Dietary sodium propionate affects mucosal immune parameters, growth and appetite related genes expression: Insights from zebrafish model

Effects of dietary powdered Ficus deltoidea on the growth and health performance of African catfish, Clarias gariepinus production

Intensive aquaculture causes a decline in the health status of fish, resulting in an increased disease incidence. To counteract this, feed additives have been utilized to improve the growth performance and health of aquaculture species. This work specifically investigates the impact of powdered Ficus deltoidea (FD) on various parameters related to growth, blood parameters, liver and intestine morphology, body proximate analysis, digestive enzymes, antioxidant capacity, and disease resistance to motile Aeromonad Septicemia (MAS) caused by Aeromonas hydrophila infection in African catfish, Clarias gariepinus. Four formulated diets were prepared: T1 (0% FD), T2 (0.5% FD), T3 (0.75% FD), and T4 (1% FD). After 8 weeks, the African catfish's growth performance fed with the T2 diet exhibited a substantial improvement (p < 0.05), along with a remarkably lower (p < 0.05) feed conversion ratio (FCR) when compared to the other treatment groups. Blood parameter analysis revealed notably higher (p < 0.05) levels of white blood cell (WBC), lymphocytosis (LYM), hemoglobin (HGB), albumin (ALB), globulin (GLOB), as well as total protein (TP) in the T2 diet group. While all treatment groups displayed normal intestinal morphology, liver deterioration was observed in groups supplemented with higher FD. The T2 diet group recorded the highest villus length, width, and crypt depth. Protease and lipase levels were also notably improved in the T2 diet group compared to other treatment groups. Additionally, catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) were remarkably elevated in all FD diet groups than in the control group. The expression of immune-related genes, including transforming growth factor beta 1, heat shock protein 90, nuclear factor kappa-B gene, and lysozyme G, was upregulated in all treatments. Overall, the results of this study indicate that incorporating dietary FD at 0.5% concentration in the diet of African catfish may enhance their productivity in intensive farming.

Buspirone administration: Influence on growth, spawning, immune response, and stress in female goldfish (Carassius auratus)

The current study evaluated the impact of buspirone supplementation on the growth, physiology, stress response, spawning, and immunity in female goldfish (Carassius auratus). For this purpose, buspirone was dissolved in absolute methanol and sprayed onto the feed to create four experimental groups: B0 (control), B25 (25 mg kg-1), B50 (50 mg kg-1), and B100 (100 mg kg-1). Fish were fed their respective diets for 56 days and subjected to stress using the air exposure method at the end of the experiment. Growth performance analysis revealed that fish in the B100 group exhibited significantly higher final weight, weight gain, specific growth rate, and average daily gain than the other groups (P < 0.05). Plasma stress response indicated that cortisol levels were significantly lower in the B100 group after stress exposure, accompanied by a simultaneous decrease in glucose levels. The mucus stress response also showed lower cortisol and glucose levels in the B100 group compared to the other groups. Immunological analysis revealed significant increases in total protein, albumin, complement C3 and C4, and immunoglobulin M concentrations in both plasma and mucus of the B100 group (P < 0.05). Reproductive performance showed a notable enhancement in the number of eggs, fertilization rate, hatching rate, and survival rate in the B100 group compared to other groups (P < 0.05). Buspirone at higher concentrations, positively impacted various physiological aspects of goldfish, including growth, stress, immune activity, and reproductive performance. The significant improvements observed in growth parameters, cortisol levels, immunological markers, and reproductive outcomes suggest the potential of buspirone supplementation as a beneficial strategy in aquaculture practices.

Dietary sulfated polysaccharides extracted from Caulerpa sp. and Padina sp. modulated physiological performance, antibacterial activity and ammonia challenge test in juvenile rainbow trout (Oncorhynchus mykiss)

Nowadays, the use of seaweed derivatives in aquaculture has drawn attention for their potential as an immunostimulant and growth promotor. The sulfated polysaccharide extracted (SPE ) from green (Caulerpa sp.; SPC) and brown (Padina sp.; SPP) seaweeds with two concentrations (0.05% and 0.1%); nominated in four groups: SPC0.05 , SPC0.1 , SPP0.05 , SPP0.1 and control group (free of SPE ) were used for juvenile rainbow trout (Oncorhynchus mykiss) diet. Fish (N: 150; 8.5 ± 0.2 g) were selected aleatory distributed in 15 circular tanks (triplicate for the group) and fed test diets for 56 days. The outcomes revealed that the supplementation of SPE up to 1 g kg-1 failed to show significant differences in the organosomatic indices as compared to the control group. The most inferior protein value of dress-out fish composition was observed in the fish fed the control diet, which was statistically lower than the SCP0.1 group (p < 0.05), while no significant difference was observed in other macronutrient composition among the treatments. Total monounsaturated fatty acid (MUFA) had lower trend in the carcass of fish fed SPE supplemented diets, so that lowest MUFA were observed in SPC0.05 group (p < 0.05; 25.22 ± 4.29%). The lowest value of docosahexaenoic acid was observed in the control diet compared to the SPE -supplemented diets (p < 0.05). The serum alternative complement pathway levels in all treatments tend to promote compared to the control treatment. A similar trend was observed for lysozyme activity. According to the results, the superoxide dismutase (SOD) value were highest in SPC0.05 and SPC0.1 compared to the other treatments (p < 0.05), while a further elevation of the SPE Padina sp. extracted level (SPP0.1 ) leads to a decrease in SOD value. Thiobarbituric acid reactive substances of plasma was indicated not to influence by sulfated polysaccharide extracts in the refrigerated storage. The lowest serum stress indicators were observed in fish fed SPP0.05 group postchallenge test. Taken together, our outcomes revealed that SPE of two species of seaweeds bestows benefits in some of the immunity and antioxidant system. Also, notable elevations in HUFA were observed in juvenile rainbow trout fed supplemented with SPE .

Exogenous 2-keto-L-gulonic Acid Supplementation as a Novel Approach to Enhancing L-ascorbic Acid Biosynthesis in Zebrafish (Danio rerio)

L-ascorbic acid (ASA) is a micronutrient that is essential for reproduction, growth, and immunity in animals. Due to the loss of enzyme L-gulono-1,4-lactone oxidase (GLO), most aquatic animals lack the capacity for ASA biosynthesis and therefore require supplementation with exogenous ASA. Recent studies have shown that 2-keto-L-gulonic acid (2KGA), a novel potential precursor of ASA, can enhance plant growth and improve stress resistance by promoting the synthesis and accumulation of ASA. Our hypothesis is that 2-keto-L-gulonic acid (2KGA) plays a similar role in aquatic animals. To investigate this, we conducted an in vivo trial to examine the effects of exogenous 2KGA supplementation on ASA metabolism and growth of zebrafish (Danio rerio). Zebrafish were categorized into groups based on their dietary intake, including a basal diet (CK group), a basal diet supplemented with 800 mg/kg ASA (ASA group), and 800 mg/kg 2KGA-Na (2KGA group) for a duration of three weeks. The results demonstrated a significant increase in ASA content in zebrafish treated with 2KGA (34.82% increase, p < 0.05) compared to the CK group, reaching a consistent level with the ASA group (39.61% increase, p < 0.05). Furthermore, the supplementation of 2KGA significantly improved growth parameters relevant to zebrafish (specific growth rate increased by 129.04%, p < 0.05) and enhanced feed utilization (feed intake increased by 15.65%, p < 0.05). Positive correlations were observed between growth parameters, feed utilization, whole-body chemical composition, and ASA content. Our findings suggest that supplementation with exogenous 2KGA can serve as a novel approach for elevating ASA synthesis in aquatic animals, and further investigation of its underlying mechanism is required.

Effects of dietary nutmeg (Myristica fragrans) seed meals on growth, non-specific immune indices, antioxidant status, gene expression analysis, and cold stress tolerance in zebrafish (Danio rerio)

Introduction

A medicinal plant, Myristica fragrans seed meal (nutmeg), was utilized to evaluate its impact on the growth, immunity, and antioxidant defense of zebrafish (Danio rerio).

Methods

In this regard, zebrafish (0.47 ± 0.04 g) (mean ± S.D.) were fed with 0% (control), 1% (T1-nutmeg), 2% (T2-nutmeg), and 3% (T3-nutmeg) of powdered nutmeg for 70 days. At the end of the feeding trial, growth performance, survival rate of fish, and temperature-challenge effects were recorded. Immune and antioxidant parameters were also assessed through the collection of serum and skin mucus samples.

Results

The results indicated that nutmeg supplementation did not significantly influence the growth of zebrafish (P > 0.05); however, the survival rate of fish fed with 2 and 3% of nutmeg supplementation significantly decreased (P < 0.05). The skin mucus and serum total protein, total immunoglobulin (Ig), and lysozyme activity were significantly increased in T3-nutmeg treatment in comparison to the control (P < 0.05). Superoxide dismutase (SOD) and catalase (CAT) activities were also enhanced in the T3-nutmeg group (P < 0.05). Nutmeg supplementation significantly upregulated the mRNA expression of growth hormone (gh) and insulin growth factor-1 (igf-1). Moreover, the nutmeg inclusion upregulated the expression of interleukin-1β (IL-1β), lysozyme, sod, and cat. The dietary supplementation of nutmeg significantly increased the resistance of zebrafish against cold-water shock and survivability afterward (P < 0.05).

Discussion

In conclusion, the supplementation of 3% powdered nutmeg in zebrafish diets could be suggested as an effective immune stimulator that improves antioxidant defense and stress tolerance.

Bioactive immunostimulants as health-promoting feed additives in aquaculture: A review

Bioactive immunostimulants could be derived from different sources like plants, animals, microbes, algae, yeast, etc. Bioactive immunostimulants are the most significant role to enhance aquatic production, as well as the cost of this method, which is effective, non-toxic, and environment-friendly. These immunostimulants are supportive to increase the immune system, growth, antioxidant, anti-inflammatory, and disease resistance of aquatic animals' health and also improve aquatic animal feed. Diseases are mainly targeted to the immune system of aquatic organisms in such a way that different processes of bioactive immunostimulants progress are considered imperative techniques for the development of aquaculture production. Communicable infections are the main problem for aquaculture, while the mortality and morbidity connected with some outbreaks significantly limit the productivity of some sectors. Aquaculture is considered the mainly developing food production sector globally. Protein insists is an important issue in human nutrition. Aquaculture has been an exercise for thousands of years, and it has now surpassed capture fisheries as the most vital source of seafood in the world. Limited study reports are available to focal point on bioactive immunostimulants in aquaculture applications. This review report provides information on the nutritional administration of bioactive immunostimulants, their types, functions, and beneficial impacts on aquatic animals' health as well as for the feed quality development in the aquaculture industry. The scope of this review combined to afford various kinds of natural derived bioactive molecules utilization and their beneficial effects in aquaculture applications.

Effect of a diet enriched with sodium propionate on growth performance, antioxidant property, innate-adaptive immune response, and growth-related genes expression in critically endangered beluga sturgeon (Huso huso)

Organic acids are active substances required for improving the productivity and wellbeing of aquatic animals. Herein, the study investigated the effects of sodium propionate on growth performance, antioxidative and immune responses, and growth-related genes expression in beluga sturgeon (Huso huso). For eight weeks, fish fed sodium propionate at 0, 1.2, 2.5, and 5 g kg^-1. The final weight, weight gain, and SGR were substantially increased while FCR decreased by dietary sodium propionate at 2.5 and 5 g kg^-1 (P < 0.05). The expression of Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) was markedly upregulated (P < 0.05) by dietary sodium propionate in the gills and livers of beluga. The highest mRNA level of GH and IGF-1 has been observed in fish fed a 2.5 g sodium propionate/kg diet. The red blood cells count, and hemoglobin level were meaningfully increased (P < 0.05) by 2.5 and 5 g sodium propionate/kg diet compared with 0 and 1.2 g kg^-1 levels. Further, the hematocrit level was increased (P < 0.05) by a dietary 5 g sodium propionate/kg diet. The total protein level and lysozyme activity were meaningfully increased (P < 0.05) by 2.5 and 5 g sodium propionate/kg diet compared with 0 and 1.2 g kg^-1 levels. The highest superoxide dismutase was observed in fish fed 2.5 g sodium propionate/kg diet. Catalase activity was significantly higher in fish fed 5 g kg^-1 than 1.2 g kg^-1. The glutathione peroxidase activity was markedly higher in fish fed 2.5, and 5 g kg^-1 than fish fed control diet. The lowest malondialdehyde levels were observed in fish fed 1.2, and 2.5 g sodium propionate/kg diets. Moreover, the highest mucosal total protein, total immunoglobulin and lysozyme were recorded in fish fed 2.5, and 5 g sodium propionate/kg diets. The obtained results indicate that dietary sodium propionate is recommended at 2.5-5 g kg^-1 to improve beluga sturgeon's growth performance, feed utilization, and wellbeing.

Application of zebrafish in the study of the gut microbiome

Zebrafish (Danio rerio) have attracted much attention over the past decade as a reliable model for gut microbiome research. Owing to their low cost, strong genetic and development coherence, efficient preparation of germ-free (GF) larvae, availability in high-throughput chemical screening, and fitness for intravital imaging in vivo, zebrafish have been extensively used to investigate microbiome-host interactions and evaluate the toxicity of environmental pollutants. In this review, the advantages and disadvantages of zebrafish for studying the role of the gut microbiome compared with warm-blooded animal models are first summarized. Then, the roles of zebrafish gut microbiome on host development, metabolic pathways, gut-brain axis, and immune disorders and responses are addressed. Furthermore, their applications for the toxicological assessment of aquatic environmental pollutants and exploration of the molecular mechanism of pathogen infections are reviewed. We highlight the great potential of the zebrafish model for developing probiotics for xenobiotic detoxification, resistance against bacterial infection, and disease prevention and cure. Overall, the zebrafish model promises a brighter future for gut microbiome research.

The Combined Effects of Propionic Acid and a Mixture of Bacillus spp. Probiotic in a Plant Protein-Rich Diet on Growth, Digestive Enzyme Activities, Antioxidant Capacity, and Immune-Related Genes mRNA Transcript Abundance in Lates calcarifer Fry

A 7-week feeding trial was conducted to evaluate the combined effects of propionic acid (PA, 5 or 10 g/kg) and a multi-strain Bacillus spp. (Bacillus subtilis IS02 (accession no. JN856456) and B. licheniformis IBRC-M 11,319) (1.7 × 10⁷ CFU/g) probiotic in a plant protein source (PP)-rich diet (∼70% of dietary protein derived from PP sources) on performance of Asian sea bass (Lates calcarifer) fry (initial body weight 2.97 ± 0.11 g). In this regard, six isoproteic (∼48%) diets were formulated as follows: a control (without supplementation of the additives); probiotic (only contained Bacillus spp. mixture); 5 g PA/kg diet; 10 g PA/kg diet; probiotic + 5 g PA/kg diet, and probiotic + 10 g PA/kg diet. Specific growth rate in fish fed with 10 g PA/kg (2.84 ± 0.1%) and diets contained blends of probiotic and PA (2.76 ± 0.19% in probiotic + 5 g PA, and 2.79 ± 0.04% in probiotic + 10 g PA) was better than in the control (2.45 ± 0.1%) (P < 0.05). Feed conversion ratio in fish fed with 10 g PA/kg (0.92 ± 0.12) and diets contained blends of probiotic and PA (0.94 ± 0.06 in probiotic + 5 g PA and 0.91 ± 0.02 in probiotic + 10 g PA) was better than in the control (1.24 ± 0.08) (P < 0.05). Digestive enzymes including α-amylase, total alkaline proteases, and bile salt dependent lipase activities improved in fish fed diets contained additives. The activity of glutathione-S-transferase and glutathione reductase enhanced in the liver of fish fed diets contained additives. The relative abundance of lysozyme, interleukin 1β, and insulin-like growth factor-1 genes mRNA transcript showed multifold increase in the liver of fish fed with the 10 g PA/kg and diets contained blends of probiotic and PA (P < 0.05). By considering the above mentioned results, supplementing a PP-rich diet with 10 g PA/kg diet or combination of PA and a mixture of Bacillus spp. probiotic recommended for L. calcarifer.

Short chain fatty acids (SCFAs) improves TNBS-induced colitis in zebrafish

The short-chain fatty acids (SCFAs) are metabolites originated from the fermentation of dietary fibers and amino acids produced by the bacteria of the intestinal microbiota. The most abundant SCFAs, acetate, propionate, and butyrate, have been proposed as a treatment for inflammatory bowel diseases (IBDs) due to their anti-inflammatory properties. This work aimed to analyze the effects of the treatment of three combined SCFAs in TNBS-induced intestinal inflammation in zebrafish larvae. Here, we demonstrated that SCFAs significantly increased the survival of TNBS-exposed larvae, preserved the intestinal endocytic function, reduced the expression of inflammatory cytokines and the intestinal recruitment of neutrophils caused by TNBS. However, SCFAs treatment did not appear to avoid TNBS-induced tissue damage in the intestinal wall and did not restore the number of mucus-producing goblet cells. Finally, exposure to TNBS induced dysbiosis of the microbiota with an increase in Betaproteobacteria and Actinobacteria, while the treatment with SCFAs maintained these population levels similar to control. Thus, we demonstrate that the treatment of three combined SCFAs presented anti-inflammatory properties previously seen in mammals, opening an opportunity to use zebrafish to explore the potential benefit of these and other metabolites to treat inflammation.

Enrichment of common carp (Cyprinus carpio) diet with Malic acid: Effects on skin mucosal immunity, antioxidant defecne and growth performance

The present study investigated possible effects of dietary malic acid on the expression of immunity, antioxidant and growth related genes expression as well as skin mucus immune parameters in common carp. Common carp (Cyprinus carpio) fingerlings were fed diets supplemented with different levels (0 [control], 0.5%, 1%, 2%) of malic acid (MA) for 60 days. The results revealed highest expression levels of immune-related genes (tnf-alpha, il1b, il8 and lyz) in skin of common carp fed 2% MA (P < 0.05). Regarding 1% MA treatment comparison with control group, significant difference was noticed just in case of lyz (P < 0.05). Evaluation of growth related genes expression revealed no significant difference between treatments (P > 0.05). The study of antioxidant related genes (gsta and gpx) in common carp skin fed with MA, showed significant difference between treated groups and control (P < 0.05). Carps fed with 2% MA had highest alkaline phosphatase activity in skin mucus compared other treated groups and control (P < 0.05). There were no significant difference between 0.5% and 1% and control (P > 0.05). The study of total protein and total immunoglobulin (Ig) in common carp skin musus revealed no alteration following MA treatment (P > 0.05). The present data demonstrated that feeding with MA altered immune and antioxidant genes expression in skin mucus of common carp.

Effect of Dietary Sodium Acetate on Skin Mucus Immune Parameters and Expression of Gene Related to Growth, Immunity and Antioxidant System in Common Carp (Cyprinus carpio) Intestine

The present study investigated the possible effects of including salt of short chain fatty acid, sodium acetate (SA), on skin mucus immune parameters and immune, antioxidant and growth-related genes expression in common carp. There is little data available about the effective role of SA on immune, antioxidant and growth related genes expression as well as skin mucus immune parameters. The aim of this study was to analyse the effect of SA intake on these factors using common carp (Cyprinus carpio) as model organism. Two hundred and forty healthy common carps (mean weight = 15 ± 0.9 g) were supplied and randomly stocked into 12 fiberglass tanks 200 L (20 fish per tank) assigned to four treatments and triplicates. The study was performed in a completely randomized design. The treatments were feeding carps with experimental diets containing different levels (0.0 [control], 0.5, 1 and 2%) of SA. The skin mucus total immunoglobulin and total protein levels in fish fed 2% SA showed significant increase compared to the control group (P<0.05). Results showed a significant increase in the GH gene expression in 1 and 2% SA treatments (P<0.05). The carps fed the diet with 2% SA showed a significant increase in IGF-1 expression (P<0.05). The expression of GSTa, and GPX (antioxidant genes) revealed a significant increase in the GSTa (fish fed SA at 1% and 2% levels) and GPX gene expression with fish fed 2% SA (P<0.05). Supplementation of fish diet with SA induced a slight elevation in the intestine of all immune-related genes (TNF-α, IL-1β, IL8 and Lyz) compared to the control group (P>0.05). However, Lyz gene was significantly up-regulated in 1 or 2% SA treatments. These results confirmed beneficial effects of SA as a feed additive in common carp culture.

Stimulation of Gastric Transit Function Driven by Hydrolyzed Casein Increases Small Intestinal Carbohydrate Availability and Its Microbial Metabolism

Gastrointestinal (GI) functions affect gut nutrient flow and microbial metabolism. Dietary peptides modulate GI functions and improve small intestinal health, but the mechanism remains elusive. This study aims to investigate whether dietary peptides affect small intestinal microbial metabolism, and the underlying mechanisms. An ileal-cannulated pig model is adopted to explore the relationship between gut nutrient flow and microbial metabolism after treatment with hydrolyzed casein (peptides) or intact casein (Control)-based diet. The results demonstrate that hydrolyzed casein enhances microbial carbohydrate metabolism with higher Streptococcus abundance and higher lactate level in the ileum. Meanwhile, hydrolyzed casein increases ileal flows of nutrients, especially carbohydrate, leading to a higher carbohydrate availability in ileal digesta. To unveil the mechanisms, it is found that the hydrolyzed casein enhances the ghrelin signal and improves development of interstitial cells of Cajal and muscular layer in gastric corpus, indicating the enhanced upper GI transit function. In addition, hydrolyzed casein improves small intestinal health, as indicated by higher villus heights and luminal lactate concentrations in the jejunum and ileum. In conclusion, hydrolyzed casein stimulates upper GI transit function, enhances gut nutrient flow, and increases small intestinal carbohydrate availability and its microbial metabolism, which favor the small intestinal health.

Effect of dietary sodium acetate on skin mucus immune parameters and expression of gene related to growth, immunity and antioxidant system in common carp (Cyprinus carpio) intestine

The present study investigated the possible effects of including salt of short chain fatty acid, sodium acetate (SA), on skin mucus immune parameters and immune, antioxidant and growth-related genes expression in common carp. There is a little data available about the effective role of SA on immune, antioxidant and growth related genes expression as well as skin mucus immune parameters. The aim of this study was to analysis the effect of SA intake on these factors using common carp (Cyprinus carpio) as model organism. Two hundred and forty healthy common carp (mean weight = 15 ± 0.9 g) supplied and randomly stocked into 12 fiberglass tanks 200 L (20 fish per tank) assigned to four treatments and triplicates. The study was performed in a completely randomized design. The treatments were feeding carps with experimental diets containing different levels (0.0 [control], 0.5, 1 and 2%) of SA. The skin mucus total immunoglobulin and total protein levels in fish fed 2% SA showed significant increase compared to the control group (P < 0.05). Results showed a significant increase in the GH gene expression in 1 and 2% SA treatments (P < 0.05). The carps were fed with diet content 2% SA showed significantly increase in IGF-1 expression (P < 0.05). The expression of GSTa, and GPX (antioxidant genes) revealed a significant increase in the GSTa (fish fed SA at 1% and 2% levels) and GPX gene expression with fish fed 2% SA (P < 0.05). Supplementation of fish diet with SA induce slight elevation in the intestine of all immune-related genes (TNF-α, IL-1β, IL8 and Lyz) compared to the control group (P > 0.05). However, Lyz gene significantly up-regulated in 1 or 2% SA treatments. These results confirmed beneficial effects of SA as a feed additive in common carp culture.

Sodium acetate alleviated high-carbohydrate induced intestinal inflammation by suppressing MAPK and NF-κB signaling pathways in Nile tilapia (Oreochromis niloticus)

With the development of aquaculture industry, high-carbohydrate diet is used to stimulate protein-sparing effect and reduce feed cost. However, fish utilize carbohydrates poorly in general, and instead, high level of carbohydrates in the diet influence the growth condition of fish. How to alleviate the side effects of high carbohydrate diet on fish health has attracted more and more attentions. In the present study, Nile tilapia (Oreochromis niloticus) were fed with 25% and 45% of carbohydrate diet for eight weeks. Higher body weight but lower resistance to pathogen was found in 45% carbohydrate diet group. Higher expression level of inflammation cytokines, increased expression of total NF-κB protein and phosphorylated NF-κB protein (p-NF-κB) were detected in higher carbohydrate group. Concentration of short-chain fatty acids (SCFAs) was measured and the results indicated that high-carbohydrate diet decreased acetate content in the intestine. In order to detect the relationship between the decreased concentration of acetate and lower resistance to pathogen in high-carbohydrate group, 45% of carbohydrate diets (HC) supplemented with different concentrations of sodium acetate (HC + LA, 100 mmol/L; HC + MA, 200 mmol/L; HC + HA, 400 mmol/L) were used to raise Nile Tilapia for eight weeks. The results indicated that addition of 200 mmol/L sodium acetate (HC + MA) reduced the mortality when fish were challenged with Aeromonas hydrophila. Furthermore, we also found that addition of 200 mmol/L sodium acetate mainly inhibited p38 mitogen-activated protein kinase (p38MAPK) and NF-κB phosphorylation to decrease the expression level of inflammation cytokines (IL-8, IL-12, TNF-α and IL-1β) in the intestine. The present study indicated that certain concentration of sodium acetate could alleviate high-carbohydrate induced intestinal inflammation mainly by suppressing MAPK activation and NF-κB phosphorylation.

Dietary Approaches to Attain Fish Health with Special Reference to their Immune System

Fish despite their low collocation in the vertebrate phylum possess a complete immune system. In teleost fish both innate and adaptive immune responses have been described with melanomacrophage centers (MMCs) equivalent to mammalian germinal centers. Primary lymphoid organs are represented by the thymus and kidney, while spleen and mucosa-associated lymphoid tissues act as secondary lymphoid organs. Functions of either innate immune cells (e.g., macrophages and dendritic cells) or adaptive immune cells (T and B lymphocytes) will be described in detail, even including their products, such as cytokines and antibodies. In spite of a robust immune arsenal, fish are very much exposed to infectious agents (marine bacteria, parasites, fungi, and viruses) and, consequentially, mortality is very much enhanced especially in farmed fish. In fact, in aquaculture stressful events (overcrowding), microbial infections very frequently lead to a high rate of mortality. With the aim to reduce mortality of farmed fish through the reinforcement of their immune status the current trend is to administer natural products together with the conventional feed. Then, in the second part of the present review emphasis will be placed on a series of products, such as prebiotics, probiotics and synbiotics, β-glucans, vitamins, fatty acids and polyphenols all used to feed farmed fish. With special reference to polyphenols, results of our group using red grape extracts to feed farmed European sea bass will be illustrated. In particular, determination of cytokine production at intestinal and splenic levels, areas of MMCs and development of hepatopancreas will represent the main biomarkers considered. All together, our own data and those of current literature suggests that natural product administration to farmed fish for their beneficial effects may, in part, solve the problem of fish mortality in aquaculture, enhancing their immune responses.

Dietary nucleotides can directly stimulate the immunity of zebrafish independent of the intestinal microbiota

In this study, we firstly tested the effects of dietary nucleotides on the disease resistance and innate immunity of zebrafish. Further, we investigated the role of intestinal microbiota in the nucleotides-induced immunostimulatory effect by using a germ-free zebrafish model and microbiota transfer technique. Fish were fed control or nucleotides (NT)-supplemented diets (at 0.05%,0.1%, 0.15% or 0.2%, m/m) for 4 weeks, followed by immersion challenge with Aeromonas hydrophila NJ-1. The results showed that 0.1% NT group enhanced the resistance of zebrafish against A. hydrophila infection. We further observed that the relative expressions of mucin, claudin16, occlusin1, hepcidin, defensin beta-like, myeloperoxidase (Mpo), and serum amyloid A (Saa) increased in the 0.1% NT group compared with control (P < 0.05), indicating that dietary nucleotides enhanced the physical barrier and mucosal immunity in the intestine of zebrafish. Moreover, ROS level in the head kidney was significantly increased in NT fed zebrafish versus control (P < 0.05), indicating enhanced systematic immunity. Furthermore, dietary NT significantly elevated the relative expressions of mpo, saa and the ROS activity in germ-free zebrafish, while germ-free zebrafish colonized with NT-altered microbiota had no significant difference in the relative expressions of mpo, saa and the ROS activity compared with the control microbiota-colonized fish, suggesting that the immunostimulatory effect of dietary NT is mediated by direct action of NT and does not involve the microbiota. Consistently, dietary NT can protect germ-free zebrafish from pathogenic infection, whereas germ-free zebrafish colonized with NT microbiota showed no difference in disease resistance compared with control microbiota colonized counterparts. Together, these results indicated that the immunostimulatory and disease protection effect of dietary nucleotides in zebrafish was mediated by direct action of the nucleotides, and does not involve the intestinal microbiota.

Mucosal immune parameters, immune and antioxidant defence related genes expression and growth performance of zebrafish (Danio rerio) fed on Gracilaria gracilis powder

In the present study zebrafish (Danio rerio) has been used as model organism to establish the effects of dietary supplementation of Gracilaria gracilis powder (GP) on mucosal and innate immune parameters, antioxidant enzymes, and growth. In order to establish these features, zebrafish were fed for eight weeks with experimental diets containing different levels of Red algae, 0.25, 0.5 and 1% of GP; also, a group was fed with control diet. At the end of the experimental period the antioxidant superoxide dismutase and catalase (SOD, CAT) genes expression, interleukin 1 beta (il-1β), 
lysozyme (LYZ), tumor necrosis factor alpha (TNF-α) for immune-related genes expression, total immunoglobulin (Ig), total protein, 
alkaline phosphatase (ALP) activity for innate immune parameters, and growth performance have been established. The GP dietary supplementation showed differences in SOD and CAT expression in zebrafish whole body respect to the control group. Non-signifcant differences were noticed among the different groups in case of TNF-α, LYZ and il-1expression (P > 0.05). The skin mucus total Ig and total protein in the group fed on 1% of GP were significantly higher respect to control group (P < 0.05). 0.25 and 0.5% of GP dietary supplementation significantly enhanced skin mucus ALP activity levels (P < 0.05). No significant differences were recorded for growth performances among groups (P > 0.05). The results obtained in the present study revealed that G. gracilis could be takes in account as fishes diet supplementation for its immune system stimulants effects.

Lactic Acid Bacteria in Finfish-An Update

A complex and dynamic community of microorganisms, play important roles within the fish gastrointestinal (GI) tract. Of the bacteria colonizing the GI tract, are lactic acid bacteria (LAB) generally considered as favorable microorganism due to their abilities to stimulating host GI development, digestive function, mucosal tolerance, stimulating immune response, and improved disease resistance. In early finfish studies, were culture-dependent methods used to enumerate bacterial population levels within the GI tract. However, due to limitations by using culture methods, culture-independent techniques have been used during the last decade. These investigations have revealed the presence of Lactobacillus, Lactococcus, Leuconostoc, Enterococcus, Streptococcus, Carnobacterium, Weissella, and Pediococcus as indigenous species. Numerous strains of LAB isolated from finfish are able to produce antibacterial substances toward different potential fish pathogenic bacteria as well as human pathogens. LAB are revealed be the most promising bacterial genera as probiotic in aquaculture. During the decade numerous investigations are performed on evaluation of probiotic properties of different genus and species of LAB. Except limited contradictory reports, most of administered strains displayed beneficial effects on both, growth-and reproductive performance, immune responses and disease resistance of finfish. This eventually led to industrial scale up and introduction LAB-based commercial probiotics. Pathogenic LAB belonging to the genera Streptococcus, Enterococcus, Lactobacillus, Carnobacterium, and Lactococcus have been detected from ascites, kidney, liver, heart, and spleen of several finfish species. These pathogenic bacteria will be addressed in present review which includes their impacts on finfish aquaculture, possible routes for treatment. Finfish share many common structures and functions of the immune system with warm-blooded animals, although apparent differences exist. This similarity in the immune system may result in many shared LAB effects between finfish and land animals. LAB-fed fish show an increase in innate immune activities leading to disease resistances: neutrophil activity, lysozyme secretion, phagocytosis, and production of pro-inflammatory cytokines (IL-1β, IL-6, IL-8, and TNF-α). However, some LAB strains preferentially induces IL-10 instead, a potent anti-inflammatory cytokine. These results indicate that LAB may vary in their immunological effects depending on the species and hosts. So far, the immunological studies using LAB have been focused on their effects on innate immunity. However, these studies need to be further extended by investigating their involvement in the modulation of adaptive immunity. The present review paper focuses on recent findings in the field of isolation and detection of LAB, their administration as probiotic in aquaculture and their interaction with fish immune responses. Furthermore, the mode of action of probiotics on finfish are discussed.

Effects of dietary inclusion of Moringa oleifera leaves on growth and some systemic and mucosal immune parameters of seabream

The effect of the dietary incorporation of drumstick, Moringa oleifera, leaf meal (MOL; 0, 5, 10 and 15%) on the growth, feed utilization, some skin mucus and systemic immune parameters and intestinal immune-related gene expression in gilthead seabream (Sparus aurata) specimens. The experiment lasted 4 weeks. The results revealed that MOL can be incorporated in S. aurata diet up to 10% with no significant negative effect on growth and feed utilization. However, there was a significant decrease with MOL at a level of 15% after 2 weeks of feeding. The systemic immune status of fish fed with the different levels of MOL showed an improvement in head kidney leucocyte phagocytosis, respiratory burst and peroxidase activities. Also, serum humoral components, including protease, ACH₅₀ and lysozyme activities and IgM level, increased with MOL inclusion especially at the 5% level. MOL at 5% improved skin-mucosal immunity such as protease, antiprotease, peroxidase and lysozyme activities. Moreover, the feeding of MOL revealed an upregulation of the intestinal mucosal immunity genes (lyso and c3), tight junction proteins (occludin and zo-1) and anti-inflammatory cytokines (tgf-β) with a downregulation of pro-inflammatory cytokine (tnf-α). Therefore, it is recommended to incorporate MOL in S. aurata diets at a level of 5% for the best immune status or 10% for the high growth performance and acceptable immune surveillance. Graphical abstract ᅟ.

Soya-saponins induce intestinal inflammation and barrier dysfunction in juvenile turbot (Scophthalmus maximus)

Soybean meal-induced enteritis (SBMIE) is a well-described condition in the distal intestine (DI) of several cultured fish species, but the exact cause is still unclear. The work on Atlantic salmon and zebrafish suggested soya-saponins, as heat-stable anti-nutritional factors in soybean meal, are the major causal agents. However, this conclusion was not supported by the research on some other fish, such as gilthead sea bream and European sea bass. Our previous work proved that soybean could induce SBMIE on turbot and the present work aimed to investigate whether soya-saponins alone could cause SBMIE and the effects of soya-saponins on the intestinal barrier function in juvenile turbot. Turbots with initial weight 11.4 ± 0.02 g were fed one of four fishmeal-based diets containing graded levels of soya-saponins (0, 2.5, 7.5, 15 g kg-1) for 8 weeks. At the end of the trial, all fish were weighed and plasma was obtained for diamine oxidase (DAO) activity and d-lactate level analysis and DI was sampled for histological evaluation and quantification of antioxidant parameters and inflammatory marker genes. The activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and intestinal glutathione level were selected to evaluated intestinal antioxidant system. The distal intestinal epithelial cell (IEC) proliferation and apoptosis were investigated by proliferating cell nuclear antigen (PCNA) labelling and TdT-mediated dUTP nick end labeling (TUNEL), respectively. The results showed that soya-saponins caused significantly dose-dependent decrease in the growth performance and nutrient utilization (p < 0.05). Enteritis developed in DI of the fish fed diet containing soya-saponins. Significantly dose-dependent increases in severity of the inflammation concomitant with up-regulated expression of il-1β, il-8, and tnf-α, increased IEC proliferation and apoptosis, and decreases in selected antioxidant parameters were detected (p < 0.05). The epithelial permeability (evaluated by the plasma DAO activity and d-lactate level) was significantly increased with the increasing of dietary level of soya-saponins (p < 0.05), which was concomitant with the destroyed the intracellular junctions. In conclusion, the present work proved that soya-saponins induced enteritis and compromised the intestinal barrier functions. Based on the present work, strategies focus on regulation of cell apoptosis, epithelial permeability, intracellular junctions and redox homeostasis worth further investigating to develop new and efficient ways for SBMIE alleviation.

The ambivalent effect of Fe3O4 nanoparticles on the urea-induced unfolding and dilution-based refolding of lysozyme

Due to the numerous biological applications of magnetite (Fe₃O₄) nanoparticles (MNPs), it is essential to identify the influence of these nanoparticles on basic biological processes. Therefore, in this research, the effect of MNPs on the structure and activity of hen egg white lysozyme (HEWL) (EC 3.2.1.1) as a model protein was examined using tryptophan intrinsic fluorescence, UV/Vis, and circular dichroism spectroscopy. Moreover, enzyme activities were analyzed by a turbidometric approach in the presence of MNPs at concentrations providing MNPs/HEWL ratios in the range of 0.04-1.25. As-synthesized MNPS were characterized by Fourier transform infrared spectroscopy, x-ray diffraction, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry and the zeta potential of MNPs was measured to be -29 mV. The goal of this work was investigating the ordering or disordering effect of MNPs on protein structure at ratios lower or higher than 0.918 as concentration ratio of threshold (CRT), respectively, in order to answer the question: 'How can the denaturation and refolding of a model protein (HEWL) be affected by MNPs?' As has been reported recently, the protein folding, helicity, and half-life were improved at <CRT to make the protein more ordered and conversely, HEWL was unfolded, and the helicity and half-life were decreased at >CRT to make the protein more disordered upon interaction with MNPs. The disordering effect of urea at >CRT and even at <CRT in the denaturation buffer (urea 6 M) increased and at <CRT the MNPs can provide a significant improvement in the refolding of the unfolded urea treated protein. These observations provide a new perspective on the growing applications of MNPs in biotechnology and biomedicine.

The functionality of prebiotics as immunostimulant: Evidences from trials on terrestrial and aquatic animals

The gut immune system is, the main option for maintaining host's health, affected by numerous factors comprising dietary constituents and commensal bacteria. These dietary components that affect the intestinal immunity and considered as an alternative of antibiotics are called immunosaccharides. Fructooligosaccharide (FOS), Galactooligosaccharide (GOS), inulin, dietary carbohydrates, and xylooligosaccharide (XOS) are among the most studied prebiotics in human as well as in aquaculture. Although prebiotics and probiotics have revealed potential as treatment for numerous illnesses in both human and fish, a comprehensive understanding of the molecular mechanism behind direct and indirect effect on the intestinal immune response will help more and perhaps extra effective therapy intended for ailments. This review covers the most newly deep-rooted scientific outcomes about the direct and indirect mechanism through which these dietetic strategies can affect intestinal immunity of terrestrial and aquatic animals. Prebiotics exert an influence on gut immune system via the increase in lysozyme and phagocytic activity, macrophage activation and stimulation of monocyte-derived dendritic cells. Furthermore, these functional molecules also enhance epithelial barrier function, beneficial gut microbial population, and production of intermediate metabolites for example short chain fatty acids (SCFAs) that assist in balancing the immune system. Moreover, emphasis will be sited on the relationship among food/feed, the microbiota, and the gut immune system. In conclusion, further studies are nonetheless essential to confirm the direct effect of prebiotics on immune response.

Prebiotic effects of resistant starch from purple yam (Dioscorea alata L.) on the tolerance and proliferation ability of Bifidobacterium adolescentis in vitro

The in vitro prebiotic effects of resistant starch (RS), prepared by different treatments from purple yam, on Bifidobacterium adolescentis (bifidobacteria for short), were investigated. Tolerance tests indicated that bifidobacteria in PDS (prepared by debranching combined with autoclaving) and PDS.H (PDS further treated by double enzyme hydrolysis) media adapted better to simulated upper gastrointestinal conditions (at pH 1.5-3.0 and 0.3% and 1.0% bile acid) than those in GLU (glucose) and DAS (prepared by autoclaving) media. PDS.H, which had the highest digestion resistibility, exhibited significant effects on the OD600 nm value (1.544) and the pH value (4.21) when the carbohydrate concentration was 20 g L-1. Additionally, the exponential growth phase of bifidobacteria was 2 h in the PDS or PDS.H media, whereas it was 4 h in the GLU or DAS media. A higher content of short-chain fatty acids (SCFAs) was obtained in the PDS.H medium. Analysis of the structural features of RS and fermented RS indicated that PDS, especially PDS.H, had a rougher surface and higher crystallinity than DAS. Fermented RS in a simulated large bowel environment showed an eroded surface and decreased crystallinity. All of these findings suggest that RS with a rough surface and perfect crystalline structure could protect bifidobacteria from gastrointestinal conditions and enhance the proliferation of bifidobacteria.

The effects of dietary supplement of galactooligosaccharide on innate immunity, immune related genes expression and growth performance in zebrafish (Danio rerio)

The present study investigates the effect of different levels of galactooligosaccharide (GOS) on innate immune parameters, immune related genes expression as well as growth performance in zebrafish (Danio rerio). Four hundred and twenty fish (mean weight 45 ± 0.1 mg) were supplied, randomly stocked in twelve aquaria assigned to four treatments. Zebrafish were fed with either control diet or control diet enriched with different levels (0.5, 1 and 2%) of GOS for eight weeks. At the end of feeding trial innate immune parameters (total immunoglobulin, total protein and alkaline phosphatase activity), immune related genes expression (interleukin 1 beta [il1b], Lysozyme [lyz], tumor necrosis factor alpha [tnf-alpha]) as well as growth performance were measured. Evaluation of immune parameters revealed significant (P < .05) increase of total protein and total Ig in zebrafish fed 1 or 2% GOS compared other treatments. However, in case of lysozyme activity no significant (P > .05) differences were noticed between GOS fed fish and control group. Also, in case of ALP activity, significant increase (P < .05) was observed in 2% GOS treatment. Gene expression studies revealed significant upregulation (P < .05) of tnf-alpha and lyz genes in GOS fed fish. While no significant (P > .05) difference was observed in case of il1b gene expression. Evaluation of growth performance at the end of feeding trial revealed no significant (P < .05) improvement in GOS fed groups. The present results revealed positive effects of GOS on innate immune parameters and related gene expression in zebrafish.

Transcriptome analysis reveals carbohydrate-mediated liver immune responses in Epinephelus akaara

As the cheapest energy source, carbohydrates are used in fish feeds to improve physical quality and reduce catabolism of proteins and lipids. The liver is the primary organ for metabolism and is also an important site of immune regulation. Here, we investigated the effect of different dietary carbohydrate levels on growth and health by evaluating the liver transcriptome of Epinephelus akaara. In this study, E. akaara juveniles were fed diets containing few (0% corn starch), moderate (18% corn starch), and high (30% corn starch) levels of dietary carbohydrate. After an 8-week feeding trial, E. akaara fed 30% dietary carbohydrates exhibited poor growth performance compared with those fed 0% and 18% dietary carbohydrates (P > 0.05). Genes related to the immune system, including IL8, TLR9, CXCR4, CCL4, and NFκB inhibitor alpha, were over-expressed in E. akaara fed the highest level of carbohydrate (30%). This general over-expression could indicate activation of inflammatory processes in the liver. The liver transcriptome data of E. akaara reported here indicate that high carbohydrate level of diet can lead to poor growth and inflammatory immune response in E. akaara.

Pathogen invasion changes the intestinal microbiota composition and induces innate immune responses in the zebrafish intestine

Numerous bacteria are harbored in the animal digestive tract and are impacted by several factors. Intestinal microbiota homeostasis is critical for maintaining the health of an organism. However, how pathogen invasion affects the microbiota composition has not been fully clarified. The mechanisms for preventing invasion by pathogenic microorganisms are yet to be elucidated. Zebrafish is a useful model for developmental biology, and studies in this organism have gradually become focused on intestinal immunity. In this study, we analyzed the microbiota of normal cultivated and infected zebrafish intestines, the aquarium water and feed samples. We found that the predominant bacteria in the zebrafish intestine belonged to Gammaproteobacteria (67%) and that feed and environment merely influenced intestinal microbiota composition only partially. Intestinal microbiota changed after a pathogenic bacterial challenge. At the genus level, the abundance of some pathogenic intestinal bacteria increased, and these genera included Halomonas (50%), Pelagibacterium (3.6%), Aeromonas (2.6%), Nesterenkonia (1%), Chryseobacterium (3.4‰), Mesorhizobium (1.4‰), Vibrio (1‰), Mycoplasma (0.7‰) and Methylobacterium (0.6‰) in IAh group. However, the abundance of some beneficial intestinal bacteria decreased, and these genera included Nitratireductor (0.8‰), Enterococcus (0.8‰), Brevundimonas (0.7‰), Lactococcus (0.7‰) and Lactobacillus (0.4‰). Additionally, we investigated the innate immune responses after infection. ROS levels in intestine increased in the early stages after a challenge and recovered subsequently. The mRNA levels of antimicrobial peptide genes lectin, hepcidin and defensin1, were upregulated in the intestine after pathogen infection. These results suggested that the invasion of pathogen could change the intestinal microbiota composition and induce intestinal innate immune responses in zebrafish.

The effects of single or combined administration of galactooligosaccharide and Pediococcus acidilactici on cutaneous mucus immune parameters, humoral immune responses and immune related genes expression in common carp (Cyprinus carpio) fingerlings

The present study was performed to investigate the effects of single or combined administration of galactooligosaccharide (GOS) and Pediococcus acidilactici on cutaneous mucus immune parameters, humoral immune responses and immune related genes expression in common carp (Cyprinus carpio) fingerlings. Carps were fed experimental diets for 8 weeks as follows: non-supplemented (Control), prebiotic diet (10 g/kg GOS), probiotic diet (1 g/kg [0.9 × 10⁷ CFU] lyophilized P. acidilactici) and synbiotic diet (10 GOS in combination with 1 g/kg [0.9 × 10⁷ CFU] lyophilized P. acidilactici). Unlike skin mucus, the serum lysozyme activity showed no significant difference between carps fed supplemented or control diets, however, remarkable elevation of serum ACH50 activity was noticed in carps fed supplemented diet (pro-, pre- and synbiotic diets) compared control group. Besides, feeding on pro-, pre- and synbiotic supplemented diets significantly increased serum and skin mucus total Ig levels. However, no significant difference was observed between treatments and control group in case of skin mucus proteases activity. There was no significant difference between expression levels of intestinal genes of LYZ and IL1b in fish fed on pre- and synbiotic, compared to the control. However, evaluation of TNF-alpha gene expression in the intestine of carps revealed remarkable down-regulation in treated groups (p < 0.05). These results indicated positive effect of supplementation of carp diet with GOS and P. acidilactici on some mucosal or serum immune parameters.

Effect of Dietary Fish Oil Replacement with Plant Oils on Growth Performance and Gene Expression in Juvenile Rainbow Trout (Oncorhynchus mykiss)

An eight-week feeding trial was conducted to evaluate the effects of total (100%) replacement of dietary fish oil with alternative lipid sources in juvenile rainbow trout. Six iso-nitrogenous and iso-lipidic experimental diets were formulated: CO (14%) – cod liver oil; SSO (14%) – safflower seed oil; SBO (14%) – soybean oil; LO (14%) – linseed oil; SBO (7%) + LO (7%) – a blend of soybean oil and linseed oil; and SSO (7%) + LO (7%) – a blend of safflower seed oil and linseed oil. Growth performance [specific growth rate (SGR), weight gain (WG), food conversion ratio (FCR) and survival rate (SR)], growth hormones [growth hormone (GH-I), insulin-like growth factor-I (IGF-I) and insulin-like growth factor-II (IGF-II)], immune transforming growth factor-β (TGF-β) and antioxidant [superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), catalase (CAT) and glutathione S-transferase (GST)] response, and heat shock protein 70 (HSP70) mRNA levels were determined in muscle and liver. Our data indicated that final weight, weight gain, FCR and SGR showed significant difference among the six dietary treatments (P<0.05) while there were no significant differences in survival rate between the rainbow trout from supplement fed groups and control group. HSP70 mRNA level expression in muscle was higher in fish fed SSO (P<0.05) while highest level in liver was obtained from fish fed SBO compared to the other treatments (P<0.05). There were no significant differences among treatments for TGF-β mRNA expression level in muscle and liver. In conclusion, growth performance and expression levels of growth hormones, antioxidants, HSP70, except TGF-β were affected by five separate lipid sources. In addition, LO positively increased growth performance of juvenile rainbow trout by means of preventing oxidative stress and HSP70 and, enhanced expression of growth hormone related gene.

Comparing the effects of different dietary organic acids on the growth, intestinal short-chain fatty acids, and liver histopathology of red hybrid tilapia (Oreochromis sp.) and potential use of these as preservatives

Dietary organic acids are increasingly being investigated as a potential means of improving growth and nutrient utilization in aquatic animals. A 9-week study was performed to compare equal amounts (2%) of different organic acids (sodium butyrate, acetate, propionate, or formate) on the growth, muscle proximate composition, fatty acid composition, cholesterol and lipid peroxidation, differential cell counts, plasma biochemistry, intestinal short-chain fatty acid (SCFA) level, and liver histopathology to red hybrid tilapia (Oreochromis sp.) (initial mean weight of 2.87 g). A second experiment was performed to determine their effects on lipid peroxidation and trimethylamine (TMA) when added at 1% to tilapia meat and left out for 24 h. The results of the first experiment showed no treatment effect to growth, feeding efficiencies, or muscle fatty acid composition, but all dietary organic acids significantly decreased intestinal SCFA. Dietary butyrate and propionate significantly decreased muscle lipid peroxidation compared to the control group, but the dietary formate treatment had the lowest lipid peroxidation compared to all treatments. Muscle crude protein and lipid in tilapia fed the formate diet were significantly lower and higher, respectively, and showed evidence of stress based on the differential cell counts, significantly higher plasma glucose and liver glycogen, as well as inflammatory responses in the liver. Although a potential benefit of dietary organic acids was a reduction to lipid peroxidation, this could be accomplished post-harvest by direct additions to the meat. In addition, inclusions of butyrate and propionate to tilapia meat significantly decreased TMA, which might be a more cost-effective option to improve the shelf life of tilapia products.

The effects of dietary Myrtle (Myrtus communis) on skin mucus immune parameters and mRNA levels of growth, antioxidant and immune related genes in zebrafish (Danio rerio)

Myrtle (Myrtus communis L., Myrtaceae) is a significant plant which naturally distributed around the globe. Although numerous studies have demonstrated the benefits of myrtle in different species, studies using the oral route are rare in the literature. In the present study, we evaluated the effect of myrtle intake on the antioxidant, immune, appetite and growth related genes as well as mucosal immune responses in zebrafish (Danio rerio) model. Zebrafish were fed control or myrtle (5, 10 and 20 g kg^-1 myrtle) supplemented diets for sixty days. The results showed that, oral administration of Myrtle significantly improved mucosal immune responses (the activity of lysozyme, total Ig and protease). Furthermore, fish fed 20 g kg^-1 showed remarkably higher antioxidant (sod and cat) enzymes gene expression compared other treatment. There were significant difference between myrtle fed fish and control group regarding tnf-alpha and lyz expression. Also, evaluation of growth (gh and igf1) related genes revealed remarkable upregulation in 20 g kg^-1 myrtle treatment compared other myrtle treatments and control group. Similar results was observed regarding the mRNA levels of appetite related genes (ghrl) in zebrafish fed 20 g kg^-1 myrtle. The present results indicated that dietary administration of myrtle improved mucosal immune parameters and altered mRNA levels of selected genes. These results on zebrafish model also highlights the potential use of Myrtle supplements as additive in human diets.