Improvement of larval rearing technique for mass seed production of snow crab <Emphasis Type="Italic">Chionoecetes opilio</Emphasis>

Larval rearing experiments were conducted to examine the potential for mass seed production of the snow crab Chionoecetes opilio using a total of eight 20-kL tanks. Tanks were equipped with agitators, which move the water using a rectangular blade to prevent the zoeas sinking to the bottom of the tank. Larval rearing water was treated with sodium nifurstyrenate once a week to reduce the chance of larval infection by pathogenic bacteria. Zo eas were fed with rotifers and Artemia nauplii. A total of 122 830 megalops and 16 660 first-stage crabs were produced. Thus, the potential for mass seed production of snow crab was determined. Survival rates up to the megalopal stage were high in tanks with a feeding regime that fed rotifers to larvae through an entire zoeal stage. This study also describes the fatty acid composition of snow crab larvae. It revealed that the first zoeas had a high DHA content and DHA/EPA ratio, but these values significantly decreased in the second stage zoeas and megalops. Improving the DHA content and/or DHA/EPA ratio of larvae should be important in studies on mass seed production technology of the snow crab.     

Replacement of a large portion of fish oil by vegetable oils does not affect lipogenesis, lipid transport and tissue lipid uptake in European seabass (Dicentrarchus labrax L.)

In order to investigate the impact of dietary lipid sources on mechanisms involved in lipid deposition, three groups of European seabass fingerlings with average initial body weight of 5.2 ± 1.0 g were fed three diets differing only by lipid source. These diets were: 100% anchovy oil (diet A), 40% anchovy oil-60% mix of vegetable oils (35% linseed, 15% palm, 10% rapeseed) (diet B) and 40% anchovy oil-60% mix of vegetable oils (24% linseed, 12% palm, 24% rapeseed) (diet C). After 64 weeks of rearing, when seabass reached the size of 160 g, the activity of lipogenic enzymes (fatty acid synthetase, glucose-6-phosphate dehydrogenase and malic enzyme) in liver and of lipoprotein lipase (LPL) in perivisceral adipose tissue, liver and white muscle were measured. Transport of lipid by lipoproteins was examined by determining plasma lipid composition and lipoprotein classes. Dietary oil source did not modify growth performance or lipid content of flesh and liver of seabass. Replacement of 60% of fish oil by the two mixtures of vegetable oils had no significant effect on hepatic lipogenesis and activity of LPL in liver and adipose tissue. Activity of LPL in white muscle was decreased in fish fed diet C compared to those fed diets A and B. Diets containing the mixture of vegetable oils led to lowered plasma, VLDL and LDL cholesterol levels compared to diet A.It is concluded that replacing 60% of fish oil by the two mixtures of vegetable oils in the feeds of European seabass fingerlings until they reach the size of 160 g has no marked effect on growth performance, lipogenesis and tissue lipid uptake but has a hypocholesterolemic effect.     

n_3多价不饱和脂肪酸营养强化轮虫技术研究

通过甲酯型，乙酯型，脂肪酸型和甘油酯型化学型式ｎ－３多价不饱和脂肪酸的营养强化饵料对轮虫的营养强化试验，观察了营养强化过程中轮虫生理生态变化，测定了轮虫体内ＥＰＡ，ＤＨＡ的含量。结果表明：不论是哪种化学型式的营养强化饵料，营养强强效果均好于微绿球藻强经对照组，轮虫中ＥＰＡ，ＤＨＡ含量明显提高，并在强化１２ｈ达到最高峰。     

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.     

Preparation of Triacylglycerols Enriched in DHA from Single Cell Glycerides via Molecular Distillation and Enzymatic Glycerolysis

In the present study, the total lipids from Schizochytrium sp. were ethylated, and ethyl esters (EE) enriched in docosahexaenoic acid (DHA; C22:6n-3) were obtained through molecular distillation and converted to glyceride form via lipase-catalyzed glycerolysis under vacuum with activated clay as absorbents in a nonsolvent system. Total lipids were extracted from dry powder of Schizochytrium sp., which was followed by lipase catalyzed ethylation. EE with 83.04% DHA was obtained through a three-stage procedure of molecular distillation. The effect of vacuum, temperature, reaction time, substrate ratio, and enzyme dosage on glycerolysis was investigated. Vacuum and increase in temperature had a positive effect on glycerolysis, and the increase in substrate ratio led to an increase in triacylglycerol (TAG) content but a decrease in EE conversion. The adsorption of glycerol onto activated clay played a positive role in glycerolysis, and the operational stability of immobilized lipase. The conditions which gave the glycerides with more than 75% TAG were 60°C, 24 h, 0.048 mol EE, 0.016 mol glycerol, 2.25 g activated clay, and 3% Lipozyme 435, and the immobilized lipase showed good operational stability in 10 batches of reactions with activated clay as absorbent.     

Effect of algal addition on stability of fatty acids and some water‐soluble vitamins in juvenile Artemia franciscana

A minor stabilization effect was found for the content of total lipids, total fatty acids and docosahexaenoic acid (DHA) when Artemia franciscana was maintained at high concentrations of Isochrysis galbana for 72 h at 12 °C, both in 3‐ and 4‐day‐old individuals. The eicosapentaenoic (EPA) level was only stabilized at higher algal concentrations in the 4‐day‐old A. franciscana. In the 3‐day‐old A. franciscana, the EPA content increased at all algal concentrations during the first 24 h of post enrichment, presumably as an effect of DHA catabolism. Apparently, the 4‐day‐old A. franciscana metabolized DHA, and other lipids, faster than the 3‐day‐old A. franciscana did. During the 72 h incubation with I. galbana, the content of ascorbic acid (AA) in A. franciscana increased approximately to 1000–1200 μg g^–1 dry weight (DW) at algal concentrations above 3 mg C L^–1, close to AA content of the algae. The vitamin B₆ content in A. franciscana decreased from approximately 20 to 4–11 μg g^–1 DW, with highest loss rates at the higher algal concentrations. The thiamin content of A. franciscana was independent of algal concentration and remained at 20–30 μg g^–1 DW. The nutritional effects of the algal incubation on the 3‐ and 4‐day‐old A. franciscana at algal concentrations which can be used during the cultivation of Atlantic‐halibut larvae (<2 mg C L^–1) was insignificant, except for the small enrichment effect of AA already at 1 mg C L^–1. Other beneficial effects of the algae should not be ruled out, like possible effects on the microflora of A. franciscana even at algal concentrations less than 2 mg C L^–1.     

Experimental larval culture of the Caribbean scallops Argopecten nucleus and Nodipecten nodosus

Several experiments were performed examining the effect of different culture variables on the growth and survival of Argopecten nucleus and Nodipecten nodosus larvae. Higher growth and survival values were obtained at a low density (1 larvae mL^?1) than at a high density (5 larvae mL^?1), except for N. nodosus's survival, which was not affected by density. Higher growth was obtained when feeding the larvae a diet of Isochrysis galbana, similar results occurred with the diet of Isochrysis galbana+Chaetoceros calcitrans in A. nucleus and with I. galbana combined with the lipid emulsion EmDHA in N. nodosus. Higher survival was obtained when the diet included a mixture of microalgae than when EmDHA was supplemented. Growth and survival of the larvae of A. nucleus were greater when fed continuously, while N. nodosus grew and survived better when food was given discontinuously. Higher growth and survival values were recorded at lower food concentrations ranging from 20 to 40 cells μL^?1 of I. galbana. Higher growth was observed with increasing temperature between 22 and 28 °C, although there was a simultaneous decrease in survival. No significant effects on larval production parameters were found when the culture water was changed totally or partially, but higher larval growth of N. nodosus was verified when a partial renewal of water was performed.     

亚麻籽和鱼油对蛋鸡蛋黄n-3多不饱和脂肪酸含量与肝脏脂肪酸代谢的影响

本试验旨在研究饲粮中添加亚麻籽和鱼油对蛋鸡蛋黄n-3多不饱和脂肪酸含量、肝脏脂肪酸组成及其合成代谢基因表达的影响。选择28周龄海兰褐壳蛋鸡96只,随机分为4组,每组24只。对照组饲喂基础饲粮,试验组分别在基础饲粮中添加10%亚麻籽、10%亚麻籽+5%鱼油和5%鱼油。饲养21 d后连续收集7 d鸡蛋,然后每组随机选取4只鸡屠宰取样。结果表明,与对照组相比:1)添加亚麻籽和鱼油均显著增加蛋黄中n-3多不饱和脂肪酸含量(P0.05),其中单独添加鱼油的蛋黄中二十二碳六烯酸(DHA)和二十碳五烯酸含量最高;2)试验组肝脏单不饱和脂肪酸比例均显著降低(P0.05),肝脏n-3多不饱和脂肪酸比例均显著增加(P0.05);3)单独添加鱼油显著降低肝脏脂肪酸延长酶1、脂肪酸延长酶2和去饱和酶(脂肪酸去饱和酶1、脂肪酸去饱和酶2和硬脂酰辅酶A去饱和酶1)基因表达水平(P0.05)。由此可见,蛋鸡饲粮中单独添加亚麻籽或鱼油可以富集蛋黄n-3多不饱和脂肪酸沉积;添加亚麻籽促进肝脏α-亚麻酸转化生成DHA过程,表现为上调脂肪酸延长酶和去饱和酶基因表达,添加鱼油显示相反结果。     

半滑舌鳎不同家系肌肉中脂肪酸含量的分析

为了研究半滑舌鳎(Cynoglossus semilaevis)不同家系肌肉中脂肪酸的组成与含量,并选育出高营养品系的半滑舌鳎家系,用气相色谱法对同一养殖环境中的半滑舌鳎15个不同家系(164个样本)肌肉中的脂肪酸的组成和含量进行了检测和比较分析,同时对高EPA、DHA、EPA+DHA含量的家系进行筛选,并研究了半滑舌鳎性别与EPA、DHA含量的关系。结果表明:(1)15个家系肌肉中脂肪酸种类没有区别,但脂肪酸的组成和含量存在若干差异。其特征均为多不饱和脂肪酸(PUFA)饱和脂肪酸(SFA)单不饱和脂肪酸(MUFA)。PUFA以ω-3系脂肪酸为主,且ω-3系脂肪酸与ω-6系脂肪酸比值达到4.16~5.03,其中的2种重要ω-3系脂肪酸EPA和DHA在15个家系中均具有显著性差异,且DHA含量远大于EPA含量;筛选出了3个高EPA、DHA、EPA+DHA含量家系,分别为F13012、F13023及F13031。(2)EPA的含量与半滑舌鳎性别不具有显著性相关关系。本研究对于选育半滑舌鳎优良品种家系具有重要意义。     

EPA与DHA最新研究进展

二十碳五烯酸(eicosapentaenioc acid,EPA)与二十二碳六烯酸(decosahexaenoic acid,DHA)是具有许多重要生理功能的ω-3系列多不饱和脂肪酸,二者对人体及动物具有重要作用,吸引越来越多研究者的关注。对EPA和DHA的基本性质、生理功能、来源、提取分离方法及应用现状进行综述,并对其研究前景进行展望。