Unveiling the Impact of Hydroxyproline Supplementation Diet on Haemato-biochemical Aspects of Gilthead Seabream (Sparus aurata) Exposed to Ammonia Challenge Under Different Stocking Densities

Simple SummaryThe development of skeletal anomalies in the early life stage of gilthead seabream (Sparus aurata) poses a significant challenge for farmers, affecting their profit margins, animal welfare, and the consumers’ perception of the aquaculture industry. Although many factors have been considered to be causative in the development of skeletal anomalies in marine finfish, the stocking density and available swimming space represent two key parameters which can be easily manipulated by the farmers during the critical phase of pre-ongrowing (prior to being placed in sea cages). This work aims at distinguishing which among tank volume and stocking density is the driving factor eliciting the development of skeletal anomalies during the pre-ongrowing phase in gilthead seabream, a productive cycle in which many skeletal anomalies can arise, particularly those affecting the vertebral axis. The results from this work indicated that particular cranial and axis deformities affected fish in higher incidences when they were reared at higher densities. The results are discussed through an eco-evo-devo approach in relation to the potential mechanisms at play affecting the increased prevalence of skeletal anomalies found. This research represents an intriguing contribution to aquaculture with results that can be applied directly to the production methods used by fish farmers to ameliorate the skeletal and morphological quality of farmed gilthead seabream.Gilthead seabream (Sparus aurata) production is a highly valued aquaculture industry in Europe. The presence of skeletal deformities in farmed gilthead seabream represents a major bottleneck for the industry leading to economic losses, negative impacts on the consumers’ perception of aquaculture, and animal welfare issues for the fish. Although past work has primarily focused on the hatchery phase to reduce the incidence of skeletal anomalies, this work targets the successive pre-ongrowing phase in which more severe anomalies affecting the external shape often arise. This work aimed to test the effects of: (i) larger and smaller tank volumes, stocked at the same density; and (ii) higher and lower stocking densities maintained in the same water volume, on the skeleton of gilthead seabream fingerlings reared for ~63 days at a pilot scale. Experimental rearing was conducted with gilthead seabream juveniles (~6.7 ± 2.5 g), which were selected as ‘non-deformed’ based on external inspection, stocked at three different densities (Low Density (LD): 5 kg/m3; Medium Density (MD): 10 kg/m3; High Density (HD): 20 kg/m3) in both 500 L and 1000 L tanks. Gilthead seabream were sampled for growth performance and radiographed to assess the skeletal elements at the beginning and end of the experimental trial. Results revealed that (i) LD fish were significantly longer than HD fish, although there were no differences in final weights, regardless of the water volume; (ii) an increase in the prevalence of seabream exhibiting cranial and vertebral axis anomalies was found to be associated with increased density. These results suggest that farmers can significantly reduce the presence of some cranial and axis anomalies affecting pre-ongrown gilthead seabream by reducing the stocking density.

Effects of dietary tryptophan and chronic stress in gilthead seabream (Sparus aurata) juveniles fed corn distillers dried grains with solubles (DDGS) based diets

Simple SummaryFarmed fish must cope with different stressors during aquaculture procedures, such as high densities, fasting, transport, or air exposure during handling. The severity and timing of these stressors can produce important imbalances in the overall status of the animals, triggering several endocrine and physiological players. In this study, gilthead sea bream (Sparus aurata) juveniles were assigned to four experimental conditions: (1) fed at a low stocking density (LSD-F, 4 kg·m−3); (2) fed at a high stocking density (HSD-F, 40 kg·m−3); (3) food-deprived at LSD (LSD-FD); and (4) food-deprived at HSD (HSD-FD). This served to evaluate, both at the plasma and central (brain) levels, the role of several hormonal (cortisol and catecholamines) and monoamine (dopaminergic and serotonergic neurotransmitters) functionalities. Our results evidenced chronic stress exposure (i.e., a high stocking density and food deprivation) fallouts in the enhancement of the parameters related to the stress response, where monoaminergic activities in different brain regions served to reorganize the physiological response depending on the challenge applied.In teleosts, brain monoamines (dopamine and serotonin) participate in the early response to different acute stressors. However, little is known regarding their role during chronic stress. In a 2 × 2 factorial design, the influence of a high stocking density (HSD) and/or food deprivation (FD) on the brain monoaminergic activity in gilthead sea bream (Sparus aurata) was evaluated. Following a 21-day experimental design, samples from the plasma and brain regions (telencephalon, hypothalamus, and optic tectum) were collected. The dopamine (DA), serotonin (5HT), and their main metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and 5 hydroxyindoleacetic acid (5HIAA), contents were HPLC-assessed in brain tissues, and the ratios DOPAC/DA and 5HIAA/5HT were calculated as indicators of enhanced monoaminergic activity. The plasma levels of cortisol and catecholamine were also evaluated. The cortisol levels increased in fish exposed to HSD and normally fed but, also, in all FD groups, whereas the NA levels decreased in LSD-FD animals. Within the brain, the dopaminergic and serotonergic activities in telencephalon and hypothalamus increased in fish subjected to HSD and in the telencephalon of LSD-FD fish. While DA (hypothalamus) and 5HT (telencephalon) increased in the animals submitted to a HSD, food-deprived fish did not show such an increase. Taken together, our results supported the hypothesis of brain monoaminergic activity participating in maintaining and orchestrating the endocrine response to chronic stress in fish.

Stocking density is considered a priority topic in aquaculture research due to its bearing on the welfare of farmed fish and the need for future recommendations governing stocking density management on fish farms. The aim of this study was to evaluate the influence of stocking density (10, 20, 30 and 40 fry/L3) on growth performance, Feed utilization and survival rate of fry gilthead seabream (Sparus aurata). The results showed that the group of fry stocked at density 30 fry/ L3 was significantly the highest final weight, weight gain, daily gain, SGR and insignificant differences in survival rate. Growth performance parameters were the highest with stocking density 30 fry/ L3 compared with stocking density (10, 20 and 40 fry/ L3), respectively. The results indicated that the best FCR, PER and FE group of fry stocked at 30 fry/ L3 than the rest of experimental groups. Stocking density also did not affect the crude protein and moisture content in body composition. But ash content was significantly highest at density 30 fry/ L3 than the rest of other stocking density (10. 20 and 40 fry/L3) groups. In contrast, total lipid was significantly highest at density 10 fry/L3 than the rest of experimental groups (20, 30 and 40 fry/L3). From the aforementioned results, it could be concluded that stocking density 30 fry/L3 had the best growth performance and feed utilization under experimental conditions.

A natural additive in the diet to improve growth and reduce energy expenditure of gilthead seabream (Sparus aurata L.): Attenuation of high stocking density stress responses

Linking stocking densities and feeding strategies with social and individual stress responses on gilthead seabream (Sparus aurata)

Behavioral and physiological responses to stocking density in sea bream (Sparus aurata): Do coping styles matter?

Two different O2 levels (normoxia: 75–85% O2 saturation; moderate hypoxia: 42–43% O2 saturation) and stocking densities (LD: 9.5, and HD: 19 kg/m3) were assessed on gilthead sea bream (Sparus aurata) in a 3-week feeding trial. Reduced O2 availability had a negative impact on feed intake and growth rates, which was exacerbated by HD despite of the improvement in feed efficiency. Blood physiological hallmarks disclosed the enhancement in O2-carrying capacity in fish maintained under moderate hypoxia. This feature was related to a hypo-metabolic state to cope with a chronic and widespread environmental O2 reduction, which was accompanied by a differential regulation of circulating cortisol and growth hormone levels. Customized PCR-arrays were used for the simultaneous gene expression profiling of 34–44 selected stress and metabolic markers in liver, white skeletal muscle, heart, and blood cells. The number of differentially expressed genes ranged between 22 and 19 in liver, heart, and white skeletal muscle to 5 in total blood cells. Partial Least-Squares Discriminant Analysis (PLS-DA) explained [R2Y(cum)] and predicted [Q2Y(cum)] up to 95 and 65% of total variance, respectively. The first component (R2Y = 0.2889) gathered fish on the basis of O2 availability, and liver and cardiac genes on the category of energy sensing and oxidative metabolism (cs, hif-1α, pgc1α, pgc1β, sirts 1-2-4-5-6-7), antioxidant defense and tissue repair (prdx5, sod2, mortalin, gpx4, gr, grp-170, and prdx3) and oxidative phosphorylation (nd2, nd5, and coxi) highly contributed to this separation. The second component (R2Y = 0.2927) differentiated normoxic fish at different stocking densities, and the white muscle clearly promoted this separation by a high over-representation of genes related to GH/IGF system (ghr-i, igfbp6b, igfbp5b, insr, igfbp3, and igf-i). The third component (R2Y = 0.2542) discriminated the effect of stocking density in fish exposed to moderate hypoxia by means of hepatic fatty acid desaturases (fads2, scd1a, and scd1b) and muscle markers of fatty acid oxidation (cpt1a). All these findings disclose the different contribution of analyzed tissues (liver ≥ heart > muscle > blood) and specific genes to the hypoxic- and crowding stress-mediated responses. This study will contribute to better explain and understand the different stress resilience of farmed fish across individuals and species.

A confinement stress test with 75% tank space reduction and behavioural monitoring through tri-axial accelerometers externally attached to the operculum was designed. This procedure was validated by demonstrating the less pronounced stress response in gilthead sea bream than in European sea bass (950-1200 g). Our study aimed to assess habituation to high stocking densities with such procedure in gilthead sea bream. Animals (420-450 g) were reared (June-August) in a flow-through system at two stocking densities (CTRL: 10-15 kg/m3; HD: 18-24 kg/m3), with natural photoperiod and temperature (21-29 °C), and oxygen levels at 5.2-4.2 (CTRL) and 4.2-3.2 ppm (HD). At the end, blood and muscle were sampled for haematology and transcriptomic analyses, and external tissue damage was assessed by image-based scoring. Four days later, fish underwent a 45 min confinement stress test over two consecutive days. HD fish showed reduced feed intake, growth rates and haematopoietic activity. Muscle transcriptome changes indicated a shift from systemic to local growth regulation and a primed muscle regeneration over protein accretion in HD animals with slight external injuries. After stress testing, HD fish exhibited a decreased recovery time in activity and respiration rates, which was shorter after a second stressor exposure, confirming habituation to high densities.

This study was conducted at the Fish Rearing Lab. at El-Mex Applied Research Station of the National Institute of Oceanography and Fisheries in Alexandria in 2015, in cooperation with the Faculty of Agriculture - Menoufia University, in order to carry out nutritional studies on some intensive marine culture techniques especially for Gilthead sea bream (Sparus aurata). The present work included three experiments on fry and fingerlings of Gilthead sea bream to study: O The effect of nursing methods and stocking density on the nursing of Gilthead sea bream using underground saline water. O The effect of some feed additives on the growth performance, dietary benefits and consumption of Gilthead sea bream, hapas or net-enclosures. O Effect of integrated multi-species culture on the performance parameters of Gilthead sea bream fingerlings. From the results of the three previous experiments, the following can be concluded: Nursing of Gilthead sea bream fish is better in hapas than in fiberglass tanks. The best density of gilthead sea bream fish culture is 100 fish / 2 m3. The addition of Aquagest® OMF (OA) as a source of organic acids to the Gilthead sea bream has improved its rate of growth and nutritional utilization compared to control treatment. Integrated multi-tropic Aquaculture (IMTA) systems improved the growth performance, feed utilization and condition factor of gilthead sea bream fish and obtained additional production of mullet and bivalves as well as increasing the economic yield of the farmer, thus achieving optimal utilization of the unit area (land and water).

Effect of vitamin E and C dietary supplementation on some immune parameters of gilthead seabream ( Sparus aurata) juveniles subjected to crowding stress

Simple SummaryA fungal toxin, aflatoxin B1 (AFB1), undermines growth and stress axes of gilthead seabream (Sparus aurata) with depletion of somatic carbohydrate and lipid reservoirs. The present study assessed the physiological consequences of high stocking density versus low stocking density in seabream juveniles, which had previously been fed with AFB1 supplementation. These stressors are likely to converge by inferring animal welfare and economic profitability in the food animal industry. Interestingly, AFB1 seems to cause physiological and molecular dysfunction in response to overcrowding densities. Our results might be relevant to elucidate a potential risk for fish farming that is often overlooked.Several studies in fish have shown that aflatoxin B1 (AFB1) causes a disparity of species-dependent physiological disorders without compromising survival. We studied the effect of dietary administration of AFB1 (2 mg AFB1 kg−1 diet) in gilthead seabream (Sparus aurata) juveniles in combination with a challenge by stocking density (4 vs. 40 g L−1). The experimental period duration was ten days, and the diet with AFB1 was administered to the fish for 85 days prior to the stocking density challenge. Our results indicated an alteration in the carbohydrate and lipid metabolites mobilization in the AFB1 fed group, which was intensified at high stocking density (HSD). The CT group at HSD increased plasma cortisol levels, as expected, whereas the AFB1-HSD group did not. The star mRNA expression, an enzyme involved in cortisol synthesis in the head kidney, presented a ninefold increase in the AFB1 group at low stocking density (LSD) compared to the CT-LSD group. Adenohypophyseal gh mRNA expression increased in the AFB1-HSD but not in the CT-HSD group. Overall, these results confirmed that chronic AFB1 dietary exposure alters the adequate endocrinological physiological cascade response in S. aurata, compromising the expected stress response to an additional stressor, such as overcrowding.

This study was conducted to investigate the effect of adding either brewer yeast as a probiotic, iodine or thyroxin with yeast as synbiotics to sea bream (Sparus aurata)fingerlings diets on; growth performance, feed utilization, body composition, biometric measurements indices and some serum constituents of sea bream. Acclimatized fish were randomly distributed in 12 glass aquaria and stocking density was 15 fish per aquarium with an average weight 1.9±0.1 g/fish as triplicate groups per treatment. The 1st group was considered as a control which fed on the basal diet (C). Three tested diets are formulated by adding 2g yeast/kg diet (Y), 2g yeast+0.01g potassium iodide/kg diet (YI) and 2g yeast+0.05 g thyroxin /kg diet (YT4) respectively for second, third and fourth groups. In the present work, addition of yeast with thyroxin followed by yeast alone to sea bream (Sparus aurata) fingerlings diets significantly improve growth performance, feed utilization efficiency and the fish biochemical composition comparing with the control one. The lowest growth performance and feed utilization values were recorded in fish fed diet supplemented with iodine when compared with corresponding values in fish of control group. Results of biometric measurements showed that adding iodine to fish diet significantly reduced gut length. Adding either iodine or thyroxin significantly increased serum lipase and decreased amylase contents.

Humoral immunomodulation of the gilthead seabream (Sparus aurata L.) subjected to long-term crowding stress

Effects of rearing density on growth, digestive conditions, welfare indicators and gut bacterial community of gilthead sea bream (Sparus aurata, L. 1758) fed different fishmeal and fish oil dietary levels