Plant extract-based diets differently modulate immune responses and resistance to bacterial infection in striped catfish (Pangasianodon hypophthalmus)

Polyphenol-rich extracts enhance growth, immune function, and antioxidant defense in juvenile rainbow trout (Oncorhynchus mykiss)

Introduction

The present study was conducted to investigate the effects of PMIX, a polyphenol-rich extract mixture from chestnut wood and olive, on growth performance, hematological parameters, immunity in serum and skin mucus, hepatic antioxidant enzymes, and intestinal cytokine expression in rainbow trout (Oncorhynchus mykiss).

Methods

Four experimental diets containing 0 g PMIX kg-1 diet (control, C), 0.5 g PMIX kg-1 diet (P0.5), 1 g PMIX kg-1 diet (P1), and 2 g PMIX kg-1 diet (P2) were fed to rainbow trout in an eight-week feeding trial. Triplicate groups of fish received each treatment. Growth performance, feed conversion ratio, protein efficiency, hepatosomatic and viscerosomatic indices, hematological parameters, immunity markers, hepatic antioxidant enzyme activities, and intestinal cytokine expression were determined.

Results

PMIX supplementation significantly improved feed conversion ratios, while groups P0.5 and P1 evidenced an increase in growth performance along with protein efficiency ratios. It also showed decreased hepatosomatic and viscerosomatic indices in the P1 group. Except for higher percentages of monocytes in P0.5 and P1, most hematological parameters of the fish did not differ from that of the control. Serum lysozyme and respiratory burst activities were heightened in all PMIX-treated groups, and the skin mucus lysozyme activity was enhanced in P1. The blood phagocytic activity and phagocytic index, serum immunoglobulin, total protein, and bactericidal activity against A. hydrophila did not change. Hepatic superoxide dismutase activity significantly increased in P1 and P2, even though catalase activity did not change. Intestinal interleukin-6 expression was upregulated in all PMIX-treated groups, while tumor necrosis factor-alpha and interleukin-1 beta were upregulated in P1, P2, and P0.5 respectively.

Discussion

The present results evidence that dietary polyphenols from chestnut wood and olive extracts enhance growth performance, antioxidant capacity, and several immunological parameters in the blood, skin mucus, and intestine of rainbow trout. A suitable supplementation level was 1 g PMIX kg-1 diet to separate these improvements.

The effect of dietary administration of Saussurea lappa root on performance, blood biochemical indices, redox status, innate immune response, intestinal microbial population and resistance against A. hydrophila infections of Tilapia Fingerlings

This experiment was performed to identify the influence of dietary Saussurea lappa root (SLR) on the performance and general health status of Nile Tilapia fingerlings (O. niloticus). Four formulated diets with different SLR levels of 0.0, 2.5, 5 and 10 g/kg, respectively, were afforded to fingerling fish (15.42 ± 0.05 g) for 8 weeks. The feed efficiency ratio (FER), feed intake (FI) and feed conversion ratio varied with dietary SLR level in a linear model and a high feed efficiency rate was recorded at the 10 g/kg group, while FI and FCR exhibited an opposite trend (P < 0.001). Dietary SLR level influenced serum protein constituents, liver and renal function enzymes, triglycerides, cholesterol and glucose (P < 0.001). Serum Catalase (CAT), total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) remarkedly increased with dietary SLR level and attained a level at 10 g/kg. Furthermore, serum lysozyme, complement C3 (C3), IgA and IgD were stimulated by 10 g/kg SLR. Intestinal digestive enzymes (lipase and amylase) increased with SLR level up to 10 g/kg. As the dietary SLR level raised, the cumulative survival percentage aginst A. hydrophila challenge increased and then reached a maximum at 10 g/kg SLR group. Moreover, gene expression of pro-inflammation cytokines (TNF-2a, IL-1β, and IL-10) in liver and kidney transcriptomes demonstrated effective immunostimulant capabilities of greater SLR inclusion levels in fish diet. Meanwhile, intestinal microbial investigation, revealed that high levels of SLR in tilapia fish feed significantly suppressed total bacterial count, and pathogenic bacterial count (such as, E. coli, Coliform, Aeromonas spp, Pseudomonas spp.), and stimulated lactic acid bacteria development. Finally, it is recommended to include a high level of SLR (5 or 10 g/kg) in the diet of O. niloticus fingerlings to enhance feed efficiency, antioxidant characteristics, and immunological response against bacterial infections.

Cyrtocarpa edulis fruit and its immunostimulant effect on Almaco Jack Seriola rivoliana: in vitro, in vivo and ex vivo studies

The present study investigates for the first time chemical, proximate analyses and immunostimulant effect of Cyrtocarpa edulis fruit (CeF). Three design experiments were carried out to evaluate immunostimulant effect of C. edulis fruit: in vitro, in vivo and ex vivo studies in juveniles Almaco jack Seriola rivoliana. In general, nutraceutical studies performed by gas chromatography/mass spectrometry (GC-MS) in CeF revealed a major quantity of the carbohydrate groups and phytosterols such as β-sitosterol. Their phytochemical and antioxidant values exposed a significant content of total phenols, flavonoids, and tannins, showing an antioxidant capacity against hydroxyl and superoxide radical. The in vitro results confirm that CeF is edible and enhanced the innate immune response in head-kidney leukocytes after 24 h of immunostimulation. The in vivo results showed that myeloperoxidase, nitric oxide production, as well as antioxidant enzymes were enhanced in skin mucus of those fish fed with CeF. Interestingly in the intestine, IL-β, TNF-α, MARCO and Piscidin gene expression were up-regulated in fish fed with C. edulis after 4 weeks. Finally, ex vivo experiments showed an important enhancement on cellular parameters (phagocytosis, respiratory burst, myeloperoxidase, and nitric oxide production) in head-kidney leukocytes of fish fed CeF and intraperitoneally infected with A. hydrophila. The results demonstrate that C. edulis fruit (0.5%) represents an available phytochemical and antioxidant rich alternative with great potential as fish immunostimulant additive.

Impacts of astaxanthin-enriched Paracoccus carotinifaciens on growth, immune responses, and reproduction performance of broodstock Nile tilapia during winter season

The growth, immune response, and reproductive performance of broodstock of Nile tilapia (Oreochromis niloticus) under winter stress conditions were investigated the effects of supplementary diets with astaxanthin-enriched Paracoccus carotinifaciens. Throughout an eight-week period in the winter season, male and female tilapia were fed with diets containing different levels of P. carotinifaciens dietary supplementation: 0 g/kg (T1; control), 5 g/kg (T2), 10 g/kg (T3), and 20 g/kg (T4). Subsequently, a four-week mating system was implemented during the winter stress period. The results revealed that there were no significant differences observed in growth, hematological indices, and blood chemical profiles among all treatment groups for both male and female tilapia. However, a significant increase in cholesterol content was noted in both male and female tilapia fed with the T4 diet (p<0.05). The total carotenoid content in the muscle was evaluated, and significantly higher values were found in both male and female tilapia that fed T4 supplementation (p<0.05). Moreover, immunological parameters such as myeloperoxidase and antioxidant parameters in the liver including superoxide dismutase activity and catalase enzyme activity showed significant increases in tilapia fed with the T4 diet. The impact of P. carotinifaciens supplementation on broodstock tilapia indicated a significant increase in spermatozoa concentration in males and increased egg production in females after consumption of the T4 diet (p<0.05). Thus, this study highlighted that the presence of astaxanthin-enriched P. carotinifaciens in the diet of broodstock Nile tilapia can lead to the accumulation of carotenoids in their muscle tissue, improvement in antioxidant status, enhancement of immune function, and potential enhancement of reproductive capabilities, even under overwintering conditions.

Effects of Dietary Phytol Supplementation on Growth Performance, Immunological Parameters, Intestinal Bacteria, and Prevention of Oxidative Stress Following Transportation of Nile Tilapia, Oreochromis niloticus

Nile tilapia, Oreochromis niloticus, (2.00 ± 0.02 g) were reared in 16 70-L tanks (40 individual/tank) and fed diets (approx. 345 g/kg protein, approx. 87 g/kg crude fat) containing 0 (CTL), 75 (PH-75), 150 (PH-150), and 300 (PH-300) mg/kg phytol (n = 4). After 60 days of feeding (4% daily), growth performance, humoral immune parameters, and gut bacteria were analyzed. Also, hepatic antioxidant parameters were determined before and after the fish were transported in plastic bags for 6 hr. The results showed that PH-75 exhibited the highest final weight (P < 0.001), weight gain (P < 0.001), feed intake (P < 0.001), feed efficiency (P=0.015), plasma lysozyme activity (P=0.004), and intestinal Lactobacillus sp. population (P=0.017), among the treatments. The highest plasma alternative complement activity (P=0.006) and the lowest intestinal total viable bacteria (P=0.027) were observed in PH-75 and PH-150. The highest plasma alkaline phosphatase activities were observed in PH-75 and PH-300 (P=0.014). The highest blood leukocyte (P=0.008), monocyte (P=0.010), and eosinophil (P < 0.001) were observed in PH-300, while the highest blood neutrophil was observed in all phytol treatments (P < 0.001). The highest hepatic lipid peroxidation was observed in PH-300, whereas PH-75 and PH-150 showed the lowest values (P < 0.001). The highest hepatic reduced glutathione was observed in PH-75, also PH-150 exhibited significant elevation in this parameter, compared to CTL (P < 0.001). Transportation led to significant elevations in the hepatic antioxidant enzymes' activities in CTL, PH-75, and PH-150; the highest activities were related to PH-75 and PH-150 treatments, which had also the highest post-transportation survivals (P < 0.001). In conclusion, phytol is a suitable feed supplement for Nile tilapia, improving growth performance and welfare, particularly at 75 mg/kg.

Effects of Dietary Tuber Ethanolic Extract of Nut Grass (Cyperus rotundus Linn.) on Growth, Immune Response, and Disease Resistance in Nile Tilapia (Oreochromis niloticus)

Nut grass (Cyperus rotundus Linn.) is a weed that grows in all tropical, subtropical and temperate regions of the world, including areas where it grows on saline soil. This research was conducted to evaluate the effect of C. rotundus tuber extract in the diet on the growth performance and disease resistance of Nile tilapia. Various components of phytochemical importance of nut grass, including sugars/carbohydrates, terpenoids, tannins, and flavonoids were found in C. rotundus. Tilapia (n = 25 fish/group in triplicate) were fed with different levels of nut grass extract including 0 (control; T1), 0.4 (T2), 0.8 (T3), and 1.6 (T4) g/kg for 60 days in a completely randomized design (CRD) experiment. After the feeding trial, the highest weight gain and average daily gain (ADG) were observed in the T4 group, but it was not significantly different from T3 (Nile tilapia fed with a 0.8 g/kg) (p > 0.05). The lowest feed conversion ratio (FCR) was observed in the T3 group. Moreover, the fillet, crud lipid content, and blood chemical profiles (aspartate aminotransferase (AST), cholesterol, and malondialdehyde (MDA)) in fish fed with 1.6 g/kg were highest when compared in all groups. In addition, the T3 group presented with the immune response parameter found in red blood cells (RBC), lysozyme activity, and antioxidant (superoxide dismutase activity (SOD)) being higher than those of the control group (p < 0.05). The highest survival (93.33%) was observed in fish fed with 0.8 g/kg (T3) after a 14 day challenge with Streptococcus agalactiae. Thus, it was concluded that nut grass extract at 0.8 g/kg can be used to improve the growth performance and the tendency for resistance to S. agalactiae in Nile tilapia.

Investigation of dietary exogenous protease and humic substance on growth, disease resistance to Flavobacterium covae and immune responses in juvenile channel catfish (Ictalurus punctatus)

Many bacterial pathogens impact the US catfish industry, and disease control can be challenging for producers. Columnaris disease in channel catfish, Ictalurus punctatus, is primarily caused by Flavobacterium covae (formerly F. columnare). Immunostimulants may enhance nonspecific immune responses and offer an alternative to antibiotic treatments in catfish. Furthermore, dietary protein sources and inclusions are also essential to fish health and nutrition and may enhance overall fish performance in pond culture. The current project evaluated two immunostimulants: a protease complex (PC) and a humic substance (HS) derived from a reed-sedge peat product. A 60-day trial examined the effects of five diets on growth performance, immune response and resistance to experimental F. covae infection in channel catfish. Diets included a high-quality fishmeal diet (32%; CF32), a high-protein soy-based diet (32%; C32), a low-protein soy-based diet (28%; C28; predominately used in industry), a low-protein soy diet supplemented with C28 + PC at 175 g metric ton^-1 and C28 + HS in a low-protein diet at 23 g metric ton^-1 . Following feeding for 60 d, juvenile channel catfish were sampled for growth performance and baseline health indicators (n = 3; body mucus, blood for sera, kidney and spleen). A subset of fish was then subjected to an immersion-based in vivo challenge trial with F. covae (ALG-00-530; 10⁶  CFU mL^-1 exposure). At 60d post-initiation, there were no dietary differences in the relative growth rate (p = .063) or thermal growth coefficient (p = .055), but the 32% diets generally appeared to perform best. Post-challenge, the C32 group's mortality was higher than the C28 + PC (p = .006) and C28 + HS diets (p = .005). Although not significant, the C28 and CF32 groups also demonstrated higher mortality compared to both PC and HS diets. Sera lysozyme concentration was found to increase following pathogen challenge (p < .001) and in comparison with mock-challenged catfish (p < .001). Elevated expression levels of proinflammatory cytokines (il-1β, il-8, tnf-α and tgf-β) were observed at trial midpoint and post-infection when compared to 60d. The C28 treatment was found to have lower tnf-α expression than the C28 + PC (p = .042) and C28 + HS (p = .042) groups following exposure to F. covae. These challenge data suggest that the immunostimulants (PC and HS) in plant-based protein may be beneficial in protecting against F. covae when offered in low-protein channel catfish diets.

Psidium guajava L.- dichloromethane and ethyl acetate fractions ameliorate striped catfish (Pangasianodon hypophthalmus) status via immune response, inflammatory, and apoptosis pathways

Psidium guajava L. is known to possess immune-modulatory properties in humans and other mammals. Although the positive effects of P. guajava-based diets on the immunological status have been shown for some fish species, the underlying molecular mechanisms of its protective effects remain to be investigated. The aims of this study were to evaluate the immune-modulatory effects of two guava fractions from dichloromethane (CC) and ethyl acetate (EA) on striped catfish with in vitro and in vivo experiments. Striped catfish head kidney leukocytes were stimulated with 40, 20, 10 and 0 μg/ml of each extract fraction, and the immune parameters (ROS, NOS, and lysozyme) were examined at 6 and 24h post stimulation. A final concentration of each fraction at 40, 10 and 0 μg/fish was then intraperitoneally injected into the fish. After 6, 24, and 72h of administration, immune parameters as well as the expression of some cytokines related to innate and adaptive immune responses, inflammation, and apoptosis were measured in the head kidney. Results indicated that the humoral (lysozyme) and cellular (ROS and NOS) immune endpoints were regulated differently by CC and EA fractions depending on dose and time in both, in vitro and in vivo experiments. With regards to the in vivo experiment, the CC fraction of the guava extract could significantly enhance the TLRs-MyD88-NF-κB signaling pathway by upregulating its cytokine genes (tlr1, tlr4, myd88, and traf6), following the upregulation of inflammatory (nfκb, tnf, il1β, and il6) and apoptosis (tp53 and casp8) genes 6 h after injection. Moreover, fish treated with both CC and EA fractions significantly enhanced cytokine gene expression including lys and inos at the later time points - 24h or 72h. Our observations suggest that P. guajava fractions modulate the immune, inflammatory, and apoptotic pathways.

Evaluation of immunostimulatory attributes of Asparagus racemosus and Withania somnifera supplemented diets in fish, Channa punctatus (Bloch, 1793)

With the progression of aquaculture industry, there has been a spurt in dietary supplementation with economically viable medicinal herbs having enough immunostimulatory potential. This also aids in avoidance of environmentally undesirable therapeutics that are almost inevitable to safeguard fish against an array of diseases in aquaculture practices. The study aims to determine the optimal dose of herbs that can stimulate substantial immune response in fish for reclamation of aquaculture. Immunostimulatory potential of the two medicinal herbs- Asparagus racemosus (Shatavari), Withania somnifera (Ashwagandha), individually, and in combination, with a basal diet was screened up to 60 days in Channa punctatus. 300 laboratory acclimatized healthy fish (14 ± 1 g; 11 ± 1 cm) were divided into ten groups- C, S1, S2, S3, A1, A2, A3, AS1, AS2, and AS3, based on the composition of dietary supplementation, in triplicates, with 10 specimens per group. The hematological index, total protein and lysozyme enzyme activity were performed after 30 and 60 days, while qRT-PCR analysis of lysozyme expression was done after 60 days of the feeding trial. The significant (P < 0.05) increments in hematological indices- (TEC, TLC, DLC, Hb, Hct, MCV, MCH and MCHC), total protein content and serum lysozyme activity, after 30 and 60 days; whereas upregulation of lysozyme transcript levels, both in liver and muscle tissues after 60 days of the feeding trial were recorded in groups- AS1, AS2, and AS3. The maximal increment in lysozyme expression was recorded in AS3, both in liver and muscle tissues, with 3.75 ± 0.13 and 3.21 ± 0.18-folds, respectively. However, increments were non-significant (P > 0.05) for MCV in AS2 and AS3 after 30 days; and for MCHC in AS1 for both the durations; whereas in AS2 and AS3, after 60 days of the feeding trial. A positive correlation (P < 0.05) among lysozyme expression, MCH, lymphocytes, neutrophils, total protein content, and serum lysozyme activity in AS3, after 60 days, conclusively, evinces that a 3% dietary supplementation with both A. racemosus and W. somnifera enhances immunity and health profile of the fish, C. punctatus. The study, thus finds ample scope in augmentation of aquaculture production and also paves the way for more researches for biological screenings of potential immunostimulatory medicinal herbs that can be appropriately incorporated in the fish diet.

Growth-promoting and immunostimulatory effects of phytobiotics as dietary supplements for Pangasianodon hypophthalmus fingerlings

A 56-day feeding experiment was designed to evaluate the impacts of five herbal extracts, namely Ginkgo biloba (GB), Moringa oleifera (MR), Myristica fragrans (NM), Silybum marianum (MT), and Astragalus membranaceus (AT) on growth, serum immune indices, and ammonia-N stress resistance of Pangasianodon hypophthalmus fingerlings. Fish were fed on a diet with no herbal additives (reference or CNT), and several plant extracts-based diets were supplied with two inclusion doses of each extract (1.0 and 2.0 g/kg). After the end of the feeding, fish in all groups were exposed to acute ammonia stress, mortalities were recorded every 2 h for a duration of 10 h, and then survival percent was assessed. Results showed that growth was upgraded significantly in groups fed plant extracts-based diets compared to the CNT group. Serum proteins (albumin and total protein), lysozyme, complement C3, bactericidal, and myeloperoxidase activities were increased significantly in groups fed plant extracts-based diets in relation to the CNT group. The total immunoglobulin levels were increased significantly only in fish groups fed GB, MT, and NM-based diets. Post-exposure to acute ammonia stress, the Kaplan-Meier survival curve presented significantly higher survival of fish groups that fed plant extracts-enriched diets than those fed the CNT diet. The aforementioned results suggest that using herbal extracts as feed supplements can beneficially enhance the growth, the immunity of P. hypophthalmus fingerlings and may increase their tolerance in the face of extrinsic stressors. These findings may pave the way for the potential and regular application of herbal extracts in diets of P. hypophthalmus at their early life stages to raise their immunity and maintain aquaculture sustainability.

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

Introduction

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

Methods

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

Results

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

Discussion

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

The Effects of Dietary Thyme Oil (Thymus vulgaris) Essential Oils for Common Carp (Cyprinus carpio): Growth Performance, Digestive Enzyme Activity, Antioxidant Defense, Tissue and Mucus Immune Parameters, and Resistance against Aeromonas hydrophila

This study evaluated the effects of dietary supplementation of thyme (Thymus vulgaris) essential oil (TVO) on growth performance, digestive enzymes, biochemical parameters, hematological indices, liver enzymes, and pathogen resistance in common carp (Cyprinus carpio). Triplicate groups of fish (15.36 ± 0.10 g) were fed daily with diets supplemented with TVO at 0, 0.5, 1, and 2 percent for 60 days then challenged with Aeromonas hydrophila. The results determined that supplementation of thyme resulted in significantly higher final body weights (FBW) and lower feed conversion ratios (FCR). Furthermore, no mortality was observed in the thyme-supplemented treatments. Regression analysis showed that fish growth parameters were polynomially related to dietary TVO levels. The optimum dietary TVO level, based upon the varied growth parameters, was 1.344 to 1.436%. Digestive enzymes activity, including amylase and protease, significantly increased in fish fed the supplemented diets. The thyme-supplemented diets also significantly increased the biochemical parameters, including total protein, albumin, and acid phosphatase (ACP), compared to the control group. We also observed significant increases in hematological indices, including red blood cells (RBC), white blood cells (WBC), hematocrit (Hct), and hemoglobin (Hb) in common carp fed diets containing thyme oil (P < 0.05). Liver enzymes activity including alanine aminotransferase (ALT), alkaline phosphatase (ALP), and aspartate aminotransferase (AST) was also reduced (P < 0.05). Immune parameters, including total protein and total immunoglobulin (total Ig) levels, alternative complement pathway hemolytic (ACH₅₀), lysozyme, protease, and ALP in the skin mucus, and lysozyme, total Ig, and ACH₅₀ in the intestine were higher (P < 0.05) in TVO-supplemented fish. Catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), and glutathione peroxidase (GPx) in the liver were also elevated (P < 0.05) in TVO administered groups. Lastly, thyme-supplementation resulted in higher survival rates after the A. hydrophila challenge compared to the control (P < 0.05). In conclusion, dietary inclusion of thyme oil (1 and 2%) effectively improved fish growth, immune systems, and resistance to A. hydrophila.

Influence of black rice (Oryza sativa L.) bran derived anthocyanin-extract on growth rate, immunological response, and immune-antioxidant gene expression in Nile tilapia (Oreochromis niloticus) cultivated in a biofloc system

This study investigated the effects of dietary supplementation with anthocyanin extracted from black rice bran (AR) on the growth rate, immunological response, and expression of immune and antioxidant genes in Nile tilapia raised in an indoor biofloc system. A total of 300 Nile tilapia fingerlings (15.14 ± 0.032 g) were maintained in 150 L tanks and acclimatized for two weeks. Five experimental AR diets (0, 1, 2, 4, and 8 g kg^-1) with various anthocyanin doses were used to feed the fish. We observed that the growth and feed utilization of fish fed with different dietary AR levels increased significantly after eight weeks (p < 0.05). In addition, the serum immunity of fish fed AR diets was much greater than that of those fed non-AR diets (p < 0.05). However, there were little or no difference in between fish fed AR enriched diets and the control AR-free diet (p > 0.05). After eight weeks, fish fed AR-supplemented diets had significantly higher mRNA transcript levels in immune (interleukin [IL]-1, IL-8, and liposaccharide-binding protein [LBP]) and antioxidant (glutathione transferase-alpha [GST-α] and glutathione reductase [GSR]) genes compared to control fish fed the AR-free diet, with the greatest enhancement of mRNA transcript levels (in the case of IL-8 by up to about 5.8-fold) in the 4 g kg^-1 AR diet. These findings suggest that dietary inclusion of AR extract from black rice bran at 4-8 g kg^-1 could function as a herbal immunostimulant to enhance growth performance, feed consumption, and immunity in Nile tilapia.

Insights into the mechanisms of tris(2-chloroethyl) phosphate-induced growth inhibition in juvenile yellow catfish Pelteobagrus fulvidraco

With the gradual elimination of brominated flame retardants (BFRs), the production and application of tris (2-chloroethyl) phosphate (TCEP), as a substitute of BFRs, has increased greatly. The objective of the present study was to comprehensively explore the potential adverse effects of TCEP on fish growth and the possible underlying mechanisms. To this end, juvenile yellow catfish (Pelteobagrus fulvidraco) were exposed to environmentally relevant concentrations of TCEP (0, 1, 10 and 100 µg/L) for 30 days. The results showed that exposure to high concentrations of TCEP (10 and 100 µg/L) significantly decreased body weight, body length and specific growth rate (SGR). Plasma IGF-I levels and hepatic mRNA levels of igf1 and igf1r were all reduced, while the transcriptional levels of IGFBPs (igfbp2, igfbp3, igfbp5) were significantly up-regulated in the liver of yellow catfish under exposure to 10 and 100 µg/L TCEP. TCEP-induced growth inhibition might be related to somatostatin (SS) signaling system, as evidenced by elevated mRNA transcriptions of ss in brain and its receptors (sstr2, sstr3, sstr5) in liver. In addition, fish exposed to high concentrations of TCEP displayed multiple histological alterations in liver. Taken together, these findings suggested that TCEP (>10 µg/L) might exert its inhibitory effect on fish growth through interfering with the GH/IGF axis and SS signaling system, and by impairing hepatic structures.

Bioprospecting for Anti-COVID-19 Interventions From African Medicinal Plants: A Review

The emergence of the novel coronavirus (SARS-CoV-2) that emanated from Wuhan in China in 2019 has become a global concern. The current situation warrants ethnomedicinal drug discovery and development for delivery of phytomedicines with potential for the treatment of COVID-19. The aim of this review is to provide a detailed evaluation of available information on plant species used in African traditional medicines with antiviral, anti-inflammatory, immunomodulatory, and COVID-19 symptoms relieving effects. Literature from scientific databases such as Scopus, PubMed, Google scholar, African Journals OnLine (AJOL), Science Direct, and Web of Science were used for this review. A total of 35 of the 38 reviewed plants demonstrated a wide range of antiviral activities. Bryophyllum pinnatum, Aframomum melegueta, Garcinia kola, Sphenocentrum jollyanum, Adansonia digitata, Sutherlandia frutescens, Hibiscus sabdariffa, Moringa oleifera, and Nigella sativa possess a combination of antiviral, immunomodulatory, anti-inflammatory, and COVID-19 symptoms relieving activities. Nine, 13, and 10 of the plants representing 23.7%, 34.2%, and 26.3% of the plants studied had antiviral activity with 3 other activities, antiviral activity with 2 other activities, and antiviral with one pharmacological activity alone, respectively. The plants studied were reported to be relatively safe at the subchronic toxicity level, except for 2. The study provides baseline information on the pharmacological activities, toxicity, and chemical components of 9 African medicinal plants with antiviral, immunomodulatory, anti-inflammatory, and symptoms relieving activities, thereby making the plants candidates for further investigation for effectiveness against COVID-19.

Effects of dietary rambutan (Nephelium lappaceum L.) peel powder on growth performance, immune response and immune-related gene expressions of striped catfish (Pangasianodon hypophthalmus) raised in biofloc system

This study aimed to evaluate the effects of rambutan peel powder (RP) on growth, skin mucosal and serum immunities, and immune-related gene expression of striped catfish (Pangasianodon hypophthalmus) reared in a biofloc system. Three hundred fingerlings (17.14 ± 0.12 g fish^-1) were randomly selected and assigned to five treatments corresponding to five diets: 0 g kg^-1 (control - RP0); 10 g kg^-1 (RP10); 20 g kg^-1 (RP20); 40 g kg^-1 (RP40), and 80 g kg^-1 (RP80) for 8 weeks. At weeks 4 and 8 post-feeding, growth, skin mucus, and serum immunity parameters were determined, whereas immune-related gene expressions were performed at the end of the feeding trial. Based on the results, skin mucus lysozyme (SML) and skin mucus peroxidase (SMP) were significantly higher in fish fed the RP diets compared to the control diet (P < 0.05). The highest SML and SMP levels were observed in fish fed RP40 diet, followed by RP20, RP80, RP10, and RP0. Fish-fed RP diets had higher serum lysozyme and serum peroxidase activities, with the highest value found in the RP40 diet (P < 0.05), followed by RP20, RP80, and RP10. Similarly, immune-related gene expressions (IFN2a, IFN2b, and MHCII) in the liver were significantly up-regulated in fish fed RP40. Up-regulation (P < 0.05) of IL-1, IFN2a, IFN2b, and MHCII genes was also observed in fish intestines, with the highest values observed in fish fed RP40 diet, followed by RP10, RP20, RP80, and RP0. Fish-fed diet RP diets also showed enhanced growth and FCR compared to the control, with the highest values observed in fish fed diet RP40. However, no significant differences in survival rates were found among diets. In conclusion, dietary inclusion of RP at 40 g kg^-1 resulted in better growth performance, immune response, and immune related gene expressions of striped catfish (Pangasianodon hypophthalmus).

Impacts of Aegle marmelos fruit extract as a medicinal herb on growth performance, antioxidant and immune responses, digestive enzymes, and disease resistance against Streptococcus agalactiae in Nile tilapia (Oreochromis niloticus)

An experiment was conducted to investigate the effects of Aegle marmelos fruit (AMF) extract on the growth performance, biochemical parameters, immune response, antioxidative capacity, and digestive enzyme activity of Nile tilapia (Oreochromis niloticus). Fish were fed a diet supplemented with AMF at concentrations of 0 (AMF0; control), 5 (AMF5), 10 (AMF10), 15 (AMF15), or 20 (AMF20) g/kg for 8 weeks. The results show that the final body weight, weight gain, specific growth rate, average daily gain, and feed conversion ratio were significantly higher in fish fed AMF15 and AMF20 compared to those fed the control diet (P < 0.05). Moreover, significant increases in antioxidant enzyme activities and non-specific immune responses were observed in groups fed AMF15 and AMF20. Interestingly, the level of cholesterol decreased with increasing AMF concentrations in the diet. As dietary AMF levels increased, digestive enzyme activities significantly improved. After the feeding trial, fish were injected intraperitoneally with Streptococcus agalactiae, and the 14-day cumulative mortality was calculated. A high survival rate after challenge with S. agalactiae was observed in all groups that received AMF-supplemented feed. Therefore, the present study suggests that supplementing the diet of Nile tilapia with AMF at a concentration of 20 g/kg could encourage their growth, improve their immunity and antioxidant status, and provide strong protection against S. agalactiae.

Dietary Guduchi (Tinospora cordifolia) enhanced the growth performance, antioxidative capacity, immune response and ameliorated stress-related markers induced by hypoxia stress in Nile tilapia (Oreochromis niloticus)

Nile tilapia can tolerate a wide range of farming conditions; however, fluctuations in the environmental conditions may impair their health status. The incorporation of medicinal herbs in aquafeed is suggested to overcome stressful conditions. In this study, dietary Guduchi (Tinospora cordifolia) was evaluated on the growth performance, antioxidative capacity, immune response, and resistance of Nile tilapia against hypoxia stress. Fish fed five diets incorporated with Guduchi at 0, 2, 4, 6, and 8 g/kg for 56 days then exposed with hypoxia stress for 72 h. The growth performance, feed intake, and feed efficiency ratio were significantly (P < 0.05) increased by including Guduchi in tilapia diets regardless of the inclusion level. Similarly, the lipase and protease activities were markedly (P < 0.05) increased in tilapia fed dietary Guduchi. The activities of lysozyme and bactericidal activities in serum and mucus, nitro-blue tetrazolium (NBT), and alternative complement activity (ACH50) were markedly (P < 0.05) enhanced in tilapia treated with Guduchi supplements regardless of the dose. Additionally, the activities of liver and intestinal superoxide dismutase, catalase, and glutathione peroxidase were markedly enhanced (P < 0.05) by including Guduchi in tilapia diets compared with the control. Before and after hypoxia stress, tilapia-fed dietary Guduchi had lower glucose and cortisol levels than fish-fed Guduchi-free diets (P < 0.05). In all groups, glucose and cortisol levels were markedly higher after hypoxia compared before hypoxia stress (P < 0.05). In conclusion, dietary Guduchi can be included at 5.17-5.49 g/kg to enhance the growth performance, digestive enzyme activity, immune and antioxidative responses, and the resistance of Nile tilapia against hypoxia stress.

Differentially expressed genes involved in immune pathways from yellowhead catfish (Tachysurus fulvidraco) after poly (I:C) challenge

Yellowhead catfish (Tachysurus fulvidraco) is an important aquaculture fish species in China with a high market value. Infectious diseases pose serious threats in farmed fish species, and although vaccines can prevent certain infections, they rely on potent adjuvants. In this study, we analyzed the transcriptomic profiles of spleens from poly (I:C)-treated T. fulvidraco. We obtained 46,362,922 reads corresponding to 490,926 transcripts and 318,059 genes. Gene annotation using different databases and subsequent differential gene expression analyses led to the identification of 5587 differentially expressed genes (DEGs), of which 2473 were up-regulated and 3114 were down-regulated in poly (I:C)-treated fish. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses of DEGs revealed the significant dysregulation of immune- and cancer-related genes in the spleens of poly (I:C)-treated fish. Notably, several components of JAK-STAT, MAPK, and p53 signaling pathways were significantly dysregulated in response to poly (I:C) treatment. Quantitative real-time PCR (qRT-PCR) analysis of 11 randomly selected immune response genes confirmed the reliability of our findings. In conclusion, our findings provide novel insight into the immune responses of T. fulvidraco and suggest that poly (I:C) may represent a promising adjuvant of fish vaccines.

Effects of dietary white mulberry leaves on hemato-biochemical alterations, immunosuppression and oxidative stress induced by Aeromonas hydrophila in Oreochromis niloticus

The present work was designed to assess the potential hemato-biochemical protective action, immunemodulatory and antioxidant conclusions of varied concentration of white mulberry Morus alba leaves (MAL) extract supplementation on Nile tilapia (Oreochromis .niloticus). A total two hundred and forty of O. niloticus were haphazardly sorted into four groups. The control (CT) group was fed on basal diet. A group MAL₁, MAL₃ and MAL₅ was fed on 1, 3 and 5 g/kg MAL respectively for thirty days. On day thirty one, half of replicates in each group were challenged by 0.5 ml × 10⁸Aeromonas hydrophila where, the residual replicates were kept without challenge. A. hydrophila challenged tilapias revealed anemia that alleviated by supplementation with 5 g/kg MAL also, recovers the shift of leucogram prompted by the challenge. Elevation of alkaline phosphatase, aminotransferases, lactate dehydrogenase and malondialdehyde (ALP, ALT, AST, LDH and MDA) in CT, MAL₁ and MAL₃ in the challenged replicates respectively where within normal at MAL₅. Supplementation with MAL₅ showed more potent antioxidant and immune reaction than MAL₁ and MAL₃. There were a rapid increase of immunoglobulin M, lysozymes, nitric oxide, catalase and superoxide dismutase and their allied genes expression (IgM, CAT and SOD) in MAL groups with contrast in CT challenged groups. Where in challenged groups, there was suppression in genes expression of interleukins (8 and 1 beta) and interferon ɤ (IL8. IL-1β and INFɤ). Tilapias challenged by A. hydrophila unveiled plentiful surge in the percentage of mortality in CT challenged fish (80%), followed by the groups supplemented with MAL₁ and MAL₃ were (73.33%) where MAL₅ was 20%. The mortalities have been halted from the 6^th, 13^th, 14^th and 15^th days in, MAL₅, MAL₃, MAL₁, and CT correspondingly. These previous results could be fulfilled that using of MAL 5 g/kg protect tilapias from hemato-biochemical alterations and enhance its immune feedback, antioxidant defense and resistance against A. hydrophila.

Immunomodulatory potential of extracts, fractions and pure compounds from Phyllanthus amarus and Psidium guajava on striped catfish (Pangasianodon hypophthalmus) head kidney leukocytes

This study aimed to identify major phytochemical constituents, as well as compare the immunomodulatory effects of Psidium guajava L. and Phyllanthus amarus Schun and Thonn crude ethanol extracts and their fractions on striped catfish (Pangasianodon hypophthalmus) head kidney leukocytes (HKLs). Moreover, pure constituents were also investigated for their effects on those cells: hypophyllanthin, identified as a major constituent of P. amarus crude extracts and its hexane fraction; corosolic acid, ursolic acid, and oleanolic acid, identified in P. guajava crude extract, ethyl acetate and dichloromethane fractions; with other terpenic derivatives, as well as guajaverin and avicularin, identified with other flavonoids by LC-UV-MS in the crude P. guajava extract and its ethyl acetate fraction. Cell viability, respiratory burst assay (RBA), nitric oxide synthase (NOS) and lysozyme activity in HKLs were analyzed after 24 h stimulation with each extract (10, 20 and 40 μg/mL) or pure compound (7.5, 15 and 30 μM). Our results show that the hexane fraction of both plant extracts inhibited the viability of HKLs, while several other fractions enhanced the cell viability. All P. guajava fractions at all or some concentration considerably enhanced the RBA production in HKLs. Similarly, NOS production was also significantly increased by some or all concentrations of P. guajava dichloromethane and ethyl acetate fractions. However, the NOS production was dose-dependently inhibited in HKLs treated with Pa ethyl acetate and both plants aqueous fractions at 10 or 10 and 40 μg/mL respectively. The lysozyme activity in cells treated with P. guajava crude extracts and all its organic solvent fractions were stronger than those in P. amarus treatments. Pure compounds including corosolic acid, guajaverin, ursolic acid, hypophyllanthin inhibited the HKLs viability according to concentration and type of compound. All pure compounds except avicularin significantly stimulated, at certain or all concentrations, the RBA production and/or the lysozyme activity in HKLs. The NOS production was significantly reduced in HKLs treated with oleanolic acid (30 μM) and hypophyllanthin (7.5 μM) while its level was increased by hypophyllanthin at 30 μM. These results highlighted that the crude ethanol extracts of P. guajava and P. amarus, their fractions and some of their pure components at certain concentrations can potentially act as immunomodulators, and could be considered as valuable candidates in fishery sciences.

Single or Combined Dietary Supply of Psidium guajava and Phyllanthus amarus Extracts Differentially Modulate Immune Responses and Liver Proteome in Striped Catfish (Pangasianodon hyphophthalmus)

Guava Psidium guajava L (Pg) and bhumi amla Phyllanthus amarus Schum. et Thonn (Pa) are well-known plants in traditional medicine. However, the capacity of these plants for improving the immune system of aquatic species has received less attention so far. This study aimed to investigate the effects of single supply or mixture of Pg and Pa extracts on immune responses, disease resistance and liver proteome profiles in striped catfish Pangasianodon hypophthalmus. Fish were fed diets including basal diet 0% or one of three doses of each plant extract, either alone or in mixture, 0.08, 0.2, or 0.5% Pg, Pa or mixture (Pg:Pa, v/v) for 6 weeks. The immune parameters (respiratory burst activity (RBA); nitric oxide synthase (NOS), total immunoglobulin, lysozyme, and complement activities) were examined at W3, W6 post-feeding, and after challenge test. The growth parameters and the challenge test with Edwardsiella ictaluri were done at W6. The liver proteome profiles were analyzed in W6 at 0.08 and 0.5% of each extract. The results showed that extract-based diets significantly improved growth parameters in the Pg0.2 group compared to control. The cellular immune responses in spleen and the humoral immune responses in plasma were significantly improved in a dose and time-dependent manner. Diets supplemented with single Pg and Pa extracts, and to lesser extent to combined extracts, could significantly decrease the mortality of striped catfish following bacterial infection compared to control. The proteomic results indicated that some pathways related to immune responses, antioxidant and lipid metabolism were enriched in liver at W6. Several proteins (i.e., CD8B, HSP90AA1, HSP90AB1, PDIA3, CASP8, TUBA1C, CCKAR, GNAS, GRIN2D, PLCG1, PRKCA, SLC25A5, VDAC2, ACTN4, GNAI2, LCK, CARD9, NLRP12, and NLRP3) were synergistically upregulated in mixture of Pg and Pa-based diets compared to control and single dietary treatments. Taken together, the results revealed that single Pg and Pa extracts at 0.2 and 0.5% and their mixture at 0.08 and 0.5% have the potential to modulate the immune mechanisms and disease resistance of striped catfish. Moreover, the combination of Pg and Pa in diets suggested positive synergistic effects liver proteome profile related to immune system processes.

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

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

Hematological and immune genes responses in yellow catfish (Pelteobagrus fulvidraco) with septicemia induced by Edwardsiella ictaluri

Yellow catfish (Pelteobagrus fulvidraco) has been an economically important freshwater species in China because of its good meat quality. In present, the high-density breeding industry has suffered great damage from bacterial infections, in especial, the rapid illness and death of fish caused by bacterial septicemia leads to huge economic losses. Therefore, it is urgent and important to identify pathogenic bacteria and study its pathogenicity. In this study, we isolated a bacterial strain from the yellow catfish with typical septicemia and named it E. 719, then, by morphological observations, regression infection, biochemical identification, 16S rDNA sequence analysis and triple PCR identification, E. 719 was determined to be Edwardsiella ictaluri. Further, we infected yellow catfish with E. ictaluri to study its effects on mortality rate, hematological, histopathological disturbances and expression of immune genes. The mortality results showed that E. ictaluri was highly pathogenic, all infected fish died after 14 days post injection, and the distribution of bacteria in body kidney, spleen, liver, head kidney and brain of fish was continuously detected by measuring the amount of bacteria in the tissues. In addition, the number of red blood cells decreased significantly with the time of infection, while the number of white blood cells and thrombocytes increased. In particular, the number of monocytes and neutrophils increased significantly in the differential leucocyte count (DLC). Histopathologic changes observed by HE staining showed similar results, gill, intestine, spleen and head kidney showed obvious inflammation, bleeding and necrosis. Besides, checking by real time quantitative RT-PCR assays, in both spleen and head kidney tissues which were the major immune organs, mRNA expressions of immune gene IL-1β, TNF-α, and MR significantly increased in the early and middle stages of infection, which suggested that the infection of E. ictaluri caused a strong immune response in yellow catfish. This study provides a preliminary basis for the diagnosis and treatment of pathophysiology septicemia in yellow catfish induced by E. ictaluri.

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

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