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1.
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2.
A 90‐day feeding trial was carried out to examine the influence of fish oil (FO) substitution with blends of vegetable oils (VOs) on reproductive efficiency of female brooders and fluctuation in fatty acid (FA) profile of embryos in Oncorhynchus mykiss. A basal diet was formulated in which 20% (80FO/20VO), 50% (50FO/50VO), 75% (25FO/75VO) and 100% (100VO) of FO were replaced by mixture of VO. Reproductive performance of brooders was not affected by drastic alternations in FA profile of diets. The level of saturated and monounsaturated FAs (MUFAs) significantly increased, whereas the levels of long‐chain polyunsaturated FAs (LC‐PUFAs), mainly docosahexaenoic acid, profoundly decreased during embryogenesis. The concentrations of MUFA and n?6 PUFA increased in the eggs with increasing the incorporation of VO mixture in diets; however, the concentration of LC‐PUFA and n?3/n?6 PUFA ratio decreased. Haematological parameters and humoral immune responses including total immunoglobulin content, lysozyme and alternative complement pathway activities in brooders fed with the experimental diets did not statically different. In summary, incorporating mixture of various VO sources especially linseed and sunflower oils as good sources of α‐linolenic and linoleic acids, respectively, along with low levels of residual fat from fish meal in diet suggested a good strategy for providing the appropriate essential FA requirements of O. mykiss brooders for their successful reproduction.  相似文献   

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4.
This study aimed to test the hypothesis that the efficiency of a finishing period can be improved by reducing the initial fat content of fish fillets, by means of a period of food deprivation. Two groups of rainbow trout (Oncorhynchus mykiss) were fed for an 18‐week grow‐out period on a vegetable oil‐based diet (VO) or a fish oil‐based diet (FO). VO fed fish were then split into two sub groups: one (VO/FO) was shifted to the FO diet for 8 weeks, whilst the other (UF/FO) was deprived of food (unfed) for 2 weeks and then fed the FO diet for the remaining 6 weeks. The control treatment (FO/FO) was represented by fish continuously fed FO. The subsequent reduction of total fat in the UF/FO treatment was then responsible for a much faster recovery towards a FO‐like fatty acid profile, validating the proposed hypothesis. However, the modification of the fatty acid composition of fish fillets during the feed withholding period, coupled with the postponement of the finishing diet, resulted in only minor beneficial effects of this strategy, and the loss of potential weight gain. However, the n‐3 LC‐PUFA content in UF/VO fish fillets was significantly higher than fish subjected to the VO/FO treatment.  相似文献   

5.
The silver barb (Barbonymus gonionotus) is a valuable cyprinid with good deposition of long‐chain polyunsaturated fatty acids (LC‐PUFA) such as docosahexaenoic acid (DHA). We have previously isolated a fatty acyl desaturase (Fads2) and elongase (Elovl5), which fulfils the production of eicosapentaenoic acid (EPA) and arachidonic acid (ARA) from C18 polyunsaturated fatty acid (PUFA) substrates. The isolation, functional characterization and dietary regulation of two elongases, Elovl2 and Elovl4, are reported here. The Elovl2 displayed the capacity to elongate C20 and C22 PUFA substrates, while the showed low activities towards saturated fatty acids and C22 PUFA substrates. This discovery validates the existence of a complete set of enzymes of LC‐PUFA in silver barb. The elovl2 showed higher expression in liver, in limited dietary LC‐PUFA intake conditions. As for Elovl4, tissue expression showed prominence in eye tissue. We also showed that the expression of both genes was upregulated when fish was fed with diets devoid of LC‐PUFA. Fatty acid composition analysis indicates the utilization of C18 polyunsaturated fatty acids for LC‐PUFA biosynthesis.  相似文献   

6.
The objective of this study was to determine the major nutrient limiting growth and lipid metabolism in African catfish fed diets composed of vegetable ingredients. Four diets were formulated from contrasted meal (fish meal: FM; vegetable meal: VM) and oil (fish oil: FO; vegetable oil: VO) sources. Replacement of FO by VO did not affect specific growth rate (SGR) and feed efficiency, whereas lower values were recorded in the case of FM replacement. LC‐PUFAs muscle contents were higher in fish fed control FMFO diet than in fish fed vegetable ingredients. However, the decrease in docosahexaenoic acid (DHA) concentration in FMVO group was limited compared to VM groups despite the same low DHA level in those three diets. These results may suggest an activation of LC‐PUFA biosynthesis from PUFA precursors brought with vegetable oils in FMVO group. This hypothesize is reinforced by the significant stimulation of elovl5 gene expression in liver and intestine from fish fed FMVO. Therefore, this study demonstrated that African catfish is able to bioconvert LC‐PUFAs at a significant biological level when FO is replaced by VO whereas the use of plant proteins has strong detrimental effects on growth performances.  相似文献   

7.
Enchytraeus albidus is a small euryhaline earthworm that is abundant in the supralittoral zone where it can be found in decaying seaweed. This species is readily mass‐cultured, and due to its relatively high contents of protein and polyunsaturated fatty acids (PUFAs), there has been a renewed interest in this species as an alternative source of valuable nutrients for fish feed. Here, we have investigated the influence of substrate salinity (0, 1, 2, 8, 15, 30 and 40 ppt) on reproduction, growth and nutrient content of worms. We found that intermediate salinities (8–15 ppt) of the substrate maximize biomass production as well as protein and PUFA contents of the worm tissue. In particular, we observed that the often used culturing of E. albidus in non‐saline growth medium resulted in low reproduction and biomass production. Increasing the salinity from 0 to 15 ppt resulted in a higher proportion of unsaturated fatty acids both in storage lipid and in membrane phospholipid fractions.  相似文献   

8.
This study aimed to evaluate the vitellogenic transference and incorporation of long‐chain polyunsaturated fatty acids (LC‐PUFA) into the membranes of Prochilodus lineatus embryos, aiming to increase the permeability to cryoprotectants and resistance to electric fields. One hundred thirty broodstock of P. lineatus were fed with control (C) or fish oil‐supplemented diets (FO) for 12 months. The fatty acid (FA) profle was determined using gas chromatography. For the neutral fraction, the FO group had a decrease in monounsaturated fatty acids (MUFA) and an increase in n3PUFA and, n6PUFA. To test for cryoprotectant toxicity, embryos were exposed for 20 min to a cryoprotectant solution of 1,2‐Propanediol (Prop) at a concentration of 5 or 6 molar (M). For FO, a reduction in survival of 33.1% was observed in 5 M, and no survival was observed at 6 M. Embryo samples were exposed the six polarized electric fields (3.4–51.6 joules), and with 11.2 J of energy, the control group exhibited reduced survival in 98.3% of the fish, whereas the FO presented superior resistance, exhibiting a survival similar to that of the OJ up to 40.2 J. We conclude that FA were transferred between P. lineatus broodstock to the embryos, with an increase in LC‐PUFA resulting in lower survival rates in the cryoprotectant test in the FO group and a greater physical plasticity of FO embryos to electrical field tests.  相似文献   

9.
This study was undertaken to evaluate the effect of dietary lipid source [linseed oil (LO, rich in 18:3 n?3); corn oil (CO, rich in 18:2 n?6); olive oil (OO, rich in 18:1n?9); and fish oil (FO, rich in LC‐PUFA)] and level (9% L and 18% L) on growth, body composition and selected plasma biochemistry parameters in hybrid catfish (Pseudoplatystoma reticulatum × Leiarius marmoratus) juveniles. Moreover, liver histology (lipids, glycogen, cell vacuolization) and key metabolic enzyme activities were also evaluated. After 8 weeks of feeding, there were no differences in growth performance and whole‐body composition between groups. Plasma lipoprotein, muscle and liver composition, and G6PD and ME activity were affected by lipid level and source. No differences were observed between groups in hepatic ALT activity; however, AST activity was lower in fish fed the 9% L diets. Overall, liver and muscle fatty acid composition reflected that of diet FA composition, with increased n3/n6 ratio, high HUFA and low MUFA in fish fed FO compared with the VO diets. Higher liver glycogen content was observed in fish fed the 18% L than the 9% L diets, except for fish fed FO diet. Considering the experimental diets used, these results indicate that hybrid catfish can efficiently utilize VO supplementation as an energy source, without affecting growth performance and fillet composition.  相似文献   

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11.
Although a stenohaline freshwater fish, the stinging catfish Heteropneustes fossilis, is also available in the freshwater fringes of the coastal areas of Bangladesh, the tolerance of this species to variable environmental salinity has not been thoroughly investigated. Based on median lethal salinity (MLS‐50 96 h), three sublethal salinity levels (3 ppt, 6 ppt and 9 ppt) and a control (0 ppt), each with three replications were selected to observe the effects of mildly brackish conditions on the fish for a period of 90‐day exposure. Better growth and survival were found up to 6 ppt compared with control. Salinity more than 6 ppt appeared unsuitable for H. fossilis fingerling due to increased mortality and reduced growth. To determine biochemical alterations, a few important physiological parameters were observed after 90 days of exposure. Glycogen level of liver and muscle in the fish reared at 9 ppt salinity decreased significantly (P < 0.05) as compared to the control. Glucose level in blood and liver was also found to be increased in fish with increase in salinity. ALP and ATPase activities were reduced significantly in both muscle and liver tissues at higher salinity, indicating the stress mitigation effect. However, all the biochemical parameters were found in normal condition up to 6 ppt compared with control. This evidence suggests that H. fossilis can sustain and grow well below 6 ppt and can be a potential candidate for culture in coastal areas after heavy downpour when the salinities level falls to 6 ppt or lower.  相似文献   

12.
To investigate the feasibility of total replacement of dietary fish oil (FO) with vegetable oils (VOs) and the optimal dietary polyunsaturated fatty acid (PUFA) level in the marine herbivorous teleost Siganus canaliculatus, six isonitrogenous (32%) and isolipidic (8%) diets were formulated. Control diet used FO as lipid source, whereas diets VO1–VO5 contained various blends of palm, soybean, rapeseed, and linseed oils, in which the dietary PUFA levels were 42.0, 38.2, 33.8, 29.9, and 27.1%, respectively. After S. canaliculatus juveniles were fed with the diets for 9 wk, their growth performance exhibited no significant difference among the dietary groups. The tissue fatty acid (FA) profiles in liver and fillet generally reflected the dietary FA compositions and showed no significant difference among the VO dietary groups. The results suggest that dietary FO can be replaced completely by VO, without affecting their growth performance. Concerning the effects of the dietary FA profile on the survival rate, hepatosomatic index and viscerosomatic index, and PUFA composition in fillets, diets VO1 and VO2 were more favorable compared with diets VO3–VO5. Considering the availability and cost of the VOs, diet VO2 was recommended for practical use in S. canaliculatus.  相似文献   

13.
Failing to initiate first feeding during the transition from endogenous nutrition to exogenous feeding will lead to starvation of fish larvae. However, little is known about the mechanism of first feeding selection of fish. Golden mandarin fish larvae (3 d after hatch, 2.05 ± 0.03 mg) were fed with four different foods for 7 d, including the following: M – Megalobrama amblycephala (prey fish larvae as natural food); S – surimi of M. amblycephala; A – Artemia (zooplankton); and MA –mixed M. amblycephala with Artemia (mixed food). Larvae fed with the mixed food achieved an appropriate balance between high survival and good growth through elevating the expression of growth genes (GH, IGF‐I, and IGF‐II) and fatty acid synthesis genes (FAD and ELO). Growth performance of fish fed with MA reared at different salinities (0, 5, and 10 ppt) was examined. The salinity of 5 ppt produced the best growth performance of the three salinity levels tested. Fish larvae adapted to high‐ or low‐salinity environments through increasing the expression of lipolysis genes (HSL, LPL, and HL). Therefore, both food type and salinity affect the growth, survival, and lipometabolism of golden mandarin fish larvae during initial feeding stage, and mixed food and 5 ppt salinity improved its survival and growth.  相似文献   

14.
Fish oil (FO) substitution has been studied in many marine carnivorous fish, but seldom in marine herbivorous or omnivorous species. To evaluate the feasibility of using soybean oil (SO) as a dietary lipid and confirm its capability of converting C18 polyunsaturated fatty acid (PUFA) into long chain polyunsaturated fatty acid (LC‐PUFA) in the marine herbivorous teleost Siganus canaliculatus, juvenile fish were fed with four formulated diets differing in lipid composition, with SO accounting for 0.76% (SO0), 23% (SO23), 45% (SO45) and 67% (SO67) of total dietary lipid respectively. After feeding for 8 weeks, growth performance including weight gain, specific growth rate, feed conversion ratio and protein efficiency rate were better in the SO23 and, especially, SO45 groups than in the SO0 and SO67 groups (P < 0.05). Tissue fatty acid compositions were affected by diet, with the liver contents of eicosapentaenoic (EPA), docosapentaenoic (DPA), docosahexaenoic (DHA) acids and total n‐3 PUFA displaying parallel changes with the corresponding dietary fatty acids. While the muscle contents of EPA, DPA and total n‐3 PUFA between SO0 and SO23 groups, and the liver contents of arachidonic acid (ARA) and 20:4n‐3, as well as the muscle content of 20:3n‐6 between SO0 and SO45 groups showed no difference, confirming the biosynthesis of LC‐PUFA from C18 precursors in vivo as the contents of corresponding fatty acids in diets SO23/SO45 were much lower than those in diet SO0 (P < 0.05). The results indicate that SO may be a suitable dietary lipid source for S. canaliculatus, and can replace up to 67% or 45% of total dietary FO without negatively compromising growth performance or nutritional quality of fish respectively. Moreover, the study increases our knowledge of FO substitution in marine herbivorous fish.  相似文献   

15.
We studied the effects of dietary n‐3 LC‐PUFAs on the activities and mRNA expression levels of tissue lipoprotein lipase (LPL) and fatty acid synthase (FAS) during vitellogenesis and ovarian fatty acid composition in female silver pomfret broodstock. Broodstock were fed one of four experimental diets for 185 days: FO (100% fish oil), FSO (70% fish oil + 30% soybean oil), SFO (30% fish oil + 70% soybean oil) or SO (100% soybean oil). The results revealed that hepatic LPL and FAS and ovarian FAS activities and mRNA expression levels significantly increased at vitellogenesis and postvitellogenesis relative to previtellogenesis, with no significant differences between these two stages, except for hepatic LPL mRNA expression. Dietary n‐3 LC‐PUFAs decreased tissue FAS and increased LPL activities and mRNA expression levels. The ovarian concentrations of 20:4n‐6 (ARA), 20:5n‐3 (EPA), 22:6n‐3 (DHA) and n‐3 LC‐PUFAs were directly influenced by n‐3 LC‐PUFA levels. Total n‐3 LC‐PUFA concentrations in SO were 57% lower than those in FO, while 18:2n‐6 concentrations in SO were 4.7 ×  higher than those in FO. These results revealed that high dietary n‐3 LC‐PUFAs levels significantly affected tissue lipid metabolism in female silver pomfret broodstock during vitellogenesis by upregulating LPL and downregulating FAS.  相似文献   

16.
This study investigated effects of linseed or fish oil–enriched finishing diets on the polyunsaturated fatty acids (PUFA) composition in dorsal muscle tissues of pond‐cultured common carp (Cyprinus carpio). After 180 days of dietary exposure to cereal diet containing vegetable oil (1%), carp were exposed to 7% linseed (LO) or 7% fish oil–enriched (FO) finishing diets for 30 days. FO supplied 17 and 20 mg fish?1 day?1, respectively, of the long‐chain n‐3 fatty acids eicosapentaenoic and docosahexaenoic acid for 30 days and doubled long‐chain PUFA concentrations in carp of the FO pond. The increased supply of short‐chain PUFA in LO resulted in higher short chain, but not long‐chain PUFA, showing that there was very little PUFA conversion. Thus, dietary short‐chain PUFA could not compensate for the low levels of dietary long‐chain PUFA in LO. However, moderate supply of dietary long‐chain PUFA in finishing diets for 30 days is very efficient in increasing nutritionally important long‐chain PUFA concentrations in carp.  相似文献   

17.
The aim of this study was to evaluate the growth and survival of pacu, Piaractus mesopotamicus, larvae reared in different salinities and to determine the Artemia nauplii life span in freshwater and in saline water. First feeding 5‐d‐old pacu larvae were reared in freshwater or at 2, 4, 6, 8, 10, 12, and 14 ppt salinities. The larvae were reared in 1.5‐L aquaria at a density of 10 larvae/L with three replicates per treatment. After 10 d of rearing, significant differences (P < 0.05) were observed for growth and survival. Larval growth was higher at 2 and 4 ppt, and survival at 2 ppt was 100%. In freshwater and at 4, 6 and 8 ppt, the survival was 91.1, 93.3, 73.3, and 39.9%, respectively. At higher salinities, there was 100% mortality after 2 h (12 and 14 ppt) and 8 h (10 ppt) of exposure. The slightly saline water of at least 2 ppt increased the Artemia nauplii life span compared to the life span in freshwater. Later, in a second trial, 5‐d‐old pacu larvae were reared in freshwater and at 2 and 4 ppt salinities during the first 5 or 10 d of active feeding, and then the fish were transferred to freshwater. At the end of 15 d, larval growth was lower in freshwater (42 mg) than in treatments 2 and 4 ppt (59–63 mg). The abrupt transfer of fish from freshwater to slightly saline water and the return to freshwater did not affect the survival rates (89–97%). The larvae were able to adapt to these saline environments and handle abrupt changes in salt concentration. We concluded that salinity concentration of 2 ppt can be used for pacu larval rearing, allowing the Artemia nauplii lifetime to last longer and cause faster fish growth.  相似文献   

18.
Changes in fatty acid metabolism in Atlantic salmon (Salmo salar) induced by vegetable oil (VO) replacement of fish oil (FO) and high dietary oil in aquaculture diets can have negative impacts on the nutritional quality of the product for the human consumer, including altered flesh fatty acid composition and lipid content. A dietary trial was designed to investigate the twin problems of FO replacement and high energy diets in salmon throughout the entire production cycle. Salmon were grown from first feeding to around 2 kg on diets in which FO was completely replaced by a 1:1 blend of linseed and rapeseed oils at low (14–17%) and high (25–35%) dietary oil levels. This paper reports specifically on the influence of diet on various aspects of fatty acid metabolism. Fatty acid compositions of liver, intestinal tissue and gill were altered by the diets with increased proportions of C18 polyunsaturated fatty acids and decreased proportions of n-3 highly unsaturated fatty acids (HUFA) in fish fed VO compared to fish fed FO. HUFA synthesis in hepatocytes and enterocytes was significantly higher in fish fed VO, whereas β-oxidation was unaltered by either dietary oil content or type. Over the entire production cycle, HUFA synthesis in hepatocytes showed a decreasing trend with age interrupted by a large peak in activity at seawater transfer. Gill cell prostaglandin (PG) production showed a possible seasonal trend, with peak activities in winter and low activities in summer and at seawater transfer. PG production in seawater was lower in fish fed the high oil diets with the lowest PG production generally observed in fish fed high VO. The changes in fatty acid metabolism induced by high dietary oil and VO replacement contribute to altered flesh lipid content and fatty acid compositions, and so merit continued investigation to minimize any negative impacts that sustainable, environmentally-friendly and cost-effective aquaculture diets could have in the future. Abbreviations: FO - fish oil; HUFA - highly unsaturated fatty acids acids (carbon chain length ≥C 20 with ≥3 double bonds); LO - linseed oil; RO - rapeseed oil; VO - vegetable oil. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

19.
The physiological responses of Senegalese sole to a sudden salinity change were investigated. The fish were first acclimated to an initial salinity of 37.5?ppt for 4?h. Then, one group was subjected to increased salinity (55?ppt) while another group was subjected to decreased salinity (5?ppt). The third group (control group) remained at 37.5?ppt. We measured the oxygen consumption rate, osmoregulatory (plasma osmolality, gill and kidney Na+,K+-ATPase activities) and stress (plasma cortisol and metabolites) parameters 0.5 and 3?h after transfer. Oxygen consumption at both salinities was higher than for the control at both sampling times. Gill Na+,K+-ATPase activity was significantly higher for the 55?ppt salinity at 0.5?h. Plasma osmolality decreased in the fish exposed to 5?ppt at the two sampling times but no changes were detected for high salinities. Plasma cortisol levels significantly increased at both salinities, although these values declined in the low-salinity group 3?h after transfer. Plasma glucose at 5?ppt salinity did not vary significantly at 0.5?h but decreased at 3?h, while lactate increased for both treatments at the first sampling time and returned to the control levels at 3?h. Overall, the physiological response of S. senegalensis was immediate and involved a rise in oxygen consumption and plasma cortisol values as well as greater metabolite mobilization at both salinities.  相似文献   

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