Growth, survival, lipid composition and pigmentation of turbot (Scophthalmus maximus) larvae fed live-prey enriched in Arachidonic and Eicosapentaenoic acids

Turbot larvae were fed live-prey enriched with different levels of arachidonic (ARA) and eicosapentaenoic (EPA) acids to study the effects of these fatty acids on body composition and pigmentation success. Significantly reduced pigmentation was obtained in those fish fed medium and high ARA diets for 43 days. Growth and survival were the same for all groups. The incorporation of ARA and EPA in fish eyes, brains, livers and carcasses reflected the percentage of these fatty acids in the diets. ARA accumulation was similar in all tissues, but brain accumulated EPA was less efficient than the other tissues examined. A highly significant, negative correlation was found between the %ARA in turbot juvenile brain total lipids and pigmentation success. A weaker, positive correlation was found between brain EPA and pigmentation. Increasing dietary ARA affected the fatty acid composition of turbot brain phosphoglycerides more than increasing dietary EPA, especially in phosphatidylinositol (PI) and phosphatidylethanolamine (PE). A negative relationship was found between percentage normal pigmentation and ARA levels in brain phosphatidylcholine (PC), PE and phosphatidylserine (PS). Elevated levels of ARA in PI also resulted in malpigmented juveniles, but EPA:ARA ratios ≥1 in PI were associated with normal pigmentation. We conclude that, given a sufficiency of dietary docosahexaenoic acid (DHA), the optimum dietary level of EPA is not a function of DHA, but of dietary ARA.     

Effects of arachidonic acid on pigmentation and fatty acid composition of Japanese flounder, Paralichthys olivaceus (Temminck and Schlegel)

The dietary effect of arachidonic acid (20:4n-6, AA) on the composition of the head and the body, and on the pigmentation of Japanese flounder, Paralichthys olivaceus (T. & S.), was studied by means of microbound diets. Increasing levels of this essential fatty acid produced higher growth and pigmentation success in juveniles after 45 days of feeding. The role played by AA in the composition of phosphatidylinositol and eicosanoid synthesis is discussed in relation to the normal function of the neural system and the production of hormones involved in the metamorphosis and pigmentation of flatfish.     

Effects of Rotifer and Artemia Fatty-Acid Enrichment on Survival, Growth and Pigmentation of Summer Flounder Paralichthys dentatus Larvae

Abstract— Enrichment of live food for marine fish larvae with highly unsaturated fatty acids (HUFA) has been shown to improve survival, growth and stress resistance in many species and to decrease pigmentation abnormalities in flatfish. In order to aid the developing summer flounder industry, we conducted an experiment in which summer flounder larvae were fed diets differing in HUFA composition to determine whether enrichment with a commercially available product would increase survival and growth and reduce the incidence of abnormal pigmentation. We also examined whether growing unenriched rotifers on different species of algae would affect the survival, growth and pigmentation of the flounder larvae to which they were fed. Growth of summer flounder larvae was significantly better when they were fed HUFA-enriched Mtifers and Artemia rather than unenriched and, among the unenriched treatments, was significantly better when the larvae were fed rotifers raised on Isochrysis galbana rather than on Tetraselmis suecica . The percentage of larvae that failed to complete metamorphosis during the experiment was significantly higher in the unenriched treatments than in the enriched treatments. Neither survival nor percentage of individuals with pigmentation abnormalities were significantly different among the treatments.     

Nutritional comparison in muscle of wild,pond and factory cultured Japanese flounder (Paralichthys olivaceus) adults

Muscle proximate composition, amino acid profiles, fatty acid compositions and selected minerals of wild, pond and factory cultured Japanese flounder adults were compared in this study to elucidate their nutritive values and dietary nutrition requirements. Wild and pond cultured Japanese flounder flesh had higher crude proteins, but crude lipid contents of factory cultured fish were 3.8~4.0 fold greater. Major amino acids in Japanese flounder were aspartic acid, glutamic acid and lysine. Wild fish had higher levels of total amino acids, essential amino acids, nonessential amino acids and half‐essential amino acids and the contents in pond cultured samples were similar. Arachidonic acids (ARA), eicosapentaenoic acids (EPA), docosahexaenoic acids (DHA), polyunsaturated fatty acids (PUFA), DHA + EPA and n–3 PUFA in wild Japanese flounder were significantly higher than that in factory cultured fish, whereas fatty acid levels were close between pond cultured and wild fish. Japanese flounder were rich in zinc, iron and selenium, but poor in copper, chromium and nickel. Results indicated wild Japanese flounder had higher nutritional value and better meat quality, but the nutritional compositions of pond cultured fish were close to wild Japanese flounder, which suggested that pond culture of Japanese flounder offers broad application prospects.     

Influence of different dietary amino acid patterns on growth and body composition of juvenile Japanese flounder, Paralichthys olivaceus

A feeding trial using five semi-purified diets (50% crude protein) was conducted to investigate the effects of different dietary amino acid patterns on growth and body composition of juvenile Japanese flounder. The control diet contained casein and gelatin as intact protein sources and four other diets contained 30% casein–gelatin (2:1, w/w) and 20% crystalline amino acids (CAA). CAA were added to the diets to simulate the amino acid pattern found in red sea bream egg protein (REP), Japanese flounder larvae whole body protein (FLP), Japanese flounder juvenile whole body protein (FJP), and brown fish meal protein (BFP), respectively. The test diets were fed to triplicate groups of juveniles (2.75±0.05 g) twice a day for 40 days to evaluate weight gain, survival, feed conversion efficiency (FCE), protein efficiency ratio (PER), and apparent protein utilization (APU). The apparent retention of total dietary amino acids in the whole body and A/E ratios of the whole body were also evaluated. The highest weight gain was observed in fish fed the diet containing the dietary amino acid pattern of BFP followed by fish fed the control, FJP, FLP and the REP diets. Percent survival, FCE, PER and APU were also significantly (P<0.05) affected by the amino acid pattern in the diets, indicating the highest value in fish fed the BFP diet. Except for a few amino acids, the amino acid composition of the whole body did not show marked differences with different dietary amino acid pattern. Results suggest that BFP could be more suitable as a reference amino acid pattern in the diet of juvenile Japanese flounder compared to the amino acid pattern of FLP, FJP or REP.     

Effect of different dietary taurine levels on the conjugated bile acid composition and growth performance of juvenile and fingerling Japanese flounder Paralichthys olivaceus

This study investigated the effects of different taurine levels on the conjugated bile acid composition and growth performance of juvenile and fingerling Japanese flounder. Five level diets of dietary taurine were prepared by the supplementation of taurine (0, 0.1, 0.2, 0.5 and 1.5%) to a basal composition. Fish meal washed with 70% ethanol to remove taurine was used as the sole protein source. Two feeding experiments were carried out at 20 °C by using different sized fish (BW: 0.7 g and 9.6 g). Both size groups of fish were fed the experimental diets for 6 weeks. At the end of experiments, fish were weighed and stored at − 80 °C for analysis of free amino acids and conjugated bile acids composition. The body weight and feed efficiency of Japanese flounder were improved by taurine supplementation in the experimental diets. The taurine contents of the whole body and tissues increased with the increase of the taurine supplementation. The conjugated bile acids in gall bladder were composed with taurocholic acid (Expt.I: 33.0-146.8 mg/ml; Expt.II: 64.8-145.3 mg/ml) and taurochenodeoxycholic acid (Expt.I: 0.8-5.5 mg/ml; Expt.II: 3.5-4.9 mg/ml). These bile acids increased with the increase of the dietary taurine level. Taurocholic acid accounted for more than 95% of the total conjugated bile acids. No other conjugated bile acids except the taurine conjugated bile acids were detected in the gall bladder of Japanese flounder. This means that taurine is the sole amino acid to conjugate bile acid in Japanese flounder. Dietary taurine intake affects the conjugated bile acid composition in juvenile and fingerling Japanese flounder.     

Effects of dietary fish oil replacement by microalgae raw materials on growth performance,body composition and fatty acid profile of juvenile olive flounder,Paralichthys olivaceus

Replacing dietary fish oil with DHA‐rich microalgae Schizochytrium sp. and EPA‐rich microalgae Nannochloropsis sp. for olive flounder (Paralichthys olivaceus) was examined. Three experimental isonitrogenous and isolipidic diets with lipid source provided by 50% fish oil (F50S50), 50% (M50F25S25) and 100% microalgae raw material (M100) respectively were compared with a soybean oil (S100) diet as control. Triplicate groups of olive flounder juveniles (16.5 ± 0.91 g) were fed the experimental diets, and a group was fed the control diets for 8 weeks in a recirculation system. Results showed feed efficiency and growth performance were not significantly changed when fish oil (FO) was totally substituted by soybean oil (SO) or microalgae raw material (MRM). The whole‐body composition, lipid content of liver and muscle, and lipid composition of plasma were not significantly influenced by the total substitution of FO by MRM. The polyunsaturated fatty acids (PUFA) content of muscle and liver declined in fish fed S100 diet, whereas it was not significantly reduced in fish fed M50F25S25 and M100 diets. The total substitution of FO by MRM not only maintained the levels of arachidonic acid, EPA or DHA but also increased n‐3/n‐6 ratio. In conclusion, MRM as the sole lipid source is sufficient to obtain good feed efficiency, growth performance and human health value in olive flounder juveniles.     

正常和白化褐牙鲆皮肤和肌肉中DHA和EPA含量的比较

利用气相色谱法对相同养殖条件下生长的正常和白化褐牙鲆(Paralichthys olivaceus)的皮肤和肌肉组织中的DHA和EPA含量进行了比较分析。结果显示，正常和白化褐牙鲆的皮肤和肌肉中EPA含量相近，但白化个体皮肤中DHA含量显著低于正常个体，约为后者的1／2。而两者肌肉中的DHA含量则没有显著差异。同时，白化个体皮肤和肌肉组织中的DHA／EPA比值略低于正常个体。这一结果证明白化褐牙鲆皮肤蓄积或利用DHA的能力要低于正常褐牙鲆。关于鲆鳔类白化现象同鱼体对饵料中脂肪酸类物质的利用率之间的关系有待深入研究。     

营养因素对比目鱼形变影响的研究进展

营养因素是影响比目鱼形变的主要因素。介绍了比目鱼的形变并分析了轮虫和桡足类动物的主要营养成分的差异,并着重介绍了甲状腺激素、维生素A、脂肪酸和能量对比目鱼着色和眼睛移位的影响。     

Effects of essential fatty acid-deficient diets on growth, mortality, tissue histopathology and fatty acid compositions in juvenile turbot (Scophthalmus maximus)

Three diets in which the lipid component was supplied either as fish oil (FO), linseed oil (LO) or olive oil (OO) were fed to duplicate groups of juvenile turbot (Scophthalmus maximus) of initial weight 1.2 g for a period of up to 12 weeks. The latter two diets resulted in a significant reduction in specific growth rate and an increased mortality compared to the FO (control) fed fish. A liver histopathology was evident in around half of the fish fed the LO and OO diets but was absent in fish fed FO. The lesion showed indications of cellular alterations consisting of foci of densely basophilic cells but without evidence of inflammatory activity. The total lipid fatty acid composition of the carcass from fish fed LO had increased percentages of 18:2n-6 and 18:3n-3, but decreased percentages of all other polyunsaturated fatty acids (PUFA) including the physiologically important 20:4n-6, 20:5n-3 and 22:6n-3, compared to fish fed FO. Almost 2/3 of the total fatty acids in the carcass of OO-fed fish were monounsaturated while the percentages of total saturated fatty acids and all other PUFA, except 18:2n-6, were significantly reduced compared to fish fed FO. Broadly similar effects on total lipid fatty acid composition were observed in liver. In the liver glycerophospholipid classes of fish fed LO, percentages of 18:2n-6, 18:3n-3 and 20:3n-3 were significantly increased whereas all C20 and C22 PUFA, with the exception of 20:5n-3 in PI, were significantly reduced compared to fish fed FO. The liver glycerophospholipids of fish fed OO all showed significantly increased total monounsaturates, 18:2n-6, 20:2n-6, 18:2n-9 and 20:2n-9 as well as reduced percentages of 20:4n-6 and 22:6n-3, compared to fish fed FO. The brain glycerophospholipids showed broadly similar changes in response to dietary treatment although the magnitude of fatty acid alterations was less than those observed in liver. The greater mortalities in the OO-fed fish compared to the LO-fed fish suggests that incorporation of 18:3n-3 into tissue phospholipids can offset losses of long-chain PUFA more effectively than incorporation of 18:1n-9. However, levels of dietary long-chain PUFA must be optimised to allow normal growth and development. We conclude that the very low flux through the fatty acid desaturase/elongase pathways in turbot is not up-regulated by diets deficient in 20:5n-3 and 22:6n-3.     

Dietary lipid sources for seabream and seabass: growth performance, tissue composition and flesh quality

Due to its traditionally good availability, digestibility and high content of n ? 3 HUFA, fish oil is the main lipid source in fish feeds. However, world demand for this product has grown significantly in recent years, whereas its production, based on fisheries landings, is static. The purpose of the present study was to assess the effect of partial replacement of fish oil in compound diets for gilthead seabream and seabass, by several vegetable oil sources, on growth, dietary fatty acid utilization and flesh quality. Five iso‐energetic and isoproteic experimental diets were formulated (25% lipid content). Fish oil was the only added lipid source in the control (FO) diet, and it was included in the other experimental diets at a level high enough (40% of FO diet) to keep the n ? 3 HUFA levels well over 3% in order to cover the essential fatty acid requirements of these species. Fish oil was replaced by soyabean oil (SO), rapeseed oil (RO) and linseed oil (LO) or a mixture (Mix) of them. Feed intake in all dietary groups was in the range of results obtained for commercial diets in both species, and growth and feed utilization were very good. The results show that, providing a minimum content of essential fatty acids in the diet, it is possible to replace up to 60% of the fish oil by SO, LO and RO or a mixture of them in diets for seabream and seabass, without compromising fish growth. Fatty acid composition of liver and muscle reflected that of the diet, but utilization of dietary lipids differed between these two tissues and was also different for the different fatty acids. Despite reduction in dietary saturated fatty acids by the inclusion of vegetable oils, their levels in fish liver were as high as in fish fed the fish oil diet, whereas, in muscle, levels were reduced according to that in the diet. Linoleic and linolenic acids were accumulated in the liver proportionally to their levels in the diet, suggesting a lower oxidation of these fatty acids in comparison to other 18C fatty acids. Regarding eicosapentaenoic acid (20 : 5n ? 3; EPA), docosahexaenoic acid (22 : 6n ? 3; DHA) and arachidonic acid (20 : 4n ? 6; ARA), these essential fatty acids were reduced in the liver at a similar rate, whereas DHA was preferentially retained in the muscle in comparison with the other fatty acids, denoting a higher oxidation particularly of EPA, in the muscle. Some other PUFA increased despite their low dietary levels in seabream fed LO diets and in seabass fed SO diet, suggesting the stimulation of delta‐6 and delta‐5 desaturase activity in marine fish. Despite differences in fatty acid composition, fillet of fish fed vegetable oils was very well accepted by trained judges when assessed cooked.     

A combination of plant oils promotes adequate growth of the freshwater catfish Rhamdia quelen (Quoy & Gaimard 1824)

Essential fatty acids should be included in the diet to ensure adequate fish growth. Despite the great number of studies on fatty acid nutrition of fish, there are still several unknowns. The aim of the present study was to investigate fatty acid nutrition of jundiá, a Latin American freshwater catfish. Four diets were formulated containing (i) coconut oil (?C, negative control), (ii) coconut oil + high‐docosahexaenoic‐acid‐fish oil (+C, positive control) and coconut + sunflower + linseed oils at different ratios, producing either (iii) a diet rich in linoleic acid (LA) (HighLA) or 4) a diet low in LA (LowLA). All diets contained significant amounts of saturated fatty acids (at least 57.5% total fatty acids in HighLA) and monounsaturated fatty acids (at least 19.1% total fatty acids in ?C). Diets were fed to jundiá fingerlings (1.5 g) for 70 days; growth, body composition and liver histology were evaluated. The ?C diet, without essential fatty acids, promoted significantly lower fish growth, body fat accumulation and hepatic lipidosis. Fish fed HighLA and LowLA diets presented similar growth as fish fed +C diet. These findings suggest that diet formulations for jundiá catfish fingerlings can include only plant oils without negative effect on growth, survival, body composition, fish health or parameters of feed utilization (ingestion rate and protein utilization).     

微粒饲料中以微藻粉替代鱼油对牙鲆(Paralichthys olivaceus)稚鱼生长存活和脂肪酸组成的影响

以18日龄的牙鲆(Paralichthys olivaceus)稚鱼为研究对象,通过11 d 的生长实验,研究了添加不同比例的微藻粉替代鱼油对牙鲆稚鱼生长、存活率和脂肪酸组成的影响。以鱼油组(FO)为对照组,以裂壶藻粉(Schizochytrium sp.)、微绿球藻粉(Nannochloropsis sp.)和橄榄油替代不同比例的鱼油,配制成5组等氮等能的实验饲料,分别命名为鱼油组(FO),50%混合替代组(M50)、100%混合替代组(M100)、100%裂壶藻橄榄油替代组(S100)、100%微绿球藻橄榄油替代组(N100)。结果显示,微藻粉替代鱼油对牙鲆稚鱼的生长无显著影响;含有裂壶藻的各饲料组(M50、M100、S100)成活率显著高于 FO 组和 N100组(P?0.05);微藻粉替代鱼油不影响牙鲆稚鱼主要脂肪酸的组成;Person相关性分析发现,C14：0、C16：1n-7、C18：2n-6、C20：0、C18：3n-3、C22：0、C20：4n-3、EPA、C22：5n-6和 DHA 的百分含量均与其饲料中的百分含量呈显著正相关(P<0.05);总饱和脂肪酸、总单不饱和脂肪酸、n-3多不饱和脂肪酸的百分含量以及 DHA/EPA 比率均与其饲料组成表现出显著正相关(P<0.05)。综上所述,微藻作为脂肪源替代鱼油完全可以满足牙鲆稚鱼的生长和发育,各种脂肪酸均可以被牙鲆稚鱼充分消化和吸收,并且添加两种微藻后提高了稚鱼的 DHA 含量和 DHA/EPA 比率,与鱼油对照组相比显著提高了牙鲆稚鱼的成活率。因此,以微藻替代鱼油在牙鲆稚鱼的培育中是可行的。     

Effects of docosahexaenoic, eicosapentaenoic, and arachidonic acids on the early growth, survival, lipid composition and pigmentation of yellowtail flounder (Limanda ferruginea): a live food enrichment experiment

The role of dietary ratios of docosahexaenoic acid (DHA, 22:6n−3), eicosapentaenoic acid (EPA, 20:5n−3) and arachidonic acid (AA, 20:4n−6) on early growth, survival, lipid composition, and pigmentation of yellowtail flounder was studied. Rotifers were enriched with lipid emulsions containing high DHA (43.3% of total fatty acids), DHA+EPA (37.4% and 14.2%, respectively), DHA+AA (36.0% and 8.9%), or a control emulsion containing only olive oil (no DHA, EPA, or AA). Larvae were fed differently enriched rotifers for 4 weeks post-hatch. At week 4, yellowtail larvae fed the high DHA diet were significantly larger (9.7±0.2 mm, P<0.05) and had higher survival (22.1±0.4%), while larvae fed the control diet were significantly smaller (7.3±0.2 mm, P<0.05) and showed lower survival (5.2±1.9%). Larval lipid class and fatty acid profiles differed significantly among treatments with larvae fed high polyunsaturated fatty acid (PUFA) diets having higher relative amounts of triacylglycerols (18–21% of total lipid) than larvae in the control diet (11%). Larval fatty acids reflected dietary levels of DHA, EPA and AA while larvae fed the control diet had reduced amounts of monounsaturated fatty acids (MUFA) and increased levels of PUFA relative to dietary levels. A strong relationship was observed between the DHA/EPA ratio in the diet and larval size (r²=0.75, P=0.005) and survival (r²=0.86, P=0.001). Following metamorphosis, the incidence of malpigmentation was higher in the DHA+AA diet (92%) than in all other treatments (50%). Results suggest that yellowtail larvae require a high level of dietary DHA for maximal growth and survival while diets containing elevated AA exert negative effects on larval pigmentation.     

Restoration of the fatty acid composition of red seabream (Pagrus auratus) using a fish oil finishing diet after grow-out on plant oil based diets

This study evaluated the potential for manipulating the fatty acid composition of juvenile red seabream, Pagrus auratus. Prior to the start of the study, three groups of fish had been reared for 3 months on a fish oil based diet or diets where the added fish oil had been replaced with either canola or soybean oil. In the present study, fish that had previously been fed either the canola or soybean oil diets were fed a fish oil based diet. Three additional treatments included fish being maintained on their original diets of fish oil, canola oil or soybean oil. Fish were fed their respective diets twice daily to apparent satiety for 32 days. Samples of fish from each treatment were collected after 0, 1, 2, 4, 8, 16 and 32 days. Composition and growth of the fish were determined at each sample point. Most treatments showed no differences in growth performance, although fish fed a fish oil diet after previously being fed a soybean oil diet showed slightly better growth. No significant differences among treatments were observed in proximate composition of the fish, although there was a significant increase in total fat and individual fatty acid (g kg^?1 live‐weight) content of the fish from all treatments over the period of the study. No significant changes in the relative fatty acid composition (% of total fatty acids) over time were observed in the three treatments where fish were maintained on their original diets. In contrast, fish that were previously fed either the canola or soybean oil diets and were then fed a fish oil diet had significant changes in both the relative (% of total fatty acids) and absolute (g kg^?1 live‐weight) fatty acid content. Key changes observed included a decrease in the relative levels of polyunsaturated fatty acids (PUFA) such as 18 : 2n ? 6 and 18 : 3n ? 3. Increases in the relative levels of the long‐chain polyunsaturated fatty acids (lcPUFA) 20 : 5n ? 3 and 22 : 6n ? 3 were also observed in both treatments. The rates of absolute (g kg^?1 live‐weight) change/accumulation of these fatty acids followed an exponential equation that differed for each fatty acid in each treatment. Examination of the retention efficiency of specific fatty acids also showed marked differences between fatty acids within treatments and also differences between treatments. Biologically important fatty acids such as 20 : 5n ? 3 and 22 : 6n ? 3 had only moderate retention efficiencies and these were unaffected by treatment. In contrast, the retention efficiencies of 18 : 2n ? 6 and 18 : 3n ? 3 suggested selective retention of these fatty acids when fed fish oil diets, but moderate catabolism when fed the plant oil diets. There were also high retention efficiencies of most saturated and monounsaturated fatty acids suggestive of active retention and/or active synthesis of these fatty acids by the fish. The results of this study, particularly the increases in lcPUFA, support the usefulness of a fish oil based finisher diet for fish raised predominantly on plant oil based diets.     

Essentiality of Dietary n-3 Highly Unsaturated Fatty Acids in Juvenile Japanese Flounder Paralichthys olivaceus

This study was conducted to confirm the essentiality of dietary n-3 highly unsaturated fatty acids (n-3 HUFA) and to investigate the effects of dietary lipid sources on growth performance, liver, and blood chemistry in juvenile Japanese flounder. Three replicate groups of fish (average weighing 3.0 g) were fed experimental diets containing lauric acid ethyl ester, soybean oil, soybean and linseed oils mixture, and squid liver oil as lipid sources for 13 wk. No significant difference was observed in survival among all groups ( P >0.05). Weight gain, feed efficiency and protein efficiency ratio of fish fed the squid liver oil diet containing high n-3 HUFA level were significantly higher than those of fish fed the other diets ( P 0.05). Saturated and monounsaturated fatty acids of liver polar and neutral lipid fractions in fish fed the diet containing lauric acid tended to increase compared to those of the other groups. Fish fed the diets containing soybean and/or linseed oils, which contained high contents of 18:2n-6 and 18:3n-3, respectively, showed the highest contents of 18:2n-6 and 18:3n-3 in both lipid fractions of the liver ( P 0.05). Significantly higher content of n-3 HUFA was observed in both lipid fractions of the liver from fish fed the diet containing squid liver oil than for fish fed the other diets ( P 0.05). Total cholesterol, glucose, and glutamic-oxaloacetic acid transaminase in plasma were significantly affected by dietary lipids ( P 0.05). Histologically, the liver of fish fed the diet containing squid liver oil had a clear distinction between nuclear and cytoplasm membranes; however, cytoplasm of fish fed the diets containing lauric acid and soybean oil was shrunken, and the hepatic cell outline was indistinguishable. It is concluded that the dietary n-3 HUFA is essential for normal growth, and that the dietary lipid sources affect growth performance, liver cell property, and blood chemistry in juvenile Japanese flounder.     

Influence of nutrition on the lipid quality of pond fish: common carp (Cyprinus carpio) and tench (Tinca tinca)

Like marine fish freshwater fish are an important source of essential fatty acids for human nutrition. However, the fatty acid composition of pond fish can vary considerably and strongly depends on that of the ingested food. Investigations on the fatty acid composition of common carp (Cyprinus carpio) and tench (Tinca tinca) have shown that different methods of rearing and feeding cause substantial variations in the proportions of the n-6 and n-3 polyunsaturated fatty acids of these fish species. Carp reared on the basis of natural food in ponds exhibit high contents of n-6 as well as n-3 fatty acids in their muscle triacylglycerols. On the other hand carp fed supplementary wheat in ponds resulted in somewhat lower levels of these essential fatty acids. High amounts of n-3 fatty acids can be found in carp fed high-energy diets containing high levels of fish oil. Analogous results were obtained in experiments with tench reared under different nutritional conditions. While rearing on the basis of only natural food in ponds as well as feeding supplementary wheat yielded in similar levels of n-3 and n-6 polyunsaturated fatty acids, higher contents of n-3 fatty acids were recorded in tench fed pellets. High levels of n-3 polyunsaturated fatty acids in foodstuffs have positive effects on human health. Experiments with different cultured fish species proved that the fatty acid composition of the edible parts can be influenced by the diet. Therefore, a finishing diet with a suitable fatty acid profile can be used to improve the nutritional quality of fish products of farmed origin.     

星斑川鲽的营养分析与评价

测定了养殖星斑川鲽肌肉中的蛋白质、脂类和灰分等生化组分,并计算了其比能值,分析了肌肉中构成蛋白质的16种常见氨基酸和主要脂肪酸含量。结果表明,星斑川鲽属高蛋白、低脂肪鱼类;肌肉氨基酸含量同其他鲆鲽鱼类相比,属中上等水平;必需氨基酸和呈味氨基酸的含量较高。肌肉蛋白中氨基酸的支／芳值为2．33。各类脂肪酸中,油酸（18：In）含量最高,其次为亚油酸（18：2n6）和棕榈酸（16：0）。星斑川鲽富含EPA和DHA,营养丰富且平衡良好,是值得推荐的优良养殖品种和优质食用鱼类。     

Partial replacement of fishmeal with sunflower cake and corn oil in diets for tilapia Oreochromis niloticus (Linn): effect on whole body fatty acids

The objective of this study was to determine the effect of replacing fishmeal with high‐fibre and low‐fibre sunflower cakes (HFSC and LFSC) on whole body fatty acid composition in tilapia Oreochromis niloticus (Linn). Sex‐reversed O. niloticus males with an initial weight of approximately 16g ± 0.95 (SD) were used. A control diet based on herring meal and soybean meal was formulated. Six test diets were formulated such that low‐fibre (LF) and high‐fibre (HF) sunflower cakes (SC) contributed 30%, 60% and 80% of the dietary protein, and the diets were designated as LFSC‐30, LFSC‐60, LFSC‐80, HFSC‐30, HFSC‐60, and HFSC‐80 respectively. All fish were held at 25–28°C. They were fed three times daily their prescribed experimental diets for 70 days. At the end of this period they were starved for 24 h and weighed. Five fish representing the average weight of each replicated group (n=3) were frozen in plastic bags at –22°C for determination of fatty acid composition. Fatty acids in the fish were significantly influenced by diet. Palmitic, oleic and linoleic acids were the most abundant fatty acids in both the diets and the fish. Linoleic acid (18:2 ω6) was the most abundant fatty acid in diets based on sunflower cake. The levels of this fatty acid were also higher in fish fed diets with high contents of the sunflower cakes (LFSC‐60, LFSC‐80 and HFSC‐80) (31.3%, 34.7% and 29.7% respectively) than fish fed the control diet (13.8%). Percentages of long chain polyunsaturated acids of the ω‐3 family viz., docosahexaenoic (22:6 ω3) and eicosapentaenoic (20:5 ω3) were low in the diets and in the fish bodies. Fish fed the control diet had a higher level of 22:6 ω3 than those fed the other diets. The possible implications of the preceding findings for human health will be discussed.     

Effects of dietary palm oil source on growth,tissue fatty acid composition and nutrient digestibility of red hybrid tilapia,Oreochromis sp., raised from stocking to marketable size

A 20-week feeding trial was carried out to investigate the influence of three palm oil products as the principal dietary lipid source on the growth performance, proximate composition, tissue fatty acid composition and nutrient digestibility of red hybrid tilapia (Oreochromis sp.) fed these diets from stocking to marketable size. Four isonitrogenous (30% crude protein) and isoenergetic (16.5 kJ g^− 1) practical diets were formulated with 8% of added fish oil (FO), crude palm oil (CPO), palm fatty acid distillate (PFAD) or refined, bleached and deodorized palm olein (RBDPO), respectively. Each diet was fed to triplicate groups of 30 fish of 31.24 ± 0.05 g mean initial body weight. The tilapia were raised at 29 ± 1 °C in 12 round 1000 L fiberglass tanks with a continuous water flow rate of about 1.8 L/min.Results showed that the source of added lipid did not significantly influence (P > 0.05) final body weight, specific growth rate, feed conversion ratio, survival, body indices, hematocrit and production yield of tilapia. There was no significant difference in the fillet proximate composition of fish fed the various diets, except that fish fed the PFAD diet showed lower lipid deposition. The deposition of fatty acids in fish tissues was generally influenced by the fatty acid profile of the diets. Fillet fatty acid profiles of tilapia fed palm oil-based diets had significantly higher concentrations of saturated and monounsaturated fatty acids, but lower levels of polyunsaturated fatty acids (PUFA) compared to the fish fed the FO diet. Fillet of fish fed the FO diet had significantly higher concentrations of EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) compared with fish fed palm oil-based diets. Dietary lipid source did not significantly affect dry matter and protein digestibility (62.1–64.8% and 83.5–85.0%, respectively). The inclusion of dietary palm-origin oils significantly reduced the total lipid digestibility of the diets due mainly to the decreased digestibility of the saturated fatty acids. In all treatments, the apparent digestibilities of both n − 3 and n − 6 PUFA were the highest, followed by monoenes, while the lowest were the saturated fatty acids. Despite the high free fatty acid content of PFAD (92.2%) compared to CPO (4.8%) and RBDPO (0.1%), the different free fatty acid content did not significantly affect the nutrient digestibility of the palm oil-based diets. Results obtained confirmed the feasibility of feeding tilapia with palm oil-based diets with a 100% substitution of added dietary fish oil throughout the grow-out cycle until marketable size.