Effect of an experimental microparticulate diet on the growth, survival and fatty acid profile of gilthead seabream (Sparus aurata L.) larvae

In recent years, a great deal of interest has emerged in the development of microdiets as an economic alternative to live food, in the larval culture of marine fish species. The ability to grow Sparus aurata larvae on a prototype microparticulate diet was examined. To achieve this objective, four feeding regimes differing in the time when the microdiet was introduced (3, 7 or 12 days) and one based exclusively on an inert diet were tested, during the first 22 days of larval life. Significant differences in larval growth were found between the experimental feeding regimes and their corresponding controls (enriched rotifers during the whole experimental period); the larvae in the co-feeding regimes and with an exclusive microparticulate diet were always significantly smaller than larvae fed on rotifers alone. However, the difference was minimised by introducing the inert diet at a later date. A lower survival was found in larvae with a co-feeding regime, in comparison with the control treatments and the survival was significantly lower in larvae fed exclusively on a microparticulate diet. The fatty acid analysis revealed that the experimental microencapsulated diet and the rotifers enriched with Protein Selco® presented relatively similar fatty acid content. In spite of the slightly higher (n?3)/(n?6) and Docosahexaenoic acid (DHA)/Eicosapentaenoic acid (EPA) ratios and somewhat lower highly unsaturated fatty acid (HUFA) content found in the inert diet, the fatty acid composition of the diets cannot explain the differences found in larval performance. The results revealed that the complete replacement of live prey with the tested microparticulate diet is still not possible in S. aurata larval rearing. Nevertheless, better growth and survival results and a substantial reduction in the daily supply of live food can be achieved with a combination of microdiet and live prey.     

Optimum soybean lecithin contents in microdiets for gilthead seabream (Sparus aurata) larvae

The aim of the present study was to determine the optimum dietary levels of soybean lecithin (SBL) for seabream (Sparus aurata) larvae, and its influence on production performance and digestive enzymes activity. Larvae were fed five formulated microdiets with five levels of SBL. Complete replacement of live preys with the experimental microdiets for seabream larvae at 16 dph produced over 55% survival rates, particularly in fish fed with the highest levels of SBL. Moreover, increase in dietary SBL up to 80 g kg⁻¹ significantly improved larval growth, leading to high final total length and body weight. An increase in alkaline phosphatase activity with the elevation up to 80 g kg⁻¹ SBL was also found denoting a better maturation of the digestive system. Besides, there was a stimulatory effect of dietary SBL on PLA2 activity. Finally, increasing dietary SBL lead to better utilization of dietary highly unsaturated fatty acid, as it was reflected in their higher content in both neutral and polar lipid of the larvae. In summary, elevation of dietary SBL up to 80 g kg⁻¹ in microdiets for seabream significantly improved digestive enzymes activities, enterocyte maturation, utilization and deposition of dietary essential fatty acids and larval growth, as a consequence of a better digestion, absorption, transport and deposition of dietary nutrients.     

Optimum krill phospholipids content in microdiets for gilthead seabream (Sparus aurata) larvae

The aim of the present study was to determine the optimum dietary levels of krill phospholipids (KPL) for sea bream (Sparus aurata) larvae, and its influence on larval development and digestive enzymes activity. Larvae were fed five formulated microdiets with five different levels of KPL. Complete replacement of live preys with the experimental microdiets for seabream larvae produced high survival and growth rates, particularly in fish fed the highest levels of KPL. In the present study, increase in dietary KPL up to 120 g kg^?1 (100 g kg^?1 total PL) significantly improved larval survival and growth, whereas further increase did not improve those parameters. An increase in alkaline phosphatase, trypsin and lipase activity with the elevation of KPL up to 120 g kg^?1 was also found denoting a better functioning of digestive system. Besides, there was a linear substrate stimulatory effect of dietary KPL on phospholipase A2 activity. Finally, increasing dietary KPL lead to better assimilation of n‐3 HUFA especially eicosapentaenoic acid, reflected in the higher content of these fatty acids in both neutral and polar lipids of the larvae. In summary, KPL were found to be an excellent source of lipids for seabream larvae. Optimum inclusion levels of this ingredient in microdiets to completely substitute live preys at this larval age were found to be 120 g kg^?1 KPL.     

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.     

Effect of dietary vegetable oils on health and liver histology of gilthead seabream (Sparus aurata) growers

There is an increasing trend towards the replacement of fish oil (FO) by vegetable oils in feeds for farmed fish, particularly marine carnivores. Previous researches on partial or complete replacement of FO by alternate vegetable oils for young gilthead seabream (Sparus aurata) were successful. The aim of the present study was to investigate the effects of different dietary vegetable oils on seabream growers' health and liver structure. Two dietary vegetable oil blends (Mix 1 and Mix 2), namely sunflower oil, cottonseed oil and either linseed oil (LO) or soybean oil (BO), were tested as 60% FO substitutes versus the 100% FO control (CTR) diet. Three isonitrogenous (∼47% CP) and isolipidic (18.2% L) diets were fed, twice a day, 6 days a week to apparent satiation, to triplicate groups of seabream growers (mean IW, 130.85 g) in PVC tanks. The growth trial lasted for 20 weeks at an average ambient water temperature of 27.0±1.8°C. At the end of the experiment, fish attained market size (300–400 g) and their health status was evaluated by blood analyses, head kidney prints and liver histology. Haemoglobin and haematocrit contents, erythrocyte (RBC) and leucocyte (WBC) count remained significantly unaffected by any dietary treatments. Despite the apparent relatively higher thrombocyte counts for fish fed vegetable oil diets, especially Mix 2 as compared with those of CTR fish, variations were found to be insignificant (P>0.05). However, a slight deformation in erythrocyte shape was noticed in the blood films of fish fed the vegetable oil diets. Inclusion of either dietary vegetable oil blend had also elevated the number of both developing myelocytes and phagocytes in fish head kidney prints examined compared with those of CTR fish particularly for Mix 2 group. Liver from seabream fed vegetable oils showed slightly swelled hepatocytes due to accumulation of oil droplets in the cytoplasm. In the liver sections investigated ultra‐structurally, nuclei and cytoplasmic organelles were shifted towards the cell periphery. Hepatocytes of fish fed Mix 2 diet showed relative shrinkage and picnotic nuclei, compared with those of CTR fish, suggesting an effect on lipid transport and/or metabolism in fish. The comparative hepatic features between experimental fish groups were described. Accordingly, Mix 1 diet (with LO) was considered better than Mix 2 (with BO) in terms of influence on seabream growers' health status.     

Effects of dietary mannan oligosaccharides in early weaning diets on growth,survival, fatty acid composition and gut morphology of gilthead sea bream (Sparus aurata,L.) larvae

Early weaning of marine fish larvae with dry diets delays gut maturation and reduces growth rates. In juvenile and adult forms of several marine fish species, inclusion of dietary mannan oligosaccharides (MOS) improves gut integrity and functionality, but the effects of MOS inclusion in gilthead sea bream (Sparus aurata, L.) larval diets have not been addressed yet. Thus, this study assesses the effects of dietary MOS inclusion on survival, growth performance, gut morphology, feed acceptance and quality of gilthead sea bream larvae. For that purpose, 16 days post‐hatched gilthead sea bream larvae were fed four graded levels of MOS (Biomos^®, Alltech, Nicholasville, KY, USA) in weaning diets as follows: 0 g kg^?1 MOS, 0.5 g kg^?1 MOS, 1.5 g kg^?1 MOS and 2 g kg^?1MOS. Dietary MOS did not affect feed acceptance in gilthead sea bream larvae (P > 0.05). MOS supplementation was correlated in a dose‐dependent way with higher larval survival (P = 0.026). After 15 days of feeding, dietary MOS increased whole larvae (P < 0.01) arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid. Gilthead sea bream larvae fed 2 g kg^?1 MOS presented higher gut occupation with goblet cells after feeding compared with larvae fed the other dietary treatments. Overall, the results suggest that inclusion of MOS in early weaning diets for gilthead sea bream improves essential fatty acid utilization and may promote growth and final survival.     

Importance of the relative levels of dietary arachidonic acid and eicosapentaenoic acid for culture performance of gilthead seabream (Sparus aurata) larvae

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.     

Effect of dietary substitution of fish oil by Echium oil on growth, plasma parameters and body lipid composition in gilthead seabream (Sparus aurata L.)

Gilthead seabream juveniles were fed on either a fish oil (FO)-containing diet or a diet containing a 50 : 50 blend of FO and Echium oil (EO) to determine the effect of EO on growth, plasma parameters and tissue lipid compositions. After 4 months of feeding, there was a significant increase of 18 : 2 n -6 and a reduction of approximately 25% of 20 : 5 n -3 in the flesh of fish fed the EO diet. At this point, half of the fish that fed on EO were returned to the FO diet as a third treatment and the trial continued with the three groups for a further 3 months. At the end of the experiment, food intake, survival, growth and plasma parameters were not affected by the inclusion of dietary EO. However, hepatosomatic index (HSI), total lipid and triacylglycerol contents of muscle decreased in fish fed the EO diet. Feeding the EO diet resulted in significant increments of potentially health-promoting fatty acids such as 18 : 3 n -6, 18 : 4 n -3 and 20 : 3 n -6 but reduced n -3 highly unsaturated fatty acids, particularly 20 : 5 n -3. When EO-fed fish were returned to the FO diet, tissue lipid contents and HSI tended to increase, but 18 : 2 n -6 and 20 : 5 n -3 levels were not fully restored to the levels of fish fed the FO diet for the entire trial. Furthermore, the fatty acids present in EO, which may promote beneficial health effects, were reduced.     

Optimum dietary soybean meal level for maximizing growth and nutrient utilization of on-growing gilthead sea bream (Sparus aurata)

Six isonitrogenous [450 g kg⁻¹ crude protein (CP)] and isoenergetic diets (23 kJ g⁻¹) with six levels of defatted soybean meal inclusion (0, 132, 263, 395, 526 and 658 g kg⁻¹) in substitution of fish meal were evaluated in gilthead sea bream of 242 g initial weight for 134 days. Fish fed diets S0, S13, S26 and S39 had a similar live weight (422, 422, 438 and 422 g, respectively) but fish fed diets S53 and S66 obtained the lowest final weight (385 and 333g, respectively), and similar results were presented in specific growth rate (SGR). Fish fed diets S53 and S66 also obtained the highest feed conversion ratio (FCR). Quadratic multiple regression equations were developed for SGR and FCR which were closely related to dietary soybean level. The optimum dietary soybean levels were 205 g kg⁻¹ for maximum SGR and 10 g kg⁻¹ for minimum FCR. Sensorial differences were appreciated by judges between fish fed S0 and S39 soybean level, but after a re-feeding period of 28 days with diet S0, these differences disappeared.     

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.     

The effect of dietary exogenous digestive enzymes on ingestion,assimilation, growth and survival of gilthead seabream (Sparus aurata,Sparidae, Linnaeus) larvae

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.     

Effects of varying dietary protein and energy supply on growth, body composition and protein utilization in gilthead seabream (Sparus aurata L.)

Diets formulated with increasing digestible energy (10–22 DE MJ kg⁻¹) contents and decreasing digestible crude protein (DCP)/DE ratios (34–15 g MJ⁻¹) were fed to triplicate groups of Sparus aurata in three consecutive trials. Fish were hand-fed to apparent satiation and voluntary feed intake was found to be dependent upon dietary DE content. Daily growth was regulated both by energy and protein intake and reached its maximum at high energy levels. Growth composition showed narrow limits regarding protein gain (157–190 g kg⁻¹) and a wider range regarding lipid (55–210 g kg⁻¹) deposition reflecting the dietary energy to protein supply. Energy utilization for growth was constant at a value of 0.50 regardless of energy intake. Efficiency of protein utilization for growth varied between 0.33 and 0.60 depending on the DCP/DE ratio in the diet. The optimal protein utilization for protein deposition was found to be at 0.47. These values allow daily energy and protein requirements for growing S. aurata to be quantified. This demonstrates that the optimal dietary DCP/DE supply changes with fish size, growth potential and daily feed intake.     

Influence of n-3 highly unsaturated fatty acid deficiency on the lipid composition of broodstock gilthead seabream (Sparus aurata L.) and on egg quality

A feeding experiment was conducted on gilthead seabream (Sparus aurata) broodstock to investigate the incidence of n-3 highly unsaturated fatty acids (n-3 HUFA) dietary deficiencies on the lipid composition of female liver, gonads and eggs, in relation to spawning quality. Broodstock were fed a control (C) diet or a n-3 HUFA deficient (D) but linolenic acid rich diet. After 20 weeks of feeding, the results showed that levels of total neutral (TNL) and total polar (TPL) lipids of female gonads and eggs were independent of diet. However the fatty acid composition of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) of female liver, gonads and eggs in the two groups of fish showed marked differences, reflecting the influence of fatty acid levels in the broodstock diets. This influence was even higher in TNL than in the phospholipid classes examined. In fish fed n-3 HUFA deficient diet, fatty acid composition of TNL of female gonads and eggs reflected the diet more than liver. A higher egg production in broodstock fed C diet (1.8% n-3 HUFA in diet) was extended to spawning quality such as percentages of fertilised and hatched eggs.     

Effects of dietary vegetable oils on liver and gonad fatty acid metabolism and gonad maturation in gilthead seabream (Sparus aurata) males and females

A 20-week growth trial was conducted to investigate the effect of two dietary blended vegetable oils (VO) on liver lipogenic enzyme activity, liver and gonad lipid class composition and fatty acid profiles, serum sex hormones, and gonad morphohistology in gilthead seabream, Sparus aurata. Three groups of fish (BW _i 130.9 ± 3.1 g) were fed, close to satiation, three experimental diets: a control (CTRL) contained fish oil (FO) as the sole lipid source (100% FO) and two VO-blended diets in each 60% of FO was substituted by an equal mixture of cottonseed oil (CO), sunflower oil (SFO) and either linseed oil (LO) or soybean oil (SBO), designated as LO or SBO diet, respectively. Each diet was assigned to triplicate groups of fish. Results showed that all dietary treatments presented no significant (P > 0.05) differences in growth rate and feed conversion ratio for sexes combined. Enzyme activities of liver lipogenic enzymes of LO-fed fish (glucose-6-phosphate dehydrogenase (G6PDH), malic enzyme (ME) and fatty acid synthetase (FAS)) were not statistically (P > 0.05) different from those of CTRL fish. Only in the group of fish fed the SBO diet, G6PDH was slightly higher (P < 0.05) for both sexes, while ME showed a significant (P < 0.05) higher activity only in females relative to CTRL fish. Liver FAS enzyme activity remained unaltered among dietary groups. VO-fed fish recorded a significant (P < 0.05) increase in total lipid (TL) and triglyceride (TAG) contents in both liver and gonad, more pronounced in females than in males, concurrent with a significant (P < 0.05) decrease in cholesterol (CHL) and phospholipids (PL), more obvious for the SBO-fed fish, as compared to CTRL. The fatty acid (FA) composition of liver or gonad reflected that of the supplied diet and evidenced a significant (P < 0.01 or <0.05) alteration in the majority of individual FA in VO-fed fish compared to CTRL. There were decreased levels of ARA (20:4 n-6), EPA (20:5 n-3), and DHA (22:6 n-3) in VO-fed fish, more pronounced in females than in males, compared to CTRL. The liver and gonad FA profiles, for males and females, reflected the composition of the diet and showed sex variation in the output of multivariate principal component analysis (PCA). Feeding fish VO diets has also led to a significant (P < 0.05) reduction in serum estradiol level by 15.8 or 22.3% in LO- or SBO-fed fish, respectively, and in testosterone level by 7.7% in the latter dietary group only compared to the CTRL. Histomorphological examination of ovary and testis has indicated a relative retardation in oogenesis and spermatogenesis in VO-fed fish, less obvious in the LO-fed fish compared to CTRL. These results suggest a preference of LO over SBO blend diet in terms of liver lipogenic enzyme activity, liver and gonad lipid content, lipid class composition and fatty acid profile, serum sex hormones as well as gonad maturation. PCA analysis of gonads highlighted the importance of using a 100% marine FO diet for gilthead seabream broodstock for the recovery of a normal FA profile in gonads of fish, previously fed VO over the production cycle, to ensure successful spawning.     

Effect of broodstock diets on total lipids and fatty acid composition of larvae of gilthead sea bream (Sparus aurata L.) during yolksac stage

Total lipid content and total lipid fatty acid compositions were studied in larvae at the yolksac stage of gilthead sea bream from two different broodstocks. The two broodstock diets had the same total lipid content but were different with respect to their fatty acid levels. There were differences in the fatty acid composition of total lipids in the two groups of larvae, reflecting the influence of fatty acid levels in the diets fed to the broodstock. The main fatty acids in both larvae lots during yolksac stage were 16:0, 18:1n-9 and 22:6n-3. The desaturation index Δx = [P + Σ (n − x) − Σ (n − x) diet]/P allowed the determination of the relative importance of the Δ9, Δ6, Δ5 and Δ4 desaturations during the egg and larval yolksac stages. The levels of total lipid fatty acids in eggs and larvae during yolksac period were almost constant and very low desaturation and elongation activities were apparent. A competitive inhibition was observed between the fatty acids of the n-6 series with respect to the ones of the n-3 series in those eggs and larvae from broodstock whose diet contained a high proportion of linoleic acid and its derivatives.     

Alteration of liver and muscle fatty acid composition in gilthead seabream (Sparus aurata) juveniles held at high stocking density and fed an essential fatty acid deficient diet

The aim of the present study was to determine the combined effect of both stress and EFA deficiency on several biological and biochemical parameters. Fish were fed during 15 weeks two isocaloric and isoproteic diets: a control diet based on fish oil and formulated to meet the n-3 HUFA requirements for this species (1.5% of n-3 HUFA) and a deficient diet containing beef tallow and formulated to be deficient in n-3 HUFA. Each experimental diet was evaluated both at high and low stocking densities (10 and 3.2 kg m^–3 of initial density, respectively).High stocking density produced a chronic stress situation with elevation of plasma cortisol levels. It also caused a reduction in hepatosomatic index and liver lipid contents, increasing the oleic acid/n-3 HUFA ratios in the polar lipids. Fish fed the EFA deficient diet at low stocking density showed common deficiency symptoms. High stocking density in fish fed the EFA deficient diet induced a higher degree of EFA deficiency symptoms leading to mortality, liver steatosis, liver lipid deposition, reduced muscle lipid and reduced n-3 HUFA contents, which particularly affected EPA, but not DHA, suggesting a preferential retention of the latter fatty acid, specially in the phosphoglycerides fraction.     

Effects of dietary soybean oil concentration on growth, nutrient utilization and muscle fatty acid composition of gilthead sea bream (Sparus aurata L.)

A 309 days feeding experiment was carried out on gilthead sea bream fingerlings (initial weight 14.7±4.4 g) to evaluate effects of substitution of fish oil with soybean oil in diets on growth and sensory characteristics and muscle fatty acid composition. Duplicate groups of fish were hand fed with four isoenergetic and isonitrogenous diets (46% protein, 14% lipid and 22 MJ kg⁻¹) in which 0%, 24%, 48% or 72% of the fish oil was replaced by soybean oil. Fish fed diet 72% reached a lower final weight (324 g) than fish fed diets 0%, 24% and 48% (349, 343 and 338 g respectively). Feed intake, protein efficiency ratio, body composition and economic profitability were not influenced by the amount of soybean oil in the diets, but muscle fatty acid composition differed with diets. Panellists observed significant sensory differences between fish fed diet 0% and diet 72%. These results verified the possibility of feeding sea bream until they reached commercial weight with a 48% dietary substitution of fish oil for soybean oil.     

Effect of dietary phospholipid level on the development of gilthead sea bream (Sparus aurata) larvae fed a compound diet

The aim of the study was to determine the influence of dietary phospholipid (PL) levels on survival and development of first feeding gilthead sea bream (Sparus aurata) larvae. Larvae were fed from day 4 to 23 posthatching with an isoproteic and isolipidic formulated diet with graded levels of PL from 90–150 g kg^?1 dry matter (DM). A dietary PL content of more than 90 g kg^?1 DM seems to be necessary for sustaining growth of first feeding sea bream larvae. The survival rates of larvae fed the formulated diets (31–40% at day 23) were similar to those generally observed in marine aquaculture hatcheries with live prey feeding sequence. However, this high survival rate was not associated with high growth and the larvae showed, at the end of the study, a high proportion of individuals with abnormal liver and calculi in the urinary bladder. It is concluded that although the diets used here cannot be used in total replacement of live preys, they constitute a solid starting point for further nutritional studies with first feeding gilthead sea bream larvae.     

Energy and protein requirements for maintenance and growth in gilthead seabream (Sparus aurata L.)

Factorial determinations of energy and protein requirements in growing Sparus aurata were carried out at 23–24°C. The energy content in the whole fish was dependent on fish weight and ranged from 5 to 11 MJ kg⁻¹ body mass for 1–250 g fish, whereas the protein content remained constant at 179 g kg⁻¹.
During starvation the fish lost 42.5 kJ body weight (BW) (kg)^−0.83 day⁻¹ and 0.42 g protein BW (kg)^−0.70 day⁻¹. The maintenance requirement for energy was calculated to be 55.8 kJ BW (kg)^−0.83 day⁻¹ and for protein 0.86 g BW (kg)^−0.70 day⁻¹. Utilization of digestible energy and digestible crude protein below and at maintenance was determined as 0.72 and 0.51, respectively. Utilization of digestible energy and digestible crude protein for growth above maintenance was determined as 0.46 and 0.28, respectively.
These values allow estimation of requirements for growing Sparus aurata .     

Effects of dietary inclusion of peas,chickpeas and faba beans on growth,feed utilization and health of gilthead seabream (Sparus aurata)

Three legumes [field peas (P), chickpeas (CP) and faba beans (B)] at two inclusion levels [170 g kg^?1 (L) and 350 g kg^?1 (H)] were evaluated in a 13‐week experiment with triplicate groups of 92.6 ± 5.0 g gilthead seabream (Sparus aurata L.). A control diet included wheat meal, fishmeal (FM) and a mixture of plant ingredients as protein sources. Diets were formulated to be isonitrogenous and isoenergetic and processed in a twin‐screw extruder. Restricted feeding was applied (15 g kg^?1 of body weight) and growth, haematology and histology parameters were evaluated. Decreased, but not significant, growth values were observed for all diets including legumes compared to the control. Poorer feed conversion ratio values were observed for both P diets and for high level B diet. Liver glycogen increased with increasing starch level, but hepatosomatic index did not differ significantly for any of the diet treatments. Histological examination of internal organs showed no pathological abnormalities that could be related to nutritional treatment. The study indicated that the tested legumes are ingredients that could be used in farmed seabream diets up to 350 g kg^?1 without negative effects replacing other carbohydrate sources and part of FM.