Immune stimulation and improved infection resistance in European sea bass (Dicentrarchus labrax) fed mannan oligosaccharides

Hematological changes in Florida pompano (Trachinotus carolinus) supplemented with β-glucan and Pediococcus acidilactici synbiotic

Florida pompano (Trachinotus carolinus) are a species of growing interest for commercial aquaculture. Effective health monitoring is crucial to the successful growout of the species, and prophylactic and therapeutic use of chemicals and antibiotics has been the traditional strategy for promoting stock health. However, concerns about antimicrobial resistance, chemical residues in seafood products and the environment, and resultant immunosuppression have prompted the industry to identify alternative management strategies, including supplementation with prebiotics, probiotics, and combinations of both (synbiotics). The objectives of this study are to determine and compare hematological, plasma biochemical, and plasma protein electrophoresis data of synbiotic-supplemented (β-glucan and Pediococcus acidilactici) and non-supplemented Florida pompano. Reference intervals for blood analytes are provided for both groups and for subgroups (females, males, large, and small fish) where statistically significant results exist. There are no differences between the hematological and plasma biochemistry analytes between the supplemented and control groups, except for blood urea nitrogen and carbon dioxide, indicating a possible effect of synbiotic supplementation on gill function and osmoregulation. Sex-related and size-related differences are observed within each of the control and supplemented groups; however, biometric measurements do not strongly correlate with blood analytes. These data represent baseline hematological and plasma biochemical data in the Florida pompano and indicate the safety of synbiotic supplementation in this commercially important species. This study serves to further the commercialization of Florida pompano by providing blood analyte reference intervals for health monitoring in the aquaculture setting.

Behavior, intestinal health, and growth of small sea cucumbers Apostichopus japonicus in different color morphs

Selecting high-quality seeds with long-term advantages in behavior, intestinal health, and growth are the key to improve production efficiency of sea cucumber aquaculture. It is proposed to distinguish the seed quality of sea cucumbers by color morphs. In the present study, we carried out a 6-week experiment to investigate behavior, intestinal health, and growth of small sea cucumbers Apostichopus japonicus in different color morphs. We found that dark-colored seeds of sea cucumber were significantly more adhesive than those with light-colored seeds. This indicates that the dark-colored seeds of A. japonicus are more adaptive in complex environments in stock enhancement. Food consumption and defecation outputs of dark-colored seeds were significantly higher than those of light-colored seeds. In addition, the feces of dark-colored seeds of sea cucumber had significantly lower crude protein content and better intestinal morphology, but there was no advantage in digestive enzyme activities. This suggests that there are potential digestive benefits in dark-colored seeds. Further, dark-colored seeds of A. japonicus showed significantly better intestinal microbiota composition and faster growth rate than that of light-colored seeds. In conclusion, the present results prove that dark-colored seeds of sea cucumber have long-term advantages in behavior, intestinal health and growth. Overall, this study provides important information for the early selection of seeds and the consequent production efficiency in sea cucumber aquaculture.

Emerging relevance of cell wall components from non-conventional yeasts as functional ingredients for the food and feed industry

Non-conventional yeast species, or non-Saccharomyces yeasts, are increasingly recognized for their involvement in fermented foods. Many of them exhibit probiotic characteristics that are mainly due to direct contacts with other cell types through various molecular components of their cell wall. The biochemical composition and/or the molecular structure of the cell wall components are currently considered the primary determinant of their probiotic properties. Here we first present the techniques that are used to extract and analyze the cell wall components of food industry-related non-Saccharomyces yeasts. We then review the current understanding of the cell wall composition and structure of each polysaccharide from these yeasts. Finally, the data exploring the potential beneficial role of their cell wall components, which could be a source of innovative functional ingredients, are discussed. Such research would allow the development of high value-added products and provide the food industry with novel inputs beyond the well-established S. cerevisiae.

Fructooligosaccharide and Bacillus subtilis synbiotic combination promoted disease resistance, but not growth performance, is additive in fish

Species diversification from major to minor carps for their sturdiness and initial higher growth, and also a quest for antibiotic-free aqua farming in the subcontinent, mandates search for and evaluation of alternatives. An experiment was performed to investigate the potential of fructooligosaccharide (FOS) and Bacillus subtilis (BS) (alone or as synbiotics) in promoting growth and immunity against infections in Labeo fimbriatus fingerlings. Six iso-nitrogenous and iso-lipidic diets containing combinations of two levels of FOS (0% and 0.5%) and three levels of BS (0, 104, 106 CFU/g feed) were fed to fish for 60 days. At the end of the feeding trial, twenty-four fish from each group were injected intra-peritoneally with pathogenic strain of Aeromonas hydrophila O:18 to test the immunoprotective efficacy of the supplements against bacterial infection. BS, but not FOS, significantly improved (P < 0.05) growth and feed utilisation attributes like percentage weight gain (PWG), specific growth rate (SGR) and feed conversion ratio (FCR). There were interactive effects of FOS and BS on PWG, SGR and FCR; however, the effects were not additive in nature. These beneficial effects of BS, alone or in combination with FOS, were corroborated by increased protease activity, microvilli density and diameter and number of goblet cells. Overall beneficial effects of FOS and BS included improved erythrocyte (RBC), hemoglobin (Hb), total protein and globulin levels. Total leucocyte (WBC) count and immunological parameters like respiratory burst activity of leucocytes (NBT reduction), lysozyme activity, albumin: globulin ratio and post-challenge survival were significantly improved by both FOS and BS, and their dietary combination yielded the highest improvement in these parameters. Synergistic effects of FOS and BS as dietary supplements indicate that a combination of 106 CFU/g BS and 0.5% FOS is optimal to improve growth, feed utilisation, immune functions, and disease resistance in L. fimbriatus fingerlings.

Effects of Aspergillus-meal prebiotic diet on the growth performance, health status and gut microbiota of Asian seabass, Lates calcarifer

In this study, the growth performance, health status and intestinal microbiota of juvenile Asian seabass, Lates calcarifer, were assessed after dietary administration of a prebiotic product obtained from fermented Aspergillus orizae, Fermacto®. Asian seabass were fed three diets; control (without Aspergillus-meal prebiotic), 0.2% and 0.3% Aspergillus-meal prebiotic for 56 days. Fish were raised in freshwater with acceptable water quality. No significant differences were found in the growth performance and composition of dorsal fish muscle among all groups. Fish fed diets supplemented with 0.3% of Aspergillus-meal prebiotic had a significantly higher survival rate after being challenged with V. alginolyticus than fish fed with the control diet. Supplementation of the Aspergillus-meal prebiotic significantly improved immune responses by inducing higher respiratory burst, superoxide dismutase, phagocytic and lysozyme activity compared to the control group. In addition, prebiotic doses significantly induced an up-regulation of heat shock cognate 70 kDa protein (hsp70) in the liver compared to the control group. Signaling pathways were also affected with significantly higher gene expression of complement c-3 (c3), mechanistic target of rapamycin (mtor), and mammalian lethal with SEC13 protein 8 (mlst-8) in the liver of fish fed 0.3% Aspergillus prebiotic. The pro-inflammatory gene, tumor necrosis factor (tnf) and anti-inflammatory gene, transforming growth factor beta-1 (tfg-β1) were significantly higher in the head kidney of fish offered prebiotic diets. Fish receiving Aspergillus-meal prebiotic revealed significantly higher expression of Mx gene 24 h post nervous necrosis virus injection compared to the control. Additionally, the α-diversity of gut microbiota, including genus, Pielou's evenness, Shannon diversity index, and Margalef's species richness were significantly higher in fish fed 0.3% Aspergillus-meal prebiotic than the control group. The principal component analysis eigenvector plots showed that a high abundance of beneficial bacteria, such as Entercoccus faecium, Lactococcus lactis, Macrococcus caseolyticus and Vagococcus fluvialis, along with potentially pathogenic bacteria, such as Staphylococcus sciuri and L. garvieae subsp. garvieae were present in fish treated with Aspergillus-meal prebiotic. Although dietary Aspergillus-meal prebiotic did not improve the growth performance of Asian seabass, 0.3% of Aspergillus-meal prebiotic is recommended to elevate the immunological status of fish.

Mannan oligosaccharides alleviate oxidative injury in the head kidney and spleen in grass carp (Ctenopharyngodon idella) via the Nrf2 signaling pathway after Aeromonas hydrophila infection

BACKGROUND

Mannan oligosaccharides (MOS) are recommended as aquaculture additives owing to their excellent antioxidant properties. In the present study, we examined the effects of dietary MOS on the head kidney and spleen of grass carp (Ctenopharyngodon idella) with Aeromonas hydrophila infection.

METHODS

A total of 540 grass carp were used for the study. They were administered six gradient dosages of the MOS diet (0, 200, 400, 600, 800, and 1,000 mg/kg) for 60 d. Subsequently, we performed a 14-day Aeromonas hydrophila challenge experiment. The antioxidant capacity of the head kidney and spleen were examined using spectrophotometry, DNA fragmentation, qRT-PCR, and Western blotting.

RESULTS

After infection with Aeromonas hydrophila, 400-600 mg/kg MOS supplementation decreased the levels of reactive oxygen species, protein carbonyl, and malonaldehyde and increased the levels of anti-superoxide anion, anti-hydroxyl radical, and glutathione in the head kidney and spleen of grass carp. The activities of copper-zinc superoxide dismutase, manganese superoxide dismutase, catalase, glutathione S-transferase, glutathione reductase, and glutathione peroxidase were also enhanced by supplementation with 400-600 mg/kg MOS. Furthermore, the expression of most antioxidant enzymes and their corresponding genes increased significantly with supplementation of 200-800 mg/kg MOS. mRNA and protein levels of nuclear factor erythroid 2-related factor 2 also increased following supplementation with 400-600 mg/kg MOS. In addition, supplementation with 400-600 mg/kg MOS reduced excessive apoptosis by inhibiting the death receptor pathway and mitochondrial pathway processes.

CONCLUSIONS

Based on the quadratic regression analysis of the above biomarkers (reactive oxygen species, malondialdehyde, and protein carbonyl) of oxidative damage in the head kidney and spleen of on-growing grass carp, the recommended MOS supplementation is 575.21, 557.58, 531.86, 597.35, 570.16, and 553.80 mg/kg, respectively. Collectively, MOS supplementation could alleviate oxidative injury in the head kidney and spleen of grass carp infected with Aeromonas hydrophila.

Effects of Five Prebiotics on Growth, Antioxidant Capacity, Non-Specific Immunity, Stress Resistance, and Disease Resistance of Juvenile Hybrid Grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂)

To explore the short-term health benefits of five prebiotics on hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂), six experimental groups fed with different diets (basal diet, diet control (CON); basal diet + 0.2% fructooligosaccharide (FOS), diet FOS; basal diet + 0.5% chitosan, diet chitosan (CTS); basal diet + 0.2% mannan-oligosaccharide (MOS), diet MOS; basal diet + 0.1% β-glucan (GLU), Diet GLU; basal diet + 0.05% xylooligosaccharide (XOS), diet XOS) were set up, and a 4-week feeding trial was conducted. MOS and XOS significantly improved the growth of hybrid grouper compared to the CON group (p < 0.05). Antioxidant enzyme assay showed that the activity of glutathione peroxidase (GPx) was significantly enhanced in the MOS group, and the content of malondialdehyde (MDA) in the XOS group was significantly lower than in the CON group (p < 0.05). The catalase (CAT) activities were significantly enhanced in all prebiotic-supplemented groups compared with the CON group (p < 0.05). Non-specific immunity assay showed that the activities of alkaline phosphatase (AKP) and lysozyme (LZM) were significantly increased in all prebiotic-supplemented groups compared with the CON group (p < 0.05). The total protein content in the XOS group was significantly increased (p < 0.05), and the albumin (ALB) activity in the MOS group was more significantly increased than that in the CON group. Histological examination of the intestine revealed that muscle thickness was significantly increased in all prebiotic-supplemented groups compared to the CON group (p < 0.05). Villi length, villi width, muscle thickness all increased significantly in the MOS group (p < 0.05). In addition, the crowding stress and ammonia nitrogen stress experiments revealed that the survival rates of the MOS and XOS groups after stresses were significantly higher than those of the CON group (p < 0.05). Though MOS and XOS exhibited similar anti-stress effects, the antioxidant and non-specific immunity parameters they regulated were not the same, indicating that the specific mechanisms of MOS and XOS's anti-stress effects were probably different. After being challenged with Vibrio harvey, MOS and GLU groups showed significantly higher post-challenge survival rates than the CON group (p < 0.05). These findings indicated that among the five prebiotics, MOS and XOS showed the best overall short-term beneficial effects and could be considered promising short-term feed additives to improve the stress resistance of juvenile hybrid grouper.

Immunostimulatory effect of mannan-oligosaccharides supplementation diet in milkfish (Chanos chanos)

The current study was designed to examine the impacts of dietary mannan-oligosaccharides (MOS) on growth, hemato-biochemical changes, digestive-antioxidant enzyme activity, immune response, and disease resistance of milkfish (Chanos chanos) fed diets contained MOS i.e. 1g, 2g, and 3g MOS. The growth parameters were significantly influence in milkfish fed all MOS diets, whereas the feed conversion ratio (FCR) and protein efficiency ratio (PER) were significantly influence with 2g or 3g MOS diets. The total protein (TP), globulin (GB), and glucose (GLU) levels, amylase, protease, liver enzymes were found significantly high in fish fed 2g or 3g MOS diets; but, lipase, trypsin, and alkaline phosphatase (ALP) enzymes were increased significantly at 3g MOS diet. All MOS inclusion levels were significantly increased total and Lactobacillus intestinal microflora population. The oxidative enzymes activity as superoxide desmutase (SOD) and catalyze (CAT) were progressively increased with all MOS supplementation diet, but the glutathione peroxidase (GPx) and lactate dehydrogenase (LDH) content were found significantly high in fish fed 2g or 3g MOS diets. Similarly, the reduced glutathione (GSH) and glutathione reductase (GR) contents were observed significantly high level in fish fed 3g MOS diet. The phagocytic (PC) and lysozyme (LYZ) activities were found gradually increase in fish fed increasing level of MOS diets, while the respiratory burst (RB) and malondialdehyde (MDA) activities were seen significant in fish fed 2g and 3g MOS diets. The current research work confirmed that C. chanos fed diets contained 3g kg^-1 MOS recorded better growth performance, digestive-antioxidant, immune response, and disease resistance.

Effect of Additives Inclusion in Gilthead Seabream (Sparus aurata L.) Diets on Growth, Enzyme Activity, Digestibility and Gut Histology Fed with Vegetable Meals

The fishmeal replacement by vegetable meals or other alternative sources, without affecting fish performance and productivity, is one of the principal challenges in aquaculture. The use of hydrolyzed porcine mucosa (HPM) and nucleotide (NT) concentrates, as feed additives in gilthead seabream (Sparus aurata L.) non-fishmeal diets was assessed in order to determine the possible effects on growth, feed efficiency, protein digestion, and gut histology when these were included in a plant-based diet (HPM 1% and 2%, P1 and P2; NT 250 and 500 ppm, N250 and N500), in comparison with two control diets, AA0 (100% plant-protein-based diet) and FM100 (100% fishmeal-protein-based diet). Diets were assayed in triplicate and the growth assay lasted 134 days. Results showed a significant improvement in all groups in terms of final weight and specific growth rate in comparison with the AA0 group. An improvement in the feed conversion ratio and the protein efficiency ratio was also observed when the additives were included in lower percentages (P1 and N250) compared to the FM100 group. Significant differences were found in hepatosomatic index, villi thickness, and goblet cells. Thus, the inclusion of NT and HPM was tested as beneficial for the improvement of efficiency of plant feed in seabream.

Dietary Supplementation with a Blend of Hydrolyzable and Condensed Tannins Ameliorates Diet-Induced Intestinal Inflammation in Zebrafish (Danio rerio)

The current study evaluated the effects of hydrolyzable and condensed tannins from chestnut and quebracho wood, respectively (TSP, Silvafeed^®), on zebrafish with intestinal inflammation induced by a plant-based diet (basal diet). Four experimental diets were prepared as follows: the basal diet + 0 TSP, the basal diet + TSP at 0.9 g/kg of feed, the basal diet + TSP at 1.7 g/kg of feed, and the basal diet + TSP at 3.4 g/kg of feed. Eighty-four zebrafish (Danio rerio) were fed for 12 days with the experimental diets. In zebrafish fed the basal diet, intestine integrity appeared to be altered, with damaged intestinal villi, high immunoexpression of tumor necrosis factor-α (TNFα) and cyclooxygenase 2 (COX2), and high expression of the cox2, interleukin 1 (il-1b), interleukin 8 (cxcl8-l1), and tnfα genes. The tannin treatment partially restored intestinal morphology and downregulated the expression of cytokines. The best activity was detected with 1.7 and 3.4 g/kg of feed. In the guts of all groups, Proteobacteria, Fusobacteria, Firmicutes, and Bacteroidetes were the most represented phyla. The most represented genera were Plesiomonas and Sphingomonas, belonging to the Proteobacteria phylum; Cetobacterium, belonging to the Fusobacteria phylum; and Lactobacillus, belonging to the Firmicutes phylum. No significant differences were detected among groups, except for a slight decrease in the Fusobacteria phylum and slight increases in the Shewanella and Bacteroides genera with TSP. In conclusion, these results suggest that tannins can improve the zebrafish intestinal inflammation caused by a terrestrial-plant-based diet in a dose-dependent manner.

Gill Oxidative Stress Protection through the Use of Phytogenics and Galactomannan Oligosaccharides as Functional Additives in Practical Diets for European Sea Bass (Dicentrarchus labrax) Juveniles

The aim of the present study is to evaluate the potential of two functional additives as gill endogenous antioxidant capacity boosters in European sea-bass juveniles fed low-FM/FO diets when challenged against physical and biological stressors. For that purpose, two isoenergetic and isonitrogenous diets with low FM (10%) and FO (6%) contents were supplemented with 5000 ppm plant-derived galactomannan-oligosaccharides (GMOS) or 200 ppm of a mixture of garlic and labiate plant essential oils (PHYTO). A control diet was void from supplementation. Fish were fed the experimental diet for nine weeks and subjected to a confinement stress challenge (C challenge) or a confinement stress challenge combined with an exposure to the pathogen Vibrio anguillarum (CI challenge). Both GMOS and PHYTO diets attenuated fish stress response, inducing lower circulating plasma cortisol and down-regulating nfκβ2 and gr relative gene-expression levels in the gill. This attenuated stress response was associated with a minor energetic metabolism response in relation to the down-regulation of nd5 and coxi gene expression.

An accidental discovery of mannan-oligosaccharide's protection effect against air exposure and its potential mechanism in hybrid grouper (Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀)

The original objective was to explore the potential benefiting effects of three prebiotics in hybrid grouper (Epinephelus lanceolatus♂ × Epinephelus fuscoguttatus♀). Therefore, three experimental diets (basal diet + 1% fructooligosaccharide, Diet F; basal diet + 1% inulin, Diet I; basal diet + 0.3% mannan-oligosaccharide, Diet M) and one basal diet (Diet C) were prepared and a feeding trial was conducted. However, at the end of the fourth week into the feeding experiment, a water-leaking accident occurred and fishes of all groups went through an unexpected air exposure event. Surprisingly, different prebiotic-supplemented groups showed significantly different air exposure tolerance: the mortality of M group was significantly lower (P ≤ 0.05) than all the other groups. Examination of antioxidant, non-specific immunity, and stress parameters revealed that comparing to control group, M group showed significantly increased catalase (CAT), acid phosphatase (ACP), and alkaline phosphatase (AKP) activities, decreased superoxide dismutase (SOD) activity, and similar cortisol level (P ≤ 0.05). Real-time PCR experiment revealed that M group significantly increased the expression of CAT, glutathione peroxidase (GPx), and manganese superoxide dismutase (MnSOD) genes in head kidney (P ≤ 0.05). Overall, M exhibited the best anti-air exposure/antioxidative stress effects among the three prebiotics and could be considered a promising feed additive to relieve air exposure/oxidative stress in hybrid grouper culture.

cMOS enhanced the mucosal immune function of skin and gill of goldfish (Carassius auratus Linnaeus) to improve the resistance to Ichthyophthirius multifiliis infection

of supporting mucosal immune barrier integrity and prevention of some pathogenic infections in aquatic species, are key areas of active study, often focusing on feed additives. The objectives of this study were to explore the effects of feeding cMOS (concentrated mannan oligosaccharide) on the gill and skin mucosal barriers of goldfish (Carassius auratus Linnaeus) and evaluate health status during Ichthyophthirius multifiliis infection. After feeding the cMOS-containing diet for 60 days, Hematoxylin and eosin (H&E) staining showed greater length of gill lamella and thicker dermal dense layer, while Alcian Blue and Periodic acid-Schiff (AB-PAS) staining showed higher numbers of mucin cells in cMOS fed fish. Chemical analysis showed that fish fed cMOS had greater enzyme activity of lysozyme (LZM) and alkaline phosphatase (AKP) in gill and skin tissues, while qRT-PCR revealed higher expression of Muc-2 and IL-1β, as well as lower expression of IL-10. After Ichthyophthirius multifiliis challenge, goldfish fed the cMOS diet had lower mortality and infection rates, as well as fewer visible white spots on the body surfaces. Histologically, the gill and skin of these fish presented less tissue damage and fewer parasites, and had a greater number of mucus cells. In addition, the expression of Muc-2 and IL-10 were notably higher while the expression of IL-1β was significantly lower in cMOS fed goldfish than control fed fish. In this study, cMOS fed goldfish had stronger immune barrier function of skin and gill mucous, and better survival following Ichthyophthirius multifiliis infection.

Dietary Mannan Oligosaccharides Enhance the Non-Specific Immunity, Intestinal Health, and Resistance Capacity of Juvenile Blunt Snout Bream (Megalobrama amblycephala) Against Aeromonas hydrophila

Mannan oligosaccharides (MOS) have been studied and applied as a feed additive, whereas their regulation on the growth performance and immunity of aquatic animals lacks consensus. Furthermore, their immunoprotective effects on the freshwater fish Megalobrama amblycephala have not been sufficiently studied. Thus, we investigated the effects of dietary MOS of 0, 200, and 400 mg/kg on the growth performance, non-specific immunity, intestinal health, and resistance to Aeromonas hydrophila infection in juvenile M. amblycephala. The results showed that the weight gain rate of juvenile M. amblycephala was not significantly different after 8 weeks of feeding, whereas the feed conversion ratio decreased in the MOS group of 400 mg/kg. Moreover, dietary MOS increased the survival rate of juvenile M. amblycephala upon infection, which may be attributed to enhanced host immunity. For instance, dietary MOS increase host bactericidal and antioxidative abilities by regulating the activities of hepatic antimicrobial and antioxidant enzymes. In addition, MOS supplementation increased the number of intestinal goblet cells, and the intestine was protected from necrosis of the intestinal folds and disruption of the microvilli and junctional complexes, thus maintaining the stability of the intestinal epithelial barrier. The expression levels of M. amblycephala immune and tight junction-related genes increased after feeding dietary MOS for 8 weeks. However, the upregulated expression of immune and tight junction-related genes in the MOS supplemental groups was not as notable as that in the control group postinfection. Therefore, MOS supplementation might suppress the damage caused by excessive intestinal inflammation. Furthermore, dietary MOS affected the richness and composition of the gut microbiota, which improved the gut health of juvenile M. amblycephala by increasing the relative abundance of beneficial gut microbiota. Briefly, dietary MOS exhibited significant immune protective effects to juvenile M. amblycephala, which is a functional feed additive and immunostimulant.

Effects of Dietary Mannan Oligosaccharides on Non-Specific Immunity, Intestinal Health, and Antibiotic Resistance Genes in Pacific White Shrimp Litopenaeus vannamei

This study was conducted to comprehensively investigate the beneficial effects of a mannan oligosaccharide product (hereinafter called MOS) on Litopenaeus vannamei and optimum level of MOS. Five isonitrogenous and isolipid diets were formulated by adding 0%, 0.02%, 0.04%, 0.08%, and 0.16% MOS in the basal diet. Each diet was randomly fed to one group with four replicates of shrimp in an 8-week feeding trial. The results showed that dietary MOS improved the growth performance and the ability of digestion of shrimp. Dietary MOS significantly increased the activity of total superoxide dismutase, catalase, and glutathione peroxidase and decreased the content of malondialdehyde in plasma of shrimp. Dietary MOS significantly increased the activity of alkaline phosphatase and lysozyme in plasma and the hemocyte counts. Dietary MOS significantly upregulated the expression of Toll, lysozyme, anti-lipopolysaccharide factor, Crustin, and heat shock protein 70 in the hepatopancreas. And dietary MOS significantly upregulated the expression of intestinal mucin-2, mucin-5B, and mucin-19, while it decreased the expression of intestinal mucin-1 and macrophage migration inhibitory factor. Dietary MOS improved the bacterial diversity; increased the abundance of Lactobacillus, Bifidobacterium, Blautia, and Pseudoalteromonas; and decreased the abundance of Vibrio in the intestine. Shrimp fed MOS diets showed lower mortality after being challenged by Vibrio parahaemolyticus. Notably, this study found a decrease in antibiotic resistance genes and mobile genetic elements after MOS supplementation for the first time. The present results showed that diet with MOS supplementation enhanced the organismal antioxidant capacity and immunity, improved intestinal immunity, optimized intestinal microecology, mitigated the degree of antibiotic resistance, and increased the resistance to V. parahaemolyticus in L. vannamei, especially when supplemented at 0.08% and 0.16%.

Mannan Oligosaccharide Enhanced the Growth Rate, Digestive Enzyme Activity, Carcass Composition, and Blood Chemistry of Thinlip Grey Mullet (Liza ramada)

Simple Summary

Sustainable aquaculture requires natural alternative substances with high potential in enhancing the performance and wellbeing of aquatic animals. In this regard, the present study tested the possibility of using mannan oligosaccharides (MOS) in the diets of grey mullet as functional additives. For 8 weeks, fish were fed with enriched diets containing 0, 0.5, 1, and 2% MOS. The results showed marked improvements in the growth performance, digestive enzyme activity, blood chemistry, and antioxidative capacity. In conclusion, dietary MOS at 0.5–1% is required to enhance the productivity of grey mullet.

Abstract

Mannan oligosaccharide (MOS) is prebiotic with high functionality in aquaculture. The current study investigated the potential roles of MOS on the growth performance, digestive enzyme activity, carcass composition, and blood chemistry of Thinlip grey mullet (Liza ramada). Four tested diets with 34.49% crude protein and 6.29% of total lipids were prepared and fortified with 0, 0.5, 1, and 2% MOS. Fish of initial weight = 5.14 ± 0.11 g/fish were distributed in 12 hapas (0.5 × 0.5 × 1 m) at 15 fish per hapa (triplicates) and fed the test diets to the satiation level two times a day (08:00 and 15:00) for eight weeks. At the end of the trial, all fish were weighed individually for growth performance calculation. Blood was collected to check blood chemistry traits, and intestines were dissected for digestive enzyme analysis. Fish treated with MOS had marked enhancement in the final body weight, feed conversion ratio, protein gain, and protein retention regardless of inclusion dose (p < 0.05). The weight gain, specific growth rate, and protein efficiency ratio were meaningfully enhanced by including MOS at 0.5 and 1%, followed by fish fed with 2% MOS, while the lowest values were in the control group (p < 0.05). Insignificant influences of MOS were seen on the chemical composition of carcass components (moisture, crude protein, total lipids, and ash) (p > 0.05). Fish treated with MOS at 0.5 and 1% had marked enhancement in the amylase, lipase, and protease activities regardless of inclusion dose (p < 0.05). The blood total protein and albumin levels were meaningfully enhanced by including MOS at 0.5 and 1%, followed by fish fed with 2% MOS, while the lowest values were in the control group (p < 0.05). The blood globulin was significantly enhanced in fish fed 1% MOS than fish treated with 0, 0.5, and 2% of MOS (p < 0.05). The blood lysozyme activity was meaningfully enhanced by including MOS at 1%, followed by fish treated with 0.5 and 2%, while the lowest values were in the control group (p < 0.05). Phagocytic activity and phagocytic index were markedly improved in fish treated with 1 and 2% MOS, followed by those fed 0.5% compared with fish fed MOS-free diet (p < 0.05). Superoxide dismutase and glutathione peroxidase were markedly improved in fish treated with 1, and 2% MOS, followed by those fed 0.5% compared with fish fed MOS-free diet (p < 0.05). Dietary MOS (0.5, 1, and 2%) meaningfully enhanced catalase activity while decreased the malondialdehyde concentration (p < 0.05). In summary, dietary MOS is required at 0.5–1% for enhancing the growth rate, feed efficiency, digestive enzyme activity, blood chemistry, and antioxidative capacity of grey mullet.

Mannans and mannan oligosaccharides (MOS) from Saccharomyces cerevisiae - A sustainable source of functional ingredients

Sustainable industry practices and circular economy concepts encourage the transformation of production waste into by-products. Saccharomyces cerevisiae is widely used in fermentation industry worldwide, generating large amounts of spent yeast which is mainly directed to animal feed or discarded as waste. Instead of becoming and environmental problem, spent yeast can be directed to the extraction of valuable compounds such as mannans and mannan oligosaccharides (MOS). This review presents a compilation of the studies up to date regarding the different chemical, enzymatic, mechanical or physical processes addressed for mannans extraction and MOS production. Additionally, the existing studies on the chemical modification of mannans aimed to improve specific characteristics are also discussed. Finally, the more relevant bioactivities and potential applications of mannans, MOS and mannose are presented, together with products on the market containing these compounds.

Transcriptome Analysis Provides Insights into Hepatic Responses to Trichloroisocyanuric Acid Exposure in Goldfish (Carassius auratus)

Simple Summary

Trichloroisocyanuric acid (TCCA) has been widely used in public health and aquaculture for the prevention and treatment of diseases. As a strong oxidative disinfectant, TCCA may cause adverse influences on aquatic organisms and further poses a threat to the aquatic ecosystems. Nonetheless, the toxicological influences of TCCA on aquatic animals are still scarce and the mechanisms of the toxicity at the molecular levels in goldfish (Carassius auratus) have not been illustrated. The current study investigated the influences of sublethal concentration of TCCA on transcriptomic responses, the molecular indices of oxidative stress, and histopathological alterations in the hepatic and gill tissues of goldfish. The results indicated that TCCA exposure induced the disturbance of energy metabolism and the detoxification process. Furthermore, TCCA exposure also induced oxidative stress in the liver and caused pathological damage in gills. These findings could be useful to help understand the toxicological influences of TCCA on goldfish.

Abstract

In this study, goldfish (Carassius auratus) were exposed to 0 (control group) and 0.81 mg/L TCCA for four consecutive days. The liver transcriptome, the molecular indices of oxidative stress, and gills histopathology were investigated. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that energy metabolism-related pathways such as glycolysis/gluconeogenesis were significantly enriched, suggesting their perturbation in the liver of goldfish. Additionally, TCCA exposure also caused pathological damage in gills, which compromised physiological function and decreased oxygen intake capacity of gills, thus leading to the enhancement of anaerobic metabolism. This finding was confirmed by the significant upregulation of lactate dehydrogenase in the liver of goldfish. Moreover, many phase I and phase II metabolic enzymes might be activated to alleviate TCCA-induced toxicity in goldfish, and glutathione S-transferases (GSTs) and cytochrome P450s (CYPs) play a crucial role in the metabolism of TCCA in the liver of goldfish. Furthermore, the antioxidant enzyme analysis showed that TCCA exposure induced oxidative damage in the liver and partially impaired the antioxidant defense system of goldfish, evidenced by decreased superoxide dismutase (SOD) and catalase (CAT), and increased malondialdehyde (MDA) level. In summary, this study will improve our understanding of the molecular mechanisms of the TCCA-induced toxicity in goldfish.

Dietary Lactobacillus casei K17 Improves Lipid Metabolism, Antioxidant Response, and Fillet Quality of Micropterus salmoides

Simple Summary

In order to find effective antioxidants to improve the fleshy degeneration and liver tissue lesions of Micropterus salmoides that were fed artificial mixed feed, Lactobacillus casei K17, which displayed a high level of antioxidant activity in vitro and in vivo was selected in this study. The results indicated that after a trial for 69 days, live bacteria (LB), live bacteria protected by skim milk powder (MB), and dead bacteria were able to improve hemal and hepatic lipid metabolism and antioxidant response, reduce reactive oxygen species production, and protect Micropterus salmoides hepatic cells from injury, while LB and MB were also able to improve fillet quality. Therefore, Lactobacillus casei K17 might be a good alternative source of improving fillet quality and liver health in Micropterus salmoides.

Abstract

We previously demonstrated that Lactobacillus casei K17, isolated from Korean kimchi, has high antioxidant levels in vitro and in vivo. However, its effect on Micropterus salmoides is unknown. In this study, we investigated the impact of L. casei K17 supplementation on the lipid metabolism, antioxidant response, liver histology, and fillet quality of M. salmoides. We randomly assigned 450 M. salmoides (33.0 ± 0.5 g) to six diet groups for 69 days. The diets were as follows: 0.85% normal saline; 10% skim milk powder; 1 × 10⁸ CFU/g live L. casei K17 (LB); 1 × 10⁸ live L. casei K17 protected by skim milk powder (MB); 1 × 10⁸ dead L. casei K17 (DB); and L. casei K17 fermentation supernatant. MB significantly improved the crude protein, total collagen, alkaline-insoluble collagen, fiber numbers, hardness, chewiness, and gumminess of M. salmoides fillets (p < 0.05). LB significantly improved crude protein and fiber numbers (p < 0.05). Furthermore, dietary supplementation with LB, MB, and DB maintained normal liver histology, preserved liver function, and increased hepatic and hemal antioxidant status by enhancing antioxidant enzyme activities. Meanwhile, the three diets also promoted lipid metabolism by increasing HDL-C effectiveness and reducing total cholesterol, triglyceride, and low-density lipoprotein cholesterol levels in serum and liver tissues, indicating that dietary supplementation with DB, LB, and MB had hypolipidemic effects on M. salmoides. MB and LB significantly improved fillet quality and LB, MB, and DB improved hemal and hepatic lipid metabolism and antioxidant response and reduced reactive oxygen species production, protecting M. salmoides hepatic cells from injury.

Selenium Nanoparticles Act Potentially on the Growth Performance, Hemato-Biochemical Indices, Antioxidative, and Immune-Related Genes of European Seabass (Dicentrarchus labrax)

The current study investigated the role of selenium (Se) nanoparticles on the growth performance, hemato-biochemical indices, antioxidative, and immune-related genes of European seabass (Dicentrarchus labrax). Therefore, fish with initial weight of 20.53 ± 0.10 g/fish were fed diets with 0, 0.25, 0.5, and 1 mg Se nanoparticles/kg diet for 90 days. The final body weight, weight gain, and specific growth rate of fish fed dietary nano-Se varying levels were significantly higher than the control with the highest performances and lowest FCR in the group of fish fed nano-Se at 0.5 mg/kg. The values of Hb, PCV, RBCs, and WBCs were significantly higher in fish fed varying levels of Se nanoparticles than fish fed the basal diets. The values of total serum protein and globulin were significantly higher in fish fed varying levels of Se nanoparticles than fish fed the basal diets. Additionally, globulin had higher value in the group of fish fed 0.25 and 0.5 mg nano-Se/kg than fish fed 1 mg nano-Se/kg (P < 0.05). No significant alterations were observed on albumin, ALT, and AST variables (P > 0.05). Phagocytic index, phagocytic, lysozyme activities were significantly higher in fish fed varying levels of Se nanoparticles than fish fed the basal diets in a dose dependent manner (P < 0.05). Further, SOD activity had higher value in the group of fish fed 0.25 and 0.5 mg nano-Se/kg than fish fed 1 mg nano-Se/kg, whereas CAT was increased in the group of fish fed dietary 0.5 mg nano-Se/kg diet (P < 0.05). The level of MDA was significantly lowered by dietary nano-Se where the group of fish fed 0.25 mg/kg had the lowest level followed by those fed 0.5 and 1 mg/kg. The expression of GH, IGF-1, IL-8, and IL-1β genes had the highest mRNA levels in the group of fish fed 0.25 and 0.5 mg/kg followed by those fed 1 mg/kg, whereas HSP70 was downregulated. Based on the overall results, Se nanoparticles are recommended at the rate of 0.5-1 mg/kg diet to maintain the optimal growth performance, hemato-biochemical indices, antioxidative status, and immune-related genes in European seabass.

Assessing the impacts of in-feed probiotic on the growth performance and health condition of pangasius (Pangasianodon hypophthalmus) in a farm trial

The effects of in-feed probiotics on growth performance, haematological parameters, gut microbial content, and morphological changes to pangasius fish were assessed. The trial had three phases, i.e., larvae to fry (20 days), fry to fingerlings (45 days), and grow-out phase from fingerlings to marketing (90 days). The stocking densities were 400 m^-3, 200 m^-3, and 12 m^-3 for phases 1, 2, and 3, respectively. Phases 1 and 2 were conducted in hapas in the same pond, whereas phase 3 was performed in concrete tanks. The in-feed probiotic was administered at a rate of 0.2 g kg^-1 of feed three times per day in phases 1 and 2 only. In phase 3, in-feed probiotics was not applied to any groups. The treated group exhibited higher growth performances (p < 0.05) than the control in all three phases of experiment. The survival % in phase 1 and 2 were found significantly (p < 0.05) higher in treatment groups. This indicates that pangasius nurserers would benefit from using probiotics as a safeguard to increase fry survival to a greater extent. Two haematological parameters including red blood cells (RBC) and white blood cells (WBC) levels were found significantly (p < 0.05) higher in treated groups in phase 2 and 3, while glucose and hemoglobin level were found significantly (p < 0.05) higher in the treated groups during phases 2 and 3, respectively. The gut microbiota content was relatively higher in the treated groups in phase 2 and 3. Histological findings indicate that the use of probiotics during the nursing phases of pangasius induced a positive change in the intestinal morphological structures. The positive impacts of probiotics on the phase 3 confirmed an immediate and long-term growth performance and health of pangasius.

Probiotics, Prebiotics, Synbiotics and Dental Caries. New Perspectives, Suggestions, and Patient Coaching Approach for a Cavity-Free Mouth

Probiotic therapy forms a new strategy for dental caries prevention. Probiotic microorganisms possess the ability to displace cariogenic microorganisms and colonize the oral cavity. They can produce various antimicrobial substances such as bacteriocins, bacteriocin-like peptides, lactic acid, and hydrogen peroxide. Dairy products may be ideal for probiotic administration in dental patients. Many other means have been proposed, primarily for those allergic to dairy components, such as capsules, liquid form, tablets, drops, lozenges, sweetened cakes, and ice creams. The last two forms can be used in a coaching approach for children and elderly patients who find it difficult to avoid sugary beverages in their daily routine and benefit from the suggestion of easy, cheap, and common forms of delicacies. In caries prevention, the concept of the effector strain is already considered an integral part of the contemporary caries cure or prevention strategy in adults. Adults, though, seem not to be favored as much as children at early ages by using probiotics primarily due to their oral microbiome’s stability. In this non-systematic review we describe the modes of action of probiotics, their use in the cariology field, their clinical potential, and propose options to prevent caries through a patient coaching approach for the daily dental practice.

Study on growth enhancement and the protective effects of dietary prebiotic inulin on immunity responses of rainbow trout (Oncorhynchus mykiss) fry infected with Aeromonas hydrophila

The present study evaluated the effects of dietary inulin on growth performance, body composition, serum, biochemical, and mucus immune factors; as well as innate immune responses of rainbow trout fry challenged with Aeromonas hydrophila. Four diets were prepared using a commercially available fish feed as a basal diet and different levels of prebiotic inulin incorporation; 0 (control), 1, 2, and 3%; referred to as C, T1, T2, and T3, respectively. The findings of the 60-day feeding trial showed that inulin inclusion affected final weight, food conversion rate (FCR), and specific growth rate (SGR) compared to that of the control group (P < 0.05), in which the lowest FCR was observed in T3. Body composition analysis revealed that inulin significantly increased protein content and decreased lipid levels, especially in the T1 and T2 groups. The lowest ash level was noticed in T2 (P < 0.05). Blood total protein, albumin, globulin, cholesterol, and glucose were not affected by inulin supplementation (P > 0.05). Analysis of humoral immune responses showed that the inulin supplements significantly increased lysozyme and complement activities (P < 0.05), as well as higher red blood cell count (RBC) and hemoglobin (Hb) in fish, fed 2% inulin, while no significant differences were observed among other treatments (P > 0.05). The mucosal parameters; including lysozyme, alkaline phosphatase (excluding ACH50); protease activities; and total immunoglobulin (IgM) improved significantly (P < 0.05), particularly in the T2 group. The T2 group also demonstrated the highest survival rate among all groups. The present findings indicate that dietary administration of inulin promotes growth and biochemical parameters, as well as serum immunity and mucosal immune responses of rainbow trout, in which a 2% inclusion produced the best results.

Gut immunity in European sea bass (Dicentrarchus labrax): a review

In this review, we summarize and discuss the trends and supporting findings in scientific literature on the gut mucosa immune role in European sea bass (Dicentrarchus labrax L.). Overall, the purpose is to provide an updated overview of the gastrointestinal tract functional regionalization and defence barriers. A description of the available information regarding immune cells found in two immunologically-relevant intestinal compartments, namely epithelium and lamina propria, is provided. Attention has been also paid to mucosal immunoglobulins and to the latest research investigating gut microbiota and dietary manipulation impacts. Finally, we review oral vaccination strategies, as a safe method for sea bass vaccine delivery.

Mannan oligosaccharides supplementation enhanced head-kidney and spleen immune function in on-growing grass carp (Ctenopharyngodon idella)

This research investigates the influences of dietary mannan oligosaccharides (MOS) on the head-kidney and spleen immune function in on-growing grass carp (Ctenopharyngodon idella) and its related mechanism. Fish were fed during 60 days at different levels of MOS (0, 200, 400, 600, 800 and 1000 mg kg^-1). Subsequently, 14 days after the feeding trial was injected intraperitoneally with Aeromonas hydrophila, the immune function was studied. The results are as follows: (1) appropriate MOS supplementation could increase the content of antibacterial compound and immunoglobulin (Ig), up-regulate antimicrobial peptides transcriptional levels in these two organs; (2) appropriate MOS supplementation attenuated inflammatory response in these two organs by regulating cytokines (pro- and anti-inflammatory cytokines) and related signalling pathways (NF-κB and TOR). The interesting points though, was, no differences were found in liver-expressed antimicrobial peptide (LEAP)-2A, interleukin (IL)-8, IL-4/13B, IκB kinase (IKK) α and nuclear factor kappa B (NF-κB) p52 gene expression in these two organs. Consequently, the present research suggests that MOS supplementation can enhance head-kidney and spleen immune function. Finally, we obtained these appropriate MOS dose (538.5 and 585.8 mg kg^-1) by quadratic regression analysis of lysozyme activity (head-kidney) and phosphatase activity (spleen), respectively.

Prebiotics and phytogenics functional additives in low fish meal and fish oil based diets for European sea bass (Dicentrarchus labrax): Effects on stress and immune responses

The use of terrestrial raw materials to replace fish meal (FM) and fish oil (FO) in marine fish diets may affect fish growth performance and health. In the last years functional additives have been profiled as good candidates to reduce the effects on health and disease resistance derived from this replacement, via reinforcement of the fish immune system. In the present study, three isoenergetic and isonitrogenous diets with low FM and FO (10% and 6% respectively) were tested based on supplementation either with 0.5% galactomannanoligosaccharides (GMOS diet) or 0.02% of a mixture of essential oils (PHYTO diet), a non-supplemented diet was defined as a control diet. Fish were fed the experimental diets in triplicate for 9 weeks and then they were subjected to a stress by confinement as a single challenge (C treatment) or combined with an experimental intestinal infection with Vibrio anguillarum (CI treatment). Along the challenge test, selected stress and immunological parameters were evaluated at 2, 24 and 168h after C or CI challenges. As stress indicators, circulating plasma cortisol and glucose concentrations were analyzed as well as the relative gene expression of cyp11b hydroxylase, hypoxia inducible factor, steroidogenic acute regulatory protein, heat shock protein 70 and heat shock protein 90 (cyp11b, hif-1α, StAR, hsp70 and hsp90). As immune markers, serum and skin mucus lysozyme, bactericidal and peroxidase activities were measured, as well as gene expression of Caspase-3 (casp-3) and interleukin 1β (il-1ß). The use of functional additives induced a significant (p < 0.05) reduction of circulating plasma cortisol concentration when confinement was the unique challenge test applied. Supplementation of PHYTO induced a down-regulation of cyp11b, hif-1α, casp-3 and il-1β gene expression 2h after stress test, whereas StAR expression was significantly (p < 0.05) up-regulated. However, when combination of confinement stress and infection was applied (CI treatment), the use of PHYTO significantly (p < 0.05) down-regulated StAR and casp-3 gene expression 2h after challenge test, denoting that PHYTO diet reinforced fish capacity of stress response via protection of head kidney leucocytes from stress-related apoptotic processes, with lower caspase-3 gene expression and a higher il-1β gene expression when an infection occurs. Additionally, dietary supplementation with GMOS and PHYTO compounds increased fish serum lysozyme after infection. Both functional additives entailed a better capability of the animals to cope with infection in European sea bass when fed low FM and FO diets.

Effects of a Trans-Galactooligosaccharide on Biochemical Blood Parameters and Intestine Morphometric Parameters of Common Carp (Cyprinus carpio L.)

Simple Summary

Prebiotics are important feed additives used in aquaculture. These are substances that are breeding grounds for beneficial bacteria and that inhibit the development of pathogens; accelerate healing and regeneration of the intestinal epithelium; increase mucus production; help maintain normal pH in the intestine; limit the growth of pathogenic bacteria; increase calcium, iron and magnesium absorption; and also have beneficial effects on glucose and protein metabolism in the liver. The saccharide-based prebiotic used in the carp experiment had a positive effect on intestine morphometric parameters. Supplementation of this prebiotic had no negative effect on growth performance and did not disturb the homeostasis of the fish, as demonstrated by the values of biochemical blood parameters.

Abstract

The aim of the study was to evaluate the effects of a trans-galactooligosaccharide prebiotic (GOS) on the growth performance, biochemical blood parameters, and intestine morphometric parameters of common carp. The 60-day-long experiment was performed on one-year-old fish with a mean body weight of 180 g (±5 g). Three diets were used: control diet 1 (C) with no microbiota affecting feed additives, diet 2 (B1) with 1% of prebiotic, and diet 3 (B2) with 2% of prebiotic, in four replications (tanks) per treatment and 25 fish per tank. At the end of the trial, 16 individuals from each group were used for analyses. The study showed that GOS supplementation did not affect growth performance. In turn, the prebiotic had a positive effect on the development of the intestine, and increased the height, width, and surface of the villi in B1 and B2 groups. The content of phosphorus (P) was significantly higher in B1 group compared with B2 group, which indicated that 1% addition of prebiotic causes better absorption of P from the intestine. The other biochemical indicators—namely lipid, protein and hepatic parameters, insulin, and Ca—were not affected by GOS treatment, which may indicate similar metabolic balance of fish in each experimental group. Serum triiodothyronine (TT₃) and glucose (stress markers) concentrations were not significantly different among treatments groups. GOS may be recommended as a feed additive for common carp due to its positive effects on fish physiology and development of the gastrointestinal tract. However, our results suggest that 1% diet supplementation causes satisfactory reactions for the abovementioned aspects in comparison to control or 2% supplementation.

V, Izquierdo M, Terova G. Assessment of dietary supplementation with galactomannan oligosaccharides and phytogenics on gut microbiota of European sea bass (Dicentrarchus Labrax) fed low fishmeal and fish oil based diet

There is an increasing interest from the aquafeed industry in functional feeds containing selected additives that improve fish growth performance and health status. Functional feed additives include probiotics, prebiotics, organic acids, and phytogenics (substances derived from plants and their extracts). This study evaluated the effects of dietary inclusion of a mucilage extract rich in galactomannan oligosaccharides (GMOS), a mixture of garlic and labiatae-plants oils (PHYTO), and a combination of them (GMOSPHYTO), on gut microbiota composition of European sea bass (Dicentrarchus labrax) fed with a low fishmeal (FM) and fish oil (FO) diet. Three experimental diets and a control diet (plant-based formulation with 10% FM and 6% FO) were tested in a 63-days feeding trial. To analyze the microbiota associated to feeds and the intestinal autochthonous (mucosa-adhered) and allochthonous (transient) microbial communities, the Illumina MiSeq platform for sequencing of 16S rRNA gene and QIIME2 pipeline were used. Metabarcoding analysis of feed-associated bacteria showed that the microbial communities of control (CTRL) feed deeply differed from those of experimental diets. The number of reads was significantly lower in CTRL feed than in other feeds. The OTU (operational taxonomic unit) number was instead similar between the feeds, ranging from 42 to 50 OTUs. The variation of resident gut microbiota induced by diet was lower than the variation of transient intestinal microbiota, because feedstuffs are a major source of allochthonous bacteria, which can temporarily integrate into the gut transient microbiome. However, the composition of transient bacterial communities was not simply a mirror of feed-borne bacteria. Indeed, the microbial profile of feeds was different from both faecal and mucosa profiles. Our findings suggest that the dietary inclusion of GMOS (0.5%) and PHYTO (0.02%) in a low FM and FO diet induces changes in gut microbiota composition of European sea bass. However, if on allochthonous microbiota the combined inclusion of GMOS and PHYTO showed an antagonistic effect on bactericidal activity against Vibrionales, at mucosa level, only GMOSPHYTO diet increased the relative abundance of Bacteroidales, Lactobacillales, and Clostridiales resident bacterial orders. The main beneficial effects of GMOS and PHYTO on gut microbiota are the reduction of coliforms and Vibrionales bacteria, which include several potentially pathogenic species for fish, and the enrichment of gut microbiota composition with butyrate producer taxa. Therefore, these functional ingredients have a great potential to be used as health-promoting agents in the farming of European sea bass and other marine fish.

Hypolipidemic Effects of β-Glucans, Mannans, and Fucoidans: Mechanism of Action and Their Prospects for Clinical Application

The search for lipid-lowering drugs is important for clinical medicine. This review summarizes our research findings regarding the hypolipidemic activity of polysaccharides. There are several validated agents altering lipid levels which reduce the risk of atherosclerotic cardiovascular events. Nonetheless, for many people, the risk of such an event remains unacceptably high despite treatment with these agents. This situation has prompted the search for new therapies to reduce the residual cardiovascular risk. The lipid-lowering effect of β-glucans consumed with food was demonstrated in patients with atherosclerosis. The mechanism of the protective effect of β-glucans is poorly studied. The effects of β-glucans are mediated by Toll-like receptors, by dectin-1, and possibly by other receptors. Nevertheless, the mechanism of the protective action of β-glucan in lipemic mice has been studied insufficiently. This review will present up-to-date information regarding experimental hypolipidemic polysaccharide compounds that hold promise for medicine. Phagocyte-specific chitotriosidase in humans contributes to innate immune responses against chitin-containing fungi. This enzyme has been first described in patients with Gaucher disease and serves as an important diagnostic biomarker. It has been reported that, in mice, chitin particles of certain size are recognized by macrophages through Toll-like receptors, dectin-1, and to a lesser extent through mannose receptor.

Effects of dietary arachidonic acid in European sea bass (Dicentrarchus labrax) distal intestine lipid classes and gut health

The use of low fishmeal/fish oil in marine fish diets affects dietary essential fatty acids (EFAs) composition and concentration and, subsequently, may produce a marginal deficiency of those fatty acids with a direct impact on the fish intestinal physiology. Supplementation of essential fatty acids is necessary to cover the requirements of the different EFAs, including the ones belonging to the n-6 series, such as arachidonic acid (ARA). ARA, besides its structural role in the configuration of the lipid classes of the intestine, plays an important role in the functionality of the gut-associated immune tissue (GALT). The present study aimed to test five levels of dietary ARA (ARA0.5 (0.5%), ARA1 (1%), ARA2 (2%), ARA4 (4%), and ARA6 (6%)) for European sea bass (Dicentrarchus labrax) juveniles in order to determine (a) its effect in selected distal intestine (DI) lipid classes composition and (b) how these changes affected gut bacterial translocation rates and selected GALT-related gene expression pre and post challenge. No differences were found between distal intestines of fish fed with the graded ARA levels in total neutral lipids and total polar lipids. However, DI of fish fed with the ARA6 diet presented a higher (P < 0.05) level of phosphatidylethanolamine (PE) and sphingomyelin (SM) than those DI of fish fed with the ARA0.5 diet. In general terms, fatty acid profiles of DI lipid classes mirrored those of the diet dietary. Nevertheless, selective retention of ARA could be observed in glycerophospholipids when dietary levels are low (diet ARA0.5), as reflected in the higher glycerophospholipids-ARA/dietary-ARA ratio for those animals. Increased ARA dietary supplementation was inversely correlated with eicosapentaenoic acid (EPA) content in lipid classes, when data from fish fed with the diets with the same basal composition (diets ARA1 to ARA6). ARA supplementation did not affect intestinal morphometry, goblet cell number, or fish survival, in terms of gut bacterial translocation, along the challenge test. However, after the experimental infection with Vibrio anguillarum, the relative expression of cox-2 and il-1β were upregulated (P < 0.05) in DI of fish fed with the diets ARA0.5 and ARA2 compared with fish fed with the rest of the experimental diets. Although dietary ARA did not affect fish survival, it altered the fatty acid composition of glycerophospholipids and the expression of pro-inflammatory genes after infection when included at the lowest concentration, which could be compromising the physical and the immune functionality of the DI, denoting the importance of ARA supplementation when low FO diets are used for marine fish.

Influence of dietary fermented Saccharomyces cerevisiae on growth performance, oxidative stress parameters, and immune response of cultured Oreochromis niloticus

Our trial was performed to investigate the effect of fully fermented yeast Sacharomyces cerevisiae (Hilyses, ICC Company, Brazil) on the growth performance and immune response of Oreochromis niloticus. In this study, a total of 270 O. niloticus (50.7 ± 0.8 g) were randomly divided into 3 groups in triplicates. The control group was fed on the basal diet while the other two groups were fed on a basal diet supplemented with 0.2% and 0.4% of Hilyses. The trial period extended for 2 months. At the end of the feeding trial, oxidant and antioxidant parameters (MDA, catalase, and glutathione reductase), some innate immunological parameters and immune-related gene expression were measured. Histological examination of liver, spleen, kidney, and intestine was performed. Further, fish groups were challenged against Gram-negative and Gram-positive bacteria; A. hydrophila and L. garvieae. The results revealed significant improvement (p < 0.05) in growth performance and feed utilization in Hilyses-treated groups versus the control group. Blood parameters and liver and kidney functions of Hilyses-supplemented groups were similar to those of the control group. The histological findings of treated groups showed normal tissue structure with multiple focal lymphoid aggregations in the spleen, kidney, and intestine. Both levels of Hilyses successfully enhanced phagocytic activity/index, lysozyme activity, and gene expression of TNF-α, and IL-1β. Fish group fed on 0.4% Hilyses exhibited the highest expression of IL-1β and the least mortality percentages post challenges. Thus, dietary supplementation of Hilyses could promote the growth performance and immunity and increase the resistance of O. niloticus against diseases.

Recombinant DnaK Orally Administered Protects Axenic European Sea Bass Against Vibriosis

Vibrio anguillarum causes high mortality in European sea bass (Dicentrarchus labrax) larviculture and is a hindering factor for successful sustainable aquaculture of this commercially valuable species. Priming of the innate immune system through administration of immunostimulants has become an important approach to control disease outbreaks in marine fish larviculture. This study was conducted to evaluate immunostimulation by Escherichia coli HSP70 (DnaK) in axenic European sea bass larvae in order to protect the larvae against vibriosis. DnaK stimulates the immune response in crustaceans and juvenile fish against bacterial infections. The use of axenic fish larvae allows to study immunostimulation in the absence of an interfering microbial community. At 7 days post-hatching, larvae received a single dose of alginate encapsulated recombinant DnaK. Two non-treated control groups in which animals either received empty alginate microparticles (C1) or no alginante microparticles (C2 and C3) were included in the study. Eighteen hours later, all larvae, except the ones from group C3 (non-infected control) were challenged with V. anguillarum (10⁵ CFU, bath infection). Mortality was daily recorded until 120 h post infection and at 18, 24, and 36 h post infection, larvae were sampled for expression of immune related genes. Results showed that V. anguillarum induced an immune response in axenic sea bass larvae but that the innate immune response was incapable to protect the larvae against deadly septicaemic disease. In addition, we showed that administration of alginate encapsulated DnaK to axenic European sea bass larvae at DAH7 resulted in a significant, DnaK dose dependent, upreglation of immune sensor, regulatory and effector genes. Significant upregulation of cxcr4, cas1 and especially of hep and dic was correlated with significant higher survival rates in V. anguillarum infected larvae. In the future recombinant DnaK might perhaps be used as a novel immunostimulant in sea bass larviculture.

Effects of Polyphenol Administration to European Farmed Sea Bass (Dicentrharcus labrax L.): Special Focus on Hepatopancreas Morphology

BACKGROUND AND OBJECTIVE

Hepatopancreas is an accessory organ associated with the liver in some fish, even including sea bass (Dicentrharcus labrax L.). Hepatopancreas contains an exocrine portion but until now its function has poorly been investigated.

METHODS

Here, European farmed sea bass have been treated with a feed enriched in polyphenols extracted from seeds of red grape (Nero di Troia cultivar) at two different doses (100 and 200 mg/kg, respectively) from day 273 to day 323. In fish samples, hepatopancreas area sizes have been measured to evaluate the effects of this dietary regimen on its morphology.

RESULTS

Quite interestingly, in treated fish area sizes of hepatopancreas were higher than those detected in untreated fish. Two hundred mg dose of polyphenols was more effective than that of 100 mg/kg polyphenols. Finally, hepatic polyphenol concentration was diminished in fish receiving 100 mg dose polyphenols and normalized with 200 mg dose in comparison to untreated fish. This evidence suggests the utilization of polyphenols for liver function, even including hepatopancreas development.

CONCLUSION

Our data suggest an expansion of hepatopancreas induced by polyphenol administration that is also associated with less mortality in farmed fish.

Mannan oligosaccharide increases the growth performance, immunity and resistance capability against Vibro Parahemolyticus in juvenile abalone Haliotis discus hannai Ino

This trial was conducted to investigate the effect of mannose oligosaccharides (MOS) on the growth performance, antioxidation, immunity and disease resistance of Vibro Parahemolyticus in juvenile abalone Haliotis discus hannai Ino. Four formulated diets were produced to contain 0.00 g/kg, 0.40 g/kg, 0.80 g/kg and 1.60 g/kg Actigen®, with functional ingredients of MOS, respectively. Accordingly, the experimental diets were named as A0, A4, A8 and A16. After 120-days feeding trial, the best growth performance was observed in A8 group (P < 0.05) and there was no significant difference in A0, A4 and A16 groups. With the increase of dietary MOS, the activity of the total antioxidant capacity in hepatopancreas is increasingly elevated (P < 0.05) while no significant difference was observed on activity of glutathione S-transferase (P > 0.05). The activities of superoxide dismutase and glutathione peroxidase were firstly increased and then decreased, with the highest values in A8 group (P < 0.05). Immune-related parameters were significantly affected by dietary MOS inclusion. Specifically, the activities of alkaline phosphatase and acid phosphatase in hepatopancreas and serum of abalone fed diets containing MOS were significantly higher than those of control A0 group (P < 0.05). Moreover, the highest values of both enzymes were observed in hepatopancreas of A8 group but in serum of A16 group, respectively. The lysozyme activities in hepatopancreas and serum of A4 group were significantly higher than those of other groups (P < 0.05) and there was no significant difference in A0, A8 and A16 groups (P > 0.05). The activities of cytophagy and respiratory burst in serum of abalone were not significantly affected by dietary MOS content (P > 0.05). The mRNA levels of focal adhesion kinase and integrin-linked kinase were gradually elevated with the increase of dietary MOS, with the highest value recorded in A16 group (P < 0.05). The gene expression of caspse-3 in A8 group was dramatically higher than those of other groups (P < 0.05) and there was no significant difference in A0, A4 and A16 groups (P > 0.05). The mRNA level of nuclear factor-κB was not significantly affected by dietary MOS (P > 0.05). During 56 h of V. Parahemolyticus challenge period, the accumulated mortality rate of abalone fed diets containing MOS were significantly lower than that of control A0 group in each time point (P < 0.05). Overall, the lowest rate was happened in A8 group (P < 0.05). In conclusion, MOS inclusion in diet has obviously positive effect on growth, immunity and disease resistance capability of abalone, with the optimal level of Actigen® at 0.80 g/kg in diet.

Inhibitory Effect of Galactooligosaccharide on Skin Pigmentation

To investigate the effects of ingestion of galactooligosaccharide (GOS) on skin pigmentation, we conducted cell experiments and clinical trials. The effect of GOS on melanin accumulation was assessed in vitro using B16F10 cells. Moreover, melanin and erythema indexes following GOS consumption were explored during a double-blind, randomized, and placebo-controlled study, which included subjects divided by stratified block randomization to placebo or GOS. No cytotoxicity was observed at 70 mg/mL or lower GOS in B16F10 melanoma cells. Melanin accumulation was inhibited at 14 mg/mL or higher GOS. Upon ultraviolet B (UVB) irradiation, the survival of HaCaT cells (control) was reduced to 69.0% lower than baseline. A protective effect of GOS was observed upon treatment with 14~35 mg/mL GOS; however at 70 mg/mL, cells showed 64% viability compared to control cells irradiated with UVB. Delta values (Δ melanin index), which indicate the difference from the baseline melanin level, were significantly different to placebo (P<0.01) after 8 weeks. In the GOS group, delta values (Δ erythema index), which indicate the difference from baseline erythema level, also significantly differed from the placebo group (P<0.05) after 8 weeks. Our results suggest that intake of prebiotic GOS inhibits skin pigmentation and may represent a novel nutritional approach for skin care.

Dietary phytogenics and galactomannan oligosaccharides in low fish meal and fish oil-based diets for European sea bass (Dicentrarchus labrax) juveniles: Effects on gut health and implications on in vivo gut bacterial translocation

European sea bass were fed four low FM/FO (10%/6%) diets containing galactomannan oligosaccharides (GMOS), a mixture of garlic oil and labiatae plants oils (PHYTO), or a combination of both functional products (GMOSPHYTO) for 63 days before exposing the fish to an intestinal Vibrio anguillarum infection combined with crowding stress. In order to evaluate functional diets efficacy in terms of gut health maintenance, structural, cellular, and immune intestinal status were evaluated by optical and electron microscopy and gene expression analyses. A semi-automated software was adapted to determine variations in goblet cell area and mucosal mucus coverage during the challenge test. Feeding with functional diets did not affect growth performance; however, PHYTO and GMOS dietary inclusion reduced European sea bass susceptibility to V. anguillarum after 7 days of challenge testing. Rectum (post-ileorectal valve) showed longer (p = 0.001) folds than posterior gut (pre-ileorectal valve), whereas posterior gut had thicker submucosa (p = 0.001) and higher mucus coverage as a result of an increased cell density than rectum. Functional diets did not affect mucosal fold length or the grade of granulocytes and lymphocytes infiltration in either intestinal segment. However, the posterior gut fold area covered by goblet cells was smaller in fish fed GMOS (F = 14.53; p = 0.001) and PHYTO (F = 5.52; p = 0.019) than for the other diets. PHYTO (F = 3.95; p = 0.049) reduced posterior gut goblet cell size and increased rodlet cell density (F = 3.604; p = 0.068). Dietary GMOS reduced submucosal thickness (F = 51.31; p = 0.001) and increased rodlet cell density (F = 3.604; p = 0.068) in rectum. Structural TEM analyses revealed a normal intestinal morphological pattern, but the use of GMOS increased rectum microvilli length, whereas the use of PHYTO increased (p≤0.10) Ocln, N-Cad and Cad-17 posterior gut gene expression. After bacterial intestinal inoculation, posterior gut of fish fed PHYTO responded in a more controlled and belated way in terms of goblet cell size and mucus coverage in comparison to other treatments. For rectum, the pattern of response was similar for all dietary treatments, however fish fed GMOS maintained goblet cell size along the challenge test.

Combined effects of ocean acidification and temperature on larval and juvenile growth, development and swimming performance of European sea bass (Dicentrarchus labrax)

Ocean acidification and ocean warming (OAW) are simultaneously occurring and could pose ecological challenges to marine life, particularly early life stages of fish that, although they are internal calcifiers, may have poorly developed acid-base regulation. This study assessed the effect of projected OAW on key fitness traits (growth, development and swimming ability) in European sea bass (Dicentrarchus labrax) larvae and juveniles. Starting at 2 days post-hatch (dph), larvae were exposed to one of three levels of PCO2 (650, 1150, 1700 μatm; pH 8.0, 7.8, 7.6) at either a cold (15°C) or warm (20°C) temperature. Growth rate, development stage and critical swimming speed (Ucrit) were repeatedly measured as sea bass grew from 0.6 to ~10.0 (cold) or ~14.0 (warm) cm body length. Exposure to different levels of PCO2 had no significant effect on growth, development or Ucrit of larvae and juveniles. At the warmer temperature, larvae displayed faster growth and deeper bodies. Notochord flexion occurred at 0.8 and 1.2 cm and metamorphosis was completed at an age of ~45 and ~60 days post-hatch for sea bass in the warm and cold treatments, respectively. Swimming performance increased rapidly with larval development but better swimmers were observed in the cold treatment, reflecting a potential trade-off between fast grow and swimming ability. A comparison of the results of this and other studies on marine fish indicates that the effects of OAW on the growth, development and swimming ability of early life stages are species-specific and that generalizing the impacts of climate-driven warming or ocean acidification is not warranted.

An evaluation of mixed plant protein in the diet of Yellow River carp (Cyprinus carpio): growth, body composition, biochemical parameters, and growth hormone/insulin-like growth factor 1

The aim of this work is to evaluate the effects of dietary inclusion of mixed plant protein (MP) (rapeseed meal:cottonseed meal:peanut meal = 1:1:1) on growth, body composition, blood biochemical parameters, growth hormone/insulin-like growth factor 1, and relative non-specific immune response in Yellow River carp Cyprinus carpio. Five isonitrogenous and isoenergetic trial diets were formulated to replace fish meal at 0 (MP0, control), 25% (MP25), 50% (MP50), 75% (MP75), and 100% (MP100) mixed plant protein, respectively. The 25% mixed plant protein did not affect the weight gain, specific growth rate, and protein efficiency ratio, whereas these parameters were depressed by 50% and above mixed plant protein. The whole body protein content gradually decreased with increasing dietary MP; meanwhile, the whole body lipid content is the opposite. The MP75 and MP100 diets adversely affected the glucose level, total cholesterol value, alanine transaminase, and aspartate transaminase activity of serum. Fish fed MP75 and MP100 diets showed higher growth hormone level than that of MP0 diet; however, the insulin-like growth factor 1 level got the opposite result. The 50% and above inclusion of MP decreased lysozyme activity and increased malondialdehyde content. In conclusion, no more than 50% of fish meal could be replaced by mixed plant protein in diet. However, 50% and above inclusion of mixed plant protein in diet could depress the growth, insulin-like growth factor 1 level, and non-specific immune response, and significantly affect the whole body composition and serum biochemical parameters in Yellow River carp.

Effects of dietary hydrolyzed yeast (Rhodotorula mucilaginosa) on growth performance, immune response, antioxidant capacity and histomorphology of juvenile Nile tilapia (Oreochromis niloticus)

An 8 weeks feeding experiment was conducted to evaluate the effects of dietary supplementation with hydrolyzed yeast (HY) (Rhodotorula mucilaginosa) on growth performance, hematological parameters, immune response and antioxidant ability of juvenile Nile tilapia. Five isonitrogenous and isolipidic diets (32% protein and 4% lipid) with different levels (0%, 0.125%, 0.25%, 0.5%, 1%) of HY were formulated. Each diet was randomly assigned to quadruplicate groups of fish (initial body weight 19.1 ± 0.01 g). Results indicated that significantly higher specific growth rate (SGR) and lower feed conversion rate (FCR) were obtained in fish fed 1% HY diet than that of fish fed 0% HY diet (P < 0.05). Fish fed 0.25% HY diet showed the lowest value of hepatopancreas somatic indices (HSI) and significantly lower than that of fish fed 0% HY diet (P < 0.05). Meanwhile, protein and ash in the whole-body content of fish fed 1% HY diet was significantly higher than that of fish fed 0%-0.5% HY diets. Serum immunological parameters showed that the lysozyme (LZM) activity and Complement C3 content were significantly increased by dietary supplementation of 0.5%-1% HY (P < 0.05). However, dietary supplementation with 0.125%-1% HY significantly decreased the activity of myeloperoxidase (MPO) (P < 0.05). Antioxidant status in serum and liver was significantly enhanced by dietary supplementation of 0.25%-1% HY through the remarkably improved superoxide dismutase (SOD) activity both in serum and liver, the raised total antioxidative capacity (T-AOC) of serum as well as the notably reduced malondialdehyde (MDA) content in the liver (P < 0.05). However, T-AOC in the liver was not significantly influenced among all diet treatments (P > 0.05). Villi height and intraepithelial lymphocytes (IEFs) of mid-intestine were significantly higher in fish fed 0.5%-1% HY diets (P < 0.05). The challenge test demonstrated the enhanced protection against Streptococcus iniae strain by the obtained higher cumulative survival rate. In conclusion, dietary supplementation of 1% HY could maintain the better growth performance, nutrient composition as well as immune response and antioxidant capacity for juvenile Nile tilapia.

Glucan and Mannan-Two Peas in a Pod

In recent decades, various polysaccharides isolated from algae, mushrooms, yeast, and higher plants have attracted serious attention in the area of nutrition and medicine. The reasons include their low toxicity, rare negative side effects, relatively low price, and broad spectrum of therapeutic actions. The two most and best-studied polysaccharides are mannan and glucan. This review focused on their biological properties.

The effects of dietary Lycium barbarum extract on growth performance, liver health and immune related genes expression in hybrid grouper (Epinephelus lanceolatus♂ × E. fuscoguttatus♀) fed high lipid diets

Growth performance, hepatic morphology and antioxidant ability, and expressions of antioxidant, inflammatory and apoptosis related genes were investigated in hybrid grouper fed high lipid diets containing 0, 0.5, 1, 2 and 10 g kg^-1Lycium barbarum extract (LBE) for 8-week feeding. The study showed that dietary LBE significantly increased weight gain rate (WGR) and specific growth rate (SGR) of fish (P < 0.05), the highest WGR and SGR were observed in fish fed 10.00 g kg^-1 LBE diet. Dietary LBE improved liver morphology by decreasing hepatocyte necrosis and inflammatory cell infiltration induced by high lipid diets. Meanwhile, high lipid diets supplemented with 0.5-2 g kg^-1 LBE improved hepatic antioxidant ability by increasing the expression of antioxidant genes (GPx and CAT) and decreasing Keap1 mRNA levels. Moreover, dietary supplementation with 0.50-2.00 g kg ^-1 LBE significantly decreased IL-8, caspase-3, caspase-8 and caspase-9 mRNA levels and significantly increased IL-10 and TGF-β1 mRNA levels in the liver of fish fed high lipid diets. In conclusion, high lipid diets supplemented with LBE improved growth performance, feed utilization and liver health in hybrid groupers by increasing hepatic antioxidant enzymes activity and its genes expression, as well as inhibition of hepatic inflammatory response and apoptosis.

Comparative immunostimulatory effect of probiotics and prebiotics in Channa punctatus against Aphanomyces invadans

In aquaculture and human health care probiotics and prebiotics have been widely used due to their important role in enhancing beneficial gut microbiota, promoting growth, increasing disease resistance, and positively modulating the host immune system. This study reports for the first time a comparative analysis on the effect of the probiotics and prebiotics on growth, digestive enzymes activity, antioxidant activity, and immune response in Channa punctatus against Aphanomyces invadans. Among the diets enriched with Saccharomyces cerevisiae (S. cerevisiae) and Galactooligosaccharide (GOS) in C. punctatus, feeding 2.5 g kg^-1 diet did not significantly influence the mean weight gain (MWG) between weeks 2 and 4 in both the infected and control groups; however the increase in MWG became significant from weeks 6-8. Similarly, during this period the protein efficiency ratio (PER), feed conversion ratio (FCR) and protein intake (PI) did not increase significantly. The intestinal protease, lipase, and amylase enzyme activities also did not increase significantly between weeks 2 and 4, whereas the values increased significantly after 6 weeks in both groups when fed with dietary supplementation of S. cerevisiae and GOS. The total S. cerevisiae count significantly increased in the gut of infected and non-infected fish fed with S. cerevisiae and GOS diets while the total bacterial (TB) count decreased between weeks 6 and 8. The total superoxide dismutase (t-SOD) activity and the malonaldehyde (MDA) concentration increased significantly in the non-infected fish fed with S. cerevisiae and GOS supplementation diets between weeks 6 and 8 whereas the catalase (CAT) and glutathione peroxidase (GPx) activities increased significantly only on week 8. The innate immune parameters such as plasma lysozyme, acid phosphatase (ACP), and myeloperoxidase (MPO) activities increased significantly in the infected and non-infected fish fed with S. cerevisiae and GOS containing diets after 6 weeks. Similarly, the plasma nitric oxide (NO) level and total protein (TP) content significantly increased in the non-infected fish fed with S. cerevisiae and GOS containing diets between weeks 6 and 8. In the control and the non-infected fish fed with S. cerevisiae and GOS enriched diets caused no mortality whereas 15% and 10% mortality was observed in the infected fish fed with S. cerevisiae and GOS diets, respectively. This study indicates that the infected and non-infected C. punctatus fed with dietary supplementation of GOS diet at 2.5 g kg^-1 had exhibited better growth performance, digestive enzyme activities, gut microbiota composition, and immune response than that of S. cerevisiae diet.

Increased parasite resistance of greater amberjack (Seriola dumerili Risso 1810) juveniles fed a cMOS supplemented diet is associated with upregulation of a discrete set of immune genes in mucosal tissues

The main objective of this study was to determine the effect of two forms of mannan oligosaccharides (MOS: Bio-Mos^® and cMOS: Actigen^®, Alltech Inc, USA) and their combination on greater amberjack (Seriola dumerili) growth performance and feed efficiency, immune parameters and resistance against ectoparasite (Neobenedenia girellae) infection. Fish were fed for 90 days with 5 g kg^-1 MOS, 2 g kg^-1 cMOS or a combination of both prebiotics, in a Seriola commercial base diet (Skretting, Norway). At the end of the feeding period, no differences were found in growth performance or feed efficiency. Inclusion of MOS also had no effect on lysozyme activity in skin mucus and serum, but the supplementation of diets with cMOS induced a significant increase of serum bactericidal activity. Dietary cMOS also reduced significantly greater amberjack skin parasite levels, parasite total length and the number of parasites detected per unit of fish surface following a cohabitation challenge with N. girellae, whereas no effect of MOS was detected on these parameters. Of 17 immune genes studied cMOS dietary inclusion up-regulated hepcidin, defensin, Mx protein, interferon-γ (IFNγ), mucin-2 (MUC-2), interleukin-1β (IL-1B), IL-10 and immunoglobulin-T (IgT) gene expression in gills and/or skin. MOS supplementation had a larger impact on spleen and head kidney gene expression, where piscidin, defensin, iNOS, Mx protein, interferons, IL-1β, IL-10, IL-17 and IL-22 were all upregulated. In posterior gut dietary MOS and cMOS both induced IL-10, IgM and IgT, but with MOS also increasing piscidin, MUC-2, and IL-1β whilst cMOS induced hepcidin, defensin and IFNγ. In general, the combination of MOS and cMOS resulted in fewer or lower increases in all tissues, possibly due to an overstimulation effect. The utilization of cMOS at the dose used here has clear benefits on parasite resistance in greater amberjack, linked to upregulation of a discrete set of immune genes in mucosal tissues.

Effects of partial replacement of fish meal by yeast hydrolysate on antioxidant capability, intestinal morphology, and inflammation-related gene expression of juvenile Jian carp (Cyprinus carpio var. Jian)

This study aimed to evaluate the effects of fish meal (FM) replacement by yeast hydrolysate (YH) on liver antioxidant capability, intestinal morphology, and inflammation-related genes of juvenile Jian carp (Cyprinus carpio var. Jian). A total of 600 fish (average initial weight 19.44 ± 0.06 g) were randomly selected and divided into five groups. Five isonitrogenous and isocaloric diets replacing FM by YH 0% (YH0), 1% (YH1), 3% (YH3), 5% (YH5), and 7% (YH7) were formulated. Each diet was tested in four replicates for 10 weeks. The results have shown that, compared to the control group (YH0), liver total superoxide dismutase (t-SOD), catalase (CAT), glutathione peroxidase (GPX), and glutathione (GSH) activities of fish fed YH1 and YH3 diets were significantly higher (P < 0.05). Liver malondialdehyde (MDA) concentration significantly increased as supplementation levels of YH increased from 1 to 7% (P < 0.05). Moreover, intestinal microvillus length of juvenile Jian carp fed YH diets were significantly higher than that of fish fed the control diet (P < 0.05). In proximal intestine, the relative expression levels of inflammation-related genes (ALP, IL-1β, and TNF-α) in YH7 were significantly higher than that in the control group (P < 0.05). However, in midintestine, the expression levels of these genes in YH3 were significantly lower compared to the control group (P < 0.05). The results of this study indicated that dietary replacement of FM by 3%YH could improve antioxidant capability and intestinal microvillus morphology, as well as enhance the non-specific immunity of juvenile Jian carp.

Dietary yeast culture modulates immune response related to TLR2-MyD88-NF-kβ signaling pathway, antioxidant capability and disease resistance against Aeromonas hydrophila for Ussuri catfish (Pseudobagrus ussuriensis)

The aim of the present study was to investigate effects of dietary yeast culture on immune response related to TLR2-MyD88-NF-kβ signaling pathway, antioxidant capability and disease resistance against Aeromonas hydrophila for Ussuri catfish (Pseudobagrus ussuriensis). A total of 240 Ussuri catfish (mean weight of 7.39 ± 0.32 g) were randomly distributed into four groups that fed diets containing 0 (Y0), 10 (Y1), 20 (Y2) and 30 (Y3) g kg^-1 yeast culture for 8 weeks. The results indicated that dietary 10 g kg^-1 yeast culture supplementation significantly down-regulated mRNA levels of TLR2, MyD88, NF-kβ p65, IL-1β and IL-8 in the liver tissue compared with the control group (P < 0.05). Simultaneously, serum lysozyme (LZM) activity, respiratory burst activity (RBA) of phagocytes, plasma alkaline phosphatase (AKP) activity and immunoglobulin M (IgM) content were significantly improved in fish fed Y1 diet (P < 0.05). Fish fed Y1 diet had significantly higher serum alternative complement pathway activity (ACH50) and plasma complement 3 (C3) content than the Y3 group (P < 0.05). However, no significant differences were observed in plasma acid phosphatase (ACP) activity and complement 4 (C4) content among the groups (P > 0.05). Fish cumulative mortality rate (CMR) in the Y1 and Y2 groups were significantly lower than that in Y0 and Y3 groups (P < 0.05), and the lowest CMR was observed in the Y1 group after challenge by A. hydrophila. The highest hepatic superoxide dismutase and glutathione peroxidase activities, total antioxidant capacity and the lowest malondialdehyde content were found in Y1 group, but no significant difference was found in hepatic catalase activity among the groups (P > 0.05). These results demonstrate that dietary 10 g kg^-1 yeast culture could effectively improve the immunity, antioxidant capability and disease resistance against A. hydrophila for Ussuri catfish and could down-regulate the mRNA expression levels of pro-inflammatory cytokines modulated by TLR2-MyD88-NF-kβ signaling pathway.

Feeding European sea bass (Dicentrarchus labrax) juveniles with a functional synbiotic additive (mannan oligosaccharides and Pediococcus acidilactici): An effective tool to reduce low fishmeal and fish oil gut health effects?

The aim of this study was to assess the effects of dietary mannan oligosaccharides (MOS), Pediococcus acidilactici or their conjunction as a synbiotic in low fish meal (FM) and fish oil (FO) based diets on European sea bass (Dicentrarchus labrax) disease resistance and gut health. For that purpose, sea bass juveniles were fed one of 6 diets containing different combinations of MOS (Biomos^® and Actigen^©; Alltech, Inc., Kentucky, USA) and Pediococcus acidilactici (BAC, Bactocell^®; Lallemand Inc., Cardiff, UK) replacing standard carbohydrates as follows (MOS (%)/BAC (commercial recommendation): high prebiotic level (HP) = 0.6/0, low prebiotic level (LP) = 0.3/0, only probiotic (B) = 0/+, high prebiotic level plus probiotic (HPB) = 0.6/+, low prebiotic level plus probiotic (LPB) = 0.3/+, control (C) = 0/0 for 90 days. After 60 and 90 days of feeding trial, fish were subjected to an experimental infection against Vibrio anguillarum. Additionally, inducible nitric oxide synthase (iNOS) and tumor necrosis factor α (TNFα) gut patterns of immunopositivity and major histocompatibility complex class II (MHCII), transforming growth factor β (TGF-β), regulatory T-cell subset (CD4⁺T lymphocytes) and effector T cell (CD8α⁺T lymphocytes) gene expression patterns in gut by in situ hybridization were evaluated after 90 days of feeding. The effects of both additives on posterior gut through Gut Associated Lymphoid Tissue (GALT) gene expression was also studied. Fish fed the prebiotic and its combination with P. acidilactici presented increased weight regardless of the dose supplemented after 90 days of feeding, however no effect was detected on somatic indexes. For posterior gut, morphometric patterns and goblet cells density was not affected by MOS, P. acidilactici or its combination. Anti-iNOS and anti-TNFα gut immunopositivity patterns were mainly influenced by MOS supplementation and not by its combination with P. acidilactici. MHCII-β, TCR-β, CD4 and CD8-α positive cells distribution and incidence was not affected by diet. Fish fed HP dose presented a clear up-regulation of TNF-α, cyclooxygenase-2 (COX-2), CD4 and IL10, whereas P. acidilactici dietary supplementation increased the number of interleukin-1β (IL1β) and COX-2 gene transcripts. Synbiotic supplementation resulted in a reduction of MOS-induced gut humoral proinflammatory response by increasing the expression of some cellular-immune system related genes. Fish mortality after V. anguillarum infection was reduced in fish fed LPB and LP diets compared to fish fed the non-suppelmented diet after 90 days of feeding. Thus, overall pointing to the combination of a low dose of MOS and P. acidilactici as synbiont (LPB) as a viable tool to potentiate European sea bass juvenile's growth and disease resistance when supplemented in low FM and FO diets.