Influence of one selected Tisochrysis lutea strain rich in lipids on Crassostrea gigas larval development and biochemical composition

Effects of a remarkably high overall lipid Tisochrysis lutea strain (T+) upon gross biochemical composition, fatty acid (FA), sterol and lipid class composition of Crassostrea gigas larvae were evaluated and compared with a normal strain of Tisochrysis lutea (T) and the diatom Chaetoceros neogracile (Cg). In a first experiment, the influence of different single diets (T, T+ and Cg) and a bispecific diet (TCg) was studied, whereas, effects of monospecific diets (T and T+) and bispecific diets (TCg and T+Cg) were evaluated in a second experiment. The strain T+ was very rich in triglycerides (TAG: 93–95% of total neutral lipids), saturated FA (45%), monounsaturated FA (31–33%) and total fatty acids (4.0–4.7 pg cell^?1). Larval oyster survival and growth rate were positively correlated with 18:1n‐7 and 20:1n‐7, in storage lipids (SL), and negatively related to 14:0, 18:1n‐9, 20:1n‐9, 20:4n‐6 and trans‐22‐dehydrocholesterol in membrane lipids (ML). Surprisingly, only the essential fatty acid 20:5n‐3 in SL was correlated positively with larval survival. Correlations suggest that physiological disruption by overabundance of TAG, FFA and certain fatty acids in larvae fed T+ was largely responsible for the poor performance of these larvae. ‘High‐lipid’ strains of microalgae, without regard to qualitative lipid composition, do not always improve bivalve larval performance.     

Evaluation of Schizochytrium meal in microdiets of Pacific white shrimp (Litopenaeus vannamei) larvae

A feeding trial was conducted to assess the effects of dietary Schizochytrium meal supplementation on survival, growth performance, activities of digestive enzymes and fatty acid composition in Pacific white shrimp (Litopenaeus vannamei) larvae (initial body weight 4.21 ± 0.10 mg). Four isonitrogenous and isolipidic diets were formulated to contain graded levels of Schizochytrium meal: 0% (S0, the control diet), 2% (S2), 4% (S4) and 6% dry matter (S6). Results showed that there was no significant difference in survival of shrimps among dietary treatments (P > 0.05). Shrimps fed diets with 2% and 4% microalgae meal had significantly higher specific growth rate (SGR) than that of shrimps fed diets with 0% and 6% microalgae meal, and no significant differences were observed between shrimps fed diets with 2% and 4% microalgae meal (P > 0.05). Activity of trypsin in the pancreatic and intestinal segments, and activity of amylase in the pancreatic segments were not significantly affected by dietary microalgae meal levels (P > 0.05). Specific activities of both alkaline phosphatase and leucine‐aminopeptidase in intestine and purified brush border membrane of intestine were significantly higher in shrimps fed diet with 2% microalgae meal (P < 0.05). There were no significant differences in C18:2n‐6, n‐3 fatty acids, n‐6fatty acids, PUFA and n‐3/n‐6 in muscle samples among dietary treatments. C16:1n‐7, C18:1n‐9, MUFA, C18:3n‐3 and C20:5n‐3 decreased, however, C20:4n‐6 increased in the muscle as dietary microalgae meal level increased. In conclusion, 4% Schizochytrium meal in microdiets of shrimps can improve growth performance and may be a valuable additive in the microdiets of shrimps.     

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.     

Performance of intensively farmed Murray cod Maccullochella peelii peelii (Mitchell) fed newly formulated vs. currently used commercial diets, and a comparison of fillet composition of farmed and wild fish

Murray cod is a top‐order carnivore with high culture potential. Currently, there are no commercial diets formulated specifically for Murray cod. In this study, results of two growth trials on Murray cod (80–83.5‐g mean initial weight), conducted in commercial settings, using two laboratory‐formulated diets (DU1 and DU2; 48.9% and 49.1% protein, and 16.9% and 16.1% lipid, respectively, on a dry matter basis), and two commercial diets, formulated for other species (salmon – CD/S and barramundi – CD/B) but used in Murray cod farming are presented. The two commercial diets had less protein (46.6% and 44.4%) but higher lipid (21.7% and 19.5%). The energy content of the feeds tested was similar (about 20–22 kJ g^?1). The growth performance and feed utilization of Murray cod did not differ significantly amongst the diets, but the food conversion ratio and % protein efficiency ratio in fish fed the DU1 and DU2 diets were consistently better. There was significantly less carcass and muscle lipid deposition in fish fed with the latter diets. Of the fatty acids in muscle, the lowest amounts (in μg mg lipid^?1) of n‐3 (262.5±2.9), n‐6 (39.8±0.9) and polyunsaturated fatty acid (PUFA) (302.3±3.8) were observed in fish fed CD/S, and the highest in fish fed DU2 and CD/B. Fatty acids 16:0 and 18:0, 18:1n‐9 and 16:1n‐7, and 22:6n‐3, 20:5n‐3, 22:5n‐3 and 18:2n‐6 were the dominant fatty acids amongst the saturates, monoenes and PUFA, respectively, and accounted for 80.8–88.7% of all identified fatty acids (23) in muscle of Murray cod. The study showed that Murray cod could be cultured successfully on a diet (DU2) containing 20% soybean meal without compromising growth and/or carcass quality. Differences in the proximate composition and fatty acid composition of muscle of wild and farmed Murray cod were observed, the most obvious being in the latter. Wild Murray cod had significantly less (P<0.05) saturates (192.6±1.84 vs. 266.3±3.51), monoenes (156.5±8.7 vs. 207.6±6.19), n‐3 (145.2±5.24 vs. 261.8±3.2) but higher n‐6 (144.3±2.73 vs. 48.3±1.38) in muscle (all values are in μg mg lipid^?1) than in farmed fish. Wild fish also had a much lower n‐3 to n‐6 ratio (1.0±0.03 vs. 5.4±0.09).     

Conjugated linoleic acid affects growth performance,hepatic fatty acid profile and lipid metabolism in juvenile Synechogobius hasta

This study was conducted to determine the effect of dietary CLA (Conjugated linoleic acid) levels on growth performance, fatty acid profiles and lipid metabolism of liver in Synechogobius hasta. Fish were fed six diets with fish oil replaced by 0 (control), 5, 10, 15, 20 and 25 g kg^?1 CLA for 8 weeks. Weight gain, WG, and SGR (specific growth rate) tended to increase when dietary CLA levels increased from 0 to 10 g kg^?1 and then decline with further increasing dietary CLA levels to 25 g kg^?1. FCR (feed conversion ratio) showed contrary trend with WG and SGR. The reduced VSI (vicero somatic index) and increased HSI (hepatosomatic index) were observed in fish fed increasing dietary CLA levels. Whole‐body lipid content declined, but hepatic lipid content increased with increasing dietary CLA levels. Dietary CLA modified total percentages of the main groups of fatty acids in liver. Hepatic 6PGD, ME and ICDH activities increased with increasing dietary CLA levels. FAS and G6PD were very variable and not related to dietary treatments. CPT I activities showed no significant differences among the treatments. Based on second‐order polynomial regression analysis of WG and FCR against dietary CLA level, 8.7–10.1 g kg^?1 was indicated to be the optimal dietary CLA range for maximum growth and feed utilization for S. hasta.     

Digestibility of energy,lipids and fatty acids of vegetable oils and poultry fat by pacu Piaractus mesopotamicus (Holmberg 1887)

Evaluation of vegetable oils and poultry fat digestibility is the first step to elicit their use in aquafeeds. This work aimed at determining apparent digestibility coefficients (ADCs) of energy, lipids and fatty acids of oil sources for pacu, a widely farmed neotropical Characin. A semipurified, omnivorous fish diet (344.2 g kg^?1 crude protein; 18.16 MJ kg^?1 gross energy) was used as reference diet. Test diets were obtained by adding 2 g kg^?1 chromium III oxide and replacing 15 g kg^?1 reference diet with fish, soybean, colza, corn and flaxseed oils and poultry fat. Juvenile pacu (64 ± 10.8 g; 14.6 ± 1.1 cm) were fed to apparent satiety, four times a day, and then transferred to cylindrical–conical aquaria for collection of faeces by sedimentation (n = 3). Apparent digestibility coefficients of energy and lipids were high for all tested oils (P > 0.05); ADCs of saturated fatty acid (SFA) were lower than monounsaturated fatty acids (MUFA) and polyunsaturated fatty acid (PUFA). Essential fatty acids (18:2n‐6 and 18:3n‐3) had high ADC (>93%), colza oil and poultry fat yielding the lowest ADC for 18:2n‐6 (P = 0.01) and 18:3n‐3 (P < 0.01), respectively. Corn oil, soybean oil and flaxseed oil were interesting sources of 18:2n‐6 and 18:3n‐3 dietary fatty acids for pacu.     

Dietary conjugated linoleic acid (CLA) for finishing Nile tilapia

A 8‐week feeding trial was conducted to evaluate the nutritional value of dietary conjugated linoleic acid (CLA) for finishing Nile tilapia evaluating its effects on growth performance, whole body and filet compositions, fatty acid composition, plasma lipid parameters, filet texture, liquid loss and holding capacity. Triplicate groups of Nile tilapia were hand‐fed until apparent satiation on diets in which CLA oil was supplemented at 0 (control), 5 or 10 g kg^?1. No differences were observed on weight gain, feed intake, feed/gain ratio, protein efficiency ratio, hepatosomatic index, visceral fat, filet yield and survival between treatments. Fish‐fed CLA diets had increased whole body crude protein and reduced filet lipid content. The total plasma cholesterol and triacylglycerol decreased with CLA supplementation. Neither 5 nor 10 g kg^?1 dietary CLA improved liquid‐holding capacity and filet texture when compared with fish fed the control diet. Fish‐fed dietary CLA showed lower whole body and filet C18:3(n‐6), C18:3(n‐3) and C20:2(n‐6) levels and higher levels of C18:0. CLA deposition in filet and whole body (16 mg–235 mg g^?1 of tissue) are higher than presented in natural sources of CLA, proving to be a great product to increase CLA consumption by humans.     

Alternative vegetable lipid sources in diets for grouper, Epinephelus coioides (Hamilton): effects on growth, and muscle and liver fatty acid composition

The aim of this study was to investigate the effects of different oils on growth performance and lipid metabolism of the grouper, Epinephelus coioides. Five experimental fish meal‐based isonitrogenous and isolipidic diets were formulated containing either 5.5%‐added fish oil (FO), soybean oil (SBO), corn oil (CO), sunflower oil (SFO) or peanut oil (PO). Each diet was fed to triplicate groups of 20 fish (initial body weight 13.2±0.02 g) grown in seawater at 28.0–30.5 °C for 8 weeks. Fish were fed twice a day to visual satiety. No significant differences in the survival, weight gain, specific growth rate, feed conversion ratio, protein efficiency ratio or hepatosomatic index were found between fish fed the FO or vegetable oils (VO) diets. Dietary lipid sources did not affect whole‐body composition among grouper fed the various diets. Muscle of fish fed the FO diet had significantly higher levels of 14:0, 16:0, 16:1n‐7, 20:5n‐3[eicosapentaenoic acid (EPA)] and docosahexaenoic acid (DHA)+EPA (except for PO fed fish) compared with those of fish fed VO diets. However, the levels of 18:1n‐9, 18:2n‐6 and DHA/EPA ratios in the muscle of fish fed FO diet were significantly lower than those of fish fed the VO diets. The liver of fish fed the FO diet had significantly higher levels of 18:0, 20:5n‐3, 22:6n‐3, n‐3 highly unsaturated fatty acids and DHA+EPA than those of fish fed the VO diets, whereas increases in 18:1n‐9, 18:2n‐6 and mono‐unsaturated fatty acid levels were observed in the liver of fish fed the VO diets.     

Combination effects of dietary EPA and DHA plus alpha‐tocopherol: effects on performance and physiological status of Caspian brown trout (Salmo trutta caspius) fry

The effects of dietary n‐3 highly unsaturated fatty acids [eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA)] with α‐tocopherol on growth, non‐specific immune response and oxidative status were investigated in Caspian brown trout, Salmo trutta caspius, fry. Six experimental diets containing three different dietary levels of n‐3 HUFAs (low: 1 + 0.5% of total fatty acids, DHA+ EPA, medium: 2 + 1%, DHA + EPA, high: 4 + 2%, DHA + EPA) with two different levels of α‐tocopherol (low: 300 and high: 1000 mg kg^?1 diet) were prepared and named: LL, LH, ML, MH, HL and HH (HUFA/α‐tocopherol) groups, respectively. Diets were fed to triplicate groups of 60 fry with an initial weight of 600 ± 25 mg for 10 weeks. Results showed that increase in dietary DHA and EPA up to high level improved fry growth in terms of the body weight and specific growth rate, particularly when dietary α‐tocopherol levels were high, suggesting a higher antioxidant protection value when these fatty acids are high. At all dietary n‐3 HUFA levels, increase in α‐tocopherol from low to high level enhanced the alternative complement (ACH50) activity. Fry fed diets medium and high n‐3 HUFA displaying significantly higher lysozyme activity (P < 0.05). Moreover, fish fed medium or high levels of n‐3 HUFA had significantly lower prostaglandin E2 (PGE2) than those fed low n‐3 HUFA (P < 0.05). Significant differences in antioxidant enzymes (catalase, glutathione peroxidase, glutathione S‐transferase, glutathione reductase and superoxide dismutase) activity were also observed between groups, with higher activity in high levels of n‐3 HUFA (P < 0.05). Results of this study suggest that the effect of dietary n‐3 HUFA on examined non‐specific immunity parameters are not uniform; however, these impacts are closely related to the α‐tocopherol supplement and their interaction. In conclusion, increased dietary levels of n‐3 HUFA and α‐tocopherol would enhance growth performance and welfare of this species.     

An evaluation of increasing linolenic acid level in the diet of Macrobrachium nipponense: Lipid deposition,fatty acid composition and expression of lipid metabolism‐related genes

To determine the effects of linolenic acid (LNA, 18:3n‐3) in oriental river prawn (Macrobrachium nipponense), an 8‐week feeding experiment was conducted using six isonitrogenous and isoenergetic semi‐purified diets containing 0.07 g/kg (control), 7.3 g/kg, 16.6 g/kg, 20.2 g/kg, 27.3 g/kg and 36.3 g/kg LNA. The hepatopancreas lipid content decreased significantly when dietary LNA content was >20.2 g/kg. Fatty acid analysis revealed that the percentage of 18:3n‐3 in the hepatopancreas significantly increased with increasing dietary LNA levels, while 20:5n‐3, 22:5n‐3 and 22:6n‐3 levels in the hepatopancreas decreased in a curvilinear manner as dietary LNA increased. Additionally, qRT‐PCR results revealed that hepatopancreas mRNA expression of acetyl‐CoA carboxylase (ACC) decreased with increasing dietary LNA, while the greatest carnitine palmitoyl transferase‐1(CPT1) mRNA expression was observed in the 2.73 g/kg and 36.3 g/kg groups. Furthermore, hepatopancreas mRNA expression of acyl‐CoA delta‐9 desaturase (SCD) and fatty acyl elongase 6(elovl6) was downregulated when prawns fed the diets containing >20.2 g/kg LNA. These results indicate that dietary 18:3n‐3 could decrease lipid deposition through increased fatty acid β‐oxidation and modulated fatty acid synthesis, and alter fatty acid composition by regulating fatty acyl elongase and fatty acyl desaturase mRNA expression in the M. nipponense.     

Deposition of conjugated linoleic acid in market size sea bass (Dicentrarchus labrax) and its effects on performance,composition and fillet sensory and texture attributes

The effect conjugated linoleic acid (CLA) accumulation in fish fillet on sensory and texture attributes has been evaluated. Fish were fed diets with graded levels of CLA, which were administered for different durations prior to harvest. Fish were sampled for fillet proximate composition and fatty acid profile for sensory and texture parameters at the end of the trial. Growth performance, feed conversion ratio and muscle proximate composition were not affected by dietary treatments. Muscle fatty acid profile was not affected by dietary treatments despite the increase in saturated fatty acids in fish fed diet with 10 g kg⁻¹ of CLA for 16 weeks before harvest. Besides, the deposition levels of CLA isomers increased gradually depending on the CLA treatment, reaching its maximum level in fish fed 10 g kg⁻¹ CLA diet for 20 weeks before harvest. Fish fed 10 g kg⁻¹ were juicier (P < 0.05) compared with control group, whereas fish fed 5 g kg⁻¹ CLA diet were less (P < 0.05) chewy than fish fed control diet regarding sensory attributes. Texture parameters were not significantly affected by dietary CLA. These results suggest that market size European sea bass could successfully incorporate CLA isomers with some minor positive effects on sensory analyses.     

Effect of dietary conjugated linoleic acid levels on growth performance,muscle fatty acid profile,hepatic intermediary metabolism and antioxidant responses in genetically improved farmed Tilapia strain of Nile tilapia Oreochromis niloticus

An 8‐week feeding trial was conducted to determine the effect of dietary conjugated linoleic acid (CLA) on growth performance, muscle fatty acid profile, hepatic intermediary metabolism and antioxidant responses in genetically improved farmed Tilapia (GIFT) strain of Oreochromis niloticus (initial body weight: 42.6 ± 0.4 g, mean ± standard deviation). Three replicated groups of GIFT strain of Nile tilapia were hand‐fed to satiation, twice a day, with the diets in which CLA oil, containing mainly the bioactive cis‐9, trans‐11 and trans‐10, cis‐12 isomers, was included at 0 (control), 0.5%, 1%, 1.5%, 2% and 2.5%, respectively, at the expense of fish oil to maintain the constant lipid and energy levels. Growth performance and feed utilization showed no significant differences among the treatments (P > 0.05). The dietary inclusion of CLA modified total percentages of the main groups of fatty acids. Increasing saturated fatty acid content and reduced mono‐unsaturated fatty acid contents in muscle were observed with increasing dietary CLA inclusion (P < 0.05). Total n‐3 fatty acids and total polyunsaturated fatty acids tended to decline with increasing dietary CLA levels (P < 0.05), but n‐6 fatty acids showed no significant differences among the treatments (P > 0.05). Dietary CLA supplementation resulted in the significant increase in the trans‐10, cis‐12 and cis‐9, trans‐11 CLA isomers in muscle (P < 0.05) and also significantly influenced several hepatic enzymatic activities, such as succinate dehydrogenase, lactate dehydrogenase, malic dehydrogenase, lipoprotein lipase and hepatic lipase activities (P < 0.05). Reduced superoxide dismutase and glutathione peroxidase activities, and the decline in malondialdehyde levels were observed in fish fed the CLA‐supplemented diets (P < 0.05), indicating that dietary CLA supplementation showed a powerful antioxidant effect for this fish species. Our study was the first report involved in the effect of dietary CLA inclusion on hepatic intermediary metabolism and antioxidant responses in fish, which could be used as indicators of nutritional and physiological status of the fish species.     

Nutritional evaluation of fatty acids for the open thelycum shrimp, Litopenaeus vannamei: I. Effect of dietary linoleic and linolenic acids at different concentrations and ratios on juvenile shrimp growth, survival and fatty acid composition

A 6‐week feeding trial was conducted to evaluate the nutritional value of dietary linoleic (18:2n‐6, LOA) and linolenic (18:3n‐3, LNA) acids for juvenile Litopenaeus vannamei by determining their effects on growth, survival and fatty acid composition of hepatopancreas and muscle tissue. Diets were formulated to contain 5% total lipid. A basal diet contained only palmitic and stearic acids, each at 2.5% of diet. Six diets contained one of three levels (0.25, 0.5 and 1%) of either LOA or LNA, and three diets had different ratios of LNA/LOA (1, 3, 9) at a combined inclusion level of 0.5% of diet. An additional diet contained 0.5% of a mixture of n‐3 highly unsaturated fatty acids (HUFA). The fatty acid profile of hepatopancreas and muscle of shrimp reflected the profile of the diets. HUFA of the n‐3 family showed higher nutritional value than LOA or LNA for juvenile L. vannamei by producing significantly (P < 0.05) higher final weight and weight gain. Neither LOA nor LNA, alone or in combination, improved growth significantly compared with shrimp fed the basal diet.Thus, dietary requirements for LOA and LNA were not demonstrated under these experimental conditions.     

Effects of oxidized fish oil intake on tissue lipid metabolism and fatty acid composition of channel catfish (Ictalurus punctatus)

Recent studies in terrestrial animals have shown that feeding the oxidized lipids led to a reduction in triacylglycerols (TAG) and total cholesterol (TC) in liver and plasma. However, limited information is available on the effect of oxidized lipids on lipid metabolism in fish. In this study, four diets containing 0 g kg^?1 (control: fresh fish oil), 30 g kg^?1 (low‐oxidized oil, LOO), 60 g kg^?1 (medium‐oxidized oil, MOO) and 90 g kg^?1 (high‐oxidized oil, HOO) graded oxidized oil levels with the same dietary lipid level were fed to channel catfish for 86 days. The tissue lipid metabolism and fatty acid composition of the fish were investigated after this period. The results showed that plasma and liver concentrations of TAG and TC decreased with increasing dietary oxidized oil level (P < 0.05). Decreasing liver lipoprotein lipase and hepatic lipase activities were observed with increasing dietary oxidized fish oil inclusion (P < 0.05). The liver C22:6n?3 concentrations significantly decreased with increasing dietary oxidized oil level (P < 0.05), while muscle lipid had a high proportion of polyunsaturated fatty acids. It suggests that the adverse effects of dietary oxidized oil may be induced by inhibiting lipid metabolism enzymes and, consequently, inhibition of cholesterol homoeostasis and fatty acid synthesis.     

Effects of dietary n‐3 PUFA supplements on composition of n‐3 PUFA and expression of fatty acid elongase 5 (AJELOVL5) in sea cucumber,Apostichopus japonicus

This is the first comprehensive study on the effect of dietary polyunsaturated fatty acid (PUFA) levels on the expression of fatty acid elongase 5 (AJELOVL5), PUFA composition, and growth in juvenile sea cucumbers. The specific growth rate (SGR_w) was improved in n‐3 PUFA‐rich diets compared to low n‐3 PUFA diets. AJELOVL5 expression was apparently upregulated in juveniles fed lower PUFA diets relative to higher PUFA diets, with higher expression in the body wall and respiratory tree of juveniles fed diets without ɑ‐linolenic acid (ALA, 18:3n‐3) compared to juveniles fed higher ALA level diets; similar results were also detected in juveniles fed diets with lower eicosapentaenoic acid (EPA, 20:5n‐3), docosahexaenoic acid (DHA, 22:6n‐3), and none of ALA, EPA, or DHA respectively. The concentrations of ALA, EPA, and DHA in tissues were positively related to the content of dietary corresponding PUFA, with higher ALA content in juveniles fed diet ALA_12.71 than in the ALA_7.46 and ALA₀ groups. Similar results were also obtained in sea cucumber fed diets enriched with either EPA or DHA. Interestingly, considerable levels of EPA and DHA were found in the tissues of juveniles fed diets of CK₀ and DHA₀, with no specific input of EPA or DHA, showing that the sea cucumber was capable of biosynthesizing EPA and DHA from their corresponding precursors as ALA and linoleic acid (LA, 18:2n‐6).     

Dietary α‐linolenic acid affects lipid metabolism and tissue fatty acid profile and induces apoptosis in intraperitoneal adipose tissue of juvenile grass carp (Ctenopharyngodon idella)

A 56‐day feeding trial was conducted to elucidate the effects and mechanism action of dietary α‐linolenic acid (ALA, 18:3n‐3) on lipid accumulation and fatty acid profile of muscle, hepatopancreas and intraperitoneal fat (IPF) in juvenile grass carp using three isonitrogenous and isoenergetic semi‐purified diets containing 0.0% (control group), 1.0% and 2.0% ALA, respectively. The lowest intraperitoneal fat (IPF) ratio was found in 2.0% group. In the muscle, hepatopancreas and IPF, docosahexaenoic acid (DHA, 22:6n‐3) and eicosapentaenoic acid (EPA, 20:5n‐3) contents increased with the increase in dietary ALA. In the IPF, caspase 3, caspase 8 and caspase 9 showed the highest activities in 2.0% group, while the value of Bcl‐2/Bax (B‐cell leukaemia 2/Bcl‐2‐associated X protein) reached the lowest. Meanwhile, swelling of the IPF mitochondria was observed in 2.0% group. The gene expressions of fatty acid desaturase (FAD) and fatty acid elongase (ELO) in the hepatopancreas and muscle showed significantly higher levels in the treatment groups, whereas an opposite trend was existed in the IPF. Fatty acid synthase (FAS), sterol regulatory element binding protein‐1c (SREBP‐1c) in the IPF and hepatopancreas reached the lowest in 2.0% group. Overall, dietary ALA could promote n‐3 highly unsaturated fatty acids (HUFAs) synthesis and suppress the accumulation of lipid by decreasing the expression of related genes and promoting the apoptosis in IPF.     

Restoration of the fatty acid composition of red seabream (Pagrus auratus) using a fish oil finishing diet after grow-out on plant oil based diets

This study evaluated the potential for manipulating the fatty acid composition of juvenile red seabream, Pagrus auratus. Prior to the start of the study, three groups of fish had been reared for 3 months on a fish oil based diet or diets where the added fish oil had been replaced with either canola or soybean oil. In the present study, fish that had previously been fed either the canola or soybean oil diets were fed a fish oil based diet. Three additional treatments included fish being maintained on their original diets of fish oil, canola oil or soybean oil. Fish were fed their respective diets twice daily to apparent satiety for 32 days. Samples of fish from each treatment were collected after 0, 1, 2, 4, 8, 16 and 32 days. Composition and growth of the fish were determined at each sample point. Most treatments showed no differences in growth performance, although fish fed a fish oil diet after previously being fed a soybean oil diet showed slightly better growth. No significant differences among treatments were observed in proximate composition of the fish, although there was a significant increase in total fat and individual fatty acid (g kg^?1 live‐weight) content of the fish from all treatments over the period of the study. No significant changes in the relative fatty acid composition (% of total fatty acids) over time were observed in the three treatments where fish were maintained on their original diets. In contrast, fish that were previously fed either the canola or soybean oil diets and were then fed a fish oil diet had significant changes in both the relative (% of total fatty acids) and absolute (g kg^?1 live‐weight) fatty acid content. Key changes observed included a decrease in the relative levels of polyunsaturated fatty acids (PUFA) such as 18 : 2n ? 6 and 18 : 3n ? 3. Increases in the relative levels of the long‐chain polyunsaturated fatty acids (lcPUFA) 20 : 5n ? 3 and 22 : 6n ? 3 were also observed in both treatments. The rates of absolute (g kg^?1 live‐weight) change/accumulation of these fatty acids followed an exponential equation that differed for each fatty acid in each treatment. Examination of the retention efficiency of specific fatty acids also showed marked differences between fatty acids within treatments and also differences between treatments. Biologically important fatty acids such as 20 : 5n ? 3 and 22 : 6n ? 3 had only moderate retention efficiencies and these were unaffected by treatment. In contrast, the retention efficiencies of 18 : 2n ? 6 and 18 : 3n ? 3 suggested selective retention of these fatty acids when fed fish oil diets, but moderate catabolism when fed the plant oil diets. There were also high retention efficiencies of most saturated and monounsaturated fatty acids suggestive of active retention and/or active synthesis of these fatty acids by the fish. The results of this study, particularly the increases in lcPUFA, support the usefulness of a fish oil based finisher diet for fish raised predominantly on plant oil based diets.     

Replacement of fish oil with vegetable oil blends in feeds for greater amberjack (Seriola dumerili) juveniles: Effect on growth performance,feed efficiency,tissue fatty acid composition and flesh nutritional value

This study was undertaken to assess the effects of fish oil (FO) substitution by a mixture of alternative vegetable oils (VO) on Seriola dumerili culture performance. A 154‐day feeding experiment was conducted using juveniles (39.2 ± 1.6 g average weight). Three isolipidic and isoenergetic meal‐based diets were formulated varying their lipid component. The control diet contained 100% FO (FO100), whereas diets VO50 and VO100 included 1/2 of oil blend and all the oil from blend of palm oil (PO) and linseed oil (LO) as substitute for FO, respectively. Dietary regime did not significantly affect growth performance, biometric indices, feed efficiency, plasma chemistry and liver and muscle lipid contents. Nonetheless, dietary VO inclusion impacted on the fatty acid profile of target tissues, especially in the liver. Fatty acid profiles of the fillets reflected those of the dietary oils except that there was apparent selective utilization of palmitic acid (C16:0) and oleic acid (C18:1n‐9) and apparent selective retention of long‐chain polyunsaturated fatty acids, especially eicosapentaenoic acid (EPA, C20:5n‐3) and docosahexaenoic acid (DHA, C22:6n‐3). The nutritional value and the potential ability to prevent the development of coronary heart diseases of the flesh lipid fraction decreased with gradual FO substitution.     

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

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

Fatty acid composition and analysis of freshwater caridean shrimp Macrobrachium nipponense (De Haan) during spermiogenesis

We analysed fatty acids (FAs) composition and the potential functions of FAs in hepatopancreas and testis of freshwater caridean shrimp Macrobrachium nipponense during testis development. The hepatopancreas presented a high unsaturated FA content of about 40%, whereas the testis showed a high level of saturated fatty acids (SFAs) with a decreasing content of 97–86% of total FAs during maturation. Several specific FAs in testis showed significant changes throughout maturation. Among SFAs, C14:0 contributed with a relatively constant high proportion of about 22%, whereas C16:0 and C18:0 contents were also at high levels but showed significant increases during maturation. Representatives of highly unsaturated fatty acids (HUFAs), such as C18:1n‐9, C18:2n‐6, C20:5n‐3 (EPA), C20:4n‐6 (AA) and C22:6n‐3 (DHA) showed significant increases despite their low proportion in the gonad. These results suggest that a high content of HUFAs in hepatopancreas may represent a reservoir for sperm production. The FA C14:0 may provide a particular function. The variations of the FA profile in testis at different developmental stages reveals that C18:1n‐9, C18:2n‐6, C20:5n‐3, C20:4n‐6 and C22:6n‐3 may play important roles in spermiogenesis.