Impact of date palm fruits extracts and probiotic enriched diet on antioxidant status, innate immune response and immune-related gene expression of European seabass (Dicentrarchus labrax)

Effects of different combinations of koumine and gelsemine on growth performance, intestinal health, and transcriptome of Cyprinus carpio

Koumine (KM) and gelsemine (GS) have shown significant benefits in livestock production, but their potential in aquaculture remains largely unexplored. This study examined the impact of different KM and GS combinations as feed additives on C. carpio (90 fish per group, initial weight 1.95 ± 0.08 g). KM and GS were introduced in ratios of 2:2 (mg/kg), 2:1 (mg/kg), and 2:0.67 (mg/kg) over a 10-week aquaculture experiment. The results demonstrate that the 2:1 (mg/kg) group increases the villus length, muscular layer thickness, crude protein, and crude fat content. Regarding fatty acid content, KM and GS enhance the levels of various fatty acids, including the total saturated fatty acid and total monounsaturated fatty acid. Additionally, KM and GS improve the composition and function of the intestinal microbiota. The 2:1 (mg/kg) group significantly elevates the enzymatic activities of SOD, MDA, CAT and upregulates the expression of immune-related genes such as toll-like receptor 2, transforming growth factor β, and glutathione S-transferase. Transcriptomic analysis suggests that KM and GS may have potential benefits for nutrient utilization and immune regulation in C. carpio. In summary, this study provides valuable insights into the use of KM and GS as feed additives in aquaculture.

Comparative proteomic analysis of the protein profile in the cuttlefish Sepia pharaonis associated with skin ulceration syndrome

Skin ulceration syndrome (SUS) is becoming a severe problem in the breeding and culturing process of the cuttlefish Sepia pharaonis. However, limited knowledge is available about the occurrence of this devastating disease. In this study, proteomic analysis was used to identify the differentially expressed proteins (DEPs) and the biological pathways enriched in SUS-diseased S. pharaonis. Both the healthy group and diseased group were analyzed in triplicate, with 4 cuttlefish in each replicate. The results showed that 85 DEPs were identified between the two groups, including 36 upregulated proteins and 49 downregulated proteins in the diseased group compared to the healthy group. GO enrichment analysis revealed that the DEPs were mainly enriched in cellular component organization or biogenesis, nucleus and ion binding processes. The results of the KEGG pathway analysis indicated that extracellular matrix (ECM)-receptor interaction was the most enriched upregulated pathway. Real-time reverse transcriptase PCR was used to identify the expression of two differentially expressed matrix metalloproteinases (MMPs), and the results showed that the mRNA expression of MMP14 and MMP19 was significantly upregulated in the skin tissue of the diseased group. Furthermore, the protease activity of the diseased group was higher than that of the healthy group. Our results offer basic knowledge on the changes in protein profiles during the occurrence of SUS in the cuttlefish S. pharaonis.

Synbiotic Agents and Their Active Components for Sustainable Aquaculture: Concepts, Action Mechanisms, and Applications

Aquaculture is a fast-emerging food-producing sector in which fishery production plays an imperative socio-economic role, providing ample resources and tremendous potential worldwide. However, aquatic animals are exposed to the deterioration of the ecological environment and infection outbreaks, which represent significant issues nowadays. One of the reasons for these threats is the excessive use of antibiotics and synthetic drugs that have harmful impacts on the aquatic atmosphere. It is not surprising that functional and nature-based feed ingredients such as probiotics, prebiotics, postbiotics, and synbiotics have been developed as natural alternatives to sustain a healthy microbial environment in aquaculture. These functional feed additives possess several beneficial characteristics, including gut microbiota modulation, immune response reinforcement, resistance to pathogenic organisms, improved growth performance, and enhanced feed utilization in aquatic animals. Nevertheless, their mechanisms in modulating the immune system and gut microbiota in aquatic animals are largely unclear. This review discusses basic and current research advancements to fill research gaps and promote effective and healthy aquaculture production.

Live Yeast (Saccharomyces cerevisiae var. boulardii) Supplementation in a European Sea Bass (Dicentrarchus labrax) Diet: Effects on the Growth and Immune Response Parameters

The present study has been aimed at evaluating the effects of the dietary inclusion of the live yeasts, Saccharomyces cerevisiae var. boulardii (LSB) administered at increasing concentrations (0, 100, and 300 mg kg-1 of feed, here referred to as LSB 0, 100, 300) for 90 days, on the health conditions of European sea bass. The main zootechnical parameters, histological and morphological analyses, innate immunity response parameters (intestinal cytokine expression, lysozyme content, spontaneous hemolytic and hemagglutinating activities, antibacterial activities, and peroxidase activity) were measured as fish welfare parameters. LSB did not impair either growth parameters or the morphometric indexes. LSB down-regulated interleukin-1β transcription in the distal gut of fish treated with 5.4 × 105 CFU g-1 (LSB100) for 21 days. The interleukin-6 mRNA level decreased significantly in the proximal gut for both doses of yeast, after 21 days of feeding; the gene expression of interleukin-6 was significantly lower in the sea bass fed 10.81 × 105 CFU g-1 (LSB300) probiotic. The levels of TNF-α mRNA were not influenced by probiotic supplementation. Increases, although not significant, in the hematological and immunological parameters were also recorded. The data collected in the present study suggests that an LSB-supplemented diet acts on the gut immune system of sea bass by modulating the expression of the key inflammatory genes.

Effects of Dietary Medlar (Mespilus germanica L.) Extract on Growth Performance, Innate Immune Characteristics, Antioxidant Status, and Responses to Crowding Stress in Rainbow Trout (Oncorhynchus mykiss)

High stocking density is a stress factor that potentially affects physiological and immune responses. In this study, the effects of medlar (Mespilus germanica) extract (ME) supplementation on growth performance, antioxidant, immune status, and stress responses in rainbow trout (Oncorhynchus mykiss) were studied. Six hundred fish (40.19 ± 1.09 g; average fish weight ± standard error) were distributed randomly into five experimental groups (assayed in triplicates). The experimental diets were formulated as follows: 0 (T1, control), 0.5% (T2), 1% (T3), 1.5% (T4), and 2% (T4). After 60 days feeding trial, the fish were confined, and the density increased (60 kg/m3) for further 14 days. Results showed significant increases in final weight (FW), weight gain (WG), specific growth rate, and feed intake in the T4 compared to the control (P < 0.05). The feed conversion ratio (FCR) in T4 significantly decreased compared to the control (P < 0.05). Also, the treated groups showed significant improvements in catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), lysozyme (LYZ), total immunoglobulin (total Ig), respiratory burst activity (RBA), total protein, and phagocytosis (PHA) (P < 0.05). Moreover, compared with the control group, supplementation could significantly decrease glucose (GLU) and cortisol (CORT), alanine transaminase (ALT), lactate dehydrogenase (LDH), aspartate transaminase (AST), and alkaline phosphatase (ALP) (P < 0.05). After the challenge, FW and WG in all treated challenge groups were significantly improved compared to the control group (P < 0.05). FCR showed a significant decrease in all treated challenged groups compared to the control group (P < 0.05). However, malondialdehyde, CAT, GPx, SOD, LYZ, complement activity (C3 and C4), total Ig, RBA, peroxidase, and PHA in challenged treated groups were significantly increased compared to the control group (P < 0.05). All treated challenged groups showed lower ALT, LDH, AST, ALP, GLU, and CORT levels than the control group (P < 0.05). The experiment herein successfully demonstrated that dietary ME stimulated fish growth, antioxidant status, and immune responses in crowding conditions and can be recommended as beneficial feed additives for rainbow trout.

Current Status of Probiotics in European Sea Bass Aquaculture as One Important Mediterranean and Atlantic Commercial Species: A Review

European sea bass production has increased in recent decades. This increase is associated with an annually rising demand for sea bass, which encourages the aquaculture industries to increase their production to meet that demand. However, this intensification has repercussions on the animals, causing stress that is usually accompanied by dysbiosis, low feed-conversion rates, and immunodepression, among other factors. Therefore, the appearance of pathogenic diseases is common in these industries after immunodepression. Seeking to enhance animal welfare, researchers have focused on alternative approaches such as probiotic application. The use of probiotics in European sea bass production is presented as an ecological, safe, and viable alternative in addition to enhancing different host parameters such as growth performance, feed utilization, immunity, disease resistance, and fish survival against different pathogens through inclusion in fish diets through vectors and/or in water columns. Accordingly, the aim of this review is to present recent research findings on the application of probiotics in European sea bass aquaculture and their effect on growth performance, microbial diversity, enzyme production, immunity, disease resistance, and survival in order to help future research.

Effects of dietary Euphorbia heterophylla extract on the growth performance, physiological, antioxidative and immune responses of Clarias gariepinus juveniles

Effects of dietary Euphorbia heterophylla extract (EH) on growth performance, feed utilization and haemato-biochemical parameters in African catfish, Clarias gariepinus, juveniles were evaluated in this study. Diets fortified with EH at 0 (control), 0.5, 1.0, 1.5 or 2.0 g/kg were fed to the fish to apparent satiation for 84 days before challenging it with Aeromonas hydrophila. The weight gain, specific growth rate and protein efficiency ratio of fish fed EH-supplemented diets were significantly higher but lower feed conversion ratio (p < 0.05) than the control group. The villi height and width at the proximal, mid and the distal of the guts rose significantly with the increasing levels of EH from 0.5 to 1.5 g than the fish fed basal diet. Dietary EH enhanced (p < 0.05) the packed cell volume and haemoglobin, whereas 1.5 g EH boosted white blood cell, in relation to their counterpart in the control group. There were significant increase in the activities of glutathione-S-transferase, glutathione peroxidase and superoxide dismutase (p < 0.05) in the fish that were fed diets supplemented with EH than the control. Dietary EH also enhanced phagocytic activities, lysozyme activities and relative survival (RS) of C. gariepinus than the control group, with the highest RS obtained in fish that were fed diet containing EH at 1.5 g/kg level. These results revealed that the fish fed 1.5 g/kg dietary EH promoted growth performance, antioxidant and immune profiles, as well as protection against A. hydrophila infection.

Effect of dietary celery (Apium graveolens) on the growth performance, immune responses, and bacterial resistance against Vibrio anguillarum of European seabass (Dicentrarchus labrax)

In this study, we evaluated to reveal the effects of aqueous methanolic extract of celery (Apium graveolens) on the growth performance, immune responses, and resistance against Vibrio anguillarum in European seabass (Dicentrarchus labrax). For this purpose, twenty fish (initial mean weight of 4.80 ± 0.06 g) were placed into twelve tanks (400 L) in triplicate and fish were fed with control (C) and three different levels (0.01, 0.05, and 0.1 g/kg) of A. graveolens (AG) extract-containing diets (AG0.01, AG0.05, and AG0.1) for 30 days. Blood and tissue (kidney, spleen, and intestine) samples were taken from the fish every 10 days during the study to determine the immune responses of the fish. Respiratory burst activity (RBA) was significantly decreased in the AG0.1 group compared to all other groups on the 10th day of the study (P < 0.05). Significance was noticed in the RBA of fish in all AG groups compared to the C group (P < 0.05) on the 30th day of the experiment Lysozyme activity (LYS) was raised on the 10th day of the study in all celery groups compared to the C group (P < 0.05). No differences in the myeloperoxidase activity (MPO) were observed among the experimental groups (P > 0.05). The final mean weight (FMW) was not affected in any experimental groups (P > 0.05). However, in the AG0.05 group, the specific growth rate (SGR) increased, and the feed conversion ratio (FCR) decreased compared to other groups (P < 0.05). IL-1β in the kidney was highly elevated in the AG0.01 group on the 20th day of the study (P < 0.05). Similar results were observed on IL-6, IL-8, and TNF-α expression in the kidney (P < 0.05). Anti-inflammatory responses (IL-10 and TGF-β) also increased in all experimental groups and tissues compared to the C group (P < 0.05). COX-2 was upregulated on the 20th day of the study in all tissues (P < 0.05). At the end of the feeding trial, the survival rate of the AG0.1 group in fish infected with Vibrio anguillarum infection was higher than the C group. Dietary celery extract did not affect growth performance directly but increased innate immune responses and a high survival rate. Overall, compared to the control group, the growth, immunity, and resistance of European seabass fed with a diet containing 0.05 g/kg celery aqueous methanolic extract has been improved, and this could be used as an immunostimulant feed additive.

Dietary Arthrospira platensis in Rainbow Trout (Oncorhynchus mykiss): A Means to Reduce Threats Caused by CdCl2 Exposure?

The rainbow trout (Oncorhynchus mykiss) is one of the most commercially sought-after freshwater fish species and one of the most farmed in the world. On the other hand, aquaculture breeding frequently results in outbreaks of infectious diseases and pests, and compromises the production and welfare of fish. Arthrospira platensis (known as "Spirulina") has been used as a supplement in diets to enhance fish welfare in recent years because of its beneficial properties. This study aimed to assess the possible protective effects of Arthrospira platensis on rainbow trout specimens exposed to three different doses of the toxicant CdCl₂. The experiment was carried out using five experimental treatments of 40 individuals each: control group; group II (0.2 mg CdCl₂ per kg of commercial fish feed); group III (0.2 mg Kg^-1 of CdCl₂ plus 2.5 g per kg of A. platensis); group IV (0.2 mg Kg^-1 of CdCl₂ plus 5 g per kg of A. platensis); group V (0.2 mg Kg^-1 of CdCl₂ plus 10 g per kg of A. platensis). During the experiment, dietary supplementation of A. platensis normalized all serum and blood parameters altered by the presence of CdCl₂. A. platensis also had a protective effect on markers of oxidative stress.

A mini-review on co-supplementation of probiotics and medicinal herbs: Application in aquaculture

The aquaculture industry is geared toward intensification and successfully meets half of the world's demand for fish protein. The intensive farming system exposes the animal to the risk of disease outbreaks, which has economic consequences. Antibiotics are commonly used for the health management of aquaculture species. However, this has several drawbacks, including the increase in antibiotic resistance in pathogenic bacteria and the entry of antibiotic residues into the human food chain, which is a public health and environmental concern. The potential of probiotics, prebiotics, synbiotics, and medicinal herbs as alternatives to antibiotics for the health management of aquaculture species has been investigated in numerous studies. This review discusses the potential use of combinations of probiotics and medicinal herbs as prophylactic agents in aquaculture, along with the definitions, sources, and modes of action. The positive aspects of combining probiotics and medicinal herbs on growth performance, the immune system, and disease resistance of aquaculture species are also highlighted. Overall, this review addresses the potential of combinations of probiotics and medicinal herbs as feed additives for aquaculture species and the key role of these feed additives in improving the welfare of aquaculture species.

Replacement of refined sugar by natural sweeteners: focus on potential health benefits

Refined sugar is a processed product containing 99% sucrose, which is obtained from sugarcane (70%) or sugar beet (30%). In modern societies, sugar continues to play a significant role in the diet, recognised not only for its flavour and special sweetening properties but also for its role in food preservation. On the other hand, a high consumption of refined sugar is associated with non-communicable diseases and many health issues such as a high risk of dental caries, overweight and neurodevelopmental disorders in children. Alternatives like unrefined sugars have generated a lot of interest as a healthy substitute due to their nutraceutical properties. This paper is aimed to review the beneficial effects of sugar derived from natural sources and highlight health problems that could be caused by refined processed sugar. Refined sugar is frequently used in variety of items including processed foods, soft drinks or ice creams although it is considered unhealthy due to its high salt and sugar content as well as added fats and artificial coloring. Natural sugars are preferred because they have a high nutritional value and a high concentration of healthy compounds, which offset the negative effects of refined sugar. Therefore, removing refined sugar or at least reducing its consumption should be promoted as a healthier option in food choices.

The effects of dietary immunostimulants on the innate immune response of Indian major carp: A review

Immunostimulants, as feed additives, play an important role in maintaining fish health and enhancing their overall growth by providing resistance against diseases in cultured fish. At the initial stages of life of fish, innate immunity is the essential mechanism in their survival. Later, innate immunity has an instructive role in adapting acquired immune response and homeostasis through different receptor proteins. Several studies have been conducted to analyze the effect of dietary immunostimulants like algae, plant extracts, vitamins, herbs, probiotics, and prebiotics-containing diets in Indian major carps. Many bacterial, fungal and viral pathogens are responsible for high death rates in both wild and cultured fish. It's a major limiting factor for world aquaculture industries. Recognition of invading pathogens by different pathogen recognition receptor plays an important role for the activation of different pathways to initiate protective immune responses. Hence, there is a growing need to control the devastating effects of diseases without recourse to toxic chemicals or antibiotics. Keeping with alternative approaches without using toxic chemicals to control fish diseases in mind, many immunostimulants are used, which enhance immune responses along with their gene expression level through different signaling pathway. The objective of this review is to summarize and evaluate the current knowledge of various immunostimulants and their immune responses in three Indian major carps namely Catla catla, Labeo rohita and Cirrhinus mrigala, which are preferred by the people.

Effect of Licorice (Glycyrrhiza glabra) Extract as an Immunostimulant on Serum and Skin Mucus Immune Parameters, Transcriptomic Responses of Immune-Related Gene, and Disease Resistance Against Yersinia ruckeri in Rainbow Trout (Oncorhynchus mykiss)

This study was designed to appraise the effect of licorice herbal supplement on the immune status of rainbow trout fingerlings. Accordingly, five diets were formulated with different levels of licorice extract (LE) including 0 (control), 0.5 g kg−1 (LE0.5), 1 g kg−1 (LE1), 2 g kg−1 (LE2), and 3 g kg−1 (LE3). The fingerlings (10.0 ± 0.1 g initial mean weight) received the diets in triplicates (30 fish in each replicate) for 56 days. The results showed that the white blood cells and their differential number (lymphocytes and monocytes) were remarkably increased by LE2 supplementation (P &lt; 0.05). The oral administration of LE2 significantly increased the levels of serum immunoglobulin (Ig), lysozyme activity, and complement components (C3 and C4) compared with others. Meanwhile, the serum bactericidal activity against Yersinia ruckeri in LE2 and LE3 treatments was significantly higher than others except for LE1 (P &lt; 0.05). In addition, serum alternative complement activity significantly improved in all treated groups except LE0.5 compared with the control group (P &lt; 0.05). In terms of skin mucosal immunity, the fish fed with LE2 and LE3 diets exhibited notably higher lysozyme activity, alkaline phosphatase activity, and Ig value than other groups (P &lt; 0.05). The highest skin mucus bactericidal activity against Y. ruckeri was obtained in LE2 treatment (P &lt; 0.05). In addition, dietary LE2 significantly increased the relative expression of immune-associated genes including tumor necrosis factor-α, interleukin-1β, interleukin-8, and IgM and the former treatments showed higher values than the control group. The cumulative mortality of fish against Y. ruckeri infection was notably reduced from 53.6% in the control group to 29.0% in LE3 treatment. Overall, the dietary administration of LE at 2 g kg−1 had the best effects on immunocompetence in rainbow trout.

A Solution for Sustainable Utilization of Aquaculture Waste: A Comprehensive Review of Biofloc Technology and Aquamimicry

Biofloc technology (BFT) is gaining traction as a strategic aquaculture tool for boosting feed conversions, biosecurity, and wastewater recycling. The significant aspect of BFT is aquaculture with highest stocking density and minimal water exchange. It not only improves the water quality of a system by removing inorganic nitrogen from wastewater but also serves as a suitable feed supplement and probiotic source for cultured species. This technology is commonly used for shrimp and tilapia culture and can be used for both semi-intensive and intensive culture systems. Biofloc, when combined with formulated diets, forms a balanced food chain that improves growth performance. Nutrients in this system are continuously recycled and reused and form an efficient alternative system in aquaculture. In addition to the reduction in water exchange, it is also considered as a bio-security measure, since it prevents entry of disease from outside sources. Aquamimicry is an innovative concept that simulates natural estuarine conditions by developing copepods that act as supplementary nutrition especially for shrimp culture. The review highlights the process, significance, and development of BFT, its microbial interactions, nutritional value, transition from biofloc to copefloc, and concept of aquamimicry to sustainably improve aquaculture production.

Dietary Lactobacillus acidophilus ATCC 4356 Relieves the Impacts of Aflatoxin B1 Toxicity on the Growth Performance, Hepatorenal Functions, and Antioxidative Capacity of Thinlip Grey Mullet (Liza ramada) (Risso 1826)

Dietary Lactobacillus acidophilus ATCC 4356 was used to relieve the impacts of aflatoxin B₁ toxicity on the performances of Liza ramada. The control diet was without any additives, while the second and third diets were supplemented with aflatoxin B₁ at 0.5 and 1 mg/kg. The fourth diet was supplemented with Lb. acidophilus ATCC 4356 at 1 × 10⁶ CFU/mL per kg diet, while the fifth with aflatoxin B₁ at 1 mg/kg and Lb. acidophilus ATCC 4356 at 1 × 10⁶ CFU/mL per kg diet. The growth performance markedly increased (p < 0.05) in L. ramada fed Lb. acidophilus ATCC 4356, while aflatoxin B₁ at 0.5 and 1 mg/kg groups showed a severe reduction. The red blood cells, hemoglobulin, hematocrit, and white blood cells were markedly increased in L. ramada fed Lb. acidophilus ATCC 4356 while decreased (p < 0.05) in fish fed aflatoxin B₁ at 0.5 and 1 mg/kg. The blood total protein and albumin were markedly increased (p < 0.05) in L. ramada fed Lb. acidophilus ATCC 4356 while reduced in aflatoxin B₁ at 0.5 and 1 mg/kg groups. The levels of total cholesterol and triglycerides were meaningfully increased in fish of the Lb. acidophilus ATCC 4356 and aflatoxin B₁ at 1 mg/kg groups while decreased in aflatoxin B₁ at 0.5 and 1 mg/kg groups. Alanine aminotransferase, aspartate aminotransferase, creatinine, and urea levels were markedly decreased (p < 0.05) in fish-fed Lb. acidophilus ATCC 4356 while increased in aflatoxin B₁ at 0.5 and 1 mg/kg groups. The highest levels of blood glucose and cortisol were seen in fish contaminated with aflatoxin B₁ at 1 mg/kg, while the lowest levels were observed in the fish fed Lb. acidophilus ATCC 4356 group (p < 0.05). The catalase and superoxide dismutase were markedly enhanced in the Lb. acidophilus ATCC 4356 group and severely declined in aflatoxin B₁ at 0.5 and 1 mg/kg groups (p < 0.05). The malondialdehyde level was markedly reduced in fish fed Lb. acidophilus ATCC 4356 with or without aflatoxin B₁ at 1 mg/kg diets while increased in fish contaminated with aflatoxin B₁ at 0.5 and 1 mg/kg (p < 0.05). The control group had lower malondialdehyde levels than the aflatoxin B₁ at 1 mg/kg group and higher than the Lb. acidophilus ATCC 4356 with or without aflatoxin B₁ toxicity (p < 0.05). Histopathological examination revealed impaired intestines and livers in fish contaminated with aflatoxin B₁ while Lb. acidophilus ATCC 4356 relieves the inflammation and protected the intestines and livers. In conclusion, dietary Lb. acidophilus ATCC 4356 is recommended to relieve the impacts of aflatoxicosis-induced hepatorenal failure and oxidative stress in L. ramada.

Lactobacillus fermentum HFY06 attenuates D-galactose-induced oxidative stress and inflammation in male Kunming mice

There has been considerable research on oxidative stress and inflammation, and their relationship with degenerative diseases. This study investigated the effect of Lactobacillus fermentum HFY06 on aging mice induced by D-galactose. The results showed that L. fermentum HFY06 inhibited the atrophy of the brain, kidneys, liver, and spleen, increased serum SOD, GSH, CAT, and MDA, and decreased IL-6, IL-1β, TNF-α, and IFN-γ. Quantitative PCR showed that L. fermentum HFY06 upregulated the expression of Nrf2, γ-GCS, NOS1, NOS3, SOD1, SOD2, and CAT in the liver and brain tissues, but decreased the expression of NOS2. Western blot analysis showed that L. fermentum HFY06 effectively upregulated the protein expression of SOD1, SOD2, and CAT in the livers and brains of mice. These results suggest that L. fermentum HFY06 can effectively alleviate D-galactose-induced aging in mice, and may activate the Nrf2 signaling pathway and increase the levels of downstream regulatory inflammatory factors and antioxidant enzymes. In conclusion, consumption of L. fermentum HFY06 may prevent aging or reduce oxidative stress.

Use of multi-strain probiotics in linseed meal based diet for Labeo rohita fingerlings

Unavailability of probiotics in fish digestive system fingerlings is unable to digest and absorb their food properly. The current research was conducted to investigate the influence of probiotics added Linseed meal based (LMB) diet on hematology and carcass composition of Labeo rohita juveniles. Hematological parameters are essential diagnostics used to estimate the health status of fish. The usage of probiotics for fish health improvement is becoming common due to the higher demand for environment-friendly culture system in water. Linseed meal was used as a test ingredient to prepare six experimental test diets by adding probiotics (0, 1, 2, 3, 4 and 5 g/kg) and 1% indigestible chromic oxide for seventy days. According to their live wet weight, five percent feed was given to fingerlings twice a day. Fish blood and carcass samples (Whole body) were taken for hematological and carcass analysis at the end of the experiment. The highest carcass composition (crude protein; 18.72%, crude fat; 8.80% and gross energy; 2.31 kcal/g) was observed in fish fed with test diet II supplemented with probiotics (2 g/kg). Moreover, maximum RBCs number (2.62× 106mm-3), WBCs (7.84×103mm-3), PCV (24.61), platelets (63.85) and hemoglobin (7.87) had also been reported in the fish fingerlings fed on 2 g/kg of probiotics supplemented diet. Results indicated that probiotics supplementation has a critical role in improvement of fingerlings' body composition and hematological indices. Present findings showed that probiotics supplementation at 2 g/kg level in linseed by-product-based diet was very useful for enhancing the overall performance of L. rohita fingerlings.

The ERβ-CXCL19/CXCR4-NFκB pathway is critical in mediating the E2-induced inflammation response in the orange-spotted grouper (Epinephelus coioides)

The main physiological function of 17β-estradiol (E2) in vertebrates is to regulate sexual development and reproduction. In fish, especially hermaphroditic fish, estrogen is often used to aid reproduction, but it also can trigger an inflammatory response. However, the molecular mechanism for this E2-induced inflammatory reaction is not clear. In this study, we found that the ERβ-CXCL19/CXCR4-NFκB cascade regulated the E2-induced inflammatory response in the orange-spotted grouper (Epinephelus coioides). Strikingly, E2 treatment resulted in significantly high expression of inflammatory cytokines and induced phosphorylation and degradation of IκBα and translocation of NFκB subunit p65 to the nucleus in grouper spleen cells. However, the E2-induced inflammatory response could be prevented by the broad estrogen receptor (ER) ligand ICI 182,780. Moreover, the luciferase assay showed that E2 induced the inflammatory response by activating the promotor of chemokine CXCL19 through ERβ1 and ERβ2. Knockdown of CXCL19 blocked the E2-induced inflammatory response and NFκB nucleus translocation. Additionally, knockdown of chemokines CXCR4a and CXCR4b together, but not alone, blocked the E2-induced inflammatory response. The immunofluorescence assay and co-immunoprecipitation analysis showed that CXCL19 mediated the E2-induced inflammatory response by activating CXCR4a or CXCR4b. Taken together, these results showed that the ERβ-CXCL19/CXCR4-NFκB pathway mediated the E2-induced inflammatory response in grouper. These findings are valuable for future comparative immunological studies and provide a theoretical basis for mitigating the adverse reactions that occur when using E2 to help fish reproduce.

The Effect of Lactococcus lactis subsp. lactis PTCC 1403 on the Growth Performance, Digestive Enzymes Activity, Antioxidative Status, Immune Response, and Disease Resistance of Rainbow Trout (Oncorhynchus mykiss)

The effect of Lactococcus lactis subsp. lactis strain PTCC 1403 as a potential probiotic was investigated on the growth, hematobiochemical, immune responses, and resistance to Yersinia ruckeri infection in rainbow trout. A total of 240 fish were distributed into 12 fiberglass tanks representing four groups (× 3 replicates). Each tank was stocked with 20 fish (average initial weight: 11.81 ± 0.32 g) and fed L. lactis subsp. lactis PTCC 1403 at 0 (control, T0), 1 × 10⁹ (T1), 2 × 10⁹ (T2), and 3 × 10⁹ (T3) CFU/g feed for 8 weeks. The results showed enhanced protein efficiency ratio and reduced feed conversion ratio in the fish-fed T2 diet. Further, fish-fed T2 and T3 diets showed a significantly higher survival rate than the control (p < 0.05). Trypsin, lipase, and protease activities were increased in fish-fed L. lactis subsp. lactis PTCC 1403 compared to the control (p < 0.05). Fish fed with a T2 diet showed significantly (p < 0.05) lower glucose content than other groups. The blood lysozyme activity and IgM showed significantly (p < 0.05) higher values in fish-fed T2 and T3 diets than in other groups. The antioxidative responses were increased in fish-fed T2 and T3 diets (p < 0.05). After 7 days post-Y. ruckeri challenge, the cumulative mortality rate showed the lowest value in fish fed with T1 and T2 diets, while the highest value was recorded in the control group. In conclusion, the results revealed beneficial effects of L. lactis subsp. lactis PTCC 1403 on the feed efficiency, immune response, and resistance to Y. ruckeri infection in rainbow trout.

Effects of Essential Oil Derived from the Bitter Orange (Citrus aurantium) on Growth Performance, Histology and Gene Expression Levels in Common Carp Juveniles (Cyprinus carpio)

Simple Summary

The aim of this analysis was to reveal the effects of Citrus aurantium essential oil on growth performance, histopathological effect on digestive system organs, expression levels of some growth-related genes in the muscle tissue and some immune-related genes in the head kidney of common carp Cyprinus carpio. To determine the effect of essential oil on carp, experimental diets containing different concentrations of essential oil were prepared, and the fish were fed these diets for 60 days. At the end of the feeding experiment, it was observed that low-dose essential oil supplementation increased immune related gene expression levels and growth-related gene expression levels in head kidney and muscle tissue, respectively. Pathological findings were observed in the liver and intestines of fish fed with high doses of essential oil supplemented diets.

Abstract

The aim of this study was to detect effects of bitter orange (Citrus aurantium) essential oil, commonly called neroli oil (NO) (0, 0.25, 0.50, 1, and 1.5% referred to as NO₀ NO_0.25, NO_{0. 05}, NO₁ and NO_1.5, respectively) on growth performance output and expression levels of some growth-related genes in the muscle tissue and some immune-related genes in the head kidney and pathological differences in digestive system organs of common carp Cyprinus carpio. The NO_0.25 group had a large improvement in growth efficiency at the end of the 60-day feeding cycle. Real-time PCR (Bio RAD, USA) system was used to detect variations in gene expression levels. Furthermore, NO supplementation of up to 0.25% in muscle tissue controlled the release of growth hormone (GH) and insulin-like growth factor I (IGF-I). Furthermore, in the NO_0.25 treatment category, immune response gene levels TNF-α, IL-8 and IL-1ß increased in head kidney tissue. In the histological examination of the liver and intestine, there were significant differences between fish fed with N₁ and N_1.5 diets. This study confirms that dietary supplementation of NO up to 0.25% can improve common carp growth efficiency and increase the expression of genes (GH and IGF-I) related to muscle growth, TNF-α, IL-8 and IL-1ß genes related to immune status, and liver and intestine histological status of common carp.

Synergistic effect of durian fruit rind polysaccharide gel encapsulated prebiotic and probiotic dietary supplements on growth performance, immune-related gene expression, and disease resistance in Zebrafish (Danio rerio)

The present study investigated the effect of polysaccharide gel (PG) extracted from the rind of durian fruit which is encapsulated with Bacillus subtilis as a feed and co-inoculation with Artemia nauplii in the induction of immune response in Danio rerio after Vibrio immersion challenge (5 days). The total RBC count, lysozyme activity test, weight, and length analysis revealed that the zebra fishes fed with the PG encapsulated probiotics had more immune induction activity, survival, and growth than the non-encapsulated groups. When the expression of the immune-related genes was measured, the studies revealed the significant upregulation (P < 0 .05) of interleukin 1 beta (Il1b), lysozyme (lyz), tumor necrosis factor-alpha (TNF-α), superoxide dismutase (SOD) genes in fish fed with PG encapsulated probiotics with A. nauplii showed an immense effect on the induction of immune response compared to other feeds.

Extract of Aloe vera (Aloe barbadensis Miller) Enhances the Growth, Protein Contents, and Gastrosomatic Index (GaSI) of Common Carp Cyprinus carpio

Aquaculture is a growing agribusiness, and large-scale microbial infection frequently leads to considerable economic losses, as there are very few approved drugs available to counteract such a problem. Aloe vera is a natural therapeutic plant with biological activities, for example, antimicrobial, anticancer, mitigating, and immunomodulatory properties. Thus, an experiment was conducted to understand the effects of dietary Aloe vera on survival, growth performance, protein utilization, gastrosomatic index, and gut histomorphological studies in common carp in laboratory conditions. Aloe vera leaves were collected, washed, shade-dried, and homogenized to get a filtrate, which was extracted in ethanol (70%) using the Soxhlet apparatus. The carp with an average weight of 1.73 ± 0.14 g was divided randomly into 5 treatments (control and other 4 treated groups) with the extract of 0.0%, 0.2%, 0.4%, 0.8%, and 1.6% in the diet with 3 replicates and the stocking density was 25 fish per each replicate. Sampling was done on the 30th, 60th, and 90th days, and the results show that percent weight gain, specific growth rate, protein efficiency ratio, and feed conversion efficiency were significantly high in the treated diet compared to the control (0.0%). Gastrosomatic index, condition factors, and gut histology found better performance in common carp group fed 0.4% and 0.8% of Aloe vera after 90 days. In conclusion, it was found that Aloe vera extract between the amount of 0.4% and 0.8% is better for fish growth for common carp.

The Immunostimulatory Effects of Commercial Feed Additives on Growth Performance, Non-specific Immune Response, Antioxidants Assay, and Intestinal Morphometry of Nile tilapia, Oreochromis niloticus

The main objective of the present research was to investigate the impacts of commercial immunostimulants on growth, non-specific immune response, antioxidant enzymes, and intestinal morphometry of Nile tilapia, Oreochromis niloticus. Fish (100 ± 6.5 g) were randomly divided into five groups in triplicates (150 fish in each replicate), stocked in 20 m² of aerated concrete ponds. The fish were fed on a control diet (30.0% crude protein) (control), and four experimental diets supplemented with Yeast Plus^®, Digestarom^®, and Biotronic^® Top³ at 1 kg ton^–1, and Sanolife PRO-F^® at 0.5 kg ton^–1. After the experimental period, the highest significant yield (kg m^–3), mean final weight (g fish^–1), average weight gain (g fish^–1), and specific growth rate (% body weight day^–1), were recorded in fish fed on the diet supplemented by Sanolife PRO-F, followed by Yeast Plus ponds. The lowest yield was recorded in the control group. However, the feed conversion ratio was significantly decreased with Sanolife PRO-F diet. Furthermore, the hematological analysis increased in the following ascending order: Sanolife PRO-F^®; Yeast Plus^®; Biotronic^® Top3 and finally Digestarom^® groups. The lowest concentrations of white blood cells, red blood cells, hematocrite, and hemoglobin (P ≤ 0.05) were observed in the control group. The levels of phagocytic activity and phagocytic index were significantly higher in fish fed with Sanolife PRO-F^® group (P ≤ 0.05). Likewise, serum lysozyme activity was significantly highest in Sanolife PRO-F (0.63 and 0.68 U/mL, after 0.5 min and 3 min, respectively). Levels of total serum proteins, globulin, Immunoglobulin M, catalase, and super oxide dismutase were significantly higher in fish fed with Sanolife PRO-F^® supplement. On the contrary, length measurement of the intestinal villus height/width, absorption area, crypt depth, and goblet cells, were significantly lower in the control group, whereas their highest values was observed in fish fed Sanolife PRO-F (P ≤ 0.05). Consequently, Sanolife PRO-F^® is recommended at a level of 0.5 kg ton^–1, to improve the growth performance, antioxidative capacity, and immune response of Nile tilapia.

Probiotic lactobacilli: Can be a remediating supplement for pandemic COVID-19. A review

In recent years increased attention is focussed on microorganisms inhabiting the digestive system that provides prophylactic and therapeutic benefits to the host. After Metchnikoff exposed the secret behind Bulgarian peasants' extended longevity, a graze to incorporate the responsible microbes in functional food emerged. Then interest towards microbe-rich food went to the vegetative phase for some time, but now a renaissance to engage these wonder microbes in the healthcare sector is increasing. With a new definition, probiotics, these good microbes have been widely applied in different types of products, either as pharmaceuticals, nutritional supplements, or foods. Probiotics, a significant source in functional dairy products, claims diverse roles such as improving intestinal tract health, enhancing the immune system, synthesizing and enhancing the bioavailability of nutrients, reducing symptoms of lactose intolerance, decreasing the prevalence of allergy in susceptible individuals, and reducing the risk of certain cancers. In the recent COVID-19 issue, searches are going fast to use probiotics as vaccine carriers, dysbiosis balancer, and immunity booster. The high expectation from probiotics expanded the development of bioengineered probiotics as new-generation probiotics. From the animal model and in vitro studies, the probiotic intervention is extrapolated to innate and adaptive immunity inducer against SARS viral infections. The possibility of using it as prophylactic and therapeutic agents in COVID-19 is explored. However, its significant activity against corona virus-induced respiratory syndromes is questioned by a few researchers also. The emerging citations on the research approach and meta-analysis of probiotic intervention against the re-emerging pandemic viral attack on the respiratory and gastrointestinal domains need to be analyzed in this context. As it is essential to understand the reality of recent experimental outcomes in the probiotic approach towards SARS-CoV-2 prevention, management, and control, the recent publications were focused on this review.

Stimulatory effect of dietary chasteberry (Vitex agnus-castus) extract on immunity, some immune-related gene expression, and resistance against Aeromonas hydrophila infection in goldfish (Carassius auratus)

Chasteberry is highly recommended as an herbal medicine across the globe for treating of many gynaecological disorders. In this study, chasteberry extract (CBE) was supplemented in goldfish diet to evaluate the immunity responses at the cellular and molecular levels. Moreover, after the feeding trial, the fish were challenged with Aeromonas hydrophila. The fish (300 individuals, 2.4 ± 0.12 g initial weight) were randomly distributed in 12 tanks and were fed with 0 (control), 5, 10, and 15 g CBE per kg of feed for 8 weeks. Based on the results, lysozyme activity, alkaline phosphatase, and total immunoglobulin (Ig) in the skin mucus samples were significantly enhanced in the fish fed with 15 g/kg CBE (P < 0.05). Moreover, dietary CBE positively affected lysozyme activity, complement components, and IgM content of the serum samples compared to the control group. Also, the number of monocytes and lymphocytes were increased significantly with increasing CBE in the diet (P < 0.05). The highest mRNA levels of tumor necrosis factors (TNF-α, TNF-2α) and Lysozyme were observed in 15 g/kg CBE treatment. After the challenge test, the highest relative percentage survival value (60%) was observed in the fish fed with 15 g/kg CBE. We concluded that dietary CBE especially at 15 g/kg has an immunomodulatory effect in goldfish by stimulating the innate immunity and some inflammatory cytokines as well as disease resistance against A. hydrophila.

Dietary supplementation of salidroside increases immune response and disease resistance of crucian carp (Carassius auratus) against Aeromonas hydrophila

Some medicinal plants have been known as immunostimulants, and the medicinal plants extract has been used to control the outbreak of the disease in aquaculture for many years. In this study, a total of 270 crucian carp (30 ± 5 g) were randomly distributed in 9 aquaria (55 cm l × 40 cm w × 50 cm h) and divided into three feeding groups including 0 (Control), 50 mg kg^-1 (Diet A) and 100 mg kg^-1 (Diet B) of salidroside. The expression of immune-related genes (IL-1β, TNFα, MYD88, CXCL-8, TGF-β, and IL-11) in the kidney had a significant increase when the crucian carp fed with Diet B for 4 weeks (P < 0.05). Meanwhile, the expression of IL-1β, TNFα, and CXCL-8 in the spleen was significantly up-regulated when the fish fed with Diet B (P < 0.05). Higher serum alkaline phosphatase (AKP) activity, catalase (CAT) activity, superoxide dismutase (SOD) activity, and complement C3 content were found in the fish which fed with salidroside-supplemented diet. Our results also proved that fish fed with salidroside-supplemented diet for four weeks, especially at a concentration of 100 mg kg^-1 diet, improved the protection of crucian carp against A. hydrophila. The amount of A. hydrophila in the kidney and spleen was significantly decreased in salidroside-supplemented diet groups (P < 0.05). In conclusion, the present results demonstrate that the addition of salidroside for four weeks can improve the immune response of crucian carp and increase the protection against the pathogen, especially at the concentration of 100 mg kg^-1 diet. The protective effect of the salidroside to the crucian carp could be used as alternatives to antibiotics for controlling fish diseases in aquaculture.

Singular effects of Bacillus subtilis C-3102 or Saccharomyces cerevisiae type 1 on the growth, gut morphology, immunity, and stress resistance of red sea bream (Pagrus major)

The beneficial effects of Bacillus subtilis C-3102 and Saccharomyces cerevisiae type 1 were tested in red sea bream (Pagrus major) feeds. A basal diet (control) and two other diets were prepared by supplementation with B. subtilis C-3102 (PB) or S. cerevisiae type 1 (PY). After 60 days, both probiotic-supplemented groups exhibited significant enhancement in growth performance, the protein efficiency ratio (PER), and digestive enzyme secretion (protease and amylase) compared to the control group (P<0.05). The anterior, middle, and posterior parts of the intestines exhibited significantly increased values of intestinal fold height (hF), enterocyte height (hE), and microvillus height (hMV) in fish fed PB- or PY-supplemented diets (P<0.05). Serum peroxidase, anti-protease, and bactericidal activities were enhanced significantly in both probiotic-treated groups compared to the control group (P<0.05). Serum and mucus lysozyme activities improved significantly in the PB group compared to the control group (P<0.05). Catalase activity was also significantly decreased in both probiotic groups, with relatively lower activity observed in the PY group (P<0.05). Both probiotic groups showed increased tolerance considerably to freshwater exposure (P<0.05). In conclusion, B. subtilis C-3102 and S. cerevisiae type 1 can be used as functional probiotics to enhance the growth performance, digestion capacity, gut morphology, immune response, and stress resistance of the red sea bream with relatively higher efficiency by B. subtilis C-3102.

Effects of Dietary Doum Palm Fruit Powder on Growth, Antioxidant Capacity, Immune Response, and Disease Resistance of African Catfish, Clarias gariepinus (B.)

Application of herbal immune-stimulants for modulation of fish growth and immune response has received great interest during the past decades. With several pharmacological properties, Doum palm, Hyphaene thebaica (Mart.) is known to be a beneficial medicinal plant. The objective of this study was to investigate the effects of the dietary addition of doum palm fruit powder (DPFP) on growth performance, non-specific immune response, and antioxidant parameters of African catfish, Clarias gariepinus (B.). A total of 120 fish (average initial weight 60.50 ± 0.04 g) were randomly allocated to four groups (three replicates/group, 10 fish/aquarium); a basal diet without DPFP supplementation was used as a control, and three other diets were prepared by supplementing 5, 10, or 15 g kg^-1 DPFP for a ten-week feeding period. Following ten weeks of feeding, the fish were challenged with Aeromonas hydrophila (as an immune challenge test), and mortalities were recorded. In comparison to the control diet, dietary DPFP significantly improved growth parameters, including final body weight, body weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER), along with an increase in the content of dry matter of the whole body, in a concentration-dependent manner. Moreover, the heights of intestinal villi, numbers of goblet cells, and intraepithelial lymphocytes (IEL) exhibited marked escalation in all parts of the intestine by increasing the level of DPFP, except for numbers of IEL in the proximal part. The decline in serum glucose, cholesterol, and triglyceride levels was prominent in DPFP10 and DPFP15 groups respective to the DPFP0 group. Furthermore, DPFP boosted the hepatic level of catalase (CAT) in the fish, in a dose-dependent manner; meanwhile, the activity of superoxide dismutase (SOD) and reduced glutathione (GSH) content were also augmented in DPFP10 and DPFP15 groups respective to the DPFP0 group. Dietary DPFP (DPFP15 followed by DPFP10 then DPFP5) led to a pronounced enhancement in the innate immune response (phagocytic percent and index, lysozyme activity, nitric oxide (NO) production, and sialoglycans, namely α 2,3-sialyltransferase and α 2,6-sialyltransferase content); however, the myeloperoxidase (MPO) activity was reduced. Significantly higher relative percentage survival (RPS, 88.56%) of the fish, following the A. hydrophila challenge, was observed for the DPFP15 group. We can suggest that DPFP can beneficially influence fish growth, intestinal histomorphology, hepatic levels of catalase (CAT), superoxide dismutase (SOD) activity and glutathione (GSH) content, immune response, and disease resistance against A. hydrophila challenge.

Dietary supplementation with Lactobacillus acidophilus enhanced the growth, gut morphometry, antioxidant capacity, and the immune response in juveniles of the common carp, Cyprinus carpio

This study investigated the effect of Lactobacillus acidophilus-fortified diets on growth performance, antioxidant profiles, and immunity-related gene expressions of common carp, Cyprinus carpio juveniles. Four isonitrogenous diets containing 0, 10², 10⁴, or 10⁶ cfu/mL/kg L. acidophilus were fed to 240 Cyprinus carpio juveniles (mean = 21.34 ± 1.85 g), allotted to 12 rectangular tanks in a completely randomized designed at 3% body weight for 56 days. Growth performance and nutrient utilization were evaluated using standard procedures. Intestinal villi were measured, antioxidant profiles were evaluated from blood sera, and immunity-related gene expressions were evaluated. The results revealed that fish fed dietary 10⁶ had significantly higher weight gain, SGR, feed intake, and lower FCR. Also, villi length, width, and areas of absorption were significantly improved in a dose-dependent manner. Furthermore, innate immune profiles, superoxide dismutase, catalase, respiratory bust activity as well as transforming growth factor beta (TGFβ), interleukin 8 (IL-8), and tumor necrosis factor alpha (TNF-alpha) were significantly stimulated. This study evoked that Lactobacillus acidophilus supplementation enhanced better growth performance, improved antioxidant profiles, and modulated expression of immune-related genes of common carp, Cyprinus carpio, than the fish fed control diet. Results show that fish fed fortified diets had better growth performance, improved antioxidant profiles, and modulated expression of immune-related genes.

Inclusion of dietary Ulva ohnoi 5% modulates Solea senegalensis immune response during Photobacterium damselae subsp. piscicida infection

Macroalgae represent valuable sources of functional ingredients for fish diets, and the influence of supplemented aquafeeds on growth performance has been studied for some fish and seaweed species. In the present work, the potential immunomodulation exerted by U. ohnoi (5%) as dietary ingredient was investigated in Senegalese sole. After feeding with the experimental diets for 90 d, fish immune response before and after challenge with Photobacterium damselae subsp. piscicida (Phdp) was assessed. In absence of infection, systemic immune response was not modified by 5% U. ohnoi dietary inclusion for 90 d. Thus, no differences in liver and head kidney immune gene transcription or serum lysozyme, peroxidase, antiprotease and complement activities were observed based on the diet received by Senegalese sole specimens. Regarding mucosal immune parameters, no changes in gene transcription were detected in the skin and gills, whilst only tnf, cd4 and cd8 were significantly up-regulated in the intestine of fish fed with U. ohnoi, compared to the values obtained with control diet. On the contrary, when S. senegalensis specimens were challenged with Phdp, modulation of the immune response consisting in increased transcription of genes encoding complement (c1q4, c3, c9), lysozyme g (lysg), tumor necrosis factor alpha (tnfα) as well as those involved in the antioxidant response (gpx, sodmn) and iron metabolism (ferrm, hamp-1) was observed in the liver of fish fed with U. ohnoi. In parallel, decreased inflammatory cytokine and complement encoding gene transcription was displayed by the spleen of fish receiving the algal diet. Though mortality rates due to Phdp challenge were not affected by the diet received, lower pathogen loads were detected in the liver of soles receiving U. ohnoi diet. Further research to investigate the effects of higher inclusion levels of this seaweed in fish diets, feeding during short periods as wells as to assess the response against other pathogens needs to be carried out.

Effect of Jasonia glutinosa on immune and oxidative status of gilthead seabream (Sparus aurata L.)

Jasonia glutinosa (rock-tea, RT) has numerous biological activities. In the present work, the beneficial effects of dietary RT on gilthead seabream (Sparus aurata L.) were studied. Fish fed experimental diets containing 0 (control), 10 or 30% of RT for 15 and 30 days. Samples from skin mucus, blood, head kidney, liver and gut were obtained at 15 and 30 days. The antioxidant properties from RT were analysed such as the antioxidant capacity and phenolic content. The heat shock protein 70 level (HSP70) and the total oxidized proteins were evaluated on skin mucus as stress markers. Immune parameters, both humoral (peroxidase activity, immunoglobulin M levels and complement activity) and cellular (phagocytic, respiratory burst and peroxidase activities) were determined in skin mucus, serum or head-kidney leucocytes, respectively. Concomitantly, the expression of different genes related to inflammation and oxidative stress was studied both in liver and gut. Skin mucus peroxidase was significantly increased on fish fed 10% RT for 15 days with respect to the control group. In addition, Serum IgM levels were significantly increased while HSP70 levels and oxidized proteins were significantly decreased on skin mucus from fish fed 30% RT for 30 days, respectively. Besides, cellular immune parameters (phagocytosis, respiratory burst and peroxidase activity) were significantly higher in leucocytes from fish fed the RT diets for 15 days, but not for 30 days. Finally, the gene expression of antioxidant enzymes was up-regulated in liver at 15 and in liver and gut at 30 days. However, the expression of il1b and hsp70 was down-regulated in the liver of fish fed 30% RT for 30 days with respect to the values of control fish. The possible inclusion of RT in fish diets as an additive with antioxidant and/or immunostimulant activities is discussed.

Effects of fucoidan on the hematic indicators and antioxidative responses of Nile tilapia (Oreochromis niloticus) fed diets contaminated with aflatoxin B1

Fucoidan is a rich source of medicinally active immunostimulants that possess various pharmacological properties. This study examined the potential impact of fucoidan on the hematic indicators and antioxidative responses of Nile tilapia fed diets contaminated with aflatoxin B₁ (AFB₁). Fish (60 ± 6.1 g) were allocated to five groups; the first (control) and second groups were fed 0% or 1% fucoidan-supplemented diets without AFB₁ contamination, while the third, fourth, and fifth groups were fed diets contaminated with AFB₁ and supplemented with 0%, 0.5%, and 1% fucoidan, respectively. After 30 days, fish fed AFB₁ showed high ALT, AST, ALP, cholesterol, urea, and creatinine levels; furthermore, total blood protein and tissue (liver, kidney, and gill) glutathione (GSH), glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT) activity significantly (P ≤ 0.05) decreased in fish fed AFB₁, while tissue malondialdehyde significantly increased (P ≤ 0.05). Interestingly, fish fed fucoidan showed decreased ALT, AST, ALP, cholesterol, urea, and creatinine, as well as increased blood protein, GSH, GPx, SOD, and CAT activity. The results suggested that fucoidan is capable of inducing protective activity against AFB₁ toxicity in Nile tilapia by enhancing the serum biochemical and tissue antioxidant responses of fish.

The effect of fishwort (Houttuynia cordata) on skin mucosal, serum immunities, and growth performance of Nile tilapia

The present study addressed the possible effects of fishwort (Houttuynia cordata) powder (FWP) on Nile tilapia's skin mucus parameter, serum immune response, and growth performance. Three hundred twenty tilapia fingerlings (average weight of 39.06 ± 0.16 g) were divided into four treatments and fed four levels of FWP; 0, 5, 10, and 20 g kg^-1 for 72 days. Completed randomised design of the four replications was applied and revealed that fish fed FWP significantly improved skin mucus lysozyme activity (SMLA). The highest value (P < 0.05) was recorded in fish fed 10 g kg^-1 FWP. However, no significant difference in SMLA was observed by feeding the fish 5 and 20 g kg^-1 FWP. Significant (P < 0.05) enhanced skin mucus peroxidase activity (SMPA) was observed in fish fed 10 g kg^-1 FWP, but no significant difference in SMPA was detected between FWP supplemented diets (5 and 20 g kg^-1 FWP) and the control group. Regarding serum immunity, dietary administration of FWP showed significantly (P < 0.05) improved serum lysozyme, peroxidase, alternative complement (ACH50), and phagocytosis vs. the control. The highest values of serum immunity (P < 0.05) were recorded in fish fed 10 g kg^-1 FWP. However, no significance in respiratory burst activity was observed. Similarly, no significant difference in growth performance, feed conversion ratio, and survival rate was observed in fish fed FWP compared to the control. In summary, diets supplemented with FWP (10 g kg^-1) increased the serum and mucosal immunity; however, no FWP supplementations had effects on Nile tilapia growth and survival rate.

Modulation of transcriptomic profile in aquatic animals: Probiotics, prebiotics and synbiotics scenarios

Aquaculture and fisheries have provided protein sources for human consumption for a long time, but diseases have induced declines in product benefits and raised concerns, resulting in great losses to these industries in many countries. The overuse of antibiotics for the treatment of diseases has increased the chemical concentrations in culture systems and weakened the natural immunity of aquatic organisms. Concerns regarding the detrimental effects of antibiotics on the environment and human health due to residual antibiotic-related issues encourage the development of reliable, environmental and health safety methods, such as vaccines, probiotics, prebiotics, synbiotics and phytobiotics, for protection against disease and for reducing and possibly eliminating disease occurrence. Immunity has been effectively enhanced by pro-, pre-, and synbiotics, which confer strong protection and reduce the risks associated with stressors and disease outbreaks in culture systems. These agents confer several benefits, including enhancing both host growth and immune responses against pathogens, while sustaining health and environmental stability, and their use is thus widely accepted. Alterations in gene expression in individual cells could serve as an indicator of the immunity and growth rate of aquatic animals after pro-, pre- and synbiotic feeding. This review addresses the potential use of pro, pre- and synbiotics as immunostimulants for improved aquaculture management and environmental health and chronicles the recent insights regarding the application of pro-, pre- and synbiotics with special emphasis on their immunomodulatory and antioxidative responses based on gene expression changes. Furthermore, the current review describes the research gaps and other issues that merit further investigation.

Extract of common mallow (Malvae sylvestris) enhances growth, immunity, and resistance of rainbow trout (Oncorhynchus mykiss) fingerlings against Yersinia ruckeri infection

The dietary effects of a native medicinal plant from Iran, common mallow (Malvae sylvestris), was evaluated on growth performance, innate immune parameters, mucosal immune parameters, and resistance of rainbow trout (Oncorhynchus mykiss) against Yersinia ruckeri. Therefore, 360 fish (initial weight 10.42 ± 0.09 g) were randomly distributed into 12 fiberglass tanks. Experimental diets supplemented with 0 (as control- C), 1% (M1), 3% (M2) and 5% (M3) levels of M. sylvestris flowers extract were fed to the fish based on 3% of body weight for 8 weeks. At the terminal sampling, growth performance, liver and digestive enzymes activities, blood and mucosal immune responses were determined. Results showed that M2 and M3 had greater final weight, weight gain, SGR, survival rate and lower FCR; higher levels of total protein, albumin, globulin, and lower cortisol levels in comparison to control; 5% extract also lowered cholesterol and glucose levels as well as Lactate Dehydrogenase (LDH) activity. We reported higher values of hematocrit, hemoglobin, Mean Corpuscular Hemoglobin (MCH), Mean Corpuscular Volume (MCV), White Blood Cell (WBC), Red Blood Cell (RBC) and lymphocytes for treated groups. Innate immune responses (Alternative complement activity (ACH50) in M2 and M3 group, total Immunoglobulin (Ig) and lysozyme in M3), mucosal immune parameters (ACH50, total Ig for M2 and M3 group and lysozyme in all treated groups) were enhanced. Activities of digestive enzymes (protease in all treated groups, amylase for 3 and 5%, while lipase only for 5%) and lower activity of liver ALT enzyme in individuals treated with highest dose was observed. Overall results indicated that the extract can positively affect growth performance and immune responses of rainbow trout.

Effects of dietary Gelsemium elegans alkaloids on intestinal morphology, antioxidant status, immune responses and microbiota of Megalobrama amblycephala

Numerous plant extracts used as feed additives in aquaculture have been shown to stimulate appetite, promote growth and enhance immunostimulatory and disease resistance in cultured fish. However, there are few studies on the famous Chinese herbal medicine Gelsemium elegans, which attracts our attention. In this study, we used the Megalobrama amblycephala to investigate the effects of G. elegans alkaloids on fish intestinal health after diet supplementation with 0, 5, 10, 20 and 40 mg/kg G. elegans alkaloids for 12 weeks. We found that dietary G. elegans alkaloids at 40 mg/kg improved intestinal morphology by increasing villus length, muscle thickness and villus number in the foregut and midgut and muscle thickness in the hindgut (P < 0.05). These alkaloids also significantly improved intestinal antioxidant capabilities by increasing superoxide dismutase, catalase, total antioxidant capacity and malondialdehyde levels and up-regulated intestinal Cu/Zn-SOD and Mn-SOD (P < 0.05) at 20 and 40 mg/kg. Dietary G. elegans alkaloids improved intestinal immunity via up-regulating the pro-inflammatory cytokines IL-1β, IL-8, TNF-α and IFN-α and down-regulating expression of the anti-inflammatory cytokines IL-10 and TGF-β (P < 0.05) at 20 and 40 mg/kg. The expression of Toll-like receptors TRL1, 3, 4 and 7 were also up-regulated in intestine of M. amblycephala (P < 0.05). In intestinal microbiota, the abundance of Proteobacteria was increased while the Firmicutes abundance was decreased at phylum level after feeding the alkaloids (P < 0.05). The alkaloids also increased the abundance of the probiotic Rhodobacter and decreased the abundance of the pathogenic Staphylococcus at genus level (P < 0.05). In conclusion, dietary G. elegans alkaloid supplementation promoted intestine health by improving intestine morphology, immunity, antioxidant abilities and intestinal microbiota in M. amblycephala.

Behavioral and immunotoxic effects of Prograf® (tacrolimus) in the male Siamese fighting fish

Siamese fighting fish (Betta splendens) has been extensively exploited in the behavioral and physiological toxicology studies of drugs. Tacrolimus is an immunosuppressant drug largely used in liver and renal transplantations. Here we found that a 7-day exposure of male B. splendens to concentrations of 0.05 and 0.1 µg/mL Prograf® (tacrolimus) caused alterations in aggression and immunity indexes. Tacrolimus exposed fish presented lower opercular display in a mirror test which is indicative of reduced aggression. In addition, serum levels of lysozyme, IgM, alternative complement, and bactericidal activity of subjects exposed to 0.1 µg/mL tacrolimus were lower than those from the control treatment. These results showed the behavioral impairment and immunotoxic impacts of tacrolimus in a model of aquatic toxicology. The results suggest fishes provide a possible model for better understanding of the drug action in vertebrates, and possible consequences for the environment via its effects on non-target organisms in an ecotoxicology context.

Lactobacillus fermentum and/or ferulic acid improved the immune responses, antioxidative defence and resistance against Aeromonas hydrophila in common carp (Cyprinus carpio) fingerlings

This study investigates the possible effects of using Lactobacillus fermentum (LF) and/or ferulic acid (FA) in common carp (Cyprinus carpio) on some immunological parameters as well as resistance against Aeromonas hydrophila. Four diets were prepared including control diet and three diets supplemented with LF (10⁸ CFU/g), FA (100 mg kg^-1) or LF + FA (10⁸ CFU/g + 100 mg kg^-1). After 8 weeks, fish fed LF or/and FA had significantly higher final body weight, weight gain, and specific growth rate when compared to control group (P < 0.05). The feed conversion ratio of fish fed LF or/and FA were noticeably lower than control (P < 0.05). No alterations were observed in case of haematological parameters except red blood cells (RBCs), white blood cells (WBCs), hemoglobin (Hb), and hematocrit (HCT) which were significantly (P < 0.05) increased in fish fed FA or those fed both LF and FA. Also, the WBCs of fish treated with LF or/and FA were noticeably higher than control (P < 0.05). Feeding on LF and FA notably increased the serum total protein and albumin levels (P < 0.05). The serum respiratory burst and lysozyme activity were also enhanced (P < 0.05) in fish fed both LF or/and FA. In addition, evaluation of the serum antioxidant enzymes (catalase, glutathione peroxidase (GPX), and superoxide dismutase (SOD)) activity showed significant (P < 0.05) increase in fish fed FA or both LF and FA as compared to the control. Fish fed LF and FA supplemented diet had highest survival rate after experimental challenge with pathogenic A. hydrophila. The obtained results revealed that LF and/or FA can be used as beneficial feed additive to improve the immune responses and disease resistance in early stages of common carp culture.

Effects of Assam tea extract on growth, skin mucus, serum immunity and disease resistance of Nile tilapia (Oreochromis niloticus) against Streptococcus agalactiae

The present study aimed to assess the possible effects of Assam tea (Camellia sinensis) extract (ATE) on growth performances, immune responses, and disease resistance of Nile tilapia, Oreochromis niloticus against Streptococcus agalactiae. Five levels of ATE were supplemented into the based diet at 0, 1, 2, 4, and 8 g kg^-1 feed of Nile tilapia fingerlings (10.9 ± 0.04 g initial weight) in triplicate. After four and eight weeks of feeding, fish were sampled to determine the effects of the tea supplements upon their growth performance, as well as serum and mucosal immune responses. A disease challenge using S. agalactiae was conducted at the end of the feeding trial. Fish fed ATE revealed significantly improved serum lysozyme, peroxidase, alternative complement (ACH50), phagocytosis, and respiratory burst activities compared to the basal control fed fish (P < 0.05). The mucus lysozyme and peroxidase activities were ameliorated through ATE supplementation in the tilapia diets. Supplementation of ATE significantly (P < 0.05) enhanced final body weight, weight gain, and specific growth rate; while a decreased feed conversion ratio was revealed at 2 g kg^-1 inclusion level, after four and eight weeks. Challenge test showed that the relative percent survival (RSP) of fish in each treatment was 33.33%, 60.00%, 83.33%, 76.68%, and 66.68% in groups fed 0, 1, 2, 4, and 8 g kg^-1, respectively. In summary, diets supplemented with ATE especially at 2 g kg^-1 increased the humoral and mucosal immunity, enhanced growth performance, and offered higher resistance against S. agalactiae infection in Nile tilapia.

Effects of elephant's foot (Elephantopus scaber) extract on growth performance, immune response, and disease resistance of nile tilapia (Oreochromis niloticus) fingerlings

Medicinal plant has been applied as an alternative strategy for antibiotics and chemotherapeutics for controlling the outbreak of diseases in tilapia farming. In this study, five doses of Elephantopus scaber extract (ESE) were added to the basal diet at 0, 2.5, 5, 10, and 20 g kg^-1 feed of Nile tilapia fingerlings (13.92 ± 0.06 g initial weight) in triplicate. After 4- and 8- weeks post-feeding, fish were sampled to determine the effects of the ESE supplemented on fish's growth performance, humoral, and skin mucus immune response. After 8 weeks post-feeding, a challenge test against Streptococcus agalactiae was carried out using 10 fish from each tank. Fish fed ESE showed significantly increased serum lysozyme (SL), serum peroxidase (SP), alternative complement (ACH50), phagocytosis (PI), and respiratory burst (RB) compared to the control group (P < 0.05). The skin mucus lysozyme (SMLA) and skin peroxidase (SMPA) were stimulated in fish fed ESE diets. Dietary inclusion of ESE significantly (P < 0.05) promoted final body weight (FW), weight gain (WG), and specific growth rate (SGR); while a reduction in feed conversion ratio (FCR) was observed in fish fed 5 g kg^-1 ESE, after 8 weeks post-feeding. The challenge study indicated that the relative percent survival (RSP) was 38.10%, 76.19%, 66.67%, and 47.62% in Diet 2, Diet 3, Diet 4, and Diet 5, respectively. Among the supplemented groups, dietary of 5 g kg^-1 ESE showed significantly higher RPS and the highest resistance to S. agalactiae in comparison with other groups. In conclusion, supplementation of ESE (5 g kg^-1) enhanced the humoral and mucosal immunity, promoted growth performance, and improved disease resistance of Nile tilapia against Streptococcus agalactiae.

The protective effect of fish-derived cathelicidins on bacterial infections in zebrafish, Danio rerio

Antibiotic-resistant bacteria are severe threats to aquaculture industry. Boosting and modulating host immune responses has been proved to be an effective strategy to combat with bacterial infections and there is an urgent need for novel immunomodulators. Cathelicidins is an important family of host defense peptides (HDPs) that possess direct antimicrobial activities and potent immunomodulatory properties. Several cathelicidins have been identified and characterized from diverse fish species. Considering the relatively conserved immune systems between different fish species, it is reasonable to speculate that cathelicidins from different fish species possess immunomodulating functions on the other fish species. In the present study, two fish-derived cathelicidins (CATH_BRALE and codCath1) were selected to investigate their protective effect on zebrafish with bacterial infections. They exhibited potent and broad-spectrum antimicrobial activities against the tested aquatic Gram-positive and Gram-negative pathogenic bacteria, with MIC values ranging 2.34-18.75 μg/ml for CATH_BRALE and 2.34-37.5 μg/ml for codCath1. And their antimicrobial effect is so rapid that they killed the bacteria within 60 min. Unlike conventional antibiotics, they kill bacteria by inducing bacterial membrane permeabilization and cell disruption. Besides direct antimicrobial activity, CATH_BRALE and codCath1 exhibited potent immunomodulatory functions by both inhibiting bacteria induced zebrafish pro-inflammatory cytokine gene (TNF-α, IL-1β, and IL-6) expression and stimulating zebrafish chemokine gene IL-8 expression. In vivo challenge test proved that they could significantly decrease the bacterial numbers and enhance the survival rates of zebrafish. All the results above imply the great potential of CATH_BRALE and codCath1 as novel peptide immunomodulators in fish aquaculture industry.

Alginate from Sargassum siliquosum Simultaneously Stimulates Innate Immunity, Upregulates Immune Genes, and Enhances Resistance of Pacific White Shrimp (Litopenaeus vannamei) Against White Spot Syndrome Virus (WSSV)

Although alginate is known as an immunostimulant in shrimp, the comprehensive and simultaneous study on its activity to resolve the relationship of the hematological parameters, upregulation of immune-related gene expression, and resistance to pathogen has not been found in shrimp. We performed experiments to evaluate the effect and mechanism of alginate from S. siliquosum on Pacific white shrimp immune system. Hematological parameters were examined after oral administration of Na alginate in the shrimp. White spot syndrome virus (WSSV) was injected to the shrimp at 14 days, and its copy number was examined quantitatively (qRT-PCR). Immune-related gene expression was evaluated by qRT-PCR. Alginate increased some hematological immune parameters of shrimp. Before WSSV infection, expression levels of Toll and lectin genes were upregulated. The lectin gene were upregulated post infection, and the Toll gene in all the treatments were downregulated, except the shrimps fed with alginate at 6.0 g kg-1 at 48 h post infection (hpi). The shrimps fed with alginate at 6.0 g kg-1 were the most resistant and gave the least WSSV copy number at 48 hpi. Resistance of shrimps fed the alginate-supplemented diets against WSSV was significantly higher compared to that of the control treatment with 56% and 10% of survival rates, respectively. Oral administration of alginate did not affect the growth and total protein plasma. At 120 h post challenge, alginate treatment at 6.0 g kg-1 exhibited the highest survival rate. It is concluded that oral administration of alginate enhanced the innate immunity by upregulating immune-related gene expression. Consequently, the enhancement of the shrimp innate immunity improves the resistance against WSSV infection.

The effect of a multi-strain probiotic on growth performance, non-specific immune response, and intestinal health of juvenile turbot, Scophthalmus maximus L

Probiotic is well known because of its health benefit on the host, including improve growth, treat disease, and enhance immunity. Currently, probiotic has been widely used in aquaculture. However, there is little information about the effect of probiotic on turbot. Therefore, an effort was made to explore the effect of a multi-strain probiotic on growth performance, non-specific immune response, and intestinal health of juvenile turbot, Scophthalmus maximus L. One hundred eighty juvenile turbot (20.04 ± 0.23 g) were randomly divided into three groups (T0, T1, T2), and fed diet were formulated to contain 0%, 1%, and 5% multi-strain probiotic, respectively. Sixty days after the feeding experiment, the growth performance, body composition, enzyme activities, and intestinal microorganism of turbot were analyzed. T2 and T1 showed better growth performance and significant higher (P < 0.05) enzyme activities than T0 (except lysozyme). Moreover, the IV (intestinal villus), IW (intestinal wall), and GC (goblet cell) were well modulated in probiotic treatments. Furthermore, Lactobacillus was found colonized in the intestine of the group fed with 5% multi-strain probiotic. These results suggested adding dietary multi-strain probiotic could positively affect for turbot aquaculture.

Effects of dietary Gelsemium elegans alkaloids on growth performance, immune responses and disease resistance of Megalobrama amblycephala

The present study aim to investigate the effects of dietary Gelsemium elegans alkaloids supplementation in Megalobrama amblycephala. A basal diet supplemented with 0, 5, 10, 20 and 40 mg/kg G. elegans alkaloids were fed to M. amblycephala for 12 weeks. The study indicated that dietary 20 mg/kg and 40 mg/kg G. elegans alkaloids supplementation could significantly improve final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR), feed conversion ratio (FCR) and protein efficiency ratio (PER) (P < 0.05). The 20 mg/kg and 40 mg/kg G. elegans alkaloids groups showed significantly higher whole body and muscle crude protein and crude lipid contents compared to the control group (P < 0.05). The amino acid contents in muscle were also significantly increased in 20 mg/kg and 40 mg/kg groups (P < 0.05). Dietary 40 mg/kg G. elegans alkaloids had a significant effect on the contents of LDH, AST, ALT, ALP, TG, TC, LDL-C, HDL-C, ALB and TP in M. amblycephala (P < 0.05). Fish fed 20 mg/kg and 40 mg/kg dietary G. elegans alkaloids showed significant increase in complement 3, complement 4 and immunoglobulin M contents. The liver antioxidant enzymes (SOD, CAT and T-AOC) and MDA content significantly increased at 20 mg/kg and 40 mg/kg G. elegans alkaloids supplement (P < 0.05). The mRNA levels of immune-related genes IL-1β, IL8, TNF-α and IFN-α were significantly up-regulated, whereas TGF-β and IL10 genes were significantly down-regulated in the liver, spleen and head kidney of fish fed dietary supplementation with 20 mg/kg and 40 mg/kg G. elegans alkaloids. After challenge with Aeromonas hydrophila, significant higher survival rate was observed at 20 mg/kg and 40 mg/kg G. elegans alkaloids supplement (P < 0.05). Therefore, these results indicated that M. amblycephala fed a diet supplemented with 20 mg/kg and 40 mg/kg G. elegans alkaloids could significantly promote its growth performance, lipids and amino acids deposition, immune ability and resistance to Aeromonas hydrophila.

Dietary supplementation of Streptococcus faecalis benefits the feed utilization, antioxidant capability, innate immunity, and disease resistance of blunt snout bream (Megalobrama amblycephala)

This study aimed to investigate the effects of Streptococcus faecalis on the growth performance, intestinal histology, antioxidant capability, innate immunity, and disease resistance of blunt snout bream Megalobrama amblycephala. Fish were fed five experimental diets containing 0 (SF0, control), 1 × 10⁵ (SF1), 1 × 10⁶ (SF2), 1 × 10⁷ (SF3), and 1 × 10⁸ cfu/g (SF4) of Streptococcus faecalis, respectively, for 10 weeks. After the feeding trial, fish were challenged by Aeromonas hydrophila with the cumulative mortality recorded during a period of 96 h. The results showed that WG and FI of fish both showed no significant difference (P > 0.05) among all the treatments. However, the FCR was significantly (P < 0.05) affected by Streptococcus faecalis levels with the lowest value observed in the SF2 group, whereas the opposite was true for intestinal microvillus length (P < 0.05). Dietary supplementation of 1 × 10⁶ cfu/g Streptococcus faecalis significantly (P < 0.05) increased the hepatic activities of SOD, CAT, and GPx; plasma activities of LZM, MPO, ACP, and AKP; and the levels of C3, C4, and IgM of fish, compared with the control group. Similar results were also observed in the tissue expressions of Leap-I, Leap-II, muc2, and muc5b (P < 0.05), whereas the opposite was true for liver MDA contents and plasma NO levels (P < 0.05). At 96 h after challenge, the cumulative mortality of the control was significantly (P < 0.05) higher than that of the SF2 group, but it showed no statistical difference (P > 0.05) with that of the other treatments. These results indicated that dietary supplementation of 1 × 10⁶ cfu/g Streptococcus faecalis could not only improve the feed utilization of blunt snout bream but also enhance its antioxidant capability, innate immunity, and disease resistance.