Conjugated linoleic acid in diets for lambari (Astyanax altiparanae) (Garutti & Britski, 2000)

This study aimed to evaluate the effect of different levels of conjugated linoleic acid (CLA) on growth performance, carcass chemical composition and fatty acid profile of lambari (Astyanax altiparanae). A completely randomized experimental design with six treatments, diets with graded levels of CLA (0.0, 5.0, 10.0, 15.0, 20.0 and 25.0 g kg^?1) and five repetitions. Fish (n = 570; weight: 1.58 ± 0.23 g) were distributed into 30 (70‐L) aquaria and fed the experimental diets during 90 days. No effects of dietary supplementation with CLA on fish performance and carcass chemical composition were observed. CLA influenced carcass fatty acid profile, a positive relationship was found for 16:1 n‐9, 18:1 n‐9, 18:2(cis‐9, trans‐11), 18:2(trans‐10, cis‐12) and 20:1 n‐9, and a negative relationship was found for 15:1 n‐7, 16:0, 16:1 n‐5, 18:2 n‐6, 18:3 n‐3, 20:5 n‐3 and 22:4 n‐6. Total CLA and monounsaturated fatty acids (MUFA) linearly increased with the increase in dietary CLA, while saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA) of n‐6 and n‐3 series linearly decreased. Dietary CLA can be incorporated into the lambari (A. altiparanae) muscle, and the fish can be used as functional foods, because CLA is related to the prevention of various diseases in humans.     

Menthol as anaesthetic for lambari Astyanax altiparanae (Garutti & Britski 2000): attenuation of stress responses

The anaesthetic potential of menthol was evaluated in lambari Astyanax altiparanae by exposing fingerlings to concentrations 50, 100, 150, 200, 250 and 300 mg L^?1 and measuring the induction and recovery times to deep anaesthesia, the mortality rates during and 96 h after procedure and after 6 min of continuous exposure. The effect of menthol on stress responses were evaluated by comparing glucose and cortisol levels of juveniles subjected to anaesthesia (50 mg L^?1), stress (air exposure) or pre‐anaesthesia associated to stress. All concentrations induced deep anaesthesia within 0.5 to 1 min, with recovery between 1.83 and 4.16 min, without mortality during the induction or up to 96 h after exposure. Induction time decreased and recovery time increased linearly as the menthol concentration increased. Continuous exposure to 50, 100 and 150 mg L^?1 concentrations resulted in mortality rates of 0%, 20% and 80% respectively. Anaesthesia or air exposure increase blood glucose but prior anaesthesia with menthol suppressed the elevation of cortisol caused by stress. Menthol has an anaesthetic effect and attenuates the stress response in lambari and 50 mg L^?1 is the most effective concentration for inducing deep anaesthesia in 1.0 min, safe for up to 6 min exposure.     

Optimal dietary methionine + cystine requirement for finishing lambari,Astyanax altiparanae (Garutti and Britski, 2000)

A 95‐day feeding trial was conducted to quantify the methionine + cystine requirement for finishing lambari, Astyanax altiparanae (6.10 ± 0.11 g). Six extruded isoproteic (310.14 g/kg crude protein) and isoenergetic (19.76 MJ/kg gross energy) diets were prepared to contain 6.71, 8.31, 11.31, 13.12, 15.59 and 19.74 g/kg dry diet of methionine + cystine. Quadruplicate groups of female lambari were randomly assigned to 24 aquaria (70 L each) and fed to apparent satiety six times daily. The methionine + cystine requirement was determined by quadratic regression analysis of growth performance, whole body composition, muscle development, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activity against dietary methionine + cystine concentrations, at 5% significance. Fish fed 6.71–11.31 g/kg dry diet of methionine + cystine showed increased weight gain, per cent weight gain, specific growth rate and protein efficiency ratio. There were no significant differences in whole body composition, muscle growth and activity of AST and ALT in fish fed the dietary treatments. In conclusion, according to the second‐order polynomial analysis of weight gain, the optimum dietary methionine + cystine requirements for finishing lambari were estimated to be 13.66 g/kg dry diet (4.40% dietary protein).     

Essential fatty acids in Atlantic salmon: effects of increasing dietary doses of n-6 and n-3 fatty acids on growth, survival and fatty acid composition of liver, blood and carcass

Atlantic salmon fry (4 g) were fed for 4 months on semi-synthetic diets containing fatty acid methyl esters of either 18:2 n-6, 18:3 n-3 or a mixture of equal amounts of 20:5 n-3 and 22:6 n-3. The different amounts of polyunsaturated fatty acids added were 0, 0.1, 0.2, 0.5, 1 and 2% (by dry weight). Increasing levels of dietary n-3 fatty acids up to 1% gave faster growth rates in salmon fry, and fish fed the mixture of 20:5 n-3 and 22:6 n-3 seemed to grow faster than fish fed only 18:3 n-3. No significant effect on growth rate was seen when the dietary level of 18:2 n-6 was increased. Dietary inclusions of n-3 fatty acids reduced the mortality of salmon, while dietary 18:2 n-6 had no such beneficial effects.
The dietary treatments caused substantial changes in the fatty acid composition of blood and liver phospholipids (PL), whereas the total lipid fraction of the carcass was less affected. Increasing doses of 18:2 n-6 in the diet resulted in an increased percentage of 20:4 n-6 in liver and blood PLs, while the percentage of 20:3 n-9 decreased. The percentage of 18:2 n-6 also increased in liver, blood and carcass. Dietary 18:3 n-3 resulted in increased percentages of 18:3 n-3 and 20:5 n-3 in liver PLs, while the percentage of 20:3 n-9 decreased. There was, however, no significant increase in the percentage of 22:6 n-3. Dietary 18:3 n-3 produced no significant changes in the composition of blood fatty acids, but increased the percentage of 18:3 n-3 in the carcass. The dietary combination of the n-3 fatty acids 20:5 and 22:6 resulted in an increased percentage of 22:6 n-3 in blood and liver lipids and a decreased percentage of 20:3 n-9, but there were no changes in the percentage of 20:5 n-3.     

A quantitative comparison between diet and body fatty acid composition in wild northern pike (Esox lucius L.)

The fatty acid compositions of wild female northern pike (Esox lucius L.) and their principle prey species were compared to assess the extent to which pike modify the relative abundance of dietary fatty acids during assimilation and to indicate the optimum dietary content of essential fatty acids (EFAs) for pike. Only minor differences existed between the estimated whole body fatty acid composition of pike and diet fatty acid composition as calculated from the contribution of each prey species to the pike's diet. Saturated fatty acids comprised a slightly higher percentage of diet lipids (25% wt) than of pike lipids (21% wt) whereas monounsaturated fatty acids were less abundant in diet lipids (26% wt) than in pike (29% wt). Percentages of total polyunsaturated fatty acids (PUFAs), n - 3 fatty acids, and n - 6 fatty acids were approximately 43, 30, and 13% wt respectively and differed by less than 1% wt between pike and diet lipids. Among individual PUFAs, the largest differences occurred in 20:5 (n-3) and 22:6(n-3) which comprised, on average, 9.6 and 14.7% wt respectively of diet lipids and 5.9 and 18.3% wt respectively of pike lipids. The close similarity in fatty acid composition between pike and their diet suggests that pike may have limited abilities to elongate and desaturate 18 carbon PUFAs and may require specific long chain PUFAs in the diet. The n-3 PUFA content of the pike's natural diet may exceed the minimum EFA requirements of better studied species such as rainbow trout and turbot.     

Lipid and fatty acid compositions of muscle from farmed and wild adult turbot

The aim of this study was to compare the total lipid, neutral lipid, phospholipid contents, phospholipid class distribution and fatty acid composition of these lipids in muscle of wild and farmed turbot (Scophthalmus maximus) of similar body size. The results showed that muscle of farmed turbot had a higher lipid content than that of wild turbot (1.06% versus 0.64%) because they contained more neutral lipids (0.52% versus 0.24%) and more phospholipids (0.54% versus 0.40%).Distribution of phospholipid classes in muscle of both wild and farmed turbot was similar with 67–70% phosphatidyl choline, 22–25% phosphatidyl ethanolamine and 4.4–5.2% phosphatidyl inositol plus phosphatidyl serine and 2.4–2.9% sphingomyeline.Compared to wild turbot, all of the lipid classes from farmed turbot contained lower proportions of long chain -3 PUFA and 20:4 -6 and conversely higher proportions of 20:1 and 22:1. The ratio between -3 and -6 polyunsatured fatty acids was higher in all the lipid fractions of wild turbot than in those of farmed fish (8.8 versus 4.2 in total lipids, 11.0 versus 3.3 in neutral lipids, 7.9 versus 4.7 in phospholipids). © Rapid Science Ltd. 1998     

The effect of culture on morphology, lipid and fatty acid composition, and polyunsaturated fatty acid metabolism of rainbow trout (Oncorhynchus mykiss) skin cells

Rainbow trout (Oncorhynchus mykiss) skin cell cultures were obtained by trypsinization of the tissue and grown in Leibovitz L-15 medium. Lipid class compositions, and fatty acid profiles of total lipids and individual phospholipid classes were determined at different times of culture. The metabolism of polyunsaturated fatty acids (PUFA) was investigated by incubating primary cultures after 7 and 14 days with [1-¹⁴C]18:2n-6 and [1-¹⁴C-]18:3n-3. The change in morphology between epithelial-like primary cultures and fibroblastic-like secondary subcultures was accompanied by alterations in the lipid composition. Polar lipids became predominant by 14 days in culture. The relative proportions of phosphatidylcholine (PC), the most abundant phospholipid, phosphatidylinositol and cholesterol increased significantly, while sphingomyelin decreased. Saturated fatty acids, 18:1n-9, n-6 and n-9PUFA were more abundant in total lipid in cultures at 14 days and 4 months than in cells initially isolated which contained higher percentages of longer chain monoenes and n-3PUFA. The changes in fatty acid composition with time in culture were observed in all the major phospholipid classes. Rainbow trout skin cells in culture desaturated and elongated both 18:2n-6 and 18:3n-3, with 20:4n-6 and 20:5n-3 being the most abundant products, respectively. PC presented the highest incorporation of radioactivity, especially following incubation with 18:3n-3. Lipid metabolism in general increased with the age of primary cultures, with both the amount of C18 PUFA incorporated and metabolized by desaturation/elongation significantly increased in 14 day cultures compared to 7 day cultures. Product/precursor ratios calculated for both n-6 and n-3 fatty acids showed that, while 6 desaturase activity was increased significantly with cell age, 5 desaturase activity was more affected by the fatty acid series, with 18:3n-3 being more readily transformed to 20:5n-3 than 18:2n-6 to 20:4n-6. Further desaturation of 20:5n-3 to hexaenes was low. Overall, the data suggested that the trout skin cell cultures were more similar to mammalian skin fibroblasts than mammalian epidermal/keratinocyte cultures.     

Influence of dietary palm oil on growth, tissue fatty acid compositions, and fatty acid metabolism in liver and intestine in rainbow trout (Oncorhynchus mykiss)

This study aimed to investigate the effects of dietary crude palm oil (CPO) on fatty acid metabolism in liver and intestine of rainbow trout. Triplicate groups of rainbow trout for 10 weeks at 13 °C were fed on diets in which CPO replaced fish oil (FO) in a graded manner (0–100%). At the end of the trial, fatty acid compositions of flesh, liver and pyloric caeca were determined and highly unsaturated fatty acid (HUFA) synthesis and fatty acid oxidation were estimated in isolated hepatocytes and caecal enterocytes using [1‐¹⁴C]18:3n‐3 as substrate. Growth performance and feed efficiency were unaffected by dietary CPO. Fatty acid compositions of selected tissues reflected the dietary fatty acid composition with increasing CPO resulting in increased proportions of 18:1n‐9 and 18:2n‐6 and decreased proportions of n‐3HUFA, 20:5n‐3 and 22:6n‐3. Palmitic acid, 16:0, was also increased in flesh and pyloric caeca, but not in liver. The capacity of HUFA synthesis from 18:3n‐3 increased by up to threefold in both hepatocytes and enterocytes in response to graded increases in dietary CPO. In contrast, oxidation of 18:3n‐3 was unaffected by dietary CPO in hepatocytes and reduced by high levels of dietary CPO in enterocytes. The results of this study suggest that CPO can be used at least to partially replace FO in diets for rainbow trout in terms of permitting similar growth and feed conversion, and having no major detrimental effects on lipid and fatty acid metabolism, although flesh fatty acid compositions are significantly affected at an inclusion level above 50%, with n‐3HUFA reduced by up to 40%.     

The fatty acid compositions of established fish cell lines after long-term culture in mammalian sera

The effect of long-term culture of fish cells in mammalian serum on the phospholipid fatty acid composition was investigated. All the cell lines studied had much lower levels of polyunsaturated fatty acids (PUFA) than those found in intact fish tissues. In particular (n-3) PUFA were considerably depleted in the cultured cell lines, leading to very low (n-3)/(n-6) ratios in all the phospholipid classes. In general the cells were rich in 18:1, 16:0, 18:0 and 16:1 with 20:4(n-6) and 22:6(n-3) as the major PUFA. The fatty acid composition reflected the composition of the fetal calf serum added to the media rather than their fish tissue origins. The results were discussed in relation to the roles of PUFA in general cell metabolism and more specifically the role of (n-3) PUFA in fish cells.     

The essential fatty acid requirement of milkfish (Chanos chanos Forsskal)

The essential fatty acid (EFA) requirement of milkfish was examined by a 12-week feeding trial using defined, purified diets at water temperature of 28–29°C and salinity of 32. The test diets contained varying levels of 18:0 (triglyceride form, TG), 18:3(n–3), 18:2(n–6) and (n–3) highly unsaturated fatty acids (n–3 HUFA). Milkfish juveniles were starved for 7 days and were than fed lipid-free diet for 30 days before the initiation of feeding trials. Low growth and feed efficiency together with high mortalities were observed in fish fed the lipid-free diet as well as in the EFA-deficient diet. Supplementation of 2% 18:2(n–6) to the tristearin based diet did not improve growth rate of milkfish as effectively as feeding with (n–3) fatty acids. The highest weight gain was obtained in milkfish fed a combination of 5% 18:0 + 1.0% 18:3(n–3) + 0.5% 20:5(n–3) + 0.5% 22:6(n–3) although the supplementation of 2% 18:3(n–3) alone or combination of 0.5% 20:5(n–3) + 0.5% 22:6(n–3) to the tristearin based diets were also effective for improvement of growth. Thus, (n–3) fatty acids, such as 18:3(n–3) and (n–3)HUFA were nutritionally more important than 18:2(n–6) for milkfish. The fatty acid composition of the polar lipids from whole body of milkfish juveniles fed the various test diets were influenced by the composition of the dietary fatty acids.     

The conversion of linoleic acid and linolenic acid to longer chain polyunsaturated fatty acids by Tilapia (Oreochromis) nilotica in vivo

Tilapia (Oreochromis) nilotica were fed either a commercial diet containing 2.2% (n-3) and 0.5% (n-6) polyunsaturated fatty acids (PUFA), or a diet containing 1.0% methyl linoleate as the only PUFA. The fatty acid composition of tissue lipids generally reflected that of the diet. Fish from both dietary groups were injected intraperitoneally with ¹⁴C-labelled linoleic acid, 18:2 (n-6), or linolenic acid, 18:3 (n-3), and the distribution of radioactivity in tissue lipids examined. The conversion of both 18:2 (n-6) and 18:3 (n-3) to longer chain PUFA was lower in fish fed the commercial diet than in those fed the diet containing only 18:2 (n-6). Half of the radioactivity from both substrates recovered in liver polar lipids was present in C20 and C22 PUFA with fish maintained on the experimental diet. It is concluded that T. nilotica is capable of elongating and desaturating both 18:2 (n-6) and 18:3 (n-3), but that this conversion is suppressed by dietary longer chain PUFA. NERC Unit of Aquatic Biochemistry     

Polyunsaturated fatty acid metabolism in a cell culture model of essential fatty acid deficiency in a freshwater fish, carp (Cyprinus carpio)

Proliferation of an essential fatty acid deficient cell line from carp (EPC-EFAD; epithelioma papillosum carp-essential fatty acid deficient) is stimulated by supplementing the cells with C₂₀, but not C₁₈ polyunsaturated fatty acids (PUFA). It is hypothesized that the differential ability of the PUFA to stimulate proliferation of the EPC-EFAD cells may be related to the extent of the cells' ability to desaturate and elongate C₁₈ PUFA. In the present study, the metabolism of ¹⁴C-labeled C₁₈ and C₂₀ PUFA was investigated in EPC-EFAD cells in comparison with normal EPC cells. The incorporation of all the PUFA was significantly greater in EPC-EFAD cells but the rank order, 20:5n-3 > 18:3n-3 = 18:2n-6 >20:4n-6 was the same in both cell lines. The proportion of radioactivity from all labeled PUFA recovered in phosphatidylethanolamine and total polar lipids was significantly lower in EPC-EFAD cells compared to EPC cells, whereas the proportion of radioactivity recovered in all the other phospholipid classes and total neutral lipid was greater in EPC-EFAD cells. Both cell lines desaturated[1-¹⁴C]18:3n-3 and [1-¹⁴C]20:5n-3 to a greater extent than the corresponding (n-6) substrates but the desaturation of all the ¹⁴ C-labeled PUFA was significantly greater in EPC-EFAD cells compared to EPC cells. The results showed that, although essential fatty acid deficiency had several significant effects on PUFA metabolism in EPC cells, the fatty acid desaturation/elongation pathway was not impaired in EPC-EFAD cells and so they can desaturate 18:3n-3 to 20:5n-3 and 22:6n-3, and 18:2n-6 to 20:4n-6. However, 20:4n-3 and 20:3n-6, and not 20:4n-6 and 20:5n-3, were the predominant C₂₀ PUFA produced by the elongation and desaturation of [1-¹⁴C]18:3n-3 and [1-¹⁴C]18:2n-6, respectively. Therefore, the previously reported inability of 18:3n-3 and 18:2n-6, compared to 20:5n-3 and 20:4n-6, to stimulate proliferation of the cells is apparently not due to a general deficiency in the fatty acid desaturation pathway in EPC-EFAD cells but may be related to potential differences in eicosanoid profiles in cells supplemented with C₁₈ PUFA compared to C₂₀ PUFA.     

闽东海域繁殖期雌性棘头梅童鱼亲鱼不同组织的脂肪酸组成分析

为获知棘头梅童鱼亲鱼性腺发育后期脂类及脂肪酸蓄积特点,采用内标定量法,对性腺发育至Ⅳ期的雌性棘头梅童鱼亲鱼肌肉、肝脏和卵巢组织中的脂肪及脂肪酸含量进行了测定,并比较分析了3种组织中的脂肪酸组成。结果表明:雌性棘头梅童鱼亲鱼卵巢、肝脏和肌肉中脂肪的质量分数分别为(4.84±0.05)%、(2.66±0.05)%和(0.56±0.05)%,不同组织间具有显著性差异(P<0.05)。雌性棘头梅童鱼亲鱼的卵巢、肌肉和肝脏中分别检出29种脂肪酸,含量最高的饱和脂肪酸依次为C16∶0、C18∶0和C14∶0;含量最高的单不饱和脂肪酸依次为C16∶1、C18∶1n9c和C20∶1;含量最高的多不饱和脂肪酸依次为C22∶6n3(DHA)、C20∶5n3(EPA)和C20∶4n6(ARA)。从相对含量来看,肌肉中饱和脂肪酸的质量分数为(58.22±0.24)%,显著高于肝脏(52.71±0.24)%和卵巢(36.42±0.24)%(P<0.05);卵巢中单不饱和脂肪酸的质量分数为(23.78±0.09)%,显著高于肌肉(16.15±0.07)%和肝脏(10.79±0.05)%(P<0.05);卵巢中多不饱和脂肪酸质量分数为(39.79±0.19)%,显著高于肝脏(36.49±0.21) %和肌肉(25.63±0.19)%(P<0.05)。肌肉、肝脏和卵巢中EPA和DHA的总量依次升高,质量分数分别为(19.34±0.15)%、(26.59±0.16)%和(27.78±0.13)%。卵巢、肝脏和肌肉组织中的DHA/EPA分别为1.95、2.28和1.89,n-3系和n-6系多不饱和脂肪酸的比值分别为3.29、3.81和6.25。     

野生和人工养殖褐牙鲆亲鱼不同组织氨基酸的比较

为了探明野生和人工养殖褐牙鲆亲鱼的繁育性能和卵巢发育之间的关系,采用生物化学方法,将处于Ⅲ~Ⅳ期和Ⅴ期的野生和养殖褐牙鲆亲鱼中肌肉、肝脏及卵巢氨基酸含量分别进行测定,结果表明,(1)褐牙鲆肌肉、肝脏、卵巢3种组织器官中总氨基酸含量大小关系为肌肉>卵巢>肝脏;(2) 发育同期的野生和养殖亲鱼肌肉中大部分氨基酸含量差异不显著（P>0.05）,并且随着性腺的成熟,野生和养殖亲鱼肌肉中大部分氨基酸较为稳定,其中含量变化显著的必需氨基酸为蛋氨酸、组氨酸（P<0.05）;(3) 发育同期的养殖亲鱼肝脏中大部分氨基酸含量高于野生亲鱼,随着性腺发育,野生和养殖亲鱼肝脏中氨基酸含量呈明显上升趋势;(4) 在Ⅴ期卵巢氨基酸组成中,除蛋氨酸、组氨酸含量存在显著差异外,野生和养殖亲鱼卵巢中氨基酸总量及必需氨基酸总量均不存在显著差异（P>0.05）,同时,随着性腺发育,野生和养殖亲鱼卵巢中氨基酸含量呈明显上升趋势,差异显著的必需氨基酸有精氨酸、蛋氨酸、组氨酸（P<0.05）。     

Muscle fatty acid composition and oxidative stress indices of Arctic charr, Salvelinus alpinus (L.), in relation to dietary polyunsaturated fatty acid levels and temperature

The influence of feeding high levels of polyunsaturated fatty acids (PUFA) on muscle fatty acid composition and indices of oxidative damage was examined in Arctic charr, Salvelinus alpinus (L.). All diets contained 100 g kg^?1 lipid of dry weight. Two diets contained marine fish oils giving a PUFA level of 250 g kg^?1 and 500 g kg^?1 of lipid. The remaining two diets contained vegetable oils high in either 18:2n-6 or 18:3n-3, giving a PUFA level of more than 500 g kg^?1 of dietary lipid. The charr were maintained at 8°C until their weight doubled, and were then transferred to 0.8°C for 30 days. Growth was similar in all groups. The fatty acid compositions of muscle were influenced by dietary PUFA but were less diverse than those of the diets. The overall pattern of fatty acid compositions indicated preferential desaturation and elongation of n-3 PUFA coupled with selective oxidation of 18:2n-6. Total n-3 PUFA content in TAG was always lowered compared with the diet, suggesting a specific mechanism for the removal of these fatty acids. Subjecting the fish to low temperature increased PUFA content in muscle of charr fed the 250 g kg^?1 marine n-3 PUFA diet, but had no effect on the other treatments. For fish at 8°C, no significant differences were found between groups in terms of haematocrit, plasma alanine aminotransferase (ALAT), and plasma and muscle thiobarbituric acid reactive substances (TBARS), although there was a tendency towards increased levels of TBARS in the group receiving 500 g kg^?1 marine n-3 PUFA of lipid. Subjecting the muscle to forced oxidative conditions resulted in increases in TBARS in all groups, particularly those fed 500 g kg^?1 marine n-3 PUFA. Lowering the environmental temperature corresponded with a further increase in the plasma ALAT and muscle TBARS in this group. It is concluded that feeding diets containing high levels of long-chain n-3 PUFA may be detrimental to the fish's health and flesh quality, particularly at low environmental temperatures.     

雌性成体点篮子鱼不同组织的脂肪酸组成分析

测定和比较了性腺发育至Ⅲ期的雌性成体点篮子鱼肌肉、肝脏和卵巢组织中总脂含量及其脂肪酸组成。结果表明:(1)肌肉、肝脏和卵巢中的总脂含量分别为(2.79±0.15)%、(12.78±1.30)%和(2.85±0.17)%。肌肉与卵巢间总脂含量差异不显著(P>0.05),肝脏总脂含量约为肌肉和卵巢总脂含量的6倍,呈显著性差异(P<0.05);(2)肝脏中SFA总量明显高于肌肉和卵巢,3种组织中SFA含量呈显著性差异(P<0.05)。单不饱和脂肪酸(MUFA)中,C18∶1ω9 c1(顺式)在3种组织中含量最高,肌肉、肝脏和卵巢中的含量分别为21.86%、23.66%和23.96%,肝脏与卵巢间无显著差异(P>0.05),而与肌肉间差异显著(P<0.05);多不饱和脂肪酸(PUFA)、3PUFA和6PUFA在卵巢中含量最高,其次是肌肉,肝脏中含量最低,且三者之间的差异显著(P<0.05)。     

Effects of dietary lipids on the fatty acid composition of triglycerides and phospholipids in tissues of white sturgeon

Eight purified diets were fed to juvenile white sturgeon, Acipenser transmontanus Rick, for 9 weeks to investigate the effect of dietary lipids on the fatty acid composition of phospholipids and triglycerides from muscle, liver and brain. The diets contained 150 g kg^?1 of oils from canola, corn, cod liver, lard, linseed, soybean, safflower, or a control mixture (corn oil/cod liver oil/lard, 1:1:1, by wt). Dietary lipids significantly (P≤ 05) affected the composition of tissue triglycerides and phospholipids. Tissue triglyceride fatty acid composition ranged widely, in parallel with the dietary lipids, while phospholipids changes were more conservative. Brain phospholipid fatty acid composition was less responsive to diet compared with that in muscle and liver. Considerable amounts of n-6 and n-3 long chain polyun-saturated fatty acids (> C₂₀) were found in triglycerides and phospholipids with all diets, demonstrating that white sturgeon can desaturate and elongate linoleic acid (18:2n–6) and linolenic acid (18:3n–3). Further, the products of the Δ6 desaturase, i.e. 18:3 n–6 and 18:4n–3, were relatively abundant in triglyceride, suggesting that the Δ6 desaturase might not be a limiting step in the process in white sturgeon. Nevertheless, accumulation of both EPA and DHA was greater in the sturgeon fed fish oil than those fed linseed oil, indicating that muscle triglyceride EPA and DHA levels are best enhanced by diets rich in preformed EPA and DHA.     

Lipid content and fatty acid composition in female American shad,Alosa sapidissima,at different stages of ovarian development under reared conditions

The fatty acid accumulation in broodstock influences the fecundity of spawners as well as egg quality. A comprehensive understanding of the lipid and fatty acid changes in broodstock during the reproductive period can increase our knowledge of the nutritional requirements in artificial breeding programs. The study assessed the lipid and fatty acid compositions of muscle, liver and ovary of American shad at different stages of reproductive development under reared conditions. The results indicated that there were significant differences in lipid content among ovary, liver and muscle. Mean total lipid levels in ovary, liver and muscle were 15.92%–10.87%, 13.62%–6.89%, 10.39%–6.11% respectively. During the development season, the total lipid content in muscle in stages V and VI were significantly lower than those in stages II and III. The total lipid content in liver in stages IV, V and VI was significantly lower than in stages II and III, whereas the total lipid content in the ovary increased significantly as the gonad developed and reached its highest value at stage V. From II to VI stage, the liver content of docosahexaenoic acid (DHA) decreased and the ovarian content of DHA increased, whereas the content of eicosapentaenoic acid (EPA) remained relatively constant. The content of C16:0 and C18:1n‐9 decreased in muscle and liver, but significantly increased in ovary. It is therefore suggested that the lipids were preferentially transferred from muscle and liver to ovary beginning in stage IV as the gonad matured. At stage IV, the lipid transfer accelerated, and saturated and unsaturated fatty acids, such as C16:0, C18:1n‐9, DHA, EPA and arachidonic acid, were selectively transferred to and conserved in ovaries.     

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.