Regulation of growth, fatty acid composition and delta 6 desaturase expression by dietary lipids in gilthead seabream larvae (Sparus aurata)

The Δ6 and Δ5 desaturases and elongases show only very limited activity in marine fish, and little is known of the possibility of enhancing Δ6 desaturase gene expression in these fish. The use of plant oils in marine fish diets is limited by their lack of n−3 highly unsaturated fatty acids (HUFA) despite an abundant content of the 18C fatty acid precursor linoleic and α-linolenic acids. The objective of the present study was to determine the ability of larval gilthead seabream to utilize vegetable oils and assess the nutritional regulation of Δ6 desaturase gene expression. Seventeen-day-old gilthead seabream larvae were fed during a 17-day period with one of four different microdiets formulated with either sardine fish oil (FO), soybean, rapeseed or linseed oils, respectively, or a fifth diet containing defatted squid meal and linseed oil. Good larval survival and growth, both in terms of total length and body weight, were obtained by feeding the larvae either rapeseed, soybean or linseed oils. The presence of vegetable oils in the diet increased the levels of 20:2n−9 and 20:2n−6, 18:2n−9, 18:3n−6, 20:3n−6 and 20:4n−6, in larvae fed rapeseed and soybean oils in comparison to those fed FO. In addition, a sixfold increase in the relative expression of Δ6 desaturase-like gene was found in larvae fed rapeseed and soybean oils, denoting the nutritional regulation of desaturase activity through its gene expression in this fish species. However, feeding linseed oil did not increase the expression of the Δ6 desaturase gene to such a high extent.     

Effect of dietary kefir on the growth performance,feed utilization and fatty acid profile of juvenile rainbow trout,Oncorhynchus mykiss

A study was conducted to determine the effect of feeding with diets containing kefir on growth performance and fatty acid profile of rainbow trout (Oncorhynchus mykiss). Four isonitrogenous (450 g protein kg^?1) and isocaloric (4325 kcal kg^?1) diets were prepared in trout feed to contain 0 (control), 20, 50 and 100 g kg^?1 kefir. Fish, initial weight of 46 g, were randomly distributed into triplicate 520‐L fibreglass tanks in freshwater flow‐through system. Fish were fed at 4% of the body weight thrice a day for 12 weeks. The results indicated that survival rate ranged from 97.14 to 100% without significant difference among treatments (p > .05). Whole‐body moisture and lipid composition were significantly affected by diets containing different levels of kefir (p < .05), but no differences were determined in protein and ash. Furthermore, the fatty acid profile of flesh showed differences among the groups. The percentages of saturated fatty acid in the flesh lipid decreased, while 18:3n‐3 and polyunsaturated fatty acids were increased at higher substitution levels of kefir grain. The present study showed that up to 100 g kg^?1 supplementation of kefir in diets could be improve the fatty acid profile, especially PUFA, in fish flesh without adverse effect on the growth, feed utilization and survival rate of rainbow trout.     

Effect of dietary n‐3 HUFA on growth performance and tissue fatty acid composition of gibel carp Carassius auratus gibelio

A 12‐week growth trial was conducted with gibel carp Carassius auratus gibelio (initial weight: 2.69 g) to evaluate the effects of dietary n‐3 highly unsaturated fatty acids (n‐3 HUFA) on growth performance and tissue fatty acid composition. Five diets of different n‐3 HUFA levels from 0 to 17 g kg^?1 diet were supplemented at 80 g kg^?1 dietary lipid by including fish oil (FO) at 0, 25, 50, 75 and 100% of supplemental lipid. The remainder was coconut oil. The results showed that fish fed FO₂₅ and FO₅₀ obtained highest specific growth rate and lowest with FO₀. Feed efficiency was highest at FO₁₀₀ and lowest at FO₀. Apparent digestibility coefficient of lipid increased with increasing dietary n‐3 HUFA. The fish fed FO₀ diet had the lowest thiobarbituric acid reactive substance in serum and muscle and highest moisture and lowest lipid content in viscera. Fatty acid compositions of muscle and liver were correlated with dietary fatty acids. Fish muscle concentration of 20:5n‐3 increased with increasing dietary n‐3 HUFA while the concentration of 22:6n‐3 was distinctly reduced in FO₀ group. It suggested that 4 g kg^?1 n‐3 HUFA in diet could permit gibel carp normal growth performance and provide considerable n‐3 HUFA in fish muscle. Excessive n‐3 HUFA showed impact on growth performance of gibel carp.     

Effect of dietary supplementation of phospholipids and highly unsaturated fatty acids on reproductive performance and offspring quality of Chinese mitten crab, Eriocheir sinensis (H. Milne-Edwards), female broodstock

This study was conducted to determine the optimum phospholipids: highly unsaturated fatty acids (PL/HUFA) ratio in maturation diets for female Chinese mitten crab, Eriocheir sinensis broodstock. Five isolipidtic and isonitrogenous diets were formulated to contain different amounts of pork lard, fish oil and soy lecithin with resulting PL/HUFA levels (%dry weight) of 1.4/0.3 (Diet 1), 1.6/2.5 (Diet 2), 2.3/2.0 (Diet 3), 3.8/1.5 (Diet 4) and 5.1/0.8 (Diet 5). Diet 1 lacked supplemental fish oil and soy lecithin and served as the control. Each of the five formulated diets was fed to a total of 150 female crabs for a period of 7 months. All diet treatments were triplicated with 50 crabs stocked in a pond as a replicate. After 6 months, male crabs were introduced into the ponds where females were kept, mating, spawning and egg hatching (in seawater) occurred in the following month. The nutritional value of various formulated diets was assessed based on survival, gonadosomatic index (GSI), egg production per female, fecundity (eggs/g female weight) of the females fed those diets and egg and larval (newly hatched zoea I larvae) quality.Females fed Diet 1 had the lowest GSI, egg production per female and fecundity while no significant difference were found for survival, hepatosomatic index (HSI) and the percentage of female spawned among the diet treatments (P > 0.05). Although there were no significant differences in egg diameter, egg wet or dry weights among all treatments (P > 0.05), the highest and the second highest proportions of essential fatty acids (EFA), i.e. 20:5n-3 (EPA), 22:6n-3 (DHA) and HUFA were found in the eggs produced by the females fed Diet 3 and Diet 2, respectively. Statistical analysis showed that EPA, DHA and HUFA in eggs produced by females fed Diet 3 were significantly higher than those from the other treatments (P < 0.05). Meanwhile, zoea I larvae from crabs fed Diet 3 had significantly larger carapace length than those from the other four treatments (P < 0.05). The zoea I larvae from crabs fed Diet 2 and Diet 3 also showed generally better tolerance to starvation and osmotic shock.In conclusion, our results indicated that diet included levels of PL/HUFA around 1.6/2.5 or 2.3/2.0 (% dry weight) fed female E. sinensis broodstock supported increased fecundity and elevated level of HUFA in egg, which in turn resulted in improved overall quality of newly hatched larvae.     

Effects of varying dietary fatty acid profile on growth performance, fatty acid, body and tissue composition of juvenile pike perch (Sander lucioperca)

Pike perch (Sander lucioperca) has been identified as specie destined to diverse European inland aquaculture, but knowledge on the nutritional requirements is weak. Therefore, we investigated the effect of varying dietary fatty acid (FA) profile by partial replacement of fish oil (FO) with vegetable oils on growth, FA and body composition of juvenile pike perch. An extruded basal diet containing 59 g kg^?1 crude lipids (FO) was added with 60 g kg^?1 FO, 60 g kg^?1 linseed oil (LO) or 60 g kg^?1 soybean oil (SO). The resulting dietary FA composition differed mainly in the triglyceride fraction and was characterized by highest amounts of linolenic acid (18:3 n‐3) in the LO diet and linoleic acid in the SO diet. Diet enriched with FO contained highest contents of highly unsaturated FA 20:5 n‐3 (eicosapentaenic acid) and 22:6 n‐3 (docosahexaenic acid). Pike perch were held in a recirculation system and each feeding group (in triplicate) was fed with experimental diets at a daily rate of 35 g kg^?1 of biomass for 57 days by automatic feeders. Weight gain and specific growth rate of experimental feeding groups ranged between 18.47 and 19.58 g and 1.37–1.45% day^?1 and was not affected by the dietary composition indicating that FO can be replaced by vegetable oils without negative impact on growth performance. In contrast to the whole body and muscle composition, liver tissue was affected by the varying diets. Liver tissues of fish fed diets enriched with vegetable oils showed significantly increased lipid contents of 162 (LO) and 147 (SO) g kg^?1 and indicate decreased lipid utilization compared with fish fed FO diet (liver lipid content 112 g kg^?1). Nevertheless, hepatosomatic index of pike perch was not influenced by dietary lipid composition. The FA profile of pike perch was generally determined by the dietary FAs.     

Dietary nucleotide mixture effects on reproductive and performance,ovary fatty acid profile and biochemical parameters of female Pacific shrimp Litopenaeus vannamei

The effects of different dietary nucleotide mixture (NT) levels (0, 2, 4 and 6 g/kg) were investigated on the reproductive performance, fatty acid profile and biochemical parameters in Litopenaeus vannamei female that were co‐fed with fresh food (two times daily) and experimental diets (two times daily) for 30 days. Sampling was carried out at the first day of the trial, before eyestalk ablation (ESA) (day 21) and after ESA (day 30). Reproductive performance parameters including the hepatopancreatic index, absolute fecundity, egg diameter and latency period were higher in the NT‐supplemented groups than the control group (p < .05). Total n‐3 polyunsaturated fatty acids in the ovaries, especially eicosapentaenoic acid, were higher in the NT‐supplemented groups than in the control (222.6 ± 7.3 versus 204.7 ± 3.0 mg/g extracted lipid) (p < .05). Total hemocyte count, granular cells, plasma glucose (Glu), total protein (TP), calcium (Ca²⁺), total cholesterol (Chol), triglyceride (Tg) and high‐density lipoprotein (HDL) levels were significantly increased in the NT‐supplemented groups in comparison with the control group (p < .05). After ESA, the concentration of plasma Glu, TP, Chol and Tg significantly decreased, but HDL levels increased in all groups (p < .05). These results suggested that the application of dietary NT may present a novel strategy for increasing reproductive performance and health status in L. vannamei.     

Effect of dietary fish and vegetable oil on the growth performance,body composition,fatty acids profile,reproductive performance and larval resistance in pearl gourami (Trichogaster leeri)

This study investigated the effect of two lipid sources on reproduction performance and growth in pearl gourami. For this purpose, 180 fish (3.32 ± 0.25 g) were fed with three isoenergetic (19.80) and isonitrogenous diets (480 g/kg protein) including FO (80 g/kg fish oil), FS (40 g/kg fish oil and 40 g/kg soybean oil) and SO (80 g/kg soybean oil) for 10 weeks before maturation. At the end of the trial, there was no significant difference in weight gain, feed conversation ratio and body composition between fish fed FO and FS diets. Individuals fed dietary FO had significantly higher levels of n‐3 long‐chain polyunsaturated fatty acids in the muscle (130.5 g/kg lipid) and ovary (140.4 g/kg lipid) as compared with those fed SO diet (64.5, 103.6 g/kg, respectively) (p < .05). Feeding pearl gourami with FO and FS diets enhanced regarding absolute fecundity, relative fecundity, the fertilization rate, larvae total length and survival at 3 day posthatch (p < .05). Also, 17 beta‐estradiol in plasma of fish fed dietary FO (6.2 ng/L) was higher than those fed SO diet (1.7 ng/L) (p < .05). In conclusion, we suggest FS diet for broodstock nutrition of pearl gourami as a model for asynchronous multi‐batch spawning fish.     

Effect of dietary lipid levels on growth performance,fatty acid profile and enzymatic activity of juvenile swimming crab,Portunus trituberculatus

The main objective of this investigation was to study the lipid requirements of the early juvenile (C1) swimming crab (Portunus trituberculatus) based on growth performance, survival, moulting and fatty acid profile. Four test diets were formulated with graded lipid levels (3.63%, 6.70%, 10.72% and 13.91%). Each diet was fed to 4 replicates of crabs (30 crabs per replicate initial weight (8.4 ± 0.1 mg). In this study, crabs fed diets with 13.91% lipid had significantly (p < 0.05) higher survival than crabs fed with 3.63% lipid, but no significant (p > 0.05) improvement of survival was observed when dietary lipid increase from 6.70% to 13.91%. Crabs fed diets with 10.72% and 13.91% lipid had significant higher weight gain(WG) than crabs fed with 3.63% lipid. While crabs fed with diets containing 6.70%, 10.72% and 13.91% lipid showed no significant (p > 0.05) difference in weight gain(WG). Moreover, the lowest moulting number was observed in crabs fed diets with 3.63% lipid, but there was no significant difference (p > 0.05) among other groups. The content of LC‐PUFA and DHA in the crabs fed diets with 3.63% lipid was significant (p < 0.05) lower compared to other groups. But there was no significant (p > 0.05) difference in EPA and ARA content among all groups. The activity of lipase increased as dietary lipid level increased (from 6.70% to 10.72%). However, beyond 10.72%, a significant (p < 0.05) decreased in lipase activity was observed. The regression analysis of weight gain data indicated that crab fed diet containing 10.47% lipid level is considered as optimum lipid level for its maximum growth and moulting process.     

The effect of dietary coconut oil on reproductive traits and egg fatty acid composition in rainbow trout (Oncorhynchus mykiss)

Two hundred and twenty rainbow trouts (IBW: 700 g) were randomly allotted to four tanks, with a male/female ratio of 0.56. Fish were fed for 168 d with four experimental diets containing herring oil, cod liver oil and coconut oil with the following inclusion rates: diet A: 12-1-0% respectively; diet B: 6-1-6%; diet C: 0-1-12%; diet D: 0-0-13%. Irrespective of the dietary treatment, weight gains of broodstocks were high (> 3 g/d) and FCR below 2. No significant difference was observed concerning the total amount of eggs spawn, egg average weight (82.5 mg/egg) and lipid content (5.4 mg/egg). However, the fatty acid profile of eggs was significantly affected by the dietary treatments. The content of unsaturated fatty acids, particularly the n-3 fatty acid series (EPA and DHA) significantly decreased with increasing levels of coconut oil in the diet.     

n-3/n-6 HUFA对大菱鲆幼鱼生长性能、全鱼脂肪酸组成和血清生化指标的影响

为探讨饲料中不同n-3/n-6高不饱和脂肪酸(HUFA)对大菱鲆幼鱼生长性能、全鱼脂肪酸组成和血液生化指标的影响,配制了6种不同n-3/n-6 HUFA(D1:29.54,D2:23.04,D3:18.97,D4:9.06,D5:6.86,D6:3.87)的实验饲料。以大菱鲆幼鱼(12.18±0.01)g为研究对象,在循环水养殖系统中开展了为期8周的养殖实验。实验共分6组,每组3个重复,每个重复35尾鱼。结果显示:饲料中n-3/n-6 HUFA对大菱鲆幼鱼的成活率(SR)无显著影响;增重率(WGR)、特定生长率(SGR)和蛋白质效率(PER)呈先上升后下降趋势且D6组的显著低于其他各组,D2组蛋白质效率显著高于其他各组。全鱼粗蛋白和灰分均呈先上升后下降趋势;D6组肌肉粗蛋白和灰分显著低于其他各组。全鱼ARA含量随着n-3/n-6 HUFA的下降呈上升趋势;全鱼中EPA、DHA、n-3/n-6多不饱和脂肪酸(PUFA)和n-3/n-6 HUFA均随着饲料中n-3/n-6 HUFA的下降呈下降趋势。血清中酸性磷酸酶(ACP)和超氧化物歧化酶(SOD)随着n-3/n-6 HUFA的变化呈上升趋势;溶菌酶(LZM)和总抗氧化能力(T-AOC)呈先上升后下降的趋势,溶菌酶在D2组达到最大值,总抗氧化能力在D3组达到最大值。综上所述,饲料中n-3/n-6 HUFA在适宜范围(18.97~23.04)显著提高了实验鱼的生长性能和非特异性免疫力,改变了鱼体组织的常规成分和脂肪酸组成。     

全氟辛烷磺酸类物质对剑尾鱼Cu/Zn-SOD及相关应激基因表达的影响

研究全氟辛烷磺酸类物质(PFOS)暴露对剑尾鱼肝脏Cu/Zn-SOD及相关应激基因表达的影响,探讨筛选导致体内氧化应激反应的敏感生物标志物,并首次克隆和分析剑尾鱼Cu/Zn-SOD的cDNA全序列。实验将剑尾鱼随机分为5组,包括对照组和3.5、7.0、14.0和28.0mg/L等4个PFOS实验暴露组,同时设置平行组。定量测定了24 h、48 h、96 h和14 d肝脏组织中的Cu/Zn-SOD、HSP70-1、HSP70-2和GST mRNA表达水平的变化,成功克隆包含794 bp核苷酸和编码154个氨基酸的剑尾鱼Cu/Zn-SOD的cDNA全序列。通过与其他相关鱼类Cu/Zn-SOD的核苷酸序列和氨基酸序列相似性比较发现,核苷酸和氨基酸序列相似性分别达到77%~83%和79%~88%。高浓度PFOS暴露后,剑尾鱼肝脏中与应激相关的各种基因发生不同程度的变化。通过RT-PCR技术检测Cu/Zn-SOD mRNA表达在剂量效应上不显著,Cu/Zn-SOD mRNA表达和SOD活性之间并没有相关性,推断是其他类型的SOD基因在PFOS暴露下发挥更为重要的作用。随着暴露时间的持续延长,Cu/Zn-SOD基因的转录水平变化趋势与SOD活性变化及HSP70-1 mRNA表达相一致,表明HSP70通过提高剑尾鱼体内SOD水平以保护机体免受氧化损伤。HSP70-2 mRNA水平比HSP70-1 mRNA表达更加敏感。HSP70-2变化趋势与Cu/Zn-SOD mRNA表达相关性不强,其相关机制有待进一步研究。G ST mRNA表达呈不断上升趋势,这与Nrf2信号传导途径有关,也可能是机体在应对PFOS进入鱼体后的一种防御措施。剑尾鱼在体实验表明,PFOS能够诱导肝脏氧化应激反应,GST mRNA和HSP70-2 mRNA表达可以作为PFOS暴露的敏感生物标志物。     

Effect of dietary arachidonic acid levels on growth performance,hepatic fatty acid profile,intermediary metabolism and antioxidant responses for juvenile Synechogobius hasta

An 8‐week feeding experiment was conducted to determine the effect of dietary arachidonic acid (ARA) levels on growth performance, hepatic intermediary metabolism and antioxidant responses for juvenile Synechogobius hasta. Five isonitrogenous and isolipidic diets were formulated with arachidonic oil (containing 400 g ARA kg^?1) at inclusion levels of 0, 2, 4, 8 and 16 g kg^?1 to replace corn oil. Dietary ARA levels were 0.6, 8.6, 16.7, 32.7 and 64.8 g kg^?1 total fatty acids (FAs), respectively. Fish fed the 8.6–32.7 g ARA kg^?1 total FAs showed the highest weight gain, specific growth rate (SGR) and feed intake. By contrast, feed conversion ratio was the lowest for fish fed the 8.6–32.7 g ARA kg^?1 total FAs. Increasing ARA and total n‐6 fatty acid contents and declining linoleic acid content in liver were observed in fish fed the diet containing increasing dietary ARA levels. As a consequence, ∑n‐6/∑n‐3 ratios increased with increasing dietary ARA levels. Dietary ARA levels significantly influenced several enzymatic activities involved in hepatic intermediary metabolism, such as succinate dehydrogenase, lactate dehydrogenase, lipoprotein lipase and hepatic lipase. Superoxide dismutase activity increased with increasing dietary ARA levels. Glutathione peroxidase and catalase activities and malondialdehyde levels in liver tended to increase with increasing dietary ARA levels from 0.6 to 32.7 g ARA kg^?1 total FAs then declined when dietary ARA levels further increased to 64.8 g ARA kg^?1 total FAs. Broken‐line regression analysis of SGR against dietary ARA level indicated that optimal dietary ARA requirement for juvenile S. hasta was 10.74 g kg^?1 total FAs.     

Effects of α-lipoic and ascorbic acid on the muscle and brain fatty acids and antioxidant profile of the South American pacu Piaractus mesopotamicus

The effects of dietary α-lipoic acid (LA) and vitamin C on the fatty acid (FA) composition in the brain and muscle and vitamins E and C levels in the brain were studied in the fish Piaractus mesopotamicus. A two-factorial design, where diets were devoid or supplemented with ascorbate (500 mg AA kg^− 1) and/or lipoic acid (1000 mg kg^− 1), was used. The levels of eicosapentaenoic acid (20:5n − 3, EPA) increased (P < 0.01) in muscle polar lipids (PL) in LA groups (6.93% ± 0.43 vs. 5.83% ± 0.40 and 6.68% ± 0.53 vs. 6.00% ± 0.39), and the same trend was also seen in the brain, however not significant. These changes are suggested to be caused by a change in lipid metabolism rather than being a direct effect of protection by LA against lipid peroxidation. No interaction of vitamin C and LA neither effects of LA on vitamin E (15.1-19.2 mg α-tocopherol g^− 1 tissue) or vitamin C (total AA, 41.7-89.8 μg g^− 1 tissue) in brain was detected.     

n-3/n-6 HUFA对许氏平鲉幼鱼生长、体组成及组织脂肪酸组成的影响

为研究饲料n-3/n-6高不饱和脂肪酸(HUFA)对许氏平鲉幼鱼生长、体组成及组织脂肪酸组成的影响,配制了6种n-3/n-6 HUFA(D1:14.28,D2:9.26,D3:5.66,D4:3.06,D5:2.02,D6:1.50)的等氮等脂的实验饲料。以许氏平鲉幼鱼(36.30±0.03) g为研究对象,在网箱中养殖65 d,分为6实验组,每组设3个重复,每个重复30尾鱼。结果发现:①饲料n-3/n-6 HUFA对许氏平鲉幼鱼的成活率无显著影响。随着n-3/n-6 HUFA降低,幼鱼增重率呈先上升后下降趋势,饲料系数呈相反趋势,D2和D3组的增重率显著高于各组。②全鱼和肌肉粗脂肪含量呈先上升后下降趋势,分别在D2、D3组达到最大值。肝脏粗脂肪含量呈先下降后上升趋势,D2组显著小于其他各组。③各组织C20:4n-6含量随n-3/n-6 HUFA的降低均呈上升趋势,而C20:5n-3、C22:6n-3和n-3/n-6 HUFA整体呈下降趋势。④鱼体脂肪酸组成受饲料影响程度由大到小依次为腹脂、肌肉、全鱼、肝脏,且各组织C20:5n-3与饲料C20:4n-6均呈显著负相关。研究表明,在本实验条件下,饲料中适宜比例(5.66～9.26)的n-3/n-6 HUFA显著提高实验鱼的生长,改变体组成及组织脂肪酸组成,以增重率和饲料系数作评价指标,经一元二次回归分析得许氏平鲉幼鱼饲料中n-3/n-6 HUFA的适宜比例分别是8.93和8.70。     

Effects of dietary canola oil level on growth performance, fatty acid composition and ionoregulatory development of spring chinook salmon parr, Oncorhynchus tshawytscha

This study assessed the potential of refined canola oil (CO) as a source of supplemental dietary lipid for pre-smolt spring chinook salmon (Oncorhynchus tshawytscha) over a period of 30 weeks. Triplicate groups of 320 fry (∼ 0.80 g), reared in flow-through well water (8-11.5 °C), were fed one of four steam-pelleted dry diets with equivalent gross energy (24.3 MJ/kg), protein (∼ 51.3%) and lipid (∼ 21.6%) content on a dry-weight basis. CO furnished either 0%, 33%, 67%, or 100% of the supplemental dietary lipid, with the remainder from a commercial blend of 1:1 anchovy oil and poultry fat (APF). Thus, CO comprised either 0% (dAPF), 25% (CO25), 49% (CO49), or 72% (CO72) of total dietary lipid content. Overall fish growth rate, feed intake, feed efficiency, protein utilization, percent survival, and terminal whole body proximate constituents were unaffected by diet treatment. Dietary lipid compositions reflected the ratios of CO and APF in the supplemental lipid and their respective fatty acid compositions. Whole body fatty acid compositions mirrored those of diet treatments. However, some essential fatty acids, namely, arachidonic acid (20:4n-6; AA), and docosahexaenoic acid (22:6n-3; DHA) were conserved in fish regardless of dietary CO level. Direct relationships were found between dietary and whole body concentrations of: 18:2n-6 (R² = 0.94; slope = 0.72), 18:3n-3 (R² = 0.99; slope = 0.58), 20:4n-6 (R² = 0.84; slope = 0.42), 20:5n-3 (R² = 0.99; slope = 0.43) and 22:6n-3 (R² = 0.82; slope = 1.25). High dietary levels of 18:3n-3, 18:2n-6, and 20:5n-3 may have been utilized for energy or converted to more unsaturated derivatives. Overall development of ionoregulatory ability, as assessed by 24-h seawater challenge tests, was unaffected by diet. However, whole body chloride content was generally inversely related to dietary CO level during early development. Our findings suggest that there is excellent potential for long-term replacement of fish oil with canola oil in the diet of pre-smolt spring chinook salmon, provided that some marine oil is present to ensure that the essential fatty acid needs of the fish are met.     

Dietary fatty acid profiling in plant protein‐rich diets affects the reproductive performance,egg fatty acid profile and haematological parameters in female rainbow trout (Oncorhynchus mykiss)

The influence of dietary fish oil (FO) substitution with blends of vegetal oils (VO: canola, linseed, olive, sunflower, corn and coconut oils) in plant protein‐rich diets on reproductive performance and fatty acid dynamics of embryos was evaluated in female rainbow trout (Oncorhynchus mykiss) brooders (1.8 ± 0.1 kg). Four diets were formulated in which 20% (FO₈₀/VO₂₀), 50% (FO₅₀/VO₅₀), 75% (FO₂₅/VO₇₅) and 100% (VO₁₀₀) of FO were replaced by mixture of VO. The above‐mentioned diets were administered for a short period prior to spawning (3 months). Fish fed the VO₁₀₀ had the lowest fertilization rate (81.3 ± 2.3), whereas brooders fed the FO₈₀/VO₂₀ diet had the lowest survival rates at eyed embryo stage (83.7 ± 1.6%) and hatching rate (79.9 ± 3.1%). The fatty acid dynamics of embryos were not only affected by embryonic developmental stages, but also they were influenced by the dietary fatty acid profile. Our study confirmed that using blends of different VO sources and FM residual fat in the FO₂₅/VO₇₅ for the short‐term period prior to spawning seemed to be a good strategy in terms of successful reproduction for sparing high levels of FM and FO in diet of O. mykiss brooders.     

Artemia enriched with high n-3 HUFA may give a large improvement in performance of Atlantic halibut (Hippoglossus hippoglossus L.) larvae

Atlantic halibut larvae were fed Artemia enriched with two different oil emulsions (cod liver oil and 2050TG) from first feeding to 70 days after first-feeding (dpff). Larvae fed 2050TG enriched Artemia had better growth, survival and eye migration than larvae fed the cod liver oil enriched Artemia, while pigmentation rate was similar in the two groups. In addition to the difference in fatty acids, the two emulsions differed in lipid class composition, since 2050TG is a synthetic oil and a mixture of mono-, di- and tri-acylglycerol, while cod liver oil is a tri-acylglycerol. Total lipid level, estimated as fatty acid methyl esters (FAME) was similar in the two Artemia types, but sum of n-6 and n-3 fatty acids, arachidonic acid (20:4n-6, ARA), docosahexaenoic acid (22:6n-3, DHA) and eicosapentaenoic acid (20:5n-3, EPA) were higher in Artemia enriched with 2050TG than in the cod liver oil enriched Artemia. However, the main difference in fatty acid composition in the larvae, was a higher DHA (% of total fatty acids) in 2050TG larvae than in cod liver oil larvae. The lipid level measured as FAME was up to four times higher in the 2050TG larvae than in the cod liver oil larvae, and the reason for this may have been a better bioavailability of the partly digested lipid in the 2050TG emulsion. The correlation between a high level of lipid in the larval tissues (e.g. high energy status) and improved eye migration in larvae fed the 2050TG enriched Artemia supports the hypothesis that energy limitation on the larval stage may be a cause of the impaired eye migration commonly observed in farmed Atlantic halibut juveniles.     

Effects of dietary docosahexaenoic acid on growth performance,fatty acid profile and lipogenesis of blunt snout bream (Megalobrama amblycephala)

Six diets were designed to investigate the effects of dietary docosahexaenoic acid (22:6n‐3; DHA) levels (0.5, 1.3, 2.3, 4.2, 8.1 and 15.9 g/kg diets) on growth performance, fatty acid profile and expression of some lipogenesis‐related genes of blunt snout bream (Megalobrama amblycephala). Fish (average weight: 26.40 ± 0.11 g) were randomly fed one of six diets for 8 weeks. Results indicated that the final body weight (FBW) and specific growth rate (SGR) of fish fed 1.3 g/kg DHA were significantly higher than other groups except for the 2.3 g/kg DHA (p < .05). Compared with other groups, the number of lipid droplet clusters of the liver stained with oil red O in the 2.3 g/kg DHA group was the highest, which was consistent with the lipid contents of whole body and liver. The DHA proportion in liver and muscle significantly increased with the increasing dietary DHA levels (p < .05), which reflected fatty acid profiles of diets. The highest mRNA expressions of acetyl‐CoA carboxylase α (ACCα), fatty acid synthase (FAS) and sterol regulatory element‐binding protein‐1 (SREBP‐1) occurred in the 1.3 g/kg DHA group, followed by 2.3 g/kg DHA. In summary, the supplementation of 1.3–2.3 g/kg DHA could improve growth performance and lipogenesis, and the dietary DHA could improve DHA and PUFA proportion in liver and muscle.     

配合饲料替代杂鱼对中华绒螯蟹生长发育、体成分及脂肪酸组成的影响

通过分别投喂配合饲料和天然杂鱼,研究配合饲料替代杂鱼对中华绒螯蟹生长发育、体成分及脂肪酸组成的影响。试验池塘设在上海市崇明县水产技术推广站特色水产养殖基地,每种饵料设3个平行。试验时间为2010年4月至11月,养殖结束后统计各试验组的存活率、体质量、产量,并随机取样测定各试验组雌雄蟹的肝胰腺指数、性腺指数、出肉率,同时测定肝胰腺、性腺和肌肉中水分、总脂、粗蛋白含量及脂肪酸组成。结果显示,杂鱼组和配合饲料组蟹的存活率、体质量、肝胰腺指数、性腺指数、出肉率等指标均无显著差异(P>0.05);杂鱼组雌雄蟹肝胰腺及雄蟹肌肉中水分含量极显著高于配合饲料组(P<0.01);杂鱼组雌雄蟹肝胰腺、性腺及雌蟹肌肉中总脂含量均显著低于配合饲料组(P<0.05);杂鱼组雌雄蟹肝胰腺中粗蛋白含量均显著高于配合饲料组(P<0.05),但杂鱼组雌蟹卵巢中粗蛋白含量极显著低于配合饲料组(P<0.01)。配合饲料组雌蟹肝胰腺游离脂肪酸含量显著高于杂鱼组(P<0.05),磷脂含量杂鱼组显著高于配合饲料组(P<0.05);配合饲料组雌蟹卵巢和肌肉甘油三酯含量均显著高于杂鱼组(P<0.05或P<0.01),游离脂肪酸和磷脂含量则杂鱼组显著高于配合饲料组(P<0.05或P<0.01);雌蟹肌肉中胆固醇含量配合饲料组极显著高于杂鱼组(P<0.01)。两组饵料雄蟹肝胰腺各脂类组成无显著差异;精巢中甘油三酯及游离脂肪酸含量为杂鱼组显著高于配合饲料组(P<0.01),磷脂含量为杂鱼组显著低于配合饲料组(P<0.05);雄蟹肌肉胆固醇含量配合饲料组显著低于杂鱼组(P<0.05)。杂鱼组雄蟹肝胰腺和肌肉中LOA含量极显著或显著低于配合饲料组(P<0.01或P<0.05),而杂鱼组雄蟹肌肉中ARA含量显著高于配合饲料组(P<0.05);杂鱼组雌蟹卵巢中LNA、ARA和DHA的含量极显著或显著低于配合饲料组(P<0.01或P<0.05)。研究结果表明,适宜的配合饲料替代杂鱼全程养殖中华绒螯蟹成蟹对其生长发育无显著负面影响,而对其体成分组成及脂肪酸组成有一定影响。