[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: Oils extracted from the marine zooplankton, Calanus finmarchicus, have high levels of n-3 highly unsaturated fatty acids (HUFA) and are therefore of interest as an alternative lipid source in aquafeeds. Copepod lipid is composed mainly of wax esters (WE) with high levels of saturated fatty acids and monounsaturated fatty alcohols which are considered hard to digest, especially at low temperatures. This assumption has however not been verified and for this reason the present study examined the digestibility of diets containing high levels of WE and two fat levels in Atlantic salmon reared at 3 and 12 °C. The fish were acclimated for one month to 3 °C (485 g) and 12 °C (599 g) and then fed with one of four diets, high fat fish oil (33% lipid, HFFO), high fat Calanus oil (32% lipid, HFCO), low fat fish oil (17% lipid, LFFO) and low fat Calanus oil (19% lipid, LFCO). The fish meal lipid content was lowered by the use of lipid-extracted fish meal (2.3% lipid). This enabled a level of 50% WE in the LFCO and HFCO diets, compared to 0% in the LFFO and HFFO diets. The fish were then allowed to grow to around 100% of initial weight (220 days at 3 °C and 67 days at 12 °C) and then analysed for faecal lipid digestibility, bile volume, bile composition and intestinal lipolytic activity. Differences were observed in all of these parameters in relation to temperature, type of dietary oil and the lipid level in the diet. Faecal lipid content and lipid class composition were dependent on rearing temperature and the type of dietary lipid. Highest levels of undigested lipids were observed in the faeces of fish fed with CO. Wax ester-derived fatty alcohols, particularly 20:1n-9 and 22:1n-11, were less extensively digested than corresponding fatty acids from FO at both fat levels and temperatures. Fish kept at 12 °C had a significantly higher bile volume than fish at 3 °C and higher volumes were found in fish fed with CO diets compared to FO. Increased faecal holding time at lower temperature was not sufficient to ensure high digestibility since the lower bile volume and enzyme activities at 3 °C in the present trial exerted a greater effect. Although the compensatory mechanisms of increased bile volume and lipolytic activity are initiated upon feeding WE at a level of 50% of dietary lipid, these are not sufficient to compensate lipid digestibility and growth as in FO diets. Low inclusion of CO in diets during winter has to be considered as saturated fatty acids and monounsaturated fatty alcohols were poorly digested at 3 °C in fish fed with CO diets.
[Show abstract][Hide abstract] ABSTRACT: The present study compared the effects of diets formulated with reduced fishmeal (FM) content and either 100% fish oil (FO) or 100% of a vegetable oil (VO) blend in post-smolts of three family groups of Atlantic salmon. Two groups were selected as being either “Lean” or “Fat” based on estimated breeding values (EBV) for flesh adiposity of their parents derived from a breeding programme, while the third group (CAL) was a mix of non-pedigreed commercial families unrelated to the two groups above. The VO blend comprised rapeseed, palm and a new product, Camelina oil in a ratio of 5/3/2, and diets were fed to duplicate pens of each salmon group. After an ongrowing period of 55 weeks, to reach a mean weight of 3kg, the fish from all treatments were switched to a decontaminated FO for a further 24 weeks to follow restoration of long-chain n-3 polyunsaturated fatty acids (LC-PUFA) in the fish previously fed VO. Final weights were significantly affected by family group and there was also an interaction between diet and group with Fat and Lean FO fish being larger than the same fish fed VO. Specific growth rate (SGR) was highest in CAL fish (1.01), feed conversion ratio (FCR) was highest in the Lean fish but there were no significant effects on thermal growth coefficient (TGC). Condition Factor (CF) was lowest in CAL fish while the hepato-somatic index (HSI) was highest in Lean fish and viscero-somatic index (VSI) highest in Fat fish. Flesh and viscera lipid content was affected by both family group and diet with a significant interaction between the two. Flesh lipid in fish fed FO was in the order Fat > CAL > Lean although this order was Fat = Lean > CAL when fed VO. Flesh fatty acid compositions were affected mainly by diet although some minor fatty acids were also influenced by group. Fish fed VO had n-3 LC-PUFA reduced by ~65% compared to fish fed FO but this could be restored by a 16 week FO finishing diet phase. The differences observed in lipid and fatty acid deposition suggested that genetics affected lipid deposition and metabolism and that breeding programmes could select for fish that retained more n-3 LC-PUFA in their flesh, particularly when fed diets low in these fatty acids.
[Show abstract][Hide abstract] ABSTRACT: Calanoid copepods are a rich source of marine lipid for potential use in aquafeeds. Copepod oil is primarily composed of wax esters (WE) and there are concerns over the efficiency of wax ester, versus triacylglycerol (TAG), digestion and utilization in fish. As smoltification represents a period of major physiological adaptation, the present study examined the digestibility of a high WE diet (Calanus oil; 48% WE, 26% TAG), compared with a TAG diet (fish oil; 58% TAG), in Atlantic salmon freshwater presmolts and seawater postsmolts, of similar age (9 months) and weight (112 g and 141 g initial, respectively), over a 98-day period at constant temperature. Fish grew significantly better, and possessed lower feed conversion ratios (FCR), in seawater than freshwater. However, total lipid apparent digestibility coefficient (ADC) values were significantly lower in seawater fish, as were total fasted bile volumes. Dietary Calanus oil also had a significant effect, reducing growth and lipid ADC values in both freshwater and seawater groups. Postsmolts fed dietary Calanus oil had the poorest lipid ADC values and analysis of faecal lipid class composition revealed that 33% of the remaining lipid was WE and 32% fatty alcohols. Dietary prevalent 22:1n-11 and 20:1n-9 fatty alcohols were particularly poorly utilized. A decrease in primary bile acid, taurocholate, concentration was observed in the bile of dietary Calanus oil groups which could be related to the lower cholesterol content of the diet. The dietary WE : TAG ratio is discussed in relation to life stage and biliary intestinal adaptation to the seawater environment postsmoltification.
[Show abstract][Hide abstract] ABSTRACT: Several transmethylation procedures have been used for fatty acid analysis of aquatic organisms although the suitability of the applied procedures has rarely been tested. The aim of this study was to demonstrate how different derivatization procedures can affect the result of fatty acid analysis. Different transmethylation procedures based on the acidic catalysts boron trifluoride, concentrated sulphuric acid and anhydrous hydrochloric acid were applied to cold-pressed copepod oil and Atlantic salmon flesh lipids rich in wax esters and triacylglycerols, respectively. The results show that 1) the use of unsuitable catalysts and/or incubation conditions may influence the data obtained which can lead to inaccurate conclusions about the presence of fatty acids in aquatic organisms/ecosystems 2) different derivatization procedures based on the same catalyst can produce diverging results and 3) the efficiency of a selected catalyst/procedure should be verified (e.g. by thin-layer chromatography) to ensure the complete transmethylation of fatty acids.
[Show abstract][Hide abstract] ABSTRACT: Total lipid content, fatty acid (FA) composition and lipid class composition of common dentex eggs spawned at different times and larvae reared under different culture conditions until 40 days posthatch (dph) were analysed to get a general pattern of lipid composition during larval development. Two groups of larvae were kept under starvation to compare their FA composition with that obtained from normally fed larvae. To compare FA use or accumulation during larval development, results were grouped according to the developmental stage of the larvae instead of age in days posthatch. Saturated and monounsaturated FAs decreased along larval development, while polyunsaturated fatty acid (PUFA) content increased. The ratio of docosahexaenoic acid (DHA)/eicosapentaenoic acid shifted from 4 to 5 in early developmental stages to lower than 1 after metamorphosis. Arachidonic acid levels remained constant along larval development. Larvae kept 6 days under starvation consumed most of their n-3 PUFA while conserving the DHA to values at day 0. The results presented here are useful for the design of nutritional experiments, because there were differences detected in terms of lipid and FA composition between developmental stages with higher differences mainly found in first-feeding larvae and early developmental stages.
[Show abstract][Hide abstract] ABSTRACT: Recent legislation in the European Union (EC/2065/2001) requires that seafood must provide the consumer with information that describes geographical origin and production method. The present studies aimed to establish methods, based on chemical and stable isotopic analysis, that could reliably differentiate between wild and farmed European sea bass (Dicentrarchus labrax). The study measured fatty acid and isotopic compositions (delta13C and delta18O) of total flesh oil, delta15N of the glycerol/choline fraction, and compound-specific analysis of fatty acids (delta13C) by isotope ratio mass spectrometry. The sample set comprised 10 wild and 10 farmed sea bass from England (wild) and Scotland or Greece (farmed). Discrimination was achieved using fatty acid composition with 18:0, 18:2n-6, 20:4n-6, and 22:6n-3 providing the highest contributions for discrimination. Principal component analysis of the data set provided good discrimination between farmed and wild sea bass where factor 1 and factor 2 accounted for 60% of the variation in the data.
Journal of Agricultural and Food Chemistry 08/2007; 55(15):5934-41. · 2.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Dietary conjugated linoleic acid (CLA) affects fat deposition and lipid metabolism in mammals, including livestock. To determine CLA effects in Atlantic salmon (Salmo salar), a major farmed fish species, fish were fed for 12 weeks on diets containing fish oil or fish oil with 2% and 4% CLA supplementation. Fatty acid composition of the tissues showed deposition of CLA with accumulation being 2 to 3 fold higher in muscle than in liver. CLA had no effect on feed conversion efficiency or growth of the fish but there was a decreased lipid content and increased protein content after 4% CLA feeding. Thus, the protein:lipid ratio in whole fish was increased in fish fed 4% CLA and triacylglycerol in liver was decreased. Liver beta-oxidation was increased whilst both red muscle beta-oxidation capacity and CPT1 activity was decreased by dietary CLA. Liver highly unsaturated fatty acid (HUFA) biosynthetic capacity was increased and the relative proportion of liver HUFA was marginally increased in salmon fed CLA. CLA had no effect on fatty acid Delta6 desaturase mRNA expression, but fatty acid elongase mRNA was increased in liver and intestine. In addition, the relative compositions of unsaturated and monounsaturated fatty acids changed after CLA feeding. CLA had no effect on PPARalpha or PPARgamma expression in liver or intestine, although PPARbeta2A expression was reduced in liver at 4% CLA feeding. CLA did not affect hepatic malic enzyme activity. Thus, overall, the effect of dietary CLA was to increase beta-oxidation in liver, to reduce levels of total body lipid and liver triacylglycerol, and to affect liver fatty acid composition, with increased elongase expression and HUFA biosynthetic capacity.
Comparative Biochemistry and Physiology - Part A Molecular & Integrative Physiology 11/2006; 145(2):258-67. · 2.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The preparation of fish oil concentrates containing only (n-3) polyunsaturated fatty acids (PUFA) with different ratios of 20:5 (n-3)/22:6 (n-3) is described. Three groups of turbot were maintained on different diets containing: 1, 10% of the dry weight of the diet as natural fish oil, equivalent to 2.5% (n-3) PUFA and 0–23% (n-6) PUFA; 2, 10% of the dry weight of the diet as palmitic acid, i.e. no PUFA; 3, 8–7% palmitic acid and 1–3% of the dry weight as (n-3 PUFA and negligible (n-6) PUFA. Only the fish on the diet containing natural fish oil showed significant growth over a 15-week period. In addition there were high mortalities on the two experimental diets (2 and 3). Changing the ratio of 20:5 (n-3)/22:6 (n-3) from 13–8 to 2–2 in the diet containing 1 3% (n-3) PUFA and negligible (n-6) PUFA markedly decreased the mortalities. Fish fed the two experimental diets (2 and 3) developed gross changes in gill structure involving the disappearance of chloride cells, a ‘sloughing off’ of the epithelium along the primary and secondary filaments and an accumulation of cellular material in the inter-lamellar spaces. The tissue ultimately disintegrated to leave a skeleton of connective tissue and a mass of cellular material in the inter-lamellar spaces. It is concluded that 22:6 (n-3) is an essential fatty acid for turbot and that the gill epithelium is a sensitive indicator of this deficiency in this species.
Journal of Fish Biology 01/2006; 26(2):181 - 191. · 1.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The spawning quality, in terms of hatching rate, larval mortality at 3 and 5 days post-hatching (dph) and day of total mortality of two
broodstock groups of common dentex was evaluated for 1 month in 2005. Several biochemical parameters including total lipid content,
lipid class and fatty acid composition, carbohydrate content and metabolic enzyme activities were analysed in all the egg batches
collected. Comparison was carried out between low- (mortality at 3 dph higher than 35%) and high-quality (mortality at 3 dph lower than
10%) batches. No differences were observed in lipid content and/or lipid class and fatty acid composition although a slightly higher
content of neutral lipids was detected in high-quality batches. However, significant differences were obtained regarding carbohydrate
composition and the activity of enzymes such as alkaline phosphatase and pyruvate kinase being higher in low-quality egg batches.
[Show abstract][Hide abstract] ABSTRACT: Atlantic salmon (Salmo salar L.) juveniles were fed either 100% fish oil (FO), 75% vegetable oil (VO), or 100% VO throughout their life cycle to harvest weight followed by a finishing diet period when all groups were fed 100% FO. The two experimental VO diets were tested at two different locations (Scotland and Norway) against the same control diet (100% FO). The VO blend was composed of rapeseed oil, palm oil, and linseed oil using capelin oil as a control for fatty acid class compositions. Flesh fatty acid profiles were measured regularly throughout the experiment, with the times of sampling determined by changes in pellet size/lipid content and fish life stage. Growth and mortality rates were not significantly affected by dietary fatty acid compositions throughout the life cycle, except during the seawater winter period in Norway when both growth and protein utilization were increased in salmon fed 100% VO compared to 100% FO. Flesh fatty acid composition was highly influenced by that of the diet, and after the finishing diet period the weekly intake recommendations of very long chain n-3 polyunsaturated fatty acid (VLCn-3 PUFA) for human health were 80 and 56% satisfied by a 200 g meal of 75% VO and 100% VO flesh, respectively. No effect on flesh astaxanthin levels was observed in relation to changing dietary oil sources. Sensory evaluation showed only minor differences between salmon flesh from the dietary groups, although prior to the finishing diet period, flesh from 100% VO had less rancid and marine characteristics and was preferred over flesh from the other dietary groups by a trained taste panel. After the finishing diet period, the levels of typical vegetable oil fatty acids in flesh were reduced, whereas those of VLCn-3 PUFA increased to levels comparable with a 100% FO fed salmon. No differences in any of the sensory characteristics were observed between dietary groups. By blending VOs to provide balanced levels of dietary fatty acids, up to 100% of the fish oil can be replaced by the VO blend without compromising growth or flesh quality. At the same time, 75% of the dietary fish oil can be replaced without compromising flesh VLCn-3 PUFA content, thereby providing a beneficial nutritional profile for human consumption.
Journal of Agricultural and Food Chemistry 01/2006; 53(26):10166-78. · 2.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Highly unsaturated fatty acid (HUFA) synthesis in Atlantic salmon (Salmo salar) was known to be influenced by both nutritional and environmental factors. Here we aimed to test the hypothesis that both these effectors involved similar molecular mechanisms. Thus, HUFA biosynthetic activity and the expression of fatty acyl desaturase and elongase genes were determined at various points during an entire 2 year production cycle in salmon fed diets containing either 100% fish oil or diets in which a high proportion (75% and 100%) of fish oil was replaced by C18 polyunsaturated fatty acid-rich vegetable oil. The results showed that HUFA biosynthesis in Atlantic salmon varied during the growth cycle with peak activity around seawater transfer and subsequent low activities in seawater. Consistent with this, the gene expression of Delta6 desaturase, the rate-limiting step in the HUFA biosynthetic pathway, was highest around the point of seawater transfer and lowest during the seawater phase. In addition, the expression of both Delta6 and Delta5 desaturase genes was generally higher in fish fed the vegetable oil-substituted diets compared to fish fed fish oil, particularly in the seawater phase. Again, generally consistent with this, the activity of the HUFA biosynthetic pathway was invariably higher in fish fed diets in which fish oil was substituted by vegetable oil compared to fish fed only fish oil. In conclusion, these studies showed that both nutritional and environmental modulation of HUFA biosynthesis in Atlantic salmon involved the regulation of fatty acid desaturase gene expression.
Biochimica et Biophysica Acta 06/2005; 1734(1):13-24. · 4.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Primary hepatocytes from wild northern pike Esox lucius were incubated with radiolabelled linolenic acid ([l-14C]-18:3(n-3)) to assess their ability to synthesize docosahexaenoic acid [22:6(n-3)]. The distribution of radioactivity in lipid classes and hepatocyte polyunsaturated fatty acids (PUFA) was measured over the time-course of 24h. The majority of radioactivity from [l-14C]-18:3(n-3) was recovered in hepatocyte triacylglycerols (TAG) and phosphatidylcholine (PC). The levels of radioactivity in TAG and in most of phospholipids, including PC, increased significantly over the incubation period. Radioactivity from [1-14C]-18:3(n-3) was recovered in several hepatocyte PUFA, including 22:6(n-3), and the Δ6 and Δ5-desaturation products 18:4(n-3) and 20:5(n-3). The presence of radioactivity in C24 (n-3) PUFA may be evidence that the biosynthesis of 22:6(n-3) in pike proceeds via a pathway independent of Δ4-desaturation. Analysis by radio gas chromatography revealed that radiolabelled 24:6(n-3) was present among the desaturation and elongation products of [l-14C]-18:3(n-3). The results establish that, under the in vitro conditions employed, pike hepatocytes are able to convert linolenic acid to 20:5(n-3) and 22:6(n-3).
Journal of Fish Biology 03/2005; 51(6):1197 - 1208. · 1.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The lipid composition of two species of Serrasalmid fish with different natural feeding habits were compared in relation to the polyunsaturated fatty acids (PUFA) supplied in their diets. Mylossoma aureum, a herbivorous piranha, was maintained on oatmeal flakes in which : 2(n-6) and : 3(n-3) were the only PUFA and accounted for 40–8 and 1.2%, respectively of dietary fatty acids. Serrasalmus nattereri, the carnivorous red piranha, was fed mosquito larvae containing .0-33.4% of their total fatty acids as : 2(n-6)+18 : 3(n-3) and 4.9-8.5% as 20 : 4(n-6)+20 : 5(n-3). The two species had similar lipid class compositions in liver, brain, viscera and carcass, except that lipids from M. aureum were generally richer in triacylglycerols. In both species, visceral and carcass lipid contained high levels of triacylglycerols whose principal PUFA was : 2(n-6). In M. aureum the major PUFA in liver total lipid and triacylglycerols was : 2(n-6) whilst the major PUFA in liver phospholipids were : 4(n-6) and : 5(n-6), with : 6(n-3) being a minor component. The level of : 6(n-3) in ethanolamine glycerophospholipids was significantly greater in brain than liver of M. aureum. Although absent from dietary lipid, : 6(n-3) was the major PUFA in phosphatidylcholine and ethanolamine glycerophospholipids from both the liver and brain of S, nattereri. In both species, the ratio of (n-6)/(n-3)PUFA was consistently lower in tissue lipids than in dietary lipids. The results are consistent with (i) the herbivorous M. aureum converting dietary C18 PUFA to their C20 and C22 homologues, (ii) the carnivorous S, nattereri forming : 6(n-3) from either 18:3(n-3) or 20: 5(n-3) and (iii) both species selectively desaturating and elongating (n-3) rather than (n-6) PUFA.
Journal of Fish Biology 03/2005; 48(3):522 - 538. · 1.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Five groups of salmon, of initial mean weight 127 +/- 3 g, were fed increasing levels of dietary linseed oil (LO) in a regression design. The control diet contained capelin oil (FO) only, and the same oil was blended with LO to provide the experimental diets. After an initial period of 40 wk, all groups were switched to a finishing diet containing only FO for a further 24 wk. Growth and flesh lipid contents were not affected by dietary treatment. The FA compositions of flesh total lipids were linearly correlated with dietary FA compositions (r2 = 0.88-1.00, P < 0.0001). LO included at 50% of added dietary lipids reduced flesh DHA and EPA (20:5n-3) concentrations to 65 and 58%, respectively, of the concentrations in fish fed FO. Feeding 100% LO reduced flesh DHA and EPA concentrations to 38 and 30%, respectively, of the values in fish fed FO. Differences between diet and flesh FA concentrations showed that 16:0, 18:1n-9, and especially DHA were preferentially retained in flesh, whereas 18:2n-6, 18:3n-3, and 22:1n-11 were selected against and presumably utilized for energy. In fish previously fed 50 and 100% LO, feeding a finishing diet containing FO for 16 wk restored flesh DHA and EPA concentrations, to approximately 80% of the values in fish fed FO throughout. Flesh DHA and EPA concentrations in fish fed up to 50% LO were above recommended intake values for humans for these EFA. This study suggests that LO can be used as a substitute for FO in seawater salmon feeds and that any reductions in DHA and EPA can be largely overcome with a finishing diet high in FO before harvest.
[Show abstract][Hide abstract] ABSTRACT: Against a background of decreasing availability of fish oils for use in aquaculture, the present study was undertaken to examine whether a wax ester-rich oil derived from the calanoid copepod Calanus finmarchicus, could be used effectively by Atlantic salmon when supplied in their diet. Individually tagged Atlantic salmon of initial weight around 500 g were divided into replicate tanks of two dietary groups and fed either a fish oil supplemented diet, or an experimental diet coated with Calanus oil. Wax esters accounted for 37.5% of the lipids in the Calanus oil diet but were absent from the fish oil diet in which triacylglycerols (TAG) were the major lipid class. Over the feeding period (140 days) the salmon fed fish oil displayed a greater increase in length, but there was no significant difference between the two groups in weight gained. The specific growth rates (0.75) and the feed conversion ratio of fish fed the two diets were similar throughout the study. No differences were observed in the apparent digestibility coefficients (ADC) of fish fed Calanus oil or fish oil. The ADC of fatty acids decreased with chain length and increased with unsaturation. Long-chain alcohol utilization showed a similar tendency although there was a notable difference in that saturated long-chain alcohols were utilized better than the comparable fatty acid homologue. In fecal lipid of fish fed Calanus oil, the content of 16:0 alcohol decreased in both the free long-chain alcohol and wax ester fractions, while the corresponding fatty acid increased in the feces of both dietary groups of fish. In contrast, the proportion of the 22:1n−11 alcohol increased in both fecal wax esters and free long-chain alcohol fractions whereas 22:1n−11 fatty acid displayed no accumulation. The observed patterns of fatty acid and long-chain alcohol compositions in fecal lipid compared to those of the initial dietary lipid are consistent with the digestive lipases of salmon preferentially hydrolyzing esters containing polyunsaturated fatty acid (PUFA) moieties. The wax esters of Calanus oil contained substantial amounts of the n−3 PUFA, 20:5n−3 and 22:6n−3, that were effectively deposited in muscle and liver tissues. No major differences were seen in either lipid content/lipid classes or in gross fatty acid composition of these tissues between the two dietary groups. It is concluded that that Atlantic salmon in seawater can effectively utilize diets in which a major lipid component is derived from zooplankton rich in wax ester without any detrimental change in growth or body lipid composition. This finding gives support to the use of lipid from zooplankton from high latitudes as an alternative or as a supplement to fish oil and a provider of long-chain n−3 PUFA in diets for use in salmon aquaculture.
[Show abstract][Hide abstract] ABSTRACT: The influence of feeding high levels of polyunsaturated fatty acids (PUFA) on muscle fatty acid composition and indices of oxidative damage was examined in Arctic charr, Salvelinus alpinus (L.). All diets contained 100 g kg−1 lipid of dry weight. Two diets contained marine fish oils giving a PUFA level of 250 g kg−1 and 500 g kg−1 of lipid. The remaining two diets contained vegetable oils high in either 18:2n-6 or 18:3n-3, giving a PUFA level of more than 500 g kg−1 of dietary lipid. The charr were maintained at 8°C until their weight doubled, and were then transferred to 0.8°C for 30 days. Growth was similar in all groups. The fatty acid compositions of muscle were influenced by dietary PUFA but were less diverse than those of the diets. The overall pattern of fatty acid compositions indicated preferential desaturation and elongation of n-3 PUFA coupled with selective oxidation of 18:2n-6. Total n-3 PUFA content in TAG was always lowered compared with the diet, suggesting a specific mechanism for the removal of these fatty acids. Subjecting the fish to low temperature increased PUFA content in muscle of charr fed the 250 g kg−1 marine n-3 PUFA diet, but had no effect on the other treatments. For fish at 8°C, no significant differences were found between groups in terms of haematocrit, plasma alanine aminotransferase (ALAT), and plasma and muscle thiobarbituric acid reactive substances (TBARS), although there was a tendency towards increased levels of TBARS in the group receiving 500 g kg−1 marine n-3 PUFA of lipid. Subjecting the muscle to forced oxidative conditions resulted in increases in TBARS in all groups, particularly those fed 500 g kg−1 marine n-3 PUFA. Lowering the environmental temperature corresponded with a further increase in the plasma ALAT and muscle TBARS in this group. It is concluded that feeding diets containing high levels of long-chain n-3 PUFA may be detrimental to the fish's health and flesh quality, particularly at low environmental temperatures.
[Show abstract][Hide abstract] ABSTRACT: Atlantic salmon postsmolts were fed a control diet or one of 9 experimental diets containing various blends of two vegetable oils, linseed (LO) and rapeseed oil (RO), and fish oil (FO) in a triangular trial design, for 50 wk. After sampling, fish previously fed 100% FO, LO and RO were switched to a diet containing 100% FO for a further 20 wk. Fatty acid compositions of flesh total lipid were linearly correlated with dietary fatty acid compositions (r = 0.99-1.00, P < 0.0001). Inclusion of vegetable oil at 33% of total oil significantly reduced the concentrations of the highly unsaturated fatty acids, eicosapentaenoate [20:5(n-3)] and docosahexaenoate [22:6(n-3)], to approximately 70 and 75%, respectively, of the values in fish fed 100% FO. When vegetable oil was included at 100% of total dietary lipid, the concentrations of 20:5(n-3) and 22:6(n-3) were significantly reduced to approximately 30 and 36%, respectively, of the values in fish fed FO. Transfer of fish previously fed 100% vegetable oil to a 100% FO diet for 20 wk restored the concentrations of 20:5(n-3) and 22:6(n-3) to approximately 80% of the value in fish fed 100% FO for 70 wk, although the values were still significantly lower. However, in fish previously fed either 100% LO or RO, concentrations of 18:2(n-6) remained approximately 50% higher than in fish fed 100% FO. This study suggests that RO and LO can be used successfully to culture salmon through the seawater phase of their growth cycle; this will result in reductions in flesh 20:5(n-3) and 22:6(n-3) concentrations that can be partially restored by feeding a diet containing only marine FO for a period before harvest.
Journal of Nutrition 09/2003; 133(9):2793-801. · 4.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The present study was undertaken to establish whether the formation of 22:6n-3 from 18:3n-3 and/or 20:5n-3 can occur in turbot liver and if this conversion is consistent with the operation of a Delta4 desaturase-independent pathway. At the same, time the effects of feeding a diet devoid of long chain polyunsaturated fatty acids (PUFA) on the patterns of esterification and modification of 18:3n-3, 20:5n-3 and 18:2n-6 by turbot hepatocytes and liver microsomes were examined. For this purpose, two groups of fish (25-30 g) were employed: one was fed a commercial diet containing fish oil (FO) and thus rich in long chain n-3 PUFA and the other was fed an experimental diet based on olive oil (OO). After 5 months of feeding, hepatocytes and liver microsomes isolated from individuals in the two groups of fish were incubated with [1-(14)C]-PUFA [either 18:3n-3, 20:5n-3 or 18:2n-6]. After 3 h of incubation, most radioactivity from all three radiolabelled substrates incorporated into lipids by hepatocytes and microsomes was recovered in the original substrate. The formation of desaturation products of n-3 radiolabelled substrates was higher in hepatocytes isolated from OO-fed than FO-fed fish. Small amounts of radiolabelled 22:6n-3 were formed from [1-(14)C]18:3n-3 and [1-(14)C]20:5n-3, but only by hepatocytes from fish fed OO, which also synthesised a small amount of radiolabelled 24:6n-3 from 14C-20:5n-3. Elongation products predominated over desaturation products in hepatic microsomes from both groups of fish studied, particularly in microsomes from fish fed FO. The results confirm that regardless of the long chain PUFA content of the diet, the production of 22:6n-3 in turbot liver from 18:3n-3 and/or 20:5n-3, and of 20:4n-6 from 18:2n-6, is very limited. The presence of radiolabelled 24:6n-3 in microsomes coupled with the absence of radiolabelled 22:6n-3 suggests that the formation of 22:6n-3 that does occur in turbot liver cells, may involve C24 intermediates and peroxisomal beta-oxidation.
Comparative Biochemistry and Physiology Part B Biochemistry and Molecular Biology 08/2002; 132(3):559-70. · 2.07 Impact Factor