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Developing tailor-made fortified farmed fish is a promising solution to overcome nutritional deficiencies and increase consumer confidence in these products. This study evaluated the supplementation of three fortified diets with I-rich seaweed and selenised-yeast on essential and toxic elements levels in gilthead seabream (Sparus aurata) and common carp (Cyprinus carpio). Fortified diets resulted in increased I, Se and Fe in fish muscle. Biofortified seabream and carp revealed lower Cu and Br. The reduction of fishmeal and fish oil in fortified diets resulted in lower Hg and Cd in seabream muscle. Contrarily, fortified diets increased As and Hg in carp fillets. The consumption of 150 g of fortified seabream enabled a significantly higher contribution to the daily recommended intake (DRI) of I (10%) and Se (76%) than non-fortified fish, whereas fortified carp fulfilled 23% of I DRI and 91% of Se DRI. Moreover, the exposure to Pb decreased with the consumption of biofortified seabream (23-82% BMDL 01 ) and carp (26-92% BMDL 01 ). These results support the strategy of developing eco-innovative biofortified farmed fish using sustainable, natural, safe and high-quality ingredients in feeds, to enable consumers to overcome nutritional deficiencies without significantly increased feed costs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The aim of this study was to evaluate the effects of short-chain fructooligosaccharides (scFOS), xylooligosaccharides (XOS) and galactooligosaccharides (GOS) on immune and hepatic oxidative status, and gut morphology of white sea bream juveniles. Four diets were formulated: a control diet with fish meal (FM) and plant feedstuffs (PF) (30FM:70PF) and three test diets similar to the control but supplemented with 1% of scFOS, XOS or GOS. Dietary prebiotic incorporation did not affect total blood cell counts, hematocrit, hemoglobin, red blood indices or differential white blood cell counts. Fish fed GOS had lower ACH50 and nitric oxide than fish fed control diet. XOS enhanced immune status through the increase in alternative complement pathway (ACH50), lysozyme and total immunoglobulin. The higher activity of glucose 6-phosphate dehydrogenase in fish fed FOS compared to the other dietary groups was the only related antioxidant enzyme affected by prebiotics in the liver. GOS ameliorated the precocious adverse effects of PF based diet on gut histomorphology, as denoted by the lower incidence of histological alterations in fish fed GOS for 15 days. In conclusion, XOS and GOS at 1% might have potential to be used as prebiotics in white sea bream juveniles., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Dietary amino acids imbalances have been described when fish larvae are fed rotifers, what may lead to a reduction in growth rate. The tube-feeding technique can be used to assess the effect of free amino acid short term supplementation. In this study supplementation of tryptophan, methionine and arginine were tested in Diplodus sargus. Single crystalline (14)C amino acids as well as a mix of (14)C amino acids were used as tracers to compare results of individual amino acids metabolism with the average of all amino acids. The results show low absorption efficiencies for tryptophan (70%) and arginine (80%) and similar absorption for methionine (90%) when compared with the average of all amino acids. Supplementation of these amino acids seems to be viable but it did not result in higher retention compared to the amino acid mix. This means that tryptophan, methionine and arginine are probably not the limiting amino acid when Diplodus sargus larvae are fed rotifers. However, supplementation in these IAA may be required for their roles as precursors of important molecules other than proteins, in order to improve larval quality and/or performance.

Control of the reproductive cycle is essential to achieve a successful aquaculture industry. Seahorse reared in captivity often shows eggs of poor quality and low offspring survival due to unsuitable rearing and nutritional protocols. This study aimed to evaluate the effect of dietary enrichment, added exclusively during the spawning season, on the egg quality of Hippocampus hippocampus. The effect of enriching mysis throughout the spawning season was analysed in terms of female fecundity, egg viability, egg size and fatty acid profile. The results showed that fecundity was not affected by the enrichment of the diet, but egg viability was increased when females were fed the enriched mysis (84.9 ± 4.1% compared to 62.2 ± 9.4%). Moreover, the content of several PUFA (20:4n-6, 18:2n-6, 22:5n-3, 22:5n-6, sum of n-6) decreased throughout the spawning season, especially in the last clutch, in eggs originated from females fed non-enriched mysis. Eggs from females fed the enriched diet maintained the fatty acid profile throughout the spawning season. In conclusion, enrichment of the diet of H. hippocampus improved egg viability and avoided a decrease in the quality of eggs by maintaining PUFA content in the last clutches of the spawning season. [ABSTRACT FROM AUTHOR]

A 14 weeks growth trial was performed to estimate the protein requirement for growth and maintenance of zebra sea bream ( Diplodus cervinus) juveniles. For that purpose, nine isolipidic diets were formulated to contain increasing protein levels (from 50 to 550 g kg−1) at the expense of carbohydrate. Each diet was assigned to duplicate groups of 20 fish, with an average body weight of 7.7 g. Feed efficiency improved with dietary protein up to 400 g kg−1, no further differences being noticed at higher protein levels. Fish fed the 50 g kg−1 protein diet lost weight during the trial. In the other groups, weight gain improved as dietary protein increased up to 350-400 g kg−1. Fish fed diets with 250 g kg−1 protein or lower had lower whole-body protein content than the other groups. A curvilinear-plateau model was used to adjust weight gain and protein gain (g kg ABW−1 day−1) to dietary protein levels. Based on that model, the optimum dietary protein requirement for maximum weight gain was estimated to be 437.6 g kg−1 and for maximum protein gain 461.9 g kg−1, corresponding to a protein intake of 7.63 g kg ABW−1 day−1. Protein requirement for maintenance was estimated to be 1.01 g kg ABW−1 day−1. [ABSTRACT FROM AUTHOR]

To assess the effect of feeding frequency on the utilization of dietary starch by white sea bream juveniles, triplicate groups of fish were fed an experimental diet (400 g kg−1 protein, 140 g kg−1 lipids and 350 g kg−1 pregelatinized maize starch) to apparent visual satiation 2, 3 or 4 times a day for 63 days. Growth performance, feed utilization efficiency, glycaemia, cholesterolaemia, plasma triacylglycerides, liver lipids and glycogen content were unaffected by feeding frequency. α-Amylase activity increased from the pyloric caeca to the posterior intestine and was higher in fish fed twice a day than in fish fed 3 or 4 times a day. Hepatic glucokinase ( GK) activity decreased with the increase in feeding frequencies, whereas fructose-1,6-bisphosphatase ( FBPase) activity increased. Hepatic glucose-6-phosphate dehydrogenase and glutamate dehydrogenase activities were unaffected by feeding frequency. Overall, feeding frequency did not improve white sea bream dietary starch utilization. α-Amylase, GK and FBPase activities responded to dietary starch consumed at each meal, denoting a good metabolic adaptation of the fish to the feeding conditions. [ABSTRACT FROM AUTHOR]

Abstract This study assessed the effect of supplementation of low-fishmeal (FM) diets with taurine in white seabream (Diplodus sargus) juveniles. Four isoproteic (36% CP) and isolipidic (18% CL) diets were formulated to include 15%FM or 5%FM, supplemented or not with 1% of Taurine (TAU). Twelve groups of 15 fish (IBW = 58 g) were fed each diet to near satiation for 10 weeks. Growth performance, feed intake, and feed efficiency were not affected by dietary FM level. Nevertheless, dietary TAU supplementation increased growth performance and feed efficiency. Nitrogen and energy retention were improved by both dietary FM level and TAU supplementation. Plasma cholesterol, lactate, and bilirubin did not differ among dietary treatments, but dietary TAU supplementation decreased plasma glucose and triglycerides levels. Decrease of FM level reduced total bile salts while TAU supplementation had the opposite effect. No differences were noticed in innate immune parameters assessed. Overall, results indicate that white seabream can be fed with diets almost devoid of FM, and that dietary TAU supplementation increases growth performance and feed efficiency. Moreover, results suggest that dietary TAU was limiting both in 15% and 5% FM diets. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effects of dietary methionine (Met) and taurine (Tau) supplementation on growth performance, feed utilization, and oxidative status of European sea bass juveniles. For that purpose, a 12-week growth trial was performed to test four isolipidic (18%) and isonitrogenous (6.7%) practical diets, containing 82% of the protein from plant origin and 18% from fish meal. Diets were formulated to have a Met level below (LMet) or above (HMet) requirements and were supplemented or not with 1% Tau (LMetTau and HMetTau). No dietary Met or Tau effects were observed on growth, feed utilization, and whole-body composition. Increasing dietary Met level led to increased catalase (CAT) and glutathione peroxidase (GPX) activities in the liver and total (tGSH) and reduced (GSH) glutathione in the intestine, while decreasing glutathione reductase (GR) and GPX activities in the intestine. Most of these effects were only observed in fish fed diets not supplemented with Tau. Dietary Tau supplementation decreased intestinal tGSH, GSH and oxidised (GSSH) glutathione content, the activity of GPX both in liver and intestine, and glucose-6-phosphate dehydrogenase (G6PDH) activity in the liver. Dietary Tau supplementation also affected hepatic CAT and intestinal GR activities, but effects were dependent of the dietary Met level. Overall, European sea bass seems to cope well with a plant-protein rich diet without Met or Tau supplementation. Both dietary Met and Tau were shown to modulate fish antioxidant response but without altering the oxidative damage level. [ABSTRACT FROM AUTHOR]

A study was undertaken to evaluate the effects of supplementation of high soybean meal (SBM)/low fish meal (FM) based diets for white seabream ( Diplodus sargus ) juveniles with Natugrain® TS, a nonstarch carbohydrases (NSPase) enzyme complex. Four isoproteic (36% CP) and isolipidic (18% CL) diets were formulated in a 2 × 2 factorial design with FM/SBM levels and NSPase supplementation as factors. Diets included 15%FM/32%SBM or 5%FM/42%SBM, supplemented or not with 0.04% of Natugrain® TS. Twelve groups of 15 fish (IBW = 58 g) were fed each diet to near satiation for 10 weeks. The apparent digestibility coefficients of the diets were evaluated in a different trial. Reduction of dietary FM from 15 to 5% did not affect voluntary feed intake, growth performance, feed efficiency, whole body composition, apparent digestibility coefficients, distal intestine and liver histomorphology, and digestive enzyme activities. However, dietary NSPase supplementation greatly increased overall feed, protein, and energy utilization, and this effect was higher in the low than in the high FM diet. Whole-body protein and lipid content also increased with dietary NSPase supplementation, and nitrogen and energy fecal losses were reduced. Moreover, in the low FM diet NSPase supplementation promoted an increase of amylase and lipase activities but not of protease activity. Overall, results indicate that white seabream perform well with diets almost devoid of FM. Also, NSPase supplementation to high plant feedstuff diets improves feed and nutrient utilization efficiency, and contribute to a reduction of fecal waste production. Statement of relevance Dietary supplementation with carbohydrase complexes is a possible strategy to overcome some of the drawbacks of plant based feedstuffs diets for aquaculture species, enhancing nutrient availability and alleviate digestive disorder. White seabream accepted, grew and utilized almost non-FM diets, if dully supplemented with carbohydrases. Dietary carbohydrase supplementation considerably increased feed utilization efficiency, reducing environmental waste. [ABSTRACT FROM AUTHOR]

A high frequency of cannibalism and high variability of growth rate within the same larval batch are the main bottlenecks for implementation of meagre culture. In this study the effect of two sodium alginate-encapsulated diets containing 55 (control) and 68% protein was tested in terms of larval composition, survival, growth and muscle cellularity. The results showed that the diet with higher protein content improved larval survival but no differences on larval growth were observed between treatments. Diets did not affect the amino acid and fatty acid profiles of meagre larvae. The differences between larval fatty acid profiles were mainly related to larval age rather than treatments. Meagre larvae fed the high protein diet showed a higher frequency of white muscle fibres with an area smaller than 150 μm 2 and a lower mean fibre area (214.9 ± 160.6 μm 2 and 187.88 ± 162.7 μm 2 , for 55 and 68% of protein, respectively). These results suggest that a higher dietary protein increases meagre larval survival and leads to a potential higher contribution of fibre hyperplasia. Statement of relevance The main aim of this work was to test two diets containing different protein levels (55 and 68%) and determine its effect on larval survival, growth, larval composition and muscle cellularity. This work was carried because meagre has been thought to have a higher protein requirement compared to seabream and seabass (Amoedo, 2011). Nevertheless, meagre is usually fed on diets formulated specifically for seabream suggesting that meagre protein requirements are not being satisfied and meagre growth might be constrained. Given that meagre is the species with highest potential to be intensively farmed in the Mediterranean region it is important to formulate specific diets for this species. The results obtained in this work showed that although growth was not affected by the diet, there seems to be a higher potential for growth in the long-term as fibre recruitment was higher when larvae were fed a high protein diet. [ABSTRACT FROM AUTHOR]