Effects of probiotics on digestive enzymes of fish (finfish and shellfish); status and prospects: a mini review

Histology and transcriptomic analysis reveal the inflammation and affected pathways under 2-methylisoborneol (2-MIB) exposure on grass carp

2-Methylisoborneol (2-MIB) is a common and widely distributed off-flavor compound in water. However, the toxic mechanisms of 2-MIB on aquatic organisms remain largely unexplored. In this study, grass carp larvae were exposed to different concentrations (0, 5, and 20 μg L-1) of 2-MIB for 96 h. The accumulation of 2-MIB in the dorsal muscle was measured. Histological analysis, ultrastructure observations, and transcriptomic sequencing were conducted on the liver tissues. The results showed that 2-MIB accumulated significantly in the fish muscle, with the accumulation increasing as the exposure concentration increased through gas chromatography-mass spectrometry (GC-MS) detection. Histological and ultrastructure observations indicated that 2-MIB caused concentration-dependent inflammatory infiltration and mitochondrial damage in the liver. Transcriptomic analysis revealed lipid metabolism disorders induced by exposure to 2-MIB in grass carp. Additionally, 5 μg L-1 2-MIB affected the neurodevelopment and cardiovascular system of grass carp larvae through extracellular matrix (ECM)-receptor interaction and focal adhesion pathway. Furthermore, several pathways related to the digestive system were significantly enriched, implying that 2-MIB may impact pancreatic secretion function, protein digestion and absorption processes. These findings provide new insights into the potential toxicological mechanisms of 2-MIB.

Effects of Lactobacillus acidophilus AC on the growth, intestinal flora and metabolism of zebrafish (Danio rerio)

The intensive aquaculture model has resulted in a heightened prevalence of diseases among farmed animals. It is imperative to identify healthy and efficacious alternatives to antibiotics for the sustainable progression of aquaculture. In this investigation, a strain of Lactobacillus acidophilus AC was introduced into the cultural water at varying concentrations (105 CFU/mL, 106 CFU/mL, 107 CFU/mL) to nourish zebrafish (Danio rerio). The findings revealed that L. acidophilus AC effectively increased the growth performance of zebrafish, improved the ion exchange capacity of gills, and enhanced hepatic antioxidant and immune-enzyme activities. Furthermore, L. acidophilus AC notably enhanced the intestinal morphology and augmented the activity of digestive enzymes within the intestinal tract. Analysis of intestinal flora revealed that L. acidophilus AC exerted a significant impact on the intestinal flora community, manifested by a reduction in the relative abundance of Burkholderiales, Candidatus_Saccharibacteria_bacterium, and Sutterellaceae, coupled with an increase in the relative abundance of Cetobacterium. Metabolomics analysis demonstrated that L. acidophilus AC significantly affected intestinal metabolism of zebrafish. PG (i-19:0/PGE2) and 12-Hydroxy-13-O-d-glucuronoside-octadec-9Z-enoate were the metabolites with the most significant up- and down-regulation folds, respectively. Finally, L. acidophilus AC increased the resistance of zebrafish to Aeromonas hydrophila. In conclusion, L. acidophilus AC was effective in enhancing the health and immunity of zebrafish. Thus, our findings suggested that L. acidophilus AC had potential applications and offered a reference for its use in aquaculture.

Effects of Dietary Supplementation with Chitosan on the Muscle Composition, Digestion, Lipid Metabolism, and Stress Resistance of Juvenile Tilapia (Oreochromis niloticus) Exposed to Cadmium-Induced Stress

The aim of this study was to investigate the effects of dietary chitosan supplementation on the muscle composition, digestion, lipid metabolism, and stress resistance, and their related gene expression, of juvenile tilapia (Oreochromis niloticus) subjected to cadmium (Cd2+) stress. Juvenile tilapia with an initial body weight of 21.21 ± 0.24 g were fed with a formulated feed containing five different levels (0%, 0.5%, 1.0%, 1.5%, and 2.0%) of chitosan for 60 days, while the water in all experimental groups contained a Cd2+ concentration of 0.2 mg/L. The results showed that, compared with the control group (0% chitosan), the contents of crude fat and crude protein in the muscle, the activities of lipase, trypsin, and amylase in the intestine, as well as the relative expression levels of metallothionein (mt), cytochrome P450 1A (cyp1a), carnitine palmitoyltransferase-1 (cpt-1), peroxisome proliferator-activated receptor alpha (pparα), peroxisome proliferator-activated receptor gamma (pparγ), hormone-sensitive lipase (hsl), lipoprotein lipase (lpl), malate dehydrogenase (mdh), leptin (lep), fatty acid synthase (fas), sterol regulatory element-binding protein 1 (srebp1), and stearoyl-CoA desaturase (scd) genes in the liver of juveniles were significantly increased (p < 0.05). In conclusion, dietary chitosan supplementation could alleviate the effects of Cd2+ stress on the muscle composition, digestive enzymes, lipid metabolism, and stress resistance, and their related gene expression, of juvenile tilapia, and to some extent reduce the toxic effect of Cd2+ stress on tilapia.

Effects of host-associated low-temperature probiotics in olive flounder (Paralichthys olivaceus) aquaculture

This study investigated the effects of supplementation of low-temperature probiotics isolated from the intestines of olive flounder on the growth performance, digestibility, and regulation of intestinal microbiota and the expression of genes related to growth, immunity, and apoptosis in olive flounder. Bacteria showing high growth at approximately 15-20 °C, which is the temperature of olive flounder culture, were isolated and confirmed to be Pseudomonas species through 16S rRNA gene sequence analysis. Whole-genome sequencing revealed that the strain has a 6,195,122 bp single circular chromosome and a guanine-cytosine content of 59.9%. In the feeding trial, supplementation with 1 × 108 CFU/g of the isolate strain positively modulated growth performances, digestive enzyme activity, and gut microbiota composition of olive flounder. RT-qPCR for the comparison of growth, immunity, and apoptosis-related gene expression levels showed no significant differences between the groups. Therefore, the isolated host-associated low-temperature probiotics improved the growth performance of olive flounder by causing positive changes in digestive activity and intestinal microbial composition without affecting host gene expression.

Effects of Tannic Acid Supplementation of a High-Carbohydrate Diet on the Growth, Serum Biochemical Parameters, Antioxidant Capacity, Digestive Enzyme Activity, and Liver and Intestinal Health of Largemouth Bass, Micropterus salmoides

We investigated the effects of dietary tannic acid (TA) supplementation of a high-carbohydrate diet on growth, feed utilization, whole-body proximate composition, serum biochemical indicators, antioxidant capacity, digestive enzyme activity, and liver and intestinal health of juvenile largemouth bass, Micropterus salmoides (initial mean weight: 8.08 ± 0.08 g). Five diets were prepared, including a positive control (dietary carbohydrate level, 16%, LC0), a negative control (dietary carbohydrate level, 21%, HC0), and three TA-supplementation diets based on the negative control diet with TA addition at 200, 400, and 800 mg/kg, respectively. After 8 weeks of feeding, the results showed that compared with the LC0 diet, 400-800 mg/kg dietary TA significantly improved the survival rate of largemouth bass (P < 0.05) while significantly reducing its weight-gain rate and specific growth rate (P < 0.05). Compared with the HC0 diet, 400 mg/kg dietary TA significantly increased serum catalase activity (P < 0.05), and significantly decreased serum malondialdehyde, liver glycogen, lightness (L ∗), and yellowness (b ∗) (P < 0.05). Moreover, compared with the HC0 diet, 200-400 mg/kg dietary TA effectively improved the vacuolation of hepatocytes caused by the high-carbohydrate diet and reduced the occurrence of intestinal epithelial cell vacuolation and necrosis. In turn, 800 mg/kg dietary TA significantly inhibited protease activity in the pyloric caecum and intestine (P < 0.05). In conclusion, dietary supplementation with TA inhibited protease activity, which resulted in decreased growth performance in largemouth bass. However, it was also found that 200-400 mg/kg TA enhanced the antioxidant capacity of largemouth bass in the case of the high-carbohydrate diet, reduced liver glycogen levels, and improved liver and intestinal health. Finally, it should be noted that, when the dietary TA level exceeded 800 mg/kg, TA appeared to play a pro-oxidation role in the liver, which may cause oxidative stress in the liver.

Feeding Strategies with Multi-Strain Probiotics Affect Growth, Health Condition, and Disease Resistance in Asian Seabass (Lates calcarifer)

A 16-week feeding trial was done to examine the impacts of continuous feeding (CF) or pulse-feeding (PF) of multi-strain probiotics on Asian seabass (Lates calcarifer, 30.0 ± 0.1 g) juveniles. In this study, three different multi-strain probiotic mixtures were added to a basal diet, including (I) a mixture of different strains of Lactobacillus plantarum, (II) a mixture of the first probiotic (I) + L. delbrueckii sub bulgaricus, L. rhamnosus and L. acidophilus, and (III) a mixture of the second probiotic (II) + two quorum quenching (QQ) bacteria (Bacillus thuringiensis QQ1 and B. cereus QQ2). CF (every day) or PF (every two weeks) strategies were applied for using the abovementioned probiotics to design seven experimental groups including C (control, without probiotics), CF-I (continuous feeding of fish with the probiotic mixture I), CF-II (continuous feeding of fish with the probiotic mixture II), CF-III (continuous feeding of fish with the probiotic mixture III), PF-I (pulse-feeding of fish with the probiotic mixture I), PF-II (pulse-feeding of fish with the probiotic mixture II), and PF-III (pulse-feeding of fish with the probiotic mixture III). Four hundred and twenty fish were stocked into 21 circular polyethylene tanks with 220 L volume (20 fish/tank). Each dietary treatment had three replicates. Tanks were supplied with seawater (temperature = 30.5 °C, salinity = 45 g L-1) in a flow-throw system. Fish in CF-I, CF-II, and CF-III had higher growth rate (ca. 113-145%) and better feed conversion ratio than fish fed C and PF-I (P < 0.05). Fish in the CF-III group had the highest protease activity. Continuous feeding strategy resulted in a higher amount of glutathione and catalase activities in both the liver and plasma as well as higher superoxide dismutase activity in the liver of fish. Pulse-feeding strategy resulted in lower plasma lactate dehydrogenase and aspartate aminotransferase levels than the CF strategy. Regardless of feeding strategy, different probiotic mixtures significantly enhanced blood hemoglobin and hematocrit levels compared to the control. Continuous feeding with the multi-strain probiotics resulted in a higher survival rate against Vibrio harveyi than the PF method. Continuous feeding induced higher mRNA transcription levels of granulocyte-macrophage colony-forming cells and interleukin 10 genes in the gut of fish than PF strategy. In conclusion, continuous feeding with multi-strain probiotics is better than pulse-feeding on growth, feed utilization, antioxidant capacity, and the gut's immune-related genes and led to higher resistance of L. calcarifer in challenge with V. harveyi.

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

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

Nanoscale ZnO Improves the Amino Acids and Lipids in Tomato Fruits and the Subsequent Assimilation in a Simulated Human Gastrointestinal Tract Model

With the widespread use of nanoenabled agrochemicals, it is essential to evaluate the food safety of nanomaterials (NMs)-treated vegetable crops in full life cycle studies as well as their potential impacts on human health. Tomato seedlings were foliarly sprayed with 50 mg/L ZnO NMs, including ZnO quantum dots (QDs) and ZnO nanoparticles once per week over 11 weeks. The foliar sprayed ZnO QDs increased fruit dry weight and yield per plant by 39.1% and 24.9, respectively. It also significantly increased the lycopene, amino acids, Zn, B, and Fe in tomato fruits by 40.5%, 15.1%, 44.5%, 76.2%, and 12.8%, respectively. The tomato fruit metabolome of tomatoes showed that ZnO NMs upregulated the biosynthesis of unsaturated fatty acids and sphingolipid metabolism and elevated the levels of linoleic and arachidonic acids. The ZnO NMs-treated tomato fruits were then digested in a human gastrointestinal tract model. The results of essential mineral release suggested that the ZnO QDs treatment increased the bioaccessibility of K, Zn, and Cu by 14.8-35.1% relative to the control. Additionally, both types of ZnO NMs had no negative impact on the α-amylase, pepsin, and trypsin activities. The digested fruit metabolome in the intestinal fluid demonstrated that ZnO NMs did not interfere with the normal process of human digestion. Importantly, ZnO NMs treatments increased the glycerophospholipids, carbohydrates, amino acids, and peptides in the intestinal fluids of tomato fruits. This study suggests that nanoscale Zn can be potentially used to increase the nutritional value of vegetable crops and can be an important tool to sustainably increase food quality and security.

Sustainable Aquafeed Formulations Containing Insect Larval Meal and Grape Marc for the New Zealand Farmed Abalone

The aquaculture industry has been criticised for the excessive use of fish meal (FM) in feeds due to the utilisation of wild fish in the formulation and the exacerbation of overfishing marine resources. Land-based abalone aquaculture mainly uses commercial feeds (CFs) to promote faster growth, which include FM as a primary protein component. Alternative ingredients, such as insect meal (IM) and grape marc (GM) are potential candidates for FM replacement due to their suitable nutritional profile and sustainable production. This paper reports on a novel nutritional approach for the New Zealand farmed abalone, which replaces FM with IM by 10% and includes a waste by-product (GM) by 30% as a potential prebiotic source. The study was performed in two stages: (a) physico-chemical determination of diets delivered in an alginate matrix (experimental diets) and their stability in seawater compared to CF and (b) evaluation of growth and feed intake for the New Zealand black-foot abalone. There were significant differences between experimental diets and CF in terms of sinking rate, particle weight, and microscopic observations. Water stability of the experimental diets was increased by 50% in 24 and 48 hr compared to CF, producing less solid waste, and potentially reducing cleaning efforts in the farm. The inclusion of IM and GM did not compromise overall animal growth or their feed conversion ratio, however, further evaluation need to be explored in the future research. The findings revealed that the developed encapsulated feeds are a more stable food delivery method for Haliotis iris compared to the CF. Furthermore, both IM and GM can be included in feed formulations as a more sustainable strategy without compromising weight and shell gains in the abalone farming.

Functionality of probiotics on the resistance capacity of shrimp against white spot syndrome virus (WSSV)

Shrimp aquaculture is currently regarded as a significant commercial and food production sector due to its growing importance as a source of human-consumable protein, As shrimp farming has become more intensive, disease outbreaks have become more common, necessitating the overuse of antimicrobial drugs, which has had a number of unintended consequences. The white spot syndrome virus (WSSV) is now recognized as one of the world's most pervasive and potentially fatal diseases affecting shrimp. However, there is currently no cure to prevent the disease's uncontrolled incidence and spread. Probiotics are currently favoured over these antimicrobial substances because of their ability to stimulate disease resilience in shrimp farms by strengthening the immune systems naturally. Probiotics for bacterial infections such as vibriosis are well documented, whereas research is still required to identify the legitimate strains for viral diseases. The utilization of these probiotics as a therapy for and preventative measure against WSSV in shrimp farming is a cutting-edge method that has proven to be effective. Some probiotic strains, such as Bacillus spp, Lactobacillus, and Pediococcus pentosaceus, have been displayed to enhance the innate immunity of shrimp against WSSV, reduce viral load, increase digestibility and growth, and support the gut microbiome of the host in multiple investigations. The present review explores recent developments regarding the function of probiotics in shrimp, with a focus on their anti-WSSV activity.

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

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

Dietary artemisinin boosts intestinal immunity and healthy in fat greenling (Hexagrammos otakii)

Introduction

Artemisinin (ART) is very common as a diet additive due to its immunoregulatory activities. Nonetheless, the immunoregulatory mechanism of ART in marine fish remains unknown. This study comprehensively examined the effects and explored the potential mechanism of ART ameliorating intestinal immune disease (IID) in fat greenlings (Hexagrammos otakii).

Methods and results

The targets of ART were screened using the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database. Here, eight putative targets of ART were collected and identified with the Uniprot database, and 1419 IID-associated target proteins were filtered through the Drugbank, Genecards, OMIM, and PHARMGKB Databases. The results of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways point out that ART may have immunoprotective effects by regulating cellular responses to stress, hypoxia, inflammation, and vascular endothelial growth factor stimulus through the hypoxia-inducible factor 1 (HIF-1) signaling pathway. The findings of molecular docking indicated that ART contains one active ingredient and three cross-targets, which showed a kind combination with hypoxia-inducible factor 1-alpha (HIF1-a), transcription factor p65 (RELA), and vascular endothelial growth factor A (VEGF-A), respectively. Furthermore, an ART feeding model was established to assess the ART's immunoprotect effect on the intestine of H.otakii in vivo. The D48 group showed smaller intestinal structural changes after being challenged by Edwardsiella tarda. The supplementation of ART to the diet improved total superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) and reduced the malondialdehyde (MDA) in intestine of H. otakii. The expression of transcription factor p65, HIF1-α, VEGF-A, cyclin D1, matrix metalloprotease 9 (MMP9), monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) was decreased after dietary ART in the intestinal of H. otakii.

Discussion

The present results demonstrated that dietary ART improved antioxidants and immunity, optimized the intestinal structure, and increased resistance to E. tarda through the SOD2/nuclear-factor-kappa- B (NFkB)/HIF1-a/VEGF-A pathway in the intestinal tract of H.otakii. This study integrated pharmacological analysis and experimental validation and revealed the mechanism of ART on IID, which provides insight into the improvement of IID in H. otakii.

Effects of dietary Clostridium butyricum on the growth performance, digestion, and intestinal health of spotted sea bass (Lateolabrax maculatus)

Clostridium butyricum (CB) is known to promote growth, enhance immunity, promote digestion, and improve intestinal health. In this study, we investigated the effects of CB in the feed on growth performance, digestion, and intestinal health of juvenile spotted sea bass. To provide a theoretical basis for the development and application of CB in the feed of spotted sea bass, a total of 450 spotted sea bass with an initial body weight of (9.58 ± 0.05) g were randomly divided into six groups. Gradient levels with 0, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% of CB (1×10⁹ cfu/g) were supplemented into diets, designated as CC, CB1, CB2, CB3, CB4, and CB5, respectively. Each group was fed for 54 days. Our results suggest that dietary 0.2% and 0.3% of CB can significantly increase the weight gain (WG) and specific growth rate (SGR) of spotted sea bass. The addition of CB significantly increased intestinal amylase activity, intestinal villus length, intestinal villus width, and intestinal muscle thickness. Similarly, CB supplementation increased the expression of tumor necrosis factor-α (TNF-α) and interleukin-8 (IL-8). Sequence analysis of the bacterial 16S rDNA region showed that dietary CB altered the intestinal microbiota profile of juvenile spotted sea bass, increasing the dominant bacteria in the intestine and decreasing the harmful bacteria. Overall, dietary addition of CB can improve growth performance, enhance intestinal immunity, improve intestinal flora structure, and comprehensively improve the health of spotted sea bass.

Effects of Replacing Soybean Meal Protein with Chlorella vulgaris Powder on the Growth and Intestinal Health of Grass Carp (Ctenopharyngodon idella)

Chlorella vulgaris (C. vulgaris) powder is a novel non-grain single-cell protein with enormous potential to be a protein source. However, it is poorly studied in aquatic animals. The purpose of the present study was to explore the optimum replacement ratio of C. vulgaris powder and the influence of the substitution of soybean meal with C. vulgaris on grass carp (Ctenopharyngodon idella) in terms of growth performance, intestinal integrity and the microbial community. Five isonitrogenous and isolipidic diets were formulated by replacing 0% (SM, containing 30% soybean meal), 25% (X25), 50% (X50), 75% (X75) and 100% (X100) soybean meal with C. vulgaris. The feeding trial period lasted 8 weeks. At the end of the experimental trial, the X50 group showed higher FW, WGR and PER than the SM group (p < 0.05). The feed conversion ratio (FCR) of the X50 group was significantly lower than that of the SM group (p < 0.05). The X50 group showed the highest value of the goblet cell number, intestinal amylase and trypsin activities when compared with the SM group (p < 0.05). Replacing 50% soybean meal with C. vulgaris improved the intestinal barrier integrity, as evidenced by upregulating zo-1, zo-2 and occluding transcript (p < 0.05), and alleviated oxidative stress by an increased SOD enzymatic activity and transcript level, probably mediated through the Nrf2-keap1 signaling pathway (p < 0.05). Meanwhile, the X50 group enhanced intestinal immunity, as manifested by increased ACP and LZM activities (p < 0.05), and downregulated the tlr-4, tlr-7, tlr-8 and il-6 through the tlr pathway (p < 0.05). The functionally predicting pathways related to the nitrate respiration and nitrogen respiration were observably activated in the X50 group (p < 0.05). The X50 group improved the biological barrier, as manifested by increased Firmicutes and Rhodobacter (p < 0.05). In conclusion, dietary C. vulgaris powder could promote the growth performance of grass carp by restoring intestinal morphology, increasing digestive enzyme activities, improving antioxidant properties and immunity and optimizing the microflora structure. A C. vulgaris powder replacement of 50% soybean meal was recommended as feed for grass carp.

The Probiotic Phaeobacter inhibens Provokes Hypertrophic Growth via Activation of the IGF-1/Akt Pathway during the Process of Metamorphosis of Greater Amberjack (Seriola dumerili, Risso 1810)

Metamorphosis entails hormonally regulated morphological and physiological changes requiring high energy levels. Probiotics as feed supplements generate ameliorative effects on host nutrient digestion and absorption. Thereby, the aim of the present research was to investigate the impact of the probiotic Phaeobacter inhibens as a water additive on cellular signaling pathways in the metamorphosis of greater amberjack (Seriola dumerili). Activation of insulin-like growth factor type 1 receptor (IGF-1R), protein kinase B (Akt), mitogen-activated protein kinases (MAPKs) and AMP-activated protein kinase (AMPK), induction of heat shock proteins (Hsps), and programmed cell death were assessed through SDS-Page/immunoblot analysis, while energy metabolism was determined through enzymatic activities. According to the results, greater amberjack reared in P. inhibens-enriched water entered the metamorphic phase with greater body length, while protein synthesis was triggered to facilitate the hypertrophic growth as indicated by IGF-1/Akt activation and AMPK inhibition. Contrarily, MAPKs levels were reduced, whereas variations in Hsps response were evident in the probiotic treatment. Apoptosis and autophagy were mobilized potentially for the structural remodeling processes. Furthermore, the elevated enzymatic activities of intermediary metabolism highlighted the excess energy demands of metamorphosis. Collectively, the present findings demonstrate that P. inhibens may reinforce nutrient utilization, thus leading greater amberjack to an advanced growth and developmental state.

Effects of Dietary Lactic Acid Supplementation on the Activity of Digestive and Antioxidant Enzymes, Gene Expressions, and Bacterial Communities in the Intestine of Common Carp, Cyprinus carpio

The present study investigated the effects of dietary lactic acid (LA) supplementation on the growth performance, intestinal digestive/antioxidant enzymes' activities, gene expression, and bacterial communities in common carp, Cyprinus carpio. Four diets were formulated to contain 0 g/kg LA (control), at 2.5 g/kg LA (2.5LAC), 5 g/kg LA (5LAC), and 10 g/kg LA (10LAC) and offered to the fish over a period of 56 days. The results showed that dietary 5 g/kg LA supplementation improved growth performance and feed efficiency in the fish. All LA treatments exhibited significant elevations in the intestinal trypsin and chymotrypsin activities, whereas the intestinal lipase, amylase, and alkaline phosphatase activities exhibited significant elevations in the 5LAC and 10LAC treatments. All LA treatments exhibited significant elevations in the intestinal heat shock protein 70, tumor necrosis factor-alpha, interleukin-1 beta, and defensin gene expressions, and the highest expression was observed in the 5LAC treatment. Additionally, dietary LA treatment significantly increased the lysozyme expression and Lactobacillus sp. population in the intestine of the fish, and the highest values were observed in the 5LAC and 10LAC treatments. Aeromonas sp. and Vibrio sp. populations decreased in the LA treatments, and the lowest Aeromonas sp. population was observed in the 10LAC treatment. The intestinal mucin2 and mucin5 expressions, and the hepatic reduced glutathione content, significantly increased, whereas hepatic glutathione peroxidase, glutathione reductase, and malondialdehyde significantly decreased in the 5LAC and 10LAC treatments. In conclusion, dietary 5 g/kg LA is recommended for common carp feeding to improve growth rate, antioxidant capacity, and intestinal health.

Effects of Astragalus membranaceus Polysaccharides on Growth Performance, Physiological and Biochemical Parameters, and Expression of Genes Related to Lipid Metabolism of Spotted Sea Bass, Lateolabrax maculatus

This experiment investigated the effects of Astragalus membranaceus polysaccharides (AMP) on growth, physiological and biochemical parameters, and the expression of lipid metabolism-related genes in spotted sea bass, Lateolabrax maculatus. A total of 450 spotted sea bass (10.44 ± 0.09 g) were divided into six groups and were given diets with different levels of AMP (0, 0.2, 0.4, 0.6, 0.8, and 1.0 g/kg) for 28 days, respectively. Results indicated that dietary intake of AMP significantly improved fish weight gain, specific growth rate, feed conversion, and trypsin activity. Meanwhile, fish fed with AMP manifested significantly higher serum total antioxidant capacity and activity of hepatic superoxide dismutase, catalase, and lysozyme. Lower triglyceride and total cholesterol were noted in fish fed with AMP (P < 0.05). Moreover, hepatic ACC1 and ACC2 were downregulated by dietary intake of AMP, and PPAR-α, CPT1, and HSL were upregulated accordingly (P < 0.05). Parameters with significant difference were analyzed by quadratic regression analysis, and results showed that 0.6881 g/kg of AMP is the optimal dosage for spotted sea bass in size (10.44 ± 0.09 g). In conclusion, dietary intake of AMP can improve the growth, physiological status, and lipid metabolism of spotted sea bass, thereby indicating its promise as a potential dietary supplement.

Lycium barbarum polysaccharides improve lipid metabolism disorders of spotted sea bass Lateolabrax maculatus induced by high lipid diet

This experiment explored the effects of Lycium barbarum polysaccharides (LBP) on lipid metabolism of spotted sea bass Lateolabrax maculatus. Blank and experimental control diets with 100 and 150 g/kg lipid were designed, respectively, and three dosages of LBP (0.75, 1.00, 1.25 g/kg) were supplemented in the experimental control diet. A total 375 of spotted sea bass (19.33 ± 0.15) g were divided into 5 groups, and were given experimental diets for 56 days, respectively. Results showed fish were induced to lipid metabolism disorders with dietary 150 g/kg lipid intake, which manifested in reduced feeding, oxidative stress, elevated serum lipid, and more severe hepatic damage. Dietary LBP improved the lipid metabolism disorders of fish, as indicated by significant enhancements in weight gain, digestion, superoxide dismutase activity, and decreases in malonaldehyde content, and activity of alanine aminotransferase and aspartate aminotransferase. Accordingly, an improvement in the hepatic morphological and expression of lipid metabolism related genes, including FAS, PPAR-α, CPT1 and ATGL, was observed. Nevertheless, no significant variation in serum triglyceride and total cholesterol was observed. Overall, dietary LBP can improve the growth, digestion, antioxidant capacity, and liver health of spotted sea bass, thereby improving the lipid metabolism disorders induced by 150 g/kg dietary lipid intake.

Dietary supplementation of multi-strain probiotic in male rainbow trout (Oncorhynchus mykiss) broodstock: Effects on feed efficiency, hemato-biochemical parameters, immune response, and semen quality

The present study aimed to determine the effects of dietary probiotic supplementation on feed efficiency, physiological parameters, and semen quality of male rainbow trout (Oncorhynchus mykiss) broodstock. For this purpose, a total of 48 breeders with an average initial weight of 1366.1 ± 33.8 g were divided into 4 groups and 3 replicates. Fish were fed with diets containing 0 (control), 1 × 10⁹ (P1), 2 × 10⁹ (P2), and 4 × 10⁹ (P3) CFU multi-strain probiotic kg^-1 diet for 8 weeks. According to the results, P2 treatment significantly enhanced body weight increase, specific growth rate, and protein efficiency ratio and decreased feed conversion ratio. Moreover, the highest values of red blood cells count, hemoglobin, and hematocrit values were observed in P2 treatment (P < 0.05). The lowest levels of glucose, cholesterol, and triglyceride were found in P1, P2, and P3 treatments, respectively. Also, the highest levels of total protein and albumin were obtained in P2 and P1 treatments (P < 0.05). Based on the results, plasma enzymes contents were significantly decreased in P2 and P3 treatments. In terms of immune parameters, the complement component 3, complement component 4, and immunoglobulin M levels were increased in all probiotic-fed treatments (P < 0.05). For spermatological features, the highest spermatocrit value, sperm concentration, and motility time were observed in the P2 treatment (P < 0.05). Consequently, we conclude that multi-strain probiotics can be used as functional feed additives in male rainbow trout broodstock to enhance semen quality, improve physiological responses, and better feed efficiency.

Rosmarinic acid alone or in combination with Lactobacillus rhamnosus ameliorated ammonia stress in the rainbow trout, Oncorhynchus mykiss: growth, immunity, antioxidant defense and liver functions

Rosmarinic acid (RS) and Lactobacillus rhamnosus (LR) were added singularly or in combination to rainbow trout (Oncorhynchus mykiss) diets to test their efficacy in the protection against ammonia stress. Fish (31.4±0.6 g) were randomly allocated to six groups in three replicates, as follows: T1: basic food as control, T2: LR with a concentration of 1.5 × 108 CFU/g, T3: LR with a concentration of 3 × 108 CFU/g, T4: 1 g RS/kg, T5: 3 g RS/kg, and T6: 1.5 × 108 CFU/g LR + 1 g RS/kg and T7: 3 × 108 CFU/g LR + 3 g RS/kg. After 60 days feeding, fish exposed to 0ammonia stress. After the feeding period, the supplemented fish had the highest final body weight (FW), weight gain (WG), and specific growth rate (SGR), and the lowest feed conversion ratio (FCR) as compared with the control group (P<0.05). Amylase, protease and lipase activities were noticed markedly higher in fish supplemented with 1.5 × 108 CFU/g LR + 1 g RS/kg and 1.5 × 108 CFU/g LR diets compared to the control (P<0.05). Generally, fish in supplemented diets, particularly T2 and T6 groups, had the highest lysozyme, alternative complement activity (ACH50), total Ig, nitroblue tetrazolium test (NBT), myeloperoxidase (MPO), complement component 3 (C3), complement component 4 (C4), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx). On the other hand, T2 and T6 groups had the lowest malondialdehyde (MDA), glucose, and cortisol concentrations as well as alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH) enzyme levels when were compared with the control (P<0.05). After ammonia stress, fish in the supplemented groups, particularly T2 and T6, generally showed significantly higher values of lysozyme, ACH50, total Ig, NBT, MPO, C3, C4, SOD, CAT, GPx and lower levels of MDA, glucose, cortisol, ALT, ALP, LDH when compared with the control (P<0.05). In conclusion, a combined administration of RS and L. rhamnosus effectively improved growth performance and health status as well as enhanced the resistance of rainbow trout against ammonia toxicity.

Combined effects of Spirulina platensis and Pediococcus acidilactici on the growth performance, digestive enzyme activity, antioxidative status, and immune genes in zebrafish

The combined effects of Spirulina platensis (SP) and Pediococcus acidilactici (PA) on growth performance, digestive enzyme activity, antioxidative status, and immune genes in zebrafish were investigated in the present study. Four experimental diets were designed: control and three test diets mixed with SP at 2.5%, PA at 107 CFU/g, or a combination of 2.5% SP and 107 CFU/g PA. After 56 days, fish treated with PA and SP mixture had higher final weight, weight gain, SGR, and lower FCR than fish fed the control and SP diets (P<0.05). The results also illustrated that fish fed PA, SP, and their mixture had higher (P<0.05) protease and amylase activities than the control. The lipase activity was significantly higher in fish treated with PA or the mixture of PA and SP than in the control (P<0.05). The alternative complement pathway (ACH50) and lysozyme activity in the mucus samples of fish treated with PA or both PA and SP were significantly higher (P<0.05) than in fish treated with the control and SP diets. The total immunoglobulin level in the skin mucus was significantly higher (P<0.05) in fish fed PA than in control. In the body homogenates samples, the lysozyme activity and immunoglobulin levels were markedly higher (P<0.05) in fish treated with the mixture of PA and SP than in the control. The dietary PA and SP diet mixture improved the glutathione peroxidase, superoxide dismutase, and total antioxidative capacity. The expression of IL-1β and IL-8 genes in fish treated with PA or the mixture of PA and SP was significantly higher (P<0.05) than in fish treated with the control or SP diets. Fish treated with PA, SP, or both PA and SP had marked (P<0.05) upregulation of the lysozyme gene expression. In conclusion, the mixture of S. platensis and P. acidilactici is more effective than using each individually for improving the growth performance, digestive enzyme activity, and the immune and antioxidative capacity of zebrafish.

The Probiotic Lactobacillus sakei Subsp. Sakei and Hawthorn Extract Supplements Improved Growth Performance, Digestive Enzymes, Immunity, and Resistance to the Pesticide Acetamiprid in Common Carp (Cyprinus carpio)

This study evaluated the impacts of the probiotic, Lactobacillus sakei (L. sakei), and the extract of hawthorn, Crataegus elbursensis, on growth and immunity of the common carp exposed to acetamiprid. Fish (mean ± SE: 11.48 ± 0.1 g) feeding was done with formulated diets (T ₁ (control): no supplementation, T ₂: 1 × 10⁶ CFU/g LS (Lactobacillus sakei), T3: 1 × 10⁸ CFU/g LS, T ₄: 0.5% hawthorn extract (HWE), and T ₅: 1% HWE) for 60 days and then exposed to acetamiprid for 14 days. The growth performance improved in the fish fed LS at dietary level of 1 × 10⁸ CFU/g, even after exposure to acetamiprid (P < 0.05). Intestinal Lactobacillus sakei (CFU/g) load increased (P < 0.05), following supplementation with the probiotic-enriched diet. The LS-treated fish had increases in the activity of digestive enzymes (P < 0.05). Both LS and HWE stimulated antioxidant enzymes and immune system components in serum and mucus (alkaline phosphatase (ALP), protease, total Ig, and lysozyme) (P < 0.05). However, the changes were different depending on the kind of the supplement. The malondialdehyde (MDA) levels decreased in HWE-treated fish after acetamiprid exposure (P < 0.05). Both LS and HWE reduced the liver metabolic enzymes (LDH, ALP, AST, ALT, and LDH) in serum both before and after exposure to the pesticide (P < 0.05). However, each enzyme exhibited a different change trend depending on the type of the supplement. HWE showed a stress-ameliorating effect, as glucose and cortisol levels declined in the HWE-treated fish (P < 0.05). This study indicated the immunomodulatory impacts of LS (1 × 10⁸ CFU/g) and HWE (at dietary levels of 0.5-1%). The probiotic showed more performance compared to HWE. However, the HWE mitigated oxidative stress more efficiently than the probiotic.

Integrated physiological, biochemical, and transcriptomic analysis of thallium toxicity in zebrafish (Danio rerio) larvae

Although several studies have evaluated the effects of Thallium (Tl) in adult species of fish, the developmental toxicity of Tl has not been previously explored. In this study, zebrafish embryos (<4 h post fertilization (hpf)) were exposed to Tl at concentrations from 0.8 to 400 μg L^-1 for 7 d. The results showed that the decreased hatching rate and increased malformation rate were observed in the larvae. The swimming velocity of larvae from 200 and 400 μg L^-1 treatments was respectively reduced by ~26 % and 15 %. Histopathological analysis of liver indicated the number of cells of karyolysis (143 % and 202 %) and pyknosis (170 % and 131 %) were respectively increased in 200 and 400 μg L^-1 Tl treatments. Meanwhile, the Tl body burden and metallothionein (MT) levels in the larvae were increased with elevated Tl concentrations. The level of malondialdehyde (MDA) was increased by ~20 to 51 % in all Tl treatments and total antioxidant capacity (TAC) was decreased by ~12 % at 200 μg L^-1. The activities of Na⁺/K⁺-ATPase and protease were inhibited in 200 and 400 μg L^-1 Tl treatments. Moreover, the transcripts of genes (Nrf2, HO-1, TNF-α, IL-1β, IL-8, IL-10, TGF) were significantly altered. In addition, a total of 930 differentially expressed genes (DEGs) and 1549 DEGs were found in the 200 and 400 μg L^-1 treatments with 458 overlapped DEGs by transcriptomic analysis. The protein digestion and absorption, ECM-receptor interaction, and complement and coagulation cascades pathways were shown to be the most significantly enriched pathways. This study helps better understand the molecular mechanisms of Tl toxicity in fish.

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

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

The dietary mixture of betaine, lactic acid bacteria, and exogenous digestive enzymes enhanced the growth performance, intestinal health, and immunity of Nile tilapia (Oreochromis niloticus) grown in outdoor concrete tanks

It has been illustrated that using mixtures of feed additives is more efficient than using individual additives in aquaculture. Hence, this study aimed to study a dietary mixture of betaine, lactic acid bacteria, and exogenous digestive enzymes (BLE) on the growth performance, digestion capacity, intestinal health, and blood indices of Nile tilapia reared outdoors in concrete tanks. Five diets were prepared where the basal diets mixed with BLE at 0, 0.25, 0.5, 0.75, and 1%. After 90 days, the growth performance of Nile tilapia-fed BLE was markedly enhanced in fish fed 0.25 and 0.5% of BLE, while the feed conversion ratio (FCR) was reduced (P<0.05). The lipase activity was significantly higher in tilapia fed BLE at 0.25, 0.5, and 0.75% than 0 and 1%. The amylase activity was meaningfully increased by 0.5% of BLE than 0, 0.25, 0.75, and 1%. The protease activity was significantly higher in tilapia fed BLE at 0.25 and 0.5 than 0, 0.75, and 1% (P<0.05). The intestine of fish fed on BLE showed an increase in intestinal villi density. The villi length, width, and the number of goblet cells were markedly higher in the anterior, middle, and posterior segments of the intestines of tilapia fed BLE than in the control group (P<0.05). Further, fish fed BLE had higher intestinal morphometry indices and count of goblet cells than the control. Significantly fish fed 0.25, and 0.5% of BLE had higher hemoglobulin, and hematocrit levels than fish fed 0, 0.75, and 1%. While, fish fed 0.5% had higher red blood cells than fish fed the remaining BLE levels (P<0.05). On the other hand, no marked effects for BLE supplementation were seen on the alanine aminotransferase (ALT), aspartate aminotransferase (AST), total protein, albumin, globulin, creatinine, uric acid, and urea. The regression analysis showed that the maximum dose of BLE supplementation to achieve the highest final weight and the lowest FCR is 0.46% and 0.42%, respectively.

The multi-enzymes and probiotics mixture improves the growth performance, digestibility, intestinal health, and immune response of Siberian sturgeon (Acipenser baerii)

The inclusion of exogenous digestive enzymes and probiotics is well established in the aquafeed industry. The mixture of multienzymes and probiotics improves the feed utilization and wellbeing of aquatic animals than the individual supplementation. Herein, we evaluated the exogenous multi-enzyme mixture (beta-glucanase, cellulase, alfa-amylase, protease, xylanase, and phytase) at 250 mg/kg and multi-species probiotic (Bacillus subtilis, Lactobacillus acidophilus, L. delbrueckii, L. rhamnosus, L. plantarum, and Pediococcus acidilactici; 1 × 1010 CFU/g for each bacterial strain) at 2 g/kg on the performances of Siberian sturgeon. The final weight, weight gain, SGR, and PER were markedly enhanced while the FCR was reduced in fish fed multienzyme and probiotics premix (P<0.05). Multi enzymes and probiotic mixture significantly increased the total body protein content (P˃0.05). Multi enzymes and probiotic mixture also improved the digestibility of crude protein, dry matter, and crude lipids nutrients (P<0.05). The count of Goblet cells, microvilli diameter, microvilli length, outer muscle wall diameter, and enterocyte total absorptive surface were markedly increased (P<0.05) by dietary multienzymes and probiotics mixture. The WBCs and neutrophils showed marked improvements (P<0.05). The levels of glucose, triglycerides, blood urea nitrogen, and total bilirubin were markedly higher in fish fed the control than fish fed the multienzymes and probiotics mixture (P<0.05). Significantly, Siberian sturgeon-fed dietary multienzymes and probiotics had improved lysozyme activity, total immunoglobulin, and total protein in the skin mucus and serum samples (P<0.05). Further, the serum complement C3 and C4 was higher in fish-delivered multienzymes and probiotic mixture than in control (P<0.05). In conclusion, dietary probiotics synergistically enhanced the activity of multienzymes and resulted in increased feed utilization, nutrient digestibility, and health status of Siberian sturgeon.

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

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