真鲷仔稚鱼对实验微粒饲料中卵磷脂适宜需要量的研究

制备了4种n-3HUFA含量基本相等、卵磷脂含量分别为0、2．5％、5．0％、7．5％的实验微粒饲料，探讨了卵磷脂的含量对真鲷仔稚鱼生长、存活、体内相关成分以及对外部压力的耐受性的影响。25d的养殖试验结果表明，当真鲷仔稚鱼的实验微粒饲料中卵磷脂含量不超过5．0％时，随着实验微粒饲料中卵磷脂含量的增加，真鲷仔稚鱼的生长速度和成活率也相应增加。养殖试验结束后，对仔稚鱼体内相关成分的分析结果表明，仔稚鱼体内n-3HUFA和DHA的含量随着实验微粒饲料中卵磷脂含量的增加而增加。但当卵磷脂含量从5．0%增加到7．5％时，真鲷仔稚鱼的生长速度、成活率以及体内n-3HUFA和DHA的含量却没有相应增加，因此，真鲷仔稚鱼对实验微粒饲料中卵磷腊的适宜需要量应为5．0％左右。活力测试结果表明，当真鲷仔稚鱼的实验微粒饲料中卵磷脂的含量不超过5．0％时，随着实验微粒饲料中卵磷脂含量的增加，真鲷仔稚鱼对外部压力的耐受性增强，但是当实验微粒饲料中卵磷脂的含量从5．0％增加到7．5％时，真鲷仔稚鱼对外部压力的耐受性并没有继续增强，从而进一步说明真鲷仔稚鱼对实验微粒饲料中卵磷脂的适宜需要量应为5．0％左右。     

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。     

细鳞鲑幼鱼n-3 HUFA需求量的研究

为确定细鳞鲑(Brachymystax lenok)n-3 HUFA需求量以减少鱼油使用和降低养殖成本,研究饲料中不同水平的n-3 HUFA对细鳞鲑的生长性能、体成分和肌肉脂肪酸组成的影响。以脱脂鱼粉、脱脂豆粕、明胶和酪蛋白为主要蛋白源,通过调节饲料中的猪油和浓缩油EPA、DHA水平,使饲料n-3HUFA的含量分别达到0.25%、0.50%、0.75%、1.00%、1.25%、1.50%,配制出6种等氮等能的试验饲料(D 0.25、D 0.50、D 0.75、D1.00、D 1.25和D 1.50),分别投喂细鳞鲑幼鱼(60.0 g±2.8 g)84 d。结果显示:饲料中n-3HUFA不同水平对细鳞鲑成活率和饲料系数没有显著影响,但是显著影响了其末重(FW)、增重率(WGR)和特定生长率(SGR)。随着添加饲料中n-3HUFA水平的升高,FW、WGR和SGR有先升高后下降的趋势,且3者在饲料中n-3HUFA水平为0.75%均最大。随着饲料中n-3 HUFA水平的升高,鱼肌肉18∶1n-9的含量逐渐下降,而22∶6n-3的水平相应升高。结果表明,以WGR为评价指标时,用二次曲线模型推测出细鳞鲑对饲料n-3 HUFA的需求量约为0.69%。     

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(P0.05);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(P0.05)。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。     

饲料蛋白质含量和n-3HUFA水平对大菱鲆亲鱼产卵的影响

给大菱鲆亲鱼投喂高蛋白和高水平 n 3HUFA的饲料。结果表明,与投喂低蛋白和低水平 n 3HUFA饲料组相比,大菱鲆亲鱼繁殖力明显提高。高水平试验组,亲鱼体重增重大,产卵量高、所产卵子卵径大,受精后上浮率、孵化率高,仔稚鱼的存活力强。其中卵子脂肪酸含量受亲鱼所摄饲料中脂肪酸含量的影响较大。当亲鱼组投喂试验组饲料的蛋白质为 49 3%、脂类含量为14 6%,其中∑n 3HUFA的比例为 29 3%时,平均每尾亲鱼的产卵量为 1 45×106,所产卵子的卵径为1 053 mm,卵子脂类∑n 3HUFA的比例为20 38%,浮性卵率为95%。经过30 d的饲育,大菱鲆苗种的存活率为 23%,明显高于低蛋白和低脂肪酸试验组的数据。本研究认为,大菱鲆亲鱼培育的饲料中适宜蛋白质含量应≥45%;脂类的适宜含量为≥10%,其中∑n 3HUFA的适宜比例≥20%。     

仔稚鱼的极性脂——磷脂研究进展

总结了饲料磷脂对仔稚鱼在成活率、生长、抗御外部压力的耐受性以及畸形鱼发生率等方面的重要作用。饲料中缺乏磷脂对仔稚鱼的影响比对幼鱼的影响更明显 ,仔稚鱼饲料中的磷脂含量应高于幼鱼饲料中磷脂的含量。仔稚鱼对饲料磷脂中的磷脂酰胆碱和磷脂酰肌醇的需要量占饲料的 1%～ 3% (干重 )。用磷脂作为必需脂肪酸和能量的来源在仔稚鱼中的消化率高于中性脂的消化率。饲料磷脂可以增强仔稚鱼体内的脂类运输能力     

用裸藻对饵料生物进行营养强化

<正> 1 前言 近20年来,鱼类营养需要的研究得到了飞速的发展,特别是脂肪酸中的高度不饱和脂肪酸(n-3HUFA)的重要性已被普遍认识。仔鱼期不可缺少地投喂饵料生物也说明了n-3HUFA的供给是非常重要的,所以目前所有的种苗生产都用海水小球藻和市售的营养强化饲料对饵料生物进行营养强化。 在天然的n-3HUFA中,二碳五烯酸(EPA)和二十二碳六烯酸(DHA)占大部分。最近在真鲷、大甲鲹、鰤鱼、日本对虾的饲养中比较了上述两种必需脂肪酸的效果。其     

石斑鱼仔稚鱼微粒子配合饲料系列产品研制

根据石斑鱼仔稚鱼的营养需求,精选原料,筛选配方,研制出石斑鱼仔稚鱼微粒子配合饲料,通过测定其散失率和沉降速度,筛选出较适宜的粘合剂配方为褐藻胶1.5%,胶原蛋白3.5%混合使用。分析石斑鱼仔稚鱼微粒子配合饲料的脂肪酸和氨基酸组成,结果表明其n3HUFA组成占19.4%,与小球藻轮虫的20%～28%非常接近;10种必需氨基酸的组成合理。所研发的饲料安全限量符合NY5072《无公害食品渔用配合饲料安全限量》的要求,第20d到第45d,投喂微粒子配合饲料的点带石斑鱼鱼苗成活率3.3%,优于对照组的3.1%。     

不同干燥温度鱼粉对半滑舌鳎稚鱼生长、消化酶及碱性磷酸酶活性的影响

制备基本组成相同、添加100℃常压干燥鱼粉的饲料(1号饲料)与50℃负压干燥鱼粉的饲料(2号饲料)。将两种饲料分别投喂半滑舌鳎(Cynoglossussemilaevis Günther)稚鱼,探讨了饲料中不同干燥温度的鱼粉对半滑舌鳎稚鱼生长、存活率、消化酶及碱性磷酸酶活性的影响。21d的养殖试验结果表明,虽然两种饲料中的鱼粉含量相等(60%),但是用2号饲料投喂的半滑舌鳎稚鱼的特定生长率、体内酸性蛋白酶与碱性磷酸酶活性要优于用1号饲料投喂的半滑舌鳎稚鱼的相应指标(P≤0.001),而存活率、体内淀粉酶与脂肪酶活性相当(P>0.05)。从生长、存活率及酶活性指标看,半滑舌鳎稚鱼对50℃负压干燥鱼粉的消化、吸收要优于对100℃常压干燥鱼粉的消化、吸收。     

几种营养强化材料应用于拟穴青蟹种苗培育的初步研究

进行了以淡水小球藻粉、虾片、营养强化剂单一或组合形式替代微绿球藻作为n-3高度不饱和脂肪酸供应源培育拟穴青蟹蚤状Ⅰ期幼体(Z1)~大眼幼体(M)的试验。结果表明:(1)轮虫营养强化后高度不饱和脂肪酸均有显著提高,微绿球藻组与其他组强化轮虫的n-3HUFA含量无显著差异。(2)卤虫不同营养强化材料组中,50μL营养强化剂组有最高的20∶4n6(ARA)、20∶5n3(EPA)、22∶6n3(DHA)、n-3HUFA含量。(3)营养强化材料直接投入苗池。上午投喂0.5×10-6g/mL组合饵料,下午投喂0.5×10-6g/mL营养强化剂,辅以10×10-6g/(mL.d)EM活菌,试验池的M成活率比对照池投喂微绿球藻增加了10.1%。     

Incorporation of fatty acids from dietary neutral lipid in eye, brain and muscle of postlarval turbot fed diets with different types of phosphatidylcholine

Previous results demonstrated the stimulating effect of soybean phosphatidylcholine (PC) on the utilization of dietary neutral lipid in larval and postlarval fish. The present study further investigated the effect of the degree of saturation of dietary PC on the enhancement of dietary fatty acid incorporation in lipids of turbot. Newly-weaned turbot were fed for 20 days on four isolipidic diets containing the same amount of highly unsaturated fatty acids (HUFA), presented either as neutral lipid, i.e. fish oil ethyl esters, or as polar lipid. Diet FO was a phospholipid-free control diet. Diets HPC, SPC and FPC were supplemented with 3% hydrogenated soybean PC, 3% native soybean PC and 3% marine fish roe PC, respectively.The three PC-supplemented diets resulted in better growth and higher muscle triacylglycerol levels than the PC-free diet FO. The fish fatty acids were determined in 3 lipid classes (neutral lipid, PC, phosphatidylethanolamine) of 3 organs or tissues (eye, brain and muscle). Despite the identical amounts of n-6 and n-3 fatty acids provided by the soybean oil and by the HUFA ethyl esters, the substitution of 3% hydrogenated coconut oil in diet FO by 3% hydrogenated PC in diet HPC caused, averaged over the various tissues and lipid classes, a 7 to 12% higher incorporation of 18:2n-6, 20:4n-6, 20:5n-3 and a 32% higher 22:6n-3 level in turbot lipid. Diet HPC appeared as efficient as diet SPC for enhancing the incorporation of the n-3 HUFA from the ethyl esters. Feeding diet FPC, in which the n-3 HUFA were provided through the marine PC source, resulted in slightly higher levels of these fatty acids in the fish than feeding the ethyl ester HUFA diets, even if supplemented with PC. Present results confirm the positive effect of PC, either hydrogenated or native, on the utilization of fatty acids provided in the diet as neutral lipid. The slightly higher incorporation of HUFA, when esterified on dietary PC instead of neutral lipid, raises the question regarding the form of intestinal absorption of PL in fish.p>     

Importance of Docosahexaenoic Acid in Marine Larval Fish

Marine finfish require n-3 HUFA such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) as essential fatty acids (EFA) for their normal growth. But it remained unclear as to which of the n-3 HUFA, either EPA or DHA, was important. Unlike the freshwater species, the EFA efficiency of EPA and DHA may vary in marine fish. The developing eggs rapidly utilize DHA either for energy or for production of physiologically important substances like prostaglandin.
This report reveals that in marine larval fish DHA is superior to EPA as EFA. In the case of red seabream, feeding rotifers incorporating EPA and DHA or an n-3 HUFA mixture prevented many of the ill-effects observed when the rotifers were low in n-3 HUFA. Apart from the best growth and survival in an activity test for the larvae fed on DHA-rotifer, the incidence of hydrops seemed to be totally prevented dietetically by DHA. Similar results were obtained in larval yellowtail, striped jack, striped knifejaw and flounder. There seems to exist a functional difference between EPA and DHA.     

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.     

Comparison of effects of vegetable oils blended with southern hemisphere fish oil and decontaminated northern hemisphere fish oil on growth performance, composition and gene expression in Atlantic salmon (Salmo salar L.)

Replacement of fish oil with sustainable alternatives, such as vegetable oil, in aquaculture diets has to be achieved without compromising the nutritional quality, in terms of n-3 highly unsaturated fatty acid (HUFA) content, of the product. This may be possible if the level of replacement is not too high and oil blends are chosen carefully but, if high levels of fish oil are substituted, a fish oil finishing diet prior to harvest would be required to restore n-3HUFA. However, a decontaminated fish oil would be required to avoid increasing undesirable contaminants. Here we test the hypotheses that blending of rapeseed and soybean oils with southern hemisphere fish oil will have a low impact upon tissue n-3HUFA levels, and that decontamination of fish oil will have no major effect on the nutritional quality of fish oil as a feed ingredient for Atlantic salmon. Salmon (initial weight ~ 0.8 kg) were fed for 10 weeks with diets in which 60% of fish oil was replaced with blends of soybean, rapeseed and southern hemisphere fish oil (SVO) or 100% decontaminated northern fish oil (DFO) in comparison with a standard northern fish oil diet (FO). Decontamination of the oil was a two-step procedure that included treatment with activated carbon followed by thin film deodorisation. Growth performance and feed efficiency were unaffected by either the SVO or DFO diets despite these having lower gross nutrient and fatty acid digestibilities than the FO diet. There were also no effects on the gross composition of the fish. Liver and, to a lesser extent flesh, lipid levels were lower in fish fed the SVO blends, due to lower proportions of neutral lipids, specifically triacylglycerol. Tissue lipid levels were not affected in fish fed the DFO diet. Reflecting the diet, flesh eicosapentaenoic acid (EPA) and total n-3 fatty acids were higher, and 18:1n-9 lower, in fish fed DFO than FO, whereas there were no differences in liver fatty acid compositions. Flesh EPA levels were only slightly reduced from about 6% to 5% although docosahexaenoic acid (DHA) was reduced more severely from around 13% to about 7% in fish fed the SVO diets. In contrast, the liver fatty acid compositions showed higher levels of n-3 HUFA, with DHA only reduced from 21% to about 18% and EPA increased from under 8% to 9–10% in fish fed the SVO diets. The evidence suggested that increased liver EPA (and arachidonic acid) was not simply retention, but also conversion of dietary 18:3n-3 and 18:2n-6. Increased HUFA synthesis was supported by increased hepatic expression of fatty acyl desaturases in fish fed the SVO diets. Flesh n-3HUFA levels and desaturase expression was significantly higher in fish fed soybean oil than in fish fed rapeseed oil. In conclusion, partial replacement of fish oil with blends of vegetable oils and southern hemisphere fish oil had minimal impact on HUFA levels in liver, but a greater effect on flesh HUFA levels. Despite lower apparent digestibility, decontamination of fish oil did not significantly impact its nutritional quality for salmon.     

Effect of a dietary phospholipid supplementation on growth and fatty acid composition of European sea bass (Dicentrarchus labrax L.) and turbot (Scophthalmus maximus L.) juveniles from weaning onwards

Two 40-day feeding trials using extruded diets were conducted to assess the effect of a dietary phospholipid (PL) supplementation on growth, survival and fatty acid composition of European sea bass (Dicentrarchus labrax) and turbot (Scophthalmus maximus) from weaning onwards. Two dietary treatments (FO and PL) were tested; both had an identical extruded basis (92.5% total diet weight) coated with a different lipid fraction (7.5% total diet weight). Diet PL contained 2% egg yolk PL (69% pure). In diet FO the PL was replaced by hydrogenated coconut oil. The isolipidic diets contained an equal amount of fish oil ethyl esters providing 1.6% (% diet dry weight) of n-3 highly unsaturated fatty acids (HUFA). A diet water stability test showed no effect of the PL supplementation on the leaching of the dietary fatty acids. In both fish species weight, but not survival, significantly increased as a result of PL supplementation. Weaning onto the experimental diets resulted in similar changes in the relative percent levels of fatty acids in both species. In general, the percentage of saturated fatty acids levelled off after a rapid increase, while monoenes increased after an initial decrease. Total n-3 polyunsaturated fatty acids (PUFA) decreased and total n-6 PUFA remained almost constant. The major effect of the dietary PL on fish fatty acid composition was a 50% increase in n-6 and n-3 HUFAs compared to the PL-free FO diet. The rise in n-6 HUFA may have reflected the higher moiety in the dietary PL. On the other hand this was not the case for the n-3 HUFA since they represented only low levels in the PL fraction (0.1%) compared to that provided by the ethyl esters (1.6%) suggesting a more efficient incorporation of the PL n-3 HUFA than of the ethyl ester n-3 HUFA. A second hypothesis is that the dietary PL may have favored the incorporation of the dietary ethyl ester n-3 HUFA.     

Essential fatty acid requirement of juvenile red drum (Sciaenops ocellatus)

Feeding experiments and laboratory analyses were conducted to establish the essential fatty acid (EFA) requirement of red drum (Sciaenops ocellatus). Juvenile red drum were maintained in aquaria containing brackish water (5 ± 2‰ total dissolved solids) for two 6-week experiments. Semipurified diets contained a total of 70% lipid consisting of different combinations of tristearin [predominantly 18:0] and the following fatty acid ethyl esters: oleate, linoleate, linolenate, and a mixture of highly unsaturated fatty acids (HUFA) containing approximately 60% eicosapentaenoate plus docosahexaenoate. EFA-deficient diets (containing only tristearin or oleate) rapidly reduced fish growth and feed efficiency, and increased mortality. Fin erosion and a “shock syndrome” also occurred in association with EFA deficiency. Of the diets containing fatty acid ethyl esters, those with 0.5–1% (n-3) HUFA (0.3–0.6% eicosapentaenoate plus docosahexaenoate) promoted the best growth, survival, and feed efficiency; however, the control diet containing 7% menhaden fish oil provided the best performance. Excess (n-3) HUFA suppressed fish weight gain; suppression became evident at 1.5% (n-3) HUFA, and was pronounced at 2.5%. Fatty acid compositions of whole-body, muscle and liver tissues from red drum fed the various diets generally reflected dietary fatty acids, but modifications of these patterns also were evident. Levels of saturated fatty acids appeared to be regulated independent of diet. In fish fed EFA-deficient diets (containing only tristearin or oleate), monoenes increased and (n-3) HUFA were preferentially conserved in polar lipid fractions. Eicosatrienoic acid [20:3(n-9)] was not elevated in EFA-deficient red drum, apparently due to their limited ability to transform fatty acids. Red drum exhibited some limited ability to elongate and desaturate linoleic acid [18:2(n-6)] and linolenic acid [18:3(n-3)]; however, metabolism of 18:3(n-3) did not generally result in increased tissue levels of (n-3) HUFA. Based on these responses, the red drum required approximately 0.5% (n-3) HUFA in the diet (approximately 7% of dietary lipid) for proper growth and health.     

Fish oil replacement by different microalgal products in microdiets for early weaning of gilthead sea bream (Sparus aurata,L.)

The aim of this study was to determine if algal products rich in DHA or ARA are able to completely replace fish oil in microdiets for marine fish larvae, gilthead seabream and if extra supplementation with EPA may further enhance larval performance. For that purpose, 20 day‐old gilthead seabream larvae of 5.97 ± 0.4 mm mean total length and 0.12 ± 0.001 mg mean dry body weight were fed with five microdiets tested by triplicate: a control diet based on sardine oil; a diet containing AquaGrow^® DHA (diet DHA) to completely substitute the sardine oil; a diet containing AquaGrow^® ARA (diet ARA); a diet containing both products, AquaGrow^® DHA and AquaGrow^® ARA to completely substitute the fish oil; and, a diet containing both products, AquaGrow^® DHA and AquaGrow^® ARA, together with an EPA source. Temperature, air and salinity activity tests were also performed to detect larval resistance to stress. At the end of the experiment, final survivals did not differ among groups. The microorganism produced DHA was able to completely replace fish oil in weaning diets for gilthead seabream without affecting survival, growth or stress resistance, whereas the inclusion of microorganism produced ARA did not improve larval performance. Moreover, addition of EPA to diets with total replacement of fish oil by microorganism produced DHA and ARA, significantly improved growth in terms of body weight and total length. The results of this study denoted the good nutritional value of microorganisms produced DHA as a replacement of fish oil in weaning diets for gilthead seabream, without a complementary addition of ARA. However, dietary supplementation of EPA seems to be necessary to further promote larval performance.     

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.     

活饵料中n-3高度不饱和脂肪酸对黑鲷仔稚鱼生长和存活的影响

采用乳化油直接添加法,用n－3高度不饱和脂肪酸（n－3HUFA）含量不等的4种乳化油分别强化轮虫、卤虫活饵料,培育4组黑鲷仔鱼和稚鱼,各自历时15d,结果表明,n－3HUFA对黑鲷仔鱼和稚鱼的生长和存活均有重要影响。在该条件下,轮虫体内n－3HUFA含量为0．233％（湿重计）,卤虫体内n－3HUFA含量为4．273％（湿重计）时,仔鱼和稚鱼达到最佳生长和成活率。