Effect of Organic Plant Ingredients on the Growth Performance of European Sea Bass (Dicentrarchus labrax): Nutritional Efficiency, Fillet Nutritional Indexes, Purchase Intention, and Economic Analysis

Effect of the dietary essential amino acid pattern on growth, feed utilization and nitrogen metabolism of European sea bass ( Dicentrarchus labrax)

Simple SummaryThis study explores the use of organic ingredients as protein sources in the diet of juvenile organic seabass. Various diets, including organic options like insect meal, Iberian pig byproduct, and rainbow trout meal byproduct, were compared to a control diet using conventional fishmeal. The research found that the control diet produced the best growth rates, and histological analysis indicated certain differences. While organic ingredients promise to replace fishmeal in aquaculture diets, further investigation is needed to achieve a complete substitution.The use of organic ingredients as a source of protein in aquaculture diets has gained significant attention due to the growing demand for organic seafood products. This study aimed to evaluate the potential for the use of organic ingredients as protein sources in the diet of juvenile organic seabass (Dicentrarchus labrax). A total of 486 juvenile seabass with an average weight of 90 g were fed six diets containing varied organic proteins. The control group (CON) was fed a diet with conventional fishmeal from sustainable fisheries as the primary protein source. The other five groups were fed diets with different compositions: organic Iberian pig meal byproduct (IB diet), a combination of organic Iberian pig meal byproduct and insect meal (IB-IN diet), a mix of organic Iberian pig meal byproduct and organic rainbow trout meal byproduct (IB-TR diet), a blend of organic rainbow trout meal byproduct and insect meal (TR-IN), and a mixed diet containing all of these protein sources (MIX diet). Over a 125-day feeding trial, growth performance, feed utilisation, feed digestibility, and histological parameters were assessed. The results showed that the fish fed the control diet had the highest final weight and specific growth rate, followed by the fish fed the TR-IN and IB-TR diets. The IB-TR diet had the highest apparent digestibility coefficients (ADCs) for protein, while the TR-IN diet had the lowest. Histological analysis revealed that fish fed the control diet had the largest nucleus diameter and hepatocyte diameter. Use of IN seems to penalise performance in several ways. Fish fed diets containing insect meal grew less, and those diets had lower digestibility. Fish fed the TR and IB diets grew at rates near that of the control, and the feed had acceptable digestibility.

SummaryThe effects of dietary fatty acids and seasonal variation on the fatty acid profiles of farmed and wild sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) were determined by analysis of their fillets. Farmed sea bream and sea bass were fed on the same commercial feeds all year. Fatty acid profiles in the fillets reflected the fatty acid profiles of the commercial feeds. The predominant fatty acids in the trial feeds, fillets of farmed and wild sea bream and sea bass were 16:0, 18:1n‐9, 18:2n‐6, 20:5n‐3 and 22:6n‐3. The fatty acid profiles in the fillets of farmed sea bream and sea bass did not differ (P > 0.05) except in the winter season compared with those of their wild counterparts. However, the content of eicosapentaenoic acid (20:5n‐3), docosahexaenoic acid (22:6n‐3) in the fillets of the farmed and wild sea bass were significantly (P < 0.05) higher than the farmed and wild sea bream. The wild sea bream had significantly (P < 0.05) higher total saturated fatty acid and monounsaturated fatty acid (MUFA) levels, and lower total n‐6 and n‐3 polyunsaturated fatty acid (PUFA) levels in winter than in the summer and spring seasons. Similarly, in the fillets of wild sea bass, total n‐3 PUFA levels were significantly (P < 0.05) lower, and the MUFA levels were higher in winter than in the other seasons. These results indicate that the farmed fish fillets were good sources of n‐3 PUFA in each of the three seasons. However, wild fish were good sources of n‐3 PUFA in the spring and summer.

The effects of either taurine (T) or sodium diformate (NDF) supplementation to a low fishmeal (FM) plant-based diet on growth, health status, immunity and muscle cellularity of European sea bass, Dicentrarchus labrax, were investigated. Four isoproteic (44% CP) and isolipidic (17% L) diets were produced to contain 46% FM as a control diet, or 20% FM and a mixture of plant nutrients (PMX). The plant-mix diets were either supplemented or not with 1% T or 0.3% NDF. Each diet was fed to triplicate groups of seabass (mean, 13.71 g) for 13 weeks. Fish fed the PMX diet supplemented with T or NDF was recorded to have a significantly higher feed intake, weight gain and a better feed conversion rate than other groups. The diet composition did not significantly alter the biochemical or essential amino acid composition of fish, except for the slightly reduced lipid content of T-fed fish in comparison to the PMX-fed fish. These supplements further enhanced blood profile, immunity response and myocytes ultrastructure relative to fish fed the PMX diet. Accordingly, these results suggest that supplementation of low-FM/plant-mix diet with either 1% T or 0.3% NDF can promote growth, normalize physiological conditions and improve the striated muscle structure of juvenile seabass.

The study involved three groups of six broodstock with a 1:1 male-to-female ratio. They were injected with 13 µg/kg LHRHa to stimulate spawning. We fed the broodstock three diets: a control diet without selenium, a diet containing 0.3 mg of nano-selenium /kg (N-Se), and a diet containing 4 mg of organic selenium /kg (O-Se). The broodstock diet consisted of equal parts of dry feed (45% protein), sardines, and squid. After being laid, the eggs were obtained from the collection ponds at the General Authority for Fisheries Development's fish hatchery and incubated until hatching. The larvae were given a micro diet containing 51.7% crude protein and live food (Rotifer and Artemia). Rotifer density increased from 5/ml to 15/ml by day 22 dph, Artemia nauplii increased from 0.2 to 4 ind./ml, from 7 to 35 dph then decreased to 0 at 55 dph, and micro-diets increased from 100-200 µ at 16 dph to 200-400 µ at 23-40 dph to 300-500 µ at 55 dph, and 500-1000 µ until the experiment ended. Three different diets in three replicates were tested: A micro diet free of selenium as a control diet (C), A micro diet with 0.3 mg of nano selenium (N-Se) kg-1, and A micro diet supplemented with organic selenium 4 mg (O-Se). Each group was taken from the three Broodstock groups respectively. Sixteen days after hatching, the three experimental micro diets were introduced to the larvae and continued for 76 days post-hatch. Larvae (260,000 per tank) were placed in fiberglass tanks with 4 m3 of water at a temperature of 19±2°C for optimal conditions. The larvae fed the N-Se diet had significantly better survival rates (75.0 ± 1.2 %), final body weight (240.0 ± 5.8 mg), weight gain (239.00 ± 5.8 mg), average daily gain (3.98±0.1mg), total length (39.0±0.06 mm), specific growth rate (9.133±0.04 %/day), feed intake (471.67±0.01 mg), and better feed conversion ratio (1.97±0.01) than the other groups (P < 0.05). The group provided with N-Se also had the highest levels of glutathione peroxidase enzyme (GPx) content in the whole larval body, whereas the control diet without Se supplementation recorded the lowest value of (14.8 ± 0.1 U/mg protein). The number and length of folds in the stomach and esophagus of sea bass post-larvae fed on diets fortified with selenium in both forms, nanoparticles or organic, showed a significant (P < 0.05) enhancement on the larval gastrointestinal (GI) tract. Moreover, selenium has an anti-inflammatory action in sea bass post-larvae. This study concluded that using N-Se as an antioxidant supports the growth and survival of European seabass D. labrax, gastrointestinal development and antioxidant efficacy during critical weaning.

Tenebrio molitor meal in diets for European sea bass (Dicentrarchus labrax L.) juveniles: Growth performance, whole body composition and in vivo apparent digestibility

Effects of feeding low fishmeal diets with increasing soybean meal levels on growth, gut histology and plasma biochemistry of sea bass

Supplementation of arachidonic acid rich oil in European sea bass juveniles (Dicentrarchus labrax) diets: Effects on leucocytes and plasma fatty acid profiles, selected immune parameters and circulating prostaglandins levels

Effect of feed supplementation with Origanum vulgare L. essential oil on sea bass (Dicentrarchus labrax): A preliminary framework on metabolic status and growth performances

A sustainable growth of the aquaculture sector implies the use of sustainable novel raw materials as replacers of the traditional fishmeal (FM) and fish oil (FO) ingredients. This fact has led to the development of sustainable and functional diets as part of a management strategy to reduce the effects on fish growth performance and health derived from low FM/FO dietary contents. In this sense, Antarctic krill (Euphausia superba) is considered a potential candidate in dietary inclusions to potentiate fish growth and health status. In this study, European sea bass (Dicentrarchus labrax) were fed a practical diet with either a 15% fishmeal content (KM0; control diet) or the same diet substituted by 30% (KM5; 50 g KM/kg diet) or 50% (KM7.5; 75 g KM/kg diet) Antarctic krill meal (KM) for 12 weeks in triplicates. At the end of the feeding trial, growth performance, liver morphology, liver proximate composition, lipid classes and fatty acid profiles, as well as the expression of hepatic genes related with lipid metabolism were evaluated. Fish fed KM-based diets presented higher (p < 0.05) final weight, protein and lipid efficiency ratios, specific growth rate (SGR) and improved feed conversion ratio (FCR), irrespective of the KM dietary level. Whole body and muscle proximate composition and fatty acid profiles were similar among dietary groups. Livers of European sea bass fed the experimental diets presented similar (p > 0.05) biochemical composition and fatty acid profile. However, smaller hepatocellular area and lower grade of cytoplasm vacuolization as well as a better alignment around sinusoidal spaces were found. The analyses of liver lipid classes revealed a positive correlation between the level of dietary KM and the pigmented material such as astaxanthin and free fatty acid content, as well as a negative correlation with the cholesterol levels. The expression of hepatic genes studied demonstrated a downregulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (hmgr) and delta-6-desaturase (fads2) expression levels in fish fed KM-based diets. Besides, gene expression levels of fatty acid binding protein 7 (fabp7) and lipoprotein lipase (lpl) were significantly correlated with KM dietary levels. Altogether, these results profile KM as a potential promoter of growth and liver health in European sea bass fed low fish meal and oil diets.

Growth of European sea bass ( Dicentrarchus labrax L.) under hypoxic and oscillating oxygen conditions

The aim of the present study was the investigation of the biological cycle of the isopod parasite Ceratothoa oestroides (Risso, 1836), the way of installation in the host and the study of its pathology in young individuals of gilthead sea bream {Sparus aurata) and sea bass {Dicentrarchus labrax) raised in experimental aquariums. During the experiment, initially, 10 sea bass of marketable size (300-400gr) were collected infected with lice from the region of Chios and Epidavros. The lice were mature and gravid. The adults and their hosts were kept in 151t aquariums, with constant water of 32-33%c salinity at temperature of 21-22° C, until they would give both to young parasites. The time that parasites stayed in aquarium was three months. After three months, new hatched larvae appeared. The pulii II stage, which was responsible for the most alterations that were observed in the fish and particular in sea bass, were observed in the first week, after the hatching. In this stage, parasites swam freely in the surface of water column. At this phase, 100 parasites were transported in 2 different aquariums with the same conditions of salinity and temperature as in the first aquarium, where young uninfected individuals (3-5 gr) of gilthead sea bream {Sparus aurata) and sea bass {Dicentrarchus labrax) were placed. The number of the uninfected, healthy fish was 40 individuals per aquarium. During the duration of experiment four weekly samplings of five individuals per sample were performed and these underwent a macroscopical, parasitological and histopathological examination. In addition, the mortalities that existed and the final luck of parasites afterwards the death of their hosts were recorded. From the results, we concluded that pulii II stage caused serious lesions and eventually the death of mainly young fish, gilthead sea bream {Sparus aurata) and sea bass {Dicentrarchus labrax). The process from the moment of "invasion" of young parasites until their final installation in the buccal cavity lasted around 2 hours. In one week, all the isopods were installed in the buccal cavity of young gilthead sea bream {Sparus aurata) and sea bass {Dicentrarchus labrax). During the second week, the first symptoms of fish appeared. The infected fish swam fast and rubbed their body against the aquarium surface in order to remove the parasites. In the sea bass {Dicentrarchus labrax), with the appearance of first symptoms, the biggest rate of mortality (56,25%) followed, while in the gilthead sea bream {Sparus aurata), the biggest rate of mortality (52%) was observed in the third week. With regard to the luck of the young parasites that remained without host it was observed that they swam for 48 hours, then fell in the bottom of aquarium and after 24 hours the first mortalities started. The adult parasites, that gave the young pulii II after 24 hours, were dead in the bottom of aquarium.

Assessing the quality of organic and conventionally-farmed European sea bass (Dicentrarchus labrax)

Successful cryopreservation in biodegradable containers of sperm from aquaculture Mediterranean fishes

9: Current Knowledge on the Development and Functionality of Immune Responses in the European Sea Bass (Dicentrarchus labrax)