necessary to produce 22:6n-3 but presented only extremely low rates of fatty acid bioconversion. Furthermore, nutritional regulation of hepatocyte fatty acid desaturation was minimal, and dietary vegetable oils did not increase desaturase activities, and in RO and LO treatments the activity was significantly lower. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

3.
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   

4.
The aim of this study was to investigate the effects of different oils on growth performance and lipid metabolism of the grouper, Epinephelus coioides. Five experimental fish meal‐based isonitrogenous and isolipidic diets were formulated containing either 5.5%‐added fish oil (FO), soybean oil (SBO), corn oil (CO), sunflower oil (SFO) or peanut oil (PO). Each diet was fed to triplicate groups of 20 fish (initial body weight 13.2±0.02 g) grown in seawater at 28.0–30.5 °C for 8 weeks. Fish were fed twice a day to visual satiety. No significant differences in the survival, weight gain, specific growth rate, feed conversion ratio, protein efficiency ratio or hepatosomatic index were found between fish fed the FO or vegetable oils (VO) diets. Dietary lipid sources did not affect whole‐body composition among grouper fed the various diets. Muscle of fish fed the FO diet had significantly higher levels of 14:0, 16:0, 16:1n‐7, 20:5n‐3[eicosapentaenoic acid (EPA)] and docosahexaenoic acid (DHA)+EPA (except for PO fed fish) compared with those of fish fed VO diets. However, the levels of 18:1n‐9, 18:2n‐6 and DHA/EPA ratios in the muscle of fish fed FO diet were significantly lower than those of fish fed the VO diets. The liver of fish fed the FO diet had significantly higher levels of 18:0, 20:5n‐3, 22:6n‐3, n‐3 highly unsaturated fatty acids and DHA+EPA than those of fish fed the VO diets, whereas increases in 18:1n‐9, 18:2n‐6 and mono‐unsaturated fatty acid levels were observed in the liver of fish fed the VO diets.  相似文献   

5.
The effects of different lipids on tissue fatty acid profile and reproductive performance in female rice field eel were investigated in this study. Virgin female eels were fed with six diets containing different lipids (diets FO, LO, SO, PO and PL with fish oil, linseed oil, soybean oil, peanut oil and pork lard, respectively; diet APO with arachidonic acid and peanut oil). The results showed that there were positive correlations between the contents of 18:2n-6, 18:3n-3, arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the tissues of eels and those of the corresponding fatty acids in their diets. The specific growth rate of eels fed with diet PO was the lowest and significantly lower than that of FO and SO. Gonad of eels fed with diets PO and PL showed hypogonadism. The long chain polyunsaturated fatty acids (LC-PUFA) can be synthesized by eels, but the quantity was not enough to meet their reproduction requirement completely. The fatty acid desaturation, rather than elongation probably was one of the limiting factors. Addition of proper amount of ARA in diet was favorable to the increase of the hatching rate of fertilized eggs, while EPA and DHA in diet were beneficial to the increase of the survival rate of larva. Both n-3PUFA and a suitable n-6/n-3PUFA ratio were necessary for growth and reproduction of eels.  相似文献   

6.
Replacement of fish oil with sustainable alternatives, such as vegetable oil, in aquaculture diets has to be achieved without compromising the nutritional quality, in terms of n-3 highly unsaturated fatty acid (HUFA) content, of the product. This may be possible if the level of replacement is not too high and oil blends are chosen carefully but, if high levels of fish oil are substituted, a fish oil finishing diet prior to harvest would be required to restore n-3HUFA. However, a decontaminated fish oil would be required to avoid increasing undesirable contaminants. Here we test the hypotheses that blending of rapeseed and soybean oils with southern hemisphere fish oil will have a low impact upon tissue n-3HUFA levels, and that decontamination of fish oil will have no major effect on the nutritional quality of fish oil as a feed ingredient for Atlantic salmon. Salmon (initial weight ~ 0.8 kg) were fed for 10 weeks with diets in which 60% of fish oil was replaced with blends of soybean, rapeseed and southern hemisphere fish oil (SVO) or 100% decontaminated northern fish oil (DFO) in comparison with a standard northern fish oil diet (FO). Decontamination of the oil was a two-step procedure that included treatment with activated carbon followed by thin film deodorisation. Growth performance and feed efficiency were unaffected by either the SVO or DFO diets despite these having lower gross nutrient and fatty acid digestibilities than the FO diet. There were also no effects on the gross composition of the fish. Liver and, to a lesser extent flesh, lipid levels were lower in fish fed the SVO blends, due to lower proportions of neutral lipids, specifically triacylglycerol. Tissue lipid levels were not affected in fish fed the DFO diet. Reflecting the diet, flesh eicosapentaenoic acid (EPA) and total n-3 fatty acids were higher, and 18:1n-9 lower, in fish fed DFO than FO, whereas there were no differences in liver fatty acid compositions. Flesh EPA levels were only slightly reduced from about 6% to 5% although docosahexaenoic acid (DHA) was reduced more severely from around 13% to about 7% in fish fed the SVO diets. In contrast, the liver fatty acid compositions showed higher levels of n-3 HUFA, with DHA only reduced from 21% to about 18% and EPA increased from under 8% to 9–10% in fish fed the SVO diets. The evidence suggested that increased liver EPA (and arachidonic acid) was not simply retention, but also conversion of dietary 18:3n-3 and 18:2n-6. Increased HUFA synthesis was supported by increased hepatic expression of fatty acyl desaturases in fish fed the SVO diets. Flesh n-3HUFA levels and desaturase expression was significantly higher in fish fed soybean oil than in fish fed rapeseed oil. In conclusion, partial replacement of fish oil with blends of vegetable oils and southern hemisphere fish oil had minimal impact on HUFA levels in liver, but a greater effect on flesh HUFA levels. Despite lower apparent digestibility, decontamination of fish oil did not significantly impact its nutritional quality for salmon.  相似文献   

7.
This study evaluated the effects of fish oil (FO) replacement by vegetable oils [soybean oil (SO), rapeseed oil (RO), linseed oil (LO)] and subsequent feeding with FO on the liver morphology of sea bream. A short-term trial (3 months) and long-term trial (6 months) were carried out feeding sea bream with the following experimental diets: FO100%; SO60% + FO40%; RO60% +FO40%; LO60% + FO40%; SO + RO +LO60% + FO40%. Finally, all groups from the long-term trial were fed with FO100% for 95 days (washout period). Liver samples were taken for histological and biochemical studies. In both the short- and long-term trials, livers of sea bream fed LO60% and SO + RO + LO60% showed a similar hepatic morphology to that observed in fish fed FO100%. In contrast, sea bream fed SO60% showed an intense steatosis, with foci of swollen hepatocytes containing numerous lipid vacuoles. After the washout period, a considerable reduction of the cytoplasmic vacuolation and the lipid vacuole accumulation were observed in the livers of fish fed the different experimental diets. The results of this study suggested that the type of non-essential fatty acid, characteristic of vegetable oils, induces the appearance of steatosis in the following order: linoleic acid > linolenic acid > oleic acid. However, the liver alterations found during the experimental periods with vegetable oils are reversible when the fish are re-fed with a balanced diet (FO100%), indicating the non-pathological character of these histological changes.  相似文献   

8.
Atlantic salmon (Salmo salar) were fed diets containing fish oil supplemented with 22:6n-3 (FO diet) or linseed oil supplemented with 20:5n-3 (LO diet) for 6 months. The effects of these diets, both containing about 36% n-3 fatty acids, on the esterification, desaturation and elongation of [1-14C] 18:2n-6 and [1-14C] 18:3n-3 were investigated in isolated hepatocytes. The percentages of radioactivity which was esterified from [1-14C] 18:2n-6 or [1-14C]18:3n-3 into total lipids, were approximately 20% lower in hepatocytes from fish fed the FO diet than in hepatocytes from fish fed the LO diet. The percentages of radioactivity esterified in both groups were further reduced when 0.1 mM unlabelled 22:6n-3 was added to the incubation. The percentage of desaturation and elongation products formed from [1-14C] 18:2n-6 was twice as high in hepatocytes from salmon fed the FO diet as it was in hepatocytes from fish fed the LO diet. The ratio of 18:2n-6 to 18:3n-3 was five times higher in the FO diet, and this probably promoted the conversion of 18:2n-6 to longer chain n-6 fatty acids. When 0.1mM unlabelled 22:6n-3 was added to the incubation medium, the percentages of desaturation and elongation products formed were unchanged. Thus, a high level of 22:6n-3 in the diet is apparently not inhibiting the conversion of 18:2n-6 to 20:4n-6, as long as the amount of 18:2n-6 present is substantially higher than that of 18:3n-3. No desaturation and elongation products were recovered from the phospholipids of hepatocytes incubated with [1-14C] 18:3n-3 in any of the groups. However, the `dead end' elongation product 20:3n-3 was found in the triacylglycerol fraction, and the percentage of this fatty acid increased when 22:6n-3 was added to the incubation medium.  相似文献   

9.
The objective of this work was to determine whether highly unsaturated fatty acid (HUFA) synthesis and fatty-acid oxidation in Atlantic salmon (Salmo salar L.) intestine was under environmental and/or seasonal regulation. Triplicate groups of salmon were grown through a full two-year cycle on two diets containing either fish oil (FO) or a diet with 75% of the FO replaced by a vegetable oil (VO) blend containing rapeseed, palm, and linseed oils. At key points in the life cycle fatty acyl desaturation/elongation (HUFA synthesis) and oxidation activity were determined in enterocytes and hepatocytes using [1−14C]18:3n−3 as substrate. As observed previously, HUFA synthesis in hepatocytes reached a peak at seawater transfer and declined thereafter, with activity consistently greater in fish fed the VO diet. In fish fed FO, HUFA synthesis in enterocytes in the freshwater stage was at a level similar to that in hepatocytes. HUFA synthesis in enterocytes increased rapidly after seawater transfer, however, and remained high for some months after transfer before decreasing to levels that were again similar to those observed in hepatocytes. Enterocyte synthesis of HUFA was usually higher in fish fed the VO diet than in those fed the FO diet. Oxidation of [1−14C]18:3n−3 in hepatocytes from fish fed FO tended to decrease during the freshwater phase but then increased steeply, peaking just after transfer before decreasing during the remaining seawater phase. At the peak in oxidation activity around seawater transfer, activity was significantly lower in fish fed VO than in fish fed FO. In enterocytes, oxidation of [1−14C]18:3 in fish fed FO reached a peak in activity just before seawater transfer. In fish fed VO, except for high activity at nine months the pattern was similar to that obtained in enterocytes from fish fed FO, with high activity around seawater transfer and declining activity in seawater. In conclusion, fatty acid metabolism in intestinal cells seemed to be under dual nutritional and environmental or seasonal regulation. Temporal patterns of oxidation of fatty acids were usually similar in the two cell types, but HUFA synthesis in enterocytes peaked over the summer seawater phase rather than at transfer, as with hepatocytes, suggesting the possibility of different regulatory cues.  相似文献   

10.
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   

11.
Duplicate groups of Atlantic salmon were fed one of four practical-type diets from first feeding to harvest after 115 weeks. The four diets were low fish oil (17% w/w, LFO), high fish oil (35% w/w, HFO), low vegetable oil (17%, linseed oil [LO]/rapeseed oil [RO], 1:1 w/w; LVO) and high vegetable oil (35%, linseed oil/rapeseed oil, 1:1 w/w; HVO). Following sample collection (average weight 2.1 kg), all groups were switched to the HFO diet for a further 24 weeks. The dioxin concentration in diets was in order HFO>LFO>LVO>HVO, with values ranging from 0.16 to 1.4 ng TEQ/kg. The dioxin-like polychlorinated biphenyl (DL-PCB) concentrations were in the same order with values ranging from 0.62 to 3.68 ng TEQ/kg. Concentrations of dioxins and DL-PCBs in flesh samples were correlated with feed concentrations, but values in flesh were always lower than in feed. Flesh dioxin concentrations ranged from 0.10 to 0.53 ng TEQ/kg and DL-PCBs from 0.58–1.48 ng TEQ/kg. After 24 weeks feeding a fish oil-containing finishing diet (HFO), the flesh dioxin concentrations ranged from 0.20 to 0.54 ng TEQ/kg and the DL-PCBs from 0.66 to 1.07 ng TEQ/kg. Feeding the HVO diet resulted in significant reductions in flesh concentrations of 20:5 n-3 (EPA) and 22:6 n-3 (DHA) to around 25% of the values in fish fed the HFO diet. However, feeding the HFO finishing diet for 24 weeks resulted in restoration of flesh EPA and DHA concentrations to 80% of the values in fish fed the HFO diet throughout. Feeding the finishing diet resulted in significantly increased dioxin levels in flesh of fish previously fed the LFO, LVO and HVO diets, although values were still significantly lower than in fish fed the HFO diet throughout. This study suggests that salmon cultured on diets based on fish meal and oil (HFO) attain flesh dioxin concentrations that are <14% of the current European Commission limit. However, by replacing marine fish oils with vegetable oils for most of the production cycle, dioxin and DL-PCB concentrations can be substantially reduced.  相似文献   

12.
Triplicate groups of European sea bass (Dicentrarchus labrax L.), of initial weight 90 g, were fed four practical‐type diets in which the added oil was 1000 g kg?1 fish oil (FO) (control diet), 600 g kg?1 rapeseed oil (RO) and 400 g kg?1 FO, 600 g kg?1 linseed oil (LO) and 400 g kg?1 FO, and 600 g kg?1 olive oil (OO) and 400 g kg?1 FO for 34 weeks. After sampling, the remaining fish were switched to the 1000 g kg?1 FO diet for a further 14 weeks. Fatty acid composition of flesh total lipid was influenced by dietary fatty acid input but specific fatty acids were selectively retained or utilized. There was selective deposition and retention of docosahexaenoic acid (DHA; 22:6n‐3). Eicosapentaenoic acid (EPA; 20:5n‐3) and DHA were significantly reduced and linolenic (LNA; 18:3n‐3), linoleic (LA; 18:2n‐6) and oleic (OA; 18:1n‐9) acids significantly increased in flesh lipids following the inclusion of 600 g kg?1 RO, LO and OO in the diets. No significant differences were found among different treatments on plasma concentrations of prostaglandin E2 and prostaglandin F2α. Evaluation of non‐specific immune function, showed that the number of circulating leucocytes was significantly affected (P < 0.001), as was macrophage respiratory burst activity (P < 0.006) in fish fed vegetable oil diets. Accumulation of large amounts of lipid droplets were observed within the hepatocytes in relation to decreased levels of dietary n‐3 HUFA, although no signs of cellular necrosis was evident. After feeding a FO finishing diet for 14 weeks, DHA and total n‐3 HUFA levels were restored to values in control fish although EPA remained 18% higher in control than in the other treatments. This study suggests that vegetable oils such as RO, LO and OO can potentially be used as partial substitutes for dietary FO in European sea bass culture, during the grow out phase, without compromising growth rates but may alter some immune parameters.  相似文献   

13.
Due to its traditionally good availability, digestibility and high content of n ? 3 HUFA, fish oil is the main lipid source in fish feeds. However, world demand for this product has grown significantly in recent years, whereas its production, based on fisheries landings, is static. The purpose of the present study was to assess the effect of partial replacement of fish oil in compound diets for gilthead seabream and seabass, by several vegetable oil sources, on growth, dietary fatty acid utilization and flesh quality. Five iso‐energetic and isoproteic experimental diets were formulated (25% lipid content). Fish oil was the only added lipid source in the control (FO) diet, and it was included in the other experimental diets at a level high enough (40% of FO diet) to keep the n ? 3 HUFA levels well over 3% in order to cover the essential fatty acid requirements of these species. Fish oil was replaced by soyabean oil (SO), rapeseed oil (RO) and linseed oil (LO) or a mixture (Mix) of them. Feed intake in all dietary groups was in the range of results obtained for commercial diets in both species, and growth and feed utilization were very good. The results show that, providing a minimum content of essential fatty acids in the diet, it is possible to replace up to 60% of the fish oil by SO, LO and RO or a mixture of them in diets for seabream and seabass, without compromising fish growth. Fatty acid composition of liver and muscle reflected that of the diet, but utilization of dietary lipids differed between these two tissues and was also different for the different fatty acids. Despite reduction in dietary saturated fatty acids by the inclusion of vegetable oils, their levels in fish liver were as high as in fish fed the fish oil diet, whereas, in muscle, levels were reduced according to that in the diet. Linoleic and linolenic acids were accumulated in the liver proportionally to their levels in the diet, suggesting a lower oxidation of these fatty acids in comparison to other 18C fatty acids. Regarding eicosapentaenoic acid (20 : 5n ? 3; EPA), docosahexaenoic acid (22 : 6n ? 3; DHA) and arachidonic acid (20 : 4n ? 6; ARA), these essential fatty acids were reduced in the liver at a similar rate, whereas DHA was preferentially retained in the muscle in comparison with the other fatty acids, denoting a higher oxidation particularly of EPA, in the muscle. Some other PUFA increased despite their low dietary levels in seabream fed LO diets and in seabass fed SO diet, suggesting the stimulation of delta‐6 and delta‐5 desaturase activity in marine fish. Despite differences in fatty acid composition, fillet of fish fed vegetable oils was very well accepted by trained judges when assessed cooked.  相似文献   

14.
Three diets in which the lipid component was supplied either as fish oil (FO), linseed oil (LO) or olive oil (OO) were fed to duplicate groups of juvenile turbot (Scophthalmus maximus) of initial weight 1.2 g for a period of up to 12 weeks. The latter two diets resulted in a significant reduction in specific growth rate and an increased mortality compared to the FO (control) fed fish. A liver histopathology was evident in around half of the fish fed the LO and OO diets but was absent in fish fed FO. The lesion showed indications of cellular alterations consisting of foci of densely basophilic cells but without evidence of inflammatory activity. The total lipid fatty acid composition of the carcass from fish fed LO had increased percentages of 18:2n-6 and 18:3n-3, but decreased percentages of all other polyunsaturated fatty acids (PUFA) including the physiologically important 20:4n-6, 20:5n-3 and 22:6n-3, compared to fish fed FO. Almost 2/3 of the total fatty acids in the carcass of OO-fed fish were monounsaturated while the percentages of total saturated fatty acids and all other PUFA, except 18:2n-6, were significantly reduced compared to fish fed FO. Broadly similar effects on total lipid fatty acid composition were observed in liver. In the liver glycerophospholipid classes of fish fed LO, percentages of 18:2n-6, 18:3n-3 and 20:3n-3 were significantly increased whereas all C20 and C22 PUFA, with the exception of 20:5n-3 in PI, were significantly reduced compared to fish fed FO. The liver glycerophospholipids of fish fed OO all showed significantly increased total monounsaturates, 18:2n-6, 20:2n-6, 18:2n-9 and 20:2n-9 as well as reduced percentages of 20:4n-6 and 22:6n-3, compared to fish fed FO. The brain glycerophospholipids showed broadly similar changes in response to dietary treatment although the magnitude of fatty acid alterations was less than those observed in liver. The greater mortalities in the OO-fed fish compared to the LO-fed fish suggests that incorporation of 18:3n-3 into tissue phospholipids can offset losses of long-chain PUFA more effectively than incorporation of 18:1n-9. However, levels of dietary long-chain PUFA must be optimised to allow normal growth and development. We conclude that the very low flux through the fatty acid desaturase/elongase pathways in turbot is not up-regulated by diets deficient in 20:5n-3 and 22:6n-3.  相似文献   

15.
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   

16.
An 84‐day growth trial was designed to investigate effects of dietary replacements fish oil with pork lard (PL) or rapeseed oil (RO) on growth and quality of gibel carp (Carassius auratus gibelio var. CAS III) (initial body weight: 158.2 ± 0.2 g), and responses of the fish refed fish oil (FO) diet. Three isonitrogenous (crude protein: 30%) and isolipid (crude lipid: 10%) diets were formulated containing 7.73% FO, PL or RO. Five experimental treatments including FO group (FO), PL group (PL), RO group (RO), group fed PL for 42 days and refed FO for 42 days (PL+rFO), RO and refed FO group (RO+rFO) was tested. At the end of first 42 days, the fish fed PL and RO had higher mortality than that of the control (P > 0.05). At the end of whole experiment, fish fed PL and RO showed higher plasma cortisol than FO fish (P < 0.05). RO+rFO fish showed higher lysozyme activity than RO fish (P < 0.05). Fish growth and feed utilization, composition of whole body and muscle, free amino acids, texture, off‐flavour substances or sensory attributes were not affected by dietary treatments (P > 0.05). PL and RO diet decreased muscle EPA, DHA and n‐3/n‐6 ratio (P < 0.05), while FO‐refeeding had recovery effect. It can be concluded that the replacement of FO by PL and RO does not affect the growth, feed utilization or fish tasting quality in gibel carp. Fish muscle fatty acids modified by dietary PL and RO can be recovered by refeeding with FO diet.  相似文献   

17.
Four isonitrogenous (300 g kg?1 crude protein), isoenergetic (21 kJ g?1) experimental diets were formulated to contain fish oil (FO), soybean oil (SBO), crude palm oil (CPO) and linseed oil (LO), respectively, as the lipid sources, added at 120 g kg?1 of crude lipid each. The diets were fed by hand to triplicate groups of Pangasius nasutus (Bleeker, 1863) juveniles (mean weight 10.66 ± 0.04 g), to apparent satiation twice daily for 12 weeks. Fish survival rate was 100% among all the treatments. Growth performance (DGR) was similar among fish fed the SBO, CPO and LO diets, but was significantly (P < 0.05) higher in the CPO compared to fish fed the control (FO) diet. Fish fed SBO and CPO diets also recorded significantly (P < 0.05) higher intraperitoneal fat compared to fish fed the control, whereas fish fed the LO diet did not significantly differ from the other treatments. Muscle and liver fatty acid profile of fish from all the treatments generally mirrored the composition of the diets fed and the major fatty acids recorded were 18:3n‐3 and 18:2n‐6 in the tissues of fish fed the LO and SBO treatments, respectively. Results of this study suggests that P. nasutus fed diets containing vegetable oils (especially CPO and SBO) produce better growth performance, without compromising fish survival and feed efficiency compared with those fed a diet containing only FO.  相似文献   

18.
To investigate the impact of different dietary lipid sources on fillet composition and lipid transport, we conducted a feeding trial and evaluated the proximate composition of muscle tissue, fatty acid profiles, total cholesterol (in muscle and plasma), triglycerides, and lipoprotein concentrations in Nile tilapia, Oreochromis niloticus. Five semi‐purified diets, containing different oils (soybean – SO, corn – CO, linseed – LO, fish – FO, and olive – OO), were supplied to tilapia for 160 d. Fish fed with LO and FO diets had a lower percentage of total lipids in muscle compared with the others (P < 0.05). The highest percentage of protein was found in fish fed with FO diet (P < 0.05). The muscle fatty acid profile was influenced differently by diets (P < 0.05). The group supplemented with SO and CO had a higher concentration of 18:2n‐6, whereas the fish fed with LO diet had a higher level of 18:3n‐3 and those that received the FO diet had more 22:6n‐3 in comparison with those supplemented with vegetable oils. Plasma lipid transport was also affected by the diets: the fish fed with FO diet had higher total cholesterol and high‐density lipoprotein and lower very‐low‐density lipoprotein concentrations (P < 0.05).  相似文献   

19.
Increased use of plant oils with different origins and quality in fish feed needs to be approached from a food safety and fish welfare point of view. Plant oils contain a number of bioactive minor lipid compounds that may affect the fish’s metabolism and taste perception. This study focuses on the effect of replacing fish oil (FO) with different levels of cold‐pressed rapeseed oil (RO) on the lipid composition in muscle and liver as well as on the preference by the fish. Rainbow trout (Oncorhynchus mykiss) were fed diets with a FO : RO ratio of 100 : 0, 75 : 25, 50 : 50 and 25 : 75 until twofold weight increase. In self‐selecting feed trials of single rainbow trout, fish preferred the diet composed of only FO compared with the diets with RO but did not discriminate between different levels of RO. Plant sterols and their metabolites were found in liver of the fish fed RO diets, suggesting an effect on the sterol metabolism different from fish fed a 100% FO diet. The largest effects were seen in the fatty acid composition of the edible tissue of the fish with a decrease in 22:6n‐3 and 20:5n‐3 and an increase in 18:2n‐6 and 18:1n‐9.  相似文献   

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