Substitution Of Dietary Fish Oil Research Articles

AMPK activation by dietary acadesine improves fillet texture in large yellow croaker (Larimichthys crocea) fed a linseed oil-based diet

The impacts of AMP-activated protein kinase (AMPK) activation by dietary acadesine (AICAR) on growth performance and muscle quality of large yellow croaker (Larimichthys crocea) fed a linseed oil-based diet (LO) were investigated by a 56-day feeding trial in this study. Fish (initial weight: 92.24 ± 0.30 g) were fed fish oil-based diet (FO), LO or LA (LO diet supplemented with 150 mg kg−1 AICAR) with three replicates of each treatment. Results indicated that weight gain rate and specific growth rate (SGR) were significantly decreased in the LO and LA groups than those of the fish fed FO, while the opposite was true for the feed conversion ratio. Moreover, the SGR of fish fed LA was significantly lower than that of the LO group. Dietary linseed oil and AICAR significantly lowered muscle eicosapentaenoic acid and docosahexaenoic acid contents. Furthermore, the LO group showed significantly lower fillet hardness, chewiness and pH, while higher lipid loss than those of the FO group. However, the FO and LA groups had similar fillet hardness, lipid loss and pH. Compared with the fish fed FO and LA, the LO group possessed significantly lower p-AMPK protein level and p-AMPK/AMPK ratio in muscle. The phosphorylation of TOR protein and the ratios of p-TOR/TOR and p-S6/S6 were significantly decreased in muscle of the LA group than those of the fish fed FO and LO. Meanwhile, totally replacing fish oil with linseed oil inhibited the AMPK/SIRT1/PGC-1α pathway, changed myofibre characteristics (e.g., density, diameter and type of myofibre) and raised the expression of genes or activity of enzyme related to anaerobic metabolism in fish muscle. Dietary AICAR activated AMPK/SIRT1/PGC-1α pathway, restored myofibre characteristics and promoted aerobic metabolism-related genes expression in muscle to some extent. In conclusion, total substitution of dietary fish oil with linseed oil reduced growth, feed utilization and nutritive value of large yellow croaker. And high level of dietary linseed oil induced softer texture and poorer liquid holding capacity (LHC) of muscle, which may be ascribed to the myofibre characteristics changed by linseed oil through depressing muscle AMPK/SIRT1/PGC-1α pathway. Inclusion of AICAR in a linseed oil-based diet improved fish muscle hardness and LHC, which may be relevant to the activated muscle AMPK/SIRT1/PGC-1α pathway and restored myofibre characteristics by AICAR. Notably, dietary AICAR could inhibit TOR pathway by activating AMPK in muscle, which may be responsible for the further decreased SGR of fish fed a linseed oil-based diet.

Dietary inclusion of Schizochytrium limacinum meal can maintain key productive parameters of pink cusk-eel (Genypterus blacodes) juveniles with a reduction in fish oil

The pink cusk-eel ( Genypterus blacodes ) is a promising new candidate species to diversify cold-water aquaculture further. However, there are several knowledge gaps to establish a commercial-scale cultivation strategy, with optimum feed formulation being one of the main remaining challenges. This study aimed to assess the dietary inclusion of Schizochytrium limacinum heterotrophic microalgae meal as a sustainable source of docosahexaenoic acid on fish growth and the condition status of pink cusk-eel juveniles. Three extruded diets were formulated to contain 0, 5 and 10% of dried algae and fed to duplicate groups of fish twice daily until apparent satiation during the 12-week trial. On termination of the feeding trial period, the average live weight gain did not show statistically significant differences between the three groups of juvenile fish, achieving an increase in weight of about two times at the end of the trial. Similarly, the protein efficiency and feed conversion ratios did not show significant differences among the experimental diets. On the contrary, a significant reduction in feed intake was observed as the dietary inclusion of microalgae meal increased. These results indicate that S. limacinum meal is a sustainable alternative ingredient for the dietary substitution of fish oil in commercial feed for G. blacodes at limited inclusion.

Effects of dietary fish oil substitution with blending vegetable oils on growth performance, antioxidant enzyme activities and tissue fatty acid composition of juvenile swimming crab, Portunus trituberculatus

Effects of dietary fish oil substitution with blending vegetable oils on growth performance, antioxidant enzyme activities and tissue fatty acid composition of juvenile swimming crab, <i>Portunus trituberculatus</i>

Dietary soybean lecithin affects growth performance, fillet biochemical composition and digestive enzyme activity in Sparidentex hasta juvenile

ABSTRACT An eight-week study was conducted on silvery-black porgy (Sparidentex hasta) juveniles to evaluate four isoproteic, isolipidic and isoenergetic different diets (50% crude protein, 20% crude lipids, 18.5 MJ kg−1) containing graded levels of soybean lecithin (SBL) (0, 30, 60 and 90 g kg−1 diet) at the expense of fish oil (FO). Fish fed the 60 g SBL kg−1 diet had significantly higher weight gain (32.4%) and feed intake (8.8 g fish−1) than the control group (SBL 0) (P < 0.05). The fillet fatty acid (FA) profiles were correlated with the FA profile of the experimental diets. Fish fed with SBL-supplemented diets had higher fillet phosphatidylcholine levels than the control group (P < 0.05). Plasma total immunoglobulin was higher in fish fed 60 and 90 g SBL kg−1 diets than in the other groups (P < 0.05). Total protease activity was higher in fish fed the 90 g SLB kg−1 diet than other treatments (P < 0.05). Results indicated that substitution of dietary FO with SBL diet up to 67% (60 g SLB kg−1 diet) improved somatic growth performance and profoundly affected the fillet fatty acid profile in silvery-black porgy juveniles.

Interactive effects of dietary vegetable oil and carbohydrate incorporation on the innate immune response of European seabass (Dicentrarchus labrax) juveniles subjected to acute stress

This study aims to understand the interactive effects of high dietary vegetable oils (VO) and carbohydrate (CH) content in European seabass cellular, humoral, and molecular innate immune responses to an acute stress. For that purpose, European sea bass juveniles (74.0 ± 1.5 g) were fed four diets differing in lipid source (fish oil (FO) or a blend of vegetable oils (VO)) and carbohydrate content (0% (CH–) or 20% (CH+) gelatinized starch). Nine fish per dietary treatment were sampled after 73 days of feeding and used as control whereas the remaining fish were subjected to an acute stress (netting, 1 min air exposure, and transfer to smaller tanks). Those fish were then sampled after 1 h and considered the stressed group. In the present study, dietary VO incorporation affected fish humoral immune parameters with a decrease of haematocrit, plasma peroxidase activity, and head-kidney mc2r and gr1 mRNA expression levels. Regardless of dietary treatment, higher cortisol levels were accompanied by an increase of several haematological, cellular, and humoral parameters in response to an acute stress. Dietary VO incorporation led to lower neutrophil numbers, plasma antiproteases activity, and head-kidney cox2 expression level in stressed fish. Fish fed CH+ diets showed a reduction of head-kidney mc2r expression levels in response to stress, while plasma cortisol remained unchanged, plasma NO decreases and antiproteases activity increased. In fish fed the VO diets, CH+ led to a decrease of plasma bactericidal activity compared to that of group CH-, while the opposite pattern was observed for plasma peroxidase. In conclusion, dietary substitution of FO by VO in CH– diet negatively affected the immune response in both undisturbed and stressed fish, while the effect of dietary CH incorporation in VO diet was not clear.

Total substitution of dietary fish oil by vegetable oils stimulates muscle hypertrophic growth in Senegalese sole and the upregulation of fgf6.

The long term effects of fish oil (FO) substitution by increasing the levels of vegetable oils (VO), 0% (CTR), 50% (VO50) and 100% (VO100), in diets for Senegalese sole were evaluated in terms of skeletal muscle cellularity and expression of related genes. After 140 days of feeding, all fish had similar body weight and length. The inclusion of 50% VO did not result in differences in muscle cellularity, but dorsal muscle cross-sectional area and fast-twitch fibre diameter increased in fish fed total FO substitution, whilst fibre density was reduced (P < 0.05) in relation to CTR. The total number of fibres was similar in all treatments. FO substitution did not affect the transcript levels of myogenic genes (myf5, mrf4, myog, myod1, myod2), but resulted in a two-fold increase of fgf6 transcript levels compared to CTR (P < 0.05). The relative expression of igf-I was higher in VO100 than in VO50, but was similar to CTR. FO substitution resulted in cellularity changes related to the stimulation of muscle hypertrophic growth, but not hyperplastic growth, and associated with a nutritional modulation of fgf6 by dietary VO. This study indicates that 50% VO does not affect the muscle phenotype, but total FO substitution stimulates muscle hypertrophy.

Dietary fish oil replacement by linseed oil: Effect on growth, nutrient utilization, tissue fatty acid composition and desaturase gene expression in silver barb (Puntius gonionotus) fingerlings.

Silver barb (Puntius gonionotus) is considered a promising medium carp species for freshwater aquaculture in Asia. This study in silver barb was carried out to evaluate the effects of total or partial substitution of dietary fish oil (FO) with linseed oil (LO) on growth, nutrient utilization, whole-body composition, muscle and liver fatty acid composition. Fish (12.1±0.4g of initial body weight) were fed for 60days with five experimental iso-proteinous, iso-lipidic and iso-caloric diets in which FO (control diet) was replaced by 33.3%, 50%, 66.7% and 100% LO. Final weight, weight gain, percent weight gain, SGR decreased linearly (p<0.001) with increasing LO levels in the diets. Dietary LO substitution levels did not significantly (p>0.05) affect the feed conversion ratio (FCR), protein efficiency ratio (PER) and whole body proximate composition. Furthermore, enhanced level of LO increased α-linolenic acid (ALA; 18:3n3) and linoleic acid (LA; 18:2n6) and decreased eicosapentaenoic acid (EPA; 20:5n3) and docosahexaenoic acid (DHA; 22:6n3) in muscle and liver. To understand the molecular mechanism of long chain-polyunsaturated fatty acid (LC-PUFA) biosynthesis, we cloned and characterized the fatty acyl Δ6 desaturase (Δ6 fad) cDNA and investigated its expression in various organs/tissues following replacement of FO with LO in the diet. The full-length Δ6 fad cDNA was 2056bp encoding 444 amino acids and was widely expressed in various organs/tissues. Replacement of FO with LO increased the expression of Δ6 fad mRNA in liver, muscle and intestine but no significant difference was found in the brain.

Quality of reared gilthead sea bream (Sparus aurata) during ice storage, as affected by dietary fish oil substitution; an instrumental and sensory designation approach

The fillet fatty acids (FAs) and volatile compounds (VCs) of gilthead sea bream, fed either fish oil-based diet (FO) or plant oils (PO), were studied in dorsal and ventral fillet parts over a 12-day ice storage. Fillet FA reflected the FA composition of the respective diets. Monounsaturated FAs were reduced with storage, while no FA differentiations occurred between fillet parts. VCs varied between diet treatments, with food chain-transported compounds (α-pinene and dimethylsulphide) showing higher abundance in the FO group. VCs proposed as fish spoilage indicators (trimethylamine, pentanal, propanal, 3-methylbutanal and 1-penten-3-ol) increased with storage, while concentration of carbon disulphide associated with fresh fish aroma decreased during the same period. VCs varied between fillet parts, with ventral part exhibiting higher concentrations in fat-soluble (terpenes, aromatic hydrocarbons) and spoilage-associated VCs. Sensory analysis revealed no significant differences between diet groups with the exception of fattiness, which was found significantly higher in the plant oil group.

Reprint of “Effect of dietary substitution of fish oil with flaxseed or sunflower oil on muscle fatty acid composition in juvenile steelhead trout (Oncorhynchus mykiss) reared at varying temperatures”

The effect of changing temperature on muscle fatty acid composition was examined in juvenile steelhead trout (~120g) with complete substitution of fish oil (herring oil; HE) with either flax seed oil (FLX; also known as linseed oil) or sunflower oil (SF). The temperature was increased from ~10.0°C to 18.0°C following seasonal temperature changes in ~2°C incremental steps with plateaus. Dietary lipid analysis showed the HE diet was rich in marine lipids, docosahexaenoic acid (DHA, 22:6ω3), eicosapentaenoic acid (EPA, 20:5ω3) and docosapentaenoic acid (DPA, 22:5ω3). In contrast FLX was rich in linolenic acid (ALA, 18:3ω3) and SF in linoleic acid (LA, 18:2ω6). Both diet and temperature had no significant effect on growth but significant effects were observed on muscle fatty acid composition. Proportions of marine fatty acids in HE fed fish were significantly higher than in both SF and FLX fish at the end (41, 31 and 31% respectively), with significantly lower levels of terrestrial plant fatty acids compared to the beginning of the experiment. Substitution of SF and FLX had a direct influence on muscle EPA:AA and ω6:ω3 ratios which could be detrimental to the health of the fish, as well as to the quality of the end product for human consumption.

Effects of dietary fish oil substitution with linseed oil on growth, muscle fatty acid and metabolism of tilapia (Oreochromis niloticus)

This study was conducted to evaluate the effect of linseed oil (LO) replacing different levels of fish oil (FO) on growth, muscle fatty acid composition and metabolism of gift tilapia (Oreochromis niloticus) (mean initial weight 22 ± 0.5 g) in indoor recycle aquarium tanks for 8 weeks. Fish fed the diet with 50% of the oil as LO had higher final body weight (FWG), specific growth rate (SGR) and protein efficiency ratio (PER) than the other groups (P < 0.05). Hepatopancreas lipid content of fish fed 50% LO was lower than the other groups. Total n-3 and n-6 PUFA contents in the dorsal muscle and superoxide dismutase (SOD) activity in serum increased with increasing dietary LO level. Fish fed 50% LO had higher alanine transaminase (ALT), aspartate transaminase (AST) and lipoprotein lipase (LPL) activities in hepatopancreas and total antioxidant capacity (T-AOC) and alkaline phosphatase (AKP) activities in serum than the other groups (P < 0.05). However, malate dehydrogenase (MDH) activities and malondialdehyde (MDA) contents in hepatopancreas were lower than other groups (P < 0.05) with a 50% substitution level. Results of this study indicated that LO could substitute <50% FO without influencing the growth of tilapia. The higher substitution levels of LO induced negative influences on growth, feed utilization and antioxidant ability of tilapia, but could promote DHA synthesis in tilapia muscle.

Total and Partial Substitution of Dietary Fish Oil with Palm Oil to Juvenile Crayfish, Procambarus Llamasi

A 12-week feeding study was carried out to establish the effect of partial or total substitution of fish oil by plant oil in experimental fed diets in crayfish juveniles (Procambarus llamasi). Three isonitrogenous (30% crude protein) and isoenergetic (15.1 kJ/g) practical diets were formulated with 100% fish oil (FO), 100% plant oil (PO), and 50% FO-50% PO. The crayfish were raised on plastic tanks without water exchange, constant aeration, PVC shelters, with an average water temperature of 26 ± 1°C. Uneaten food and fecal residues were siphoned out from the tank bottom each morning. Crayfish total body weight (BW) and total length (TL) was measured every two weeks. Results showed that the use of plant oil did not significantly modified (p>0.05) growth performance, survival or maturity of experimental organisms. All diets were offered to apparent satiation twice a day. Fed was consumed showing good results in all performance growth parameters and maturity index. In conclusion the present study clearly supported the possibility of total or partial substitution of fish oil by plant oil for crayfish. Despite the absence of fish oil as attractant in the diet with 100% PO, its acceptance was as good as the one containing it. P. llamasi demonstrated the feasibility of using a vegetable oil as lipidic energy source, which allows lowering costs in the use of fish oil about 66%.

Effect of dietary substitution of fish oil with flaxseed or sunflower oil on muscle fatty acid composition in juvenile steelhead trout (Oncorhynchus mykiss) reared at varying temperatures

Abstract The effect of changing temperature on muscle fatty acid composition was examined in juvenile steelhead trout (~ 120 g) with complete substitution of fish oil (herring oil; HE) with either flax seed oil (FLX; also known as linseed oil) or sunflower oil (SF). The temperature was increased from ~ 10.0 °C to 18.0 °C following seasonal temperature changes in ~ 2 °C incremental steps with plateaus. Dietary lipid analysis showed the HE diet was rich in marine lipids, docosahexaenoic acid (DHA, 22:6ω3), eicosapentaenoic acid (EPA, 20:5ω3) and docosapentaenoic acid (DPA, 22:5ω3). In contrast FLX was rich in linolenic acid (ALA, 18:3ω3) and SF in linoleic acid (LA, 18:2ω6). Both diet and temperature had no significant effect on growth but significant effects were observed on muscle fatty acid composition. Proportions of marine fatty acids in HE fed fish were significantly higher than in both SF and FLX fish at the end (41, 31 and 31% respectively), with significantly lower levels of terrestrial plant fatty acids compared to the beginning of the experiment. Substitution of SF and FLX had a direct influence on muscle EPA:AA and ω6:ω3 ratios which could be detrimental to the health of the fish, as well as to the quality of the end product for human consumption.

Substitution of dietary fish oil with plant oils is associated with shortened mid intestinal folds in Atlantic salmon (Salmo salar)

BackgroundFish meal and fish oil are increasingly replaced by ingredients from terrestrial sources in the feeds for farmed salmonids due to expanding production and reduced availability of marine feed raw material. Fish oil that is rich in n-3 polyunsaturated fatty acids is considered beneficial to human health in general and to prevent intestinal inflammation and carcinogenesis in particular. In contrast, n-6 fatty acids that are present in many vegetable oils have been associated with increased risk of colitis and colon cancer in rodents and humans, as well as lowered transcription levels of certain stress and antioxidant-related genes in Atlantic salmon.The aim of the present study was to investigate the intestinal health in Atlantic salmon fed with different vegetable oils as partial substitutes of fish oil in the diet. A feed trial lasting for 28 weeks included one reference diet containing fish oil as the sole lipid source and three diets where 80% of the fish oil was replaced by a plant oil blend with either olive oil, rapeseed oil or soybean oil as the main lipid source. These plant oils have intermediate or low n-3/n-6-ratios compared to fish oil having a high n-3/n-6-ratio. The protein and carbohydrate fractions were identical in all the feeds.ResultsMorphometric measurements showed significantly shorter folds in the mid intestine in all groups fed vegetable oils compared to the group fed fish oil. In the distal intestine, the complex folds were significantly shorter in the fish fed soybean oil compared to the fish fed rapeseed oil. Histological and immunohistochemical examination did not show clear difference in the degree of inflammation or proliferation of epithelial cells related to dietary groups, which was further confirmed by real-time RT-PCR which revealed only moderate alterations in the mRNA transcript levels of selected immune-related genes.ConclusionsShortened intestinal folds might be associated with reduced intestinal surface and impaired nutrient absorption and growth, but our results suggest that partial substitution of dietary fish oil with vegetable oils does not have any major negative impact on the intestinal health of Atlantic salmon.

The response of digestive enzyme activities and gut histology in yellowtail kingfish (Seriola lalandi) to dietary fish oil substitution at different temperatures

Yellowtail kingfish (Seriola lalandi) were fed five diets in which the dietary lipid component was replaced with 100% lipid as either poultry oil (PO), canola oil (CO), a blend of fish oil and poultry oil (FO/PO; 50:50) or a blend of fish oil and canola oil (FO/CO; 50:50) and held at 18 or 22°C. After five weeks, the changes in gastrointestinal histology and digestive enzyme activity of fish were examined. Digestive trypsin, lipase and α-amylase enzyme activities were downregulated in fish held at 18°C. The α-amylase activity was not influenced by diet, but the trypsin activities were significantly lower in fish fed the CO diet than fish fed the FO and FO/PO diets. Although the lipase activities were significantly lower in fish fed the CO diet than fish fed the FO/PO diet at 18°C and 22°C, there were no significant differences between fish fed other diets at both temperatures. The reduction in trypsin activity in fish fed the CO diet may be attributed to anti-nutritional factors present in the canola oil. The histology of the foregut and hindgut showed no signs of diet-induced enteritis. However, there was a high influx of goblet cells and severe reduction in supranuclear vacuolisation across all dietary treatments, including the fish oil control diet at both water temperatures and in initial fish samples. As no information exists on the histology of juvenile yellowtail kingfish this study provides baseline information for further study. However, reference tissue from wild fish is recommended to determine the validity of these findings and for the future histological assessment of this economically important fish species to dietary or environmental temperature changes.

Dietary Fish Oil Substitution Alters the Eicosanoid Profile in Ankle Joints of Mice during Lyme Infection1–3

AbstractDietary ingestion of (n-3) PUFA alters the production of eicosanoids and can suppress chronic inflammatory and autoimmune diseases. The extent of changes in eicosanoid production during an infection of mice fed a diet high in (n-3) PUFA, however, has not, to our knowledge, been reported. We fed mice a diet containing either 18% by weight soybean oil (SO) or a mixture with fish oil (FO), FO:SO (4:1 ratio), for 2 wk and then infected them with Borrelia burgdorferi. We used an MS-based lipidomics approach and quantified changes in eicosanoid production during Lyme arthritis development over 21 d. B. burgdorferi infection induced a robust production of prostanoids, mono-hydroxylated metabolites, and epoxide-containing metabolites, with 103 eicosanoids detected of the 139 monitored. In addition to temporal and compositional changes in the eicosanoid profile, dietary FO substitution increased the accumulation of 15-deoxy PGJ2, an antiinflammatory metabolite derived from arachidonic acid. Chiral analysis of the mono-hydroxylated metabolites revealed they were generated from primarily nonenzymatic mechanisms. Although dietary FO substitution reduced the production of inflammatory (n-6) fatty acid-derived eicosanoids, no change in the host inflammatory response or development of disease was detected.

Effects of dietary fish oil substitution with mixed vegetable oils on growth and fillet fatty acid composition of juvenile Caspian great sturgeon (Huso huso)

The objective of this study was to determine the effects of fish oil replacement with dietary vegetable oils on growth performance, chemical composition and fatty acids profiles in fillets of farmed Caspian great sturgeon juveniles Huso huso (26.97 ± 0.49 g). Five isonitrogenous and isolipidic diets were formulated, containing 10 % of added oil. The diet with 100 % kilka fish oil (Caspian tyulka, Clupeonella caspia) was the control. Fish oil was substituted by 50 % of vegetable oils consisting of an equal share of sunflower and soybean oils (diet A), sunflower and canola oils (diet B) and soybean and canola oils (diet C). In diet D, 100 % of fish oil was replaced with vegetable oil (1:1:1 ratio of sunflower oil, soybean oil and canola oil). Significant differences (P > 0.05) were not detected during 60 days feeding trial in final body weight, weight gain, condition factor, specific growth rate, feed conversion rate, protein efficiency ratio and the chemical composition of fillet (crude protein, crude lipid, moisture and ash). Generally, the fatty acids composition of fish fillets was reflective of the dietary lipid sources. These results indicate the feasibility of substituting fish oils with the mixture of vegetable oils in diets of juvenile H. huso without negative influence on growth providing optimum ratios of n-3/n-6 and n-3/18:1n-9 is met in the diet.

Effects of Dietary Fish Oil Substitution with Palm Oil on Growth, Survival, and Muscle Proximate Composition of Cirrhinus mrigala (Hamilton, 1822)

A 60-day growth experiment was carried out to evaluate the effect of replacing dietary cod liver oil with palm oil on the growth, survival, and muscle proximate composition of the Indian major carp, Cirrhinus mrigala. Five diets were fed to triplicate groups of 20 advanced C. mrigala fry (2.16±0.01 g): 100% cod liver+0% palm (control), 25% palm+75% cod liver, 50% palm+50% cod liver, 75% palm+25% cod liver, and 100% palm+0% cod liver. At the end of the experiment, mean weight gain, average daily growth, specific growth rate, feed conversion efficiency, feed conversion ratio, and percentage survival were assessed. Growth performance and survival were not compromised when fish oil was substituted with palm oil up to 25%. However, beyond this level, growth was significantly retarded (p&lt;0.01). There were no significant (p&gt;0.01) differences in feed efficiency or muscle proximate composition. Results confirm the feasibility of substituting up to 25% dietary fish oil by palm oil in diets for C. mrigala advanced fry without negatively affecting growth or feed utilization efficiency.

The effect of replacing dietary fish oil with canola oil on fatty acid composition and expression of desaturase and elongase genes in Jade Tiger hybrid abalone

This study investigates the effect of graded substitution of dietary fish oil (FO) with canola oil (CO) on fatty acid composition and expression of Δ-6 desaturase and elongase 2 genes in the muscle of Jade Tiger hybrid abalone. The control diet contained 1.5% FO supplement (0% CO). Four other diets contained FO/CO in ratios of 3:1 (CO 25%), 1:1 (CO 50%), 1:3 (CO 75%) and 100% CO. The result demonstrated that abalone fed the diets supplemented with 25% and 50% CO showed similarly high levels of total omega-3 polyunsaturated fatty acid (n-3 PUFA), eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) (P<0.05) as the 0% CO group. The highest levels of total PUFA and total monounsaturated fatty acids were found in the 100% CO group (P<0.05). The results also showed that Δ-6 desaturase and elongase 2 gene expression was increased in a graded manner by increasing dietary CO (P<0.05). It was concluded that replacement of FO by CO at the levels of 25–50% can improve the contents of health-benefiting EPA and DHA in abalone.

Effects of dietary fish oil replacement with flaxseed oil on tissue fatty acid composition and expression of desaturase and elongase genes

This study was conducted to evaluate the effects of total or partial substitution of dietary fish oil (FO) by flaxseed oil (FlaxO) in Jade Tiger hybrid abalone on fatty acid composition of muscle, gonad and digestive gland, and the expression of desaturase and elongase genes. Abalone were fed five different experimental diets in which FO (control diet) was serially replaced by 25%, 50%, 75% and 100% FlaxO respectively. Muscle, gonad and digestive gland of abalone fed the control diet and the diets containing 25%, 50% and 75% FlaxO showed significantly higher (P < 0.05) levels of eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) compared to those fed the 100% FlaxO. The results also showed that Δ-6 desaturase and elongase gene expression in muscle was increased in a graded manner by increasing dietary FlaxO. The expression of both genes was higher in abalone fed the FlaxO-substituted diets compared to the abalone fed FO. The replacement of FO with FlaxO in commercial abalone diets at levels of 25-75% can improve the composition of health-benefiting n-3 polyunsturated fatty acids in tissues of cultured hybrid abalone, and achieve similar outcomes to FO supplementation.

Effects of dietary fish oil substitution by Echium oil on enterocyte and hepatocyte lipid metabolism of gilthead seabream (Sparus aurata L.)

The fatty acid profile of vegetable oils (VOs), together with the poor ability of marine fish to convert polyunsaturated fatty acids (PUFA) to highly unsaturated fatty acids (HUFA), lead to important changes in the nutritional value of farmed fish fed VO, which include increased fat and 18:2n-6 and reduced n-3 HUFA. Echium oil (EO) has a good n-3/n-6 balance as well as an interesting profile with its high content of unusual fatty acids (SDA, 18:4n-3 and GLA, 18:3n-6) that are of increasing pharmacological interest. The effects of substituting 50 % of dietary fish oil (FO) by EO on gilthead seabream (Sparus aurata L.) enterocyte and hepatocyte lipid metabolism were studied. After 4months of feeding, cell viability, total lipid contents and lipid class compositions were not affected by EO. The cells clearly reflected the fatty acid profile of the EO showing increased SDA, GLA and its elongation product 20:3n-6, and only minorly decreased n-3 HUFA compared to other VO. Metabolism of [1-(14)C]18:2n-6 and [1-(14)C]18:3n-3 was also unaffected by EO in terms of total uptake, incorporation, beta-oxidation and elongation-desaturation activities.