养殖和野生亚东鲑机体成分比较分析

亚东鲑(Salmo trutta fario)是鲑属鱼类在青藏高原仅有的鱼类种群,是亚东地区全国农产品地理标志产品。本研究对西藏亚东地区野生和养殖亚东鲑的常规营养成分及各组织氨基酸和脂肪酸组成进行分析,旨在比较野生和养殖亚东鲑营养成分的异同,为养殖亚东鲑的品质评价和饲料配方的完善提供参考信息。实验采集亚东河中野生亚东鲑和亚东渔业产业园中使用配合饲料养殖的亚东鲑各10尾用于相关成分分析,每尾为一个独立样本。结果显示,野生组肥满度显著低于养殖组,而全鱼水分和灰分显著高于养殖组。全鱼粗蛋白、粗脂肪以及肝脏常规成分在野生组和养殖组间无显著差异。野生组肌肉粗脂肪显著低于养殖组,而水分含量显著高于养殖组。野生组全鱼必需氨基酸总量显著高于养殖组,且野生组肌肉中苏氨酸、缬氨酸、苯丙氨酸、赖氨酸和甘氨酸含量显著高于养殖组。野生组全鱼、肌肉和肝脏中饱和脂肪酸、n-3多不饱和脂肪酸(n-3 PUFA)总量、EPA、C20:4n-6以及肌肉中DHA含量高于养殖组,而全鱼和组织中单不饱和脂肪酸和n-6 PUFA总量低于养殖组。综上所述,目前养殖亚东鲑和野生亚东鲑在机体成分上存在较大差异。由于养殖鱼类体成分很大程度上反映了饲料组成,因此,亚东鲑养殖中饲料营养组成可能有待进一步优化。     

Early ontogeny-related changes of the fatty acid composition in the Percichthyid fishes trout cod,Maccullochella macquariensis and Murray cod,M. peelii peelii

Changes in the fatty acid profiles of the Percichthyid fish trout cod, Maccullochella macquariensis (Cuvier), and Murray cod, M. peelii peelii (Mitchell), two Australian native freshwater fish species, were investigated during early development from egg to yolk-sac-resorbed larval stage. In the two Percichthyid fishes polyunsaturated fatty acids (PUFA) accounted for more than 50 % of the 19 quantified fatty acids in total lipid. The fatty acids that occurred in the highest abundance in both trout cod and Murray cod, in all developmental stages, in order, were docosahexaenoic acid [DHA 22:6(n-3)], arachidonic acid [AA 20:4(n-6)], oleic acid [18:1(n-9)] and palmitic acid (16:0), all of which exceeded 100 μg per mg total lipid in most instances. The ratio of 22:6(n-3) to eicosapentaenoic acid- 20:5(n-3) in eggs of trout cod and Murray cod was 5.4:1 and 7.3:1, respectively, and remained almost unchanged through development, and was considerably higher than the 2:1 ratio generally reported for fish eggs. In trout cod, 11 of the 19 fatty acids in total lipid decreased during the transformation from egg to yolk-sac-resorbed larva. In Murray cod, only 16:1(n-7) showed a significant decrease whilst 20:4(n-6) increased significantly with development. Overall, there was a tendency in both species to conserve n-3 and n-6 series highly unsaturated fatty acids (HUFA), suggesting their essentiality in first feeding larvae. These observations are discussed in relation to the feeding habits of trout cod and Murray cod, which are top order, freshwater carnivores.     

Egg quality determinants in cod (Gadus morhua L.): egg performance and lipids in eggs from farmed and wild broodstock

Lipids and essential fatty acids, particularly the highly unsaturated fatty acids, 20:5n‐3 (eicosapentaenoic acid; EPA), 22:6n‐3 (docosahexaenoic acid; DHA) and 20:4n‐6 (arachidonic acid, AA) have been shown to be crucial determinants of marine fish reproduction directly affecting fecundity, egg quality, hatching success, larval malformation and pigmentation. In Atlantic cod (Gadus morhua L.) culture, eggs from farmed broodstock can have much lower fertilization and hatching rates than eggs from wild broodstock. The present study aimed to test the hypothesis that potential quality and performance differences between eggs from different cod broodstock would be reflected in differences in lipid and fatty acid composition. Thus eggs were obtained from three broodstock, farmed, wild/fed and wild/unfed, and lipid content, lipid class composition, fatty acid composition and pigment content were determined and related to performance parameters including fertilization rate, symmetry of cell division and survival to hatching. Eggs from farmed broodstock showed significantly lower fertilization rates, cell symmetry and survival to hatching rates than eggs from wild broodstock. There were no differences in total lipid content or the proportions of the major lipid classes between eggs from the different broodstock. However, eggs from farmed broodstock were characterized by having significantly lower levels of some quantitatively minor phospholipid classes, particularly phosphatidylinositol. There were no differences between eggs from farmed and wild broodstock in the proportions of saturated, monounsaturated and total polyunsaturated fatty acids. The DHA content was also similar. However, eggs from farmed broodstock had significantly lower levels of AA, and consequently significantly higher EPA/AA ratios than eggs from wild broodstock. Total pigment and astaxanthin levels were significantly higher in eggs from wild broodstock. Therefore, the levels of AA and phosphatidylinositol, the predominant AA‐containing lipid class, and egg pigment content were positively related to egg quality or performance parameters such as fertilization and hatching success rates, and cell symmetry.     

黄颡鱼早期发育阶段受精卵和鱼体脂肪酸组成变化

研究了黄颡鱼受精卵孵化期间和仔鱼发育阶段脂肪含量和脂肪酸的组成变化规律.采用常规化学分析方法和气相色谱法对黄颡鱼从鱼卵受精开始至仔鱼孵化后未投饵的7 d内的脂肪含量和脂肪酸组成进行测定.结果表明,受精卵在整个孵化期间脂肪含量有下降趋势.受精卵中不饱和脂肪酸含量大于饱和脂肪酸含量.受精卵在整个孵化期间各种脂肪酸含量无明显变化.仔鱼孵化后,鱼体总脂肪含量急剧下降,总脂含量从0日龄的4.57%降低到7日龄的0.75%.仔鱼在饥饿期间鱼体脂肪酸组成发生明显变化,单不饱和脂肪酸含量下降最为明显,尤其是C18:1.仔鱼在饥饿期间,脂肪酸按n-9>n-6>n-3顺序被先后利用,黄颡鱼仔鱼发育阶段主要以单不饱和脂肪酸作为能量代谢基质,而C20:4n6(AA)和C22:6n3(DHA)优先于C20:5n3(EPA)被保存下来.     

Metabolism of 18:4n-3 (stearidonic acid) and 20:4n-3 in salmonid cells in culture and inhibition of the production of prostaglandin F2α (PGF2α) from 20:4n-6 (arachidonic acid)

Arachidonic acid (AA; 20:4n-6) is the precursor of a range of highly biologically active derivatives, collectively termed eicosanoids, including prostaglandins, thromboxanes, leukotrienes and lipoxins, that act as autocrine hormones regulating many physiological processes including haemostasis, reproduction, immune and inflammatory responses. Eicosapentaenoic (EPA; 20:5n-3) and dihomo-γ-linolenic (20:3n-6) acids modulate eicosanoid metabolism by both inhibiting the conversion of AA to eicosanoids whilst simultaneously being converted to eicosanoids with different, often attenuated, properties compared to their AA homologues. Eicosatetraenoic acid (20:4n-3) is a naturally occurring C₂₀ polyunsaturated fatty acid (PUFA), present in fish oil at levels of around 1–2%, that has been suggested to be the active metabolite responsible for the anti-inflammatory effects of plant oils containing stearidonic acid (18:4n-3). However, the biochemical properties of 20:4n-3 in terms of cellular biology have rarely been investigated, partly due to difficulties in obtaining the fatty acid in high purity. In this paper, we describe methods for the medium scale laboratory preparation of high purity 20:4n-3, and investigate its metabolism in fish cell culture systems which normally contain significant amounts of n-3 PUFA. Thus the incorporation and metabolism of 18:4n-3 and 20:4n-3, and their distribution in phospholipid classes was studied in an established cell line from Atlantic salmon (Salmo salar) (AS), and the effects of 20:4n-3 on eicosanoid production studied in freshly isolated macrophages from rainbow trout (Oncorhynchus mykiss). Both 18:4n-3 and 20:4n-3 were preferentially esterified into phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine in contrast with the accumulation of AA in phosphatidylinositol. Incorporated 18:4n-3 was readily converted to 20:4n-3, and both fatty acids were further desaturated and elongated to EPA and 22:5n-3 but not 22:6n-3. Supplementation with 20:4n-3 decreased the conversion of AA into prostaglandins, as demonstrated by the decreased levels of PGF_2α produced in trout macrophages supplemented with 20:4n-3 and AA compared to cells supplemented with AA alone. In addition, 20:4n-3 was converted into eicosanoids in fish cells as indicated by the presence of Δ^17,18 12-HETE, Δ^17,18 PGE1 and Δ^17,18 PGF_1α in extracts from rainbow trout macrophages incubated with 20:4n-3.     

Lipid classes and fatty acids during embryogenesis of captive and wild silverside (<Emphasis Type="Italic">Chirostoma estor estor</Emphasis>) from Pátzcuaro Lake

Lipid classes and fatty acid levels were analyzed in freshly fertilized eggs, early and late embryo development, and freshly hatched larvae obtained from wild and captive silverside Chirostoma estor estor broodstock, as well as in plankton, Artemia, and pelleted feed. The concentration of triglycerides (TGs) and highly unsaturated fatty acids (HUFAs) in neutral lipid fraction significantly decreased during early development and especially after hatching, whereas phospholipids and HUFA in polar lipid fraction remained constant. These results indicate that TGs rather than PLs are used as energy sources and that all HUFAs [20:4n-6/arachidonic acid (ARA), 20:5n-3/eicosapentaenoic acid (EPA), and 22:6n-3/docosahexaenoic acid (DHA)] of polar lipids are selectively conserved during early development. High levels of DHA (30%, on average, of total fatty acids) and low levels of EPA (4%) were observed in eggs, embryos, and larvae and did not reflect the proportions of these fatty acids in food. Preferential accumulation of DHA from food consumed by broodstock, and then transference to eggs, was probably occurring. The main difference between eggs from both origins was a low level of ARA in eggs from captive fish (4% of total fatty acids) compared to wild fish (9%). This could be associated with a deficiency in the diet that is not compensated for by desaturation/elongation of 18:2n-6 and, possibly, with greater stress in captive fish. In any case, particular requirements of ARA should be determined to optimize the culture of C. estor.     

Quantification of the Differences in Flesh Fatty Acid Components between Farmed and Wild Fish

Inconclusive results on the effect of farming on fatty acid composition of fish prevent the application of this possible variable in studies related to human health and environmental policies. The current meta-analysis used results from 39 studies to produce compelling quantitative results on differences in fatty acid components related to human health between farmed and wild fish. With seawater fish, mean effect sizes (Hedges' d) for differences in contents of EPA + DHA, total n-3 fatty acids, and the n-3:n-6 ratio were virtually zero. However, farmed freshwater fish showed a lower total n-3 fatty acid content than their wild counterparts.     

Effects of temperature and feed composition on essential fatty acid (n-3 and n-6) retention in Atlantic salmon (Salmo salar L.) parr

Retentions of total n-3 and n-6 essential fatty acids (EFAs) were assessed in Atlantic salmon (Salmo salar L.) parr held at 8 °C and 2 °C until they increased in weight from ca. 19 g to 38 g. Feeds contained sandeel oil or a rapeseed:linseed oil blend at 21 and 34% dietary fat. EFA retention efficiencies [(g EFA gained g EFA ingested-1) × 100] were estimated by the 'mass balance method' from measurements of feed intake, changes in biomass for each tank of fish, and fatty acid compositions of the feeds and fish. The n-3 EFA retentions were higher (overall mean 71%) across feed treatments and temperatures than the n-6 EFA retentions (overall mean 63%). Retentions of the n-3 fatty acids were higher in the fish given the feeds with the lower fat content (77% vs. 65%), implying improved retention with reduced n-3 EFA availability. n-3 EFA retention tended to be higher at 2 °C than at 8 °C, although this was not consistent across feeds. At low temperature there was very high retention of the n-3 EFAs in feeds containing sandeel oil (80%). Such high retention may represent an adaptation response to low temperature. Lower n-6 EFA retentions imply that more n-6 fatty acids were metabolized than n-3 EFAs. Feed oil influenced retention of the n-6 fatty acids, retention being lower for the salmon parr given the feeds containing sandeel oil (56% vs. 71%). This could indicate a higher tissue deposition of n-6 fatty acids when they are freely available via the diet. Abbreviations: AA – arachidonic acid (C20:4 n-6); DHA – docosahexaenoic acid (C22:6 n-3); EFA – essential fatty acid; EPA – eicosapentaenoic acid (C20:5 n-3); HUFA – highly-unsaturated fatty acid (\ge4 double bonds); MUFA – monounsaturated fatty acid (1 double bond); PL – phospholipid; PUFA – poly-unsaturated fatty acids (\ge2 double bonds); SFA – saturated fatty acid (no double bond); TAG – triacylglycerol. This revised version was published online in July 2006 with corrections to the Cover Date.     

Comparison of fatty acid contents of wild and cultured rainbow trout <Emphasis Type="Italic">Onchorhynchus mykiss</Emphasis> in Turkey

Abstract:   The total lipid content and fatty acid composition were determined in the flesh and skin of wild and cultured rainbow trout in Turkey. The effect of diet content was also investigated on cultured trout. Gas chromatography-mass spectrometry (GC-MS) was used for fatty acid analyses. Total lipid content of skin was higher than flesh in both types and when compared appreciably higher in cultured fish. The predominant fatty acid was palmitic acid (C16:0) in saturated fatty acids and oleic acid (C18:1n-9) in monounsaturated fatty acids. The amount of eicosapentaenoic acid was double in wild and docosahexaenoic acid (DHA) 1.5 times higher in cultured fish flesh. The n-3/n-6 ratio was higher in cultured fish than wild fish. The levels of palmitic, oleic, linoleic (C18:2n-6) and palmitoleic (C16:1n-7) acids were high in skin. The level of EPA was the same in skin of wild fish but 5.5 times higher in cultured fish, whereas the proportion of DHA in skin was lower for wild and 3.5 times higher in cultured fish. Wild fish had a high level of linoleic, arachidonic (C20:4n-6) and linolenic (C18:3n-3) acids. The total amount of n-3 and n-6 polyunsaturated fatty acids was higher in flesh of wild fish than cultured fish, contrary to skin of cultured fish. The data obtained demonstrated that fatty acid composition of cultured fish did not depend on that of feed.     

Nutritional regulation of hepatocyte fatty acid desaturation and polyunsaturated fatty acid composition in zebrafish (Danio rerio) and tilapia (Oreochromis niloticus)

The desaturation and elongation of [1-¹⁴C]18:3n-3 was investigated in hepatocytes of the tropical warm freshwater species, zebrafish (Danio rerio) and Nile tilapia (Oreochromis niloticus). The hepatocyte fatty acid desaturation/elongation pathway was assayed before and after the fish were fed two experimental diets, a control diet containing fish oil (FO) and a diet containing vegetable oil (VO; a blend of olive, linseed and high oleic acid sunflower oils) for 10 weeks. The VO diet was formulated to provide 1% each of 18:2n-6 and 18:3n-3, and so satisfy the possible EFA requirements of zebrafish and tilapia. At the end of the dietary trial, the lipid and fatty acid composition was determined in whole zebrafish, and liver, white muscle and brain of tilapia. Both zebrafish and tilapia expressed a hepatocyte fatty acid desaturation/elongation pattern consistent with them being freshwater and planktonivorous fish. The data also showed that hepatic fatty acid desaturation/elongation was nutritionally regulated with the activities being higher in fish fed the VO diet compared to fish fed the FO diet. In zebrafish, the main effect of the VO diet was increased fatty acid Δ6 desaturase activity resulting in the production of significantly more 18:4n-3 compared to fish fed the FO diet. In tilapia, all activities in the pathway were greater in fish fed the VO diet resulting in increased amounts of all fatty acids in the pathway, but primarily eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3). However, the fatty acid compositional data indicated that despite increased activity, desaturation of 18:3n-3 was insufficient to maintain tissue proportions of EPA and DHA in fish fed the VO diet at the same level as in fish fed the FO diet. Practically, these results indicate that manipulation of tilapia diets in commercial culture in response to the declining global fish oil market would have important consequences for fish fatty acid composition and the health of consumers. Scientifically, zebrafish and tilapia, both the subject of active genome mapping projects, could be useful models for studies of lipid and fatty acid metabolism at a molecular biological and genetic level. This revised version was published online in August 2006 with corrections to the Cover Date.     

The effect of different HUFA enrichment emulsions on the nutritional value of rotifers (Brachionus plicatilis) fed to larval haddock (Melanogrammus aeglefinus).

A feeding study was conducted in the winter 2001 to determine the effects of feeding rotifers (Brachionus plicatilis) enriched with various levels of essential fatty acids on the growth and survival of haddock larvae (Melanogrammus aeglefinus). Rotifer enrichment treatments were: 1) mixed algae, 2) high DHA (docosahexaenoic acid, 22:6n-3), 3) high DHA and EPA (eicosapentaenoic acid, 20:5n-3), and 4) DHA, EPA, and AA (arachidonic acid, 20:4n-6). Larvae were fed rotifers enriched with the different treatments from days 1 to 16 post-hatch. From day 17 until 25 all treatment groups were fed rotifers reared on mixed algae and then weaned onto the International Council for Exploration of the SEA (ICES) Standard Reference Weaning diet (http://allserv.rug.ac.t/aquaculture/rend/rend.htm) over a five day period. The experiment was terminated on day 41 post-hatch. The enrichment treatments affected the fatty acid composition of the rotifers and correlated with the accumulation of these fatty acids in the haddock larvae. However, no significant differences in larval growth or survival to 40 days post hatch were detected, suggesting that all treatments provided the minimal essential fatty acid requirements for haddock.     

Influence of egg lipids and fatty acids on egg viability, and their utilization during embryonic development of spotted wolf-fish, Anarhichas minor Olafsen

The changes in egg lipids and fatty acid compositions that occur during embryonic development of spotted wolf‐fish, Anarhichas minor, were examined by monitoring individual egg batches from the time of spawning (egg stripping) until hatching. The lipids, present as 3.7±0.1% of the wet mass of the freshly stripped eggs, contained high percentages of monoenes (monounsaturated fatty acids (MUFAs), ca. 33%) and polyenes (ca. 43%) and approximately 20% saturated fatty acids (SFAs). The fatty acid profiles were dominated by a small number of fatty acids. The major SFA was 16:0 (ca. 14%), the dominant MUFA was 18:1 n‐9 (ca. 21%), and among the polyenes, the n‐3 highly unsaturated fatty acids (HUFAs) 22:6 n‐3 docosahexaenoic acid (DHA) and 20:5 n‐3 eicosapentaenoic acid (EPA) were present in the highest concentrations (EPA, ca. 16%; DHA, ca. 19%). The n‐6 HUFA 20:4 n‐6 arachidonic acid (AA) was present as ca. 1% of the total fatty acids in the freshly stripped eggs. This resulted in an AA:EPA of ca. 0.07, which is lower than reported for eggs of many other fish species. As embryonic development progressed, the percentage contribution of AA to the total fatty acids almost doubled. There were also increases in the relative proportions of SFAs (due mainly to an increase in the percentage of 16:0 to ca. 16% at hatch) and DHA (to ca. 23%), and there was a corresponding decrease in the percentage of MUFAs (mostly brought about by a decrease in the percentage of 18:1 n‐9 to ca. 18% at hatch). The most marked changes occurred towards the end of incubation. The percentage of EPA changed little during incubation. This implies that there was selective retention of DHA, 16:0 and AA, and these fatty acids were probably incorporated into cell membranes. MUFAs, particularly 18:1 n‐9, seem to have been catabolized to provide energy for the developing embryo, and some EPA also seems to have been utilized as an energy source. Survival of eggs to the eyed stage (range ca. 10–80%) and to hatch (ca. 5–75%) was negatively correlated with the %AA, %EPA and AA:DHA of the freshly stripped eggs. There was also a negative correlation between AA:EPA and egg survival, which implies that there is not a universal requirement for a high AA:EPA to ensure high rates of survival of fish eggs.     

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.     

Effect of soybean oil and soybean lecithin on intestinal lipid composition and lipid droplet accumulation of rainbow trout, Oncorhynchus mykiss Walbaum

Rainbow trout (Oncorhynchus mykiss Walbaum) were fed purified diets containing fish oil for six weeks and then soybean lecithin or soybean oil for 25 days. The gastrointestinal tract segments, stomach, midgut and hindgut were then sampled for lipid and fatty acid composition and electron microscopy. Membrane lipid class composition was fairly similar in all three segments of trout fed fish oil. Hindgut contained slightly more phosphatidylserine than stomach and midgut, while midgut contained more phosphatidylcholine and less lysophospatidylcholine/sphingomyelin. Feeding soybean products appeared to marginally decrease free cholesterol. The fatty acid compositions of the main lipid classes showed significant regional differences. In control fish, stomach had higher levels of arachidonic acid (20:4n-6) and n-6 polyunsaturated fatty acids than midgut and hindgut, and lower content of docosahexaenoic acid (22:6n-3) and n-3 polyunsaturated fatty acids. Midgut phosphatidylethanolamine also had higher levels of saturated fatty acids and less n-3 polyunsaturated fatty acids than the other tissues. Feeding soybean products decreased the n-3/n-6 ratio mainly due to increases in linoleic (18:2n-6) and 20:4n-6 and decreases in 22:6n-3 and eicosapentaenoic acid (20:5n-3). Phosphatidylcholine and to a lesser extent phosphatidylethanolamine adapted more readily to dietary changes by major increases in 18:2n-6 and C₂₀₋₂₂ n-6 polyunsaturated fatty acids. The composition of phosphatidyl-serine and -inositol appeared to be under more strict metabolic control. Linoleic acid hardly increased at all while the increase in other n-6 polyunsaturated fatty acids was less pronounced than for the other lipid classes. Regardless of lipid class, stomach resisted dietary changes more strongly than midgut and hindgut. Increases in n-6 polyunsaturated fatty acids were minor as were the loss of n-3 polyunsaturated fatty acids. The dead-end product 20:2n-6 accumulated to a higher degree in hindgut phosphatidyl-ethanolamine and -coline compared to midgut and stomach, suggesting that the activity of Δ₆ desaturation is higher in the anterior part of the intestine where most of the lipid is absorbed. Feeding soybean oil caused massive accumulation of free lipid droplets in midgut enterocytes while little lipid droplets were observed in trout fed fish oil or soybean lecithin. Since both soybean products influenced intestinal composition to the same degree, altered fatty acid profiles in membranes is not responsible for the observed lipid accumulation. This supports previous observations in Arctic charr (Salvelinus alpinus L.), suggesting that fish may require exogenous phospholipids in order to sustain a sufficient rate of lipoprotein synthesis. This revised version was published online in July 2006 with corrections to the Cover Date.     

牙鲆幼鱼对EPA和DHA的营养需求

研究了EPA和DHA水平对牙鲆生长的影响,饲料中含0.5%EPA和1.0%～1.5%DHA能保证牙鲆幼鱼最适生长,鱼体水分最低,肝体指数最小,脂肪含量有较大幅度提高,肝脏极性脂中EPA和DHA达到最大积累;在肝脏和肌肉的非极性脂部分,各组间的脂肪酸组成没有显著变化,而极性脂部分能体现出饲料中n-3 HUFA含量对鱼体脂肪酸组成的影响,极性脂中的EPA和DHA含量远高于非极性脂;在肌肉和肝脏的极性脂和非极性脂中都含有较高的16:0和18:1n-9; 18:1n-9/n-3HUFA可以作为必需脂肪酸满足程度的一个判据,18:1n-9值的升高往往是缺乏必需脂肪酸的表现,在生长最佳时18:1n-9/n-3HUFA比值下降,为0.62和0.74.     

Dynamics of Total Body Fatty Acids During Early Ontogeny of Pikeperch (<Emphasis Type="Italic">Sander lucioperca</Emphasis>) Larvae

The fatty acid composition of pikeperch (Sander lucioperca) was determined according to their physiological status, during starvation (10 days) and feeding (28 days). In starved larvae, polyunsaturated, monounsaturated and saturated fatty acids were utilized as metabolic substrates until day 9. At day 10, all fatty acid levels remained stable or, at least, increased in larval body. Among fatty acids, docosahexaenoic acid 22:6 n-3 was used preferentially (20.3% from total fatty acids utilized) followed by palmitoleic acid 16:1 n-7 (13.9%) and then by oleic 18:1 n-9 (12.3%), linoleic 18:2 n-6 (10.1%), linolenic 18:3 n-3 (9.7%) and eicosapentaenoic 20:5 n-3 (9.1%) acids. On the other hand, arachidonic acid 20:4 n-6 was utilized very lowly (0.3%). In fed larvae, no utilization of body fatty acids was observed during the experiment. It seems that energy requirements (and others) of fed larvae were satisfied by feed.     

Maturation diet based on fatty acid content for male Penaeus monodon (Fabricius) broodstock

The contents of three essential fatty acids, arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), from wild Penaeus monodon broodstock were evaluated in comparison with natural diet fed P. monodon. Spermatophores of wild male broodstock contained higher levels of AA than those of artificial diet fed males. Polychaetes had higher proportion of AA to EPA and DHA at 5.8:5.5:1 in mud polychaetes followed by 12:7:1 in sand polychaetes, while DHA was a preferential n‐3 highly unsaturated fatty acid (HUFA) in squids and fish. The experimental feed was constructed to simulate the HUFA profile of polychaetes (AA:EPA:DHA as 5:1:1) and then fed to farmed male black tiger prawn broodstock for 1 month. The results exhibited comparable reproductive characteristics to wild male suggesting the possibility of replacing wild males with pond‐reared males. Rearing farmed males in a test unit for a month did not reduce the quality of prawn sperm. Reproductive performance indices (sperm sac weight, total number of sperm, percentage of live sperm, percentage of abnormal sperm) from the males of all treatments were not statistically different except in males fed with pellets. Control (live feeds) and combined diet provided better reproductive performance in pond‐reared males. Analysis of AA, EPA and DHA in reproductive tissues, hepatopancreas and muscle of treated animals in each treatment revealed an accumulation of dietary HUFA into reproductive tissues. No evidence of transfer of HUFA from hepatopancreas or muscle to spermatophore was found.     

Assessment of Fatty Acid Composition and Technological Properties of Northern Pike (Esox lucius) Fillets: The Effects of Fish Origin and Sex

The aim of the study was to investigate the effects of northern pike origin (wild vs. farmed) and sex (female vs. male) on chemical composition, including fatty acids, and technological properties of fresh fillets. Fish origin influenced moisture, protein, fat, and ash contents, pH and color of the fillets, and the proportion of 22 out of 25 determined fatty acids, whereas sex affected expressible water, pH, lightness and redness of fillets, and only a single fatty acid (C20:0) proportion. Farmed pike had higher protein and fat content and lower moisture and ash than wild pike. Higher proportion and content of total polyunsaturated and n-3 fatty acids, as well as lower n-6/n-3 ratio, were found in farmed pike. Thus, it can be concluded that the commercial feed positively affected fatty acid proportion and content in the fish tissue and increased its nutritional value.     

Can Different Body Tissues of Two Sea Cucumbers Supply a Fair Amount of Omega 3 for Health Benefit?

The lipid content and fatty acids profile of different tissues of Holothuria tubulosa and H. polii were analyzed to assess the suitability of the central Mediterranean species as a potential marine resource for fatty acids, in particular omega-3 polyunsaturated fatty acids (n-3 PUFAs). Simultaneously, their important indices for human health were evaluated. Gonad and respiratory tree had the highest lipid content, while the body had the lowest values. The results showed significant differences between species and among the different portions analyzed. Internal tunic and longitudinal muscle of H. tubulosa exhibited the highest PUFA proportion (55.3 and 46.4%, respectively). Eicosapentaenoic acid (EPA, C20:5n-3) and arachidonic acid (ARA, C20:4n-6) were the most abundant PUFAs in both species, with a favorable n-3/n-6 ratio in all tissues. The atherogenic and thrombogenicity indices and hypocholesterolaemic/hypercholesterolaemic fatty acid ratio suggested the high-quality of this food, similar to the nutritional values of most popular fish.     

Echium oil increased the expression of a Δ4 Fads2 fatty acyl desaturase and the deposition of n-3 long-chain polyunsaturated fatty acid in comparison with linseed oil in striped snakehead (<Emphasis Type="Italic">Channa striata</Emphasis>) muscle

Despite the potential of vegetable oils as aquafeed ingredients, a major drawback associated with their utilization is the inferior level of beneficial n-3 long-chain polyunsaturated fatty acids (LC-PUFA). Echium oil (EO), which is rich in stearidonic acid (SDA, 18:4n-3), could potentially improve the deposition of n-3 LC-PUFA as the biosynthesis of LC-PUFA is enhanced through bypassing the rate-limiting ?6 desaturation step. We report for the first time an attempt to investigate whether the presence of a desaturase (Fads2) capable of ?4 desaturation activities and an elongase (Elovl5) will leverage the provision of dietary SDA to produce a higher rate of LC-PUFA bioconversion. Experimental diets were designed containing fish oil (FO), EO or linseed oil (LO) (100FO, 100EO, 100LO), and diets which comprised equal mixtures of the designated oils (50EOFO and 50EOLO) were evaluated in a 12-week feeding trial involving striped snakeheads (Channa striata). There was no significant difference in growth and feed conversion efficiency. The hepatic fatty acid composition and higher expression of fads2 and elovl5 genes in fish fed EO-based diets indicate the utilization of dietary SDA for LC-PUFA biosynthesis. Collectively, this resulted in a higher deposition of muscle eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) compared to LO-based diets. Dietary EO improved the ratio of n-3 LC-PUFA to n-6 LC-PUFA in fish muscle, which is desirable for human populations with excessive consumption of n-6 PUFA. This study validates the contribution of SDA in improving the content of n-3 LC-PUFA and the ratio of EPA to arachidonic acid (ARA, 20:4n-6) in a freshwater carnivorous species.