Gilthead Seabream Larvae Growth and Survival Using New Co‐Feeding Regimes With Early Microdiet Application

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.

Vitamin D is an essential fat soluble micronutrient that helps in growth, bone development, calcium homeostasis and other metabolic process. The study on effect of vitamin D3 in marine fish larvae were very scarce irrespective of species. The present study determines the impacts of dietary vitamin D3 on growth performance, calcium absorption, mineralization, and skeletal anomalies during the development of gilthead seabream (Sparus aurata) larvae was assessed until 47 days post hatching. Diets containing four levels of vitamin D3 (0, 25, 30, 384 μg kg−1 or 11.6, 1000, 1200, 15,360 IU kg−1) were formulated to determine the effect of vitamin D3 at deficient, excess, and optimum levels. The gilthead seabream larvae in the present study fed with this wide range of vitamin D3 presented a constant growth with all the diets but presented signs of toxicity in excess level, affecting the survival, calcium uptake, and bone biomarker mechanism in larvae, which resulted in increased skeletal anomalies and mortality. An increase of dietary vitamin D3 up to 384 μg kg−1 significantly raised the whole body vitamin D3 content, calcium, and phosphorus intake and increased the incidence of skeletal anomalies, particularly cranial anomalies. The appearance of skeletal anomalies in larvae fed 384 μg kg−1 vitamin D3 was in association with the upregulation of bmp2, alp, and oc gene expression. However, larvae fed 0, 25, 30 μg kg−1 vitamin D3 showed higher survival than the group fed 384 μg kg−1 vitamin D3. Meanwhile vitamin D3 deficient diet 0 μg kg−1 presented with lower mineralization rate and increase incidence of maxillary anomaly. Thus, the current study revealed the evidence of vitamin D3 deficiency as well as toxicity in gilthead seabream larvae during the developmental process and conclude that the recommended dietary vitamin D3 level for gilthead seabream larvae may range between 25 and 30 μg kg−1 which improves larval survival, calcium and phosphate level and vertebral mineralization with reduced incidence of skeletal anomalies in gilthead seabream larvae

Riboflavin enrichment throughout the food chain from the marine microalga Tetraselmis suecica to the rotifer Brachionus plicatilis and to White Sea Bream ( Diplodus sargus) and Gilthead Sea bream ( Sparus aurata) larvae

Effects of the dietary supplementation of manganese on growth, skeletal development, oxidative stress and bone metabolism related genes in gilthead seabream (Sparus aurata) larvae

Viral nervous necrosis outbreaks caused by the RGNNV/SJNNV reassortant betanodavirus in gilthead sea bream (Sparus aurata) and European sea bass (Dicentrarchus labrax)

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.

Diurnal patterns of tryptic enzyme activity under different feeding regimes in gilthead sea bream (Sparus aurata) larvae

Developing eggs and larvae of laboratory-reared gilthead sea bream (Sparus aurata) maintained in filtered seawater (40 ppt) at 18°C, were measured for oxygen uptake, ammonia excretion, contents of free amino acids (FAA), protein, fatty acids (FA) accumulated ammonia, and volumes of yolk-sac and oil globule. Absorption of the yolk coincided with the consumption of FAA and was complete ca. 100 h post-fertilisation. Amino acids from protein were mobilised for energy in the last part of the yolk-sac stage. Absorption of the oil globule occurred primarily after hatching following yolk absorption, and correlated with catabolism of the FA neutral lipids. Overall, FAA appear to be a significant energy substrate during the egg stage (60 to 70%) while FA from neutral lipids derived from the oil globule are the main metabolic fuel after hatching (80 to 90%).

Currently, the larviculture of many marine fish species with small-sized larvae depends for a short time after hatching, on the supply of high-quality live zooplankton to ensure high survival and growth rates. During the last few decades, the research community has made great efforts to develop artificial diets, which can completely substitute live prey. However, studies aimed at determining optimal levels of minerals in marine larvae compound feeds and the potential of novel delivery vectors for mineral acquisition has only very recently begun. Recently, the agro-food industry has developed several nano-delivery systems, which could be used for animal feed, too. Delivery through nano-encapsulation of minerals and feed additives would protect the bioactive molecules during feed manufacturing and fish feeding and allow an efficient acquisition of active substances into biological system. The idea is that dietary minerals in the form of nanoparticles may enter cells more easily than their larger counterparts enter and thus speed up their assimilation in fish. Accordingly, we evaluated the efficacy of early weaning diets fortified with organic, inorganic, or nanoparticle forms of trace minerals (Se, Zn, and Mn) in gilthead seabream (Sparus aurata) larvae. We tested four experimental diets: a trace mineral-deficient control diet, and three diets supplemented with different forms of trace minerals. At the end of the feeding trial, larvae growth performance and ossification, and the level of expression of six target genes (SLC11A2β, dmt1, BMP2, OC, SOD, GPX), were evaluated. Our data demonstrated that weaning diets supplemented with Mn, Se, and Zn in amino acid-chelated (organic) or nanoparticle form were more effective than diets supplemented with inorganic form of minerals to promote bone mineralization, and prevent skeletal anomalies in seabream larvae. Furthermore, nanometals markedly improved larval stress resistance in comparison to inorganic minerals and upregulated mRNA copy number of OC gene. The expression of this gene was strongly correlated with mineralization degree, thus confirming its potency as a good marker of bone mineralization in gilthead seabream larvae.

The effect of dietary copper (Cu) levels on growth, oxidative stress, fatty acid profile and bone health of gilthead seabream larvae (Sparus aurata) was studied in 47 days-post-hatching fish fed 4 experimental diets containing 17, 18, 19 and 25 mg Cu/kg diet. After 21 days of feeding, larval growth and survival were not affected by the dietary Cu levels. However, larvae fed the non-supplemented diet (17 mg Cu/kg) showed clear symptoms of Cu deficiency, including increased lipid peroxidation and reduced bone mineralization. Increased peroxidation risk caused a reduction in essential fatty acids and n-3 PUFA (polyunsaturated fatty acids) contents in whole body lipids, whereas the poor vertebral body mineralization in seabream larvae was related to a marked increase in abdominal vertebrae anomalies. On the contrary, dietary Cu supplementation raised whole-body contents in DHA, EPA and n-3 PUFA and reduced MUFA, TBARS and the incidence of severe, cranial, branchiostegal rays and abdominal vertebral anomalies. Polynomial regression models applied to all these parameters suggested optimum dietary Cu levels to be 21.5–22.6 mg/kg in gilthead seabream larvae microdiets supplemented with CuSO4.5H2O. These levels (21.5–22.6 mg/kg) are in the range of the Cu contents in copepods (12–38 mg/kg) and on the verge of the dietary levels authorized by EU Commission in feeds for cultured fish species (25 mg Cu/kg diet).

The high prevalence of opercular deformities present in fish from Mediterranean marine hatcheries is an important problem, which is causing considerable economic losses. The aetiology of this syndrome is not yet well understood. In this study a histological and ultrastructural description of gilthead sea bream (Sparus aurata) larvae affected with anomalies of the opercular complex was carried out.

The effect of dietary phosphatidylcholine on the assimilation and distribution of ingested free oleic acid (18:1 n−9) in gilthead seabream ( Sparus aurata) larvae

Consumption vs. deposition of essential fatty acids in gilthead sea bream ( Sparus aurata) larvae fed semi-purified diets

Consumption vs. deposition of essential fatty acids in gilthead sea bream (Sparus aurata) larvae fed semi-purified diets

The digestive enzymes and hormones of gilthead seabream (Sparus aurata) larvae fed live prey (Artemia nauplii) enriched with free histidine were investigated for 16 days (from day 24 to day 40 after hatching). Larvae were sampled at 4-day intervals. The control group had significantly lower growth than the enriched group (p&lt;0.05). Trypsin activity was higher in the control (p&lt;0.05). Bombesin activity significantly differed between treatments, periods, and period x treatment interac- tions and the cholecystokinin level was significantly higher in the enriched groups (p&lt;0.05). Results indicate that Artemia nauplii can successfully be enriched with free histidine, bombesin and chole- cystokinin activity can be stimulated by free histidine, and mechanisms controlling the adaptation of trypsin activity to the amount of dietary protein were not activated within the 40-day study period.