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1.
Together with docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), arachidonic acid (ARA) is being considered to be an essential fatty acid in marine fish larval diets. The objective of the present study was to determine the importance of dietary ARA levels for larval European sea bass performance, when EPA and DHA are also present in the diet. Eighteen‐day‐old larvae were fed, for 14 days, gelatine‐based microdiets containing the following ARA levels: 0.3%, 0.6% or 1.2%. Elevation of dietary ARA up to 1.2% showed a positive correlation with larval survival and a significant improvement in the specific growth rates, body weight and total length. Arachidonic acid was efficiently incorporated into larval lipids, even at a higher proportion than that in the diets. Increased accumulation of ARA did not affect the incorporation of DHA or EPA from the diet into larval total lipids. A significant positive correlation was found between dietary ARA levels and survival after handling stress, indicating the importance of this fatty acid in sea bass larvae response to acute stressors. The results show the importance of ARA for sea bass larvae, but higher dietary levels should be tested to determine whether there is a negative effect of ARA in sea bass as reported for other species.  相似文献   

2.
Mangrove red snapper fed advanced broodstock diets containing squid meal and squid oil exhibited higher hatching rates, cumulative survival and survival activity index than those fed a basal diet or a basal diet supplemented with mixture of antioxidants. On the other hand, fatty acid analyses of ovaries and fry of wild fish and eggs and larvae of broodstock fed raw fish revealed high arachidonic acid (ARA) and docosahexaenoic acid (DHA) levels and relatively lower eicosapentaenoic acid (EPA) levels consequently showing high ARA/EPA and DHA/EPA ratios compared to cold water species. This suggests that ARA may be nutritionally more important for egg and larval development and survival in tropical marine fish and its supplementation in broodstock diets may enhance reproductive performance of mangrove red snapper.  相似文献   

3.
The effect of different arachidonic acid (ARA) dietary contents at several dietary eicosapentaenoic acid (EPA) levels on the growth, survival and biochemical composition of gilthead seabream larvae was studied to better define the importance of this fatty acid as a function of EPA. Larvae of 18 days were fed one of the five isonitrogenous and isolipidic microdiets with three different EPA (0.3%, 2% and 4%) and ARA amounts (0.1%, 0.6% and 1.2%). Although a dietary increase in either ARA or EPA alone did not improve survival significantly, the increase in both fatty acids significantly enhanced growth and survival, suggesting an optimum dietary value of EPA:ARA close to 4:1.2. Dietary ARA was more efficiently incorporated into larval tissues than EPA. Increased dietary EPA or ARA contents reduced the incorporation of ARA or EPA into larval lipids, indicating their competition as substrates for different enzymes. The possible negative effect of further elevation of dietary ARA and its competition with EPA for phospholipids synthesis deserves further studies in marine fish larvae.  相似文献   

4.
In previous studies, combined inclusion of Zn, Mn and Se in early weaning diets improved larval growth, but suggested a potential toxicity by one of these elements. The present study aimed to determine the effect of the single inclusion of Zn, Mn, Se or Cu, their combination (Control+) or their absence (Control?) on larval diets. At the end of the trial, survival was significantly (p < .05) lowest in fish fed C+ diet (17.16 ± 7% mean ± SD), followed by that of larvae fed Mn diet (21.91 ± 7%). The highest survival was obtained by Cu diet (35.27 ± 15%), followed by C? diet (34.58 ± 9%). Cu and Se supplementation significantly improved total length and body weight, in comparison with the C? fish. On the contrary, fish fed Mn and C+ showed the lowest growth. Supplementation with Zn or Cu significantly increased CuZnsod, whereas gpx was significantly upregulated in fish fed Se and C+ diets. ARA/EPA level was significantly highest and DHA/EPA lowest in larvae fed the Cu diet in fish fed C+ diet. The results pointed out the importance of supplementation with Cu, as well as Se and Zn, on early weaning diets for gilthead sea bream, and the potential toxic effect of Mn.  相似文献   

5.
The recent decreasing worldwide supplies of marine oils have forced the aquaculture industry to investigate alternative lipid sources for use in marine fish feeds. The aim of this study was to determine the impact of dietary replacement of fish oil by vegetable oils on gilthead seabream (Sparus aurata) growth performance, nutritive utilization, body composition, and fatty acid profile as well as feed cost. Two dietary vegetable oil (VO) mix blends (VO1 and VO2) in which: sunflower (SO), cottonseed (CO) and linseed (LO) for VO1 or soybean oil (SBO) for VO2, were tested as 60% fish oil (FO) substitutes versus the 100% FO control or reference diet (FO). Three iso-proteic (46% CP) and iso-lipidic (18%) experimental diets were hand fed, twice a day, 6 days a week to apparent visual satiety to triplicate groups of seabream growers (average initial weight, 130.9 ± 3.44 g), until fish reached market size (300–400 g/fish) after 20 weeks at mean ambient temperature 27.0 ± 1.8°C. All experimental diets were well accepted by seabream growers regardless of the different lipid sources used, as overall mean feed intake (FI) and daily intake (DFI) were not significantly different (P > 0.05) among dietary treatments. In terms of growth performance, fish fed VO1 diet (with LO) exhibited a relatively lower, but significant (P < 0.05), total weight gain (WG) than fish fed all FO diet (FO). However, mean value of WG of fish fed either vegetable oil-tested diet was nonsignificantly different. Feeding seabream growers vegetable oil (VO) diets (VO1 or VO2) had no significant effect on specific growth rate (SGR), daily weight index (DWI), or feed conversion ratio (FCR) among dietary treatments. Consumption of VO for 20 weeks did not significantly alter the major nutrient composition of fish, but the muscle fatty acid (FA) profile was significantly altered compared to the reference FO diet. Comparatively reduced levels of eicosapentaenoic acid (EPA) and docosahexaenoic acids (DHA), as well as elevated levels of linoleic and linolenic acids (LA and LNA) compared with fish fed the FO were noticed. In terms of economics, 17 or 20% reduction in Kg feed cost was obtained for diets VO1 or VO2, respectively. In terms of growth performance and cost, VO2 diet showed slight relative superiority over VO1 diet. However, in terms of liver structure morphology, VO1 diet (with LO) has resulted in less fat-infiltration and altered hepatic cells than VO2 (with SBO). As these traits do not affect yield or the price paid for the fish, VO2 diet has therefore been considered better than VO1 as complementary lipid sources for gilthead seabream grower diets.  相似文献   

6.
Cultivated Atlantic cod (Gadus morhua) entering their first year of gamete maturation were fed diets with different levels of arachidonic acid (ARA) and eicosapentaenoic acid (EPA) for 6.5 months prior to commencement of spawning. Gravid females were stripped three times: at the beginning, peak and end of spawning. Lipid composition and egg and larval quality of 34 family crosses were investigated. Results indicated that ARA uptake into eggs from broodstock diet was highly efficient achieving proportions of ARA up to 84% higher in eggs than in the diet. EPA was 42–76% higher, and DHA was 155–173% higher in eggs than in diets. Cod fed the diet with the lowest EPA/ARA ratio had the greatest egg production. Eggs from fish on a diet with high ARA level had significantly higher fertilization and hatching success than those fed low levels of ARA. This diet produced on average 71 viable eggs g?1 female compared with 32.5 and 4 eggs in diet B and C, respectively. Furthermore, larval survival until 8 days posthatch was higher in diets with lower ARA levels. The combined results showed that ARA dietary supplementation and low EPA/ARA ratio yielded a greater number of viable larvae kg?1 female.  相似文献   

7.
The Δ6 and Δ5 desaturases and elongases show only very limited activity in marine fish, and little is known of the possibility of enhancing Δ6 desaturase gene expression in these fish. The use of plant oils in marine fish diets is limited by their lack of n−3 highly unsaturated fatty acids (HUFA) despite an abundant content of the 18C fatty acid precursor linoleic and α-linolenic acids. The objective of the present study was to determine the ability of larval gilthead seabream to utilize vegetable oils and assess the nutritional regulation of Δ6 desaturase gene expression. Seventeen-day-old gilthead seabream larvae were fed during a 17-day period with one of four different microdiets formulated with either sardine fish oil (FO), soybean, rapeseed or linseed oils, respectively, or a fifth diet containing defatted squid meal and linseed oil. Good larval survival and growth, both in terms of total length and body weight, were obtained by feeding the larvae either rapeseed, soybean or linseed oils. The presence of vegetable oils in the diet increased the levels of 20:2n−9 and 20:2n−6, 18:2n−9, 18:3n−6, 20:3n−6 and 20:4n−6, in larvae fed rapeseed and soybean oils in comparison to those fed FO. In addition, a sixfold increase in the relative expression of Δ6 desaturase-like gene was found in larvae fed rapeseed and soybean oils, denoting the nutritional regulation of desaturase activity through its gene expression in this fish species. However, feeding linseed oil did not increase the expression of the Δ6 desaturase gene to such a high extent.  相似文献   

8.
The aim of this study was to evaluate the long‐term effects (7‐month experiment) of diets consisting of fish oil (Kilka fish) and vegetable oil (rapeseed) on the reproductive performance of sterlet sturgeon (Acipenser ruthenus) broodstock. Forty‐five broodstock (990.3 ± 20.05 g) were randomly allocated to three different diet treatments. Three experimental diets were formulated with graded levels of fish oil (100% FO), vegetable oil (100% VO), and a combination of fish and vegetable oil (50% FO + 50% VO). At the end of the 7‐month feeding trial period, the weight gain and final weight were changed significantly different between the treatments (p < 0.05). Broodstock fed the FO + VO diet had higher growth than those fed the only FO or VO diets (p < 0.05). The highest germinal vesicle migration percentage was observed in FO + VO treatment (p < 0.05). The DHA/EPA, DHA/ARA and EPA/ARA ratios in oocyte exhibited a significant difference in the different treatments (p < 0.05). This study indicates that nutrition of broodstock with diet including FO + VO (p < 0.05) can positively affect the growth performance of larvae compared with only FO or VO diets. Furthermore, the high levels of 18:1n‐9, AL and ALA contents in oocytes from broodstock fed VO and the lowest ALA content in oocytes from broodstock fed FO underlined the important role of broodstock diets in the reproductive process and embryonic and/or larval developments of sterlet.  相似文献   

9.
Sea urchin eggs and larvae have been suggested as potential live prey for marine fish larval feeding. This study evaluated the fatty acid composition of Paracentrotus lividus eggs, prisms and four-armed plutei, obtained from wild and captive broodstocks fed on raw diets: maize, seaweed and a combination of maize and seaweed. Amounts of essential fatty acids (EFA) for marine fish larvae [arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA)] were determined in eggs and endotrophic larvae. ARA ranged from 3.93% in eggs from combination to 18.7% in plutei from maize diets. In any developmental stage, EPA amounts were always lower than 5% for the raw diets, and DHA showed null or trace amounts including the wild diet. Thus, broodstock-prepared diets had to be formulated based on different lipid sources (Algamac, linseed oil, cod liver oil and olive oil) in order to test eggs and larvae EFA enhancement. EFA improvement was possible for all tested prepared diets. Algamac diet lead to superior EFA enhancement mainly in DHA (7.24%, 4.92% and 6.09% for eggs, prisms and plutei, respectively) followed by cod liver oil diet. Only these two lipid sources should be considered for prepared broodstock diets in order to obtain suitable live prey for fish larval feeding.  相似文献   

10.
The concept of nutritional programming raises the interesting possibility of directing specific metabolic pathways or functions in juvenile fish, for example, to improve the use of substitutes to fishmeal and oil, and hence to promote sustainability in aquaculture. The aim of the study was to determine effects of early nutritional stimuli of gilthead seabream larvae and check if nutritional programming of gilthead sea bream is possible between 16 days post hatching (dph) and 26 dph. A trial was conducted to determine the effects of early nutritional stimuli of gilthead seabream larvae. Five experimental microdiets (pellet size <250 μm) were formulated containing five different proportions of a marine lipid source rich in long‐chain polyunsaturated fatty acids (LC‐PUFA) and two vegetable lipid sources rich in linolenic and linoleic acids. The results of this study demonstrate that dietary n‐3 LC‐PUFA levels increased larval growth and survival affecting Δ6 desaturase gen (fads2) expression and retinal neurons density. However, the high mortalities obtained along on‐growing in fish fed low n‐3 LC‐PUFA at 16 dph constrained the feasibility of nutritional programming of gilthead seabream during this late developmental window and needs to be further investigated.  相似文献   

11.
The success of microdiets commonly used in the cultivation of marine fish larvae is limited to serving as partial replacements for live food. This limited success is thought to be associated with a reduced digestive ability due to an incompletely developed digestive system. The enhanced growth obtained from live food has been partially attributed to the digestive enzyme activity of the food organism. The present study was designed to test the effect of an exogenous digestive enzyme incorporated. into a microdiet on the growth of Sparus aurata. Larval gilthead seabream, 20–32 days old, were fed 14C labelled microdiets containing a commercial pancreatic enzyme at different concentrations (0, 0.1 and 0.05g / 100 g dry diet). Rates of ingestion and assimilation were measured and their relationship to dry weight was determined. Our results show that the success of the microdiet as a food for larval gilthead seabream was limited by the larva's low ingestion rate which only approached its maintenance requirement. In addition, the presence of digestive enzyme in the microdiet enhanced its assimilability by 30%. Larval growth over ten days was 0, 100 and 200% on microdiet free of added enzymes, one with added enzymes and a live food regime, respectively. It is our opinion that successful development of microdiets for Sparus aurata must be based on diets improved both in digestibility and attraction to the larvae. Further studies are now underway to determine the nutritional requirements of gilthead seabream larvae using the experimental method developed in the present study. This research was carried out in partial fulfillment of the requirements for the M.Sc. degree.  相似文献   

12.
The use of non‐marine arachidonic acid (ArA) and docosahexaenoic acid (DHA) as highly unsaturated fatty acid (HUFA) enrichments was evaluated as complete replacements for marine fish oil in practical diets formulated with solvent‐extracted soybean meal (SESM). Litopenaeus vannamei juveniles (0.59 g) were reared over 84 days in an outdoor tank system with no water discharge. Fishmeal was replaced with SESM, while fish oil was replaced with HUFA‐rich algal cells, alternative oil and/or fermentation products. Spray‐dried Schizochytrium algal cells (Schizomeal‐Hi DHA) served as the DHA enrichment source. Oil extracted from Mortierella sp. was used as the ArA enrichment (AquaGrow® ArA). DHA and ArA sources (Advanced BioNutrition Corp., Columbia, MD, USA) were non‐marine products obtained from a commercial supplier. Five diets were formulated with ArA inclusion levels of 0, 0.65, 1.3, 2.6 and 5.2 g kg?1. In addition, one diet was formulated to be DHA deficient and another was formulated with menhaden fish oil (control). Different inclusion levels of non‐marine ArA had no effect on survival or growth. Shrimp fed the non‐marine HUFA‐supplemented diets had lower average weight compared to shrimp offered the diet containing fish oil. No differences were detected in average weights of shrimp offered the ArA‐deficient and ArA‐supplemented diets.  相似文献   

13.
Due to its traditionally good availability, digestibility and high content of n ? 3 HUFA, fish oil is the main lipid source in fish feeds. However, world demand for this product has grown significantly in recent years, whereas its production, based on fisheries landings, is static. The purpose of the present study was to assess the effect of partial replacement of fish oil in compound diets for gilthead seabream and seabass, by several vegetable oil sources, on growth, dietary fatty acid utilization and flesh quality. Five iso‐energetic and isoproteic experimental diets were formulated (25% lipid content). Fish oil was the only added lipid source in the control (FO) diet, and it was included in the other experimental diets at a level high enough (40% of FO diet) to keep the n ? 3 HUFA levels well over 3% in order to cover the essential fatty acid requirements of these species. Fish oil was replaced by soyabean oil (SO), rapeseed oil (RO) and linseed oil (LO) or a mixture (Mix) of them. Feed intake in all dietary groups was in the range of results obtained for commercial diets in both species, and growth and feed utilization were very good. The results show that, providing a minimum content of essential fatty acids in the diet, it is possible to replace up to 60% of the fish oil by SO, LO and RO or a mixture of them in diets for seabream and seabass, without compromising fish growth. Fatty acid composition of liver and muscle reflected that of the diet, but utilization of dietary lipids differed between these two tissues and was also different for the different fatty acids. Despite reduction in dietary saturated fatty acids by the inclusion of vegetable oils, their levels in fish liver were as high as in fish fed the fish oil diet, whereas, in muscle, levels were reduced according to that in the diet. Linoleic and linolenic acids were accumulated in the liver proportionally to their levels in the diet, suggesting a lower oxidation of these fatty acids in comparison to other 18C fatty acids. Regarding eicosapentaenoic acid (20 : 5n ? 3; EPA), docosahexaenoic acid (22 : 6n ? 3; DHA) and arachidonic acid (20 : 4n ? 6; ARA), these essential fatty acids were reduced in the liver at a similar rate, whereas DHA was preferentially retained in the muscle in comparison with the other fatty acids, denoting a higher oxidation particularly of EPA, in the muscle. Some other PUFA increased despite their low dietary levels in seabream fed LO diets and in seabass fed SO diet, suggesting the stimulation of delta‐6 and delta‐5 desaturase activity in marine fish. Despite differences in fatty acid composition, fillet of fish fed vegetable oils was very well accepted by trained judges when assessed cooked.  相似文献   

14.
A feeding experiment was conducted to develop non‐fish meal and non‐fish oil diet for red seabream by using plant protein source and Schizochytrium meal which is rich in 22:6n‐3 (DHA). Three iso‐nitrogenous and iso‐lipidic experimental diets were prepared (CP 41.2% ± 0.4%, CL 16.4% ± 1%). Control diet contained both fish meal (40%) and fish oil (6%). In the second diet, fish meal was replaced by plant meals (soy protein concentrate, soybean meal, corn gluten meal) [FO]. In the third diet, fish meal and fish oil were replaced by algae meal (Schizochytrium sp. powder) and plant proteins [AO]. Duplicated groups of juvenile red seabream (8.8 g ± 1.5) were fed the experimental diets for 12 weeks to near satiation. There was no statistical difference among treatment in specific growth rate. Feed conversion ratio of AO diet group was higher than that of control. In wet basis, whole body protein level was significantly higher in AO diet than FO group while lipid content was lower than control group. In fatty acid profile, AO group had significantly lower 18:4n‐3, 20:4n‐3, 22:5n‐3 and 20:5n‐3 (EPA) level, but significantly higher 18:3n‐3 and DHA level than the other two diet fed fish. The results might suggest that further developments in microalgae diet offer a promising lipid source of n‐3 PUFA as essential fatty acid on marine fish. And it showed possibility to develop non‐fish meal and non‐fish oil feed for marine aquaculture fish by using microalgae.  相似文献   

15.
The nutritional requirements of pikeperch larvae have been sparsely examined. Dietary polyunsaturated fatty acids, arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may affect growth and physiological stress response in marine fish larvae, but these mechanisms have not received as much attention in freshwater fish. Pikeperch larvae were reared on Artemia from day 3 until 21 days posthatch. Artemia were enriched with six formulated emulsions, with inclusion of either fish oil, pure olive oil (POO) or olive oil supplemented with various combinations of ARA, EPA and DHA. Larval tissue FA was significantly related to the content in the diets, but larval growth was similar for all treatments. When exposed to stress by confinement in small tanks with culture tank water or saline water (15 g L?1.), mortality in larvae treated with POO was significantly higher than in the remaining treatments while tissue cortisol contents in these fish seemed lower. The findings of a lower stress response in larvae fed POO may be related to the lower tissue content in these larvae of essential fatty acids especially DHA but also EPA and ARA.  相似文献   

16.
The importance of dietary 20:5n‐3 (EPA), 22:6n‐3 (DHA) and 20:4n‐6 (ARA) for growth, survival and fatty acid composition of juvenile cockles (Cerastoderma edule) was investigated. Cockles of 6.24 ± 0.04 mm and 66.14 ± 0.34 mg (live weight) were distributed into three treatments where live microalgae diets were fed constantly below the pseudofaeces production threshold, for three weeks. Diets had distinct fatty acid profiles: high EPA (53% Chaetoceros muelleri + 47% Pyramimonas parkeae), no DHA (47% Brachiomonas submarina + 53% Tetraselmis suecica) and low ARA concentrations (73% P. parkeae + 27% Phaeodactylum tricornutum). Growth was positively affected by high EPA and low ARA diets, whereas no significant growth was observed for the no DHA diet. High mortality of cockles fed no DHA diet raises questions about its suitability for cockles. In balanced diets with EPA and DHA, lower concentrations of ARA do not limit growth. The impact of dietary fatty acids was evident in the fatty acids of neutral and polar lipids of cockles. In polar lipids of all cockles, there was a decrease in EPA, in contrast to an increase in DHA. The combination of EPA and DHA in a live microalgae diet was beneficial for the growth and survival of juvenile cockles.  相似文献   

17.
This study is the first attempt to condition broodstock Babylonia areolata using formulated diets under hatchery conditions. Samples of spotted babylon egg capsules from broodstock fed either a formulated diet or a local trash fish, carangid fish (Seleroides leptolepis) for 120 days were analyzed for proximate composition and fatty acid composition. The formulated diet contained significantly higher levels of arachidonic acid (20:4n − 6; ARA), eicosapentaenoic acid (20:5n − 3; EPA) and docosahexaenoic acid (22:6n − 3; DHA) than those of the local trash fish. The formulated diet also had significantly higher ratios of DHA/EPA and (n − 3)/(n − 6) PUFA than those of local trash fish but not for the ARA/EPA ratio. The compositions of egg capsules produced from broodstock fed formulated diet contained significantly more ARA, EPA and DHA compared to broodstock fed the local trash fish. The ARA/EPA and DHA/EPA ratios in egg capsules were significantly higher in the trash fish—fed group compared to those fed the formulated diet. However, (n − 3)/(n − 6) PUFA ratios in egg capsules produced from broodstock fed the formulated diet did not differ significantly compared to those from broodstock fed the local trash fish. The relatively low DHA/EPA, ARA/EPA and (n − 3)/(n − 6) ratios in the egg capsules produced from the formulated diet—fed broodstock B. areolata suggested that this diet is inferior, when compared to the traditional food of trash fish.  相似文献   

18.
The present study tested the effect of dietary lecithin and exogenous lipase on the incorporation of oleic acid in the tissue lipids of gilthead seabream larvae (Sparus aurata). Two of four microdiets were prepared by the addition of [14C]oleic acid as free fatty acid (FFA) to diets containing either 5% cuttlefish liver oil (CLO) or 5% soybean lecithin. Glycerol tri[1-14C]oleate was similarly incorporated in two other diets identical in lipid (4% cuttlefish liver oil, 1% soybean lecithin) and non-lipid composition but differed in that one contained a supplement of 0.05% porcine lipase. The effect of these diets was tested by following the incorporation of the label (dpm/mg larvae DBW) in the neutral and phospholipid fractions of seabream larvae at four different ages (21, 27, 32 and 45 days after hatching).A significant (p<0.05) effect of dietary lecithin on the incorporation of labelled FFA in both larval neutral and phospholipid fractions was demonstrated at all ages. This was particularly pronounced during early development (day 21) where fish fed the lecithin supplement incorporated 6.75 times more label than the diet containing [14C]oleic acid in CLO. The dietary lecithin enhancing effect diminished with age but was still significant at day 45 (2.17 times more label). In addition, the label was considerably higher in the phospholipid fraction compared to the neutral lipid, reflecting the high demand for membrane synthesis during rapid growth. Lecithin fed larvae demonstrated a higher consumption rate and efficiency of incorporation than fish consuming the cuttlefish liver oil diet, suggesting an emulsifying function for dietary phospholipid.In contrast, the supplementation with lipase showed a clear effect only in older fish where 45 day old larvae fed the lipase diet demonstrated a 3.42 times increase in radioactivity in their tissue lipids. This late lipase response may be the result of an insufficient level of dietary lecithin (M) and a short intestinal length being ineffective, in the early larval stages, in incorporating labelled free fatty acid from dietary glycerol tri[1-14C]oleate breakdown.  相似文献   

19.
Five experimental diets containing different lipid sources, fish oil (D1), soybean lecithin (D2), corn oil (D3), canola oil (D4) and olive oil (D5), were evaluated in Atractosteus tropicus larvae for the relative gene expression of the enzymes fatty acid synthase (fas), acetyl‐CoA carboxylase 1 (acc1) and carnitine palmitoyltransferase 1C (cpt1c), in addition to their effects on larval growth, survival and cannibalism during a 30‐day feeding trial. Higher growth and survival were obtained in treatments D1 and D2, and lower performance in diets D3, D4 and D5. The highest levels of expression of fas and acc1 occurred in larvae fed with D1, which contained high amounts of n‐3 long‐chain polyunsaturated fatty acids (LC‐PUFA), mainly DHA and EPA FA are regulators of lipogenesis. The higher cpt1c expression in plant‐based diets is attributed to the fact that these diets are rich in α‐linolenic acid (ALA) and low DHA, EPA and ARA levels that favour ß‐oxidation. In conclusion, the diets with fish oil (D1) and soybean lecithin (D2) were the best treatments for larval growth, survival and cannibalism and thus appear to meet both lipid and energy requirements of A. tropicus larvae, meanwhile the use of vegetable oils influences the expression of intermediary lipogenic genes.  相似文献   

20.
A study with varying dietary inclusion levels (1, 5, 10, 15 and 20 g kg?1) of docosahexaenoic acid (DHA; 22:6n-3) was conducted with post-smolt (111 ± 2.6 g; mean ± S.) Atlantic salmon (Salmo salar) over a 9-week period. In addition to the series of DHA inclusion levels, the study included further diets that had DHA at 10 g kg?1 in combination with either eicosapentaenoic acid (EPA; 20:5n-3) or arachidonic acid (ARA; 20:4n-6), both also included at 10 g kg?1. An additional treatment with both EPA and DHA included at 5 g kg?1 (total of 10 g kg?1 long-chain polyunsaturated fatty acids, LC-PUFA) was also included. After a 9-week feeding period, fish were weighed, and carcass, blood and tissue samples collected. A minor improvement in growth was seen with increasing inclusion of DHA. However, the addition of EPA further improved growth response while addition of ARA had no effect on growth. As with most lipid studies, the fatty acid composition of the whole body lipids generally reflected that of the diets. However, there were notable exceptions to this, and these implicate some interactions among the different LC-PUFA in terms of the fatty acid biochemistry in this species. At very low inclusion levels, DHA retention was substantially higher (~250 %) than that at all other inclusion levels (31–58 %). The inclusion of EPA in the diet also had a positive effect on the retention efficiency of DHA. However, EPA retention was highly variable and at low DHA inclusion levels there was a net loss of EPA as this fatty acid was most likely elongated to produce DHA, consistent with increased DHA retention with additional EPA in the diet. Retention of DPA (22:5n-3) was high at low levels of DHA, but diminished with increasing DHA inclusion, similar to that seen with DHA retention. The addition of EPA to the diet resulted in a substantial increase in the efficiency of DPA retention; the inclusion of ARA had the opposite effect. Retention of ARA was unaffected by DHA inclusion, but the addition of either EPA or ARA to the diet resulted in a substantial reduction in the efficiency of ARA retention. No effects of dietary treatment were noted on the retention of either linolenic (18:3n-3) or linoleic (18:2n-6) acids. When the total n-3 LC-PUFA content of the diet was the same but consisted of either DHA alone or as a combination of EPA plus DHA, the performance effects were similar.  相似文献   

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