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Abstract: This study aimed at evaluating the effects of short‐chain fructooligosaccharides (scFOS), xylooligosaccharides (XOS) and galactooligosaccharides (GOS) on growth performance, hepatic metabolism, gut microbiota and digestive enzymes activities 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 control but supplemented with 10 g of scFOS, XOS or GOS per kilo diet, which were fed to fish during 12 weeks. Prebiotics had no effect on growth, feed efficiency or gut microbiota. Plasmatic triglycerides were lower in fish fed XOS than FOS and GOS diets. Malic enzyme activity was lower in fish fed XOS than FOS diet. Fish fed XOS diet had lower fatty acid synthetase (FAS), a key lipogenic enzyme and higher alanine aminotransferase activities. Fifteen days after the start of the trial, an enhancement of total alkaline protease, trypsin and lipase activities was observed in fish fed prebiotics, but such effect disappeared at 12 weeks. In conclusion, scFOS, XOS or GOS seem to have limited applicability in white sea bream feed. [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]

The aim of this study was to assess the role of soluble non-starch polysaccharide (guar gum) on white sea bream Diplodus sargus, glucose and lipid metabolism. A control diet was formulated to contain 40 % crude protein, 14 % crude lipids and 35 % pregelatinized maize starch, and three other diets were formulated similar to the control diet except for guar gum, which was included at 4 % (diet GG4), 8 % (diet GG8) or 12 % (diet GG12). Diets were fed to the fish for 9 weeks on a pair-feeding scheme. Guar gum had no effect on growth performance, feed efficiency, glycaemia, cholesterolaemia and plasma triacylglyceride levels. Hepatic glucokinase and pyruvate kinase activities, liver glycogen content and liver insulin-like growth factor-I gene expression were not affected by dietary guar gum, while fructose-1,6-bisphosphatase activity was lower in fish fed guar gum-supplemented diets. Hepatic glucose-6-phosphate dehydrogenase activity was higher in fish fed diets GG4 and GG8 than in the control group. Overall, data suggest that in contrast to mammals guar gum had no effect on white sea bream glucose utilization and in lowering plasma cholesterol and triacylglyceride levels. However, it seems to contribute to lower endogenous glucose production. [ABSTRACT FROM AUTHOR]

In order to investigate the effects of dietary protein hydrolysates (PH) on larval growth performance, skeleton quality and proteome expression, triplicate groups of white seabream ( Diplodus sargus) larvae were co-fed from first-feeding with live feed and three microencapsulated diets differing in the molecular weight of their PH fraction (Control - inclusion of CPSP-90; H - inclusion of a high amount in 0.5-30 kDa hydrolysates; L - inclusion of a high amount in <0.5 kDa hydrolysates). At 15 days after hatching (DAH), proteome expression changes were assessed in entire larvae by two-dimensional gel electrophoresis and the quality of larval skeleton was analysed at 28 DAH through double staining of cartilage and bone. Dietary PH fractions tested affected growth, the larvae fed diet L being significantly larger than those fed diet H, but it did not affect the incidence of deformed larvae, nor the number of deformities per fish. Two-dimensional analysis of larvae proteome allowed the detection and the comparative quantification of a total of 709 protein spots having a pI between 4 and 7, around half of which had an expression significantly affected by dietary treatment, the main difference being between proteome of Control larvae with those of both groups L and H. From these spots, 52 proteins involved in diverse processes such as cytoskeletal dynamics, energetic, lipoprotein, amino acid (AA), and nucleotide metabolisms, protein chaperoning and degradation, and signal transduction, were identified. This study revealed that the molecular weight of the dietary protein hydrolysate fraction had a minor impact on skeletal deformities in white seabream larvae, but affected growth performance and had a strong impact on larvae whole body proteome. [ABSTRACT FROM AUTHOR]

A trial was undertaken to estimate the protein requirement of white sea bream ( Diplodus sargus). Five fish meal-based diets were formulated to contain graded levels of protein (from 60 to 490 g kg−1). Each diet was assigned to triplicate groups of 25 fish with a mean individual body weight of 22 g. Fish fed the 60 g kg−1 protein diet lost weight during the trial, while growth improved in the other groups as dietary protein level increased up to 270–370 g kg−1. Feed efficiency improved as dietary protein level increased. Maximum protein efficiency ratio (PER) was observed with the 17% protein diet. N retention (NR) (% N intake) was not different among groups fed diets with 17% protein and above. Ammonia excretion (g kg−1ABW day−1) increased as dietary protein level increased, while no differences in urea excretion were noted. An exponential model was used to adjust specific growth rate and NR (g kg−1 day−1) to dietary protein level. Based on that model, dietary protein required for maximum retention was 330 g kg−1, while for maximum growth it was 270 g kg−1. On a wet weight basis, there were no differences in whole body composition of fish-fed diets with 170 g kg−1 protein and above, except for the protein content, which was lower in group fed the 170 g kg−1 protein diet than the 490 g kg−1 protein diet. Specific activities of hepatic amino acid catabolism enzymes (glutamate dehydrogenase, alanine aminotransferase and aspartate aminotransferase) increased as dietary protein levels increased. There were no differences among groups in fatty acid synthetase and malyc enzyme but 6-phosphate dehydrogenase (G6PDH) was significantly lower in fish fed the 60 g kg−1 protein diet than the 170 and 490 g kg−1 protein diets. [ABSTRACT FROM AUTHOR]

In this study, two growth trials were conducted to evaluate the effect of dietary protein and lipid levels on growth and feed utilization of white sea bream ( Diplodus sargus) juveniles. For the first trial, five diets were formulated to contain 120 g kg−1 lipid and increasing levels of protein, ranging from 400 to 600 g kg−1. Two additional diets were formulated with 400 and 600 g kg−1 protein and 180 g kg−1 lipids. The diets were fed to apparent visual satiety to duplicate groups of fish with a mean weight of 1.5 g for 10 weeks. For the second growth trial, four diets were formulated to contain 120 g kg−1 lipid and 380–520 g kg−1 protein. Two additional diets were formulated with 380 and 520 g kg−1 protein and 180 g kg−1 lipids. The diets were fed to apparent visual satiety to triplicate groups of fish with a mean weight of 41 g for 12 weeks. At the end of both trials, there were no growth differences among groups independent of the dietary protein content. In the first trial, growth was negatively correlated to dietary lipid levels. No significant differences of feed intake were detected among groups in both trials, but a direct correlation between feed efficiency and dietary protein level was observed. Protein efficiency ratio and nitrogen (N) retention (% N intake) significantly decreased with the increase of dietary protein levels. In both trials, energy retention (% energy intake) was highest in groups fed on diets with the highest protein-to-energy (P/E) ratio. At the end of both trials, no significant differences in whole-body composition were observed among groups. Specific activity of enzymes involved in amino acid catabolism [aspartate aminotransferase (AST), alanine aminotransferase (ALT) and glutamate dehydrogenase (GDH)] showed no significant differences with dietary protein level in both trials. Nevertheless, in the first trial, a significantly lower GDH activity was observed in fish fed with higher dietary lipid levels. No differences were found for specific activity of the lipogenic enzymes, fatty aid synthetase and glucose-6-phosphate dehydrogenase, in the second trial. Results of this study indicate that a diet with a protein level of 380–420 g kg−1 and a P/E ratio of 20 g protein MJ−1 satisfies the growth requirements of D. sargus juveniles. Also, within the range tested, no evidence of protein sparing by dietary lipids seems to occur. [ABSTRACT FROM AUTHOR]

Insect meals (IM) are being pointed out as a promising sustainable protein source. However, chitin in IM may negatively interfere with fish performance and nutrient availability. Given that carnivorous fish have a low or inexistent ability to digest chitin, novel strategies are needed to overcome chitin-imposed bottlenecks. Carbohydrolytic sporeforming probiotics offer a competitive industrial approach, being able to resist the harsh feed manufacturing process, transport, storage, and animal's gastrointestinal tract, while being able to increase the digestibility of otherwise indigestible components. Aiming to increase IM chitin digestibility, two chitinolytic sporeforming fish isolates (Fish isolates 645 (FI645) and 658 (FI658)), closely related to Bacillus licheniformis , were isolated from European sea bass (ESB) gastrointestinal tract, and incorporated (individually or as a mixture) in ESB diets with high defatted Hermetia illucens larvae meal (HM) levels (30% inclusion). FI were evaluated regarding their effects on ESB growth performance and digestibility. The spores were able to maintain their viability throughout the 180 days of diet storage at room temperature. Dietary inclusion of FI645 led to higher chitin digestibility. Concomitantly, the digestibility of dry matter, protein, and energy increased, overall leading to higher feed efficiency and protein efficiency ratio. Dietary inclusion of FI645 led to increased plasma N -acetylglucosamine (GlcNAc) levels. This is the first evidence for diet-mediated modulation of plasma GlcNAc concentrations. Dietary inclusion of FI645 also increased the expressions of the genes coding for N -acetylglucosamine kinase (nagk) and GlcNAc phosphomutase (pgm3) , key enzymes from the GlcNAc salvage pathway and the hexosamine biosynthetic pathway (HBP). On the other hand, no differences were found for the expression of N -acetyl-D-glucosamine-6-phosphate deacetylase (amdhd2) , a precursor enzyme for GlcNAc redirection to glycolysis. These results hint that free GlcNAc resulting from increased chitin digestibility might be preferentially redirected to protein O-GlcNAcylation processes through HBP in fish cells. Additionally, when challenged with Vibrio anguillarum , and after being feed for one month with the same diets, D645 also increased ESB survival from 52.5% to 77.5%, when compared to the control. Together, these results establish the potential of using FI645 as a probiotic for enhancing chitin digestion and acting as a prophylactic agent for ESB protection against V. anguillarum infection. This strategy opens novel possibilities for using commodities, including high chitin levels in aquafeeds, and reducing the use of antibiotics in aquaculture. • Fish isolate 645 increases chitin, protein, and energy digestibility and feed efficiency. • Increase in chitin digestibility increased N -acetylglucosamine in plasma. • The hexosamine biosynthetic pathway is potentially modulated by N -acetylglucosamine. • Fish isolate 645 increases European sea bass survivability to Vibrio anguillarum. [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]

Abstract: The present work aims to study the effect of a soluble non-starch polysaccharide (NSP), guar gum on white sea bream intestinal health through oxidative status and distal intestine morphology evaluation. A control diet was formulated to contain 40% crude protein, 14% crude lipids and 35% pregelatinized maize starch. Three other diets were formulated to include the same levels of all ingredients as control diet except for guar gum, which was included at 4% (diet GG4), 8% (diet GG8) or 12% (diet GG12). Compared to the control, lower catalase (CAT), superoxide dismutase (SOD) and glutathione reductase (GR) activities and higher SOD, glutathione peroxidase (GPX) and glucose-6-phosphate dehydrogenase (G6PD) activities were observed in the whole intestine of fish fed with diets GG4 and GG12, respectively. Thiobarbituric acid-reacting substances (TBARS) levels were unaffected by diet composition. No morphological alterations in the distal intestine were found among groups. Overall, data on key enzymes of the antioxidant enzymatic defense mechanism suggested that diet-induced reactive oxygen species (ROS) generation is dependent on guar gum inclusion levels and low dietary inclusion of soluble NSP (up to 4%) may have a gut oxidation stress prevention effect. [Copyright &y& Elsevier]

Abstract: A trial was undertaken to estimate the protein requirement of sharpsnout sea bream (Diplodus puntazzo) and the protein sparing of dietary lipids. Ten diets were formulated to contain 5 protein levels (ranging from 15 to 55%) and two lipid levels (12 and 18%). Each diet was assigned to duplicate groups of 15 fish with a mean individual body weight of 49.3g. A quadratic model was used to adjust weight gain and N retention (gkgABW−1 day−1) to dietary protein levels. Based on that model, optimum dietary protein requirement was estimated to be 42.9% for maximum weight gain and 43.8% for maximum N retention, corresponding to a protein intake of 7.68gkgABW−1 day−1. Protein requirement for maintenance was estimated to be 0.71gkgABW−1 day−1. Dietary lipid level improved protein utilization efficiency but did not affect protein requirement. Whole-body protein content increased with dietary lipids and protein content, but no other relevant differences in body composition were noticed. Hepatosomatic index increased with dietary starch and lipid levels and was directly correlated to liver glycogen content. Diet composition affected plasma glucose clearance and cholesterolaemia but not plasma protein and triglyceride levels. [Copyright &y& Elsevier]