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

Terpinen-4-ol from tea tree oil prevents Aspergillus flavus growth in postharvest wheat grain

Plant volatile organic compounds (PVOCs) have gained increasing attention for their role in preventing fungal spoilage and insect contamination in postharvest agro-products owing to their effectiveness and sustainability. In this study, the essential oil was extracted from fresh M. alternifolia (tea tree) leaves, and the fumigation vapor of tea tree oil (TTO) completely inhibited the growth of Aspergillus flavus on agar plates at a concentration of 1.714 μL/mL. Terpinen-4-ol was identified as the major component (40.76 %) of TTO volatiles analyzed using headspace gas chromatography-mass spectrometry. Terpinen-4-ol vapor completely inhibited the A. flavus growth on agar plates and 20 % moisture wheat grain at 0.556 and 1.579 μL/mL, respectively, indicating that terpinen-4-ol serves as the main antifungal constituent in TTO volatiles. The minimum inhibitory concentration of terpinen-4-ol in liquid-contact culture was 1.6 μL/mL. Terpinen-4-ol treatment caused depressed, wrinkled, and punctured mycelial morphology and destroyed the plasma membrane integrity of A. flavus. Metabolomics analysis identified significant alterations in 93 metabolites, with 79 upregulated and 14 downregulated in A. flavus mycelia exposed to 1.6 μL/mL terpinen-4-ol for 6 h, involved in multiple cellular processes including cell membrane permeability and integrity, the ABC transport system, pentose phosphate pathway, and the tricarboxylic acid cycle. Biochemical analysis and 2,7-dichlorofluorescein diacetate staining showed that terpinen-4-ol induced oxidative stress and mitochondrial dysfunction in A. flavus mycelia. This study provides new insights into the antifungal effects of the main TTO volatile compounds terpinen-4-ol on the growth of A. flavus.

Selenium Nanoparticles: Revolutionizing Nutrient Enhancement in Aquaculture - A Review

Aquaculture, a cornerstone of global food production, confronts myriad challenges including disease outbreaks and environmental degradation. Achieving nutritionally balanced aquafeed is critical for sustainable production, prompting exploration into innovative solutions like selenium nanoparticles (SeNPs). SeNPs offer potent antimicrobial, antioxidant, and growth-promoting properties, bolstering gut immunity and digestive capacity in aquatic animals. Their high bioavailability and ability to traverse gut barriers make them promising candidates for aquafeed supplementation. This study investigates SeNPs as a cutting-edge solution to enhance nutrient supply in aquaculture, addressing key challenges while promoting environmental stewardship and food security. By synthesizing current research and highlighting future directions, this review provides valuable insights into sustainable aquaculture practices. SeNPs hold promise for revolutionizing aquaculture feed formulations, offering a pathway to improved production outcomes and environmental sustainability.

Immuno-protective response of Asian seabass (Lates calcarifer) to inactivated vaccines against Streptococcus iniae and Vibrio harveyi

BACKGROUND

In this study, the protective immunity and immunogenicity of the monovalent and bivalent Streptococcus iniae and Vibrio harveyi vaccine were evaluated in Asian seabass. To analyze immune responses, 1200 Asian seabass with an average weight of 132.6 ± 25.4 g were divided into eight treatments in triplicates (50 fish per tank) as follows: S. iniae immunized by injection (SI), V. harveyi immunized by injection (VI), bivalent S. iniae and V. harveyi (SVI) immunized by injection, S. iniae immunized by immersion (SIM), V. harveyi (VIM) immunized by immersion, bivalent S. iniae and V. harvei (SVIM) immunized by immersion, phosphate-buffered saline (PBS) by injection (PBSI) and control group without vaccine administration (CTRL). Blood and serum samples were taken at the end of the 30th and 60th days. Then the vaccinated groups were challenged with two bacteria (S. iniae) and (V. harveyi) separately and mortality was recorded for 14 days.

RESULTS

This study reveals that there is no significant difference in the hematological parameters on the 30th and 60th days of the experiment in the vaccine-immunized groups compared to the CTRL group (P > 0.05). Meanwhile, there was no significant difference in the amount of serum albumin level, respiratory burst activity, and serum bactericidal activity in the vaccine-immunized groups compared to the CTRL group on the 30th and 60th days of the experiment (P > 0.05). Total protein on the 60th day (in the VI and SVI groups), globulin on the 30th day (in the VI and SVI groups) and the 60th day (in the VI group) compared to the CTRL and PBSI groups had a significant increase (P < 0.05). Complement activity (in the VI and SVI groups) and lysozyme (in the SI and SVI groups) increased significantly compared to the control group (P < 0.05). Serum antibody titer against S. iniae had a significant increase in the SI, VI, SVI and SVIM groups compared to the CTRL and PBSI groups (P < 0.05). Serum antibody titer against V. harveyi had a significant increase in the groups immunized with the vaccine compared to the CTRL and PBSI groups (P < 0.05). A significant increase in the relative percentage survival (RPS) following challenge with S. iniae in the SVI (86.6%), SI (83.3%,) and VI (73.3%) groups were observed compared to the CTRL (43.3%) and PBSI (40%) groups (P < 0.05). Also, a significant increase in the RPS after challenge with V. harveyi in the SVI group, VI 86.6%, SVI 83.3%, VIM 80% and SVIM 76.6% were observed compared to the CTRL (46.6%) and PBSI (50%) groups (P < 0.05).

CONCLUSION

Overall, the results demonstrated that the bivalent vaccine of S. iniae and V. harveywas able to produce significant immunogenicity and RPS in Asian seabass.

Do combinations of fipronil, eugenol and carvacrol have synergistic effects against Rhipicephalus sanguineus?

The tick Rhipicephalus sanguineus is one of the main ectoparasites that affects dogs, causing direct and indirect damage to parasitized animals. Currently, infestation control is mainly carried out by using synthetic acaricidal drugs. However, a decrease in efficacy and an increase in resistance to the main therapeutic protocols against tick infestations have been increasingly reported and confirmed, a factor that has driven research into the potential acaricide activity of natural compounds, including in association with synthetic molecules. The aim of this work was to evaluate whether the combinations of fipronil (FIP) and eugenol (EUG), FIP and carvacrol (CAR), and EUG and CAR would have synergistic effects against immature and unfed adult stages of R. sanguineus through in vitro bioassays. Bioassays were carried out using the larval packet test (FAO 2004) adapted for nymphs and adults. The synergistic activity was explored by combining each solution, based on the estimated LC50, in a 1:1 ratio (FIP: EUG, FIP: CAR and EUG: CAR). CompuSyn software was used to evaluate the various pairwise combinations of FIP, EUG and CAR, checking if there was synergism or antagonism between them. FIP and EUG and FIP and CAR showed combination index (CIn) values above 1.45, indicating antagonism. The synergistic activity between EUG and CAR was verified against all unfed phases of R. sanguineus, since the CIn was below 0.70, a value that indicates synergism. The combination of fipronil with either eugenol or carvacrol presented antagonistic effects against R. sanguineus larvae. On the other hand, carvacrol and eugenol had excellent pharmacological synergism against all tick stages with mortality values in the range of 80 to 100%, including the adult stage, which is less susceptible than immature stages.

Optimization and antifungal efficacy against brown rot fungi of combined Salvia rosmarinus and Cedrus atlantica essential oils encapsulated in Gum Arabic

The stability, sensitivity, and volatility of essential oils are some of their most serious limitations, and nanoencapsulation has been considered one of the most effective techniques for solving these problems. This research aimed to investigate the incorporation of Salvia rosmarinus Speen and Cedrus atlantica Manetti (MEO) essential oil mixture in Gum Arabic (GA) and to evaluate nanoencapsulation's ability to promote antifungal activity against two brown rot fungi responsible for wood decay Gloeophyllum trabeum and Poria placenta. The optimization of encapsulation efficiency was performed using response surface methodology (RSM) with two parameters: solid-to-solid (MEO/GA ratio) and solid-to-liquid (MEO/ethanol). The recovered powder characterization was followed by various techniques using a scanning electron microscope (SEM), X-ray diffractometry (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), and thermo-gravimetric analysis (TGA). The optimal nanoencapsulating conditions obtained from RSM were ratios of MEO/GA of 1:10 (w/w) and MEO/ethanol of 10% (v/v), which provided the greatest encapsulation efficiency (87%). The results of SEM, XRD, DLS, FTIR, and TGA showed that the encapsulation of MEO using GA modified particle form and molecular structure and increased thermal stability. An antifungal activity assay indicated that an effective concentration of MEO had an inhibitory effect on brown rot fungi. It had 50% of the maximal effect (EC50) value of 5.15 ± 0.88 µg/mL and 12.63 ± 0.65 µg/mL for G. trabeum and P. placenta, respectively. Therefore, this product has a great potential as a natural wood preservative for sustainable construction and green building.

Effects of the combination of chitosan and Acinetobacter KU011TH on the growth and health performances and disease resistance of juvenile hybrid catfish (Clarias gariepinus × C. macrocephalus)

Aquatic animal health management has become a crucial component in the goal of increasing catfish aquaculture productivity. Additionally, hybrid catfish (Clarias gariepinus × C. macrocephalus) has been promoted as a highly profitable freshwater fish in Asia. Interestingly, the crucial diseases induced by Aeromonas hydrophila have been reported to greatly impede catfish production. To overcome this challenge, the aim was to investigate the effects of the oral administration of potentially synbiotic chitosan (CH) and Acinetobacter KU011TH (AK) on the growth performance, immunological responses, and disease resistance of hybrid catfish against A. hydrophila. The control group was fed a basal diet (A), the diet fed to treatment group B was supplemented with 20 mL of CH/kg diet (B), and the experimental feed fed to groups C-D was mixed with 1 × 108, 1 × 109 and 1 × 1010 CFU/mL AK coated with 20 mL of CH/kg diet. Five different groups of juvenile hybrid catfish were continuously fed the 5 formulated feeds for 4 weeks. The results revealed that all tested feeds did not significantly enhance the hybrid catfish's average daily gain, specific growth rate, feed conversion ratio, hematocrit and erythrocyte counts. Interestingly, the application of CH and AK significantly increased the leukocyte counts, respiratory burst, lysozyme activity, alternative complement pathway hemolytic activity, and bactericidal activity (P < 0.05). The expression levels of the immune-related genes in the whole blood, head kidney, and spleen were significantly increased after CH-AK application (P < 0.05), but this finding was not observed in the liver (P > 0.05). Additionally, after 14 days of A. hydrophila peritoneal injection, the fish in group C showed significantly higher survival rates of approximately 70.0 % compared with the control fish in groups B, D, and E (52.5 %, 40.0 %, 45.0 %, and 45.0 %, respectively) (P < 0.05). These results collectively suggest that short-term application of the diet fed to group C effectively boosted the immune responses and disease resistance of hybrid catfish against A. hydrophila.

Effect of Dietary Selenium on the Growth and Immune Systems of Fish

Dietary selenium (Se) is an essential component that supports fish growth and the immune system. This review attempts to provide insight into the biological impacts of dietary Se, including immunological responses, infection defense, and fish species growth, and it also identifies the routes via which it enters the aquatic environment. Dietary Se is important in fish feed due to its additive, antioxidant, and enzyme properties, which aid in various biological processes. However, excessive intake of it may harm aquatic ecosystems and potentially disrupt the food chain. This review explores the diverse natures of dietary Se, their impact on fish species, and the biological methods for eliminating excesses in aquatic environments. Soil has a potential role in the distribution of Se through erosion from agricultural, industrial, and mine sites. The research on dietary Se's effects on fish immune system and growth can provide knowledge regarding fish health, fish farming strategies, and the health of aquatic ecosystems, promoting the feed industry and sustainable aquaculture. This review provides data and references from various research studies on managing Se levels in aquatic ecosystems, promoting fish conservation, and utilizing Se in farmed fish diets.

Acute toxicity of essential oils of Aloysia triphylla (L'Hér.) Britton, Lippia gracilis Schauer, and Piper aduncum L. in Colossoma macropomum (Cuvier, 1818)

The aim of this study was to determine the acute toxicity of the essential oils (EOs) of Aloysia triphylla, Lippia gracilis and Piper aduncum in juvenile tambaqui (Colossoma macropomum), and evaluate the possible histopathological alterations in their gills. For the acute toxicity tests, juvenile tambaqui (n=24/treatment) were distributed in six treatments with three replicates, which comprised the control and five EO concentrations of A. triphylla (60, 80, 100, 120 and 140 mg L-1), L. gracilis (35, 40, 45, 50 and 55 mg L-1) and P. aduncum (42.5, 45, 47.5, 50 and 52.5 mg L-1), with an exposure period of 4 h. The mortality rate and severity of damage to the tambaqui gills were proportional to the increase in the concentration of the EO, with LC50-4 h values estimated at 109.57 mg L -1 for A. triphylla, 41.63 mg L -1 for L. gracilis and 48.17 mg L -1 for P. aduncum. The main morphological damages observed in the gills of the tambaqui exposed to the three EOs, were Grade I: hypertrophy and hyperplasia of lamellar epithelial cells, lamellar fusion, epithelial detachment, capillary dilation and constriction, proliferation of chloride cells and mucosal cells and edema; in low frequency Grade II damage as epithelial rupture and lamellar aneurysm. Necrosis (Grade III damage) was observed only in gill lamellae exposed to P. aduncum EO (47.5, 50.0 and 52.5 mg L-1). Concentrations of EOs below LC50-4 h can be used sparingly, for short periods of exposure for the treatment of diseases in tambaqui breeding.

Simultaneous Hydrodistillation of Cedrus atlantica Manetti and Salvia rosmarinus Spenn: Optimization of Anti-Wood-Decay Fungal Activity Using Mixture Design Methodology

Chemical fungicides are often harmful to people and the environment because of their toxicity. The wood protection industry places a high priority on replacing them with natural products. Therefore, this investigation focused on developing a formulation of a binary combination of Salvia rosmarinus Spenn and Cedrus atlantica Manetti obtained by Simultaneous hydrodistillation to protect the wood from decay using a mixture design methodology. The chemical composition of essential oil was identified by gas chromatography coupled with mass spectrometry (GC/MS), and their anti-wood-decay fungal activity was assessed using the macrodilution method against four fungi responsible for wood decay: Coniophora puteana, Coriolus versicolor, Gloeophyllum trabeum, and Poria placenta. The results of GC/MS identified myrtenal as a new component appearing in all binary combinations. The optimum anti-wood-decay fungal activity was observed in a combination of 60% S. rosmarinus and 40% C. atlantica essential oils, providing an effective concentration for 50% of maximal effect (EC50) value of 9.91 ± 1.91 and 9.28 ± 1.55 μg/mL for C. puteana and C. versicolor, respectively. The highest anti-wood-decay fungal activity for G. trabeum and P. placenta was found in the combination of 55% of S. rosmarinus and 45% of C. atlantica essential oils, with EC50 values of 11.48 ± 3.73 and 22.619 ± 3.79 μg/mL, respectively. Combined simultaneous hydrodistillation improved the antifungal effect of these essential oils. These results could be used to improve antifungal activity and protect wood against wood-decay fungi.

Eugenol Essential Oil and Nanoemulsion as Antihydatic Agents with Antifibrotic and Immunomodulatory Effects in Cystic Echinococcosis

Conventional scolicidal agents are still unsatisfactory in combating hydatid disease due to their low efficacy and increased drug side effects. Therefore, novel scolicides are required. This study aimed to evaluate the antihydatic and immunomodulatory effects of eugenol essential oil (Eug) and its nanoemulsion (Eug-NE) in cystic echinococcosis (CE). Eug and Eug-NE were administered orally to CE-infected rats and compared to albendazole (ABZ). Hydatid cyst development was assessed based on organ weight and hypertrophy indicators of the infected organs, along with a histopathological and histochemical evaluation of collagen content. The immunomodulatory effects of treatment on CE were evaluated by serum cytokine levels measurement of interferon-γ (IFN-γ) and interleukin (IL)-4 and immunohistochemical (IHC) analysis of signal transducer and activator of transcription 4 (STAT4) and GATA-binding protein 3 (GATA3) markers. Eug-NE was the most effective in reducing the cyst weights, organ weights, and hypertrophy indicators and improving histopathological lesions with reduced collagen content. Eug and Eug-NE significantly increased the IFN-γ levels and decreased the IL-4 levels, while IHC analysis demonstrated a significant reduction in STAT4 and GATA3 expression in all treated groups. Eug and Eug-NE demonstrated antihydatic and preventative effects, with a substantial decrease in liver fibrosis compared to that of ABZ. Besides their promising immunomodulatory effects, their good treatment response suggests their use as alternatives or complementary scolicidal agents in hydatid cyst treatment.

Chemical Composition and Biological Activities of Essential Oils from Origanum vulgare Genotypes Belonging to the Carvacrol and Thymol Chemotypes

The remarkable biological activities of oregano essential oils (EOs) have recently prompted a host of studies aimed at exploring their potential innovative applications in the food and pharmaceutical industries. The chemical composition and biological activities of EOs from two Origanum vulgare genotypes, widely cultivated in Sicily and not previously studied for their biological properties, were characterized. Plants of the two genotypes, belonging to the carvacrol (CAR) and thymol (THY) chemotypes and grown in different cultivation environments, were considered for this study. The chemical profiles, including the determination of enantiomeric distribution, of the EOs, obtained by hydrodistillation from dried leaves and flowers, were investigated by GC-MS. Biological activity was evaluated as antimicrobial properties against different pathogen indicator strains, while intestinal barrier integrity, reduction in pathogen adhesion and anti-inflammatory actions were assayed in the intestinal Caco-2 cell line. The chemical profile of the CAR genotype was less complex and characterized by higher levels of the most active compound, i.e., carvacrol, when compared to the THY genotype. The enantiomeric distribution of chiral constituents did not vary across genotypes, while being markedly different from that observed in Origanum vulgare genotypes from other geographical origins. In general, all EOs showed high antimicrobial activity, both in vitro and in a food matrix challenge test. Representative EOs from the two genotypes resulted not altering epithelial monolayer sealing only for concentrations lower than 0.02%, were able to reduce the adhesion of selected pathogens, but did not exert relevant anti-inflammatory effects. These results suggest their potential use as control agents against a wide spectrum of foodborne pathogens.

Assessment of the Oxidative Damage and Genotoxicity of Titanium Dioxide Nanoparticles and Exploring the Protective Role of Holy Basil Oil Nanoemulsions in Rats

This study was designed to evaluate the oxidative damage, genotoxicity, and DNA damage in the liver of rats treated with titanium nanoparticles (TiO₂-NPs) with an average size of 28.0 nm and ξ-potential of - 33.97 mV, and to estimate the protective role of holy basil essential oil nanoemulsion (HBEON). Six groups of Male Sprague-Dawley rats were treated orally for 3 weeks as follows: the control group, HBEO or HBEON-treated groups (5 mg/kg b.w), TiO₂-NPs-treated group (50 mg/kg b.w), and the groups treated with TiO₂-NPs plus HBEO or HBEON. Samples of blood and tissues were collected for different analyses. The results revealed that 55 compounds were identified in HBEO, and linalool and methyl chavicol were the major compounds (53.9%, 12.63%, respectively). HBEON were semi-round with the average size and ζ-potential of 120 ± 4.5 nm and - 28 ± 1.3 mV, respectively. TiO₂-NP administration increased the serum biochemical indices, oxidative stress markers, serum cytokines, DNA fragmentation, and DNA breakages; decreased the antioxidant enzymes; and induced histological alterations in the liver. Co-administration of TiO₂-NPs plus HBEO or HBEON improved all the tested parameters and the liver histology, and HBEON was more effective than HBEO. Therefore, HEBON is a promising candidate able to protect against oxidative damage, disturbances in biochemical markers, gene expression, DNA damage, and histological changes resulting from exposure to TiO₂-NPs and may be applicable in the food and pharmaceutical sectors.

Protective effects of the fructooligosaccharide on the growth performance, biochemical indexes, and intestinal morphology of blunt snout bream (Megalobrama amblycephala) infected by Aeromonas hydrophila

The purpose of the study was to investigate the effects of dietary fructooligosaccharide (FOS) on growth performance, biochemical indexes, intestinal morphology, and growth-related gene expression of blunt snout bream (Megalobrama amblycephala) infected by Aeromonas hydrophila (AH). Two hundred twenty-five healthy blunt snout bream with an initial body weight of 38.41 ± 0.88 g were randomly divided into five groups with three replicates: control (basal diet), model (AH + basal diet), SFOS (AH + 2 g/kg FOS), MFOS (AH + 4 g/kg FOS), LFOS (AH + 6 g/kg FOS). After 9 weeks of feeding, the results showed that the FOS-added diet abrogated AH-induced retardation, hemorrhage, and inflammatory infiltration. FOS supplementation enhanced the growth performance degradation caused by AH, and the highest growth performance was observed at MFOS. Meanwhile, the addition of FOS to feed improved the blood immunity reduced by AH. In expansion, the mucosal epithelium of intestinal villi exfoliated, exposing the lamina propria, and a few villi were genuinely harmed in the model group. Fish fed with MFOS ameliorated the damaged intestine, evidenced by well-preserved intestine architecture. Furthermore, the model group downregulated the expression of growth-related genes (growth hormone receptor (GHR), insulin-like growth factor 1 (IGF-1)). Fish fed with 2 g/kg or 4 g/kg FOS upregulated the genes specified above expressions in the liver compared with the model group. In conclusion, the results mentioned above suggested that the dietary FOS could relieve the pressure to elevate the immune damage and intestine injury induced by AH and enhance the hepatic expression of IGF-1 and GHR.

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.

Green nanotechnology for controlling bacterial load and heavy metal accumulation in Nile tilapia fish using biological selenium nanoparticles biosynthesized by Bacillus subtilis AS12

Heavy metal accumulation and pathogenic bacteria cause adverse effects on aquaculture. The active surface of selenium (Se) nanoparticles can mitigate these effects. The present study used Se-resistant Bacillus subtilis AS12 to fabricate biological Se nanoparticles (Bio-SeNPs). The double-edged Bio-SeNPs were tested for their ability to reduce the harmful effects of heavy metals and bacterial load in Nile tilapia (Oreochromis niloticus) and their respective influences on fish growth, behavior, and health. The Bio-SeNPs have a spherical shape with an average size of 77 nm and high flavonoids and phenolic content (0.7 and 1.9 g g^-1 quercetin and gallic acid equivalents, respectively), resulting in considerable antioxidant and antibacterial activity. The Bio-SeNPs (3-5 μg ml^-1) in the current study resolved two serious issues facing the aquaculture industry, firstly, the population of pathogenic bacteria, especially Aeromonas hydrophilia, which was reduced by 28-45% in fish organs. Secondly, heavy metals (Cd and Hg) at two levels (1 and 2 μg ml^-1) were reduced by 50-87% and 57-73% in response to Bio-SeNPs (3-5 μg ml^-1). Thus, liver function parameters were reduced, and inner immunity was enhanced. The application of Bio-SeNPs (3-5 μg ml^-1) improved fish gut health, growth, and behavior, resulting in fish higher weight gain by 36-52% and a 40% specific growth rate, compared to controls. Furthermore, feeding and arousal times increased by 20-22% and 28-53%, respectively, while aggression time decreased by 78% compared to the control by the same treatment. In conclusion, Bio-SeNPs can mitigate the accumulation of heavy metals and reduce the bacterial load in a concentration-dependent manner, either in the fish media or fish organs.

Selected essential oil components fail to induce an immunological response in Artemia but still protect against vibriosis

In the present research, in order to screen out the best candidates from 12 different EOCs, we proposed three in vivo screening methods, namely the screening method of bioluminescence of V. campbellii associated with brine shrimp, regrowth performance of V. campbellii, and immune gene expression of brine shrimp without challenge. Our result showed that challenged with V. campbellii at 10⁷ cells/mL, the survival of the brine shrimp at 48 h was significantly increased after treatment with the EOCs (at 0.0005%, v/v) of 4-allylanisole, R-(+)-limonene, S-(-)-limonene, (-)-terpinen-4-ol, (±)-citronellal, citral, trans-cinnamaldehyde and (+)-carvone, compared to the positive control group. Also, it was observed that the EOCs- of 4-allylanisloe, R-(+)-limonene, S-(-)-limonene, (-)-β-pinene, geraniol, (±)-citronellal, citral, trans-cinnamaldehyde and (+)-carvone decreased significantly the in vivo bioluminescence of V. campbellii at 36 h after Vibrio exposure. The regrowth assay showed that independently from incubation time (1, 12 or 24 h), no difference was observed in the regrowth curve in all EOC treatment groups compared to the positive control group. The dscam gene expression in the (±)-citronellal group, and the sod gene in the citral group were observed to be significantly higher than in the negative control at 24 h, respectively. However, most of the immune genes were down-regulated in the EOC groups. Combining the survival data at 48 h with the bioluminescence result at 36 h, it was noted that the survival rate of brine shrimp was moderately correlated with in vivo bioluminescence of V. campbellii. The results indicate that the approach of determining in vivo bioluminescence of V. campbellii is a moderately reliable, fastest, and cheapest screening method for EOCs. As the regrowth performance assay of V. campbellii, and the immune genes expression assay of brine shrimp without challenge cannot predict Artemia survival properly, they cannot be used as screening methods for EOCs. Moreover, the immune genes expression assay is relatively slow, time-consuming and costly.

Gill Oxidative Stress Protection through the Use of Phytogenics and Galactomannan Oligosaccharides as Functional Additives in Practical Diets for European Sea Bass (Dicentrarchus labrax) Juveniles

The aim of the present study is to evaluate the potential of two functional additives as gill endogenous antioxidant capacity boosters in European sea-bass juveniles fed low-FM/FO diets when challenged against physical and biological stressors. For that purpose, two isoenergetic and isonitrogenous diets with low FM (10%) and FO (6%) contents were supplemented with 5000 ppm plant-derived galactomannan-oligosaccharides (GMOS) or 200 ppm of a mixture of garlic and labiate plant essential oils (PHYTO). A control diet was void from supplementation. Fish were fed the experimental diet for nine weeks and subjected to a confinement stress challenge (C challenge) or a confinement stress challenge combined with an exposure to the pathogen Vibrio anguillarum (CI challenge). Both GMOS and PHYTO diets attenuated fish stress response, inducing lower circulating plasma cortisol and down-regulating nfκβ2 and gr relative gene-expression levels in the gill. This attenuated stress response was associated with a minor energetic metabolism response in relation to the down-regulation of nd5 and coxi gene expression.

Screening and evaluating honokiol from Magnolia officinalis against Nocardia seriolae infection in largemouth bass (Micropterus Salmoides)

Nocardiosis caused by Nocardia seriolae is a major threat to the aquaculture industry. Given that prolonged therapy administration can lead to a growth of antibiotic resistant strains, new antibacterial agents and alternative strategies are urgently needed. In this study, 80 medicinal plants were selected for antibacterial screening to obtain potent bioactive compounds against N. seriolae infection. The methanolic extracts of Magnolia officinalis exhibited the strongest antibacterial activity against N. seriolae with the minimal inhibitory concentration (MIC) of 12.5 μg/ml. Honokiol and magnolol as the main bioactive components of M. officinalis showed higher activity with the MIC value of 3.12 and 6.25 μg/ml, respectively. Sequentially, the evaluation of antibacterial activity of honokiol in vivo showed that honokiol had good biosafety, and could significantly reduce the bacterial load of nocardia-infected largemouth bass (p < .001). Furthermore, the survival rate of nocardia-infected fish fed with 100 mg/kg honokiol was obviously improved (p < .05). Collectively, these results suggest that medicinal plants represent a promising reservoir for discovering active components against Nocardia, and honokiol has great potential to be developed as therapeutic agents to control nocardiosis in aquaculture.

Palmatine Inhibits the Pathogenicity of Aeromonas hydrophila by Reducing Aerolysin Expression

Aeromonas hydrophila, an opportunistic aquatic pathogen widely spread in aquatic environments, is responsible for a number of infectious diseases in freshwater aquaculture. In addition, A. hydrophila can transmit from diseased fish to humans and results in health problems. The occurrence of antibiotic-resistant bacterial strains restricts the application of antibiotics and is responsible for failure of the treatment. Moreover, residues of antibiotics in aquatic products often threaten the quality and safety. Therefore, alternative strategies are called to deal with infections caused by antibiotic-resistant bacteria. Aerolysin, one of the most important virulence factors of A. hydrophila, is adopted as a unique anti-virulence target on the basis of the anti-virulence strategy to battling infections caused by A. hydrophila. Palmatine, an isoquinoline alkaloid from a variety of herbal medicines that showed no anti-A. hydrophila activity, could reduce hemolysis of the bacterium by decreasing aerolysin production. The results of the qPCR assay demonstrated that the transcription of the aerA gene was suppressed. Moreover, cell viability and in vivo study showed that palmatine treatment could decrease the pathogenicity of A. hydrophila both in vitro and in vivo. In summary, palmatine is a leading compound against A. hydrophila-associated infection in aquaculture by inhibiting the expression of aerolysin.

Phytochemical Profiling, Antioxidant, Antimicrobial and Cholinesterase Inhibitory Effects of Essential Oils Isolated from the Leaves of Artemisia scoparia and Artemisia absinthium

The current studies were focused on the phytochemical profiling of two local wild Artemisia species, Artemisia scoparia and Artemisia absinthium leaves’ essential oils, extracted via the hydro distillation method along with evaluation of their antioxidant as well as antimicrobial effects. The constituents of EOs were identified using a combined gas chromatography-mass spectrometric (GC-MS) technique. A total of 25 compounds in A. scoparia essential oil (EOAS) were identified, and 14 compounds with percentage abundance of >1% were tabulated, the major being tocopherol derivatives (47.55%). A total of nine compounds in Artemisia absinthium essential oil (EOAA) were enlisted (% age > 1%), the majority being oleic acid derivatives (41.45%). Strong antioxidant effects were pronounced by the EOAS in DPPH (IC50 = 285 ± 0.82 µg/mL) and in ABTS (IC50 = 295 ± 0.32 µg/mL) free radical scavenging assays. Both the EOs remained potent in inhibiting the growth of bacterial species; Escherichia coli (55−70%) and Shigella flexneri (60−75%) however remained moderately effective against Bacillus subtilis as well as Staphylococcus aureus. Both EOAS and EOAA strongly inhibited the growth of the tested fungal species, especially Aspergillus species (up to 70%). The oils showed anti-cholinesterase potential by inhibiting both Acetylcholinesterase (AChE; IC50 = 30 ± 0.04 µg/mL (EOAS), 32 ± 0.05 µg/mL (EOAA) and Butyrylcholinesterase (BChE; IC50 = 34 ± 0.07 µg/mL (EOAS), 36 ± 0.03 µg/mL (EOAA). In conclusion, the essential oils of A. scoparia and A. absinthium are promising antioxidant, antimicrobial and anticholinergic agents with a different phytochemical composition herein reported for the first time.

Effects of Illicium verum Hook. f. (Chinese herb) enriched diet on growth performance, immune response and disease resistance in Catla catla [Hamilton] fingerlings against Aeromonashydrophila

Our present study investigates the effects of Illicium verum enriched diet on growth performance, immune response and disease resistance in Catla catla fingerlings against Aeromonas hydrophila. Experimental groups, i.e., infected C. catla were fed with 5 g/kg, 10 g/kg and 15 g/kg of I. verum diet for a period of 30 days showed a significant increase in their final body weight (FBW) over control. There was a significant increase (p < 0.05) in total weight gain (TWG), specific growth rate (SGR), feed conversion rate (FCR), protein efficiency ratio (PER), condition factor (CF) and survival rate (SR) in 10 g/kg and 15 g/kg groups compared to control; also from 31 to 60 days these groups showed an enhanced (p < 0.05) complement activity, phagocytic activity, respiratory burst activity and lysosome activity. The experimental group fed with 10 g/kg of I. verum diet showed the least cumulative mortality rate (5%) compared to 5 g/kg (30%) and 15 g/kg (15%) experimental groups and in control (10%) and negative control (75%). Our present study highlights that challenged fish fed with the mid dosage of 10 g/kg showed a significant increase in overall growth performance, non susceptibility to diseases and tolerance against A. hydrophila in C. catla compared to other experimental groups including the group given with high dosage of 15 g/kg. Thus our results suggest 10 g/kg as the optimal dosage of I. verum that can be used to enrich the fish diet for a better performance and effective immunostimulation in commercially important C. catla for its sustainable culture and is reported for the first time.

Effects of caffeic acid on the growth performance, growth genes, digestive enzyme activity, and serum immune parameters of beluga (Huso huso)

Caffeic acid is a phenolic metabolite known for its beneficial pharmaceutical effects and is suggested as a functional additive for aquaculture. In this study, the effects of caffeic acid on the growth performance, growth genes, digestive enzyme activity, and serum immune parameters of beluga (Huso huso) were investigated. For this purpose, 120 beluga juveniles (367.75 ± 21.32 g) were divided into 12 tanks and fed with caffeic acid at rates of 0 (T0, control), 1 (T1), 5 (T2), and 10 (T3) g/kg for 56 days. The final weight and weight gain of beluga were significantly higher in fish fed 5 (T2) and 10 (T3) g caffeic acid/kg than in the control group and 1 (T1) g caffeic acid/kg. The specific growth rate was significantly higher in beluga fed 10 g caffeic acid/kg than 0 and 1 g/kg. Compared with the control group, the amylase, lipase, and pepsin activities were significantly higher in T2 and T3. The relative expression of growth hormone and insulin-like growth factor significantly increased in T3 compared with the control group. The expression of lipoprotein lipase and nuclear factor interleukin 3 of beluga fed 5 and 10 g caffeic acid/kg was higher than the control group. The lysozyme activity, total immunoglobulin, and total protein in the serum of beluga significantly increased in fish fed with caffeic acid at different rates compared with the control group. Based on the finding, the results suggested that the inclusion of caffeic acid (5-10 g/kg) in the diets of beluga is recommended to enhance the growth performance, some digestive enzyme activity, and serum immune parameters.

Anthelmintic Efficacy of Palmarosa Oil and Curcuma Oil against the Fish Ectoparasite Gyrodactylus kobayashii (monogenean)

Monogeneans are a serious threat to the development of aquaculture due to the severe economic losses they cause. The prevention and treatment of this disease are increasingly difficult because of the environmental and health concerns caused by the use of chemical anthelmintics and the emergence of drug resistance. It is thus necessary to search for effective alternatives for the treatment of monogenean infections. In the current study, anthelmintic efficacy of 16 selected essential oils (EOs) was investigated using the goldfish (Carassius auratus)–Gyrodactylus kobayashii model. The screening experiment indicated that palmarosa oil and curcuma oil had satisfactory anthelmintic activity against G. kobayashii with EC100 values of 10 and 12 mg/L after 24-h exposure, respectively. The in vivo and in vitro assays indicated anthelmintic efficacy of palmarosa oil against G. kobayashii was in a time and dose-dependent manner. Interestingly, curcuma oil showed an anesthetic effect on G. kobayashii, and its anthelmintic activity was dose-dependent rather than time-dependent in the concentration range tested in this study. Additionally, the 24-h LC50 (50% lethal concentration) against goldfish of these two EOs was 8.19-fold and 5.54-fold higher than their corresponding EC50 (50% effective concentration) against G. kobayashii, respectively. Moreover, exposure to these two EOs at 100% effective concentration against G. kobayashii had no serious physiological and histopathological influence on goldfish. These results demonstrated a high safety for goldfish of these two EOs. Overall, palmarosa oil and curcuma oil could be potential candidates for the treatment of G. kobayashii infections in aquaculture.

The Use of Cinnamon Essential Oils in Aquaculture: Antibacterial, Anesthetic, Growth-Promoting, and Antioxidant Effects

Cinnamon essential oils (EOs) are widely known for their pharmaceutical properties; however, studies investigating the use of these EOs in aquaculture are scarce. The aims of this study were to evaluate the anesthetic effect of bathing silver catfish (Rhamdia quelen) with Cinnamomum cassia EO (CCEO) and its nanoemulsion (NCCEO); the growth-promoting and antioxidant effects of dietary supplementation with CCEO in silver catfish; and the in vitro antibacterial effect of CCEO, NCCEO, and Cinnamomum zeylanicum EO (CZEO) against bacteria isolated from diseased silver catfish. The two cinnamon EOs showed promising antibacterial activity, which was potentiated by the nanoemulsion. CCEO showed satisfactory anesthetic activity in silver catfish, and its nanoemulsion intensified the sedative activity. Supplementation of 1.0 mL CCEO per kg of diet for 60 days increased weight, length, and weight gain when compared to the control group, evidencing the growth-promoting activity of this EO. Dietary supplementation of CCEO for 30 and 60 days also showed an antioxidant effect, as it decreased levels of thiobarbituric acid reactive species and increased the superoxide dismutase activity in the liver of silver catfish. Therefore, cinnamon EOs have a promising use in aquaculture.

The pharmaco-therapy potential of astaxanthin: human and animal targeting roles

The recent pandemic stress and the impacts of climatic changes on humans’ and animals’ health status and well-being resulted in severe drawbacks. Initially, stress-induced oxidation resulting from the generation of free radicals leading to the impairment of cellular function and a high possibility of attack with infection. Astaxanthin is a bioactive material derived from fish, crustaceans, and algae with high antioxidative potential. Astaxanthin is a lipid-soluble carotenoid that can easily cross through the cellular membrane layers to catch the reactive oxygen metabolites. Astaxanthin also has pigmentation properties making it suitable for pharmaceutical, cosmetic, nutraceutical, agriculture, and aquaculture sectors. Recently, astaxanthin is suggested as a natural scavenger for free radicals induced by COVID-19. Besides, using astaxanthin as antioxidative and immunostimulant agents is well-reported in several clinical studies. The output of these investigations should be simplified and presented to the scientific community to utilize the available information and fill the gap of knowledge. Also, it is necessary to update the researchers with the recent recommendations of applying astaxanthin in vivo and in vitro to help in proposing new horizons for engaging natural antioxidative agents to protect human and animal health. Herein, this review article tackled the nature, sources, potential roles, applicable sides, and availability of astaxanthin to fortify the scientific community with the required knowledge for further research efforts.

The effects of coriander (Coriandrum sativum) seeds on the growth performance, growth hormone, antibacterial capacity, and immune response of European sea bass (Dicentrarchus labrax)

Coriander seeds are among the functional herbal supplements, but their effects on aquatic animals are still lacking. Herein we evaluated the effects of coriander seeds on the growth performance, growth hormone, antibacterial capacity, and immune response of European sea bass (Dicentrarchus labrax). Fish with initial mean weights of 5.08 ± 0.12 g/fish were allocated in four groups (in triplicate) and fed dietary coriander at 0, 5, 10, and 20 g/kg for 150 days. The growth performance, feed utilization, and survival rate of fish-fed dietary coriander meaningfully increased (P<0.05). The protein efficiency ratio gradually increased (P<0.05) in fish-fed coriander seeds compared with the control. On the other hand, the feed conversion ratio was gradually decreased (P<0.05) in fish-fed coriander seeds comparing with the control. The survival rate was markedly increased (P<0.05) in European sea bass-fed dietary coriander regardless of the inclusion level. Further, no differences were seen among fish fed varying levels of coriander (P<0.05). The level of blood growth hormone was markedly higher (P<0.05) in European sea bass-fed dietary coriander at 20 g/kg than fish-fed 0 and 5 g/kg. The abundance of intestinal Vibrio spp. and Faecal Coliform were obviously lower (P<0.05) in fish fed 10 and 20 g/kg than fish fed the coriander-free diet. Further, fish fed 20 g/kg had lower (P<0.05) Vibrio spp. and Faecal Coliform counts than fish fed 10 g/kg. Fish fed dietary coriander had significantly higher (P<0.05) hematocrit, hemoglobulin, red blood cells (RBCs), and white blood cells (WBCs) than fish fed the control. The lysozyme and phagocytic activities were meaningfully increased (P<0.05) in fish fed 10 and 20 g/kg compared with fish fed 0 and 5 g/kg of dietary coriander. In conclusion, dietary coriander could be included in the diets at 10–20 g/kg to improve the growth performance, growth hormone, feed utilization, and immune response of European sea bass.

Research on the indirect antiviral function of medicinal plant ingredient quercetin against grouper iridovirus infection

Grouper iridovirus is a devastating pathogen that belongs to the genus Ranavirus. Based on the previous results that natural ingredient quercetin isolated from Illicium verum Hook. f. could effectively inhibit Singapore grouper iridovirus (SGIV) replication, suggesting that quercetin could serve as potential antiviral agent against grouper iridovirus. To know about whether quercetin has indirect antiviral activity against SGIV, this study made the investigation in vitro and in vivo, and the potential mechanism was also explored. Pretreating the cells with quercetin (12.5 μg/mL) significantly inhibited the replication of SGIV, similar results were also confirmed in vivo. Importantly, quercetin pretreatment could induce the expression of genes involved in type I interferon (IFN) system (IFN, STAT1, PKR, MxI and ISG15) and TLR9. It suggested that quercetin exerted the indirect antiviral activity against SGIV infection through promoting the recognition of SGIV and activating the IFN pathway to establish the antiviral status of host cell. Taken together, our results shedded light on the indirect antiviral function of natural ingredient quercetin, and clearly demonstrated that natural ingredient quercetin will be an excellent potential agent against SGIV infection in grouper aquaculture.

Predicting the impact of environmental factors on citrus canker through multiple regression

Climatic conditions play a significant role in the development of citrus canker caused by Xanthomonas citri pv. citri (Xcc). Citrus canker is regarded as one of the major threats being faced by citrus industry in citrus growing countries of the world. Climatic factors exert significant impacts on growth stage, host susceptibility, succulence, vigor, survival, multiplication rate, pathogen dispersion, spore penetration rate, and spore germination. Predicting the impacts of climatic factors on these traits could aid in the development of effective management strategies against the disease. This study predicted the impacts of environmental variables, i.e., temperature, relative humidity, rainfall, and wind speed the development of citrus canker through multiple regression. These environmental variables were correlated with the development of canker on thirty (30) citrus varieties during 2017 to 2020. Significant positive correlations were noted among environment variables and disease development modeled through multiple regression model (Y = +24.02 + 0.5585 X1 + 0.2997 X2 + 0.3534 X3 + 3.590 X4 + 1.639 X5). Goodness of fit of the model was signified by coefficient determination value (97.5%). Results revealed the optimum values of environmental variables, i.e., maximum temperature (37°C), minimum temperature (27°C), relative humidity (55%), rainfall (4.7-7.1 mm) and wind speed (8 Km/h), which were conducive for the development of citrus canker. Current study would help researchers in designing better management strategies against citrus canker disease under changing climatic conditions in the future.

Assessment of Verbesina alternifolia and Mentha piperita oil extracts on Clinostomum phalacrocoracis metacercariae from Tilapia zillii

Background

Clinostomiasis (yellow grub disease) is a disease of freshwater fish caused by the encysted metacercariae (EMC) of Clinostomum spp. showing retarded growth, unusual host behavior, and even death in fishes. Thus, the purpose of this study was to conduct an assessment of two selected plant extract: V. alternifolia and M. piperita oil extracts on tegument surface of C. phalacrocoracis metacercariae (MC) from T.zillii as utilisation of biodegradable, eco-friendly plant extracts in environmental remediation to avoid utilization of chemotherapy to control of parasitic diseases leading to potential long-term health risks on the environment and humans.

Results

The results of evaluation efficacy of plant oil extracts, namely V. alternifolia and M. piperita on C. phalacrocoracis MC infecting T. zillii, were dependent on dose and exposure time. The lethal concentrations caused by V. alternifolia extract were determined LC50 at (400 ppm/24 h), and contrarily, the worms from gp2 exposed to M. piperita extract at LC50 (1000 ppm/48 h) and did not cause complete mortality among the exposed worms. Statistically, mortality of C. phalacrocoracis caused by V. alternifolia was found to be a stronger effect significantly higher than that caused by M. piperita. The fine integument structures observed suffered stronger effect that appeared as severe damage and desquamation of worm’s teguments after exposure of V. alternifolia. In contrast, the M. piperita treatment exhibited edematous, swollen teguments, and blebs. Therefore, C. phalacrocoracis was an adequate model for evaluation of in vitro anthelmintic effects, contributing to the endeavors to identify suitable plant extracts, V. alternifolia and M. piperita.

Conclusions

This study highlights on assessment of selected two plant extracts; V. alternifolia and M. piperita revealed a stronger effect of V. alternifolia than M. piperita on tegumental surface of C. phalacrocoracis worms and, also, recommended the successful utilization of V. alternifolia on investigated worms as anthelmintic efficacy.

Exploring the Roles of Dietary Herbal Essential Oils in Aquaculture: A Review

The aquaculture sector is one of the main activities contributing to food security for humanity around the globe. However, aquatic animals are susceptible to several farming stressors involved in deteriorated growth performance, reduced productivity, and eventually high mortality rates. In some countries still, antibiotics and chemotherapies are comprehensively applied to control biotic stressors. Aside from the apparent benefits, the continuous usage of antibiotics develops bacterial resistance, deteriorates bacterial populations, and accumulates these compounds in the aquatic environment. Alternatively, environmentally friendly additives were used to avoid the direct and indirect impacts on the aquatic ecosystem and human health. In aquaculture, medicinal herbs and extracts are extensively used and approved for their growth-promoting, anti-inflammatory, and antioxidative properties. Herbal essential oils contain many bioactive components with powerful antibacterial, antioxidative, and immunostimulant potentials, suggesting their application for aquatic animals. Essential oils can be provided via diet and can benefit aquatic animals by improving their well-being and health status. The use of essential oils in aquafeed has been studied in a variety of aquatic animals to determine their beneficial roles and optimum doses. The outputs illustrated that herbal essential oils are exciting alternatives to antibiotics with prominent growth promotion, antioxidative, and immunostimulant roles. Herein, we reviewed the beneficial roles of essential oils in aquaculture. This review also aims to describe trends in herbal essential oils use, mainly in commercial fish species, and to analyze different factors that affect essential oils’ efficacy on the growth performance, antioxidative, and immune responses of finfish species.

Effects of dietary Gracilaria persica on the intestinal microflora, thyroid hormones, and resistance against Aeromonas hydrophila in Persian sturgeon (Acipenser persicus)

Red seaweeds have several biomedical derivatives making them healthy additives for the aquaculture industry. Previously we reported enhanced growth performance, feed utilization, and immunity of Persian sturgeon treated with Gracilaria gracilis. Herein, we investigated the effects of G. gracilis on the intestinal microflora, thyroid hormones, and resistance against Aeromonas hydrophila in Persian sturgeon. Fish fed G. gracilis at 0, 2.5, 5, and 10 g/kg for eight weeks, then challenged with A. hydrophila for ten days. The results showed that the total bacterial count in the fish intestines had no meaningful differences among the groups of fish fed varying levels of G. persica (P˃0.05). Fish fed 10 g/kg of G. persica had a higher lactic acid bacteria (LAB) count than fish fed 0, 2.5, and 5 g/kg (P<0.05). Serum thyroid-stimulating hormone (TSH) showed higher levels in fish treated with 2.5 and 5 g/kg of G. persica than the other groups (P<0.05). Besides, fish fed 2.5 g/kg G. persica had higher thyroxine (T4) and triiodothyronine (T3) levels than the other groups (P<0.05). At the end of the challenge test, the highest mortality was seen in the fish fed the G. persica free diet. In summary, Persian sturgeon treated G. gracilis had improved intestinal microflora, thyroid hormones, and resistance against A. hydrophila.

Studying the Influence of Copper on the Growth Behavior, Antioxidative Status, and Histology of the Intestine and Liver of Striped Catfish (Pangasianodon hypophthalmus)

Microelements are well recognized as an essential approach in the field of aquaculture nutrition. Thus, this study aimed to evaluate copper (Cu) inclusion (0, 0.5, 1, and 2 mg/kg) on Striped catfish performances. Fish fed the Cu-incorporated diets for 60 days, then their growth behavior, antioxidative capacity, and intestinal and liver histological features were evaluated. The results showed a marked enhancement in Striped catfish's growth behavior fed 1-2 mg/kg of Cu, as shown by the final weight, weight gain, and specific growth rate. The feed and protein efficiency ratios were significantly affected by Cu in a dose-dependent manner. The highest level of Cu was accumulated in the whole body, muscle, liver, and gills of fish fed 2 mg/kg of Cu. The carcass composition of Striped catfish showed higher protein content in groups received 0.5, 1, and 2 mg/kg Cu in a linear and quadratic manner (p=0.001). The ash content was quadratically increased in Striped catfish fed 2 mg/kg Cu (p=0.001). However, no marked effects were observed on the moisture and lipid contents and the somatic indices (p>0.05). The incorporation of Cu showed meaningfully increased superoxide dismutase, catalase, and glutathione peroxidase but decreased malondialdehyde level in Striped catfish. The villous height exhibited visible growth and branching with increased doses of Cu without a significant increase in the goblet cells. No abnormal features were observed in the liver and hepatocytes of fish treated with Cu. It can be concluded that Cu is required at 1-2 mg/kg for better performances of Striped catfish.

Health benefits and potential applications of fucoidan (FCD) extracted from brown seaweeds in aquaculture: An updated review

Nowadays, the application of immunomodulators in aquaculture has become of an urgent need because of high incidence of fish and shrimp diseases. For a long time, researchers have paid great interest to find suitable, relatively economical, and environmentally safe immunostimulant products to be used either as feed or water additives to boost immunity and increase the resistance of fish and shrimp against the challenging pathogens. Probiotics, prebiotics, synbiotics, phytobiotics, herbal extracts, microalgae, macroalgae, and essential oils have been extensively evaluated. Brown seaweeds (Phaeophyceae) are a large group of multi-cellular macroalgae that are widely distributed in marine aquatic environments. They are abundant in several bioactive sulfated polysaccharides known as fucoidan (FCD). Research studies demonstrated the beneficial functions of FCD in human medicine because of its immunomodulating, antioxidant, anti-allergic, antitumor, antiviral, anti-inflammatory, and hepatoprotective effects. In aquaculture, several researchers have tested the benefits and potential applications of FCD in aquafeed. This literature review provides an updated information and key references of research studies that focused principally on using FCD in aquaculture. Its effects on growth, intestinal health, antioxidant capacity, and immune responses of several finfish and shellfish species will be discussed. This review paper will also highlight the potential efficacy and mechanisms of FCD in the modulation of toxicity signs and increasing the resistance of fish and shrimp against bacterial and viral infections. Hence, this contribution will be valuable to maintain aquaculture sustainability and to improve the health and welfare of farmed fish and shrimp.

Modulation of Antioxidant Defense in Farmed Rainbow Trout (Oncorhynchus mykiss) Fed with a Diet Supplemented by the Waste Derived from the Supercritical Fluid Extraction of Basil (Ocimum basilicum)

Phytotherapy is based on the use of plants to prevent or treat human and animal diseases. Recently, the use of essential oils and polyphenol-enriched extracts is also rapidly increasing in the aquaculture sector as a means of greater industrial and environmental sustainability. Previous studies assessed the antibacterial and antiparasitic effects of these bioactive compounds on fish. However, studies on the modulation of oxidative stress biomarkers are still scant to date. Thus, in this study, the modulation of antioxidant defense against oxidative stress exerted by fish diets supplemented with a basil supercritical extract (F1-BEO) was assessed in rainbow trout Oncorhynchus mykiss. The F1-BEO extracted with supercritical fluid extraction was added to the commercial feed flour (0.5, 1, 2, 3% w/w) and mixed with fish oil to obtain a suitable compound for pellet preparation. Fish were fed for 30 days. The levels of stress biomarkers such as superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase, glutathione reductase, glyoxalase I, glyoxalase II, lactate dehydrogenase, glutathione and malondialdehyde showed a boost in the antioxidant pathway in fish fed with a 0.5% F1-BEO-supplemented diet. Higher F1-BEO supplementation led to a failure of activity of several enzymes and the depletion of glutathione levels. Malondialdehyde concentration suggests a sufficient oxidative stress defense against lipid peroxidation in all experimental groups, except for a 3% F1-BEO-supplemented diet (liver 168.87 ± 38.79 nmol/mg prot; kidney 146.86 ± 23.28 nmol/mg prot), compared to control (liver 127.76 ± 18.15 nmol/mg prot; kidney 98.68 ± 15.65 nmol/mg prot). Our results suggest supplementing F1-BEO in fish diets up to 0.5% to avoid potential oxidative pressure in farmed trout.

Progress in Alternative Strategies to Combat Antimicrobial Resistance: Focus on Antibiotics

Antibiotic resistance, and, in a broader perspective, antimicrobial resistance (AMR), continues to evolve and spread beyond all boundaries. As a result, infectious diseases have become more challenging or even impossible to treat, leading to an increase in morbidity and mortality. Despite the failure of conventional, traditional antimicrobial therapy, in the past two decades, no novel class of antibiotics has been introduced. Consequently, several novel alternative strategies to combat these (multi-) drug-resistant infectious microorganisms have been identified. The purpose of this review is to gather and consider the strategies that are being applied or proposed as potential alternatives to traditional antibiotics. These strategies include combination therapy, techniques that target the enzymes or proteins responsible for antimicrobial resistance, resistant bacteria, drug delivery systems, physicochemical methods, and unconventional techniques, including the CRISPR-Cas system. These alternative strategies may have the potential to change the treatment of multi-drug-resistant pathogens in human clinical settings.

Influences of spent coffee grounds on skin mucosal and serum immunities, disease resistance, and growth rate of Nile tilapia (Oreochromis niloticus) reared under biofloc system

The study was executed to find out the potential effects spent coffee ground (SCG) on Nile tilapia's skin mucosal and serum immunities, disease prevention, and growth rate reared in a biofloc system. Nile tilapia fingerlings (average weight 15.25 ± 0.07 g) were disseminated into 15 aquaria (150 L tank^-1) at a density of 20 fish per aquarium and treated five diets: SCG1 (control), SCG2 (10 g kg^-1), SCG3 (20 g kg^-1), SCG4 (40 g kg^-1), and SCG5 (80 g kg^-1) for eight weeks. A Completely Randomized Design (CRD) with three replications was applied. Growth rate, skin mucus, and serum immunities were quantified every 4 weeks; whereas the challenge study was conducted at the termination of the feeding trial. The outputs indicated that dietary incorporation of SCG give rise to the enhancement of SGR and FCR in comparison with the control, with best levels noted in fish fed SCG2 diet. Similarly, significant enhancements in skin mucosal and serum immunities were revealed in fish treated SCG2 over the control and other SCG diets. Likewise, higher survival rates against Streptococcus agalactiae were displayed in fish fed SCG, with the maximum level displayed in the fish treated SCG2. In conclusion, dietary supplementation of SCG2 (10 g kg^-1) can be potential used as immunostimulants in tilapia aquaculture.

Effects of dietary tea tree oil on the growth, physiological and non-specific immunity response in the giant freshwater prawn (Macrobrachium rosenbergii) under high ammonia stress

This study aimed to investigate the effects of dietary tea tree oil (TTO) on the performance, intestinal antioxidant capacity, and non-specific immunity after ammonia nitrogen stress in Macrobrachium rosenbergii. Six experimental diets were formulated with 0, 25, 50, 100, 200, 400 mg/kg TTO, respectively. A total of 900 prawns (average initial weight, 0.39 ± 0.01 g) were randomly assigned to 6 groups in triplicate in 18 tanks. After an 8-week feeding trial, 20 prawns from each tank were changed with 20 mg/L ammonia stress for 24 h. The results showed that 100 mg/kg TTO significantly increased prawns performance and survival rate compared with the control group. Moreover, 100 and 200 mg/kg TTO significantly improved intestinal antioxidant capabilities by increasing SOD enzyme activities and decreasing MDA levels. In addition, the prawns fed with 100 mg/kg TTO diet showed the highest survival rate under ammonia stress. After ammonia stress, the group of 100 mg/kg TTO significantly improved antioxidant capacity by increasing hemolymph respiratory burst activity, as well as intestinal anti-superoxide anion activity and SOD. Coincidentally, 100 mg/kg TTO significantly upregulated the intestinal relative expression of antioxidant-related genes (peroxiredoxin-5). Further, it was found that 100 mg/kg TTO activated the toll-dorsal pathway in prawns, which performed the similar function as the classic NF-κB pathway by upregulating the TNF-α and IL-1. Finally, 100 mg/kg TTO increased the levels of iNOS activities and NO contents after ammonia stress and enhanced non-specific immunity. The results indicated that 100 mg/kg TTO could significantly improve the M. rosenbergii performance, antioxidant capacity and ammonia stress resistance. We suggested that the mechanisms may be attributed to that TTO enhanced the antioxidant capacity and non-specific immunity of M. rosenbergii via the NF-κB signal pathway.

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.

Mannan Oligosaccharide Enhanced the Growth Rate, Digestive Enzyme Activity, Carcass Composition, and Blood Chemistry of Thinlip Grey Mullet (Liza ramada)

Simple Summary

Sustainable aquaculture requires natural alternative substances with high potential in enhancing the performance and wellbeing of aquatic animals. In this regard, the present study tested the possibility of using mannan oligosaccharides (MOS) in the diets of grey mullet as functional additives. For 8 weeks, fish were fed with enriched diets containing 0, 0.5, 1, and 2% MOS. The results showed marked improvements in the growth performance, digestive enzyme activity, blood chemistry, and antioxidative capacity. In conclusion, dietary MOS at 0.5–1% is required to enhance the productivity of grey mullet.

Abstract

Mannan oligosaccharide (MOS) is prebiotic with high functionality in aquaculture. The current study investigated the potential roles of MOS on the growth performance, digestive enzyme activity, carcass composition, and blood chemistry of Thinlip grey mullet (Liza ramada). Four tested diets with 34.49% crude protein and 6.29% of total lipids were prepared and fortified with 0, 0.5, 1, and 2% MOS. Fish of initial weight = 5.14 ± 0.11 g/fish were distributed in 12 hapas (0.5 × 0.5 × 1 m) at 15 fish per hapa (triplicates) and fed the test diets to the satiation level two times a day (08:00 and 15:00) for eight weeks. At the end of the trial, all fish were weighed individually for growth performance calculation. Blood was collected to check blood chemistry traits, and intestines were dissected for digestive enzyme analysis. Fish treated with MOS had marked enhancement in the final body weight, feed conversion ratio, protein gain, and protein retention regardless of inclusion dose (p < 0.05). The weight gain, specific growth rate, and protein efficiency ratio were meaningfully enhanced by including MOS at 0.5 and 1%, followed by fish fed with 2% MOS, while the lowest values were in the control group (p < 0.05). Insignificant influences of MOS were seen on the chemical composition of carcass components (moisture, crude protein, total lipids, and ash) (p > 0.05). Fish treated with MOS at 0.5 and 1% had marked enhancement in the amylase, lipase, and protease activities regardless of inclusion dose (p < 0.05). The blood total protein and albumin levels were meaningfully enhanced by including MOS at 0.5 and 1%, followed by fish fed with 2% MOS, while the lowest values were in the control group (p < 0.05). The blood globulin was significantly enhanced in fish fed 1% MOS than fish treated with 0, 0.5, and 2% of MOS (p < 0.05). The blood lysozyme activity was meaningfully enhanced by including MOS at 1%, followed by fish treated with 0.5 and 2%, while the lowest values were in the control group (p < 0.05). Phagocytic activity and phagocytic index were markedly improved in fish treated with 1 and 2% MOS, followed by those fed 0.5% compared with fish fed MOS-free diet (p < 0.05). Superoxide dismutase and glutathione peroxidase were markedly improved in fish treated with 1, and 2% MOS, followed by those fed 0.5% compared with fish fed MOS-free diet (p < 0.05). Dietary MOS (0.5, 1, and 2%) meaningfully enhanced catalase activity while decreased the malondialdehyde concentration (p < 0.05). In summary, dietary MOS is required at 0.5–1% for enhancing the growth rate, feed efficiency, digestive enzyme activity, blood chemistry, and antioxidative capacity of grey mullet.

Efficacy and residual effect of Illicium verum (star anise) and Pelargonium graveolens (rose geranium) essential oil on cat fleas Ctenocephalides felis felis

The essential oils (EOs) of Illicium verum and Pelargonium graveolens were evaluated for lethality, inhibition of development and residual efficacy against the flea Ctenocephalides felis felis. Their chemical composition was characterized by means of gas chromatography with a flame ionization and mass spectrometry detection. Mortality at different immature stages and among adult fleas was measured through in vitro filter paper tests at different concentrations of EOs. The chemical characterization of I. verum volatile oil showed that E-anethole (79.96%) was the major constituent, while the major compounds in P. graveolens were citronellol (29.67%) and geraniol (14.85%). Insecticidal activity against both immature and adult flea stages were observed. The EO of I. verum had insecticidal activity for approximately 18 days, while the EO activity of P. graveolens lasted for 13 days. The pulicidal activity of I. verum remained above 70% for up to 9 days, while the activity of P. graveolens was 41.7% for up to 2 days. Essential oils, especially that of I. verum, showed insecticidal activity for flea control at different life cycle stages and have potential for the development of ectoparasiticides (biopesticides) for veterinary use.

Selenium nanoparticles are required for the optimum growth behavior, antioxidative capacity, and liver wellbeing of Striped catfish (Pangasianodon hypophthalmus)

Selenium (Se) is a multifunctional trace element required in specific amounts for the optimal growth of aquatic finfish species. For this reason, this study investigated the effect of Se nanoparticles on the growth behavior, antioxidative capacity, and liver wellbeing of Striped catfish (Pangasianodon hypophthalmus). Striped catfish fed varying Se nanoparticles levels (0. 0.5, 1, and 2 mg/kg) in triplicate units and kept for 60 days. Striped catfish delivered dietary Se nanoparticles had markedly increased growth performance, specific growth rate (SGR), consumed feed, and protein efficiency ratio but reduced feed conversion ratio (FCR). The whole body, liver, muscle, and gills have higher Se accumulation levels in fish that received Se nanoparticles than the control with the highest level in fish fed 2 mg/kg. The carcass composition showed higher protein content in fish fed 1 and 2 mg/kg (p = 0.001 and 0.001) and higher ash content (p = 0.001 and 0.002) in fish fed 2 mg/kg than the remaining groups. Superoxide dismutase was meaningfully activated in Striped catfish delivered 1 and 2 mg Se nanoparticles/kg compared with the control (p < 0.05). Also, catalase and glutathione peroxidase activities were higher, and malondialdehyde level was lower in Striped catfish fed Se nanoparticles at 0.5, 1, and 2 mg/kg than the control (p < 0.05). The villi exhibited a visible increase in both height and branching with an increased level of Se nanoparticles in addition to the increased number of goblet cells. The Se nanoparticles-treated fish revealed dose-dependent modifications fluctuated from diffuse fatty vacuolization in hepatocytes with eccentric pyknotic hepatocytes nuclei. In conclusion, Se nanoparticles are required for the optimum growth behavior, antioxidative capacity, and liver wellbeing of Striped catfish. Based on SGR and FCR data's regression analysis, Se nanoparticles are recommended at 1.02-1.11 mg/kg diet.

Potential effects of dietary seaweeds mixture on the growth performance, antioxidant status, immunity response, and resistance of striped catfish (Pangasianodon hypophthalmus) against Aeromonas hydrophila infection

Striped catfish (Pangasianodon hypophthalmus) is one of the important fish species in the world, which is widely cultured in several countries worldwide including Egypt. Aeromonas hydrophila infection showed a high prevalence in the farmed striped catfish negatively affecting its production causing economic loss. Therefore, the finding of functional feed supplements with antimicrobial activity is urgently needed. The use of marine seaweeds as feed supplements has produced satisfactory results as antibacterial agents. Accordingly, the present study was designed to evaluate the dietary effects of seaweeds mixture (Ulva lactuca, Jania rubens, and Pterocladia capillacea) extract (SME) on the growth performance, haemato-chemical parameters, antioxidant capacity, immune indices, and resistance of striped catfish fry against A. hydrophila infection. Four isonitrogenous (30% crude protein) diets were prepared to contain 0.0% (control), 1%, 2%, and 3% SME and were fed to striped catfish fry (1.7 ± 0.1 g) up to apparent satiety three times a day for 60 days. After the feeding trial, fish of each treatment were intraperitoneally injected with a virulent A. hydrophila strain and the relative percentage of survival (RPS) was recorded. The growth-stimulating activity of dietary SME was observed especially at 2% and 3% SME treatments. Similarly, haematological parameters (red blood cells, haemoglobin, haematocrit, and white blood cells) and serum protein profile (total protein, albumin, and globulin) were significantly (P < 0.05) improved, meanwhile serum alanine and aspartate aminotransferases were significantly (P < 0.05) decreased in fish fed with 2 and 3% SME diets. Serum creatinine and uric acid levels revealed no significant (P > 0.05) differences among the experimental groups. Hepatic malondialdehyde and serum nitrous acid levels were significantly decreased; meanwhile hepatic superoxide dismutase, catalase, and glutathione peroxidase levels were significantly increased in all SME-treated groups than the control one. Also, SME supplementations significantly increased the serum lysozyme, total immunoglobulin, and complement C3 activities with highest values at 2% and 3% SME treatments. Interestingly, after bacterial challenge, fish fed SME-supplemented diet were more resistant with the lowest fish mortality (15%) at the 3% SME diet, which exhibit the highest RPS (81.9%). Meanwhile the control group showed highest mortality (85%). According to the regression fitting curve, the current study recommends using the dietary SME with optimum levels of 2.25-2.5% to improve the growth performance, welfare status, and resistance of striped catfish fry against A. hydrophila infection.

Antibacterial and antibiofilm activities and synergism with florfenicol from the essential oils of Lippia sidoides and Cymbopogon citratus against Aeromonas hydrophila

AIMS

Aeromonas hydrophila is an opportunistic bacterium, with a high capacity for biofilm production, which can cause severe damage in aquaculture. The objective of this study was to identify the chemical compounds of the essential oils of Lippia sidoides (EOLS) and Cymbopogon citratus (EOCC), and to evaluate the biocidal, antibiofilm and synergistic action with the antimicrobial florfenicol of these essential oils (EOs) against A. hydrophila.

METHODS AND RESULTS

The antibacterial activity of EOLS and EOCC was verified by the minimum bactericidal concentration and by the action of these EOs against both forming and consolidated biofilms. The synergistic activity of EOs with florfenicol was performed using the checkerboard technique. The main component of EOLS and EOCC was carvacrol (44.50%) and α-citral (73.56%), respectively. Both EOs showed weak inhibitory activity (≥3125.00 µg ml^-1 ). Two bacterial isolates were able to produce biofilm, and EOLS and EOCC acted upon the bacterial isolates to prevent biofilm formation. A bactericidal effect was verified for EOLS in the previously consolidated biofilm for both isolates and for EOCC in only one of the isolates. In general, EOLS had a synergistic effect with florfenicol, while EOCF had an additive effect.

CONCLUSIONS

Both EOs were able to interfere with biofilm formation and did not have an antagonistic effect in combination with florfenicol. The best results were found for EOLS, which showed a synergistic effect with florfenicol and the ability to interfere in the formation of consolidated biofilm.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study highlights the potential of EOLS and EOCC to interfere in biofilm and act in synergy with florfenicol to reduce the occurrence of A. hydrophila. Development of these compounds may contribute to the development of herbal medicines in aquaculture.

The functionality of probiotics in aquaculture: An overview

Probiotics are live beneficial bacteria introduced into the gastrointestinal tract through food or water, promoting good health by enhancing the internal microbial balance. Probiotic microbes produce bacteriocins, siderophores, lysozymes, proteases, and hydrogen peroxides, inhibiting the growth of harmful pathogens. Such beneficial bacteria also produce many enzymes such as amylase enzyme by Aeromonas spp., Bacillus subtilis, Bacteridaceae, Clostridium spp., Lactobacillus plantarum, and Staphylococcus sp., and protease and cellulase enzymes by B. subtilis, L. plantarum, and Staphylococcus sp. In aquaculture, probiotics confer several benefits and play important roles in improving growth performances, disease resistance, immunity, health status, intestinal epithelial barrier integrity, gut microbiome, and water quality. In addition, the practical application of probiotics in aquaculture diets could minimize antibiotic side effects. Promoting these feed additives for fish would help to improve their productive performance and feed utilization and, therefore, boost fish production and safeguard human health. This review provides updated information regarding definitions, sources of bacterial probiotics, probiotic use in fish diets against pathogenic bacteria, mechanisms of action, beneficial aspects, and potential applications of probiotics in fish. It is anticipated that these will be of significant value for nutritionists, agricultural engineers, researchers, pharmacists, scientists, pharmaceutical industries, and veterinarians.

Ginkgo biloba leaf extract improves growth, intestinal histomorphometry, immunity, antioxidant status and modulates transcription of cytokine genes in hapa-reared Oreochromis niloticus

This study was designed to evaluate the impacts of dietary supplementation with Ginkgo biloba leaf extract (GBL) on the growth, intestinal histomorphometry, immunity, antioxidant status, and expression of cytokine genes in Nile tilapia reared in the hapas. A control diet was enriched with different GBL levels (0.0, 5.0, 7.0, and 9.0 g/kg) to form 4 experimental diets and were fed to Nile tilapia for 8 weeks. The findings illustrated that dietary GBL significantly enhanced the growth and feed utilization indices compared to those reared in the control group. A dose-dependent increase of hepatic catalase, superoxide dismutase, and glutathione peroxidase activities alongside a decline of hepatic malondialdehyde levels were recorded in GBL groups compared with the control. Serum lysozyme activity, complement C3, and immunoglobulin M levels were significantly increased in GBL groups compared with the control group. Moreover, dietary GBL maintained the normal intestinal and hepatopancreatic histological structures with a significant increase of some histomorphometric measurements of proximal, middle, and distal intestinal parts of the treated fish. Interestingly, dietary GBL supplementation significantly increased the mRNA expression of interleukin-1 beta (IL-1β), IL-6, IL-10, tumor necrosis factor alpha (TNF-α) and interferon gamma (INF-γ) genes in the splenic tissues of treated fish over the control group. To conclude, it could be recommended to use GBL as a functional phytogenic feed additive to improve the growth, hepatic and intestinal health status, hepatic antioxidant status, and immunity of treated Nile tilapia. Besides, the second order polynomial regression revealed that 7.50 g GBL/kg diet is the optimal inclusion level to improve growth with no negative impacts on the overall health condition of treated Nile tilapia.

A blend of herbal essential oils enhanced the growth performance, blood bio-immunology traits, and intestinal health of Nile tilapia (Oreochromis niloticus)

Nile tilapia fed four levels (0, 0.25, 0.5, and 1 ml/kg) of a liquid blend of herbal essential oils (EOs) contains carvacrol, oregano, 1,8 cineol, thymol, pinene, pinene β, limonene, and propylene glycol for 60 days. The results showed higher final weight, weight gain, and specific growth rate (P<0.05) in fish delivered 0.25 and 0.5 ml EOs/kg than the control. However, the feed conversion ratio was markedly reduced in fish fed 0.5 and 1 ml EOs/kg (P<0.05). Lipase showed enhanced activity in fish subjected to a blend of EOs, while fish fed 0.5 ml/kg of EOs blend had higher amylase activity (P<0.05) than the other levels. Lysozyme activity and superoxide dismutase showed a higher value in fish received 0.5 ml EOs/kg. Additionally, phagocytic and catalase activities enhanced in fish received 0.5 and 1 ml/kg while phagocytic index enhanced in fish fed 1 ml/kg (P<0.05). Interestingly, the total immunoglobulin level was markedly higher, while malondialdehyde was lower in EOs-subjected fish (P<0.05) than in control. The histomorphology appearance of the intestine, liver, and spleen were enriched in EOs-treated fish comparing the control fish. In conclusion, the growth performance, feed efficiency, and blood bio-immunological indices of fish fed 0.5–1 ml of EOs blend per kg had the best performances.

Evaluation of oregano (Origanum vulgare) essential oil supplementation on growth performance, digestive enzymes, intestinal histomorphology and gut microbiota of Black Sea salmon, Salmo labrax

This study aimed to determine the effect of dietary oregano (Origanum vulgare) essential oil (EO) on the growth performance, digestive enzyme activity, intestinal histomorphology, and intestinal microbiota of the Black Sea salmon juvenile (Salmo labrax). Fish fed with diets have at different levels oregano EO such as 50, 100, 200, and 400 mg kg−1. For this purpose, a total of 675 fish were distributed randomly in triplicate into 5 experiment groups in 15 experiment tanks. Fish with average initial weights of 3.52±0.01g were fed by hand 3% level of live weight for 90 days. At the end of the study, feeding with oregano EO supplementation didn’t significantly affected the growth performance of fish. Except for pepsin, there were no significant differences in the activity of digestive enzymes among the control and oregano EO groups. Besides, oregano EO at the doses of 50 or 400 mg kg−1 may have the potential to increase the surface area required for digestion by increasing intestinal villi length. Moreover, all doses of oregano EO showed antimicrobial properties by decreasing the count of lactic acid bacteria in the intestine. Supplementation with 100 and 200 mg kg−1 oregano EO in diets decreased the total coliform, Escherichia coli and lactic acid bacteria counts when compared to the control group. The results showed that oregano EO may affect positively digestion and absorption without adverse effects on the growth performance of Black Sea salmon juvenile.