Effect of replacement of fish oil with camelina (Camelina sativa) oil on growth, lipid class and fatty acid composition of farmed juvenile Atlantic cod (Gadus morhua)

Camelina (Camelina sativa) oil was tested as a replacement for fish oil in diets for farmed Atlantic cod (Gadus morhua). Camelina differs from other plant oilseeds previously used in aquaculture with high lipid (40 %), α-linolenic acid (40 %), antioxidants and low proportions of saturated fats. Dietary treatments were fed to cod (19 g fish^?1 initial weight) for 9 weeks and included a fish oil control (FO), 40 % (CO40) and 80 % (CO80) replacement of fish oil with camelina oil. There was no effect of replacing fish oil with camelina oil included at levels up to 80 % on the growth performance. Cod fed CO80 stored more lipid in the liver (p < 0.01), including more neutral lipid (p < 0.05) and triacylglycerol (p < 0.05). Cod fed CO80 decreased in total polyunsaturated fatty acids (PUFAs) in muscle compared to CO40 and FO (p < 0.05), increased in monounsaturated fatty acids (p < 0.01), decreased in total ω3 fatty acids (FO > CO40 > CO80; p < 0.01) and increased in total ω6 fatty acids (FO < CO40 < CO80; p < 0.01). In the liver, long-chain (LC) PUFA such as 20:4ω6, 20:5ω3, 22:5ω3 and 22:6ω3 decreased when fish oil was removed from the diet (p < 0.05), and increased in 18-carbon fatty acids (p < 0.01). Camelina oil can reduce the amount of fish oil needed to meet lipid requirements, although replacing 80 % of fish oil reduced LC PUFAs in both tissues. A comparison of BF₃ and H₂SO₄ as catalysts to transmethylate cod liver and muscle lipids revealed small but significant differences in some fatty acid proportions.     

Changes in the Quality of Refined Fish Oil in an Accelerated Storage Study

ABSTRACT

The aim of this study was to prepare the refined oil derived from Sardinella longiceps by a step-wise procedure of degumming, bleaching, and deodorization. The refined sardine oil showed greater susceptibility toward oxidation than the crude oil, but the addition of ethyl acetate fractions of the red seaweeds Hypnea musciformis, Kappaphycus alvarezii, and Jania rubens with great antioxidant potential significantly increased the oxidative stability of the refined oil. The refined oil supplemented with the ethyl acetate fraction of these seaweeds indicated more noteworthy oxidative stability indices (≥ 0. 51 h) than α-tocopherol. The induction time was greater for refined oil added with H. musciformis (1.26 h) than butylated hydroxytoluene (1.04 h) and α-tocopherol (0.4 h). No traces of aromatic (δ 6.7–7.5 ppm), hydroperoxides, and aldehydes (δ 9–10 ppm) in the ¹H-NMR spectra of the refined oil supplemented with seaweed extracts at the baseline and after the accelerated storage study demonstrated that the seaweed extracts were able to prevent the formation of secondary oxidation products in the unsaturated system during storage. This study demonstrated the potential of seaweeds as natural alternatives to the synthetic antioxidants to prevent the rancidity of the refined fish for use in food and pharmaceutical industries.     

Deposition of tocopherol and tocotrienol in the tissues of red hybrid tilapia, Oreochromis sp., fed vitamin E-free diets supplemented with different plant oils

Vitamin E, a potent antioxidant consisting of four isomers each (α, β, γ, δ) of tocopherol (T) and tocotrienol (T3), is found naturally in plant oils at different concentrations. In this study, four semi-purified isonitrogenous and isolipidic (10 %) diets containing canola oil, cold-pressed soybean oil, wheat germ oil, or palm fatty acid distillates (PFAD) as the sole vitamin E source were fed to triplicate groups of red hybrid tilapia (Oreochromis sp.) fingerlings (14.82 ± 0.05 g) for 45 days. Vitamin E concentrations and composition were measured in the muscle, liver, skin, and adipose tissue. Deposition of α-T (53.4–93.1 % of total vitamin E) predominated over deposition of other isomers, except in the liver of fish fed the SBO diet, where α-T and γ-T deposition was in the ratio 40:60. T3 deposition (2.6–29.4 %) was only detected in tissues of fish fed the PFAD diet; adipose tissue was the major storage depot. Fish fed the SBO diet contained significantly more (P < 0.05) muscle thiobarbituric acid-reactive substances. Muscle fatty acid composition reflected dietary fatty acid profile. This is the first study to compare the deposition in fish tissues of the naturally occurring vitamin E isomers present in plant oils. The type and concentration of endogenous vitamin E and the fatty acid composition of plant oils can affect the oxidative stability of tilapia tissues.     

Growth performance, feed efficiency and fatty acid composition of juvenile Murray cod, Maccullochella peelii peelii, fed graded levels of canola and linseed oil

In two independent experiments, the effects of dietary inclusion of canola and linseed oil were evaluated in juvenile Murray cod (Maccullochella peelii peelii, Mitchell) over a 112‐day period. In each experiment, fish received one of five semi‐purified diets in which the dietary fish oil was replaced with canola oil (Experiment A) or linseed oil (Experiment B) in graded increments of 25% (0–100%). Murray cod receiving the graded canola and linseed oil diets ranged in final weight from 112.7 ± 7.6 to 73.8 ± 9.9 g and 93.9 ± 3.6 to 74.6 ± 2.2 g, respectively, and exhibited a negative trend in growth as the inclusion level increased. The fatty acid composition of the fillet and liver were modified extensively to reflect the fatty acid composition of the respective diets. Levels of oleic acid (18:1 n‐9) and linoleic acid (18:2 n‐6) increased with each level of canola oil inclusion while levels of α‐linolenic acid (18:3 n‐3) increased with each level of linseed oil inclusion. The concentration of n‐3 highly unsaturated fatty acids in the fillet and liver decreased as the amount of vegetable oil in the diets increased. It is shown that the replacement of fish oil with vegetable oils in low fish meal diets for Murray cod is possible to a limited extent. Moreover, this study reaffirms the suggestion for the need to conduct ingredient substitution studies for longer periods and where possible to base the conclusions on regression analysis in addition to anova .     

Blood vessel melanosis: a physiological detoxification mechanism in Atlantic cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>)

Melanin deposits in white muscle represent a potentially serious quality problem for farmed cod. Black lines of deposited melanin are associated with blood vessels and consist of layers of melanin-filled cells. Despite numerous anecdotal reports of melanosis in farmed cod no detailed investigations into the underlying mechanisms have been undertaken. In this study we have confirmed that melanosis is present in both farmed and wild cod. However, the incidence of melanosis in wild fish is much lower than that in farmed fish. In addition, we have demonstrated that tyrosinase, a copper-dependent metalloenzyme that is the primary enzyme of melanin synthesis, is present in cod tissues. Copper levels are significantly different in the white muscle of farmed (0.5 ± 0.03 mg/kg wet weight) and wild (0.34 ± 0.01 mg/kg wet weight) cod (P < 0.05) and in the blood vessels of farmed (2.23 ± 0.37 mg/kg wet weight) and wild (0.32 ± 0.02 mg/kg wet weight) cod (P < 0.05). Similarly, differences in the levels of tyrosinase activity were observed in both muscle and blood vessels. Melanised tissues contain higher copper concentrations than tissue containing little or no melanin. Furthermore, we have shown that the addition of copper to protein extracts from fish muscle causes an increase in tyrosinase activity in vitro. Our results suggest that overabundance of copper in commercial feeds leads to increased melanin synthesis via increased tyrosinase activity. We propose that melanin is deposited at sites of high copper exposure and subsequently sequesters copper as a means of reducing the overload stress on other homeostatic mechanisms.     

Effects of replacing dietary fish oil and squid liver oil with vegetable oils on the growth,tissue fatty acid profile and total carotenoids of the giant freshwater prawn, Macrobrachium rosenbergii

A feeding trial was conducted to investigate the complete substitution of either fish oil (FO) or squid liver oil (SLO) with crude palm oil (CPO), canola oil (CO) sunflower oil (SFO) or linseed oil (LO), as the sole added lipid source in diets fed to triplicate groups of giant freshwater prawn, Macrobrachium rosenbergii (initial weight = 0.42 ± 0.01 g) for 6 weeks. Prawns fed the CO or SLO diets showed significantly higher (P < 0.05) specific growth rate than those fed the FO or CPO diets. The feed conversion ratio of the prawns was significantly better when fed the CO diet, compared with the FO, CPO, SFO and LO diets. The muscle eicosapentaenoic acid content of prawns fed the vegetable oil (VO) diets were not significantly different (P > 0.05) from those fed the FO diet, although all VO‐based diets led to a significantly lower docosahexaenoic acid content compared with prawns fed the FO or SLO diet. The whole‐body total carotenoid content was significantly lower for prawns fed the SLO diet compared with prawns on the CO or CPO diets. The successful use of VO instead of marine‐based oils in prawn diets will likely reduce feeding costs associated with M. rosenbergii aquaculture.     

Canola oil,as a good alternative dietary lipid source in sturgeon: Effects on growth,physiology and fatty acid profile in Beluga sturgeon Huso huso L.

An 8‐week feeding trial was conducted on juvenile beluga sturgeon Huso huso to evaluate the effects of different dietary lipid levels and sources on growth performance, physiological indices, proximate composition and fatty acid (FA) profile. Four practical diets, which had either low level (120 g/kg) of canola oil (LCO) and fish oil (LFO) or high level (240 g/kg) of canola oil (HCO) and fish oil (HFO), were fed to triplicate groups of 25 beluga (mean initial body weight 207 ± 0.5 g). The growth performance of beluga was improved by replacing dietary fish oil with canola oil and increasing dietary lipid level. Except the number of red blood cells, lymphocytes, neutrophils and eosinophils, the rest of haematological factors including the values of haemoglobin, haematocrit, number of white blood cells, mean corpuscular haemoglobin concentration, cholesterol and triglyceride concentrations and the number of basophils and monocytes were not significantly affected by dietary lipid sources or levels. Results showed that both moisture and crude fat of the beluga muscle were affected by dietary lipid. The highest moisture and the lowest fat contents were found in the muscle of beluga fed fish oil (LFO). Moreover, the lowest moisture and the highest fat contents were observed in the muscle of beluga fed canola oil (HCO) (p < .05). The FA profile of the beluga muscle was significantly influenced by dietary treatments. The highest monounsaturated fatty acids, total n‐6 fatty acids containing linoleic acid and arachidonic acid, and total unsaturated fatty acids were found in fish fed canola oil (LCO and/or HCO) (p < .05). However, n‐3 fatty acids containing linolenic acid, eicosapentaenoic acid and docosahexaenoic acid were not affected by the diet (p > .05). FA profile of the beluga muscles reflected the proportions of CO and FO in the diet except that there was a decrease in oleic acid and linolenic acid, but an increase in arachidonic acid (C20:4n‐6), eicosapentaenoic acid and docosahexaenoic acid. The obtained data showed that canola oil is an excellent source of supplemental dietary lipid in a practical fish‐meal‐based diet of beluga sturgeon under the experimental conditions. Moreover, the data demonstrated that increasing dietary lipid up to 240 g/kg in beluga sturgeon resulted to improve growth performance and haematology.     

Effect of Squid Melanin-Free Ink and Pre-Emulsification on Properties and Stability of Surimi Gel Fortified with Seabass Oil during Refrigerated Storage

ABSTRACT

The effects of melanin-free ink (MFI) and pre-emulsification on gel properties and stability of bigeye snapper surimi gel fortified with seabass oil during refrigerated storage of 10 days were studied. Lipid oxidation as determined by peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) of surimi gel increased as the level of seabass oil increased (P < 0.05). When MFI was incorporated into surimi gel, lower PV was obtained throughout the storage (P < 0.05). Addition of seabass oil pre-emulsified with soy protein isolate (SPI) in the presence of MFI yielded surimi gel with the highest breaking force and could improve oxidative stability during refrigerated storage (P < 0.05). Slight decrease in whiteness was found in surimi gel added with MFI, while those added with MFI along with pre-emulsified seabass oil showed increased whiteness (P < 0.05). Addition of MFI did not affect total viable count and psychrophilic bacterial count in surimi gels. Thus, the incorporation of pre-emulsified seabass oil prepared using SPI in conjunction with MFI could improve quality and oxidative stability of gel from bigeye snapper surimi.     

Use of canola oil in the feed of larval and juvenile goldfish, Carassius auratus (L.)

Goldfish were used as a model for the evaluation of canola oil as a lipid source in the feeds of larval and juvenile cyprinids. Goldfish larvae were raised from hatching until 24 weeks of age on diets containing cod liver oil. canola oil or a mixture of the two oils as the lipid source. Survival, weight gain and weight-length relationship did not differ among groups of fish fed the three diets. Carcass fatty acid profiles largely reflected those of the diets except that carcasses of fish fed canola oil contained long chain (n-3) and (n-6) polyunsaturated fatty acids (PUFA) that are not found in canola oil. This indicates that goldfish are capable of producing these fatty acids from 18-carbon precursors. The flesh of fish fed canola oil would be inferior for human nutrition to that offish fed marine oils, due to lower (n-3) PUFA levels. However, the results do indicate that canola oil has good potential as a lipid source in larval cyprinid diets.     

Effect of oxidized fish oil and α‐tocopherol on growth,antioxidation status,serum immune enzyme activity and resistance to Aeromonas hydrophila challenge of Chinese mitten crab Eriocheir sinensis

The impact of dietary α‐tocopherol on juvenile Chinese mitten crab Eriocheir sinensis was experimentally evaluated in a 10‐week study. Crab were fed with nine diets including three levels of α‐tocopherol (0, 100 and 300 mg kg^?1 diet) and three levels of fish oil oxidation (fresh, moderate and high) in triplicates. Fresh and moderate oil oxidization enhanced weight gain, but moderate and high oil oxidization lowered survival and feed efficiency. The 100‐mg α‐tocopherol kg^?1 diet resulted in higher hepatopancreas MDA than other α‐tocopherol diets. High oil oxidization led to the lowest serum superoxide dismutase (SOD) and glutathione peroxidase (GPH‐PX). The serum SOD and GPH‐PX activities in crab fed 100 mg α‐tocopherol were higher than in those fed other α‐tocopherol diets. The diet without α‐tocopherol addition lowered lysozyme and phenoloxidase (PO) activities compared to other α‐tocopherol diets. Fresh fish oil diet increased PO activity compared to oxidized oils. High oil oxidization caused significantly more mortality than fresh or moderate oxidization after 7‐d postchallenge with Aeromonas hydrophila. Supplementation with α‐tocopherol significantly enhanced resistance to bacterial infection. This study indicates that α‐tocopherol can protect lipid from peroxidation and enhance disease resistance.     

Effects of dietary oxidized oil and vitamin E on the growth,blood parameters and body composition of juvenile Atlantic cod Gadus morhua (Linnaeus 1758)

The effects of oxidized dietary lipid and the role of vitamin E on the growth performance, blood parameters and body composition of juvenile Atlantic cod (Gadus morhua) were evaluated over a 9‐week feeding period. Four isonitrogenous experimental diets containing fresh or oxidized fish oil with or without added vitamin E (α‐tocopherol or mixed tocopherols) were fed to juvenile cod. The oxidized lipid used had a peroxide value of 94 mEq kg^?1 oil. No significant (P>0.05) differences in growth performance (weight gain and specific growth rate) or feed utilization (feed consumption and feed efficiency ratio) were observed when oxidized dietary lipid was used. The hepatosomatic index (HSI), viscerosomatic index (VSI) and haematocrit did not show any significant (P>0.05) differences among the treatments. However, erythrocyte osmotic fragility (EOF), referred to as susceptibility to haemolysis, of fish fed oxidized oil without added vitamin E was high in comparison with those fed unoxidized oil. Supplementation with α‐tocopherol appeared to decrease haemolysis, but mixed tocopherols had no significant (P>0.05) effect on EOF. The proximate composition of fish whole body was also affected by diet treatment. Fatty acid composition of liver total lipid reflected that of dietary lipid. Variations in tissue (liver and muscle) fatty acid composition among the treatments followed the same trend as those of the dietary fatty acids. Fish fed fresh oil had a higher proportion of polyunsaturated fatty acids (PUFA) in muscle and liver lipid than those fed oxidized oil. The results suggest that oxidized dietary oil affected juvenile Atlantic cod in certain tissues and that these effects could be alleviated by supplementation of sufficient amounts of vitamin E in the diet.     

Oxidative stability of lipids from squid tissues

ABSTRACT: Oxidative stability of lipids from squid tissues was compared with those of other marine lipids. On the basis of peroxide formation, total lipids (TL) from squid viscera or squid muscle with skin were most oxidatively stable, followed by squid eye TL, trout egg TL, bonito oil, and tuna orbital TL, respectively. This tendency in oxidative stabilities was also confirmed by the decrease in unoxidized polyunsaturated fatty acids during oxidation. Analyses of tocopherol contents and lipid compositions suggested that the higher oxidative stabilities of three kinds of squid tissue TL and trout egg TL compared to those of bonito oil and tuna orbital TL would be mainly because of the presence of phospholipids (PL) in squid tissue lipids and trout egg TL. However, the oxidative stability of lipids containing PL did not always decrease with increasing PL contents and stability was strongly influenced by PL composition. As squid viscera contained more than 25% of TL and these lipids were oxidatively stable, squid viscera may be used as a good resource of functional lipids rich in eicosapentaenoic acid and docosahexaenoic acid.     

Effects of dietary lipids on the fatty acid composition of triglycerides and phospholipids in tissues of white sturgeon

Eight purified diets were fed to juvenile white sturgeon, Acipenser transmontanus Rick, for 9 weeks to investigate the effect of dietary lipids on the fatty acid composition of phospholipids and triglycerides from muscle, liver and brain. The diets contained 150 g kg^?1 of oils from canola, corn, cod liver, lard, linseed, soybean, safflower, or a control mixture (corn oil/cod liver oil/lard, 1:1:1, by wt). Dietary lipids significantly (P≤ 05) affected the composition of tissue triglycerides and phospholipids. Tissue triglyceride fatty acid composition ranged widely, in parallel with the dietary lipids, while phospholipids changes were more conservative. Brain phospholipid fatty acid composition was less responsive to diet compared with that in muscle and liver. Considerable amounts of n-6 and n-3 long chain polyun-saturated fatty acids (> C₂₀) were found in triglycerides and phospholipids with all diets, demonstrating that white sturgeon can desaturate and elongate linoleic acid (18:2n–6) and linolenic acid (18:3n–3). Further, the products of the Δ6 desaturase, i.e. 18:3 n–6 and 18:4n–3, were relatively abundant in triglyceride, suggesting that the Δ6 desaturase might not be a limiting step in the process in white sturgeon. Nevertheless, accumulation of both EPA and DHA was greater in the sturgeon fed fish oil than those fed linseed oil, indicating that muscle triglyceride EPA and DHA levels are best enhanced by diets rich in preformed EPA and DHA.     

Effect of Alpha-Linolenic Acid Sources in Diets for Nile Tilapia on Fatty Acid Composition of Fish Fillet Using Principal Component Analysis

This study evaluated the effect of feed supplementation with chia and canola oils as a substitute for soybean oil on the composition of Nile tilapia muscle tissue using chemometrics. Diets were supplemented with 2.1% of each oil and were provided to fish for 15 and 30 days. Compared to soybean oil, supplementation with canola and chia oils significantly increased (P < 0.05) the contents of eicosapentaenoic acid (EPA, 20:5n-3), docosapentaenoic acid (DPA, 22:5 n-3), and docosahexaenoic acid (DHA, 22:6 n-3) in Nile tilapia fillet. At 30 days, DHA content increased 97% in Nile tilapia fed chia oil and 91% in treatment with canola oil. The highest EPA content correlated to treatment with chia oil (7.33 mg 100 g^?1). The long-chain polyunsaturated fatty acids (LC-PUFAs) precursors, linoleic acid and α-linolenic acid, were observed to increase according to treatment type and feed supplementation duration. The principal component analysis resulted in a two-principal-component model that described 92.07% of the total data variance. Also, it highlighted that the replacement of soybean oil with canola and chia oils in Nile tilapia diets contributed to increasing the n-3 LC-PUFA concentration in Nile tilapia fillets, improving its nutritional value.     

The influence of a dietary lipid source on growth, muscle fatty acid composition and erythrocyte osmotic fragility of hybrid tilapia

An 8-week feeding trial was conducted to determine the effects of various dietary lipids on the growth, tissue proximate composition, muscle fatty acid composition and erythrocyte osmotic fragility of red hybrid tilapia, Oreochromis sp. Five isonitrogenous and isoenergetic semipurified diets were supplemented with 10% of either cod liver oil (CLO), sunflower oil (SFO), crude palm oil (CPO), crude palm kernel oil (CPKO), or a combination of 5% CLO with 5% palm fatty acid distillates (PFAD), respectively. There were no significant effects (P > 0.05) of diet on growth but fish fed the CLO diet showed a significantly (P< 0.05) poorer feed efficiency ratio compared to fish fed the CPO diet. Lipid deposition in fish muscle was mostly similar among fish fed the various diets but bone ash was significantly higher in fish fed the CPO and CPKO diets. Muscle lipids of fish fed palm oil-based diets did not increase in saturated fatty acids content but showed significantly lower polyunsaturated fatty acid (PUFA) concentrations compared to fish fed the CLO diet. The concentrations of individual PUFA in muscle lipids were strongly influenced by dietary PUFA concentrations. Dietary lipids did not markedly affect the structural integrity of erythrocyte membranes but the erythrocytes of tilapia fed the CPO diet were slightly more resistant to osmotic lysis. It was concluded that palm oil products, especially CPO, could be successfully used in the diet of hybrid tilapia based on its availability, cheaper costs and its potential ability to enhance oxidative stability due to its low PUFA content and high natural concentrations of antioxidants.     

Antioxidant Efficacy of Protein Hydrolysates from Large Yellow Croaker (Pseudosciaena crocea) in D-galactose-Induced Aging Mice

The antioxidant efficacy of protein hydrolysates prepared from large yellow croaker (Pseudosciaena crocea) by enzymatic hydrolysis using neutral protease was evaluated in D-galactose-induced aging mice. Animals were divided into normal and model control groups, and low-, middle-, and high-dose groups (50, 100, and 300 mg/kg; LYCHs), as well as tocopherol (VE) and antagonistic (LYCHs + VE) groups. The study was carried out for 30 days. Administration of D-galactose induced oxidative damage with a significant rise (p < 0.01) in malondialdehyde and a reduction in several endogenous antioxidant enzymes and glutathione (GSH). Treatment with large yellow croaker protein hydrolysates stimulated an increase in superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase activities, increased levels of reduced glutathione, and decreased malondialdehyde, compared with the model control group. Additionally, hepatocellular damage was evaluated by measuring aspartate aminotransferase and alanine aminotransferase levels. These results demonstrate the protective role of large yellow croaker protein hydrolysates in D-galactose-induced oxidative stress, as well as their potential as nutraceuticals or adjuvant agents for disease prevention.     

Effect of Dietary Safflower and Canola Oil on Growth Performance,Body, and Fatty Acid Composition of Rainbow Trout (Oncorhynchus mykiss)

The objective of the present study was to evaluate the effects of the diets enriched with safflower and canola oil on growth, feed utilization, body composition, liver, and muscle fatty acid composition of rainbow trout (Oncorhynchus mykiss). Rainbow trout having approximate initial weight of 97.03 ± 0.10 g were fed the experimental diets containing only fish oil (Group 0SFO), safflower oil (50% safflower oil, Group 50SFO and 33% safflower oil, Group 33SFO), and vegetable oil blend (33% safflower and 33% canola oil, Group 66SFCO) for 45 days. Twenty-five fish were randomly assigned for triplicate treatments and offered the test diets two times daily to apparent satiation. At the end of the experiment, survival was 100% in all treatments. No significant differences in the weight gain, specific growth rate, feed conversion ratio, and protein efficiency ratio were found between fish fed with the different experimental diets. The highest hepatosomatic index (HIS) and viscerasomatic index (VSI) was obtained in 50SFO and 33SFO groups, respectively. The moisture, protein, lipid, and ash content in the body composition of the fish increased in all experimental groups. The lipid content was not significantly different among the groups (p > 0.05); however, there was a significant difference in ash content between the control and the other groups (p < 0.05). The experimental diets containing vegetable oil (50SFO and 33SFO groups) and vegetable oil blend (66SFCO group) had significantly higher concentrations of n-6 fatty acids, predominantly in the form of linoleic acid (LA). The n-3 fatty acids were present in significantly higher concentration in the control treatment (0SFO). The fatty acid composition of fish fillet and liver were reflective of the dietary lipid source. While the fillet and liver of fish fed the 50SFO diet was high in linoleic acid (18:2 n-6), fish fed the 66SFCO diet had high concentrations of oleic acid (OA; 18:1 n-9). The present study suggests that fish oil can be replaced by up to 50% with safflower oil and by up to 66% with safflower + canola oil blend in rainbow trout diets with no significant effect on growth.     

Effects of replacing fish meal and oil with plant resources in on‐growing diets for Atlantic cod Gadus morhua L

The present paper gives an overview on the use of plant protein and plant oils as replacers for fish meal and fish oil in diets for Atlantic cod Gadus morhua L. In focus are effects on growth, feed utilization, digestibility, gut health, muscle and liver uptake and retention of nutrients, and muscle quality. Plant oil can replace fish oil without affecting growth provided that the requirement of marine long chain (LC) n‐3 fatty acids is met, but the altered dietary fatty acid profile in diet will be reflected in both muscle and liver. This can reduce the value of cod liver as an oil source for cod liver oil production. For the fish itself, there are more challenges replacing fish meal than fish oil, due to the amount of fibre and antinutrients in plant protein meals. However, A. cod seems to tolerate a wide range of plant types and their inclusion levels provided that the amino acids requirements are met. It is our view that there is sufficient knowledge to be able to design an A. cod diet based on a mixture of plant and marine ingredients and be able to predict performance such as growth, feed utilization, digestibility, liver size and fish health in general.     

Effects of phospholipid addition to diets with different inclusion levels of fish oil on growth and fatty acid body composition of juvenile swimming crab Portunus trituberculatus

Six experimental diets were designed with two phospholipid (PL; 0% and 1.5%) and three fish oil levels (0%, 1% and 3%) to evaluate the effects of dietary fish oil and PL levels on growth, survival and fatty acid composition of juvenile swimming crab, Portunus trituberculatus. Diets were iso‐energetic and iso‐nitrogenous and each diet was fed to triplicate groups (initially weight, 24.88 ± 0.04 g per crab) for 59 days. Weight gain (WG) and specific growth rate (SGR) increased with dietary PL addition to 0% fish oil‐supplemented diets (P < 0.05). On the other hand, WG and SGR decreased with dietary PL addition to 3% fish oil diets (P < 0.05). Crabs fed PL supplemented diets had higher haemolymph low‐density lipoprotein cholesterol concentrations and muscle crude lipid levels (P < 0.05) than crabs fed a none PL supplemented diet. The percentage of highly unsaturated fatty acids (HUFA; % total FA) in both polar and neutral lipids fractions of muscle tissue only increased in case of PL addition to 0% and 1% fish oil‐supplemented diets (P < 0.05). HUFA levels in the neutral lipids fraction of the hepatopancreas increased by dietary PL addition at each dietary fish oil level (P < 0.05). In this study, both dietary fish oil and PL addition contributed to a high n‐3/n‐6 ratio in muscle and hepatopancreas of P. trituberculatus. In conclusion, PL addition is only meaningful with fish oil‐deficient diets, in which case it enhanced lipid transport and HUFA absorption efficiency, hence improving the nutritional value of the diet.     

Effects of dietary fish oil replacement with vegetable oils on growth and tissue fatty acid composition of humpback grouper, Cromileptes altivelis (Valenciennes)

The replacement of dietary marine fish oil with vegetable oils was examined in fingerling humpback grouper, Cromileptes altivelis, over the course of an 8‐week growth trial. Five isolipidic (10%) and isoproteic (50%) fish meal‐based practical diets were formulated to contain iso‐ingredients but with different sources of lipids [crude palm oil (CPO), refined, bleached and deodorized, palm olein (RBDPO), soybean oil (SBO) or canola oil (CNO)], and their performance was compared with the control diet, which contained cod liver oil (CLO) as the added lipid source. The experimental diets were fed close to apparent satiation twice a day to triplicate groups of fish (10.6 ± 2.2 g). The grouper fingerlings were randomly distributed into groups of 12 fish in cylindrical cages (61 cm depth and 43 cm diameter) that were placed in a 150 tonne polyethylene seawater tank. There were no significant differences (P>0.05) in terms of growth, survival, feed conversion ratio, protein efficiency ratio, net protein utilization, hepatosomatic index and condition factor among fish fed the various dietary treatments. Similarly, the dietary lipid source did not significantly affect the whole body proximate composition of the fish. Muscle and liver fatty acid composition of fish was influenced by the experimental diets. Replacement of dietary CLO with CPO, RBDPO, SBO or CNO produced fish with lower n‐3 highly unsaturated fatty acids and increased levels of 18:2n‐6 in the muscle and liver. The n‐3:n‐6 fatty acid ratio in the muscle of fish fed the CLO‐based diet was 3.0 compared with 0.5–0.8 in the muscle of fish fed the various vegetable oil‐based diets. The present study demonstrated that various vegetable oils can be used in fish meal‐based dietary formulations for humpback grouper without compromising growth or feed utilization efficiency.