Juvenile Sea Bream Research Articles

Effects of dietary phytosterols and soy saponins on growth, feed utilization efficiency and intestinal integrity of gilthead sea bream (Sparus aurata) juveniles

The use of plant ingredients in aquafeeds for piscivorous fish species is a reality that exposes fish to a number of antinutritional factors present in plants. The present study is the first to evaluate the effect of two purified antinutrients, saponins and phytosterols, in sea bream juveniles. For that purpose, seven diets were formulated: a control diet (fishmeal and fish oil based) and six experimental diets containing low (1 g kg− 1, SapL) or high (2 g kg− 1, SapH) levels of purified soya saponins, low (5 g kg− 1, PhytL) or high (10 g kg− 1, PhytH) levels of purified phytosterols or a combination of 1 g kg− 1 saponins + 5 g kg− 1 phytosterols (SapPhytL) or 2 g kg− 1 saponins + 10 g kg− 1 phytosterols (SapPhytH). Fish were fed for 48 days in order to evaluate growth performance, feed utilization, plasma cholesterol, and gut health as assessed by histomorphological evaluation and gene expression profiling of immune and functional markers. Fish fed the diets PhytH, SapPhytL and SapPhytH showed better feed utilization and PhytH and SapPhytH showed higher protein utilization than the other groups, although this was not reflected in improved growth performance. Histomorphological analysis of the distal intestine revealed increased variation in supranuclear vacuole sizes after 48 days of feeding diets SapH, SapPhytL and SapPhytH and increased number of intraepithelial leukocytes in response to all dietary treatments except SapL and SapPhytL. Although juvenile sea bream growth was not affected by dietary inclusion of saponins and phytosterols, the results indicated some disturbances of the intestinal mucosal structure that could compromise function and/or protection from potential dietary antigens or opportunistic pathogens.

Effects of the microalga Scenedesmus almeriensis as fishmeal alternative in diets for gilthead sea bream, Sparus aurata, juveniles

The rising costs of fishmeal worldwide promote great research effort aimed to find alternative and renewable ingredients for aquafeeds. In the last years considerable attention has been paid to the use of algae as a potential ingredient for fish feeds. The objective of this work was to evaluate the effects of the microalgae Scenedesmus almeriensis incorporated to diets intended to feed sea bream (Sparus aurata) juveniles in a 45-day trial. Growth, body composition, and intestinal functionality of fish were studied. Microalgae meal was tested in triplicate at different inclusion levels (0%, 12%, 20%, 25% and 39%). At the end of the trial, individual body weight was recorded for evaluation of growth and nutrient utilization, and biological samples were obtained for proximate analysis, determination of digestive enzyme activities, intestinal histology, and microvilli morphological evaluation. Results indicated that S. almeriensis did not cause negative effects on fish growth or nutrient utilization efficiency. Growth rate and protein utilization in fish fed on a diet with 20% Scenedesmus meal tended to be higher, although not significantly different from those fed on control diet. None of the treatments caused adverse effects on body composition. Fish fed 12% S. almeriensis showed higher trypsin than animals fed on control diet. Leucine-aminopeptidase and alkaline phosphatase activities showed a quadratic response with increasing levels of Scenedesmus biomass. Ultrastructural study revealed that the dietary inclusion of algal biomass, especially at 20% level, significantly increased the absorptive capacity of intestinal mucosa in both the anterior and posterior intestinal regions. This study confirmed the usefulness of S. almeriensis to partially replace fishmeal in practical diets for gilthead sea bream juveniles.

Beef tallow as an alternative to fish oil in diets for gilthead sea bream (Sparus aurata) juveniles: Effects on fish performance, tissue fatty acid composition, health and flesh nutritional value

Gilthead sea bream juveniles of 135 g average body weight were fed for 120 days a fish oil‐based commercial diet (CTRL) or one of two experimental isonitrogenous and isolipidic low fat (LF) fish meal‐based diets differing only by the lipid source, in order to evaluate the efficacy of beef tallow (BT) as an ingredient in aquafeeds. Both experimental feeds were formulated with 60 g/kg of BT; the LFBTFO diet also contained 35 g/kg of fish oil (FO) whereas a blend of BT and vegetable oils (VO) completely replaced FO in the LFBTVO diet. No differences in growth and feed efficiency were found between fish fed the LFBTFO diet and the CTRL group whereas fish fed the diet devoid of FO (LFBTVO) presented the poorest growth indicators and the lowest feed and protein efficiencies. The use of LF feeds contributed to maintain the hepatosomatic index and the proportion of triacylglycerols (TAG) in muscle and brain in spite of the dietary replacement of FO. Flesh from fish fed the LFBTFO diet supplied the same absolute amount of EPA + DHA than that of fish fed the CTRL diet, whereas a reduction of approximately 45% was registered when fish were deprived of FO.Practical applications: High proportions of BT can effectively be used as a valuable alternative to partially substitute FO in diets for gilthead sea bream juveniles without significantly affecting fish performance and health while promoting a limited impact on its health benefits for human consumption. The decline in the inclusion of marine ingredients in aquafeeds could actively contribute to the sustainability and profitability of the marine aquaculture industry.

Cottonseed oil as a complementary lipid source in diets for gilthead seabreamSparus auratajuveniles

The efficacy of using cottonseed oil (CSO) as a fish oil (FO) substitute in gilthead seabream (Sparus aurata) juveniles feed was evaluated. Fish (BWi 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.

Endocrine regulation of carbonate precipitate formation in marine fish intestine by Stanniocalcin and PTHrP

In marine fish, high epithelial bicarbonate secretion by the intestine generates luminal carbonate precipitates of divalent cations that play a key role in water and ion homeostasis. In vitro studies highlight the involvement of the calciotropic hormones PTHrP (parathyroid hormone-related protein) and stanniocalcin (STC) in the regulation of epithelial bicarbonate transport. The present study tested the hypothesis that calciotropic hormones have a regulatory role in carbonate precipitate formation in vivo. Sea bream (Sparus aurata) juveniles received single intraperitoneal injections of piscine PTHrP(1-34), the PTH/PTHrP receptor antagonist PTHrP(7-34) or purified sea bream STC, or were passively immunized with polyclonal rabbit antisera raised against sea bream STC (STC-Ab). Endocrine effects on the expression of the basolateral sodium bicarbonate co-transporter (Slc4a4.A), the apical anion exchangers Slc26a6.A and Slc26a3.B, and the V-type proton pump β-subunit (Atp6v1b) in the anterior intestine were evaluated. In keeping with their calciotropic nature, the hypocalcaemic factors PTHrP(7-34) and STC up-regulated gene expression of all transporters. In contrast, the hypercalcaemic factor PTHrP(1-34) and STC antibodies down-regulated transporters involved in the bicarbonate secretion cascade. Changes in intestine luminal precipitate contents provoked by calcaemic endocrine factors validated these results: 24 h post-injection either PTHrP(1-34) or immunization with STC-Ab reduced the carbonate precipitate content in the sea bream intestine. In contrast, the PTH/PTHrP receptor antagonist PTHrP(7-34) increased not only the precipitated fraction but also the concentration of HCO3(-) equivalents in the intestinal fluid. These results confirm the hypothesis that calciotropic hormones have a regulatory role in carbonate precipitate formation in vivo in the intestine of marine fish. Furthermore, they illustrate for the first time in fish the counteracting effect of PTHrP and STC, and reveal an unexpected contribution of calcaemic factors to acid-base balance.

ミズクラゲ給餌によるマダイ人工孵化稚魚の横臥傾向の改善

ミズクラゲ給餌によるマダイ人工孵化稚魚の横臥傾向の改善

Evaluation of dietary protein and lipid requirements of two-banded seabream (Diplodus vulgaris) cultured in a recirculating aquaculture system

The objective of this study is to investigate the effects of dietary protein and lipid levels on the growth performance and bioeconomic benefits of two-banded seabream (Diplodus vulgaris) juveniles, a candidate species for aquaculture sector. Eight experimental diets were formulated with four protein (50, 45, 40 and 35 %) levels for each of the two lipid levels (15 and 10 %). Triplicate groups of juvenile fish with an average initial body weight of ~3.64 g were reared in a recirculating aquaculture system and hand fed twice a day until satiation for a period of 60 days. In the experiment, no difference in survival rate was found between the different groups. Relative growth rate (RGR), specific growth rate (SGR), feed conversion ratio (FCR) and daily feed intake were not significantly affected by increasing protein and/or lipid treatments in this present study. However, the RGR, SGR and FCR values showed slightly better efficiency in the experimental group (35/15) fed with lower protein content (35 %) and higher lipid level (15 %) compared with those fed other diets. According to bioeconomic analyses results, the diet with the 35 % protein and 15 % lipid generated the best profit. The results suggest that two-banded seabream can be accepted as a promising alternative species for the aquaculture industry and optimum growth of two-banded seabream fingerlings can be obtained when they are fed a diet containing 35 % crude protein and 15 % crude lipid.

Naturally Occurring Stable Isotopes Reflect Changes in Protein Turnover and Growth in Gilthead Sea Bream (Sparus aurata) Juveniles under Different Dietary Protein Levels

Ideal nutritional conditions are crucial to sustainable aquaculture due to economic and environmental issues. Here we apply stable isotope analysis as an indicator of fish growth and feeding balance, to define the optimum diet for efficient growing conditions. Juveniles of gilthead sea bream were fed with six isoenergetic diets differing in protein to lipid proportion (from 41/26 to 57/20). As protein intake increased, δ¹⁵N and Δδ¹⁵N of muscle and Δδ¹⁵N and Δδ¹³C of its protein fraction decreased, indicating lower protein turnover and higher protein deposition in muscle. This is reflected in the inverse relationship found between Δδ¹⁵N and growth rate, although no differences were observed in either parameter beyond the protein/lipid proportion 47/23. Principal component analysis (PCA) also signaled 47/23 diet as the pivotal point with the highest growing efficiency, with isotopic parameters having the highest discrimination load. Thus, muscle isotope composition, especially ¹⁵N, can be used to evaluate nutritional status in farmed fish.

Effect of acoustic environment on gilthead sea bream (Sparus aurata): Sea and onshore aquaculture background noise

The present study evaluated the impact of sea background noise (the acoustic environment of the offshore aquaculture system) and onshore aquaculture system's ambient noise on the welfare of gilthead sea bream juveniles (Sparus aurata) through primary, secondary (biochemical and haematological indexes) and tertiary (growth performances) stress responses. The experiment lasted 120days during which two different playlists of acoustic stimuli were projected inside six experimental tanks (each condition was replicated in three tanks). Offshore aquaculture noise conditions were recreated as the typical acoustic field in proximity of an offshore sea cage for fish farming using a random sequence of quiet sea background and boat noises. The acoustic field inside an onshore open concrete tank for fish farming represented the onshore aquaculture noise conditions. The other three tanks were used as a control condition without acoustic projection. The weights and lengths of fish exposed to offshore aquaculture noise were higher than the specimens in the control and onshore aquaculture groups. Moreover, higher levels of serum cortisol, glucose, red blood cell count, haematocrit value and haemoglobin content and lower levels of white blood cells were recorded in fish groups from the control and onshore treatments. These results allow us to hypothesise that offshore aquaculture noise and the sea soundscape in particular positively influence growth performance and could reduce stress and improve the welfare of the sea bream.

Different protein to energy ratio diets for gilthead sea bream (Sparus aurata): Effects on digestive and absorptive processes

Sea bream juveniles were fed for a 12-week period with 7 isoenergetic diets with different levels of protein (35, 38, 41, 44, 47, 50 and 53%). The diets were formulated by changing simultaneously the levels of lipid (from 27 to 19%) and starch (from 21 to 10%). After the growth period, we studied the digestive enzyme activities at 5h post-feeding and the nutrient absorption capacity at 24h post-feeding. A progressive increase in the total protease activity (TPA) was found as the content of diet protein rose (from 35 to 41%) and a diminution of TPA activity was detected in sea bream fed high soybean concentrate content diets (50 and 53% dietary protein). Lipase activity did not change by dietary composition. An up-regulation of α-amylase activity, and d-glucose and l-Ala absorption capacities was found in fish fed with the lowest carbohydrate diets, corresponding to 50 and 53% dietary protein. Moreover, the l-lysine absorption capacity was upregulated in fish fed with low protein diets (35, 38, 41 and 44%). Thus, changes in diet composition can modulate enzymatic activities and nutrient absorption capacity, to improve food use and assure growth performance. In this sense, only sea bream fed with the lowest protein diet (35%) had a significantly lower SGR (<1), although they had the highest voluntary feed intake. Sea bream fed with P44 and P47 diets need the minimal adaptive changes to diet and showed good growth.

Effect of partially protected butyrate used as feed additive on growth and intestinal metabolism in sea bream (Sparus aurata)

Butyrate is a short-chain fatty acid extensively used in animal nutrition since it promotes increases in body weight and other multiple beneficial effects on the intestinal tract. Although such effects have been demonstrated in several species, very few studies have assessed them in fish. On the other hand, little is known about the metabolic processes underlying these effects. In the present work, growth parameters and changes in more than 80 intestinal metabolites (nucleotides, amino acids and derivatives, glycolytic intermediates, redox coenzymes and lipid metabolism coenzymes) have been quantified in juvenile sea bream fed a butyrate-supplemented diet. Results showed a significant increase in the weight of fish receiving butyrate, while metabolomics provided some clues on the suggested effects of this feed additive. It seems that butyrate increased the availability of several essential amino acids and nucleotide derivatives. Also, the energy provision for enteric cells might have been enhanced by a decrease in glucose and amino acid oxidation related to the use of butyrate as fuel. Additionally, butyrate might have increased transmethylation activity. This work represents an advance in the knowledge of the metabolic consequences of using butyrate as an additive in fish diets.

Effects of sub-lethal CO2(aq) concentrations on the performance of intensively reared gilthead seabream (Sparus aurata) in brackish water: Flow-through experiments and full-scale RAS results

The effects of sub-lethal CO2(aq) concentrations were tested for the first time on gilthead seabream (Sparus aurata) juveniles (4–25g; 64 growth days) and adult (∼300–400g; 71d) fish, both in fully controlled pilot tests and the latter also as part of full-scale RAS (recirculating aquaculture system) operation. In the pilot experiments (concentration range 5.2–56.3mg CO2/L) the specific growth rate, mortality rate, and physical fish disorders were monitored. In the full scale experiment, two groups of fish, originally from the same batch, were exposed for 197d to controlled (by NaOH dosage) and uncontrolled pH conditions, resulting in exposure of the fish to significantly different CO2(aq) concentrations. The pilot results showed, as expected, that the seabream fish grew faster at the lower CO2 concentrations and that the growth rate of both juveniles and adult fish was only minimally inhibited up to roughly 20mg CO2/L (compared to a previously published curve). Mortality rate was considerable only at the highest CO2 concentration (∼56mg CO2/L). Physical irregularities were not observed, apart from abnormally high absence of swim bladder at the highest CO2(aq) treatment. The (statistically significant) results from the full-scale RAS operation showed that growing gilthead seabream for 197d at roughly constant and relatively low (∼16mg/L) CO2(aq) concentration resulted in fish with ∼10% larger mean weight relative to the fish grown in ponds in which CO2(aq) was not controlled and its concentration fluctuated daily between 19 and 37mg/L.

High mortality of juvenile gilthead sea bream (Sparus aurata) from photobacteriosis is associated with alternative macrophage activation and anti-inflammatory response: Results of gene expression profiling of early responses in the head kidney

The halophilic bacterium Photobacterium damselae subsp. piscicida (Phdp) represents a substantial health problem for several fish species in aquaculture. Bacteria that reside free and inside phagocytes cause acute and chronic forms of photobacteriosis. Infections of juveniles rapidly kill up to 90–100% fish. Factors underlying failure of the immune protection against bacteria remain largely unknown. The reported study used a transcriptomic approach to address this issue. Juvenile sea breams (0.5 g) were challenged by immersion in salt water containing 2.89 × 108 CFU of a virulent Phdp and the head kidney was sampled after 24- and 48-h. Analyses were performed using the second version of a 44 k oligonucleotide DNA microarray that represents 19,734 sea bream unique transcripts and covers diverse immune pathways. Expression changes of selected immune genes were validated with qPCR. Results suggested rapid recognition of the pathogen, as testified by up-regulation of lectins and antibacterial proteins (bactericidal permeability-increasing protein lectins, lysozyme, intracellular and extracellular proteases), chemokines and chemokine receptors. Increased expression of proteins involved in iron and heme metabolism also could be a response against bacteria that are dependent on iron. However, negative regulators of immune/inflammatory response were preponderant among the up-regulated genes. A remarkable finding was the increased expression of IL-10 in concert with up-regulation of arginase I and II and proteins of the polyamine biosynthesis pathway that diverts the arginine flux from the production of reactive nitrogen species. Such expression changes are characteristic for alternatively activated macrophages that do not develop acute inflammatory responses. Immune suppression can be induced by the host to reduce tissue damages or by the pathogen to evade host response.

Environmental Conditioning of Skeletal Anomalies Typology and Frequency in Gilthead Seabream (Sparus aurata L., 1758) Juveniles

In this paper, 981 reared juveniles of gilthead seabream (Sparus aurata) were analysed, 721 of which were from a commercial hatchery located in Northern Italy (Venice, Italy) and 260 from the Hellenic Center for Marine Research (Crete, Greece). These individuals were from 4 different egg batches, for a total of 10 different lots. Each egg batch was split into two lots after hatching, and reared with two different methodologies: intensive and semi-intensive. All fish were subjected to processing for skeletal anomaly and meristic count analysis. The aims involved: (1) quantitatively and qualitatively analyzing whether differences in skeletal elements arise between siblings and, if so, what they are; (2) investigating if any skeletal bone tissue/ossification is specifically affected by changing environmental rearing conditions; and (3) contributing to the identification of the best practices for gilthead seabream larval rearing in order to lower the deformity rates, without selections. The results obtained in this study highlighted that: i) in all the semi-intensive lots, the bones having intramembranous ossification showed a consistently lower incidence of anomalies; ii) the same clear pattern was not observed in the skeletal elements whose ossification process requires a cartilaginous precursor. It is thus possible to ameliorate the morphological quality (by reducing the incidence of severe skeletal anomalies and the variability in meristic counts of dermal bones) of reared seabream juveniles by lowering the stocking densities (maximum 16 larvae/L) and increasing the volume of the hatchery rearing tanks (minimum 40 m3). Feeding larvae with a wide variety of live (wild) preys seems further to improve juvenile skeletal quality. Additionally, analysis of the morphological quality of juveniles reared under two different semi-intensive conditions, Mesocosm and Large Volumes, highlighted a somewhat greater capacity of Large Volumes to significantly augment the gap with siblings reared in intensive (conventional) modality.

Effects of Intensive and Semi-Intensive Rearing on Growth, Survival, and V-Shaped (Lordotic) Skeletal Deformities in Juvenile Gilthead Sea Bream (Sparus aurata)

Intensive production can reduce production costs and improve efficiency of larvae culture. This study compared the effects of intensive and semi-intensive production on growth, survival, and V-shaped skeletal deformities in juvenile gilthead sea bream (Sparus aurata). At the end of the 50-day study, survival was 68.01±0.8%, mean weight was 1.32±0.03 g, and lordosis was 32% among juveniles raised in the intensive system. Survival and mean weight were significantly higher, 92.06±1.1% and 1.61±0.02 g, respectively, among juveniles raised in the semi-intensive system, and none had lordosis (p&lt;0.05). Results suggest that semi-intensive systems are more advantageous than intensive for rearing sea bream juveniles.

Neuroglial Cells in Long-Term Primary Cultures from the Gilthead Seabream (Sparus Aurata L.): New Functional In Vitro Model from Bony Fish Brain

As its Greek name suggests, neuroglia is the glue of the nervous system, simply referred to as non-neuronal cells, with supporting functions for neurons in the central nervous system (CNS) of mammalian and lower vertebrates. Recent advances in stem cell biology have redefined new functions. In fish, neuroglial cells have been described as supporting cells, and as such require further investigation. Approximately 283 cell lines have been obtained from fish worldwide, yet none from the brain of Sparus aurata, neither in cell lines nor as primary culture. We describe a novel reproducible in vitro neuroglial marine model for establishing primary neuroglial cell cultures by dissociating the whole brain of seabream juveniles. Proliferating neural stem cells produced alongside three generating lineages (neuronal precursor cells, astroglial precursor cells and oligodendroglia precursor cells) developed neurons, astrocytes and oligodendrocytes, respectively. The radial glia, finely described by morphological studies and immunochemical antigen expression, showed a particular spatial distribution, giving rise simultaneously both to astrocytes and neuronal precursors within a highly proliferative assemblage. Radial glial cells were assessed by glial fibrillary acidic protein (GFAP) and vimentin reactivity, astrocytes by GFAP, neurons by the neuron-specific markers for ubiquitin carboxy-terminal hydrolase 1 (UCHL1) and intermediate filament associated protein (NF). Myelinating oligodendrocytes were immunostained with anti-myelin basic protein (MBP) and anti-O4. Findings suggest that seabream neuroglial cells at 3-4 weeks of culture proliferation acquire neuroglial differentiation and oligodendrocyte maturation with myelination, suggesting that mixed neuroglial cultures accelerate maturation of oligodendrocytes and regenerate CNS injury in fish.

Linking cortisol responsiveness and aggressive behaviour in gilthead seabream Sparus aurata: Indication of divergent coping styles

Farmed animals, including fish, often exhibit a pronounced individual variation in stress coping styles with proactive and reactive individuals differing in a variety of neuroendocrine and behavioural responses. In this study we disclosed that individual differences in cortisol responsiveness after a restraining test were predictive of aggressive behaviour in gilthead seabream Sparus aurata, one of the most important Mediterranean farmed fish. Seabream juveniles (n=24, initial weight: 49.3±7.3g) were exposed to a restraining test that consisted of keeping each fish in an emerged net for three minutes. Afterwards fish returned to their home tank and 30min after were rapidly caught and anaesthetised for blood sampling. Blood was collected from the caudal vein and analysed for cortisol (radioimmunoassay). After 3 months the same individuals were exposed to an aggression test: fish were allowed to interact with a naïve fish of similar size (max 10% weight difference) for 20min. Aggressive behaviour was determined as follows: latency to start chasing (time taken until the first chase; chase was defined as a sudden change in swimming direction and speed as a response to an approach by the opponent); number of chases; latency to fighting (time taken until the first fight; fight was defined when fish engaged in a circle movement around each other) and number of fights. Results showed that individuals exhibiting lower cortisol responsiveness after a restraining test were more aggressive (cortisol vs number of chases: rs=−0.479, p=0.021) In conclusion, seabream juveniles exhibited pronounced individual differences in cortisol responsiveness and aggression that are interrelated and likely to be distinctive traits of coping styles.

Proteomic evaluation of potentiated sulfa treatment on gilthead sea bream (Sparus aurata L.) liver

Potentiated sulfa drugs are a combination of sulfonamide and pyrimidine potentiators. They are currently used against fish bacterial pathogens in Mediterranean marine fish farming. The present work aimed studying the potential hepatotoxicity of a combination of sulfadiazine (SDZ) and trimethoprim (TMP) in gilthead sea bream juveniles after oral administration, at the recommended ratio of 5:1 (SDZ/TMP), equivalent to a dose of 30mgkg−1fishday−1, for 10days at 19°C temperature. Electrophoresis (DIGE) technology coupled with MS was used to identify possible markers of hepatotoxicity of this treatment. The results obtained show significant changes in the expression of 41 proteins by treatment (p≤0.02). Among these proteins, 14 increased in abundance, and 27 decreased with respect to the control group. Proteins showing differential expression with respect to the control were identified by PMF and/or LC-MS/MS and database research. Proteins like apolipoprotein A-I and fatty acid binding protein (lipid metabolism and transport, and antioxidant role), phosphoglucomutase 1 (carbohydrate metabolism), elongation factor 1-alpha (protein biosynthesis and antioxidant role), mitochondrial aldehyde dehydrogenase (oxidation regulation activity and antioxidant role) and ypbc-32-D06 (aminotransferases), were differentially expressed in treated fish. These proteins have not been associated before with potentiated sulfa effect in farmed fish. However, they are frequently found differentially expressed as a characteristic cellular/tissue stress response under different experimental conditions, making difficult their use as specific biomarkers for this treatment.

Effects of diet supplementation with white tea and methionine on lipid metabolism of gilthead sea bream juveniles (Sparus aurata)

A growth trial was performed with gilthead sea bream juveniles (Sparus aurata) to evaluate the effect of diet supplementation with white tea and methionine on fish performance and lipid metabolism. For that purpose, four diets were formulated: a fish meal-based diet (Control) and diets identical to the control diet but supplemented with 2.9% white tea (Tea), 0.3% methionine (Met) or 2.9% white tea plus 0.3% methionine (Tea+Met). Growth performance and feed efficiency parameters, whole-body and liver composition, plasma metabolites concentration and liver glucose 6-phosphate dehydrogenase (G6PDH), malic enzyme (ME) and fatty acid synthetase (FAS) activities were determined. Feed intake was higher in fish fed methionine-supplemented diets, whereas this parameter and growth was decreased in fish fed white tea supplementation. Feed efficiency and protein efficiency ratio were not affected by diet composition. Plasma HDL cholesterol and total lipids concentration were higher in fish fed white tea-supplemented diets. Whole-body lipid, plasma glucose, liver glycogen concentration and liver G6PDH, ME and FAS activities were lower in fish fed white tea-supplemented diets. Results of the present study indicate that methionine seems to act as a feed attractant in diets for sea bream juveniles. Additionally, white tea is an important modulator of lipid metabolism in sea bream juveniles.

Selected plasma biochemistry parameters in gilthead seabream (Sparus aurata) juveniles

Summary The aim of this study was to assess plasma biochemistry parameters with the potential of being used as indicators of the nutritional status for healthy gilthead seabream juveniles. Triplicate groups of 18 seabream (body weight of 58 g) were kept unfed for 24 h, 7 or 14 days. Nine fish per treatment were then sampled randomly for blood collection and the following parameters analyzed in the plasma using standard clinical methods: glucose; protein; triglycerides; cholesterol; calcium; magnesium; inorganic phosphorus; alkaline phosphatase (ALP); aspartate aminotransferase (AST); lactate dehydrogenase (LDH); gamma-glutamyl transferase (GGT); creatine phosphokinase (CPK); and lipase. Biochemical parameters showed lower variability among individuals than did enzymatic parameters. Plasma glucose, protein, cholesterol, calcium and inorganic phosphorus levels were inversely related to the duration of starvation. On the contrary, plasma triglycerides decreased significantly during the first week of starvation and remained stable in the second week. Plasma ALP, AST and LDH decreased significantly after 1 week of starvation and then remained constant. In healthy seabream juveniles, plasma glucose, protein, cholesterol, calcium and inorganic phosphorus are responsive to starvation and may be useful indicators of the nutritional status of the animals. Indicative baseline reference values for gilthead seabream juveniles starved for 24 h and held at optimum temperature are: protein, 3.7–4.9 g dl−1; cholesterol, 341–407 mg dl−1; calcium, 13.1–8.0 mg dl−1; and inorganic phosphorus, 10–14.2 mg dl−1. Plasma triglycerides, along with plasma enzyme activities, may be useful as indicators of short term starvation. For these parameters baseline values after 1 week of starvation were: triglycerides: 138–230 mg dl−1; ALP: 58–125 U L−1; AST: 15–127 U L−1; and LDH 61–677 U L−1. Plasma glucose is only responsive to longer starvation periods, remaining relatively stable during the first week of starvation, and ranging from 59 to 196 mg dl−1.