growth performance and stress response of common sole subjected to varying stocking densities and rearing temperatures

AbstractEarlier short-term studies have shown productivity of intensively farmed common sole (S. solea) to be closely dependent on rearing density. Irrespective of fish size, elevating crowding conditions led to declining growth rates while the effect of density on mortality remains controversial. To what extent water temperature could affect productivity of growing sole subjected to varying crowding conditions, warrants investigation as very few studies have tried to quantify the effects of this fundamental rearing parameter on growth and survival in this fish species. This is particularly crucial for developing suitable farming protocols in Italy, where common sole may experience a broad range of water temperatures throughout the rearing cycle. The aim of this study was to evaluate productivity and blood cortisol level as a measure of stress response, in growing sole subjected to different stocking densities and temperature conditions. Six hundred juveniles (ind. weight 21.8±1.5g) were randomly allotted..

Intestinal morpho-physiology and innate immune status of European sea bass (Dicentrarchus labrax) in response to diets including a blend of two marine microalgae, Tisochrysis lutea and Tetraselmis suecica

The aim of this study was to investigate the effects of replacing graded levels of dietary fish meal by a blend of two marine microalgae Tisochrysis lutea and Tetraselmis suecica on intestinal morpho-physiology and innate immune response in European sea bass. Two complete diets were formulated to be iso-nitrogenous and isolipidic and prepared by including a blend of the two microalgae, to replace approximately 15 and 45% fish meal protein of the control diet. A fourth diet, where the microalgae mix was substituted by soybean meal, was also prepared. Each diet was offered until visual satiety over 105 days to triplicated groups of European sea bass (204 \ub1 12.7 g), kept in a recirculating marine water system. The humoral and cellular innate immune parameters of E. sea bass were affected by the dietary treatment. Fish fed the microalgae-containing or the soybean rich diets, showed a significantly greater villi height, while the thickness of intestinal epithelium was significantly reduced in fish fed the soybean meal-rich diet. The activity of the brush border membrane enzymes, maltase, sucrase-isomaltase, \u3b3-glutamil transferase and alkaline phosphatase was not affected by dietary treatment but changed in different intestinal tracts. The genes sucrase-isomaltase, peptide transporter 1, sodium/potassium-transporting ATPase and aminopeptidase N were overexpressed in the pyloric and proximal region of the intestine of fish fed the microalgae-including diets. In conclusion, a blend of dried marine microalgae Tisochrysis lutea and Tetraselmis suecica as alternative ingredients to dietary fish meal did not hamper gut digestive-absorptive functions of E. sea bass. Moreover, it resulted in enhanced non-specific immune response, suggesting an effective role as an immunostimulant ingredien

Effect of dietary chitin on growth performance, nutrient utilization, and metabolic response in rainbow trout (Oncorhynchus mykiss)

The dietary inclusion of ingredients containing chitin has been claimed to be beneficial to fish health. However, controversial results on growth performance and nutrient digestibility have been reported in literature. The present study aimed at assessing the response of rainbow trout (Oncorhynchus mykiss) fed with increasing levels of chitin (0, 1.5, 3.0, and 4.5 %) in a semi-purified basal diet. Protein and lipid digestibility was assessed and after 10 weeks of feeding, 6 h after the last meal, fish were euthanized for the evaluation of growth performance, blood biochemistry, brush border membrane and chitinolytic enzyme activity, gene expression of enzymes and nutrient transporters as well as the major pro-inflammatory intestinal cytokines, and mid intestine microbiota. Dietary chitin inclusion of up to 3 % did not hamper growth performances, nutrient apparent digestibility, and levels of most blood enzymes and metabolites. Diet including 4.5 % chitin negatively affected growth performances and nutrient digestibility. The application of a multidisciplinary approach highlighted that the biomarkers related to gut digestion functionality and inflammation response were altered also in fish fed the diets including 1.5 and 3 % of chitin, while gut microbiota did not differ between dietary treatments, even if some taxa suggested to be important in fish physiology were not recovered. Overall, the results demonstrate a good tolerance of rainbow trout to diets including chitin up to 3 %

Chitin and its effects when included in aquafeed

Chitin, the second most abundant polysaccharide in nature after cellulose, has been the sub- ject of increasing interest in recent years, particularly in the aquaculture sector. This review focuses on the effects of chitin in aquafeed on growth, nutrient utilization, gut microbiome modulation, and the immune system of aquatic organisms. Data from the literature showed significant variability in response to chitin by species, with some species benefiting from dietary chitin supplementation in terms of growth and immune health. However, excessive chitin inclusion led to negative effects on the protein and lipid digestibility. These results suggest that optimizing the amount of chitin-containing ingredients in aquafeed requires a deep understanding of each species’ nutritional needs and other studies needed for differ- ent aquaculture species. Furthermore, studies have highlighted the potential of chitin as an immunostimulant and promoter of gut health. In conclusion, chitin appears to be a promis- ing additive for sustainable aquaculture, but further research is needed to define best prac- tices for its use

Postprandial kinetics of digestive function in rainbow trout (Oncorhynchus mykiss ): genes expression, enzymatic activity and blood biochemistry as a practical tool for nutritional studies

Postprandial kinetics of genes expression of gastric (chitinase, pepsinogen) and intestinal (alkaline phosphatase, maltase) digestive enzymes and nutrient transporters (peptide transporter 1, sodium-glucose transporter 1), Brush Border Membrane (BBM) enzymes activity (alkaline phosphatase, leucine aminopeptidase, maltase, saccharase) and blood biochemistry (triglycerides, cholesterol, protein, albumin, glucose, amino acids) through NMR spectroscopy, were investigated in rainbow trout (Oncorhynchus mykiss) fed a commercial aquafeed. For this purpose, fish were starved 72 h and digestive tract and blood were sampled before the meal and at 1.5, 3, 6, 9, 12, and 24 h after feeding (T0, T1.5, T3, T6, T9, T12 and T24). The postprandial kinetic showed that the expression of the genes involved in digestion and nutrient transport, the activity of BBM enzymes, and the presence of metabolites in blood were stimulated in different ways by the presence of feed in the digestive tract. The expression of most genes peaked 3 h after meal except gastric pepsinogen and maltase in distal intestine that peaked at T9 and T12, respectively. The activity of BBM enzymes were stimulated differently based on the intestine tract. The plasma proteins level increased from T1.5 until T9, while the other blood parameters unvariated during the postprandial period. This study supplied useful information about the physiological effects a single meal as a potential tool for planning nutritional studies involving the digestive functions

Single-cell proteins polyhydroxyalkanoates-rich microbial biomass from municipal and winery waste as potential additive for aquafeeds

This study evaluated single-cell protein production from PHA-rich mixed microbial cultures obtained from fermentation and subsequent PHA storage, using urban (namely food waste and municipal sewage sludge; FW-MSS) and agricultural waste (namely wine lees; WL) streams as substrates. FW-MSS fermentation achieved stable short-chain fatty acid (SCFA) production and a high CODSCFA/CODSOL ratio of 0.77 ± 0.01, which allowed to select a mixed microbial culture (MMC) with intracellular PHA content of 15.1 wt%, which aligns with fish dietary standards and yielded a MMC biomass with a protein level of 55.1 wt% and a balanced essential amino acid (EAA) profile. In contrast, WL fermentation showed lower SCFA content and stability, yielding a MMC with 45.8 wt% of protein along with a high non-conformance rate (53.65 %), and 7.2 wt% PHA, making the resulting MMC more suited as a supplemental protein source. Distinct microbial communities developed in the two SBRs due to different feedstocks, influencing the abundance of PHA-storing bacteria, with no known fish pathogens detected in either sample. Statistical analysis confirmed FW-MSS's superior product consistency, supporting its potential as a good quality SCP for aquafeed, especially for rainbow trout, as confirmed by its high essential amino acid index (EAAI)

Natural-based solutions to mitigate dietary microplastics side effects in fish

Dietary microplastics (MPs) can be consumed by fish, crossing through the gastrointestinal tract. MPs smaller than 20 μm can easily translocate to other organs, such as liver, commonly triggering oxidative stress in fish. Given the current unlikelihood of their short-term elimination, strategies to mitigate MPs-related issues on fish are of considerable interest to the scientific community. In the present study, to reduce both the dietary MPs-induced oxidative stress and the accumulation of MPs, the effectiveness of microencapsulated astaxanthin (ASX) was evaluated in zebrafish (Danio rerio). Specifically, zebrafish were reared from larvae to adults (6 months) and fed diets containing MPs different in range-size (polymer A: 1-5 μm; polymer B: 40-47 μm) at different concentrations (50 or 500 mg/kg). After this period, fish from each experimental group were divided in two sub-groups that were fed, for an additional month, with the previous diets or with the same diets containing implemented with microencapsulated ASX (7 g/kg), respectively. Results showed that microencapsulated ASX was able to counteract the negative effects caused by MPs different in size. Particularly, in zebrafish fed diets containing polymer B microbeads, microencapsulated astaxanthin was able to restore the intestinal epithelium, affected by the abrasive role of MPs during gut transit. Differently, in zebrafish fed diets containing polymer A microbeads, absorbed at intestinal level and translocated mainly to the liver, the microencapsulated ASX decreased the oxidative stress response and reduced the MPs accumulation in target organs due to the antioxidant and the coagulant properties of the ASX and microcapsules wall, respectively. Taken together, the results highlighted that the aquafeeds' implementation with microencapsulated astaxanthin is a prospective tool to prevent MPs-related issues in fish

Lipid quality and oxidative response in gilthead seabream fillets fed an organic diet including crayfish meal as a source of natural astaxanthin

Organic certification for aquaculture fish prohibits the use of synthetic pigments in feed but allows natural alternatives. Meal derived from the alien red swamp crayfish (Procambarus clarkii) is rich in astaxanthin, a powerful natural antioxidant. This study aims to evaluate the effects of a 12 % dietary inclusion of crayfish meal on the shelf-life and nutritional quality of farmed gilthead seabream (Sparus aurata). Compared to the control diet, the experimental diet had no negative effects on fish growth. To assess shelf-life, fillets from fish fed the two diets were analyzed at different times: immediately after harvesting (0 days), after refrigeration (4 days), after freezing (30 days), and post-cooking. Fillets from the crayfish-fed group showed a higher proportion of omega-3 polyunsaturated fatty acids compared to the control (26.5 % vs. 23.5 % of total fatty acid methyl esters). Additionally, levels of conjugated dienes and trienes in fish muscle were significantly lower in the experimental group, likely due to the antioxidant properties of astaxanthin. The radical scavenging activity of both feeds and fillets was evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, while endogenous antioxidant activity was assessed by thiol group analysis. Both methods highlighted significantly improved antioxidant capacity in fillets from the experimental diet (e.g., 34.5 % vs. 1.1 % for DPPH). Malondialdehyde analysis of refrigerated, frozen, and cooked fillets further confirmed significantly lower lipid oxidation levels in the test group compared to the control. Overall, these findings suggest that crayfish meal can be considered a natural functional ingredient in seabream diets, as its inclusion enhances fillet stability against oxidation

Unagreement is an illusion

This is the author accepted manuscript. The final version is available from Springer via http://dx.doi.org/10.1007/s11049-015-9311-yThis paper proposes an analysis of unagreement, a phenomenon involving an apparent mismatch between a definite third person plural subject and first or second person plural subject agreement observed in various null subject languages (e.g. Spanish, Modern Greek and Bulgarian), but notoriously absent in others (e.g. Italian, European Portuguese). A cross-linguistic correlation between unagreement and the structure of adnominal pronoun constructions suggests that the availability of unagreement depends on whether person and definiteness are hosted by separate heads (in languages like Greek) or bundled on a single head (i.e. pronominal determiners in languages like Italian). Null spell-out of the head hosting person features high in the extended nominal projection of the subject leads to unagreement. The lack of unagreement in languages with pronominal determiners results from the interaction of their syntactic structure with the properties of the vocabulary items realising the head encoding both person and definiteness. The analysis provides a principled explanation for the cross-linguistic distribution of unagreement and suggests a unified framework for deriving unagreement, adnominal pronoun constructions, personal pronouns and pro