Cottonseed oil as a complementary lipid source in diets for gilthead seabream Sparus aurata juveniles

The efficacy of using cottonseed oil (CSO) as a fish oil (FO) substitute in gilthead seabream (Sparus aurata) juveniles feed was evaluated. Fish (BW_i 4.0 ± 2.9 g) were fed one of four isoproteic (~48% CP) and isolipidic (~18% L) diets for 9 weeks. Added oil was either FO (control diet, CTRL) or CSO, replacing 50% (CSO50 diet), 60% (CSO60 diet) and 70% (CSO70 diet) of dietary FO. Results indicated that FO replacement by CSO up to 60% level had no detrimental effects on growth or nutritive utilization and composition in fish muscles. Higher CSO intake (CSO70 diet, 56 g kg^?1) led to a 16% reduction in weight gain, 14% in feed utilization (FCR) and 57% in muscle n‐3 long‐chain polyunsaturated fatty acids (lc PUFA) as compared with CTRL and to abundant accumulation of lipid within the hepatocytes. Use of CSO altered fatty acid (FA) profiles of muscle and liver. Data suggested utilization of linoleic acid (LOA) by fish and retain of docosahexaenoic acid (DHA) in muscles. Therefore, limits of CSO inclusion as the main source of supplementary dietary lipid, with no negative effects on fish performance or nutritive composition and utilization in muscles, are: 40–48 g kg^?1 feed for gilthead seabream juveniles.     

Debaryomyces hansenii L2‐enriched diet enhances the immunity status,gene expression and intestine functionality in gilthead seabream (Sparus aurata L.)

This study evaluates the effects of the dietary administration of the live yeast Debaryomyces hansenii strain L2 on the immune responses of gilthead seabream for 4 weeks. Cellular immune parameters were measured from serum and head‐kidney leucocytes respectively. The expression levels of immune‐associated genes were quantified by real‐time polymerase chain reaction. In addition, the profile of intestinal microbiota was studied by denaturing gradient gel electrophoresis. The results showed that seabream fed a diet containing D. hansenii had significantly increased cellular immune parameters. The yeast‐supplemented diet up‐regulated the expression of most seabream genes at week 2 and down‐regulated all of them at week 4, except in the head‐kidney. Finally, a reduction in the diversity of the intestinal microbiota was detected in those specimens receiving the yeast‐supplemented diet. These results support the idea that the live yeast D. hansenii strain L2 stimulates the immune system of gilthead seabream.     

Plant protein and vegetable oil‐based diets modulate gilthead seabream (Sparus aurata) muscle biochemical status and proteolytic enzymes at an early postmortem stage

A 70 days feeding trial was carried out on juvenile gilthead seabream (Sparus aurata) (mean initial body weight: 362 ± 59 g) to evaluate whether the simultaneous replacement of fishmeal and fish oil by vegetable ingredients affected the muscle's proteolytic potential. Fish were fed either a fishmeal/fish oil diet, a fishmeal/vegetable oil diet, a plant protein/fish oil or a plant protein/vegetable oil diet. The use of dietary plant proteins resulted in lower sulphated glycosaminoglycans' content and lower glycogen phosphorylase activity in the muscle, while both plant proteins and vegetable oil increased muscle pH and reduced cathepsin B activity. Our results indicate that high replacement of fish meal and/or fish oil with plant ingredients has a significant impact on early postmortem metabolic processes and proteolytic potential of seabream muscle, especially when replacing both fish meal and fish oil.     

Apparent digestibility of nutrients in grass carp (Ctenopharyngodon idellus) diet supplemented with graded levels of neutral phytase using pretreatment and spraying methods

The effects of supplemental graded levels of neutral phytase using pretreatment and spraying methods on the apparent digestibility coefficients (ADCs) of protein, minerals and amino acids were investigated in grass carp (Ctenopharyngodon idellus) (mean weight, 20.92 ± 1.04 g). Seven experimental diets were prepared as: no‐phytase supplementation (control), pretreatment with phytase dose of 500 U (PP500), 1000 U (PP1000) and 1500 U (PP1500) per kg diet. With spraying method, the phytase was added to feed at the same three grades, namely 500 U (PS500), 1000 U (PS1000) and 1500 U (PS1500) per kg diet. After an 8‐week feeding trial, addition of phytase improved the crude protein, crude lipid, dry matter, ash, phosphorus and calcium digestibilities in comparison with the control, especially in the diets where phytase addition level was above 1000 U kg^?1 (P < 0.05). Phytase supplementation, both the pretreatment and spraying, significantly enhanced the ADCs of essential amino acid (EAA) and non‐essential amino acid. The ADCs of the nutrients were significantly influenced by phytase supplementation methods, supplementation levels and interaction of methods and levels. Based on the results, supplemental dietary phytase, regardless of application methodology, improved the ADCs of nutrients in grass carp, and the pretreatment mode of phytase application was more effective than spraying at the same phytase level. We suggest that the optimal level of phytase pretreatment is 1000 U kg^?1 diet, and the best addition level of phytase spraying is 1500 U kg^?1 diet or more phytase is required for spraying.     

Partial replacement of fish meal by soybean meal with or without methionine and phytase supplement in diets for juvenile Chinese sucker,Myxocyprinus asiaticus

This study was designed to evaluate the effects of using soybean meal supplemented with or without methionine (M) and graded levels of phytase (P) to replace high‐level (60%) fish meal in the diets for juvenile Chinese sucker. Seven experimental diets (about 430 g kg^?1 crude protein on dry matter basis) were formulated from practical ingredients. The control diet (FM) was formulated to contain 400 g kg^?1 white fish meal (FM), whereas in the other six diets (diets 2–7), soybean meal (SBM) was used to replace 60% fish meal with or without methionine (3 g kg ^?1) and 0,500, 1000, 1500 and 2000 U kg^?1 phytase (designated as SBM, SM, SMP500, SMP1000, SMP1500 and SMP2000, respectively). Results from the feeding trial indicated that SBM without any methionine or phytase supplement replacing about 60% FM significantly affected the growth of fish (P < 0.05). Weight gain of fish fed diet SM was significantly higher than the fish fed diet SBM, but still much lower than fish fed the control diet (P < 0.05). SBM with methionine and phytase supplement significantly improved the growth of fish and apparent digestibility coefficients of phosphorus compared with the groups which fed diet SBM and diet SM (P < 0.05). Weight gain of fish fed SMP1000, SMP1500 and SMP2000 had no significant difference than fish fed control diet. Furthermore, fish fed SMP1500 showed optimum weight gain and ADC of phosphorus between these three groups. This suggested that soybean meal with 3 g kg^?1 methionine and 1500 U kg^?1 phytase supplement could successfully replace 60% fish meal in the diet for juvenile Chinese sucker without affecting growth and enhanced the apparent digestibility coefficient of phosphorus.     

Interference of Listonella anguillarum with potential probiotic microorganisms isolated from farmed gilthead seabream (Sparus aurata, L.)

Four isolates obtained from gilthead seabream have been tested for their adhesion to the skin, gill and intestinal mucus of gilthead seabream, and for their ability to interfere with Listonella anguillarum, an important pathogen of farmed gilthead seabream. The ability to adhere to mucus was higher than 7% for all isolates. Three isolates showed an antagonistic effect against some of the pathogenic strains tested. They were assayed to interfere with the attachment of L. anguillarum to the mucus of gilthead seabream. Only two isolates significantly reduced the adhesion of L. anguillarum to all of the mucus assayed under exclusion, competition and displacement conditions. According to the criteria applied, the isolate Pdp11 was selected and its in vivo probiotic potential was assessed by oral administration followed by challenge with the pathogen L. anguillarum. For the feeding trial, a group of 50 gilthead seabreams received a commercial diet supplemented with lyophilized 10⁸ CFU g^?1 of this isolate for 15 days. An other group of similar characteristics received the non‐supplemented commercial diet. After the challenge, the mortality of the fish receiving the diet supplemented with the potential probiotic was significantly lower than that observed in the groups of fish receiving the non‐supplemented commercial diet.     

Nutritional stimuli of gilthead seabream (Sparus aurata) larvae by dietary fatty acids: effects on larval performance,gene expression and neurogenesis

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.     

Fish oil replacement by different microalgal products in microdiets for early weaning of gilthead sea bream (Sparus aurata,L.)

The aim of this study was to determine if algal products rich in DHA or ARA are able to completely replace fish oil in microdiets for marine fish larvae, gilthead seabream and if extra supplementation with EPA may further enhance larval performance. For that purpose, 20 day‐old gilthead seabream larvae of 5.97 ± 0.4 mm mean total length and 0.12 ± 0.001 mg mean dry body weight were fed with five microdiets tested by triplicate: a control diet based on sardine oil; a diet containing AquaGrow^® DHA (diet DHA) to completely substitute the sardine oil; a diet containing AquaGrow^® ARA (diet ARA); a diet containing both products, AquaGrow^® DHA and AquaGrow^® ARA to completely substitute the fish oil; and, a diet containing both products, AquaGrow^® DHA and AquaGrow^® ARA, together with an EPA source. Temperature, air and salinity activity tests were also performed to detect larval resistance to stress. At the end of the experiment, final survivals did not differ among groups. The microorganism produced DHA was able to completely replace fish oil in weaning diets for gilthead seabream without affecting survival, growth or stress resistance, whereas the inclusion of microorganism produced ARA did not improve larval performance. Moreover, addition of EPA to diets with total replacement of fish oil by microorganism produced DHA and ARA, significantly improved growth in terms of body weight and total length. The results of this study denoted the good nutritional value of microorganisms produced DHA as a replacement of fish oil in weaning diets for gilthead seabream, without a complementary addition of ARA. However, dietary supplementation of EPA seems to be necessary to further promote larval performance.     

In vitro and in vivo antifungal activity of Satureja cuneifolia ten essential oil on Saprolegnia parasitica strains isolated from rainbow trout (Oncorhynchus mykiss,Walbaum) eggs

In the present study, the chemical composition and the antifungal properties against Saprolegnia parasitica (in vitro and in vivo) of the essential oils of thyme (Satureja cuneifolia) from Mediterranean region of Turkey were evaluated for the first time. The composition of oils was analysed using gas chromatography/mass spectrometry (GC/MS). The major constituents of oil of S. cuneifolia were cavracrol (46,84%) and cymene (16.90%). Antifungal effects of S. cuneifolia essential oil against S. parasitica strains (A1 and E1) were detected by disc diffusion and tube dilution assays. The antifungal effect of S. cuneifolia was determined to be stronger against S. parasitica E1 isolate (MIC 50 μL mL^?1, MLC 250 μL mL^?1) compared with S. parasitica A1 isolate (MIC 50 μL mL^?1, MLC 500 μL mL^?1). Following in vitro assays, effective doses of S. cuneifolia for disease control in rainbow trout eggs experimentally infected with S. parasitica were investigated. For this aim, infected eggs were treated with the essential oil (0, 5, 10, 20 and 50 ppm) during incubation period (21 days) after fertilization. Formalin (5 mL L^?1) was used as positive control. Hatching rate of eggs at the end of incubation period were calculated. The highest hatching rates were recorded in S. parasitica E1 strain at 5 and 10 ppm concentrations of S. cuneifolia and in S. parasitica A1 strain at 10 and 20 ppm (P < 0.05).     

Stress assessment,quality indicators and shelf life of three aquaculture important marine fish,in relation to harvest practices,water temperature and slaughter method

The objective of this study was to evaluate the effect of harvest practices and slaughter method on stress, quality and shelf life of whole fish (gilthead sea bream, European sea bass and red sea bream) towards the development of a humane slaughter practice. The use of hook and line resulted in significantly lower plasma cortisol and glucose in European sea bass and gilthead sea bream. Water temperature at harvest affected significantly the concentrations of stress indicators (plasma cortisol and glucose), mainly in European sea bass and gilthead sea bream. No significant differences were observed between the harvesting methods, regarding fish appearance, microbial spoilage and sensory scoring and subsequently shelf life. However, significantly lower hardness was recorded in fish harvested using the electric stunner, compared to the fish killed with slurry ice of the same harvesting period. Shelf life ranged between 13–18 days for gilthead seabream, 10–16 days for European sea bass and 10–14 days for red sea bream, depending on harvesting period.     

Dietary lipid sources for seabream and seabass: growth performance, tissue composition and flesh quality

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.     

Supplemental graded levels of neutral phytase using pretreatment and spraying methods in the diet of grass carp,Ctenopharyngodon idellus

A feeding trial was conducted for 8 weeks to evaluate the effects of graded levels of neutral phytase supplementation using pretreatment or spraying method on growth performance, body composition, bone mineral content and serum biochemical parameter in grass carp, Ctenopharyngodon idellus. A control diet without phytase was added and six additional diets were arranged as a 2 × 3 factorial with two methods (pretreatment or spraying) and three levels of phytase (500, 1000 or 1500 U kg^?1). The results showed that supplemental phytase at different levels in the diet and with different application methods all improved weight gain, specific growth rate and protein efficiency ratio of grass carp (P < 0.05). The feed conversion ratio in phytase‐supplemented groups was lower than the control. Dietary phytase addition reduced the lipid content in the whole body of grass carp. Phytase supplementation with different method increased ash and mineral (P, Ca, Mg and Zn) contents in whole‐body and vertebra (P < 0.05). The increase in these mineral contents was also observed in the serum. Based on the results, we may conclude that: 1) supplemental dietary phytase, regardless of the application methodology, improved the growth performance and nutrient utilization in grass carp; 2) the pretreatment mode of phytase application was more effective than spraying at the same phytase level.     

Effect of dietary lipid oxidation with vitamin C and E supplementation on fillet quality of red sea bream,Pagrus major (Temminck & Schlegel) during storage

An experiment was conducted to determine the effects of different levels of dietary vitamin C (VC) and E (VE) supplementation on fillet quality of red sea bream fed oxidized fish oil (OFO). Fish with an average body weight of 205.0 g were fed four test diets for 9 weeks. Control diet contained fresh fish oil (FFO) with 100 mg kg^?1 of VE and 500 mg kg^?1 of VC (FFO100E/500C). The other three diets contained OFO with varying levels of VE (mg kg^?1) and VC (mg kg^?1) (OFO100E/500C, OFO200E/500C and OFO200E/1000C). After feeding trial, two fillets from each fish by hand filleting were stored in a refrigerator at 4°C for 96 h during analyses. Results showed that fish fed OFO increased fillet thiobarbituric acid reactive substances (TBARS) and K‐value, and decreased fillet VC and VE concentrations during storage time. Supplementation of VC did not have any detectable effect on fillet quality. Increasing dietary VE supplementation increased fillet VE concentrations, reduced fillet TBARS and K‐value values of red sea bream. Therefore, we suggest that dietary supplementation of 200 mg kg^?1 of vitamin E could improve fillet oxidative stability of red sea bream fed OFO.     

Linseed oil inclusion in sea bream diets: effect on muscle quality and shelf life

Dietary lipid source in aquaculture has become a central topic in research whilst natural resources availability diminishes. Hence, to weigh up and forecast consumers impressions, the impact of partial (70%) and complete (100%) dietary replacement of fish oil (FO) by linseed oil (LO) on sensory and quality attributes was studied during the edible shelf life of gilthead sea bream (Sparus aurata). Physico‐chemical parameters (pH, torrymeter, total volatile basic nitrogen, thiobarbituric acid reactive substances and texture), and sensory analysis, both in cooked and raw fish were carried out during 17 days of ice storage. Throughout ice storage, feeding with LO diets, TBARS values remained lower on muscle than those found when feeding FO control diet. On freshly caught fish (day 0 of ice storage), statistically significant dietary texture variations were recorded on cooked fillet fed FO diet. No sensory differences on Quality Index Method, sensory profile or Torry scheme were found with partial or total LO replacement diets.     

Eggs of gilthead seabream Sparus aurata L. as a potential enrichment product of Brachionus sp. in the larval rearing of gilthead seabream Sparus aurata L.

The gilthead seabream Sparus aurata L. is a sequential spawner whose reproductive cycle can be manipulated to obtain year-round egg and fry production. Hence, there is an overproduction of eggs in commercial hatcheries that is normally wasted. Two feeding experiments were conducted with the purpose of investigating the potential use of fresh and freeze-dried gilthead seabream eggs for the enrichment of live preys. The first experiment was also designed to study the possibility of using freeze-drying as a conservation process for eggs in excess. Larvae were reared for 20 days after hatching (DAH),on a diet of Brachionus sp. As experimental controls, the commercial enrichment emulsion SUPER HUFA was used in the first experiment, and the microalgae Nannochloropsis sp. in the second. This study demonstrated the potential of gilthead seabream eggs as an enrichment product to be used in the feeding of the first larval stages of Sparus aurata L. The data obtained emphasize the need to have an overall perspective of the nutritional requirements of the organisms in culture.     

Transmission of lymphocystis disease virus to cultured gilthead seabream,Sparus aurata L., larvae

The transmission of lymphocystis disease virus (LCDV) to gilthead seabream, Sparus aurata L., larvae was investigated using fertilized eggs from a farm with previous reports of lymphocystis disease. LCDV genome was detected by PCR‐hybridization in blood samples from 17.5% of the asymptomatic gilthead seabream broodstock analysed. Using the same methodology, eggs spawned from these animals were LCDV positive, as well as larvae hatched from them. The presence of infective viral particles was confirmed by cytopathic effects development on SAF‐1 cells. Whole‐mount in situ hybridization (ISH) and immunohistochemistry (IHC) showed the presence of LCDV in the epidermis of larvae hatched from LCDV‐positive eggs. When fertilized eggs were disinfected with iodine, no viral DNA was detected either in eggs (analysed by PCR‐hybridization) or in larvae (PCR‐hybridization and ISH). These results suggest the vertical transmission of LCDV, the virus being transmitted on the egg surface. Larvae hatched from disinfected eggs remain LCDV negative during the endotrophic phase, as showed by PCR‐hybridization, ISH and IHC. After feeding on LCDV‐positive rotifers, viral antigens were observed in the digestive tract, which suggests that viral entry could be achieved via the alimentary canal, and that rotifers can act as a vector in LCDV transmission to gilthead seabream larvae.     

Effect of miconazole nitrate on immunological response and its preventive efficacy in Labeo rohita fingerlings against oomycetes Saprolegnia parasitica

This study evaluated the effect of sublethal doses of antifungal drug miconazole nitrate (MCZ) on immunological responses and its role as a prophylactic drug against S. parasitica in Labeo rohita fingerlings. Fish were fed with sublethal doses of MCZ, that is, T1—6.30 mgMCZ kgBW^?1, T2—12.61 mgMCZ kgBW^?1 and T3—25.22 mgMCZ kgBW^?1, and sampling was done at different time intervals for 240 hr. Immunological parameters viz. lysozyme activity, oxygen radical production and plasma antiprotease activity showed significant enhancement (p < 0.05) in fish fed with T2 and T3 doses. Expression of immune‐relevant genes such as TLR‐22 and β2‐M showed significantly higher expression at 6 hr and 24 hr of sampling in both liver and head kidney. However, these genes showed a downregulation after 120 hr of sampling in both the tissues. Preventive efficacy study showed that single dose of MCZ provides protection against oomycetes up to the fourth day of infection. Significantly higher mortality was observed in control diet‐fed fish as compared to fish fed with MCZ medicated diet. Thus, it can be concluded that the MCZ can act as a potent antifungal agent for preventing oomycetes infection as well as to enhance the immune response.     

Influence of lupin and rapeseed meals on the integrity of digestive tract and organs in gilthead seabream (Sparus aurata L.) and goldfish (Carassius auratus L.) juveniles

Two rearing trials were conducted to evaluate the effects of dietary lupin (LM) and rapeseed (RM) meals in gilthead seabream (Sparus aurata L.) and goldfish (Carassius auratus L.) juveniles. Each plant meal was incorporated at the rate of 200 g kg^?1 in two distinct diets, which were compared with a fishmeal‐based diet as control. After 1 month, the two plant diets did not influence the whole body growth, but the digestive systems were affected. The splenosomatic index was reduced with two plant meals in goldfish and with RM in seabream. The hepatosomatic index was only reduced in LM‐fed seabream. Cellular characteristics were also affected. The largest liver cells were observed in RM‐fed goldfish suggesting changes in metabolic function. The LM and RM diets stimulated in seabream, especially the reaction in haematopoietic tissues with the proliferation of melano‐macrophages centres, and a tendency for elongated villus height in the anterior intestine thus that possibly compensated for a reduction in digestive function. Such adaptive structural modifications and the absence of degenerative signs allowed concluding that the integrity of the digestive system was maintained in fish fed plant meals.     

Vegetable oil blend as alternative lipid resources in diets for gilthead seabream, Sparus aurata

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.     

Enhancement of gilthead seabream (Sparus aurata) larval growth by dietary vitamin E in relation to two different levels of essential fatty acids

The objective of this study was to determine the effect of dietary vitamin E on gilthead seabream (Sparus aurata) growth and survival, at two different highly unsaturated fatty acids (HUFAs) levels. Eighteen days old gilthead seabream larvae were fed four formulated experimental diets combining two different dietary levels of HUFAs (M: medium 2.5 + 1.5, DHA + EPA, H: high 5 + 2.5 DHA + EPA g per 100 g) with two different levels of vitamin E (M: medium 540 mg kg^?1, H: high 2900 mg kg^?1): MM, MH, HM, HH (HUFA/vitamin E). After 2‐week feeding trial, the average survival rate was 52.6% and there were no significant differences found among treatments. Increase in vitamin E up to high level markedly improved larval growth, particularly when dietary HUFA levels were lower, suggesting a higher protection value when these fatty acids are more limiting. At medium dietary HUFA levels, increase in vitamin E from medium to high level enhanced larval growth performance in terms of total length. Moreover, increase in vit E enhanced HUFAs content in the larval polar lipids denoting the anti‐oxidative effect of vitamin E.