Tropical Vegetable Oils Do Not Alter Growth Performance in African Catfish through a High n-6 Polyunsaturated Fatty Acids Biosynthesis Capacity

The main objective of this study was to determine the best vegetable oils (VO) for nutrition of African catfish by assessing the effects of a complete replacement of fish oil (FO) by different VO sources on its growth performance, fatty acid composition, and elongase-desaturase gene expression levels. Fish (16.2 g of initial body weight) were fed with five experimental isonitrogenous, isolipidic, and isoenergetic diets in which FO was totally replaced by cottonseed oil (CO), palm oil (PO), desert date oil (DO), or Shea butter (SB). Complete replacement of FO with VO did not affect growth performance except for low values in fish fed SB diet. Muscle n-3 LC-polyunsaturated fatty acids (PUFA) were significantly reduced in fish fed VO-based diets when compared with FO fed fish. However, the muscle arachidinic acid (ARA) levels in phospholipid class were 1.4 to 1.6 times higher in fish fed CO and DO diets than FO fed fish despite the lower ARA suppliers from these VO-based diets, suggesting endogenous LC-PUFA biosynthesis from PUFA precursors in fish fed these VO. The fads2 and elovl5 gene expression levels in liver of fish fed DO were also higher compared to FO controls. Therefore, all the results support the hypothesis that African catfish has higher biosynthesis capacity to convert vegetable n-6 PUFA precursors like linoleic acid (LNA, 18:2n-6) into n-6 LC-PUFA of the ARA type, compared to the conversion of vegetable α-linolenic acid (ALA, 18:3n-3) into n-3 LC-PUFA of the eicosapentanoic acid (EPA) or docosahexanoic acid (DHA) type. The results also indicate that DO can be recommended as the best alternative to FO replacement in African catfish nutrition.     

Dietary Linseed Oil Reduces Growth While Differentially Impacting LC-PUFA Synthesis and Accretion into Tissues in Eurasian Perch (Perca fluviatilis)

The aim of this study was to evaluate the impact of replacing dietary fish oil (FO) with linseed oil (LO) on growth, fatty acid composition and regulation of lipid metabolism in Eurasian perch (Perca fluviatilis) juveniles. Fish (17.5 g initial body weight) were fed isoproteic and isoenergetic diets containing 116 g/kg of lipid for 10 weeks. Fish fed the LO diet displayed lower growth rates and lower levels of DHA in the liver and muscle than fish fed the FO diet, while mortality was not affected by dietary treatment. However, DHA content recorded in the liver and muscle of fish fed the LO diet remained relatively high, despite a weight gain of 134 % and a reduced dietary level of long‐chain polyunsaturated fatty acids (LC‐PUFA), suggesting endogenous LC‐PUFA biosynthesis. This was supported by the higher amounts of pathway intermediates, including 18:4n‐3, 20:3n‐3, 20:4n‐3, 18:3n‐6 and 20:3n‐6, recorded in the liver of fish fed the LO diet in comparison with those fed the FO diet. However, fads2 and elovl5 gene expression and FADS2 enzyme activity were comparable between the two groups. Similarly, the expression of genes involved in eicosanoid synthesis was not modulated by dietary LO. Thus, the present study demonstrated that in fish fed LO for 10 weeks, growth was reduced but DHA levels in tissues were largely maintained compared to fish fed FO, suggesting a physiologically relevant rate of endogenous LC‐PUFA biosynthesis capacity.     

Dietary Fatty Acid Metabolism is Affected More by Lipid Level than Source in Senegalese Sole Juveniles: Interactions for Optimal Dietary Formulation

This study analyses the effects of dietary lipid level and source on lipid absorption and metabolism in Senegalese sole (Solea senegalensis). Juvenile fish were fed 4 experimental diets containing either 100 % fish oil (FO) or 25 % FO and 75 % vegetable oil (VO; rapeseed, linseed and soybean oils) at two lipid levels (~8 or ~18 %). Effects were assessed on fish performance, body proximate composition and lipid accumulation, activity of hepatic lipogenic and fatty acid oxidative enzymes and, finally, on the expression of genes related to lipid metabolism in liver and intestine, and to intestinal absorption, both pre‐ and postprandially. Increased dietary lipid level had no major effects on growth and feeding performance (FCR), although fish fed FO had marginally better growth. Nevertheless, diets induced significant changes in lipid accumulation and metabolism. Hepatic lipid deposits were higher in fish fed VO, associated to increased hepatic ATP citrate lyase activity and up‐regulated carnitine palmitoyltransferase 1 (cpt1) mRNA levels post‐prandially. However, lipid level had a larger effect on gene expression of metabolic (lipogenesis and β‐oxidation) genes than lipid source, mostly at fasting. High dietary lipid level down‐regulated fatty acid synthase expression in liver and intestine, and increased cpt1 mRNA in liver. Large lipid accumulations were observed in the enterocytes of fish fed high lipid diets. This was possibly a result of a poor capacity to adapt to high dietary lipid level, as most genes involved in intestinal absorption were not regulated in response to the diet.     

Replacing Dietary Fish Oil with Vegetable Oil Blends in Female Rainbow Trout Brood Stock Does Not Affect Breeding Quality

To determine the effects of replacing fish oil (FO) with a mixture of vegetable oils (VO) in plant protein-rich diets on reproductive performance, the fatty acid profile of embryos as well as health indices of female rainbow trout (Oncorhynchus mykiss) brooders (initial mean body weight, 1.8 ± 0.1 kg), a 3-month feeding trial was conducted. Four isoproteic (ca. 42%) and isoenergetic (ca. 20 MJ/kg) diets were formulated in which 50% (FO50/VO50), 75% (FO25/VO75), and 100% (VO100) of FO were replaced by a mixture of VO, whereas the control diet (FO100) was prepared with FO as the major source of lipid. Fish fed the VO100 had the lowest fertilization (73.0 ± 2.5%), survival at eyed-embryo stage (62.5 ± 5.0%), and hatching rate (56.0 ± 4.7%) rates. Brood fish fed the FO50/VO50, FO25/VO50, and VO100 diets had higher levels of saturated and monounsaturated fatty acids in embryos in comparison with fish fed FO100 diet. The levels of docosahexaenoic acid of embryos gradually decreased during embryogenesis in all treatments, whereas the concentrations of eicosapentaenoic acid was greatly increased at hatching day (35 days after spawning). Regarding serum biochemical parameters, fish fed the VO100 diet had the highest serum glucose, cholesterol, and low-density lipoprotein levels. The results of the current study revealed that replacement of dietary FO with a mixture of VO up to 75% did not have any adverse effects on reproductive performance and health indices of O. mykiss females.     

The effect of dietary lipid on polyunsaturated fatty acid metabolism in Atlantic salmon (Salmo salar) undergoing parr-smolt transformation

The aim of this study was to measure the changes in lipid metabolism which occur during smoltification and seawater transfer in Atlantic salmon (Salmo salar). Duplicate groups of Atlantic salmon parr were fed diets containing either fish oil (FO) or a blend of linseed and rapeseed oils, vegetable oil (VO), from October (week 0) to seawater transfer in May (week 26). From May to August (weeks 26–43), all fish were fed a fish oil-containing diet. Fatty acyl desaturation and elongation activity were followed in isolated hepatocytes incubated with radioactive 18:3n−3 and 18:2n−6. Metabolism of 18:3n−3 was consistently around 5-fold greater than metabolism of 18:2n−6, and total metabolism of both substrate polyunsaturated fatty acids (PUFA) was increased in fish fed both VO and FO up to seawater transfer after which desaturation activities were reduced. Desaturation activities with both 18:3n−3 and 18:2n−6 were significantly greater in fish fed VO, compared to fish fed FO, at 22 and 26 wk. Arachidonic acid (20:4n−6; AA) in liver polar lipids (PL) of fish fed VO increased consistently from weeks 0–22 but varied after seawater transfer. In fish fed FO, AA in liver PL remained constant up to week 17 before increasing at seawater transfer and leveling off thereafter. Eicosapentaenoic acid (20:5n−3; EPA) in liver PL of fish fed VO decreased significantly from week 0–22 before rising at seawater transfer and increasing rapidly posttransfer. EPA in liver PL of fish fed FO showed a similar trend except EPA was always greater in the freshwater phase compared to fish fed VO. Docosahexaenoic acid (DHA) levels in liver PL of fish fed VO remained constant in the freshwater phase before increasing following seawater transfer. In fish fed FO, DHA in liver PL increased from weeks 0–17 reducing and leveling off postseawater transfer. The levels of PGF_2α and PGF_3α were measured in isolated gill cells stimulated with calcium ionophore A23187. PGF_2α production in fish fed VO increased significantly between 0–7 wk before decreasing toward seawater transfer. After transfer, PGF_2α production increased to a peak at 35 wk. PGF_2α production in fish fed FO was not significantly altered during the trial period. The changes in PGF_3α production were broadly similar to those occurring with PGF_2α, but the latter was always in excess of the former (2-to 4-fold). Plasma chloride concentrations in fish subjected to seawater challenge at 20 wk were significantly lower in fish fed VO compared to those fed FO. This study has provided new information on the changes in lipid metabolism which accompany parr-smolt transformation and suggests that diets which have a fatty acid composition more similar to that in aquatic invertebrates may be beneficial in effecting successful seawater adaptation.     

Replacement of Dietary Fish Oils by Alpha-Linolenic Acid-Rich Oils Lowers Omega 3 Content in Tilapia Flesh

A 20-week feeding trial was conducted to determine whether increasing linolenic acid (18:3n-3) in vegetable oil (VO) based diets would lead to increased tissue deposition of 22:6n-3 in Nile tilapia (Oreochromis niloticus). Five isonitrogenous and isoenergetic diets were supplemented with 3% of either linseed oil (LO), a mixture of linseed oil with refined palm olein oil (PO) (LO–PO 2:1) and a mixture of refined palm olein oil with linseed oil (PO–LO 3:2) or with fish oil (FO) or corn oil (CO) as controls. The PO–LO, LO–PO and LO diets supplied a similar amount of 18:2n-6 (0.5% of diet by dry weight) and 0.5, 0.7 and 1.1% of 18:3n-3, respectively. Increased dietary 18:3n-3 caused commensurate increases in longer-chain n-3 PUFA and decreases in longer-chain n-6 PUFA in the muscle lipids of tilapia. However, the biosynthetic activities of fish fed the LO-based diets were not sufficient to raise the tissue concentrations of 20:5n-3, 22:5n-3 and 22:6n-3 to those of fish fed FO. The study suggests that tilapia (O. niloticus) has a limited capacity to synthesise 20:5n-3 and 22:6n-3 from dietary 18:3n-3. The replacement of FO in the diet of farmed tilapia with vegetable oils could therefore lower tissue concentrations of 20:5n-3 and 22:6n-3, and consequently produce an aquaculture product of lower lipid nutritional value for the consumer.     

Chemical Form of Dietary Selenium Affects the Fatty Acids Profile and Oxidative Stability of Muscles of Broilers Supplemented with Lycopene and Oils

The aim of this study is to determine the effects of the addition of different chemical forms of selenium (Se)—selenate (SeVI) or selenized yeast (SeY) to chickens’ diet containing equal amounts of fish (FO) and sunflower oils and lycopene (Lyc) on fatty acids (FA) profile and peroxidation yield in thigh muscles of chickens. FA profile is analyzed by gas chromatography coupled with mass spectrometry while content of malondialdehyde is determined by ultra‐fast liquid chromatography (UPLC) with photodiode detection. The diets containing SeY or SeVI increase the feed conversion efficiency of chickens compared with the control diet. SeY or SeVI added to the diet containing Lyc and FO stimulates concentrations of monounsaturated and polyunsaturated (PUFA) FA in muscles. Muscles of chickens fed a diet only with Lyc and FO have the highest indices of atherogenic (A‐SFA) and thrombogenic (T‐SFA) saturated FA and the highest ratios of A‐SFA and T‐SFA to all assayed FA. Dietary Se‐compounds also decrease the PUFA peroxidation indices in muscles compared with the diet containing only FO and Lyc. Therefore Se‐compounds may be added to diets including FO and Lyc to improve the growth parameters, nutritive value, and oxidative stability of chicken meat. Practical Applications: Poultry meat, which is characterized by high protein content of high biological value, high minerals and vitamins, and low collagen and fat content, is recommended as particularly desirable in a balanced diet to replace red and highly processed meat. Also, relatively good price makes this type of meat one of the most popular among consumers. The present study aims to check if inclusion of different chemical forms of selenium into chickens’ diets improves nutritional value of broiler meat. Feeding chickens with seleno‐supplements significantly enhances poultry production efficiency and nutritional value of broilers’ meat, because it favorably modifies FA composition (enhanced monounsaturated and polyunsaturated FA and decrease atherogenic and thrombogenic saturated FA in muscles) and reduces lipid oxidation in chickens’ meat. These results are important from the both producers’ and consumers’ point of view and correspond to contemporary nutritional recommendations.     

Dietary Fish Oil Supplements Increase Tissue n-3 Fatty Acid Composition and Expression of Delta-6 Desaturase and Elongase-2 in Jade Tiger Hybrid Abalone

This study was conducted to investigate the effects of fish oil (FO) supplements on fatty acid composition and the expression of ∆6 desaturase and elongase 2 genes in Jade Tiger abalone. Five test diets were formulated to contain 0.5, 1.0, 1.5, 2.0 and 2.5% of FO respectively, and the control diet was the normal commercial abalone diet with no additional FO supplement. The muscle, gonad and digestive glands (DG) of abalone fed with all of the five test diets showed significantly high levels of total n-3 polyunsaturated fatty acid (PUFA), eicosapentaenoic acid (EPA), docosapentaenoic acid n-3 (DPAn-3), and docosahexaenoic acid (DHA) than the control group. In all three types of tissue, abalone fed diet supplemented with 1.5% FO showed the highest level of these fatty acids (P < 0.05). For DPAn-3 the higher level was also found in muscle and gonad of abalone fed diet supplemented with 2% FO (P < 0.05). Elongase 2 expression was markedly higher in the muscle of abalone fed diet supplemented with 1.5% FO (P < 0.05), followed by the diet containing 2% FO supplement. For ∆6 desaturase, significantly higher expression was observed in muscle of abalone fed with diet containing 0.5% FO supplement (P < 0.05). Supplementation with FO in the normal commercial diet can significantly improve long chain n-3 PUFA level in cultured abalone, with 1.5% being the most effective supplementation level.     

Dietary fish oil dose- and time-response effects on cardiac phospholipid fatty acid composition

Fish consumption is associated with reduced cardiovascular mortality, and elevated myocardial long-chain n−3 polyunsaturated FA (PUFA) content is implicated in this cardioprotection. This study examined the dose and time responses for incorporation of n−3 PUFA into cellular membranes in rats fed fish oil (FO)-containing diets. For the time course study, rats were fed a 10% FO diet for periods ranging from 0 to 42 d, after which myocardial and erythrocyte membrane fatty acid composition was determined. For the dose response study, rats (n=3) were fed 0, 1.25, 2.5, 5, or 10% FO for 4 wk, with myocardial, erythrocyte, and skeletal muscle membrane FA determined. Myocardial DHA (22∶6n−3) levels doubled in 2 d, stabilizing at levels ≈200% higher than control after 28 d feeding with 10% FO. By comparison, DHA levels doubled after 4 wk of 1.25% FO feeding. In myocardium and skeletal muscle, EPA (20∶5n−3) levels remained low, but in erythrocytes EPA levels reached 50% of DHA levels. The n−3 PUFA were incorporated at the expense of n−6 PUFA in myocardium and skeletal muscle, whereas erythrocytes maintained arachidonic acid levels, and total n−3 PUFA incorporation was lower. This study shows that low doses of FO produce marked changes in myocardial DHA levels; maximal incorporation takes up to 28 d to occur; and while erythrocytes are a good indicator of tissue n−3 incorporation in stable diets, they vary greatly in their time course and pattern of incorporation.     

Partitioning of Rumen-Protected n-3 and n-6 Fatty Acids is Organ-Specific in Growing Angus Heifers

Dietary polyunsaturated fatty acids (PUFA), especially n-3 and n-6 fatty acids (FA), play an important role in the regulation of FA metabolism in all mammals. However, FA metabolism differs between different organs, suggesting a distinct partitioning of highly relevant FA. For the present study in cattle, a novel technology was applied to overcome rumen biohydrogenation of dietary unsaturated FA. Angus heifers were fed a straw-based diet supplemented for 8 weeks with 450 g/day of rumen-protected oil, either from fish (FO) or sunflower (SO). The FA composition in blood and five important organs, namely heart, kidney, liver, lung, and spleen, was examined. In blood, proportions of polyunsaturated FA were increased by supplementing FO compared to SO. The largest increase of eicosapentaenoic acid (EPA) proportion was found with FO instead of SO in the kidney, the lowest in the lung. Docosahexaenoic acid (DHA) was increased more in the liver than in kidney, lung, and spleen. The heart incorporated seven times more EPA than DHA, which is more than all other organs and described here for the first time in ruminants. In addition, the heart had the highest proportions of α-linolenic acid (18:3n-3) and linoleic acid (18:2n-6) of all organs. The proportions of polyunsaturated FA in the lung and spleen were exceptionally low compared to heart, liver, and kidney. In conclusion, it was shown that the response to FO in the distribution of dietary n-3 FA was organ-specific while proportions of n-6 FA were quite inert with respect to the type of oil supplemented.     

Effect of dietary organic selenium on fatty acid composition in nutria (Myocastor coypus Mol.) livers

Young, female nutrias (n = 13) were fed a diet supplemented with 0.36 mg/kg selenium in selenium‐enriched yeast (SeY; Sel‐Plex; Alltech, Inc., Nicholasville, KY) for 60 days (total Se concentration in the basal diet was ～0.1 mg/kg). Concentrations of fatty acids (FA) in the liver were compared to those of nutrias on a control diet (n = 11). Animals were sacrificed at 8 months of age and liver samples (approximately 30 g) were collected. The gas‐chromatographic analysis of tissue samples from the experimental group revealed a significant decrease in saturated fatty acids (p<0.001), monounsaturated fatty acid (p = 0.006), and polyunsaturated fatty acid (PUFA) (p = 0.02) compared to controls. The linoleic and linolenic acids, which are precursors of n‐6 and n‐3 PUFA, respectively, were significantly lower (p = 0.01 and p<0.001, respectively) in the supplemented group. The n‐6 to n‐3 PUFA ratio was significantly affected (p = 0.001) by the SeY dietary supplement (13.17 vs. 8.93, respectively).     

Dietary saturated and omega‐3 fatty acids affect growth and fatty acid profiles of Malaysian mahseer

The current study was conducted to determine optimal levels of dietary saturated fatty acids (SFA), n‐3 PUFA and to study potential n‐3 sparing effect of dietary SFA for Malaysian mahseer Tor tambroides. Juvenile T. tambroides were fed four trial diets with similar basal composition but different oil mixtures in a 2 × 2 factorial experimental design for 10 weeks. The two factors were the levels of dietary SFA and the levels of dietary n‐3 PUFAs. Growth performance and fatty acid profile of tissues were analyzed at the end of the experiment. Significant differences in growth performance were observed among treatments, and fish fed the diet low in n‐3 and high in SFA showed the best growth performance. T. tambroides fed the high n‐3 diets showed a significantly higher (p<0.05) muscle total n‐3 PUFA content compared to fish fed the low n‐3 diets. The highest 22:6 n‐3 and total n‐3 PUFA content of the liver were also observed in fish fed the low n‐3 and high SFA diet. However, the significant interaction (p<0.05) between dietary SFA and n‐3 PUFA levels was observed for the total n‐3 PUFA content of both muscle and liver tissues, suggesting an n‐3 sparing action by dietary SFA. The results of this study suggest that 2.5% n‐3 PUFA in the diet of T. tambroides, with an SFA to n‐3 ratio of 15.3, is sufficient to provide the best growth performance and to retain the n‐3 content of tissues. Practical applications: The continuous increase of world population and growth of aquaculture industry put severe pressure on the marine resources such as fish oil and fishmeal. Here we show that fish oil can be substituted with palm oil, a cheaper and more available source of oil in tropical countries, in the diet of Malaysian mahseer without a reduction of growth. Moreover, palm oil as a source of SFA may spare omega‐3 in the fish tissues. Omega‐3 is an essential fatty acid for humans as final consumer of edible fish.     

Replacement of Marine Fish Oil with de novo Omega-3 Oils from Transgenic Camelina sativa in Feeds for Gilthead Sea Bream (Sparus aurata L.)

Omega‐3 (n‐3) long‐chain polyunsaturated fatty acids (LC‐PUFA) are essential components of the diet of all vertebrates. The major dietary source of n‐3 LC‐PUFA for humans has been fish and seafood but, paradoxically, farmed fish are also reliant on marine fisheries for fish meal and fish oil (FO), traditionally major ingredients of aquafeeds. Currently, the only sustainable alternatives to FO are vegetable oils, which are rich in C₁₈ PUFA, but devoid of the eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) abundant in FO. Two new n‐3 LC‐PUFA sources obtained from genetically modified (GM) Camelina sativa containing either EPA alone (ECO) or EPA and DHA (DCO) were compared to FO and wild‐type camelina oil (WCO) in juvenile sea bream. Neither ECO nor DCO had any detrimental effects on fish performance, although final weight of ECO‐fed fish (117 g) was slightly lower than that of FO‐ and DCO‐fed fish (130 and 127 g, respectively). Inclusion of the GM‐derived oils enhanced the n‐3 LC‐PUFA content in fish tissues compared to WCO, although limited biosynthesis was observed indicating accumulation of dietary fatty acids. The expression of genes involved in several lipid metabolic processes, as well as fish health and immune response, in both liver and anterior intestine were altered in fish fed the GM‐derived oils. This showed a similar pattern to that observed in WCO‐fed fish reflecting the hybrid fatty acid profile of the new oils. Overall the data indicated that the GM‐derived oils could be suitable alternatives to dietary FO in sea bream.     

Dietary fish oil dose-response effects on ileal phospholipid fatty acids and contractility

We have reported that dietary fish oil (FO) leads to the incorporation of long-chain n−3 PUFA into the gut tissue of small animal models, affecting contractility, particularly of rat ileum. This study examined the FO dose response for the incorporation of n−3 PUFA into ileal tissue and how this correlated with in vitro contractility. Groups of ten to twelve 13-wk-old Wistar-Kyoto rats were fed 0, 1, 2.5, and 5% FO-supplemented diets balanced with sunflower seed oil for 4 wk, after which ileal total phospholipid FA were determined and in vitro contractility assessed. For the total phospholipid fraction, increasing the dietary FO levels led to a significant increase first evident at 1% FO, with a stepwise, nonsaturating six-fold increase in n−3 PUFA as EPA (20∶5n−3), DPA (docosapentaenoic acid, 22∶5n−3), and DHA, but mainly as DHA (22∶6n−3), replacing the n−6 PUFA linoleic acid (18∶2n−6) and arachidonic acid (20∶4n−6) over the dosage range. There was no difference in KCl-induced depolarization-driven contractility. However, a significant increase in receptor-dependent maximal contractility occurred at 1% FO for carbachol and at 2.5% FO for prostaglandin E₂, with a concomitant increase in sensitivity for prostaglandin E₂ at 2.5 and 5% FO. These results demonstrate that significant increases in ileal membrane n−3 PUFA occurred at relatively low doses of dietary FO, with differential receptor-dependent increases in contractility observed for muscarinic and prostanoid agonists.     

Fatty Acid Profile of Sunshine Bass: I. Profile Change is Affected by Initial Composition and Differs Among Tissues

Fatty acid (FA) composition of fillet tissue can be tailored by transitioning fish from alternative lipid-based, low long-chain polyunsaturated fatty acid (LC-PUFA) grow-out feeds to high LC-PUFA "finishing" feeds. To address whether grow-out feed composition influences the responsiveness of fillet tissue to finishing, sunshine bass (SB, Morone chrysops x M. saxatilis) were reared to a submarketable size on grow-out feeds containing fish oil (FO) or a 50:50 blend of FO and coconut (CO), grapeseed (GO), linseed (LO), or poultry (PO) oil. For the final 8 weeks of the trial, fish were either maintained on assigned grow-out feeds or finished with the 100% FO feed. Production performance was unaffected by dietary lipid source, but fillet FA profile generally conformed to nutritional history. Regardless of grow-out regimen, finishing had a significant restorative effect on fillet FA composition; however, complete restoration of control levels of 20:5n-3, 22:6n-3, total LC-PUFA and n-3:n-6 FA ratio was achieved only among fish fed the CO-based grow-out feed. Saturated fatty acids (SFA) appear to be preferential catabolic substrates, whereas medium-chain and long-chain PUFA are selectively deposited in tissues. Provision of SFA in grow-out feeds appears to optimize selective FA metabolism and restoration of beneficial fillet FA profile during finishing.     

Fatty Acid Composition of Tropical Fish Depends on Reservoir Trophic Status and Fish Feeding Habit

Eutrophication results in a deficiency of n‐3 LC‐PUFA (long‐chain polyunsaturated fatty acids) in aquatic food chains, affecting fish nutrition and physiology. The trophic transfer of FA (fatty acids) to fish species of different feeding habits was investigated in two reservoirs in southeast Brazil—the mesotrophic Ponte Nova Reservoir (PN) and the hypereutrophic Billings Reservoir (Bil). Total FA profile of stomach contents and adipose tissue, triacylglycerols (TAG), and phospholipids (PL) from liver and muscle of the omnivorous Astyanax fasciatus and the carnivorous Hoplias malabaricus were analyzed by gas chromatography. A prevalence of n‐6PUFA, as 18:2n‐6 (linoleic acid) and 20:4n‐6 (arachidonic acid, ARA) was observed in the stomach contents and in the tissues of A. fasciatus from the PN reservoir. In contrast, n‐3 LC‐PUFA, as 20:5n‐3 (eicosapentaenoic acid, EPA) was accumulated in fish tissues from Bil, resulting in higher n3/n6 and EPA/ARA ratios, compared to fish from PN. This differential FA accumulation was also observed for H. malabaricus, but differences were slightly minor, and no changes were observed in the EPA/ARA ratios between fish from both reservoirs. Regardless reservoir, FA profiles of TAG resembled that of their diet, whereas FA profiles of PL were more conservative and mainly comprised by LC‐PUFA. We conclude that reservoir trophic status affected the FA composition of food resources available to these fish species, resulting in differential allocation of n‐3 and n‐6 FA. As expected, FA profile of the investigated fish species also reflected their feeding habit and physiological demands.     

Preferential Partitioning of Rumen-Protected n-3 and n-6 Fatty Acids into Functionally Different Adipose Tissues

Lipids are stored at various sites inside the body as adipose tissue (AT). These include subcutaneous, abdominal, and intermuscular locations. The AT substantially differ in their metabolic function. It is, however, unclear whether AT have specific requirements for individual essential n-3 and n-6 fatty acids (FA). If so, control mechanisms would partition FA from the blood. To investigate the hypothesis of a selective FA incorporation, 18 beef heifers were fed diets supplemented with 60 g/kg diet with lipids from either fish oil (FO) or sunflower oil (SO). The lipids had partially been rumen-protected to ruminal biohydrogenation of n-3 and n-6 FA. The AT analyzed for n-3 and n-6 FA by gas chromatography were obtained from pericardial, longissimus thoracis (LT) intermuscular, perirenal, and subcutaneous sites. The greatest proportions of n-3 and n-6 FA were found in the pericardial AT. Despite generally low abundance, n-3 FA proportions increased with FO compared to SO supplementation in all AT, but to a different extent. No such partitioning was found for the n-6 FA when supplementing SO. Concomitantly, the n-6/n-3 FA ratio was reduced with FO in all AT, except in the pericardial AT. The latter has specific metabolic functions and thus appears to be quite resistant to diet-induced changes in FA profile in order to maintain its function. The present findings showed the special role of specific n-3 and n-6 FA in bovine AT.     

Survey of qualitative traits of European sea bass cultivated in different rearing systems

The purpose of this study was to evaluate the main qualitative traits of European sea bass fattened in farms adopting different rearing techniques (offshore cages, inshore cages, land‐based basins) but fed the same diets in each production cycle, in a three year survey (2006, 2007, 2008). Three farms were chosen for each rearing technique and two sampling sessions of ten fish each were carried out for each rearing cycle. Proximate composition, fatty acid profile, and cholesterol content were evaluated in the fillet of marketable size fish as well as morpho‐biometric parameters and indices. Diets administered in 2008 had higher amounts of lipids, lower proportions of n–3 polyunsaturated fatty acids (PUFA) and higher proportions of n–6 PUFA compared to 2006 and 2007 diets. The chemical and fatty acid composition of the fish fillet was affected by the diet composition: fish fattened in 2008 exhibited statistically higher amounts of fat and cholesterol, lower proportions of n–3 PUFA and higher proportions of n–6 PUFA in comparison with fish cultivated in 2006 and 2007. Fish cultivated in cages, both offshore and inshore cages, exhibited leaner fillets, lower amounts of cholesterol and higher proportions of n–3 PUFA than fish cultivated in basins. Practical applications: In this study we have analyzed the combined effects of feeding and rearing systems of sea bass in a 3‐year survey for the first time. The results showed that feeding is the main factor affecting fish quality as regards both the chemical composition and the fatty acid profile. The partial substitution of fish meal and fish oil with vegetable sources, with the aim of saving the wild fish biomass as well as formulating less expensive diets, strongly alters the fillet composition. We also showed that the rearing system of fish in offshore cages makes it is possible to obtain better quality products.     

Modification of membrane fatty acid composition,eicosanoid production,and phospholipase a activity in Atlantic Salmon (Salmo salar) gill and kidney by dietary lipid

Atlantic salmon post-smolts were fed diets containing either fish oils (Fosol, FO and Marinol, MO) rich in long-chain n-3 polyunsaturated fatty acids (PUFA), or plant oils rich in 18:2n-6 (sunflower oil, SO) or 18:3n-3 (linseed oil, LO) for 12 wk. The major PUFA in individual phospholipids from gill and kidney were related to the dietary lipid intake. Levels of n-6 PUFA were highest while levels of n-3 PUFA were lowest in fish fed SO. Fish fed LO generally had lower levels of 20:4n-6 compared to the other treatments while fish fed SO generally had the highest levels of 20:4n-6. In all phospholipid classes except phosphatidylinositol (PI) 20:5n-3 was greatest in fish fed MO followed by FO, LO, and SO. In PI, 20:5n-3 was also highest in fish fed MO but those fed LO contained more 20:5n-3 than those fed FO. This resulted in the ratio of the eicosanoid precursors, 20:4n-6/20:5n-3, being significantly greater in fish fed SO, for all phospholipid classes, compared to fish fed the other three dietary oils. The activity of gill phospholipase A was greatest in fish fed FO and was lowest in fish fed SO. The concentration of PGF_3α was significantly increased in gill homogenates from fish fed MO compared to the other three treatments while PGF_2α was significantly increased in fish fed SO compared to those fed LO. The concentration of PGE₃ was significantly reduced in kidney homogenates from fish fed SO compared to the other three treatments while PGE₂ was significantly increased in fish fed SO compared to those fed either FO or LO.