Grethe Rosenlund

Total replacement of fish oil by soybean or linseed oil with a return to fish oil in turbot (Psetta maxima): 1. Growth performance, flesh fatty acid profile, and lipid metabolism

The aim of the study was to investigate the replacement of fish oil by vegetable oils and the effects of a washout with a return to fish oil on growth performances and lipid metabolism. Three experimental fish meal-based isonitrogenous (crude protein content: 57.5%) and isolipidic (crude lipid content: 16.5%) diets were formulated containing either 9% of added fish oil (FO), soybean oil (SO), or linseed oil (LO). Each diet was distributed to triplicate groups of 25 marketable size turbot (initial body weight of 579 g) grown in seawater at water temperature of 17 °C. Fish were fed once a day to visual satiety. At the end of the growth trial, which lasted 13 weeks, all groups of turbot were fed with FO diet for 8 weeks. The growth of turbot was high, but the incorporation of vegetable oils in the diets resulted in a slight decrease in growth as compared to those fed with fish oil-based diet. Feed and protein efficiency and whole body composition were not affected by dietary lipid sources. Total lipid content was low in the muscle of turbot (below 2%); ventral muscle being fatter than dorsal muscle. Liver and muscle fatty acid (FA) composition reflected dietary FA composition. Liver and muscle of fish fed with SO diet were rich in 18:2n-6, whereas those of fish fed with LO diet were rich in 18:3n-3. Liver and muscle of fish fed with SO and LO diets had lower levels of 20:5n-3 and 22:6n-3 in comparison to those of fish fed with FO diet. In turbot, hepatic lipogenic enzyme activities were low and not influenced by dietary lipid source. At the end of the second period, after transfer to FO-based diets, muscle FA composition of fish fed previously with SO and LO diets were still different to those of fish fed with FO diet. The values of 18:2n-6 and 18:3n-3, respectively, were lower than the values found at the end of the growth period, but higher than those of fish fed with FO diet. An increase of FA levels, characteristic of fish oil, was observed in the liver and muscle of fish previously fed with vegetable oils. Data obtained show that replacement of fish oil by vegetable oils is possible with negligible impact on growth performance of turbot, that dietary lipids are an effective vector to influence the nutritional quality of finished product, and that a duration of 8 weeks is not sufficient to bring the FA profile of turbot of this size back to that of fish fed with fish oil over the whole period.

Dietary intake of differently fed salmon; the influence on markers of human atherosclerosis.

Backgroundu2002 Cardioprotective effects of omega‐3 polyunsaturated fatty acids (n‐3 PUFAs) of marine origin are well recognized. Because of the shortness of marine resources vegetable oils are increasingly used in fish farming. The effects on human health of fish fed on vegetable oils are largely unknown.

Total replacement of fish oil by soybean or linseed oil with a return to fish oil in Turbot (Psetta maxima): 2. Flesh quality properties

The aim of this study was to evaluate (1) the effects of replacement of fish oil by vegetable oils on flesh quality and (2) the effects of a washout with a return to fish oil on flesh quality of turbot. In a first period of 3 months, three isonitrogenous and isolipidic diets containing 9% of added marine fish oil (FO), soybean oil (SO) or linseed oil (LO) were fed to triplicate groups of 25 marketable size turbot (initial body weight: 579±1 g) grown in sea water at the temperature of 17 °C. At the end of the first period, all groups of turbot were fed with the diet containing fish oil (diet FO) for a further period of 2 months. The gutted and fillet yields were not affected by the incorporation of vegetable oils. However, soybean or linseed oils significantly affected the organoleptic quality of flesh particularly odour, colour and texture. A more pronounced potatoes odour and a lower fat texture were observed in dorsal fillet of turbot fed soybean oil diet. During the washout period, the differences observed between treatments in first period on sensory attributes disappeared. This study showed that the changes in organoleptic properties occurring due to the intake of vegetable oils can be reduced with a return to a fish-oil-based diet.

Digestibility of dry matter, protein, starch and lipid by cod, Gadus morhua: comparison of sampling methods

Atlantic cod were fed 11 different extruded diets spanned by a multiple simplex design. The dietary ranges of protein, fat and starch were 36-66%, 8-28% and 8-18%, respectively. All diets contained 0.1% yttrium oxide as an inert marker. After several months of feeding, faeces were sampled, either by stripping or by dissecting the last part of the intestine, which in turn was frozen and faecal matter removed while still partly frozen. No significant differences were found in average digestibility results of dry matter, protein, starch or lipid when comparing the two methods of sampling. All groups showed high digestibility of dry matter, protein and lipid, with minor variations, and only extreme feed compositions resulted in changed digestibility of dry matter and protein. A larger variation was found in apparent starch digestibility, from 60% to 90%, however, independent of dietary level when this was below 17% of dry matter, in agreement with findings for this nutrient as concerns other carnivorous fish. No difference was detected for any of the compared digestibility coefficients when evaluating the four centre points of the multiple simplex design. In conclusion, no difference between methods gives the opportunity to freely choose sampling method, and either stripping or dissection of faecal matter can be used to determine apparent digestibility values in cod.

The effect of enrichment diets on the fatty acid composition of the rotifer Brachionus plicatilis

Cultures of the rotifer Brachionus plicatilis (200 ind./ml, 0.5 μg dry weight/ind.) pre-fed on yeast and capelin oil (10:1 w/w) were given different enriched diets and harvested after 24 h. The fatty acid composition of the rotifers was affected by that of the feed. The highest level of n−3 highly unsaturated fatty acids (HUFA) 38%) and 22:6 n−3 (19%) was obtained after enrichment of the rotifers fed with squid meal. A positive relation was found between the n−3 HUFA in the enrichment diet and that of the rotifers (P < 0.05, t-test). The cultivation feed of the rotifers may nevertheless be more important for the n−3 HUFA level than the enrichment feed. Starvation for 49 h did not change the fatty acid composition of the rotifers.

The Salmon in Pregnancy Study: study design, subject characteristics, maternal fish and marine n–3 fatty acid intake, and marine n–3 fatty acid status in maternal and umbilical cord blood

BACKGROUNDnOily fish provides marine n-3 (omega-3) fatty acids that are considered to be important in the growth, development, and health of the fetus and newborn infant.nnnOBJECTIVESnThe objectives were to increase salmon consumption among pregnant women and to determine the effect on maternal and umbilical cord plasma marine n-3 fatty acid content.nnnDESIGNnWomen (n = 123) with low habitual consumption of oily fish were randomly assigned to continue their habitual diet or were provided with 2 portions of farmed salmon/wk to include in their diet from week 20 of pregnancy until delivery.nnnRESULTSnMedian weekly consumption frequency of study salmon in the salmon group was 1.94 portions, and total fish consumption frequency was 2.11 portions/wk in the salmon group and 0.47 portions/wk in the control group (P < 0.001). Intakes of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from the diet, from seafood, and from oily fish were higher in the salmon group (all P < 0.001). Percentages of EPA and DHA in plasma phosphatidylcholine decreased during pregnancy in the control group (P for trend = 0.029 and 0.008, respectively), whereas they increased in the salmon group (P for trend for both < 0.001). EPA and DHA percentages were higher in maternal plasma phosphatidylcholine at weeks 34 and 38 of pregnancy and in umbilical cord plasma phosphatidylcholine in the salmon group (P < 0.001 for all).nnnCONCLUSIONnIf pregnant women, who do not regularly eat oily fish, eat 2 portions of salmon/wk, they will increase their intake of EPA and DHA, achieving the recommended minimum intake; and they will increase their and their fetus status of EPA and DHA. This trial was registered at clinicaltrials.gov as NCT00801502.

Dietary intake of differently fed salmon: a preliminary study on contaminants

Backgroundu2002 In a previous study, a group of coronary heart disease (CHD) patients exhibited positive cardioprotective effects of fatty acids derived from a diet of farmed Atlantic salmon fed fish oil (Seierstad et al. 2005). This follow‐up study examines these patients for plasma exposure to selected organic and inorganic contaminants found in seafood that may detract from the benefits of eating oily fish.

Predicting World Health Organization toxic equivalency factor dioxin and dioxin-like polychlorinated biphenyl levels in farmed Atlantic salmon (Salmo salar) based on known levels in feed.

Assimilation and elimination rate constant of dietary polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DLPCBs) with a World Health Organization toxic equivalency factor (WHO-TEF) were estimated in market-size Atlantic salmon (Salmo salar) using fish that were previously fed vegetable oil-based (low in PCDD/Fs and DLPCBs) or fish oil-based (high in PCDD/Fs and PCBs) diets. At the start of the kinetic trial, half the fish that were fed fish oils were fed vegetable oil feeds and inverted (cross-over design) for five months. The assimilation efficiencies of the PCDD/F congeners were more variable (3-89%) and, generally, were lower than those of the DLPCBs (70-80%). Among the PCDD/F congeners, the assimilation efficiency of the most toxic tetra- and pentachlorinated PCDD/Fs was greater than that of higher-chlorinated PCDD/Fs. Elimination rates for DLPCBs were higher than those for PCDD/Fs. Lower-chlorinated PCDDs had a lower elimination rate than the higher-chlorinated PCDDs, but no differences were observed among PCDF congeners or DLPCB congeners. Kinetic parameters were used to predict the level of WHO-TEF dioxins and DLPCBs in Atlantic salmon reared in a large-scale facility under commercial conditions. Predictions were based on preanalyzed levels of these organochlorines in feeds with three different replacement levels (0, 30, and 60%) of vegetable oil. A simple one-compartmental, first-order kinetic model was used to predict the level of sum WHO toxic equivalents for PCDD/Fs and DL-PCBs. The predicted values varied by 0 to 11% from the measured values in the commercially reared salmon.

Intake of Farmed Atlantic Salmon Fed Soybean Oil Increases Insulin Resistance and Hepatic Lipid Accumulation in Mice

Background To ensure sustainable aquaculture, fish derived raw materials are replaced by vegetable ingredients. Fatty acid composition and contaminant status of farmed Atlantic salmon (Salmo salar L.) are affected by the use of plant ingredients and a spillover effect on consumers is thus expected. Here we aimed to compare the effects of intake of Atlantic salmon fed fish oil (FO) with intake of Atlantic salmon fed a high proportion of vegetable oils (VOs) on development of insulin resistance and obesity in mice. Methodology/principal findings Atlantic salmon were fed diets where FO was partly (80%) replaced with three different VOs; rapeseed oil (RO), olive oil (OO) or soy bean oil (SO). Fillets from Atlantic salmon were subsequently used to prepare Western diets (WD) for a mouse feeding trial. Partial replacement of FO with VOs reduced the levels of polychlorinated biphenyls (PCB) and dichloro-diphenyl-tricloroethanes (DDT) with more than 50% in salmon fillets, in WDs containing the fillets, and in white adipose tissue from mice consuming the WDs. Replacement with VOs, SO in particular, lowered the n−3 polyunsaturated fatty acid (PUFA) content and increased n−6 PUFA levels in the salmon fillets, in the prepared WDs, and in red blood cells collected from mice consuming the WDs. Replacing FO with VO did not influence obesity development in the mice, but replacement of FO with RO improved glucose tolerance. Compared with WD-FO fed mice, feeding mice WD-SO containing lower PCB and DDT levels but high levels of linoleic acid (LA), exaggerated insulin resistance and increased accumulation of fat in the liver. Conclusion/Significance Replacement of FO with VOs in aqua feed for farmed salmon had markedly different spillover effects on metabolism in mice. Our results suggest that the content of LA in VOs may be a matter of concern that warrants further investigation.

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 28xa0weeks 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.