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Aquaculture contributes to global food security but sustainable aquaculture development in terms of biodiversity impacts requires the establishment of viable solutions in replacement of the fisheries-based components in aquafeeds. In the current work, pit-tagged Atlantic salmon individuals were grown, from fresh water (18 g body weight) to salt water in tanks (up to 800 g body weight), on diets with low fish meal (FM) (10%) and 1–1.25% total n-3 LC-PUFA levels balanced across the experimental diets. Dietary n-3 LC-PUFAs were supplemented by (1) fish oil (FO), (2) Schizochytrium limacinum biomass (ScB), or (3) a mix of the two (FO/ScB). Further, the fish from all treatments were mixed and redistributed in sea cages reared to slaughter (ca. 3 kg body weight) on either FO or ScB. As FO was rich in both EPA and DHA and ScB was rich in DHA and nearly devoid of EPA, the experimental diets differed significantly in DHA/EPA ratio (0.8 vs. 10.5 in average for FO and ScB, respectively). ScB treatment fish grew to significantly higher body weight in the end of the experiment (2.8 kg vs. 3.3 kg, for FO and ScB, respectively) but similar FCR, survival rate, and biometric indexes compared to the FO groups. ScB fish contained higher levels of EPA + DHA in the filet but lower in the liver, and better filet pigmentation already from the tank phase of the experiment as determined chemically, by salmonfan and a trained sensory panel, and lower prevalence of melanin spots at slaughter. The trained sensory panel found no differences in flavor or odor in the filets from the different dietary groups; however, filets in the FO group were perceived as softer and juicier compared to ScB. The pre-diets up to 800 g body weight had minor effects on fish performance. Global transcriptomics in liver and intestinal tissues revealed significant dietary effects on the expression of immune modulating, as well as ion, lipid, protein, and xenobiotic metabolism genes.

The aquafeed ingredient inventory is ever changing, from marine to plant based, and recently evolving to incorporate increasing amounts of low trophic, side stream and circular economy based raw materials, each one contributing with variable amounts and qualities of macro- and micronutrients. Meeting the micronutrient requirement of farmed fish for healthy and efficient growth under normal and challenging conditions is of paramount importance. In this study we run a trial based on a 2 × 4 factorial design with three replications for each dietary treatment, where Atlantic salmon smolt were fed one of 8 experimental diets supplemented with either organic or inorganic mineral premixes (copper, iron, manganese, selenium, and zinc) at four dietary inclusion levels. We saw a trend for higher growth rate in the organic mineral groups irrespective of the dietary mineral levels. Mineral digestibility was negatively correlated with increasing mineral supplementation levels for all tested minerals but Se which increased with the increasing supplementation in the inorganic and up to the 2nd inclusion level in the organic mineral groups. Increasing mineral supplementation affected retention efficiency of Zn, Mn, Cu and Fe while mineral source affected only the retention of Se which was higher in the organic mineral groups. Moreover, fish obtained higher EPA and DHA in their body and increased slaughter yield in the organic as compared to the inorganic mineral groups and corroborated that trace mineral inclusion levels play a key role on salmon fillet's technical quality. More effects from different origin and dietary inclusion levels of trace minerals were seen on fillet yield, fillet technical and nutritional quality, bone strength, skin morphology, organ mineralization and midgut transcriptome. [ABSTRACT FROM AUTHOR]

The following research was conducted to elucidate the evolution and expression of salmonid selenoprotein P (SelP), a selenoprotein that is unique in having multiple selenocysteine (Sec) residues, following supranutritional selenium supplementation and infection in rainbow trout. We show that in salmonids SelP is present as four paralogues and that the diversification of SelP genes during vertebrate evolution relates to whole genome duplication events. With 17 and 16 selenocysteine residues for rainbow trout (Oncorhynchus mykiss)/Atlantic salmon (Salmo salar) SelPa1 and SelPa2 proteins respectively and 1 or 2 (trout or salmon) and 4 or 3 (trout or salmon) selenocysteine residues for salmonid SelPb1 and SelPb2 proteins respectively, this is the highest number of (predicted) multiple selenocysteine containing SelP proteins reported for any vertebrate species to date. To investigate the effects of selenium form on SelP expression we added different concentrations (1 nM– 10 μM) of organic or inorganic selenium to a trout cell line (RTG-2 cells) and analysed changes in mRNA abundance. We next studied the impact of supplementation on the potential modulation of these transcripts by PAMPs and proinflammatory cytokines in RTG-2 and RTS-11 cells. These experiments revealed that selenium type influenced the responses, and that SelP gene subfunctionalisation was apparent. To get an insight into the expression patterns in vivo we conducted a feeding trial with 2 diets differing in selenium content and 5 weeks later challenged the trout with a bacterial pathogen (Aeromonas salmonicida). Four tissues were analysed for SelP paralogue expression. The results show a significant induction of SelPa1 in gills and intestine following infection in selenium supplemented fish and for SelPa2 in gills. SelPb1 was significantly reduced in head kidney of both diet groups following infection, whilst SelPb2 was significantly upregulated in skin of both diet groups post infection. Overall these findings reveal differential expression profiles for the SelPa/SelPb paralogues in trout, influenced by selenium supply, cell type/tissue and stimulant. The increase of multiple Sec containing SelP proteins in salmonids could indicate an enhanced requirement for selenium in this lineage. [ABSTRACT FROM AUTHOR]

by Neil Cossons and Barrie Trinder, with a foreword by Eric DeLony (Chichester: Phillimore, 2002; pp. xiv + 154. 25 £). The Shropshire Iron Bridge is famous the world over. [...]

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. [ABSTRACT FROM AUTHOR]

During the last 400 years, armed clashes between the states of Europe have been instrumental in shaping the political structure of the Continent and, moreover, the course of international relations. [...]

Background: Selenium (Se) is an essential oligonutrient, as a component of several Se-containing proteins (selenoproteins), which exert important biological functions within an organism. In livestock, Se-enriched products have been proposed as dietary supplements to be included into functional feeds for animal preventive health care. To this end, it is important to understand the optimal range of concentrations for supplementation and how long it takes to be assimilated into the organism. Methods: In this study, rainbow trout (Oncorhynchus mykiss) were fed a control diet containing 0.9 g Kg-1 Se or the same diet supplemented with a Se-Yeast product (Sel-Plex) to achieve Se concentrations ranging from 1.5–8.9 g Kg-1 for a period of ten weeks. Fish were sampled every two weeks for analysis. The kinetics of Se bioaccumulation and the effects on fish selenoprotein expression was determined in different tissues combining chemical and bimolecular techniques. Results: The Sel-Plex enriched diets did not have any effect on survival and growth performance. The highest Se levels were found in liver and kidney followed by muscle and blood cells. Analysis of the Se concentration factor showed that liver is able to initially regulate the amount of Se accumulated. However, with higher dietary Se level (4.8 and 8.9 g Kg-1) and longer times of exposure (10 weeks), regulation is ineffective and the Se tissue concentration increases. The expression of the selected trout selenoprotein transcripts showed an inverse correlation with Sel-Plex augmentation in most cases. In liver, kidney and blood cells the highest up-regulation of the trout selenoprotein genes was seen mostly in the group fed the diet enriched with the lowest concentration of Sel-Plex (0.5 g Kg-1) for 10 weeks. Conclusion: Sel-Plex may represent an excellent Se supplement to deliver a high level of Se without provoking harm to the fish and to guarantee the maximal absorption of the element. According to our results, a dietary supplementation of Sel-Plex between 0.5 and 4 g Kg-1 may allow maximal benefits, whereas 8 g Kg-1 may be excessive for the purpose of supplementation. [ABSTRACT FROM AUTHOR]

Microalgae, as primary producers of EPA and DHA, are among the most prominent alternative sources to fish oil for n-3 long-chain PUFA in animal and human nutrition. The present study aimed to assess technical, nutritional and fish health aspects of producing n-3-rich Atlantic salmon (Salmo salar) fish fillets by dietary supplementation of increasing levels of a DHA-producing Schizochytrium sp. and reduced or without use of supplemental fish oil. Atlantic salmon smolt were fed diets with graded levels of microalgae for 12 weeks, during which all fish showed high feed intake rates with postprandial plasma leptin levels inversely correlating with final mean fish body weights. Fish performance was optimal in all experimental treatments (thermal growth coefficient about 4·0 and feed conversion ratio 0·8-0·9), protein digestibility was equal in all diets, whereas dietary lipid digestibility inversely correlated with the dietary levels of the SFA 16 : 0. Fillet quality was good and similar to the control in all treatments in terms of n-3 long-chain PUFA content, gaping, texture and liquid losses during thawing. Histological fluorescence staining and immunofluorescence analysis of salmon intestines (midgut: base of intestine and villi) revealed significant effects on slime, goblet cell production and inducible nitric oxide synthase (iNOS) activity with increasing levels of dietary Schizochytrium sp. supplementation. Microarray analysis did not reveal any signs of toxicity, stress, inflammation or any other negative effects from Schizochytrium sp. supplementation in diets for Atlantic salmon. [ABSTRACT FROM AUTHOR]

We examined the effects of the following seven experimental diets that varied in the concentration of inactivated cells ofEnterococcus faecalis(Ef) and mannan oligosaccharides (MOS), on Rainbow TroutOncorhynchus mykiss: control (C) diet (noEfand no MOS), diet E0.25% (2.5 g/kgEf), diet E0.5% (5 g/kgEf), diet M0.25% (2.5 g/kg MOS), diet M0.5% (5 g/kg MOS), diet EM0.25% (2.5 g/kgEf+ 2.5 g/kg MOS) and diet EM0.5% (5 g/kgEf+ 5 g/kg MOS). Rainbow Trout, initially weighing 36.27 ± 0.42 g (mean ± SD) were distributed into fourteen 60-L glass tanks at a stocking density of 35 fish per tank. Each diet was hand-fed to duplicate groups of fish twice daily for a 12-week period. After the feeding test, an intraperitoneal injection challenge test ofAeromonas salmonicidawas conducted over 14 d. Resulting data were submitted to a multivariate analysis of variance. Weight gain increased significantly (P< 0.05) in E0.25%, M0.25%, and EM0.5% experimental groups compared with the control. Specific growth rate was significantly higher (P< 0.05) in fish fed E0.25%, M0.25%, and EM0.5% diets compared with fish fed the C diet. Feed gain ratio and protein efficiency ratio were significantly improved (P< 0.05) in fish fed the EM0.5% diet compared with fish fed the C diet. Feed intake, protein efficiency ratio, protein retention, and the apparent digestibility coefficient recorded slight differences within experimental groups. Hematocrit value and phagocytic activity were significantly higher (P< 0.05) in fish fed E0.25%, E0.5%, M0.5%, EM0.25%, and EM0.5% diets compared with fish fed the C diet. Except for fish in the E0.25% group, fish in all other experimental groups showed a significantly higher (P< 0.05) mucus weight compared with those in the C group. After the challenge test, cumulative mortality and frequency ofA. salmonicidawere significantly decreased (P< 0.05) in all experimental groups compared with the C group. In conclusion, dosage and single or combined supplementation ofEfand MOS are factors that significantly affect fish performance. Received October 30, 2012; accepted April 13, 2013 [ABSTRACT FROM PUBLISHER]