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Effects of dietary ??-1, 3 glucan on innate immune response of large yellow croaker, Pseudosciaena crocea
Abstract
The present study was conducted to investigate the effects of dietary beta-1, 3 glucan on the innate immune response and protection against Vibrio harveyi infection in large yellow croaker, Pseudosciaena crocea. A basal diet was supplemented with 0% (control), 0.09% (low) and 0.18% (high) beta-1, 3 glucan to formulate three experimental diets. Each diet was randomly allocated to triplicate groups of fish in floating sea cages (1.5 x 1.5 x 2.0m), and each cage was stocked with 100 fish (initial average weight 9.75+/-0.35 g). Fish were fed twice daily (05:00 and 17:00) to apparent satiation for 8 weeks. The results of 8 weeks feeding trial showed that low glucan supplementation (0.09%) significantly enhanced fish growth, whereas high supplementation (0.18%) did not. The serum lysozyme activity was significantly increased with the increase of dietary glucan (P < 0.05), and fish fed the diet with high glucan had significantly higher lysozyme activity compared with low glucan. There were no significant differences in alternative complement pathway (ACP) activity between fish fed diets with and without supplementation of glucan. The phagocytosis percentage (PP) and respiratory burst activity in fish fed the diet with 0.09% glucan were significantly higher than those in fish fed with the control diet (P < 0.05), but both immunological parameters significantly decreased in fish fed the diet with high supplementation compared with low supplementation and no significant difference was observed between the control and high supplementation groups. The challenge experiment showed that fish fed the diet with low glucan had significantly lower cumulative mortality compared with the control and high glucan groups (P < 0.05), but no significant difference was observed between the control and high supplementation groups. These results suggested that low glucan could enhance growth and innate immunity of large yellow croaker with an 8-week oral administration, but higher supplementation did not influence growth, or further improve immunity of large yellow croaker.
... In recent years, there has been a growing interest in determining the effects produced by prebiotic supplements in global fish aquaculture. The main prebiotics used include inulin [47,[49][50][51][52][53][56][57][58]61], β-glucans [30][31][32]34,36,37,40,69], FOS [50,61,70], MOS [52,61,65,69,70], GOS [43,61,[69][70][71], XOS [68,70], AXOS [29], IMO [45], and GroBiotic ® -A (International Ingredient Corporation, Lake City, MN, USA) [69] (Table 1). ...
... Research worldwide shows that the benefits of prebiotics supplements include an improved immune response and nutrient absorption (increased enterocyte number and microvilli size), as well as increased growth and survival rates (Table 1) [30][31][32]35,40,42,44,49,[51][52][53][54][55]59,60,64,65]. Mo et al. [52] studied in the grass carp C. carpio the effect of inulin and mannan-oligosaccharides at concentrations of 0.2 and 2% in the administered diet. ...
Simple Summary
The aquaculture industry is constantly growing and contributes to the food demand of the world’s population, which is already more than 8 billion people. In aquaculture, antibiotics are commonly used to mitigate the appearance of bacterial diseases that cause considerable damage to production. However, this activity induces antibiotic resistance, which risks the health of cultured organisms and consumers. Therefore, alternative supplements such as prebiotics have been emphasized, with their management and due to their multiple beneficial effects, as viable to improve the conditions of production and health of aquatic animals. In developed countries, these supplements are widespread in culture-producing commercial fish, representing a rich protein source worldwide. However, in developing countries such as Mexico, this technology is rare in commercial fish and practically non-existent in endemic fish species. The importance of such supplements for use in the small- and large-scale aquaculture of fish in developing countries should be underscored as relevant for their application in both commercial and endemic fish cultivated in developing countries.
Abstract
Continued human population growth has resulted in increased demand for products, including those derived from aquaculture. The main challenge in aquaculture is producing more every year. In recent years, environmentally friendly supplements that provide the necessary pathways for optimal production have been emphasized. One of them is prebiotics, selectively utilized substrates by host microorganisms conferring a health benefit. Interest in applying prebiotics in global fish farming has increased in recent years as it has been shown to improve growth, boost the immune system, resist stress conditions, and cause the modulation of digestive enzymes. These effects reflect reduced production and disease costs. However, in Latin American countries such as Mexico, large-scale use of these food supplements is needed as a sustainable alternative to improve fish production. This paper gives a review of the current advances obtained with the application of prebiotics in commercially farmed fish worldwide, mentions the prebiotics to use in the aquaculture industry, and updates the status of studies about the used prebiotics in global commercial fish cultivated in Mexico, as well as freshwater and marine endemic fish in this country. Also, the limitations of prebiotics application in terms of their use and legislation are analyzed.
... Cell wall of yeast ( ) is rich in bioactive components and immunostimulating compounds such as nucleic acids, -glucan and MOS, which are commonly used additives in aquaculture. The dietary impacts of MOS and beta-glucan have been reported in aquaculture species such as snapper, (Cook ., 2003); Rohu, (Misra ., 2006); large yellow croaker, (Ai ., 2007);Nile tilapia, (Sado ., 2008); gilthead seabream, (Dimitroglou , 2010); channel catfish, (Duncan and Klesius, 1996;Peterson ., 2012); Pacu, (Sado ., 2014); Rainbow trout, (Denji et al., 2015); Sea bass, L. (Salem ., 2016) and Asian seabass, (Ali ., 2017). However, there is insufficient data on the dietary effects of MOS and -glucan on African catfish ( ) except possibly for a study conducted over a decade ago in which African catfish ( ) were fed commercial diets supplemented with MOS (Genç ., 2006) and-glucan (Yoshida ., 1995). ...
... varied inclusion levels. The observed increase in growth was partly attributed to the ability of MOS to promote the gut microflora (mainly the beneficial lactic acid bacteria) and subsequent production of extracellular enzymes by the gut microflora (Andrews ., 2009) which in turn enhanced nutrient digestion. Similarly, Cook . (2003), Misra . (2006) and Ai . (2007 reported improvement in growth performance of snapper ( ), , and large yellow croaker ( ) respectively when fed diets supplemented with -glucan. Since the growth capacity of fish species is conditioned by several factors, the variations and contradictory effects of dietary MOS and -glucan on the growth of fish species could be due to th ...
The effects of dietary mannaoligosaccharides (MOS) and β-glucan on the production performance of African catfish, Clarias gariepinus, was examined in this study. Three (3) trial diets were produced viz-a-vis., Control (basal diet, BD), MOS (BD + 0.2% MOS) and β-glucan (BD +0.02% β-glucan) and fed to catfish (11.77±0.05 g fish-1) for 63 days. Nine circular tanks were distinctly assigned into 3 dietary groups in triplicate, stocked with 100 fish per tank (85 L), and fed twice daily (8:00 - 9:00h and 17:00 - 18:00h). The results indicated that there was no significant difference (p>0.05) in the mean final body weight, specific growth rates, feed conversion and protein efficiency ratios, and survivals among the various treatments groups. Similarly, somatic indices (condition factors, hepatosomatic indices, and viscerosomatic indices) measured were not significantly different (p>0.05) across the experimental groups. However, the haematological parameters such as packed cell volume, haemoglobin as well as the erythrocyte and leucocyte counts were significantly (p<0.05) lower in the catfish fed MOS diet. It could be concluded herewith that dietary supplementation of MOS and β-glucan do not have a deleterious effect on African catfish production. Further study is however warranted to establish dose-response effect of MOS and β-glucan on innate immunity of African catfish (C. gariepinus).
... It was reported that dietary 50 g/kg of AMP was the suitable dosage for L. vannamei in the study of Wu [7], while dietary 1 g/kg of AMP was considered a suitable dosage for Lates calcarifer in the study of Yu et al. [22]. Except the experimental animal was different, the immune fatigue caused by long-term or high dosage intake of polysaccharide, and polysaccharide characteristics are also potential vital reasons [22,38]. In addition, more studies have been conducted on the improvement in lipid metabolism by AMP in terrestrial animals but less on aquatic animals [30,31]. ...
... It is well known that oligosaccharide is the constituent unit of polysaccharide, and the immune stimulation effect of polysaccharide is closely related to the constituent of oligosaccharide. Nevertheless, dietary intake of oligosaccharide in the long term would induce immune fatigue in aquatic animals [38,63]. Consequently, long-term or high-level polysaccharide intake may also lead to immune fatigue in aquatic animals. ...
This experiment investigated the effects of Astragalus membranaceus polysaccharides (AMP) on growth, physiological and biochemical parameters, and the expression of lipid metabolism-related genes in spotted sea bass, Lateolabrax maculatus. A total of 450 spotted sea bass ( 10.44 ± 0.09 g) were divided into six groups and were given diets with different levels of AMP (0, 0.2, 0.4, 0.6, 0.8, and 1.0 g/kg) for 28 days, respectively. Results indicated that dietary intake of AMP significantly improved fish weight gain, specific growth rate, feed conversion, and trypsin activity. Meanwhile, fish fed with AMP manifested significantly higher serum total antioxidant capacity and activity of hepatic superoxide dismutase, catalase, and lysozyme. Lower triglyceride and total cholesterol were noted in fish fed with AMP ( P < 0.05 ). Moreover, hepatic ACC1 and ACC2 were downregulated by dietary intake of AMP, and PPAR-α, CPT1, and HSL were upregulated accordingly ( P < 0.05 ). Parameters with significant difference were analyzed by quadratic regression analysis, and results showed that 0.6881 g/kg of AMP is the optimal dosage for spotted sea bass in size ( 10.44 ± 0.09 g). In conclusion, dietary intake of AMP can improve the growth, physiological status, and lipid metabolism of spotted sea bass, thereby indicating its promise as a potential dietary supplement.
... However, the results of studies on prolonged administration of immunostimulants are often contradictory (2,14,20). Our experiment suggests that the provision of all tested prebiotics to vimba for 55 days weakened innate cellular immunity. ...
... Furthermore, Rodrigues et al. (30) reported that the negative effect of β-glucans on the immune system of fish could only be observed when high doses of these compounds (>0.1%) were added to the diet. In the experiment carried out by Ai et al. (2), dietary supplementation with a 0.18% addition of β-glucan caused a significant decrease in the percentage of phagocytosis and RBA in a large yellow croaker (Larimichthys crocea). These researchers demonstrated that the dose of glucan was the key parameter to be considered when supplementing the fish's diet for a longer period, because excessively high doses of glucan could lead to the exhaustion of the immune cells and cause immunosuppression. ...
Introduction
The experiment was set to determine the effects of long-term (55-day) use of three commercial prebiotics including Saccharomyces cerevisiae –derived β-glucans and one including inulin on juvenile vimba (Vimba vimba) reared intensively under controlled conditions.
Material and Methods
Six-month-old fish were fed commercial feed (Control group, n = 90), or the same feed supplemented with 0.02% Leiber Beta-S (BS group, n = 90), 0.20% Biolex MB40 (MB group, n = 90), 0.30% CeFi (CE group, n = 90) or 1.00% inulin Orafti GR (IN group, n = 90) for 55 days.
Results
In the BS group, the final growth parameters were significantly lower than in the Control group, while the feed conversion ratio was significantly higher. No significant differences were found between any other group and the Control group in the respective parameters. The respiratory burst activity of the head-kidney phagocytes was significantly lower in all fish groups fed the prebiotic-supplemented diets compared to the Control group. The proliferative response of the head-kidney lymphocytes stimulated by concanavalin A was lower in the BS group than in the Control group, while in other groups this response was not affected. No significant differences were found in histopathological analyses of the digestive tract, liver or pancreas.
Conclusion
The long-term supplementation of fish diets with prebiotics can negatively influence the growth, feed conversion, nonspecific cellular resistance and proliferative activity of the T lymphocytes of vimba juveniles.
... Moreover, the mode of action of DHA is decreasing inflammasome stimulation by enhancing autophagy and thus reducing IL-1β secretion [77]. Nutritional immunology is a new approach to disease prevention in aquaculture via using nutrients to overcome drug residues and resistance and vaccination program difficulties [78,79]. Previous findings described n-3 PUFA as a crucial nutrient that regulates the immune system of fish in response to pathogen invasion [15,80,81], but there is no information describing the efficacy of omega-3NPs against the invasion of Aeromonas hydrophila. ...
... Additionally, Dietary n-3 unsaturated fatty inhibits the inflammatory response of hybrid grouper and provides protection against Vibrio harveyi [58]. Moreover, higher levels of EPA and DHA could inhibit bacterial growth and boost the secretion of anti-inflammatory cytokines, in this manner protecting zebrafish from V. vulnificus disease [78]. The antibacterial effect of omega-3 FAs was explained by their anti-virulence properties, which change cell membrane hydrophobicity, alter the charge on the cell surface, and change membrane integrity, which leads to electron outflow and subsequent cell death [79]. ...
... It is well known that β-glucan supplementation might improve immunological responses of several species of aquatic creatures such as Oncorhynchus mykiss (11), Trachinotus ovatus (12), Cyprinus carpio (13), Lutjanus peru (14) and Litopenaeus vannamei (15). Likewise, previous reports investigated that the inclusion β-glucan within fish feed could stimulate the performance of some fish species such as Cyprinus carpio (16), Pseudosciaena crocea (17), Oncorhynchus mykiss (18) and Apostichopus japonicas (19). In contrast, some studies have found no significant influence of β-glucan dietary administration on the performance of Oreochromis niloticus (20,21) and Dicentrarchus labrax (22). ...
... The gene findings showed that fish fed BG/BC had higher levels of interleukin-1 beta (IL-Iβ) and interleukin-8 (IL-8). The activation of the IL-8 and IL-Iβ genes in response to BG and BC supplemented diets verified the synergistic protective potential function of these mixtures in attracting and activating neutrophils in inflammatory regions and promoting the immune system response function and overall health status of fish (17,93). ...
A 14-week feeding study was conducted to assess the effects of feed supplementation with prebiotics β-glucan (BG group) and/or probiotics Bacillus coagulans (BC group) on O. niloticus growth performance, body analysis, intestinal structure, immunological response, and antioxidant status. The fish were equally divided into six groups, as follows: the fish group fed an un-supplemented diet served as a control group; the other fish groups were fed supplemented diets with 0.1 g β-glucan kg⁻¹; 1 g Bacillus coagulans kg⁻¹; 2 g B. coagulans kg⁻¹; 0.1 g β-glucan combined with 1 g B. coagulans kg⁻¹; 0.1 g β-glucan combined with 2 g B. coagulans kg⁻¹. The findings revealed that supplementing B. coagulans and the β-glucan mixture improved growth performance and feed efficiency parameters (RGR and SGR) more than the other groups. The fish flesh analysis revealed increased crude protein and dry matter content and lower lipid and ash levels in the BG and BC supplemented groups than in the Control group. On the other hand, β-glucan and B. coagulans supplementation significantly boosted antioxidant activity and immunological responses in serum as determined by CAT, MDA, lysozyme, and phagocytic activity. Dietary β-glucan and B. coagulans supplementation remarkedly enhanced anterior intestine villus histomorphometry characteristics. Furthermore, B. coagulans, alone or in combination with β-glucan, could reduce HSP70 and IL-1β gene expression while increasing IL-8 and GH gene expression. According to the findings, B. coagulans and/or BG increased growth performance by increasing gut health and morphology. Furthermore, β-glucan and B. coagulans supplementation enhanced Tilapia's body composition, immunological responses, and antioxidant status.
... Moreover, the mode of action of DHA is decreasing inflammasome stimulation by enhancing autophagy and thus reducing IL-1β secretion [77]. Nutritional immunology is a new approach to disease prevention in aquaculture via using nutrients to overcome drug residues and resistance and vaccination program difficulties [78,79]. Previous findings described n-3 PUFA as a crucial nutrient that regulates the immune system of fish in response to pathogen invasion [15,80,81], but there is no information describing the efficacy of omega-3NPs against the invasion of Aeromonas hydrophila. ...
... Additionally, Dietary n-3 unsaturated fatty inhibits the inflammatory response of hybrid grouper and provides protection against Vibrio harveyi [58]. Moreover, higher levels of EPA and DHA could inhibit bacterial growth and boost the secretion of anti-inflammatory cytokines, in this manner protecting zebrafish from V. vulnificus disease [78]. The antibacterial effect of omega-3 FAs was explained by their anti-virulence properties, which change cell membrane hydrophobicity, alter the charge on the cell surface, and change membrane integrity, which leads to electron outflow and subsequent cell death [79]. ...
In modern aquaculture, enriching Nile tilapia’s diet with omega-3 poly-unsaturated fatty
acids (PUFAs) not only plays an important role in its general health but also fortifies its fillet with
omega-3-PUFAs. However, the major challenge affecting their delivery is their high instability due to
oxidative deterioration. Thus, the prospective incorporation of omega-3-PUFAs into nanocarriers
can enhance their stability and bioactivity. In this regard, the effect of reformulated omega-3-NPs
was investigated on Nile tilapia’s performance, flesh antioxidant stability, immunity, and disease
resistance. Four fish groups supplemented with omega-3-PUFAs-loaded nanoparticles (omega-
3 NPs) at levels of 0, 1, 2, and 3 g/kg diet and at the end of feeding trial fish challenged with
Aeromonas hydrophila. Fish performance (weight gain and feed conversion) was improved in groups
supplemented with omega-3-NPs (2 and 3 g/kg diet). The deposition of omega-3-PUFAs in fish
flesh elevated with increasing dietary omega-3-NPs. Simultaneously the oxidative markers (H2O2,
MDA, and reactive oxygen species) in fish flesh were reduced, especially with higher omega-3-NPs.
Post-challenge, downregulation of IL-1�, IL-6, IL-8, TNF-�, and caspase-1 were noticed after dietary
supplementation of omega-3-NPs. Moreover, mRNA expression of autophagy-related genes was
upregulated while the mTOR gene was downregulated with higher omega-3 NPs levels. Lower
expression of A. hydrophila ahyI and ahyR genes were detected with omega-3 NPs supplementation.
In conclusion, omega-3-NPs application can fortify tilapia flesh with omega-3-PUFAs and augment
its performance, immunity, and disease resistance against Aeromonas hydrophila.
... Moreover, the mode of action of DHA is decreasing inflammasome stimulation by enhancing autophagy and thus reducing IL-1β secretion [77]. Nutritional immunology is a new approach to disease prevention in aquaculture via using nutrients to overcome drug residues and resistance and vaccination program difficulties [78,79]. Previous findings described n-3 PUFA as a crucial nutrient that regulates the immune system of fish in response to pathogen invasion [15,80,81], but there is no information describing the efficacy of omega-3NPs against the invasion of Aeromonas hydrophila. ...
... Additionally, Dietary n-3 unsaturated fatty inhibits the inflammatory response of hybrid grouper and provides protection against Vibrio harveyi [58]. Moreover, higher levels of EPA and DHA could inhibit bacterial growth and boost the secretion of anti-inflammatory cytokines, in this manner protecting zebrafish from V. vulnificus disease [78]. The antibacterial effect of omega-3 FAs was explained by their anti-virulence properties, which change cell membrane hydrophobicity, alter the charge on the cell surface, and change membrane integrity, which leads to electron outflow and subsequent cell death [79]. ...
In modern aquaculture, enriching Nile tilapia’s diet with omega-3 poly-unsaturated fatty acids (PUFAs) not only plays an important role in its general health but also fortifies its fillet with omega-3-PUFAs. However, the major challenge affecting their delivery is their high instability due to oxidative deterioration. Thus, the prospective incorporation of omega-3-PUFAs into nanocarriers can enhance their stability and bioactivity. In this regard, the effect of reformulated omega-3-NPs was investigated on Nile tilapia’s performance, flesh antioxidant stability, immunity, and disease resistance. Four fish groups supplemented with omega-3-PUFAs-loaded nanoparticles (omega-3 NPs) at levels of 0, 1, 2, and 3 g/kg diet and at the end of feeding trial fish challenged with Aeromonas hydrophila. Fish performance (weight gain and feed conversion) was improved in groups supplemented with omega-3-NPs (2 and 3 g/kg diet). The deposition of omega-3-PUFAs in fish flesh elevated with increasing dietary omega-3-NPs. Simultaneously the oxidative markers (H2O2, MDA, and reactive oxygen species) in fish flesh were reduced, especially with higher omega-3-NPs. Post-challenge, downregulation of IL-1β, IL-6, IL-8, TNF-α, and caspase-1 were noticed after dietary supplementation of omega-3-NPs. Moreover, mRNA expression of autophagy-related genes was upregulated while the mTOR gene was downregulated with higher omega-3 NPs levels. Lower expression of A. hydrophila ahyI and ahyR genes were detected with omega-3 NPs supplementation. In conclusion, omega-3-NPs application can fortify tilapia flesh with omega-3-PUFAs and augment its performance, immunity, and disease resistance against Aeromonas hydrophila.
... Studies where BGs were orally administered to fish not only showed immunostimulatory effects but in some cases, improved growth performance [23,24,41,42]. Dawood et al. [43] showed that supplementing red seabream diets up to 0.1% (g/Kg feed) with a commercial BG product (85% purity) for 8 weeks improved final body weight and growth performance as well as lysozyme activity and higher tolerance against a low-salinity stress test when compared with a BG-free fed group. ...
... Authors reported increased complement system activity but no effects on serum lysozyme and blood leukocytes respiratory burst. Still, previous studies in fish revealed a tendency of BGs oral administration to stimulate or modulate innate immune parameters [21,22,42,44,51,52]. ...
This work aimed to evaluate the effects of dietary supplementation with β-glucans extracted from yeast (Saccharomyces cerevisiae) and microalga (Phaeodactylum tricornutum) on gene expression, oxidative stress biomarkers and plasma immune parameters in gilthead seabream (Sparus aurata) juveniles. A practical commercial diet was used as the control (CTRL), and three others based on CTRL were further supplemented with different β-glucan extracts. One was derived from S. cerevisiae (diet MG) and two different extracts of 21% and 37% P. tricornutum-derived β-glucans (defined as Phaeo21 and Phaeo37), to give a final 0.06% β-glucan dietary concentration. Quadruplicate groups of 95 gilthead seabream (initial body weight: 4.1 ± 0.1 g) were fed to satiation three times a day for 8 weeks in a pulse-feeding regimen, with experimental diets intercalated with the CTRL dietary treatment every 2 weeks. After 8 weeks of feeding, all groups showed equal growth performance and no changes were found in plasma innate immune status. Nonetheless, fish groups fed β-glucans supplemented diets showed an improved anti-oxidant status compared to those fed CTRL at both sampling points (i.e., 2 and 8 weeks). The intestinal gene expression analysis highlighted the immunomodulatory role of Phaeo37 diet after 8 weeks, inducing an immune tolerance effect in gilthead seabream intestine, and a general down-regulation of immune-related gene expression. In conclusion, the results suggest that the dietary pulse administration of a P. tricornutum 37% enriched-β-glucans extract might be used as a counter-measure in a context of gut inflammation, due to its immune-tolerant and anti-oxidative effects.
... Despite these beneficial effects of β-glucan on growth and immunity, recent studies demonstrated that overdoses and/or prolonged feeding of β-glucan could lead to either no or negative effects on growth and immune functions [24]. For instance, feeding of low (0.09%) β-glucan for eight weeks was shown to enhance growth in large yellow croaker, whereas high (0.18%) levels did not affect growth or further promote immunity [25]. However, in Indian major carp, Labeo rohita, the beneficial effects of β-glucan could be observed at the lower dietary inclusion levels (0.25 and 0.1%) of beta-glucan [7,26]. ...
... The authors demonstrated that feeding of β-glucan for two weeks did not significantly modulate antiprotease activity of gilthead seabream. On the contrary, β-glucan intake is reported to increase lysozyme and antiprotease activity in different species under normal and healthy conditions [9,25,51]. The dramatic reduction of lysozyme activity in control and 0.5% glucan-fed fish during bacterial challenge indicates a weakened immune function. ...
An eight-week feeding trial was performed to assess the effect of different dietary levels (0, 0.5, 1.0, and 1.5%) of β-glucan (sourced from Saccharomyces cerevisiae) on growth, survival, immunological parameters (immune gene expression, lysozyme, and antiprotease), total antioxidant status, thermal tolerance, and disease resistance of Tor putitora fry. Feeding of moderate doses (0.5 and 1.0%) of β-glucan significantly improved survival but not weight gain percentage as compared to that received unsupplemented control and highest dose (1.5%) of glucan. Supplementation of β-glucan in diets differentially influenced the mRNA expression of cytokine and other immune genes. For instance, transcripts of cytokines such as tnf-α and il-1β were significantly upregulated, while ifn-γ and il-10 were unaffected by β-glucan intake. Also, the relative mRNA expression of tlr-5 and hepcidin1 along with lysozyme and antiprotease activities were remained largely unchanged by dietary glucan administration. In contrast, β-glucan induced mRNA expression of defensin1 and c3 while decreased the transcript level of mhc-1. On the other hand, dietary inclusion of β-glucan markedly improved total antioxidant levels and extended the thermal tolerance limits at both the ends, as shown by increased CTmax and lower CTmin than the control group. After feeding β-glucan for eight weeks, the fish were bath challenged with a bacterial pathogen, Aeromonas salmonicida. The challenge study results revealed that β-glucan intake improved most of the studied immune parameters, resulting in lower mortality. Overall, dietary inclusion of β-glucan (0.5–1.0%) was efficient in improving the immune responses, thermal tolerance, and disease resistance of T. putitora fry.
... They have been observed to play a role in anti-tumor, anti-inflammatory and immunostimulating reactions in aquatic animals like the black tiger shrimp (Penaeus monodon). Dietary beta-1, 3 glucan has been found to enhance innate immunity of the large yellow croaker (Umbrina roncador) and is used as a feed additive for various fish species, including the Nile tilapia and common carp (Cyprinus carpio) (Sahoo & Mukherjee, 2001;Suphantharika et al., 2003;Ai et al., 2007;El-Boshy et al., 2010;Gopalakannan & Arul, 2010;Przybylska-Diaz et al., 2013;Petit & Wiegertjes, 2016;Zhu et al., 2016). ...
... In a recent study, a diet containing 0-0.18% β-glucan could enhance disease resistance in large yellow croakers against Vibrio harveyi infection. Fish fed with 0.09% of β-glucan for eight weeks had increased growth and serum lysozyme activities (Ai et al., 2007). In another study, β-1, 3 glucan could increase immunity against pathogenic Edwardsiella tarda and confer specific immunity to aflatoxin in rohu fish (Labeo rohita Hamilton) (Sahoo & Mukherjee, 2001). ...
... Outcomes of the gene study indicated that groups fed B. coagulans had increased levels of interleukin-1 beta (IL-Iβ) and TNF-α. These genes' activation in response to diets supplemented with B. coagulans confirmed the probiotics' capacity to reduce inflammation by attracting and activating neutrophils in affected areas, improving the response capability of the immune system, and enhancing fish health in general [67]. ...
This study evaluated the effects of Technospore® (Bacillus coagulans) supplementation on intestinal health, immune response, and Oreochromis niloticus (Nile tilapia) growth performance. The experiment divided fish into four groups: a control group fed an unsupplemented diet and three experimental groups receiving diets supplemented with 0.2 g/kg, 0.4 g/kg, and 0.8 g/kg of Technospore®, respectively. Results indicated that Technospore® supplementation significantly enhanced growth rates and feed efficiency in all treated groups, with the most pronounced improvements observed in the group receiving 0.4 g/kg. Furthermore, the study revealed that B. coagulans supplementation markedly boosted serum immune responses, as evidenced by increased phagocytic activity, phagocytic index, and lysozyme levels, following a challenge with Aeromonas hydrophila. Histological analysis showed improved gut morphology, while gene expression analysis indicated upregulation of immune-related genes, including liver IGF-1, GHR, HSP70, IL-1β, and TNF-α, as well as spleen TNF-α and IL-1β and intestinal C-lysozyme and TNF-α, both before and after the bacterial challenge. These findings suggest that dietary inclusion of Technospore® can significantly improve gut health and immune responses in tilapia, potentially serving as an effective prophylactic alternative to antibiotics in aquaculture.
... Sci. 2023, 10, 588 5 of 18 et al. [15] and Ai et al. [16]. Absorbance at 630 nm was measured with a Model Multiskan spectrum (Thermo, Shanghai, China) using KOH/DMSO as a blank. ...
Simple Summary
This study focuses on the Wuchang bream (Megalobrama amblycephala) as the research subject, aiming to investigate the effects of emodin on the total bacterial count of Aeromonas hydrophila and the immune response in various tissues of Wuchang bream following infection. The experimental diets were made by supplementing emodin at 0, 30, 100, and 150 mg kg⁻¹ to a basal (control) diet, respectively, and fed to fish with an initial weight of 50.4 ± 2.35 g. All fish were divided into five experimental groups: uninfected fish fed with basal control diet (negative control, NC), infected fish fed with the diet supplemented with 0 (positive control group, PC), 30 (30), 100 (100), and 150 mg/kg (150) of emodin. Except for the negative control group, all other groups were injected with A. hydrophila at a concentration of 1 × 10⁶ CFU/mL. The experiment was conducted over a period of 14 days, with sampling at various time points. The results of the experiment demonstrated that the total bacterial count of Aeromonas in the kidney, blood, and liver tissues of infected Wuchang bream was significantly affected by the dosage of added emodin and the feeding duration. Additionally, the immune response of Wuchang bream following intraperitoneal infection with A. hydrophila was also significantly influenced by emodin (p < 0.05). In conclusion, the addition of 100 mg/kg of emodin to the diet could enhance the Wuchang bream’s resistance to A. hydrophila infection by reducing the total bacterial count of pathogenic bacteria in tissues, increasing the activity of relevant immune enzymes and promoting the secretion of cytokines. This study provides a theoretical basis for practical production.
Abstract
This experiment aimed to investigate the effects of emodin on the total bacterial count and immune response in various tissues of Wuchang bream infected with A. hydrophila. The experimental diets were made by supplementing emodin at 0, 30, 100, and 150 mg kg⁻¹ to basal (control) diet, respectively, and fed to fish with an initial weight of 50.4 ± 2.35 g. All fish were divided into five experimental groups: uninfected fish fed with basal control diet (negative control, NC), infected fish fed with the diet supplemented with 0 (positive control group, PC), 30 (30), 100 (100), and 150 mg/kg (150) of emodin. The fish were reared for 14 days and sampled at different time points. The results showed that the total bacterial count in the kidney, blood, and liver tissues of Wuchang bream infected with A. hydrophila was significantly affected by the supplementation and feeding time of emodin. At the beginning of the experiment, the difference in total bacterial count among the groups was not significant. On day 1, the total bacterial count in all groups was significantly higher (p < 0.05) than that in the negative control group. On day 4, the total bacterial count in all the emodin groups was significantly reduced, and the best bactericidal effect was observed in the 100 mg kg⁻¹ group. In addition, emodin had a significant effect on the immune response of Wuchang bream after infection with A. hydrophila (p < 0.05). Compared with the other groups, the respiratory burst activity, tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1) content, and white blood cell count (WBC) in the 100 and 150 mg kg⁻¹ groups could be restored to normal levels in the shortest time (p < 0.05). Furthermore, this study also measured the complement alternative pathway activity (ACH50), plasma superoxide dismutase (SOD) activity, and malondialdehyde (MDA) content of the fish. The results showed that supplying 100 mg kg⁻¹ emodin to the diet could significantly (p < 0.05) increase the ACH50 activity of the fish. Compared with the positive control (PC) group, the addition of emodin to the diet can inhibit the decrease in SOD activity and the increase in MDA content in the plasma of infected Wuchang bream. In conclusion, supplying 100 mg kg⁻¹ emodin to the diet can enhance the ability of Wuchang bream to resist A. hydrophila infection by reducing the total bacterial count in tissues, increasing the activity of related immune enzymes, and promoting the secretion of cytokines. This provides a theoretical basis for production practice.
... As the first line of defence against invaders, neutrophils and monocytes generate huge amounts of superoxide anion, as reported by Anderson and Siwicki 23 . A number of different fish species have shown that beta-glucan actually increases superoxide anion generation by macrophages, which is contrary to the current study [34][35][36] . Nevertheless, the experimental designs used in each of these studies were distinctive in the form of beta-glucan, dosage, and administration time. ...
Beta-glucans have immense potential to stimulate immune modulation in fish by being injected intramuscularly, supplemented with feed or immersion routes of administration. We studied how supplementing Labeo rohita’s diet with reishi mushroom powder containing beta-glucan influenced immunological function. A supplemented diet containing 10% reishi mushroom powder was administered for 120 days. Afterwards, analyses were conducted on different immunological parameters such as antioxidants, respiratory burst, reactive oxygen species (ROS), alternative complement activity, and serum immunoglobulin, which resulted significant increases (p < 0.05; p < 0.01) for the reishi mushroom-fed immune primed L. rohita. Additionally, analyzing various hematological parameters such as erythrocytes and leukocytes count were assessed to elucidate the immunomodulatory effects, indicating positive effects of dietary reishi mushroom powder on overall fish health. Furthermore, the bacterial challenge-test with 1.92 × 10⁴ CFU/ml intramuscular dose of Aeromonas veronii showed enhanced disease-defending system as total serum protein and lysozyme activity levels accelerated significantly (p < 0.01). Nevertheless, reishi mushroom powder contained with beta-glucan ameliorated the stress indicating parameters like acetylcholinesterase (AChE), serum-glutamic pyruvic transaminase (SGPT) and serum-glutamic oxaloacetic transaminase (SGOT) enzyme activities results suggested the fish’s physiology was unaffected. Therefore, the results indicated that adding dietary reishi mushroom as a source of beta-glucan could significantly boost the immune responses in Rohu.
... The second assay showed peaks in the expression of C-reactive protein (CRP) at 6 h and 12 h for a subsequent decrease (Pionnier et al. 2013); both authors conclude that β-glucans promote resistance against bacterial infections. Similarly, in Pseudosciaena crocease, an experiment was conducted with diets supplemented with 0%, 0.09%, and 0.18% β-glucan for 4 weeks, where the 0.09% dose showed an increase in the phagocytic burst, respiratory and a lower mortality rate (Ai et al. 2007). ...
The effect of β-glucans 1,3/1,6 from Saccharomyces cerevisiae yeast at different inclusion percentages (0.0, 0.2, 0.4, 0.6, and 0.8%) in the diet for tropical gar (Atractosteus tropicus) larvae was evaluated on growth, digestive enzyme activity and, relative expression of the immune system genes. The bioassay started on the third day after hatching (DAH) and lasted 21 days, using a total of 1500 larvae of 0.055 ± 0.008 g and, a total length of 2.46 ± 0.26 cm. Larviculture was carried out in a recirculation system with 15 tanks of 70 L using a density of 100 organisms per experimental unit. No significant differences in larval growth were observed by the inclusion of β-glucans (p > 0.05). Digestive enzymes showed changes in lipase and trypsin activities, presenting higher values in fish fed 0.6% and 0.8% β-glucans diets compared to the other treatments (p < 0.05). Leucine-aminopeptidase, chymotrypsin, acid phosphatase, and alkaline phosphatase activity showed higher activities in larvae fed with a 0.4% β-glucan diet compared to the control group. The relative expression of intestinal membrane integrity (mucin 2) muc-2, (occludins) occ, (nucleotide-binding oligomerization domain) nod-2, and immune system lys (lysosome) genes showed over-expression in larvae fed the 0.4% β-glucan diet to the rest of the treatments (p < 0.05). The inclusion of β-glucans at 0.4–0.6% in diets for A. tropicus larvae could improve larviculture, as effects on the increase in the activity of several digestive enzymes and the expression of genes of the immune system.
... It is known that functional feed additives and adequate nutrition stimulate fish growth and immune system and potentiate tolerance to different husbandry stressors in aquaculture. Although β-glucan has shown promise in increasing immunity and stress resistance, the results of different studies are highly variable and inconsistent depending upon the type of stressor, fish species, β-glucan source, feeding duration, dose etc. [27]. Nevertheless, little is known about its effect on the expression of water channel proteins/aquaporins and nitric oxide synthase during the ammonia challenge. ...
The study investigated the effects of dietary administration of β-glucan on aquaporins and antioxidative & immune gene expression in endangered golden mahseer, Tor putitora juveniles, exposed to ammonia stress. For that, fish were fed experimental diets having 0 (control/basal), 0.25, 0.5, and 0.75% β-d-glucan for five weeks and then exposed to ammonia (10 mgL-1 total ammonia nitrogen) for 96 h. Administration of β-glucan differentially influenced the mRNA expression of aquaporins, anti-oxidative, and immune genes in ammonia-exposed fish. For instance, the transcript abundance of catalase and glutathione-s-transferase in gill varied significantly among the treatment groups, with the lowest levels in 0.75% β-glucan fed groups. At the same time, their hepatic mRNA expression was similar. Congruently, transcript abundance of inducible nitric oxide synthase considerably decreased in the β-glucan fed ammonia-challenged fish. Conversely, the relative mRNA expression of various immune genes viz., major histocompatibility complex, immunoglobulin light chain, interleukin 1-beta, toll-like receptors (tlr4 and tlr5) and complement component 3 remained largely unchanged in ammonia-exposed mahseer juveniles that were fed with graded levels of β-glucan. On the other hand, a significantly lower transcript level of aquaporins 1a and 3a was noticed in the gill of glucan-fed fish compared to ammonia-exposed fish that received the basal diet. However, branchial aquaporin 3b remained unaltered. Altogether, this study showed that dietary intake of 0.75% β-glucan improved resistance to ammonia stress to a certain degree, probably through activating anti-oxidative system and reducing brachial ammonia uptake.
... Similar to our results, several authors have reported that β-glucans such as yeast glucan obtained from Saccharomyces cerevisiae incorporated in fish feed increase the growth rate of certain species [1,7,18]. The aim of an immunostimulant treatment is to improve immune response and disease resistance but it may also help to counteract the immunosuppressive effects of stress. ...
Dietary β-glucans may be a useful tool to prime the host immune system and increase resistance against invading pathogens as the β-glucans influence the immune response. This prompted us to investigate the effects of dietary yeast β-1,3/1,6-D-glucans supplemented for a 14-day feeding period on liver and cardiac function and the oxidative mechanisms underlying these effects. We assessed relevant lipid peroxidation in the hepatic and cardiac tissue of rainbow trout (Oncorhynchus mykiss), European whitefish (Coregonus lavaretus), and graylings (Thymallus thymallus) after a 14-day period of supplementation with β-glucans. Thirty healthy grayling weighing 34.9 ± 1.9 g, thirty healthy rainbow trout weighing 55.9 ± 2.1 g, and thirty healthy European whitefish weighing 43.3 ± 2.7 g were used in the experiments. The fish were fed with a commercial basal diet at a rate of 1.5% body weight four times a day. After acclimation, the fish were randomly divided into six groups. The groups were fed for 14 days as follows: the control groups comprising grayling (n = 15), rainbow trout (n = 15), and European whitefish (n = 15) received a control basal diet and the β-glucan groups were fed with the Yestimun® food product at a dose of 1% of the basal feed (with 85% of β-1.3/1.6-glucans, Leiber GmbH, Bramsche, Germany). The basal feed was supplemented with 1% of Yestimun® powder (dose: 1 kg per 99 kg, w/w). This insoluble and highly purified preparation contains natural polysaccharides, e.g. β-1,3/1,6-D-glucans derived from Spent Brewers’ Yeast (Saccharomyces cerevisiae). Yeast cell walls typically contain approximately 30% of β-glucans of dry weight. Our results showed that feeding with low doses of β-glucans induced a decrease in TBARS levels in the hepatic and cardiac tissues of rainbow trout, andEuropean whitefish. Similarly, 14 days of feeding graylings with low doses of β-glucans resulted in a decrease in the TBARS levels both in the hepatic and cardiac tissues. This study confirms that dietary β-glucan is beneficial for promoting growth and enhancing antioxidant capacity against oxidative stress in rainbow trout, European whitefish, and graylings. Indeed, we cautiously hypothesized that feeding low β-glucans doses may help to boost antioxidant function, especially by the decrease of biomarkers of lipid peroxidation in the hepatic and cardiac tissues of these fish. Keywords: β-glucans, oxidative stress, lipid peroxidation, Thymallus thymallus, Oncorhynchus mykiss, Coregonus lavaretus
... The bglucan has been widely applied to the aquaculture industry due to its positive impact on the health of aquatic animals (5,6). Numerous studies in b-1,3-glucan have confirmed its property of antiinflammatory, immune-enhancing, and anti-oxidation in aquatic animals such as white shrimp (7)(8)(9), marine swimming crab (Portunus trituberculatus), hybrid striped bass (Morone chrysops × M. saxatilis) (10), and large yellow croaker (Pseudosciaena crocea) (11). Evidence from human hepatocytes suggested that b-1,3-glucan could attenuate inflammation and accumulation of reactive oxygen species (ROS) induced by lipopolysaccharide (12). ...
The phenomenon of intestinal dysfunction is widely observed in white shrimp (Litopenaeus vannamei) culture, and β-1,3-glucan has been confirmed to be beneficial in intestinal health with a lack understanding of its underlying mechanism. Proteobacteria, Firmicutes, and Actinobacteria served as the predominant phyla inhabiting the intestine of white shrimp, whilst a significant variation in their proportion was recorded in shrimp fed with basal and β-1,3-glucan supplementation diets in this study. Dietary supplementation of β-1,3-glucan could dramatically increase the microbial diversity and affect microbial composition, concurrent with a notable reduction in the ratio of opportunistic pathogen Aeromonas, gram-negative microbes, from Gammaproteobacteria compared to the basal diet group. The benefits for microbial diversity and composition by β-1,3-glucan improved the homeostasis of intestinal microbiota through the increase of specialists’ number and inhibition of microbial competition caused by Aeromonas in ecological networks; afterward, the inhibition of Aeromonas by β-1,3-glucan diet dramatically suppressed microbial metabolism related to lipopolysaccharide biosynthesis, followed by a conspicuous decrease in the intestinal inflammatory response. The improvement of intestinal health referred to the elevation in intestinal immune and antioxidant capacity, ultimately contributing to the growth of shrimp fed β-1,3-glucan. These results suggested that β-1,3-glucan supplementation improved the intestinal health of white shrimp through the modulation of intestinal microbiota homeostasis, the suppression of intestinal inflammatory response, and the elevation of immune and antioxidant capacity, and subsequently promoted the growth of white shrimp.
... In this study, the activity of the antimicrobial titer signi cantly increased in sh that did not receive an immunomodulator. Similar results were found by Ai et al. 2007, in a study with diets containing β-glucans for Pseudosciaena crocea, in which the immunological parameters signi cantly decreased in animals treated with a high content of this peptide. These ndings differ from those found by Lin The time/duration factor as well as how the supplementation was administered may be a possible explanation for the results found in this trial, as it lasted 60 days with oral supplementation. ...
The study analyzed the hematoimmunological effects of the joint dietary supplementation of immunomodulators (β-glucans-nucleotides) and different levels of vitamins for Nile tilapia after physical and acute stress. Four treatments with different experimental diets were used: diets with indicated vitamin levels (Vit ind ); Vit ind + 0.5% immunomodulator (Vit ind+Immune ); rations with a high level of vitamins (Vit high ); Vit high + 0.5% immunomodulator (Vit high+Immune ). The experiment included 560 fish (3.0 ± 0.68 g of initial weight and 5.33 ± 0.66 cm of initial length), in 28 tanks and 25 fish/tank, with 7 replicates. After 60 days of supplementation, the animals had a weight of 33.30 ± 7.6 g and a length of 11.97 ± 0.94 cm. The water temperature was set at 20°C and two complete biometrics were performed. Subsequently, the animals were conditioned to two stress factors: physical (I), temperature oscillations: 20ºC to 30ºC/30ºC to 20ºC/20ºC to 30ºC; (II), the same animals were placed in plastic bags with dechlorinated water and shaken for 5 minutes and returned to their respective tanks. For hematoimmunological data, 140 animals were used after stress. Antimicrobial title and total plasma protein were significantly higher in fish that did not receive an immunomodulator. Differently, the binder title increased in fish fed with lower levels of vitamins, while immunoglobulin showed immunomodulatory interaction x level of vitamins. In summary, the inclusion of immunomodulators increased the animals' resistance to physical and acute stress, and improved hematoimmunological parameters, and the high level of vitamins did not modulate immune responses.
... Efforts that have been implemented by cultivators at this time are providing vaccines to prevent disease attacks, giving antibiotics to cure fish infected with pathogens and diseases, and also administering immunostimulants and probiotics to keep the fish's body healthy and can increase the immune response in the body. In addition to those mentioned above, several other efforts can be applied to prevent the entry of disease attacks on fish, such as implementing biosecurity [3,4]. Biosecurity can not only be applied to fish however but biosecurity can also be applied to another aquatic biota such as shrimp. ...
Apart from providing benefits to bread, Saccharomyces cerevisiae can provide benefits to fish by providing it as a probiotic, and immunostimulant can be used as a feed substitute. Saccharomyces cerevisiae can provide benefits to increase growth and disease resistance in cultivated fish, both consumption fish and ornamental fish. Therefore, this journal review will look at which treatments are suitable for utilizing baker's yeast which will later be given to fish. The materials used to review this journal are related reference sources. The method used in this journal review is a systematic, explicit and reproducible method for evaluating and identifying the results of a study that has been produced by previous researchers and then draws a conclusion from the best treatment. From the review results, the best dosage is to use 5 g/kg of baker's yeast.
... Atlantic salmon macrophages possess a receptor that can recognize even very short beta-1,3-linked glucosyl chains extending from yeast cell walls (Engstad and Robertsen 1994). A low dietary concentration of â-1,3 glucan (0.09%) enhanced the growth of and innate immunity in large yellow croaker following eight weeks of oral administration, but higher supplementation did not influence growth or further improve immunity in this species (Ai et al. 2007). The dietary administration of â-glucans potentiated innate immunity and disease resistance in Asian catfish (Kumari and Sahoo 2006). ...
The present study was performed to investigate the effects of dietary yeast β-1,3/1,6-D-glucans supplemented over a 14-day feeding period on liver and cardiac function and the oxidative mechanism underlying these effects. We assessed relevant lipid peroxidation and protein oxidation biomarkers, antioxidant defense indices [superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), total antioxidant capacity (TAC)], and biochemical alterations [activities of aminotransferases (AT), lactate dehydrogenase (LDH), and succinate dehydrogenase (SDH), and levels of lactate (L) and pyruvate (P)] in rainbow trout, European whitefish, and grayling. The fish received a control diet and an experimental diet containing yeast β-1,3/1,6-D-glucans at a dose of 1% in the basal feed for 14 days. The results demonstrated enhancement in the phagocytic activity and phagocytic index in the groups fed β-glucans, compared to the control groups. In the groups fed β-glucans, the oxidative stress parameters such as lipid peroxidation, oxidatively modified proteins, and TAC did not vary significantly. The dietary β-glucans stimulated CAT and GPx activities in hepatic and cardiac tissues in comparison to the control group; however, a reverse trend was observed in the GR activity in these tissues.
... However, when oyster mushroom stalk waste (Pleurotus spp.) has been used in Nile tilapia diets, higher yields have been obtained Table 2 It has been determined that mushrooms of the genus Pleurotus spp. produce β-glucan that at high levels can produce toxicity (Qinghui et al. 2007). Assays of mushroom stalk waste of P. pulmonarius in Nile tilapia have shown that levels up to 20% β-glucan do not induce mortality in feeding trials, and the content of βglucan in our diets did not influence survival. ...
This study aimed to evaluate the effects of mushroom meal supplementation, Pleurotus djamor var. roseus (Pd), on the diet of Nile tilapia (Oreochromis niloticus), on hematological parameters and growth performance for 60 days. Nile tilapia fingerlings (3.23 ± 0.19 g) were fed with three experimental diets based on the mushroom meal in different percentages: diet 0% control (MM0), diet 15% (MM15), diet 20% (MM20) and diet 25% (MM25). Blood samples from the fish of all treatments were collected at the start of the experiment (day 0), 30 and 60 days. The weight and size of the fish were determined every 15 days (0, 15, 30, 45 and 60 days). The results showed a significant dose-dependent increase in the levels of erythrocytes count and leukocytes count. The groups that showed significant differences in the basal value and the final control result were hematocrit, hemoglobin, and lymphocyte. An increase in lymphocytes proportion and a decrease in neutrophils were found, which was related to the immune response of fish fed the diet. The highest levels of leukocytes, lymphocytes, and low neutrophils were presented in the diet with 15 and 20% (P < 0.05). The growth (weight gain and specific growth rate) of fish fed MM15 and MM20 of Pd in the diet was higher than the control group (P > 0.05). Dietary supplementation (15 and 20%) improved hematological and defense blood cells, as well as the growth of tilapia.
... Other studies have found greater survival in animals supplemented with β-glucan without suffering any challenges (Do-Huu et al. 2018). However, in experimental stages in which the fish were challenged, there was usually an influence of the additive on the reduction of negative effects, resulting in lower mortality, either in challenges with pathogens (Ai et al. 2007;Li et al. 2009;Zhu and Wu 2018), due to physical stress, such as differences in water salinity (Do-Huu et al. 2016), or even in challenges due to hypoxia (Souza et al. 2020). Due to the higher survival rates occurring in animals fed with β-glucan after challenging conditions, according to the studies mentioned above, the survival of H. eques fish in the current study remained unchanged during the experimental period due to good quality conditions of water and the absence of stress that would be caused by some physical, chemical, or biological challenges. ...
The effects of β-1,3/1,6-glucan on Hyphessobrycon eques were assessed after 42 days of feeding diets containing 0 (control group given commercial feed), 0.5, 1, or 2 g β-glucan/kg diet. In total, 180 fish, with an initial weight of 0.43 ± 0.03 g, were used. There were 15 fish in each of twelve 42-L aquariums, and there were 3 aquariums of fish for each dietary treatment. The fish were fed until apparent satiety. Performance parameters (final weight, total length, standard length, feed intake, survival rate, weight gain, feed conversion, specific growth rate, and condition factor) and plasma glucose concentration were measured. Histological analysis of the proximal portion of the intestine (width and height of the villi, depth of the crypts, height of the enterocytes, thickness of the muscle layer, and number of goblet cells) was performed. Different levels of the additive did not influence fish performance (for example, final weight: control: 0.63 g, 0.5: 0.60, 1: 0.58, and 2: 0.61). Likewise, there was no influence on the plasma glucose concentration (control: 81.80 mg/dL, 0.5: 75.33, 1: 85.00, and 2: 81.00) and intestinal morphometry of the animals. However, the results showed that 2.0 g/kg of β-1,3/1,6-glucan provided a greater abundance of goblet cells secreting acidic and neutral mucus present in the epithelium (periodic acid-Schiff: 66.67 cells, Alcian blue pH 1.0: 72,67 cells, and Alcian blue pH 2.5: 95.00 cells), showing significant differences when compared to animals in the control group, which may represent better protection of the intestinal epithelium of H. eques.
... Feed additives for cultured aquatic animals have impacts on growth performances, immune response, resistance to diseases and intestinal microbial communities (Kesarcodi-Watson et al., 2008;Merrifield et al., 2010;Ringø et al., 2012;Zokaeifar et al., 2012). In order to improve growth and immunity, several of these additives have commercial potential for the promotion of growth and immune responses in the aquaculture industry (Ai et al., 2007;Choi et al., 2004;Güroy et al., 2014;Lee et al., 2015;NRC, 2011;Shahkar et al., 2015). However, in individual fish species, each dietary additive can produce different levels of response and contribute differently to feed cost. ...
Song-Gang® bio-stone (SGS) is a microporous crystalline
hydrated aluminosilicate which has found various applications because of their
very unique physiochemical characteristics such as ion exchange and
absorptive-desorptive properties. Significant progress has been made in recent
years on applications of these inorganic adsorbents in different industries
including agriculture, aquaculture, water and wastewater treatment. This review
article intends to summarize the published reports on the applications of SGS in
aquaculture industry. SGS application as a feed additive to enhance fish growth
and promote their health and nutritional parameters is the most important
discussed areas. According to the technical data that are discussed in this
review, SGS should be considered as a material with tremendous potential for
application in the aquaculture industry. Considerable amounts of research works
are under way to explore other opportunities for application of SGS to benefit
aquaculture industry.
... In the current research, a signi cant difference was observed in the values of immune parameters, so that the highest levels of IgM, Lysozyme, C3, C4 and ACH50 were observed in treatment with 2% beta-glucan, which shows that adding beta-glucan to the diet improves immunity in trout. Ai et al. (2007) examined the effects of beta-glucan on growth and innate immunity indices in Pseudosciaena crocea ngerlings. The results of their study showed that 0.09% of glucan in the diet has the best effect on immunity, but immunity was not signi cantly different in the control group and 0.18%. ...
This study aimed to investigate the effect of beta-glucan in rainbow trout’s diet on survival, growth performance, hematological, immunity and biochemical parameters. Rainbow trout ( Oncorhynchus mykiss ) with an average weight of 6.35 ± 0.09 were stocked in 30 fiberglass tanks with a volume of 200 liters. Four treatments including: control group (0%), 0.5, 1 and 2% of beta-glucan were considered for 8 weeks. The results showed that the survival and growth performance of rainbow trout in the control group were at the lowest level and showed a significant difference with other treatments. The highest percentage of hematocrit (47.9%), white blood cell count, neutrophil percentage (35.2%) was observed in the treatment with 2% beta-glucan. Also, the highest lysosomal activity (59.7 units’ mL − 1 , IgM (54.7 mg dL − 1 ), C3 and C4 was obtained in 2% beta-glucan treatment. Biochemical parameters showed improvement in treatments fed with 1 and 2% beta-glucan. In general, the present study showed that 2% beta-glucan in the diet of rainbow trout improves growth performance, survival, hematological, immunity and biochemical parameters.
... Oreochromis niloticus) (Abu-Elala et al., 2020; Pilarski et al., 2017), large yellow croaker (Pseudosciaena crocea)(Ai et al., 2007) and tiger ...
Prebiotics, that is, β‐1,3‐glucans are widely used immunostimulants in aquaculture. A 70‐day feeding trial was conducted to investigate the effects of dietary β‐1,3‐glucan on growth performance, feed utilization, antioxidative and immune status of Pacific white shrimp (Litopenaeus vannamei). Six iso‐energetic and iso‐nitrogenous diets with dietary β‐1,3‐glucan levels at 0, 0.04, 0.08. 0.16, 0.32 and 0.64 g kg−1 were fed to six replicates of shrimp (initial mean weight 0.98 ± 0.02 g). The diet with 0.16 g kg−1 β‐1,3‐glucan significantly improved weight gain and decreased feed conversion ratio of the shrimp. Compared with shrimp fed the basal diet, protein efficiency ratio was significantly higher in the β‐1,3‐glucan supplemented groups. Hepatopancreatic amylase activity was significantly increased by the β‐1,3‐glucan supplementation. The 0.16 g kg−1 β‐1,3‐glucan supplemented diet significantly improved serum total superoxide dismutase activity. The lowest hepatopancreatic malondialdehyde content was observed in the 0.64 g kg−1 β‐1,3‐glucan group. This study suggested that appropriate inclusion level of β‐1,3‐glucan can improve the growth performance, feed utilization and improve the antioxidative capacity of Pacific white shrimp, with optimum supplemental level being about 0.156 g kg−1 based on the weight gain in our results.
... The results indicated that vitamin-E was able to enhance the phagocytic activities of L. rohita better when compared to the commercial probiotic or control diets. Likewise, earlier studies on the immunomodulatory effect of dietary vitamin-C [53,54] and immunostimulants [55] on fish showed, more or less, similar effects. In the present study, the A. hydrophila N 10 P challenge caused a significant increase in serum phagocytic activities on 7-dpi, with the maximum in the vitamin-E group. ...
Immunomodulation is one of the useful tools to prevent diseases in aquaculture. In this study, the immunomodulatory effects of vitamin-E (100 mg/kg feed) and commercial probiotic consortia, RhodomaxTM (5 g/kg feed) on the innate immunity of Labeo rohita and their protective effect against Aeromonas hydrophila infection were evaluated and compared. Three groups of fish at 30 numbers/tank were fed with vitamin-E, probiotic and control diets at 3% body weight for 30 days, in triplicate. Following this, the fish of all groups were injected intramuscularly with A. hydrophila N10P at 2.40 × 10⁷ cells/fish. The growth indices like specific growth rate (SGR) and feed conversion ratio (FCR) during the feeding and the non-specific immune responses during the feeding and post-challenge regimen were recorded. The dietary supplementation of vitamin-E and/or commercial probiotics caused significant improvements in the innate immunity of L. rohita compared to control. Nevertheless, the vitamin-E diet offered markedly better results in terms of SGR, FCR, ceruloplasmin, antiprotease, myeloperoxidase and phagocytic activities of L. rohita during the feeding and post-challenge regimen. While the respiratory oxidative burst activity was enhanced in probiotic diet-fed L. rohita only during the feeding regimen. All the immune parameters reached normalcy on day 15 post-injection with A. hydrophila. These findings revealed that supplementation vitamin-E at 100 mg/kg feed may improve the growth indices, prime the non-specific immune responses of L. rohita against A. hydrophila infection and enhance the overall health status than the tested commercial probiotics.
This study aims to test the single and combination effects of dietary vitamin C and β-glucan on golden trevally, Gnathanodon speciosus. The basal diet (D0) was added with vitamin C at 200 mg kg-1 diet (D1), β-glucan at 1.0 g kg-1 diet (D2), and a combination of vitamin C and β-glucan (200 mg vitamin C and 1 g β-glucan per kilogram diet) (D3). The diets were fed the fish for eight weeks. After eight weeks of diet feeding, the growth rate of the fish enhanced significantly with the presence of vitamin C, β-glucan, and the combination of Vitamin C and β-glucan (p < 0.05). The growth rate was significantly higher in a fish-fed diet combined with vitamin C and β-glucan. Survival rates were not significantly different among diet treatments. Muscle protein of fish ranged from 18.36–21.50% among diet treatments. Fish protein content in fish was not influenced by vitamin C, but the protein was higher in fish fed with the β-glucan-added diet and combination the β-glucan and vitamin C-added diet. The current results suggest that a supplemented combination of vitamin C and β-glucan could boost this golden trevally’s growth and body composition at the juvenile stage.
The efficacy of dietary β‐glucan supplementation in golden trevally ( Gnathanodon speciosus ) was evaluated. The fish were fed five different diets supplemented with 0%, 0.05%, 0.10%, 0.20%, and 0.40% β‐glucan for 56 days. After 56 days of culture, survival was the highest when the fish were fed a 0.10% β‐glucan diet. Growth rates were higher in fish fed diets supplemented with all β‐glucan levels. Lymphocytes increased when the fish were fed a diet supplemented with 0.05% β‐glucan, and thrombocytes increased when the fish were fed 0.2% and 0.4% β‐glucan‐supplemented diets. The total aerobic bacteria count in the gut of golden trevally was higher ( p < 0.05) and the total Vibrio counts in the gut of golden trevally were lower ( p < 0.05) when the fish were fed any level of β‐glucan. Flesh protein content was higher and flesh lipid content was lower when fish were fed β‐glucan‐supplemented diets at levels greater than 0.1%. When challenged with Streptococcus iniae , fish fed diets containing 0.10% or 0.20% β‐glucan exhibited the highest survival rates. The current results suggest that supplementation with 0.05 to 0.2% β‐glucan in the diet would be beneficial for the culture of the golden trevally.
The aquaculture industry has developed significantly over the past few decades and has had a substantial impact on the global food supply and marine fisheries resources. However, some problems arise behind the scenes due to excessive intensive farming, such as slow animal growth, frequent disease, and lipid metabolism disorders. These problems have limited the sustainable development of the aquaculture industry, and a continuable solution is required. The use of fungal polysaccharide appears to provide a solution to these problems. Therefore, different supplemented levels of Poria cocos polysaccharide (PCP) (0, 0.4, 0.8, 1.2, 1.6, and 2.0 g/kg, respectively) were fed to spotted sea bass (Lateolabrax maculatus) in similar size (30.28±0.18 g) in current study. The effects of PCP on growth, physiological parameters, and lipid metabolism of spotted sea bass were investigated after a 4-week rearing period. Results showed, fish with PCP intake presented a significantly higher weight gain, specific growth rate, and a significantly lower feed conversion ratio. Significantly higher trypsin activity in liver and intestine were observed in fish with PCP intake. The superoxide dismutase activity in serum and liver of fish with PCP intake were significantly improved, while significantly higher serum total antioxidant capacity and hepatic catalase activity were also observed. However, no significant differences in lysozyme and alkaline phosphatase activity were evident among groups. Fish with PCP intake showed a significantly lower total cholesterol, but no noteworthy change in triglyceride and lipid-metabolism-related genes expression were observed among groups. Results indicated that intake of PCP has a positive effect on growth and antioxidant capacity of spotted sea bass, but seems to have a limited effect on the non-specific immunity and lipid metabolism of spotted sea bass. Based on the regression analysis results, 1.4 g/kg of PCP is the optimal dose for spotted sea bass in size (30.28±0.18 g).
Immunostimulants were widely used in aquafeed due to their multiple important functions, including promoting growth, enhancing non‐specific defence mechanisms and resisting infectious diseases. But the efficiencies of the positive effects of immunostimulants were affected by the duration of the administration and their dose. Short‐term and normal‐dose of immunostimulants promoted the growth and enhance non‐specific immunity of aquatic animals. However, improper use led to several immune disorders, including immune tolerance, immune exhaustion and over‐immunity. The application of two immunostimulant diets in rotation technique and the intermittent use of immune stimulant diets may solve the problems associated with immune disorders, but this application method will be limited by both species and immunostimulants. The occurrence of immune disorders is accompanied by different degrees of gut microbiota dysbiosis, especially significantly up‐regulated the abundance of Proteobacteria. Besides, the gut symbiotic microbiota plays a significant role in host immunity. Consequently, the regulation of gut microbiota may be an effective way to modulate immune disorders caused by improper use of polysaccharide immunostimulants. Regulating the gut microbiota not only solves the negative effects caused by improper use of immunostimulants without restrictions on both species and immunostimulants, but also has the advantage of simplicity and convenience compared to conventional approaches. In summary, this article reviews the possible negative effects caused by improper use of immunostimulants on aquatic animals and compares regular approaches with regulating gut microbiota. And gut microbiota maybe be used as a therapeutic target to improve immune disorders caused by immunostimulants in aquatic animals.
This Study was done in order to evaluate the efficacy of dietary prebiotic yeast (Saccharomyces cerevisiae) cell wall so called (YCW) on growth indices, survival rate and carcass proximate Composition of Acipenser nudiventris fingerlings. 240 cultural ship fingerlings weighted average number (± SD) 7.61 ± 0.01 g for 8 weeks were fed by four different diets including 0, 0.5, 1 and 1.5% YCW in basal diet in form of 4 treatments (following control, 1, 2 and 3). The treatments in twelve 500L fiberglass tank with density of 20 fish in each tank, in the form of 4 treatments with 3 replicates were randomly distributed. At the end of trial, growth indices, survival rate and carcass proximate Composition were determinded. Growth indices such as final weight and length , Condition factor, specific growth rate, feed convertion ratio in all treatments had no statisical significant differences in compared with the control (P>0.05). Hepatosomatic index in treatments fed by YCW was significantly higher than control (P<0.05). Condition factor only in treatment 2 was significantly higher than control. Survival in all treatments was significantly higher than control. Adding YCW in diet couldn't produce statistical significant differences in body composition except moisture. The experiment indicated that YCW didn't influence on growth indices and carcass proximate Composition highly in Acipenser nudiventris.
There is need to reduce usage of antibiotics in favor of prebiotics and phytogenic in aquafeed production. The study evaluated effects of mushroom on growth, gut histology and haematological variables of Clarias gariepinus. Five treatment feeds were made to vary in inclusion of solvent extracted oyster mushrooms, Lentinus sajor-caju as follows: Feed 1, 0%; Feed 2, 4%; Feed 3, 8%; Feed 4, 12% and Feed 5, 16%. The diets were made isonitrogenous (42%) and isolipidic (6.0%). The growth performances, gut histology and haematological profile of the fish were estimated using standard procedures. The essential amino acid (EAA) contents of the mushroom and feeds were analyzed following standard methods. Ingredients were mixed according to proportions, preconditioned and steam pelleted. African catfish of average weight 9.48g were stocked in three replicates 20liter aquarium, at 113.76g/aquarium and fed with the experimental diets for 90days. Results showed that mushroom had good array of EAA especially lysine (7%). The haematobiochemical parameters and growth of the catfish were best at 8% mushroom extract inclusion. Histological sections showed significant increase in length and width of the mucosal fold microvilli as mushroom extract inclusion increased up to 8%. Similarly, red blood cell counts, packed cell volume, hemoglobin and total white blood cell counts of the catfish increased up to 8%. Fish fed Feed 3 had the best specific growth rate (3.00±0.06% day-1), food conversion ratio (1.54±0.01), weight gain, (128.67±0.02g) and protein conversion ratio of 0.3±0.04. Catfish fed with higher than 8% inclusion of mushroom had reduced growth rates, hemato-biochemical and histological parameters. This may be probably due to the high polysaccharides and beta-glucans present in mushroom. Thus, mushroom extracts should be included in catfish feed but not beyond 8%.
The present study aims to explore the effects of dietary fulvic acid (FA) supplementation on the growth performance, digestive enzyme activity and immune response of sea cucumber (Apostichopus japonicas). FA was used to replace 0 (control), 0.1, 0.5 and 1 g cellulose in the basic diet of sea cucumber to formulate four experimental feeds with equivalent nitrogen and energy denoted as F0, F0.1, F0.3 and F1, respectively. No significant differences were observed in the survival rate among all groups (P > 0.05). Results show that the body weight gain rate, specific growth rate, intestinal trypsin, amylase and lipase activities, serum superoxide dismutase, catalase, lysozyme, alkaline and acid phosphatase activities and disease resistance ability against the pathogen, Vibrio splendidus of the sea cucumbers fed with FA-containing diets were significantly higher than those of the control group (P < 0.05). The optimum dose of dietary FA supplementation required for the maximum growth of sea cucumber was 0.54 g/kg. Therefore, dietary FA supplementation to the feed of sea cucumber can significantly improve its growth performance immune response.
The present experiment aimed to analyse the advantages of diets containing 0.05%, 0.10% and 0.20% β-glucan on improving the non-specific immunity response, intestinal Vibrio, total aerobic bacteria, growth and ammonia resistance of pompano, Trachinotus ovatus (28.68 ± 0.23 g). After four weeks of diet feeding, the phagocytic index (PI), phagocytic ratio (PR), and serum lysozyme (SL) of pompano increased when adding β-glucan to their diet. The greatest immune response was observed in the pompano fed the feeds containing 0.05% and 0.10% of β-glucan (P≤0.041). Further, on day 28, the total intestinal bacteria were remarkably rose (P≤0.017) in the pompano those were fed 0.05%–0.10% of β-glucan. However, the Vibrio density and the proportion of Vibrio to the aerobic bacteria were considerably higher in pompano fed the basal (P≤0.045). Also, the pompano that offered dietary β-glucan grew faster than the pompano in control. On days 14 and 28, the β-glucan concentration and fish immune response (PR, PI, SL) correlated positively (r≥ 0.379, P≤0.012). Moreover, on day 28, the total intestinal bacteria showed a profound correlation with the β-glucan level (r=0.312, P=0.012). However, the Vibrio to total bacteria ratio increased as the Vibrio count was corresponded negatively to the β-glucan quantity (r= −0.528, P≤ 0.001). On day 28, the β-glucan addition was highly correlated to the phagocytic index (PI) and intestinal Vibrio. The predicted optimum levels of β-glucan to maximise responses of pompano were 0.121% and 0.122% of β-glucan for PI and intestinal Vibrio, respectively. Moreover, under stress ammonia, the pompano that was given β-glucan diets gained better survival rates and lower relative risks than pompano fed the base diet. In conclusion, the 0.05% to 0.10% β-glucan diet could boost the immune activity, improve intestinal microbes, enhance the tolerance capacity to the ammonia of the cultured pompano, T.ovatus.
Immunopotentiator can activate the immune system, improve the specific and nonspecific immunity of aquatic animals, thereby enhancing the ability to resist infection by pathogenic microorganisms. In recent years, aquaculture diseases have occurred frequently. In order to maintain the health of fish and other aquatic animals, and increase the benefits of aquaculture production, adding growth-promoting immunopotentiator in feed can improve the immune response, promote growth, and reduce the occurrence of diseases. As a substance that effectively controls the occurrence of aquatic animal diseases, it has been widely used in aquaculture. Through its regulation and improvement, the immunity and growth performance of aquatic animals can not only reduce environmental pollution but also ensure human food safety. This article reviewed the research progress of some commonly used immunopotentiator and its biological activities, hoping to provide a valuable reference.KeywordsImmunopotentiatorsImmunityAquatic animals
As an important aquaculture species, improving the immunity of cultured Apostichopus japonicus (A. japonicus) is vital for its health in aquaculture farming. It has been shown that ARA is an important metabolite for A. japonicus infected by Vibrio splendidus. In this study, we aimed to determine the effects of dietary exogenous ARA on healthy sea cucumber cultures, including assessments of immunity, growth, and fatty acid content. Five experimental diets containing 0.01%, 0.29%, 0.46%, 0.70%, and 1.09% ARA were tested. The specific growth rate (SGR) of sea cucumbers did not be significantly affected by exogenous ARA diet groups. The results showed that dietary ARA between 0.49 and 1.09% notably improved the survival rate of sea cucumbers infected by Vibrio splendidus compared with the control group without exogenous ARA. The results also showed the effects of dietary ARA on immune-related genes, enzymes, and oxidation indices; most of the exogenous ARA significantly upregulated the mRNA expression of the genes NFκB, TLR, TLR3, TRAF6, Toll, and MyD88. The activities of ACP, AKP, and lysozyme increased in the 0.49–1.09% ARA groups, especially the dietary 0.49% ARA group. The SOD1 and NOS activities were enhanced by dietary ARA between 0.29 and 0.70%. Compared with the control, the MDA content increased, but the 0.49% ARA-diet group had a lower MDA content. Based on these data, 0.49–0.70% ARA significantly enhanced immunity in cultured A. japonicus. Exogenous 0.49% and 0.70% ARA also elevated the ARA, total PUFA and n-6 PUFA in the body walls. In conclusion, the appropriate exogenous ARA (0.49%–0.70%) in diets could improve immunity and fatty acid content considerably. The results provide basic evidence that ARA can serve a useful immune enhancer for A. japonicus aquaculture.
An eight-week growth trial was conducted to investigate the effects of different dietary levels (0%, 2%, 4%, and 8%) of chrysophyte (Poterioochromonas malhamensis) rich in water-soluble beta-glucan on the growth performance, intestinal health, lipid metabolism, immune responses, and disease resistance of juvenile rainbow trout (Oncorhynchus mykiss). At the end of the feeding trial, no significant difference in weight gain was observed between the non-supplemented control and moderate doses (2% and 4%), but decreased weight gain was found at the highest dose (8%) of P. malhamensis compared with the control group. The survival rate in each group was above 97%, with no significant differences between groups. P. malhamensis supplementation in diets changed bacterial diversity and altered the composition of intestinal microbes. In particular, the abundance of the beneficial bacteria Lactobacillus was increased with moderate doses, and the abundance of the pathogenic bacteria Acinetobacter was enhanced with the highest dose (8%) of P. malhamensis. The mRNA expression levels of tight junction protein genes (e.g., claudin-1, occludin, and tricellulin) were also increased after P. malhamensis supplementation. Meanwhile, P. malhamensis supplementation altered lipid metabolism, including reduced crude lipid content in whole fish and decreased CHO, TG, HDL, and LDL in the serum of the highest dose group. Several free fatty acids, including C14:0, C16:1, and C18:3n3, were also reduced in the liver in the highest dose group. In contrast, P. malhamensis induced mRNA expression of the immune-related genes c3, c4, and c5 and the upregulation of mRNA expression in pro-inflammatory cytokines (IL1β and IL8) in the highest dose group. After the 8-week feeding trial, fish were intraperitoneally injected with a bacterial pathogen, Aeromonas salmonicida. The survival rate increased by 14% in the moderate dose groups and decreased by 11% in the highest dose group compared with the control. In addition, the mRNA expression levels of cytokines and complement system genes were differentially influenced by the challenge test, with an increase of c7 in the moderate dose groups, a decrease of c3 in the highest dose group, a reduction of IL1β in the moderate dose groups, and an upregulation of the anti-inflammatory cytokine IL10 in the moderate dose groups. In conclusion, the dietary inclusion of P. malhamensis at optimum levels (2–4%) efficiently regulated lipid metabolism, improved intestinal health, heightened immune responses, and increased resistance to A. salmonicida in juvenile rainbow trout. P. malhamensis could be a good source of beta-glucan for fish.
Після успішного вильоту пташенят С. familiaris, у гнізді не виявлено решток
корму, проте установлено невелику кількість кліщів. Так, в гнізді знайдено чотири
види: Androlaelaps casalis (Berlese, 1887), Cheletonella caucasica (Volgin, 1955), Acarus
siro (L., 1758) та представника панцирних кліщів Oribatei (Dugès, 1833). З них два види
(A. siro та панцирний кліщ) є сапрофагами та два види (A. casalis та C. caucasica) –
хижаками. За даними літератури, види A. casalis та C. caucasica можна вважати
нідиколами, тобто членистоногими, які є облігатними мешканцями гнізд птахів чи нір
ссавців. Що стосується сапрофагів, то панцирні кліщі можуть потрапляти до гнізда
разом із будівельними матеріалами, бо вони є типовими мешканцями верхнього шару
ґрунту, трав’яної підстилки, мохів тощо. Кліща A. siro називають “борошняний кліщ”,
тому що він живиться зернами злаків (в природі) або різними зернопродуктами (в
місцях зберігання людиною). Хоча основу гнізда С. familiaris складають шматочки
кори дерев та інший матеріал, втім були й злаки, на яких цей кліщ, можливо, потрапив до будівлі птахів.
The effects of different types of non-starch polysaccharides (NSPs) on growth performance, antioxidant activity and intestinal mucosal barrier function of tilapia (Oreochromis niloticus) were evaluated through a 10-week feeding trial. Eleven isonitrogenous (32% crude protein) and isoenergetic (20 MJ/kg) diets were prepared without (control) or with 3.96% arabinoxylan, 0.92% β-glucan, 1.06% mannan, 7.92% pectin, 6.60% cellulose, 1.06% lignin, 1.51% alduronic acid, 13.86% soluble NSPs (sNSP, 3.96% arabinoxylan + 0.92% β-glucan + 1.06% mannan + 7.92% pectin), 9.17% insoluble NSPs (iNSP, 6.60% cellulose + 1.06% lignin + 1.51% alduronic acid) and 23.03% NSP (13.86% sNSP + 9.17% iNSP), respectively. Dietary inclusion of β-glucan or pectin significantly increased weight gain rate (WGR), daily growth coefficient (DGC), hepatic lactase and plasma catalase (CAT) activities. Dietary inclusion of arabinoxylan or mannan significantly decreased hepatic lactase activity,WGR and DGC, significantly increased diamine oxidase (DAO) activity. Dietary inclusion of iNSP or NSP significantly increased WGR, DGC, feed intake, feeding rate, intestinal lipase and lactase activities, hepatic amylase and lactase activities, plasma superoxide dismutase (SOD) and CAT activities, and hepatic SOD activity, significantly reduced pepsin activity and hepatic malondialdehyde (MDA) content. Furthermore, dietary inclusion of sNSP significantly increased feed coefficient ratio, feed intake, pepsin and hepatic trypsin activities, hepatic MDA and plasma DAO contents, and significantly decreased protein efficiency, plasma CAT and hepatic peroxidase activity. These results showed that dietary inclusion of arabinoxylan, mannan or sNSP negatively affected the growth and health of tilapia, while dietary inclusion of β-glucan, pectin or iNSP shown a positive effect; dietary inclusion of iNSP can ameliorate the negative effects produced by sNSP.
Bluefin bream (Sparidentax hasta) fry were immunostimulated using β-glucan (BG) or sodium alginate (SA) or thyroxine sodium (EltroxinTM, T4) at 45 mg, 3 g and 0.01 mg per litre, respectively. The fry were stocked @15 fry per litre in each one-ton tank under a triplicated random design. The tanks were supplied with filtered aerated seawater. The best enhancement in growth and survival (12.91 ± 3.48%) of fry until 14 dps was with T4 treatment while, BG was better than T4 at 21 dps. Immune parameters suggest a superior performance of the immunostimulated fry in their phagocyte response, lysozyme activity, hemagglutinin, and bacterial agglutinin levels. Expression of IgM, IL-1β and Mx genes were upregulated with T4 and BG treatments at all the three samplings. All the treatments were subjected to a bath challenge test using live Proteus vulgaris (10⁷ colony forming unit (CFU ml⁻¹). Survival response was the best in fry stimulated with SA and T4 (92 and 88% respectively) followed by BG-stimulated fry (75%). Vaccine efficacy was also improved in immunostimulated fry (60 dph) when treated with BG and T4 with a memory factor (MF) of 1.87 and 1.25, respectively.
The present study examines host pathogen response in developmental stage of Pterophyllum scalare (angelfish) infected with Aeromonas hydrophila. The study conducted had two different experiments in which the fish were subjected to formalin‐killed Aeromonas hydrophila (FKA) and immunostimulant (β‐glucan) by immersion method. The first experiment had three treatment groups viz., immunized, non‐immunized and control groups and the exposure time ranged between 12 and 32 dph (days posthatch) of larval rearing. The immunized group exhibited a higher fold expression of RAG‐1, RAG‐2 and IgM genes compared with non‐immunized group. The results demonstrated that the vaccination of 12 dph developmental stage prior to bacterial challenge of angelfish makes it more immunocompetent against the pathogens. Moreover, another experiment using β‐glucan was conducted to further examine the development of immune responses in angelfish larvae. The study consisted four treatments containing graded levels of β‐glucan dosages such as 100, 200 and 300 mg/L including a control (0 mg/L) for 20 days from 12 to 32 dph. The higher fold change in mRNA expression of RAG‐1, RAG‐2 and IgM genes was observed in β‐glucan (200 mg/L) treated group as compared to non‐treated and control group. The highest survivability was observed in the immunized group and immunostimulant treated group in the survival analysis. Hence, the present study suggested that either immunization with FKA or β‐glucan (200 mg/L) could be used as a strategy to mitigate the mortality rate and combat infection during the early larval rearing of P. scalare.
This study was conducted to investigate the effects of replacing dietary lipid source FO with a terrestrial lipid blend (LB) on the growth performance, body composition and immunity of juvenile Japanese sea bass when the dietary n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFAs) requirements are met (Lateolabrax japonicus). Two types of experimental diets were formulated with the total FO (the control) or the LB (linseed oil and lard = 1:1). A 56-day feeding trial was conducted in floating cages with three replicates for each treatment. The results indicated that a significantly higher specific growth rate (SGR) and feed efficiency ratio (FER) occurred in fish that were fed the LB diet compared with the control group (p < 0.05). There was no significant difference in the survival rate, body composition or body indicates between the groups (p > 0.05). The respiratory burst, alternative complement pathway activity, lysozyme activity, cytokine genes expression and air exposure test results indicated that the replacement of FO with LB did not significantly affect the nonspecific immunity or stress resistance (p > 0.05). The serum antioxidant enzyme activities and liver tissue antioxidant-related gene expression were significantly higher in the control group than in the other group (p < 0.05). Therefore, the terrestrial lipid blends from linseed and lard (1:1) could be used as an alternative for dietary fish oil without compromising the growth performance, nonspecific immunity and resistance to stress in juvenile Japanese sea bass.
This study aimed to investigate the effect of β-glucan in rainbow trout's diet on survival, growth performance, haematological, immunity and biochemical parameters. Rainbow trout (Oncorhynchus mykiss) with an average weight of 6.33 ± 0.09 were stocked in 30 fibreglass tanks with a volume of 200 L. Four treatments including control group (0%), 0.05%, 0.1% and 0.2% of β-glucan were considered for 8 weeks. The results showed that the survival and growth performance of rainbow trout in the control group were at the lowest level and showed a significant difference (p < 0.05) with other treatments. The highest percentage of haematocrit (47.9%), white blood cell count and neutrophil percentage (35.2%) was observed in the treatment with 0.2% β-glucan. Also, the highest lysosomal activity (59.7 units’ ml−1), IgM (54.7 mg dl−1), C3 and C4 was obtained in 0.2% β-glucan treatment. Biochemical parameters indicated improvement in treatments fed with 0.1 and 0.2% β-glucan. In conclusion, the present study suggested that 0.2% β-glucan in the diet of rainbow trout improves growth performance, survival, haematological, immunity and biochemical parameters.
The use of antibiotics in aquatic feed reduces the incidence of disease and enhances growth performance, although it presents harmful effects, such as development of resistant bacteria and accumulation in the natural environment. A variety of immune stimulants including probiotics, prebiotics, synbiotics, phytobiotics, organic acids, nucleotides, antioxidants, microalgae, yeast and enzymes have been used in the aquaculture industry. In recent decades, much attention has been paid on finding a variety of immunostimulants with lower cost which also affect specific and non-specific immunity and improve fish resistance against a wide range of pathogens. These stimulants strengthen the fish’s immune system by increasing the number of phagocytes, lysozyme activity and level of immunoglobulin. The use of immune stimulants as an effective tool to overcome diseases and strengthen the immune system of farmed species, leads to the promotion of cellular and humoral defense mechanisms and increases resistance to infectious diseases. Among these immunostimulants used in aquaculture, β-glucans are of particular importance. Glucans are complex polysaccharide compounds extracted from the cell wall of yeasts and fungi. These compounds can stimulate fish growth, survival, and immune function. Therefore, this review discusses the role and importance of β-glucan as a food additive in aquaculture and examines the impact of these compounds on the growth performance, immunity and biochemical parameters of farmed species.
Fish peptidoglycan recognition proteins (PGRPs) play important roles in microbial recognition, and bacterial elimination. In the present study, a short-type PGRP from large yellow croaker, LcPGRP5 was cloned and its functions were characterized. LcPGRP5 gene encodes a protein containing conserved PGRP domain, but no signal peptide. Phylogenetic analysis shows that LcPGRP5 is clustered with other short PGRPs identified in other teleosts. LcPGRP5 is constitutively expressed in all tissues examined, with the highest expression being detected in the head kidney. Recombinant LcPGRP5 protein features amidase activity and bactericidal activity. Notably, LcPGRP5 could enhance the phagocytosis of the bacteria by large yellow croaker macrophage, with higher phagocytic capacity being observed in Staphylococcus aureus compared to Escherichia coli. Moreover, overexpression of LcPGRP5 suppresses pro-inflammatory effects elicited by bacterial exposure in the macrophage cell line. Overall, the present results clearly indicate the important roles of LcPGRP5 played in the innate immune responses against bacterial infection.
The present study was to investigate the effect of dietary Tribonema ultriculosum supplementation on growth performance, fillet nutritional quality and immunity of rainbow trout Oncorhynchus mykiss (165.26 ± 0.57 g, mean ± SD). Three diets containing 0 (control), 50 g/kg and 100 g/kg T. ultriculosum (TU) were introduced to triplicate groups of the experimental fish for 90 days. Then, a lipopolysaccharide (LPS) stress experiment was conducted to evaluate the effect of microalgal addition on fish immune response. Compared to the control, microalgal addition significantly increased fish feed intake and growth. Dietary T. ultriculosum supplementation significantly increased the contents of palmitoleic acid, eicosapentaenoic acid (EPA) and docosahexaenoic acid in fillet. The addition of T. ultriculosum significantly increased the activity levels of spleen glutathione peroxidase (before LPS stress) and superoxide dismutase (after LPS stress), and simultaneously decreased the spleen malondialdehyde content compared to the control. In terms of the immune response, fish fed diets containing T. ultriculosum had a higher level of lysozyme activity (before LPS stress), immunoglobulin M content (before and after LPS stress) and hepcidin expression (after LPS stress) compared to the control. These results suggest that T. ultriculosum can be used to increase fish growth, fillet nutritional quality and immunity.
Cultured kuruma prawns were experimentally vaccinated against vibriosis with formalin-killed Vibrio sp. Application of the vaccine by injection, immersion, and spray techniques all reduced mortality of the prawns when they were challenged by Vibrio injection 30 d later. Hemocytes in contact with blood homogenate from immunized prawns produced a chemokinetic factor that activated other hemocytes to migrate through a membrane in a Boyden chamber.
Atlantic salmon head kidney macrophages grown in the presence of particulate yeast β-glucan and bacterial lipopolysaccharide (LPS) showed increased production of lysozyme in the culture supernatants compared to non-treated controls. The increased lysozyme production started at day 3 and was five- to six-fold higher compared to controls at day 6 in culture. β-Glucan showed an approximate linear dose–response curve between 1 and 250 μg ml−1whereas LPS showed a dose–response curve with a well-defined optimum concentration (10 μg ml−1). The increase in lysozyme activity was accompanied by an accumulation of lysozyme gene transcript in the stimulated cells. Recombinant human tumor necrosis factor alpha, known for its ability to stimulate lysozyme in human macrophages and to elevate respiratory burst activity of rainbow trout macrophages, failed to stimulate lysozyme production of Atlantic salmon macrophages. Macrophages isolated from fish suffering from a non-lethal Ichthyobodo necator infection displayed a highly increased ability to produce lysozyme in response to both β-glucan and LPS. As in higher vertebrates, lysozyme production may reflect the differentiation stage of the Atlantic salmon macrophages as well as a direct activation of lysozyme gene transcription by biological response modifiers. The rather late increase in lysozyme production induced by β-glucan and LPS may thus be explained by stimulation of differentiation of the macrophages in culture eventually combined with direct activation of transcription of the lysozyme gene.
Glucans are (1→3)-β-D-glucose polymers that are found in the cell wall of fungi, bacteria and plants. Glucans are known to stim ulate humoral and cell-mediated immunity in humans and animals. In addition to the potent immune stimulatory effects of (1→3)-β-D-glucans, there are a number of toxicological effects associated with exposure to the water-insoluble, microparticulate form of the polymer. Recent investigations have suggested a potential role for (1→3)-β-D-glucans in inhalational toxicity. Specifically, (1→3)-β-D-glucans have been implicated in the symptomatology associated with ‘sick building’ syndrome. The mechanisms by which
(1→3)-β-D-glucans mediate immune stimulation and, perhaps, toxicity are currently under investigation. It is now established that (1→3)-β-D-glucans are recognized by macrophages and, perhaps, neutrophils and natural killer cells via a (1→3)-β-glucan specific receptor. Following receptor binding, glucan modulates macrophage cytokine expression. Here we review the chemistry, immunobiology and toxicity of (1→3)-β-D-glucans and how it may relate to effects caused by inhalation.
Sepsis and sepsis syndrome are significant causes of morbidity and mortality in critically ill surgical patients. Despite technological and therapeutic advances in critical care, sepsis continues to be a pivotal factor in 20 to 50% of deaths in surgical intensive care units. It is clear that alternative approaches to the prevention and/or treatment of sepsis must be found. Preclinical data indicate that macrophage activation with ( I ->3)-D-gIucans will ameliorate sequelae associated with Gram-negative septicaemia. We and others have translated these preclinical observations to the clinical setting and have shown that macrophage activation with (l->3)-D-gIucans will significantly reduce septic morbidity and mortality in trauma and/or high-risk surgical patients. The precise mechanism(s) by which ( I->3)-D-glucans prevent or ameliorate infections have not been fully elucidated. However, recent data suggest the anti-infective efficacy of (l->3)-D-gIucans is attributable, in part, to macrophage activation induced by binding of (l->3)-D-gIucan to a specific receptor followed by modulation of macrophage pro-inflammatory cytokine expression. This article reviews the anti-infective potential of ( l-3)-D-glucans in the prevention of sepsis and septic sequelae. Adis International Limitea1 All rights reserved.
Postlarval tiger shrimp (Penaeus monodon) were immersed in aerated beta-glucan suspensions for 3 h. Enhanced growth was observed in shrimp immersed in glucan at concentrations of 0.5, 1, and 2 mg/ml, but not at 0.25 mg/ml. Shrimp gill tissue became shrunken immediately after immersion in the 2 mg/ml suspension. On days 10, 18, and 43 after beta-glucan treatment, shrimp were immersed in a bacterial suspension containing Vibrio vulnificus cells at a concentration of 5×107 CFU/ml for 12 h at a density of 25 individuals per liter; deaths were recorded for one month following experimental infection. The protective effect of glucan treatment was observed in those shrimp treated with 0.5 and 1 mg/ml glucan, but not in shrimp treated with 0.25 and 2 mg/ml glucan. The protective effect lasted until day 18 following immersion. In vitro, beta-glucan treatment enhanced the phenoloxidase activity in shrimp hemocytes. It therefore appears that beta-glucan is a short-term immunostimulant for shrimp.
The effect of β-1,3-M-Glucan on the production of antibodies reactive with Aeromonas salmonicida antigens i.e. whole bacteria (WB), outer membrane (OM) and lipopolysaccharide (LPS) was studied. The presence of the glucan adjuvant in the Aeromonas vaccine significantly enhanced the production of antibodies to all antigens tested, particularly to those reactive with LPS. Studies of antibody specificities also showed that glucan stimulated the production of protein reactive antibodies. In spite of high antibody levels in all vaccinated groups, results from challenge experiments showed that the salmon were not sufficiently protected against A. salmonicida infection as the relative percent survival did not exceed 54%.
Sepsis and sepsis syndrome are significant causes of morbidity and mortality in critically ill surgical patients. Despite technological and therapeutic advances in critical care, sepsis continues to be a pivotal factor in 20 to 50% of deaths in surgical intensive care units. It is clear that alternative approaches to the prevention and/or treatment of sepsis must be found.
Preclinical data indicate that macrophage activation with (1 →3)-β-D-glucans will ameliorate sequelae associated with Gram-negative septicaemia. We and others have translated these preclinical observations to the clinical setting and have shown that macrophage activation with (1→3)-β-D-glucans will significantly reduce septic morbidity and mortality in trauma and/or high-risk surgical patients. The precise mechanism(s) by which (1→3)-β-D-glucans prevent or ameliorate infections have not been fully elucidated. However, recent data suggest the anti-infective efficacy of (1→3)-β-D-glucans is attributable, in part, to macrophage activation induced by binding of (1→3)-β-D-glucan to a specific receptor followed by modulation of macrophage pro-inflammatory cytokine expression.
This article reviews the anti-infective potential of (1→3)-β-D-glucans in the prevention of sepsis and septic sequelae.
The aim of this study was to determine the influence of dietary glucan and vitamin C, alone and in combination, on the cellular and humoral immune responses of rainbow trout. After 4 weeks of adaptation on a control diet containing glucan at 0ppm and vitamin C at 150ppm, four groups of rainbow trout were fed the experimental diets containing vitamin C at 150 and 1000ppm plus a fixed amount of glucan, or no glucan for 2 weeks. The fish were then switched back to the control diet. Non-specific immunity was investigated at the end of the two-week experimental feeding period, and then again 4 weeks later. Macrophage activities such as oxidative burst and pinocytosis were determined along with complement activation and lysozyme levels. The specific immune response was evaluated as: (1) proliferation of lymphocytes induced by mitogen and (2) the antibody response after vaccination against enteric redmouth disease. Fish were vaccinated at the end of the 2-week experimental feeding period and antibody titres were determined every second week for the 16 following weeks. The results of this trial showed a significant effect of dietary vitamin C but not glucan on the non-specific immune response of rainbow trout such as increased oxidative burst, pino-cytosis and lysozyme activity. Dietary treatments had no effect on alternative pathway of complement activation. A significant enhancing effect of dietary beta-1,3/1,6 yeast glucan was observed on concanavalin A-induced proliferation of lymphocytes and the antibody response after vaccination against enteric redmouth disease. When considering the antibody titres at the peak time, glucan or vitamin C significantly enhanced the response. This was also observed on serum complement levels measured at the same time. Results from this trial helped to establish the beneficial effect of a dietary combination of glucan and vitamin C on the immune response of rainbow trout, as well as to evaluate the specific effect of each substance.
Immunostimulants are valuable for the control of fish diseases and may be useful in fish culture. The immunostimulatory effects of glucan, chitin, lactoferrin and levamisole for fish and shrimp have been reported. Nutritional factors such as Vitamins B and C, growth hormone and prolactin have also been reported to be immunostimulators. These immunostimulants mainly facilitate the function of phagocytic cells and increase their bactericidal activities. Several immunostimulants also stimulate the natural killer cells, complement, lysozyme and antibody responses of fish. The activation of these immunological functions is associated with increased protection against infectious disease. Resistance to bacterial pathogens such as Vibrio anguillarum, V. salmonicida, Aeromonas salmonicida, Yersinia rukeri and Streptococcus spp. and to parasitic infections such as white spot disease can be increased by administration of immunostimulants, but not to intracellular pathogens such as Renibacterium salmoninarum and Pasteurella piscicida. The most effective method of administration of immunostimulants to fish is by injection. Oral and immersion methods have also been reported, but the efficacy of these methods decreases with long-term administration. Overdoses of several immunostimulants induce immunosuppression in fish. The side effects of immunostimulants have not been well-studied. Growth-promoting activity has been noted in fish or shrimp treated with glucan or lactoferrin. Immunostimulants can overcome immune suppression by sex hormones. Thus, the influence of immunostimulants in mature fish should be studied. In conclusion, immunostimulants can reduce the losses caused by disease in aquaculture; however, they may not be effective against all diseases. For the effective use of immunostimulants, the timing, dosages, method of administration and the physiological condition of fish need to be taken into consideration.
Previous studies have shown that intraperitoneal (i.p.) injection of a yeast cell wall glucan into Atlantic slamon, Salmo salar L., resulted in increased resistance to bacterial pathogens and that the glucan enhanced the protective effect of an i.p.-administered furunculosis vaccine in salmon. In the present work, the peritoneal cell responses to yeast glucan, glycogen, Freund's incomplete adjuvant (FIA) and saline were compared. Whereas saline gave no detectable peritoneal cell response, injection of the three other agents resulted in accumulation of macrophages, neutrophils and thrombocytes in the peritoneal cavity 2–22 days later. Glucan and glycogen gave maximum leucocyte responses 2 days after injection, whereas the number of leucocytes after FIA injection showed a continuous increase during the 22-day experimental period. Two days after injection, macrophages dominated in the leucocyte response to yeast glucan, whereas neutrophils dominated in response to glycogen and FIA. At 8 and 22 days post-injection of yeast glucan and FIA, thrombocytes represented the largest fraction of peritoneal cells. Except for an elevated number of neutrophils 3 weeks after injection, i.p. administration of yeast glucan gave no significant change in leucocyte numbers from the head kidney. On the other hand, head kidney macrophages from glucan-treated fish showed an increased ability to kill a virulent strain of Aeromonas salmonicida.
The stimulatory effect of LPS (Vibrio anguillarum), laminaran and sulphated laminaran, aqueous soluble β(1,6)-branched β(l,3)-D-glucan obtained from Laminaria hyperborea, on head kidney macrophages of Atlantic salmon, Salmo salar L., is reported. The macrophages, after stimulation with LPS or laminaran, showed pronounced spreading, membrane ruffling and increased organellc content when examined by light microscopy. LPS stimulation induced enhanced phagocytic and pinocytic activity, higher intraccllular production of superoxide anion, and higher activity of acid phosphatase compared to control cells. Native laminaran stimulated the cells to pinocytose more fluid phase, increase the intracellular production of superoxide anion and to elevate the activity of acid phosphatase. Sulphated laminaran induced higher production of superoxide anion and higher activity of acid phosphatase by macrophages than in control cells.
Intraperitoncal injection of β-l,3 glucan in channel catfish, Ictalurus punctatus Rafinesque, greatly reduces mortality from experimental infection with Edwardsiella ictaluri. Anterior kidney phagocytes from fish receiving glucan had enhanced phagocytic and bactericidal ability. The elevated bactericidal ability of phagocytes was not accompanied by increased production of hydrogen peroxide. Fish injected with glucan responded to subsequent E. ictaluri immunizations with higher serum antibody titres relative to the control catfish. The timing of glucan administration and antigen immunization was also important. These results indicate that β-1,3 glucan potentially could be utilized prophylactically as an immunomodulator in channel catfish.
Juvenile common dentex (Dentex dentex) Sparidae, were fed moist diets over 2 months. The three test groups (triplicate lay out) received diets supplemented every second week with one of the two tested immunostimulants — MakroGard or Vita-Stim, or a diet without supplement (control). All fish were weighed at weekly intervals to (a) obtain data on growth and feed conversion and (b) generate repeatedly a defined stress situation to amplify the possible effects of the immunostimulant treatments on growth, mortality and non-specific defense mechanisms.
Growth and feed conversion were not significantly influenced by the applied immunostimulants during the entire experimental period. Most likely, as a result of the cumulative handling stress, growth decreased considerably during weeks 5 and 6 of the experiment in all three test groups. Fish in five of the nine test tanks developed a protozoan infection, regardless of the immunostimulant applied. However, mortalities related to this disease were markedly reduced in tanks treated with either MacroGard (10%) or VitaStim (15%) compared to the control tank (30%). Mortalities related either to cannibalism, eye damage or other unidentified events were not significantly different between treated and control tanks. At the end of the experiment, general fish health parameter (Haematocrit, Leucocyte number) and parameter of the non-specific immune response (Oxygen radical activity, Lysozyme activity, Total plasma protein) were determined from blood samples. Blood parameter did not clearly reflect the protective effect of the administered immunostimulants.
The activities of lysozyme, alkaline and acid phosphatase, N-acetyl-glucosaminidase and complement (as spontaneous haemolytic activity) were measured in plasma of Atlantic salmon, Salmo salar L., after intraperitoneal injection of a β-1,3 and β-1,6 linked glucan from Saccharomyces cerevisiae. The glucan has previously been shown to induce resistance of Atlantic salmon to several bacterial pathogens. The glucan treatment resulted in increased activities of lysozyme 1–3 weeks and complement 2–4 weeks after injection. The activities of alkaline phosphatase and N-acetyl-glucosaminidase showed a decrease 1 week after injection and then slowly restored to normal levels, whereas acid phosphatase was only slightly altered during the experimental period. These results indicate that the glucan induces a selective increase in lysozyme rather than a general release of lysosomal enzymes. The time intervals of enhanced activities of lysozyme and complement partially overlapped with the time intervals of expected enhanced protection against pathogens. Thus, induction of increased activities of lysozyme and complement may, at least in part, explain the mechanisms by which glucan induces protection against bacterial pathogens in salmon.
An insoluble polysaccharide from the cell wall of Saccharomyces cerevisiae, called M-Glucan, has been shown to enhance the non-specific disease resistance of Atlantic salmon, Salmo salar L., when injected intraperitoneally. M-Glucan consists only of glucose units which presumably are linked through β-1,3 and β-1,6 linkages. Enhanced resistance was demonstrated against Yersinia ruckeri, the causal agent of enteric redmouth disease, against Vibrio anguillarum, the causal agent of classical vibriosis and against Vibrio salmonicida, which causes cold water vibriosis or ‘Hitra-disease’ in salmon. At a dose of 2mg M-Glucan per fish (20g mean weight), maximal resistance developed in the fish 3 weeks after injection. Injection of different glucan doses and challenge one week later with Vibrio anguillarum, showed that 50-200μg glucan per fish resulted in the highest level of resistance. The level of resistance in Atlantic salmon obtained with M-Glucan was strikingly higher than that obtained with another glucan which was prepared from Saccharomyces cerevisiae by a different procedure.
The suitable protein-to-lipid ratio for juvenile large yellow croaker, Pseudosciaena crocea Richardson (initial body weight, 0.57 ± 0.11 g) was determined using practical diets in a 4 × 3 factorial experiment. Four dietary protein levels (34%, 37%, 42% and 47%) and three dietary lipid levels (7.5%, 10.5% and 14.0%) were tested. Each of the 12 diets was fed to triplicate groups of croaker juveniles for 60 days in floating netcages (1.0 × 1.0 × 2.0 m3) in the sea. The effects of dietary treatments on survival, weight gain, feed conversion ratio, protein efficiency ratio, hepatosomatic index and carcass composition of the fish were evaluated. At all three lipid levels, the best growth was always obtained in the fish fed diets of 47% protein. At 34% protein, better growth was observed for the fish fed the diet with 10.5% lipid, whereas at the protein levels above 37% the diets containing 10.5% and/or 14.0% lipid proved better. Based on the results of current experiment, the dietary protein:lipid ratio of 47:10.5 appeared to be suitable for this fish. Feed conversion ratio ranged from 1.40 to 1.98, declining with the increases of both dietary protein and lipid. The carcass lipid was correlated positively to dietary lipid, unlike the carcass protein that was independent of dietary protein. There was no interaction between dietary protein and lipid except for carcass lipid. Further investigations should be conducted to determine the optimal protein-to-lipid ratio for large yellow croaker juveniles using diets containing higher levels of protein and lipid than 47% and 14%, respectively.
Using crude homogenates from the digestive system of pond-cultured Penaeus monodon, carbohydrase activity was demonstrated toward a wide variety of substrates differing in sources and complexity. The largest concentration of this activity was found to be localised within the midgut gland. Multiple pH optima for the hydrolysis of starch suggested the presence of more than one amylase, which was confirmed by partial purification using chromatofocusing. Enzyme characterisation of the amylase activity suggested exohydrolysis in the form of a glucoamylase and possible endohydrolysis in the form of an -amylase. The complexity of the enzyme profile demonstrated in P. monodon is discussed in relation to possible sources of carbohydrate found in natural food items.
The movement of intracellular free calcium([Ca2+]i) and phosphatidyl inositol-1, 4, 5-triphosphate (IP3) was studied in bone cells cultured in a low-calcium environment. The [Ca2+]i was 98.0±10.2(n=6)nM/106 cells for the control group (bone cells cultured in control medium) and 21.3±2.8(n=6)nM/106 cells for the low Ca group (bone cells cultured in low Ca medium). After the addition of exogenous CaCl2 to the calibration solution, [Ca2+]i increased significantly more in the low Ca group than in the control group(p<0.01). The IP3 content/2×106 cells was 12.40 pmoles in the control group and less than 0.19 pmoles in the low Ca group. After the stimulation with phospholipase
C (PLC), the IP3 content in the bone cells increased markedly more in the low Ca group than in the control group. These findings suggest that
a low-calcium environment around cells and organsin vivo may inhibit the intracellular signal tranduction system.
This study investigated the in vitro effects of a commercial β-glucan preparation, EcoActiva™, on the respiratory burst activity of head-kidney macrophages isolated from pink snapper (Pagrus auratus), a marine fish cultured in Australia. Macrophages incubated with EcoActiva™ displayed morphological characteristics of activation, and were stimulated to produce superoxide. Pre-incubation with low levels of EcoActiva™ significantly increased the response to phorbol myristate acetate (PMA) and lipopolysaccharide (LPS), indicating that EcoActiva™ could prime these macrophages. Co-culturing macrophages with both LPS and PMA, or EcoActiva™ and PMA, increased burst activity compared with the response to PMA alone, however, this increase was additive and not synergistic. These results suggest that EcoActiva™ is able to stimulate non-specific immunity in snapper through increased respiratory burst activity of macrophages, an important component of the host defence network.
The influence of traditional Chinese medicine (TCM) formulated from Astragalus Root (Radix astragalin seu Hedysari) and Chinese Angelica Root (Radix angelicae sinensis) at the rate of 5:1 (w/w) on nonspecific immunity including the number of phagocytes, lysozyme and complement activities, and disease resistance to Vibrio alginolyticus in large yellow croaker, Pseudosciaena crocea (Richardson) was determined. Minced fish (surimi) supplemented with 0.5% TCM had no influence on the nonspecific immunity of the fish (P>0.05). On the other hand, the surimi with 1.0% and 1.5% TCM resulted in a significant increase in nitroblue tetrazolium (NBT) positive cells and lysozyme activities (P<0.05) of experimented fish on 20, 25 and 30 days after feeding and led to evident enhancement of complement activities (P<0.05) after 15 days of feeding. The highest survival rates (93.3%) in fish infected with V. alginolyticus were achieved with surimi containing 1.0% and 1.5% TCM, but the cumulative mortalities were 37% and 75% in fish fed with surimi containing 0.5% TCM and TCM-free surimi, respectively. These results indicated that the TCM formula might elevate the function of nonspecific immunity and enhance disease resistance of large yellow croaker.
The in vitro effect of several β-glucans on the respiratory burst of turbot and gilthead seabream phagocytes was examined. Three particulated β-glucans from yeast, Saccharomyces cerevisiae and a particulate glucan from the fungus Schizophyllum commune were used. In some experiments, cells were incubated for 1 or 2 h with a mixture of glucan (0–500 μg ml−1) and nitroblue tetrazolium (NBT). In others, cells were preincubated with glucans for 1, 3 and 6 h and then incubated for 1 h with NBT with or without PMA. Cells from gilthead seabream and turbot responded similarly to glucans, and differences in activity depended mainly on the concentration of glucans, the length of incubation period of cells and glucan, and on the glucan used. Incubation of cells with glucans for 1 h directly induced a respiratory burst which increased with the concentration of glucan. However, after 2 h incubation a decrease in NBT reduction occurred at the highest glucan concentrations. An enhancement of the respiratory burst, which increased with the concentration of glucan, was also seen when cells were preincubated with glucans and then incubated with NBT without PMA. However, when PMA was added to the NBT solution, the highest NBT reduction was found at low glucan concentrations whereas with higher concentrations of glucan the NBT reduction decreased significantly. Thus high concentrations of glucan directly induced respiratory burst and led to exhaustion. Low concentrations of glucan primed the phagocytes to be capable of enhanced production of reactive oxygen species on subsequent activation of the respiratory burst. The former may increase disease susceptibility, the latter increase resistance.
A study was conducted to estimate the optimum requirement of dietary phosphorus for large yellow croaker in floating sea cages (1.0 × 1.0 × 1.5 m). Five practical diets were formulated to contain graded levels (0.30%, 0.55%, 0.69%, 0.91% and 1.16%) of available phosphorus from dietary ingredients and monocalcium phosphate (MCP). Each diet was randomly assigned to triplicate groups of 180 juvenile fish (initial body weight, 1.88 ± 0.02 g). Fish were fed twice daily (5:00 and 17:00) to satiation for 8 weeks. During the experimental period, the water temperature fluctuated from 26.5 to 32.5 °C, salinity from 32‰ to 36‰ and dissolved oxygen was more than 7 mg l− 1. Specific growth rate (SGR) significantly increased with increasing available phosphorus from 0.30% to 0.69% of diet (P < 0.05), and then leveled off. The body composition analysis showed that the whole-body ash and lipid, as well as phosphorus content in the whole body, vertebrae and scales were significantly affected by dietary available phosphorus level (P < 0.05). Broken-line analysis based on SGR indicated the minimum available phosphorus requirement for the optimal growth of large yellow croaker was 0.70%. Based on the phosphorus content in either vertebrae or whole body, the requirements were 0.89% and 0.91%, respectively.
β-glucan at different dietary doses was administered to enhance the immunity, growth and survival against Aeromonas hydrophila and Edwardsiella tarda in Labeo rohita fingerlings. Four different Diets with 0, 100, 250 or 500 mg of β-glucan kg− 1 diet were fed to L. rohita fingerlings for 56 days. Biochemical and haematological parameters such as serum total protein content, albumin content, globulin content, albulin : globulin ratio, glucose content and leucocyte counts as well as cellular immune parameters such as superoxide anion production, phagocytic activities, lymphokine production index and humoral immune parameters such as lysozyme activity, complement activity and serum bactericidal activity in the fish were evaluated at two week intervals. After 56 days, the specific growth rate (SGR) and food conversion ratio (FCR) were calculated and fish were divided into two subgroups under each major treatment group for challenge with A. hydrophila and E. tarda. The mortality (%) and agglutinating antibody titre were recorded on the 28th day after challenge. Immune parameters including the leucocyte count, phagocytic ratio, phagocytic index, lysozyme activity, complement activity and serum bactericidal activity rose to their highest levels on 42 days after feeding with the diet containing 250 mg of β-glucan kg− 1 diet. This dose also resulted in the highest protection in the challenge study. Doses of 250 and 500 mg of β-glucan kg− 1 diet resulted in better SGR and FCR. Thus, administration of 250 mg of β-glucan kg− 1 diet is recommended for enhancement of immunity, growth and survival of L. rohita fingerlings.
Immunostimulant preparations Macrogard®, Candida utilis, Saccharomyces cerevisiae, Evetsel®, Chitosan®, or FinnStim® were mixed into semipurified diets and fed to groups of rainbow trout for 1 week. Fish were bled by non-lethal caudal puncture and blood samples assayed for changes in non-specific cellular immunity and humoral protein levels. In the immunostimulated fish, hematocrit levels and lymphocyte counts remained relatively stable; however, elevations were observed in oxidative radical release, myeloperoxidase activity, phagocytic indexes, and potential killing activities of phagocytic cells including neutrophils. Total plasma protein and total immunoglobulin levels were elevated by the dietary immunostimulants. A challenge with the virulent pathogen that causes furunculosis, Aeromonas salmonicida, showed that the immunostimulated groups of fish were more resistant to the disease, confirming the potential use of these substances in fish culture for the prevention of disease.
To determine the effect of dietary supplementation of A3α-peptidoglycan (A3α-PG), extracted from Bifidobacterium sp. cell wall, on the immune responses of Japanese flounder (Paralichthys olivaceus) and explore a possible influence of doses and administration length, a 40-day feeding trial was conducted to evaluate graded levels (0, 0.5, 1, 2, 4, 8 and 16 g A3α-PG/kg diet) in the diet of juvenile Japanese flounder, followed by a challenge with Vibrio anguillarum by intraperitoneal injection. Growth, serum lysozyme, hemolytic complement activity, blood leucocyte phagocytic activity, respiratory burst, and total serum protein were monitored at intervals of 10, 20, 30 and 40 days.Growth, serum lysozyme, hemolytic complement activity, blood leucocyte phagocytic activity of juvenile Japanese flounder were generally enhanced by dietary supplementation of 1, 2, 4 and 8 g A3α-PG/kg diet and also enhanced immune responses, but not growth. The beneficial influence of A3α-PG on most of the tested immune responses were dose- and/or administration length-dependent except serum lysozyme, which was only stimulated by higher doses (more than 2 g A3α-PG/kg) after 40 days feeding. No significant influence of dietary supplementation of 0.5 g A3α-PG/kg on innate immunity was observed on juvenile fish. The highest dose explored in the present study, 16 g A3α-PG/kg, also failed to show any significant influences, although no obvious pathology was observed. Dietary supplementation of A3α-PG showed protection against V. anguillarum. The present study showed an immunomodulatory effect of dietary supplementation of A3α-PG and the potential use in health management of cultured economic fish species such as Japanese flounder.
Recently, there has been an increasing interest in the potential effect of dietary chromium on the health of fish, particularly with respect to their metabolism and growth. Information as to the role of this mineral on their immune response, is limited however, so the aim of this study was to assess the effects of dietary chromium yeast supplementation on the immune response of rainbow trout (Oncorhynchus mykiss).Juvenile rainbow trout (56 g average weight) were fed three semipurified diets containing different levels of chromium (1540, 2340 and 4110 ppb), obtained by supplementing a basal diet with 800 or 2570 ppb chromium yeast, for 6 weeks. After this, time differences in their immune response were examined.A positive influence was observed on serum lysozyme activity at this time in fish maintained on the high chromium diet. The respiratory burst of head- kidney macrophages was also examined, and statistical differences were found in the level of respiratory burst elicited by macrophages from both groups of fish fed supplemented chromium after 3 and 6 weeks of feeding (absorbance at 3 weeks: 0·118, 0·166, 0·151 and 6 weeks 0·114, 0·168, 0·151 for the 1540, 2340 and 4110 ppb groups). Macrophages of fish receiving diets supplemented with chromium also had a greater ability to phagocytose yeast after 6 weeks than the control fish (40·5, 48 and 48·5% macrophages phagocytic in the 1540, 2340 and 4110 ppb groups, respectively).The results of the study show that chromium yeast is able to modulate the immune response of rainbow trout, and this effect appears to be both dose- and time-dependent.
The non-specific defence (NSD) of vertebrates includes a variety of components such as lysozyme, complement, pentraxins, transferrin, protease-inhibitors, antibacterial peptides, mononuclear and polymorphonuclear phagocytes, natural killer cells and the interferon system. Many of these components have been identified in fish. Although the NSD can be down-regulated by different kinds of stress, it can also be up-regulated by various compounds of microbial or synthetic nature. Several lines of evidence suggest that the NSD has evolved towards recognition of structurally conserved microbial polymers like fungal cell wall β-glucans, bacterial LPS and peptidoglycan, bacterial DNA and viral double-stranded RNA (dsRNA). These components also have the ability to augment the resistance of vertebrates against microbial infections. The macrophage is the key regulator of most of these processes due to its production of various cytokines upon recognition of conserved microbial structures. Fungal β-glucans and peptidoglycan have been shown to enhance the resistance of fish against bacterial infections. Injection of microbial wall polymers into fish appear to result in production of acute phase proteins and activation of macrophages. Ds RNA has been shown to enhance the resistance of fish against infections with viral pathogens which can be explained by induction of type I interferons which in turn induce the production of antiviral proteins. In salmonids dsRNA has been shown to induce the production of Mx proteins which in man and mouse are known to have potent antiviral activity against certain negative-stranded RNA viruses.
The immune system can be influenced by a wide range of factors, including disease, pollutants, hormones and diet. The effects of these factors have been investigated in several flatfish species including turbot Scopthalmus maximus, flounder Platichthys flesus, dab Limanda limanda and sole Solea solea. The studies included diseased fish, the in vitro application of the stress hormone cortisol, the contaminants copper and TBT, and in vivo dietary vitamin E supplements. A range of microscopic and microplate assays to measure immunocompetence has been applied to these species in both in vivo and in vitro laboratory experiments. The results are discussed in relation to current ideas of stress in fish, the regulation of the immune system and the biomarker concept.
Schizophyllan and scleroglucan, which are β-1,3-glucans derived from Schizophyllum commune and Sclerotium glucanicum, were evaluated for their ability to enhance protection against bacterial infection in yellowtail. Intraperitoneal injections of the β-1,3-glucans (2–10 mg/kg) into fish 6 and 3 days prior to intraperitoneal challenge with Streptococcus sp. resulted in a significantly increased survival rate, but the injection did not enhance resistance against Pasteurella piscicida. In β-1,3-glucan-treated fish, an elevation of serum complement and lysozyme activity was observed in addition to an increase in the phagocytic activity of pronephros cells. This suggests that the β-1,3-glucans enhanced the resistance of yellowtail against Streptococcus sp. infection through the activation of the non-specific immune system. The ineffectiveness of the β-1,3-glucans in enhancing the resistance against P. piscicida is discussed.
The extensive and varied reviews regarding the broad spectrum activity of the immunopharmacologic activities of glucans demonstrate the growing interest in these unique molecules. Since the end metabolite is glucose, a new dimension in pharmacology and therapeutics employing this unique molecule is clearly incidated.
At present Krestin is a prescription drug in Japan with both lentinan and Schizophyllan soon to be introduced for the treatment of neoplasia. In the US, clinical studies employing our glucans are presently underway. Mannozym, a glucan-mannan complex, is extensively employed in Hungary and Russia, while soluble yeast glucan is under clinical investigation in Czechoslovakia. In contrast to all of the previously employed immunomodulators such as BCG,C. parvum, MER, pyran copolymer, glucans have few toxic side effects and equivalent or greater immunopharmacologic activities.
Based upon the previously presented data and extensive reviews, as well s current findings from a variety of laboratories, it is clear that glucans are a unique class of immunomodulators and adjuvants with significant clinical potential in infectious diseases, neoplasia, radiation recovery, vaccine development, and control of hemopoeitic activity. While signficant research is clearly yet to be undertaken regarding the most appropriate clinial employment of glucans, the possible applications in clinical as well as agricultural medicine are both numerous and obvious. Additionally, glucans should be effectively employed in defining the relative contribution of various host cells and their secretory products in host defense mechanisms.
In mice and humans zymosan binds to the complement receptor three/Mac-1 receptor; however, identification of this receptor in channel catfish (Ictalurus punctatus) has not been accomplished. Soluble fluorescein isothiocyanate (FITC) conjugated beta-glucan, a component of zymosan, was found to bind to channel catfish anterior kidney (AK) neutrophils but not to B-lymphocytes. Serum activated zymosan (SAZ)-mediated chemiluminescence responses of channel catfish AK neutrophils could be inhibited by beta-glucan but not by mannan, and inhibition of chemiluminescence responses by beta-glucan was dose dependent. Similarly, phagocytosis of FITC-SAZ could be inhibited by beta-glucan in a dose-dependent manner. Treatment of channel catfish AK neutrophils with various concentrations of trypsin resulted in inhibition of phagocytosis of FITC-SAZ but not of Aeromonas hydrophila indicating that A. hydrophila phagocytosis was mediated by a trypsin-resistant receptor. Deleting serum or using heat-inactivated serum in the mixtures for the chemiluminescence and FITC-SAZ phagocytosis assays resulted in baseline readings. These data indicate that the beta-glucan component of zymosan is responsible for zymosan phagocytosis. Furthermore, the recognition of zymosan by a specific receptor is evident based on trypsin sensitivity assays. Based on these results it is proposed that a complement receptor 3, Mac-1-like receptor, is present on channel catfish AK neutrophils.
Phagocytosis of yeast (Saccharomyces cerevisiae) glucan particles by Atlantic salmon (Salmo salar L.) pronephric macrophages was studied. The particles contained > 95% glucose linked through beta-1,3- and beta-1,6-glycosidic linkages. The macrophages rapidly phagocytized both native and opsonized glucan particles although the latter were taken up at a higher rate. Within 30 min, 40-60% of the macrophages had taken up > 1 native glucan particle. The uptake of native glucan particles could be inhibited by preincubating the macrophages with laminarin, a soluble beta-1,3-linked glucan, and a soluble yeast glucan made by partial formolysis of glucan particles. Soluble yeast glucan, on the other hand, did not inhibit uptake of serum opsonized glucan particles or sheep red blood cells, which showed that it did not interfere with phagocytosis in general or inhibit phagocytosis through complement receptors. Polyglucoses with glycosidic linkages other than beta-1,3, like dextran, glycogen, and pustulan or the polymannose mannan, showed little or no inhibition of phagocytosis of native glucan particles. Altogether these observations indicate that Atlantic salmon macrophages may have a specific receptor for yeast glucan. Studies with chelator- and heat-treated salmon serum showed that glucan particles were opsonized primarily by activation of the alternative complement pathway. However, the data indicate that serum components other than complement may also be involved in the opsonization of glucan particles.
The effects of vitamin E (deficiency or supplementation) on the non-specific immune system in rainbow trout, Oncorhynchus mykiss, were evaluated. Rainbow trout were fed daily a semi-purified diet supplemented with vitamin E at 0, 28 and 295 mg x kg(-1) of diet. After 80 days of experimental feeding, the phagocytic function (respiratory burst evaluated by the CL response, phagocytosis) from gut leucocytes and head kidney enriched macrophages was measured; head kidney cell pinocytosis and serum lysozyme activity were also analysed. The results showed that some phagocyte functions were influenced by dietary vitamin E. When fish were fed the high dietary dose of vitamin E an enhancement of phagocytosis was found, but only significantly for the leucocytes isolated from the gut of rainbow trout; moreover, an impaired response was also observed in the fish fed no vitamin E for 80 days. However, no significant differences were noticed on the oxidative burst (CL) response of both gut and head kidney cells according to the dietary dose of vitamin E. Pinocytosis evaluated on head kidney cells was not influenced by dietary vitamin E. Fish fed vitamin E at 295 mg x kg(-1) had a lower serum lysozyme activity than those fed with vitamin E at 28 mg x kg(-1) and the fish fed no vitamin E for 80 days had an impaired activity. Thus, the present results demonstrate that altered dietary levels of vitamin E modulates the phagocytic functions of gut leucocytes in rainbow trout; moreover, the vitamin E diet effect seems to be greater on the local intestinal response as compared to systemic (head kidney). Taken together, this study confirms the crucial role of gut phagocytes in mucosal non-lymphoid defences in fish.
The immunostimulant beta-1,3 glucan was fed at 0.1% in feed for 7 days to healthy and aflatoxin B1 (AFB1)-induced immunocompromised fish, Labeo rohita (one of the major tropical carp species), in a 60 day trial. The effects of AFB1, glucan and their interactions on non-specific and specific immunity levels and disease resistance of fish were studied. A single intraperitoneal injection of AFB1 at 1.25 mg kg(-1) body weight) caused a significant (P < 0.05) reduction in non-specific immunity as measured through neutrophil phagocytic indices, serum bactericidal activity, and specific immunity as measured through bacterial agglutination titre against Edwardsiella tarda, as well as reduced protection against Aeromonas hydrophila challenge in comparison to control fish which were exposed neither to aflatoxin nor to glucan. Feeding of glucan to healthy fish raised the non-specific and specific immunity level and protection against bacterial infection compared with the control. Feeding of glucan to AFB1-induced immunocompromised fish for 7 days significantly raised the degree of resistance against A. hydrophila challenge and the non-specific immunity level in comparison to non-treated AFB1 exposed fish. Although feeding of glucan was able to increase specific immunity, all measured through haemagglutination titre against sheep red blood cells, and bacterial (E. tarda) agglutination titre in healthy fish in comparison to all other groups, no significant increase in specific immunity to the aflatoxin-exposed group was seen.
The effects of including lyophilised whole yeast, Saccharomyces cerevisiae, in the diet on the seabream innate immune response were investigated. Gilthead seabream (Sparus aurata L.) specimens were fed four different diets for 4 weeks: a commercial diet as control and the same diet supplemented with 1, 5 or 10 g/kg yeast. After 1, 2 and 4 weeks, serum complement titres, as a humoral parameter, and phagocytic, respiratory burst, myeloperoxidase and natural cytotoxic activities of head-kidney leucocytes, as cellular parameters, were evaluated. The results showed that yeast supplements enhanced all the latter responses, but not the humoral response. This enhancement was dose-dependent except for the cytotoxic activity that was only stimulated by the lower dose of yeast assayed. As yeast cell walls are able to enhance the seabream cellular innate immune response, these results support the possible use of whole yeast as natural inmunostimulants in common fish diets.
The effects of orally administered carotenoids from natural sources on the non-specific defense mechanisms of rainbow trout were evaluated in a nine-week feeding trial. Fish were fed four diets containing either beta-carotene or astaxanthin at 100 and 200 mg kg-1 from the marine algae Dunaliella salina and red yeast Phaffia rhodozyma, respectively, and a control diet containing no supplemented carotenoids. Specific growth rate and feed:gain ratio were not affected by dietary carotenoid supplementation. Among the humoral factors, serum alternative complement activity increased significantly in all carotenoid supplemented groups when compared to the control. On the other hand, serum lysozyme activity increased in the Dunaliella group but not in the Phaffia group, whereas plasma total immunoglobulin levels were not altered by the feeding treatments. As for the cellular responses, the superoxide anion production from the head kidney remained unchanged while the phagocytic rate and index in all supplemented groups were significantly higher than those of the control. These findings demonstrate that dietary carotenoids from both D. salina and P. rhodozyma can modulate some of the innate defense mechanisms in rainbow trout.
The present study investigated the immunomodulatory activity of Ergosan, an algal extract containing alginic acid, and Macrogard, a yeast extract containing β-glucans, on innate and specific immunity in sea bass (Dicentrarchus labrax). Four cycles of experimental feeding using normal fish feed formulation (control group) supplemented with Ergosan (0.5%) or Macrogard (0.1%) were performed at 60-day intervals (15 days of treatment + 45 days of suspension). Serum complement, lysozyme, total proteins and heat shock protein (HSP) concentrations were measured at 15, 30 and 45 days from the end of the first 15-day feeding cycle (short term) and 45 days after the end of each feeding cycle over a 35-week period (long term). The percentage of B- and T-lymphocytes in peripheral blood leucocytes and gut were measured over long-term trial.
Assays of hemolytic complement activity
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Isolation of salmonid macrophages and analysis of their killing activity
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Secombes CJ. Isolation of salmonid macrophages and analysis of their killing activity. In: Stolen JS, Fletcher TC, Anderson DP, Robertsen BS, Van Muiswinkel WB, editors. Techniques in fish immunology. Fair Haven, NJ: SOS Publications; 1990. p. 137e54.
Glucan-based macrophage stimulators. A review of their anti-infective potential
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Williams DL, Mueller A, Browder W. Glucan-based macrophage stimulators. A review of their anti-infective potential. Clin Immunother 1996;5:392e9.
β;-glucans as immunostimulants in fish
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Robertsen B, Engstad RE, Jøgensen JB. b;-glucans as immunostimulants in fish. In: Stolen JS, Fletcher TC, editors. Modulators of fish immune responses, vol.
Assays of hemolytic complement activity
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