The role of β-glucan in the growth, intestinal morphometry, and immune-related gene and heat shock protein expressions of Nile tilapia (Oreochromis niloticus) under different stocking densities

Synergistic Effect of Dietary Supplementation with Sodium Butyrate, β-Glucan and Vitamins on Growth Performance, Cortisol Level, Intestinal Microbiome and Expression of Immune-Related Genes in Juvenile African Catfish (Clarias gariepinus)

The effect of dietary supplementation with sodium butyrate, β-glucan and vitamins (A, D3, E, K, C) on breeding indicators and immune parameters of juvenile African catfish was examined. The fish were fed with unenriched (group C) and enriched feed with a variable proportion of sodium butyrate/β-glucan, and constant content of vitamins (W1-W3). After the experiment, blood and the middle gut were collected. The microbiome of the gut was determined using Next Generation Sequencing (NGS). Liver tissue was collected for determination of expression of immune-related genes (HSP70, IL-1β, TNFα). W2 and W3 were characterized by the most favorable values of breeding indicators (p < 0.05). The highest blood cortisol concentration was in group C (71.25 ± 10.45 ng/mL), and significantly the lowest in W1 (46.03 ± 7.01 ng/ mL) (p < 0.05). The dominance of Cetobacterium was observed in all study groups, with the largest share in W3 (65.25%) and W1 (61.44%). Gene expression showed an increased number of HSP70 genes in W1. IL-1β and TNFα genes peaked at W3. The W3 variant turns out to be the most beneficial supplementation, due to the improvement of breeding and immunological parameters. The data obtained can be used to create a preparation for commercial use in the breeding of this species.

Long- and short-term dietary β-glucan improves intestinal health and disease resistance in pearl gentian grouper (Epinephelus lanceolatus♂ × Epinephelus fuscoguttatus♀)

β-Glucans are immunostimulants and are widely used in aquaculture industry. The present study was conducted to evaluate the effects of different periods of β-glucan management on growth performance, intestinal health, and disease resistance in pearl gentian grouper (Epinephelus lanceolatus♂ × Epinephelus fuscoguttatus♀). A commercial feed was used as control diet (CD), and the β-glucan diet (βD) was based on CD and further supplemented with 0.1% β-glucan. Grouper in control and long-term β-glucan diet (LGD) groups were fed with CD and βD for 8 weeks, respectively. Groupers in short-term β-glucan diet (SGD) group were fed with CD for the first 4 weeks and βD for the last 4 weeks. We found that LGD and SGD had no effect on growth performance but reduced the mortalities of grouper after challenging with Vibrio harveyi. In addition, both LGD and SGD increased intestinal morphology, enhanced antioxidant capacity, enhanced immunity, inhibited apoptosis, altered the transcriptional profile, and activated mitogen-activated protein kinase (MAPK) and nuclear factor kappa-B (NF-κB) signaling pathway in the intestine of grouper. Furthermore, the effect of LGD on most of the above parameters was comparable to that of SGD. In conclusion, LGD and SGD did not affect growth rate parameters but enhanced the intestinal health and disease resistance of pearl gentian grouper.

Effects of dietary nucleotide and yeast cell wall on growth performance, feed utilization, anti-oxidative and immune response of grass carp (Ctenopharyngodon idella)

A 70-day feeding trial was conducted to study the effects of dietary nucleotide, yeast cell wall (containing 20% β -glucan) and their combination on growth performance, feed utilization and immune response of grass carp (Ctenopharyngodon idella) with 69.97 ± 0.05 g of initial body weight. Four isonitrogenous (about 38% crude protein) and isolipidic (about 5% crude lipid) diets were established. Based on the control diet (CD), the other three experimental diets were prepared by adding 0.01% of nucleotide (NT), 0.1% of yeast cell wall (YCW) and NT (0.01%) +YCW (0.1%), respectively. Results showed that no significant difference was found in survival of grass carp ranging from 94.44% to 97.78% among all the groups (P > 0.05). Compared with the control group, weight gain rate, muscle crude protein content, serum protein, trypsin and chymotrypsin activities in midgut, lysozyme and immunoglobulin M in serum significantly increased in fish fed the YCW diet (P < 0.05). The significantly highest weight gain rate, villus height and digestive enzyme activities in midgut and innate immune parameters in serum were found in fish fed the NT + YCW diet (P < 0.05). The gene expressions of β-defensin, hepcidin, il-10 and tgf-β1 in the midgut, and tor and s6k1 in liver significantly increased in fish fed the NT + YCW diet. Meanwhile, the gene expressions of il-1β and tnf-α in the midgut decreased significantly (P < 0.05). The liver histology showed the better development in dietary NT and/or YCW supplemented groups than those in the control group. In conclusion, combination of dietary NT and YCW had significantly synergetic improvements on the growth, feed utilization, digestive enzymes, innate immunity and histology of midgut and liver of grass carp.

β-1,3-glucan improved the health and immunity of juvenile African catfish (Clarias gariepinus) and neutralized the histological changes caused by lead and fipronil pollutants

BACKGROUND

Water pollutants cause adverse effects in aquatic ecosystems. The immunomodulatory and mitigating effects of dietary 1,3-glucan on fipronil and lead-induced intoxication in African catfish (Clarias gariepinus) were investigated. Two hundred forty catfish were randomly divided into four equal groups: those in the first group were fed basic diet and served as controls; those in the second group were supplemented with β-1,3-glucan (0.1%); those in the third group were exposed to combination of lead nitrate at 0.041 mg/L (1/10 96 h LC50) and fipronil at 2.8 mg/l (1/10 96 h LC50); and those in the fourth group were exposed to combination of fipronil, lead, and β-1,3-glucan. The health status, haematological, immunological, and histological changes were all evaluated.

RESULT

Swelling on the dorsolateral side, spinal column deviation, sluggish movement, skin bleaching, excessive mucus secretion, significant variations in blood indices-related measures, and a 45% death rate were observed in the third group. There was a significant reduction in interleukin-1 (IL-1) and interleukin-6 (IL-6) and immunoglobulin M (IgM) concentrations, as well as decrease in their corresponding gene expression, indicating that fipronil and lead had immunosuppressive activity. Severe catarrhal enteritis and mucinous degeneration of the lining epithelium, and notable depletion of white pulp, congested red pulp and hemosiderosis were common pathological findings in the spleen. β-1,3-glucan alone or in combination with fipronil and lead provoked physical activity, blood indices, with elevations in IL-1β, IL-2, IL-6, and IgM concentrations, as well as up-regulation in their genes' expression in splenic tissues, when compared to the third group. The spleen and intestine had normal histological architecture with 5% mortalities. There were no fish deaths in the β-1,3-glucan-alone or control groups.

CONCLUSION

The use of β-1,3-glucan (0.1%) as dietary supplement could be implemented to protect against the toxic effects of fipronil and lead toxicity by improving the health and immunological parameters of intoxicated catfish.

The combined effects of salinity and ammonia on the growth behavior, stress-related markers, and hepato-renal function of common carp (Cyprinus carpio)

One of the most critical factors affecting aquaculture efficiency is the capability of releasing ammonia from the water. By applying a high salinity strategy, this study provides a prompt approach for removing high ammonia levels and relieving its adverse impacts on common carp. The study investigated five groups with triplicates where the control was kept with fresh water, and the remaining four groups stressed with different salinity levels (5, 10, 15, and 20 ppt) for 8 weeks. Then fish were exposed to unionized ammonia (NH₃ ) stress (0.5 ppm) for 6 h. The final weight (FBW) and weight gain (WG) showed lower values in fish stressed with 15 and 20 ppt salinity levels than fish reared in 0 and 5 ppt salinity levels (p < 0.05). The lowest FBW and WG and the highest feed conversion ratio were shown in fish grown in 20 ppt (p < 0.05). The survival rate was markedly lowered by 15 and 20 ppt salinity levels (p < 0.05), while no significant differences were observed among 0, 5, and 10 ppt salinity levels (p > 0.05). Liver condition-related indices (alanine aminotransferase, aspartate aminotransferase, and alanine aminotransferase) were markedly increased in fish grown in 15 and 20 ppt before or after ammonia stress (p < 0.05). The results showed higher creatinine levels in fish raised in 15 and 20 ppt than the remaining salinity levels, with the highest value in fish of 20 ppt salinity before and after ammonia stress (p < 0.05). Markedly the blood glucose and cortisol levels were upraised in fish reared in 10, 15, and 20 ppt before and after ammonia stress (p < 0.05). The glucose level was not significantly different in fish reared in 5 ppt than 0 and 10 ppt salinity levels (p < 0.05). Generally, the blood glucose and cortisol levels were decreased markedly after ammonia stress than before ammonia stress (p < 0.05). Interestingly, total protein, albumin, and globulin levels were increased in common carp reared in different salinity levels after ammonia stress (p < 0.05). In conclusion, ammonia toxicity combined with high salinity resulted in a regulatory effect on the hepato-renal function and stress-related markers in common carp.

Role of Clostridium butyricum, Bacillus subtilis, and algae-sourced β-1,3 glucan on health in grass turtle

This study investigated the effects of two probiotics namely Clostridium butyricum and Bacillus subtilis, and one prebiotic known as algae-sourced β-1,3 glucan, on the overall performances of grass turtles (Chinemys reevesii) juveniles. Growth performance, immune responses, enzymatic antioxidant activities, intestinal histomorphology, and disease resistance against the challenge with Aeromonas veronii were assessed. Two hundred and sixteen (216) juvenile turtles with an average initial weight of 106.35 ± 0.03 g were divided into four groups, each containing three replicates with 18 turtles per each replicate, which were fed a basic diet (control group, GD) and a basal diet supplemented with C. butyricum 1.0 × 10⁸ CFU per kg (GA group), or with B. subtilis 1.0 × 10⁸ CFU per kg (GB group) and with algal-sourced β-1,3-glucan 50 mg per kg (GC group), respectively. After the turtles had been fed for 60 d, 90 d, and 120 d of the experimental period, the growth performance and survival rate (SR), intestinal digestive enzyme, hepatic and intestinal antioxidant capacity, serum biochemical indexes, and immune performance were measured. The results showed that the weight gain rate and SR were significantly enhanced (P < 0.05) after fed probiotics and algae-sourced β-1,3-glucan in all test times;The pepsin, amylase, acid phosphatase, total antioxidant capacity, triglyceride, alkaline phosphatase, urea nitrogen, cholesterol, total protein, IgA, IgG, IgM at 120 d were significantly enhanced (P<0.05) after fed C. butyricum. The intestinal villi heights, widths, and the thickness of the muscle layer were significantly higher in groups GA, GB, and GC than those reared within the GD control group (P < 0.05). After injecting the challenge by A. veronii the survival rate of grass turtles in the GA group (75%) was significantly higher than the other three groups (P<0.05), while there was no significant difference between the GB and GC groups compared with the control GD group, respectively (P>0.05). Overall, these results indicated that dietary supplementation with probiotics or algae-sourced β-1,3 glucan, exhibited positive effects on C. reevesii. In particular, C. butyricum, showed the greatest improvements relating to growth, immune response, antioxidant activity, intestinal health, and disease resistance.

Dietary supplementation of Nile tilapia (Oreochromis niloticus) with β-glucan and/or Bacillus coagulans: Synergistic impacts on performance, immune responses, redox status and expression of some related genes

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.

Synbiotic Lactic Dry ® enhanced the growth performance, growth-related genes, intestinal health, and immunity of Nile tilapia reared in inland brackish groundwater

Nile tilapia is recognized as a suitable candidate for intensive farming and sustainability of the aquaculture industry. However, one issue limiting Nile tilapia expansion in arid and semi-arid areas is the scarcity of freshwater resources. In this study, the supplementation of synbiotics was investigated to enhance the growth performance, growth-related genes, intestinal health, and immunity of Nile tilapia reared in inland brackish groundwater. Four diets were prepared where the basal diets were mixed with the dietary mixture of probiotics and prebiotics (Synbiotic Lactic Dry®, a blend of Saccharomyces cerevisiae, Lactobacillus acidophilus, Streptococcus faecium, and Bacillus subtilis, mannan oligosaccharides and β-1.3/1.6-D-glucan) at 0, 0.5, 1, and 2 g/kg. After eight weeks, the final weight and weight gain are linearly increasing with increasing the supplementation level of synbiotic. Markedly fish fed 0.5, 1, and 2 g/kg of synbiotic had higher final weight, weight gain, and feed intake and lower feed conversion ratio (FCR) than fish fed synbiotic free diet. The specific growth rate (SGR) was significantly higher in fish fed 1 and 2 g/kg than in fish fed 0 and 0.5 g/kg. The intestine of fish fed on synbiotic shows an increase in intestinal villi density. Further, the intestine of fish fed on synbiotic showed an increase in the length and branching intestinal villi (anterior, middle, and posterior) in a dose-dependent manner. The lysozyme and phagocytic activities were significantly different from the control, while synbiotic supplementation did not affect the phagocytic index. Interestingly, the results showed marked upregulation of ghrelin, IGF-1, and GH genes in fish fed synbiotics at 0.5, 1, and 2 g/kg. In addition, fish fed 2 g/kg had the highest expression of ghrelin, IGF-1, and GH genes. In conclusion, growing Nile tilapia in inland brackish groundwater can be achieved without negative impacts on the growth performance and health status. Supplementing synbiotics (1-2 g/kg) in Nile tilapia feeds enhanced the growth and feed performances, intestinal histomorphological features, growth-related genes, and immune response.

Effects of sulfated β-glucan from Saccharomyces cerevisiae on growth performance, antioxidant ability, nonspecific immunity, and intestinal flora of the red swamp crayfish (Procambarus clarkii)

The aim of this study was to examine the combined effects of sulfated β-Glucan from Saccharomyces cerevisiae (sGSC) on growth performance, antioxidant ability, nonspecific immunity, and intestinal flora of the red swamp crayfish (Procambarus clarkii). Four experimental diets (sGSC25, sGSC50, sGSC100 and sGSC200) with different levels of sGSC (0.025%, 0.05%, 0.1% and 0.2% in diet, respectively) were fed to juvenile crayfish (average weight: 2.5 ± 0.5 g) for 8 weeks. The control diet was given with 2000 mg/kg GSC (GSC200 group). The based control diet was given without sGSC or GSC (blank group). Each group had 3 parallel test pools, 20 crayfish were reared in each pool. At the end of the growth trial, adding dietary 0.025%-0.1% sGSC could significantly improve the growth performance, antioxidant capacity and immunity of crayfish. Compared with GSC, sGSC had a better effect at lower concentration. Higher concentration of sGSC (>0.1%) would cause some side effects. sGSC also could improve the structure of the intestinal flora and optimize the function of the flora. sGSC would increase the abundances of probiotics such as Hafnia and Acinetobacter, and decreases the abundances of maleficent bacteria such as Enterobacteriaceae. Higher concentration of sGSC (>0.1%) would increase the abundance of Aeromonas. To conclude, 0.025%-0.1% sGSC can be used as a supplement in crayfish feed to increase growth, immunity, and antioxidant capacity and improve the structure of intestinal flora. These results provided a theoretical basis for the application of sGSC instead of GSC in crayfish breeding. It will be necessary to further study the optimal concentration of sGSC in feed additives in different growth stages of crayfish in the future.

Dietary Supplementation of Bacillus sp. PM8313 with β-glucan Modulates the Intestinal Microbiota of Red Sea Bream (Pagrus major) to Increase Growth, Immunity, and Disease Resistance

A 56-day feeding trial was conducted to determine the effect of dietary supplementation with Bacillus sp. isolated from the intestines of red sea bream on the growth performance, immunity, and gut microbiome composition of red sea bream. Three diets (a control diet and two treatments) were formulated without Bacillus sp. PM8313 or β-glucan (control, CD), 1 × 108 CFU g-1 PM8313 (BSD), and 1 × 108 CFU g-1 PM8313 + 0.1% β-glucan (BGSD). At the end of the experiment, the weight, specific growth rate, feed conversion ratio, and protein efficiency ratio of the fish in the BSD and BGSD diet groups were significantly improved than those of the control group (P < 0.05). Additionally, amylase and trypsin activities were significantly higher (P < 0.05) in both groups compared to the control. Superoxide dismutase and lysozyme activity, which are serum non-specific immune responses, only increased in the BGSD group. The two treatment groups exhibited a marked difference in the intestinal microbiota composition compared to the control group. Furthermore, the treatment groups exhibited an upregulation of IL-6 and NF-κb, coupled with high survival rates when challenged with Edwardsiella tarda. Therefore, dietary supplementation with PM8313 improved the growth performance, digestive enzyme activity, non-specific immunity, and pathogen resistance of red sea bream, in addition to affecting the composition of its intestinal microflora.

The effects of extended feeding of florfenicol coated medicated diets on the safety, serum biomarkers and blood cells morphology of Nile tilapia Oreochromis niloticus (L.)

Tilapia is one of the most consumed farmed fish, which requires the use of antibiotics in certain phases of its production. This study assessed the safety of 30 days of oral florfenicol (FFC) dosing at 0-10 times the therapeutic dose (1 × : 10 mg/kg biomass/day) in Oreochromis niloticus juveniles. Behavioural changes, feed consumption, mortality and biomass were evaluated. Besides, the levels of serum glucose, calcium, chloride, creatinine, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and blood cell morphology were determined at scheduled intervals. The 30 days of oral FFC dosing caused 3.33% (1 ×) to 18.33% (10 ×) mortalities, reduced feed intake and biomass in a dose-dependent manner. The fish fed the therapeutic dose recorded 1.25-fold increase in biomass, while the control group recorded 1.45-fold increase in 30 days. No significant erythrocyte morphological alterations were observed in the 1 × group compared to the control. However, marked morphological alterations like tear-shaped, spindle-shaped and degenerative erythrocytes in higher dosing groups indicated FFC cytotoxicity. All the serum biomarkers of O. niloticus increased significantly on day 10 and day 30 FFC dosing in a dose-dependent manner, except for calcium and chloride, which reduced significantly during the dosing period. Within 2 weeks of suspension of FFC dosing, the serum biomarker levels became normal except for alkaline phosphatase and creatinine. The recovery of biomass, feed intake, serum biomarker levels and erythrocyte morphological changes suggested that the FFC-induced changes are reversible. This study has, thus, proclaimed the safety of FFC at the therapeutic dose in O. niloticus.

Blood Performance: A New Formula for Fish Growth and Health

Simple Summary

The use of haematological and blood biochemistry parameters has proven to be effective and repeatable ways to monitor fish health. Testing these parameters is becoming more common in aquaculture studies. Further, it is widely accepted that fish with better health status are more likely to grow faster as less energy should be consumed for non-growth purposes. Here, a new formula (Blood Performance) is introduced, which contains five common haematological and blood biochemistry parameters: red blood cells, white blood cells, haemoglobin, haematocrit, and total protein. The idea behind this formula is that any single component of this formula cannot be reliable enough as a biomarker of fish health and growth. However, interestingly, Blood Performance can be much more reliable and accurate for monitoring fish health and growth.

Abstract

Monitoring fish health in a repeatable and accurate manner can contribute to the profitability and sustainability of aquaculture. Haematological and blood biochemistry parameters have been powerful tools and becoming increasingly common in aquaculture studies. Fish growth is closely related to its health status. A fish with a higher growth rate is more likely to be a healthy one. Any change in the physiological status of the fish, from pollution to nutritional stress, can cause changes in the blood parameters. Various aquaculture studies have measured the following components: red blood cells, white blood cells, haemoglobin, haematocrit, and total protein. However, because these parameters do not always follow the same trend across experimental fish, it is difficult to draw a firm conclusion about which parameter should be considered. Therefore, Blood Performance (BP) as a new formula is introduced, which is a more reliable indicator. This formula is simple and sums up the natural logarithm of the five above-mentioned parameters. More than 90 published peer-reviewed articles that measured these five parameters in the last six years confirmed the reliability and validity of this formula. Regardless of which supplements were added to the diets, the fish with a higher growth rate had higher BP as well. In addition, in 44 studies out of 53 articles, there was a significant positive correlation between specific growth rate and BP. Under different stressful situations, from pollution to thermal stress, the fish under stress had a lower BP than the control. Fish meal and fish oil replacement studies were further evidence for this formula and showed that adding excessive alternative proteins decreased growth along with BP. In conclusion, BP can be a reliable indicator of fish health and growth when it is compared between groups in the same experiment or farm. Although there was a positive correlation between specific growth rate and BP, comparing BP between experiments is not recommended. Standardising the haematological assays can improve the reliability and accuracy of BP across experiments.

Immune Status and Hepatic Antioxidant Capacity of Gilthead Seabream Sparus aurata Juveniles Fed Yeast and Microalga Derived β-glucans

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.

β-glucan as a promising food additive and immunostimulant in aquaculture industry

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.

β-glucan mimics tissue damage signaling and generates a trade-off between head kidney and spleen to activate acquired immunity in vaccinated tilapia (Oreochromis niloticus)

The association of vaccines with immunostimulants such as β-glucan, promote the production of cytokines, competent immune cells and antibodies. However, differences between β-glucan types and trials make it difficult to understand β-glucan's mechanism of action. In this study, three trials were carried out with control and fish fed β-glucan, the first trial occurred at 15 days; the second trial occurred at 30 days when we associated β-glucan and vaccine; and the third trial occurred at 15 days post-challenge with Streptococcus agalactiae in tilapia (O. niloticus) in order to investigate immune-related gene expression in the head kidney and spleen using real-time qPCR. We found increases in HSP70, IL-6, IL-1β, TNF-α, IL-10, Lys and C3 predominantly in the head kidney, except for IgM expression, which prevailed in the spleen, under vaccinated + β-glucan action. This demonstrates the trade-off presented by the head kidney and spleen after immunostimulation in order to produce acquired immunity, as well as an increase in HSP70 expression in vaccinated + β-glucan fish. The results suggest that β-glucan stimulates the immune response through damage-associated molecular patterns (DAMPs) recognition. Therefore, these dynamics of the immune response promote a more robust defense against disease.

A mixture of β-Glucan and Mannanoligosaccharide Ameliorated the Growth Rate, Digestive Enzyme Activity, Intestinal Morphometry, and Immunity of Common Carp ( Cyprinus carpio )

The feasible strategies to keep up the growth and wellbeing of aquatic organisms by using beneficial dietary additives are highly recommended. Among these additives, β-glucan (BG) and mannanoligosaccharide (MOS) were examined on common carp performances in the current experiment. For 80 days, carps were fed four diets with 0%, 1%, 2%, and 3% BG/MOS (1:1) and distributed in four groups (triplicates). Higher final weight and weight gain (P<0.05) were detected in carps fed 1%, 2%, and 3% of BG/MOS than the control group. The feed conversion ratio showed lower values (P<0.05) in carps fed BG/MOS mixture at 2%, and 3% than 0% and 1% levels. The activities of amylase, lipase, and protease were higher in fish fed BG/MOS mixture than in the control group. Interestingly, fish fed BG/MOS mixture had markedly increased villi length and width with branched villi integrity. Further, the count of goblet cells was increased (P<0.05) in groups fed BG/MOS mixture than in carps fed the basal diet. The hemoglobin and hematocrit levels and the counts of red and white blood cells were higher in carps fed BG/MOS mixture than the control with the highest counts in 3% level. Additionally, the blood total protein, globulin, and phagocytic activity were higher (P<0.05) in groups that received BG/MOS mixture at 3% than the control. The lysozyme had a higher value in 1% group than the control (P<0.05). Therefore, using the mixture of BG/MOS at 2–3% is suggested for improving the growth rate, intestinal health, blood health, and immunity of common carp.

Dietary Aspergillus oryzae Modulates Serum Biochemical Indices, Immune Responses, Oxidative Stress, and Transcription of HSP70 and Cytokine Genes in Nile Tilapia Exposed to Salinity Stress

Simple Summary

Probiotics are live microbial adjuncts with numerous beneficial effects on fish. This study aims to evaluate the roles of Aspergillus oryzae (ASP) in the modulation of serum haemato-biochemical measurements, immunity, antioxidative capacity, and transcriptomic responses of Nile tilapia juveniles exposed to salinity stress. Findings revealed that dietary supplementation with A. oryzae mitigated the harmful influences of salinity stress on the exposed Nile tilapia.

Abstract

Nile tilapia Juveniles (19.50 ± 0.5 g) were fed on a basal diet (control group (CTR)) and a diet supplemented with 1 g Aspergillus oryzae (ASP) per kg diet for 12 weeks. Fish were then subjected to different salinity levels (0, 10, 15, and 20 practical salinity units (psu)) for another 15 days. Two-way ANOVA analysis revealed that the individual effects of ASP in Nile tilapia exposed to salinity levels presented a significant decrease (p < 0.05) in values of haemato-biochemical indices (such as glucose, cortisol, alanine transaminase, aspartate transaminase, and malondialdehyde) compared to those in the CTR group exposed to the same salinity levels. Moreover, significant increases (p < 0.05) of blood protein profile (albumin, globulin, and total protein), non-specific immune responses (lysozyme activity, phagocytic activity, and phagocytic index), and antioxidant enzymes activities (glutathione peroxidase, catalase, and superoxide dismutase) were observed in ASP-supplemented groups. Interestingly, there was significant (p < 0.05) downregulation of the mRNA expression values of heat shock protein 70 and interferon-gamma genes, alongside upregulation of the mRNA expression values of interleukin 1 beta and interleukin 8 genes, in the hepatic tissues of Nile tilapia in ASP-supplemented groups exposed to different salinities compared to those in the CTR group exposed to the same salinity levels. Taken together, these findings supported the potential efficacy of dietary supplementation with ASP in alleviating salinity stress-induced haemato-biochemical alterations, immune suppression, and oxidative stress in the exposed Nile tilapia.

Effects of bovine lactoferrin and chitosan nanoparticles on serum biochemical indices, antioxidative enzymes, transcriptomic responses, and resistance of Nile tilapia against Aeromonas hydrophila

The present study was carried out to investigate the effects of dietary bovine lactoferrin (BLF) or chitosan nanoparticles (CHN) alone or in combinations on serum biochemical indices, antioxidative capacity, transcriptomic responses, non-specific immunity, and resistance of Nile tilapia (Oreochromis niloticus) against challenge with Aeromonas hydrophila. Fish were fed on the basal diet with no supplements and served as control (CTR), and six other experimental diets containing different levels of BLF (800 and 1200 mg per kg diet), CHN (500 and 1000 mg per kg diet), and their combinations (400 mg BLF plus 250 mg CHN per kg diet, and 600 mg BLF plus 500 mg CHN per kg diet) for 45 days. At the end of the experiment, serum, and tissue specimens (liver and kidney) were collected, fish in all groups were challenged with A. hydrophila and then observed for another ten days to calculate the RPS. Compared to the CTR group, no significant differences were recorded in TP, ALB, GLO, BUN, and CREAT values among all treatments. Serum LYZ, ALT, AST, and ALP enzyme activities were significantly increased in all experimental groups over the CTR (P < 0.05), and their highest values were recorded in the combined treatments. Moreover, dietary supplementation with CHN (1000 mg/kg) and combined treatments significantly increased the SOD, CAT, and GSH-Px enzyme activities compared to other groups (P < 0.05). The highest mRNA expression levels of IGF-1 gene in liver, and IL-1β, and IFN-γ genes in kidneys were found in CHN (1000 mg/kg) group and combined treatments more than other groups. Interestingly, no, or mild histopathological alterations were noticed in the hepatopancreas and posterior kidney of the treated groups. A significantly higher RPS was identified in the combined treatments challenged with A. hydrophila compared with the CTR group. This study exemplifies the positive impacts of dietary supplementation with BLF or CHN alone or combinations on the antioxidative status, immunity, and disease resistance of Nile tilapia.

Antiparasitic and Antibacterial Functionality of Essential Oils: An Alternative Approach for Sustainable Aquaculture

Using synthetic antibiotics/chemicals for infectious bacterial pathogens and parasitic disease control causes beneficial microbial killing, produces multi-drug resistant pathogens, and residual antibiotic impacts in humans are the major threats to aquaculture sustainability. Applications of herbal products to combat microbial and parasitic diseases are considered as alternative approaches for sustainable aquaculture. Essential oils (EOs) are the secondary metabolites of medicinal plants that possess bioactive compounds like terpens, terpenoids, phenylpropenes, and isothiocyanates with synergistic relationship among these compounds. The hydrophobic compounds of EOs can penetrate the bacterial and parasitic cells and cause cell deformities and organelles dysfunctions. Dietary supplementation of EOs also modulate growth, immunity, and infectious disease resistance in aquatic organisms. Published research reports also demonstrated EOs effectiveness against Ichthyophthirius multifiliis, Gyrodactylus sp., Euclinostomum heterostomum, and other parasites both in vivo and in vitro. Moreover, different infectious fish pathogenic bacteria like Aeromonas salmonicida, Vibrio harveyi, and Streptococcus agalactiae destruction was confirmed by plant originated EOs. However, no research was conducted to confirm the mechanism of action or pathway identification of EOs to combat aquatic parasites and disease-causing microbes. This review aims to explore the effectiveness of EOs against fish parasites and pathogenic bacteria as an environment-friendly phytotherapeutic in the aquaculture industry. Moreover, research gaps and future approaches to use EOs for sustainable aquaculture practice are also postulated.

Dietary Gracilaria persica mediated the growth performance, fillet colouration, and immune response of Persian sturgeon (Acipenser persicus)

Algal seaweeds have abundant amounts of active substances and can be used as pharmaceuticals and biomedicals in aquafeeds. In this context, the powder of red macroalgae Gracilaria persica was included in the diets of Persian sturgeon at the rate of 0, 2.5, 5, and 10 g/kg to investigate its role on the growth rate, fillet colouration, haemato-biochemical indices, serum, and skin mucus immunity. The weight gain, SGR, and FCR displayed no significant changes in fish fed varying levels of G. persica (P > 0.05). The level of total carotenoids was significantly higher in the blood and fillet of fish fed 5 and 10 g G. persica/kg diet (P < 0.05). Dietary G. persica significantly altered RBCs, WBCs, and HCT at 5, and 10 g/kg, whereas the Hb was increased in fish fed 5 g/kg (P < 0.05). The blood total protein and albumin were significantly increased in fish fed 5 and 10 g/kg (P < 0.05). No significant alterations were observed on ALT, AST, ALP, and glucose levels of fish fed varying levels of G. persica (P > 0.05). Serum Ig, lysozyme, superoxide dismutase, catalase, and respiratory burst activities were increased in fish fed 5, and 10 g/kg than fish fed 0 and 2.5 g/kg diet (P < 0.05). The level of total protein and lysozyme activity in the skin mucus were significantly higher in the blood and fillet of fish fed 5, and 10 g G. persica/kg diet than fish fed 0 and 2.5 g/kg (P < 0.05). Based on the obtained results, G. persica can be used as a feasible feed additive in the diets of Persian sturgeon at 5-10 g/kg diet.

The Effect of Stocking Density and Carbon Sources on the Oxidative Status, and Nonspecific Immunity of Nile tilapia (Oreochromis niloticus) Reared under Biofloc Conditions

Simple Summary

The present study investigated the effect of stocking density and dietary carbon sources on the water quality, oxidative status and immune-related of Nile tilapia (Oreochromis niloticus) reared under biofloc conditions (BFT). Eight groups were established at two levels of stocking densities (140 fish per m³: low stocking density, LSD) and (280 fish per m³: high stocking density, HSD) (5.15 ± 1.12 g) and kept in eight biofloc units containing water without carbon sources (control groups) or with glycerol, molasses, or starch. Overall, this study has reported that immune response gene expression is better in LSD than HSD and improved by carbon addition. More specifically, based on the overall performances of tilapia reared under LSD or HSD, using molasses is recommended as a carbon source to promote the performances and health status of Nile tilapia cultured in a biofloc system.

Abstract

The present study investigated the effect of stocking density and dietary carbon sources on the water quality, oxidative status, and immune-related genes of Nile tilapia (Oreochromis niloticus) reared under biofloc conditions (BFT). Eight groups were established at two levels of stocking densities (140 fish per m³: low stocking density, LSD) and (280 fish per m³: high stocking density, HSD) (5.15 ± 1.12 g) and kept in eight biofloc units containing water without carbon sources (control groups) or with glycerol, molasses, or starch. Red blood cells count, hemoglobin, and hematocrit values were reduced in fish stocked in control groups at LSD and HSD than biofloc groups. Control fish groups reared at both LSD and HSD have the highest significant (p < 0.05) white blood cells number than other fish groups. Meanwhile, fish groups that received glycerol, molasses, and starch maintained in both LSD and HSD presented a higher significant (p < 0.05) monocyte % than in the control group reared at both LSD and HSD. The fish group reared in biofloc conditions (BFT) using starch carbon source and reared at the HSD presented a significantly higher (p < 0.05) increase in total serum protein and albumin levels as well as globulin value than the control fish group reared at both LSD and HSD. The highest glucose and cortisol levels were showed in the control fish group reared at both LSD and HSD. Fish maintained in glycerol-based biofloc at LSD attained the highest (p < 0.05) serum superoxide dismutase (SOD), glutathione reductase (GR), and catalase than other experimental groups. Regarding the nonspecific immune status, significantly increased expression of CC-chemokines, CXC-chemokines, TLR7 and IL-8 genes was found in molasses based biofloc groups. The data of the present study revealed that using molasses promotes health status of Nile tilapia cultured in a biofloc system.

Yucca schidigera Usage for Healthy Aquatic Animals: Potential Roles for Sustainability

Simple Summary

This review presents an updated and exclusive collection of results about yucca’s beneficial effects as phytogenic additives for clean aquaculture activity. The overall performances of aquatic organisms treated with yucca as dietary additives of water cleaners encourage performing further studies to prove its mode of action based on biochemical and biological techniques.

Abstract

In modern aquaculture systems, farmers are increasing the stocking capacity of aquatic organisms to develop the yield and maximize water resources utilization. However, the accumulation of ammonia in fishponds regularly occurs in intensive aquaculture systems, resulting in reduced growth rates and poor health conditions. The inclusion of yucca extract is recognized as a practical solution for adsorbing the waterborne ammonia. Yucca has abundant amounts of polyphenolics, steroidal saponins, and resveratrol and can be used as a solution or as a powder. In this context, this review aimed to investigate the possible regulatory roles of yucca extract on aquatic animals’ performances. Concurrently, the feed utilization, growth performance, and physiological status of aquatic species can be improved. Additionally, the yucca application resulted in enhancing the antioxidative, immunological, and anti-inflammatory responses in several aquatic animals. Exclusively, the present review proposed a protective solution through the application of yucca extract in the aquafeed and rearing water of aquatic animals suffering from ammonia accumulation. Furthermore, it shows how yucca could enhance the growth, survival rates, blood biochemical quality, immunological indices, and the antioxidative capacity of aquatic animals in light of the relevant published data.

Comparative study on the effect of dietary β-carotene and phycocyanin extracted from Spirulina platensis on immune-oxidative stress biomarkers, genes expression and intestinal enzymes, serum biochemical in Nile tilapia, Oreochromis niloticus

The current trial investigated the roles of β-carotene and phycocyanin extracted from Spirulina platensis on growth, serum biochemical, digestive enzymes, antioxidant defense, immune responses, and immune gene expression in Nile tilapia (Oreochromis niloticus). Fish (1.52 ± 0.10 g) were randomly stocked to three treatments with three replicates (12 fish per replicate) in nine aquaria (60 L glass aquarium for each), and reared for 70-days. Three tested diets were formulated to be isonitrogenous and isolipidic, and were offered for experimental fish until ad-libitum three times daily at 09:00 a.m., 11.00 a.m. and 3:00 p.m. The first diet (control) was without supplementation. About 50 mg β-carotene and 50 mg phycocyanin kg^-1 were supplemented to the other experimental diets, respectively. Results indicated that feed intake was not (P > 0.05) differ among experimental diets. Compared to control diet wight gain and specific growth rate were significantly (P < 0.05) in fish fed diet containing β-carotene, while, the highest weight gain and the best FCR were detected in phycocyanin diet. Survival fish among treatments was significantly (P < 0.05) differ and the highest survival rate was showed in fish fed diet supplemented with phycocyanin. Either β-carotene or phycocyanin significantly (P < 0.05) improved the intestinal digestive enzymes compared with control diet, where the highest values of chymotrypsin, trypsin, lipase and amylase were noticed in fish fed phycocyanin. Diets supplemented with β-carotene and phycocyanin significantly (P < 0.05) improved hematology parameters contents compared with to the control diet, and the best contents were detected in fish fed diet supplemented with phycocyanin. The highest significant (P < 0.05) phagocytic, lysozyme, immunoglobulin M (IgM), superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx) and total antioxidant capacity (T-AOC) activities were recorded in diet supplemented with phycocyanin. The transcripts of interferon gamma and interleukin 1β genes were (P < 0.05) up-regulated in the liver of fish fed diet supplemented with β-carotene and phycocyanin, but expression of HSP70 gene down-regulated in fish fed β-carotene and phycocyanin containing diet compared control. The highest gene expression of the interferon gamma and interleukin 1β was observed in fish fed phycocyanin.

Effects of dietary Nannochloropsis oculata on growth performance, serum biochemical parameters, immune responses, and resistance against Aeromonas veronii challenge in Nile tilapia (Oreochromis niloticus)

The current work was planned to assess the effects of dietary microalga, Nannochloropsis oculata (NP) on the growth indices, serum biochemistry, non-specific immunity, and resistance of Nile tilapia (Oreochromis niloticus) juveniles against challenge with pathogenic Aeromonas veronii. Fish (10.21 ± 0.28 g) were randomly divided into four treatments in triplicates and were fed on diets supplemented with different levels of NP (0, 5, 10, and 15%) for eight weeks. The results showed that the dietary 5% NP significantly improved the growth parameters (final body weight, weight gain, specific growth rate, and total feed intake) (P < 0.05). Meanwhile, the feed conversion ratio was significantly decreased in NP-supplemented groups with respect to the control group. The serum protein profile (total protein, albumin, globulin, and albumin/globulin ratio) was significantly decreased by 15% NP supplemented group. Meanwhile, liver enzymes (alanine transaminase, and aspartate transaminase) activities were not significantly affected by NP dietary supplementation (P < 0.05). Serum lysozyme activity, nitric oxide (NO), and nitroblue tetrazolium (NBT) levels were significantly enhanced only in 5% NP supplemented group (P < 0.05). Interestingly, the hepatopancreatic and intestinal tissues had apparently normal histomorphology of Nile tilapia fed at 5% NP-supplemented diets. Significant upregulation of cytokines [interleukin 1beta (IL-1β), interleukin 8 (IL-8), interferon-gamma (IFN-γ), transforming growth factor-beta (TGF- β), and tumor necrosis factor-alpha (TNF-α)], with significant downregulation of the antioxidant gene [superoxide dismutase (SOD)] in 10% and 15% NP supplemented groups. Attractively, the relative level of protection (RLP) against challenge with pathogenic A. veronii was significantly elevated in 10% and 15% NP supplemented groups. Conclusively, the obtained results reflect the beneficial roles of dietary NP to improve growth and boost the immune responses of Nile tilapia.

Supplementation of AQUAGEST ® as a Source of Medium-Chain Fatty Acids and Taurine Improved the Growth Performance, Intestinal Histomorphology, and Immune Response of Common Carp ( Cyprinus carpio ) Fed Low Fish Meal Diets

Four diets were prepared to include a mixture of medium-chain fatty acids and taurine as a digestive/ metabolic enhancer (DME, AQUAGEST®) at 0, 1, 2, and 3 g DME/kg diet and fed to common carp (initial weight, 4.55±0.03 g) for 70 days. Dietary DME significantly increased the final weight, weight gain, specific growth rate, feed intake, and protein efficiency and decreased feed conversion ratio in a dose-dependent manner (P<0.05). The body lipid composition was significantly improved by feeding DME at 2 g/kg diet (P=0.0141). The intestine villus length and the number of goblet cells were significantly increased in fish fed 2 g DME/kg diet (P<0.05). The intestinal villi displayed increased length, branching, and density by supplementing DME to common carp diets. Fish fed DME at 2 g/kg diet displayed markedly decreased aspartate aminotransferase (AST) and alanine aminotransferase (ALT ) (P=0.025 and P=0.043) and increased total protein and globulin (P =0.002 and P=0.003). Additionally, fish fed 2 and 3 g DME/kg levels displayed significantly increased albumin levels (P=0.006). Lysozyme and phagocytic activities were increased by feeding DME at 2 g/kg diet, while the phagocytic index increased by 2 and 3 g/kg diet (P<0.05). The optimal supplementation level of DME is 1.63 to 2.05 g/kg for common carp based on the polynomial regression analysis. In conclusion, common carp fed diets with a mixture of medium-chain fatty acids and taurine displayed improved growth, digestion activity, and immune response.

Assessing the Impact of Purslane ( Portulaca oleracea L.) on Growth Performance, Anti-Oxidative, and Immune Activities in Grass Carp ( Ctenopharyngodon idella )

In this study, the basal diet was supplemented with ethanolic extract of purslane (Portulaca oleracea L.) and the possible effects on growth performance, anti-oxidative, and immune activities of grass carp were evaluated. Fish with initial weight 1.23 ± 0.11 g were randomly divided into four groups (triplicates) and fed purslane extract at 0% (T0), 0.5% (T1), 1% (T2), and 1.5% (T3) for 56 days. At the end of the feeding trial, the results showed that growth parameters were enhanced in T1 groups compared to the control group (P<0.05). Lipase activity in T1 and T2 groups increased, whereas no significant changes were noticed in cases of amylase and protease activities (P>0.05). Catalase and superoxide dismutase activities were enhanced in all groups fed the supplemented diets in comparison with the control group (P<0.05). However, no significant alteration was noticed in the case of glutathione peroxidase activity following the administration of purslane extract (P>0.05). A significant increase in total immunoglobulin level was noted in the T1 group, but lysozyme activity was higher in T1 and T2 groups compared to the control group (P<0.05). In conclusion, supplementation of grass carp diet with the purslane ethanolic extract, especially at 0.5%, can improve growth performance, lipase activity, the antioxidant enzyme activities as well as the immune response of grass carp fingerlings.

Dietary origanum essential oil improved antioxidative status, immune-related genes, and resistance of common carp (Cyprinus carpio L.) to Aeromonas hydrophila infection

The use of herbal essential oils in aquafeeds is an important approach to maintain the fish health status. The origanum essential oil (OEO), extracted from Origanum vulgare, was included at levels of 0, 5, 10, 15, and 20 g per kg diet to evaluate its beneficial effects on antioxidant, immunity status, and expression of immune-related genes of common carp, Cyprinus carpio L. After 8 weeks, dietary inclusion of OEO significantly increased the activities of hepatic superoxide dismutase and catalase (P < 0.05); meanwhile, levels of hepatic malonaldehyde significantly decreased (P < 0.05). The levels of serum lysozyme activity, phagocytic activity, and phagocytic index have been linearly and quadratically increased by dietary OEO in a dose-dependent regime showing their highest levels in 15-20 g OEO/kg diet. Moreover, dietary OEO significantly upregulated the relative expression of hepatic interleukin-1beta (IL-1β) and interleukin-10 (IL-10) genes (P < 0.05). Dietary OEO maintained the normal histomorphological criteria and density of melanomacrophage centers of spleens, and hematopoietic tissues of the anterior kidneys in all fish groups with respect to the control. After challenge with pathogenic bacterium Aeromonas hydrophila, the 10-day cumulative mortality significantly decreased (P < 0.05); meanwhile, the relative percent of survival of common carp significantly increased by OEO administration (P < 0.05) in a dose-dependent manner. The obtained results reflect the beneficial roles of dietary OEO to boost the antioxidative status and the immune responses in common carp with an optimum level of 15 g/kg diet.