Beneficial effects of dietary probiotics mixture on hemato-immunology and cell apoptosis of Labeo rohita fingerlings reared at higher water temperatures

Short-term starvation at different feeding regimes on appetite responses, feeding utilization and physiological indices, of red hybrid tilapia (Oreochromis mossambicus × Oreochromis niloticus) fingerlings reared in brackish water

A 42 day factorial trial (3x2) was designed to evaluate the effect of short-term starvation with different feeding frequencies on performance, feed utilization, physiological status and appetite responses of red hybrid tilapia fingerlings. Eighteen plastic tanks with a capacity of (55 L) were used to accomplish this work. Fingerlings with an average initial weight of 23 g ± 0.2 (SE) were randomly stocked at a rate of 8 fingerlings/aquarium. Six groups were designated as the following: II/ED: fish was fed twice every day; IV/ED: fish fed four times every day; II/EOD: fish fed twice every other day (alternate-day feeding or one day of feeding followed by another of fasting); IV/EOD: was fed four times every other day; II/EO3D: fish fed twice every other three days (three day of feeding followed by another of fasting) and IV/EO3D: fish fed four times every other three days. Fish were fed on commercial diets 30 % protein (4 % of biomass). Results showed insignificant differences between fish fed every other day and those fed every day in some growth indicators. In the same trend, the interaction between feed deprivation and feeding frequency cleared that fingerlings of IV/EOD did not significantly differ with those fed every day in growth indices. Moreover this treatment was the best in feed conversion efficiency and several physiological indicators.

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.

Utilisation of probiotics for disease management in giant freshwater prawn (Macrobrachium rosenbergii): Administration methods, antagonistic effects and immune response

The giant freshwater prawn (Macrobrachium rosenbergii) is a high-yielding prawn variety well-received worldwide due to its ability to adapt to freshwater culture systems. Macrobrachium rosenbergii is an alternative to shrimp typically obtained from marine and brackish aquaculture systems. However, the use of intensive culture systems can lead to disease outbreaks, particularly in larval and post-larval stages, caused by pathogenic agents such as viruses, bacteria, fungi, yeasts and protozoans. White tail disease (viral), white spot syndrome (viral) and bacterial necrosis are examples of economically significant diseases. Given the increasing antibiotic resistance of disease-causing microorganisms, probiotics have emerged as promising alternatives for disease control. Probiotics are live active microbes that are introduced into a target host in an adequate number or dose to promote its health. In the present paper, we first discuss the diseases that occur in M. rosenbergii production, followed by an in-depth discussion on probiotics. We elaborate on the common methods of probiotics administration and explain the beneficial health effects of probiotics as immunity enhancers. Moreover, we discuss the antagonistic effects of probiotics on pathogenic microorganisms. Altogether, this paper provides a comprehensive overview of disease control in M. rosenbergii aquaculture through the use of probiotics, which could enhance the sustainability of prawn culture.

Probiotic Supplementation as an Emerging Alternative to Chemical Therapeutics in Finfish Aquaculture: a Review

Aquaculture is a promising food sector to fulfil nutritional requirements of growing human population. Live weight aquaculture production reached up to 114.5 million tonnes in 2018 and it is further expected to grow by 32% by year 2030. Among total aquaculture production, major product harvested is finfish and its contribution has reached 46% in recent years. Frequent outbreaks of infectious diseases create obstacle in finfish production, result in economic losses to the farmers and threaten the sustainability of aquaculture industry itself. In spite of following the best management practices, the use of antibiotics, chemotherapeutics and phytochemicals often become the method of choice in finfish culture. Among these, phytochemicals have shown lesser effect in animal welfare while antibiotics and other chemotherapeutics have led to negative consequences like emergence of drug-resistant bacteria, and accumulation of residues in host and culture system, resulting in quality degradation of aqua products. Making use of probiotics as viable alternative has paved a way for sustainable aquaculture and minimise the use of antibiotics and other chemotherapeutics that pose adverse effect on host and culture system. This review paper elucidates the knowledge about antibiotics and other chemicals, compilation of probiotics and their effects on health status of finfish as well as overall culture environment. Besides, concoction of probiotics and prebiotics for simultaneous application has also been discussed briefly.

Histomorphological Changes in Fish Gut in Response to Prebiotics and Probiotics Treatment to Improve Their Health Status: A Review

The gastrointestinal tract (GIT) promotes the digestion and absorption of feeds, in addition to the excretion of waste products of digestion. In fish, the GIT is divided into four regions, the headgut, foregut, midgut, and hindgut, to which glands and lymphoid tissues are associated to release digestive enzymes and molecules involved in the immune response and control of host-pathogens. The GIT is inhabited by different species of resident microorganisms, the microbiota, which have co-evolved with the host in a symbiotic relationship and are responsible for metabolic benefits and counteracting pathogen infection. There is a strict connection between a fish's gut microbiota and its health status. This review focuses on the modulation of fish microbiota by feed additives based on prebiotics and probiotics as a feasible strategy to improve fish health status and gut efficiency, mitigate emerging diseases, and maximize rearing and growth performance. Furthermore, the use of histological assays as a valid tool for fish welfare assessment is also discussed, and insights on nutrient absorptive capacity and responsiveness to pathogens in fish by gut morphological endpoints are provided. Overall, the literature reviewed emphasizes the complex interactions between microorganisms and host fish, shedding light on the beneficial use of prebiotics and probiotics in the aquaculture sector, with the potential to provide directions for future research.

Evaluation of dietary single probiotic isolates and probiotic multistrain consortia in growth performance, gut histology, gut microbiota, immune regulation, and infection resistance of Nile tilapia, Oreochromis niloticus, shows superior monostrain performance

The probiotic potential of a designed bacterial consortia isolated from a competitive exclusion culture originally obtained from the intestinal contents of tilapia juveniles were evaluated on Nile tilapia alevins. The growth performance, intestinal histology, microbiota effects, resistance to Streptococcus agalactiae challenge, and immune response were assessed. In addition, the following treatments were included in a commercial feed: A12+M4+M10 (Lactococcus lactis A12, Priestia megaterium M4, and Priestia sp. M10), M4+M10 (P. megaterium M4, and Priestia sp. M10) and the single bacteria as controls; A12 (L. lactis A12), M4 (P. megaterium M4), M10 (Priestia sp. M10), also a commercial feed without any probiotic addition was included as a control. The results showed that all probiotic treatments improved the growth performance, intestinal histology, and resistance during experimental infection with S. agalactiae in comparison to the control fish. Also, the administration of probiotics resulted in the modulation of genes associated with the innate and adaptive immune systems that were non-dependent on microbial colonization. Surprisingly, L. lactis A12 alone induced benefits in fish compared to the microbial consortia, showing the highest increase in growth rate, survival during experimental infection with S. agalactiae, increased intestinal fold length, and the number of differentially expressed genes. Lastly, we conclude that a competitive exclusion culture is a reliable source of probiotics, and monostrain L. lactis A12 has comparable or even greater probiotic potential than the bacterial consortia.

Evaluation of fermented soybean meal by Bacillus subtilis as an alternative to fishmeal on the growth, and physiological status of Nile tilapia Oreochromis niloticus fingerlings

A feeding trial was conducted to investigate the effect of fermented soybean meal with Bacillus subtilis bacteria on growth performance, feed utilization, carcass composition, and hematological, and histological section of the liver and intestine of Nile tilapia Oreochromis niloticus fingerlings. Commercial soybean meal (SBM) containing 44% Crude Protein (CP) was fermented using the solid-state fermentation method which depended on autoclaving of SBM, then bacterial treatment injection by Bacillus subtilis, and finally incubation at 40C for 72 h then autoclaved to stop the growth of bacteria. Five isonitrogenous (25% crude protein) and isocaloric (4.4 kcal\g gross energy) experimental fish meal-free diets were formulated to compare with a common control diet containing fishmeal and unfermented soybean meal. Diets without fish meal contain fermented soybean meal (FSM) as a sole protein, FSM with corn gluten (CG), FSM with free amino acid methionine (Meth), FSM with corn gluten and methionine, and unfermented soybean meal. Eighteen glass aquaria, 80-L net volume, were used to stock 10 fingerlings (10.0 ± 0.1 g/fish) in each aquarium in the replicates group. The feed amount was given three times daily, six days a week throughout the 98 days experimental period. Fish were weighed biweekly and feed amounts were adjusted based on the new fish weight. Bacterial fermentation enhanced the protein content of commercial soybean meals by 6%. The crude protein of fermented soybean meal increased from 43.44% to 50.67%. Used of FSM as a sole dietary protein source resulted in a decrease in growth rate and feed utilization. However, the incorporation of FSM with corn gluten, and/or methionine amino acid led to an improvement in the performance of fish. Finally, the best final body weight, weight gain, specific growth rate, protein efficiency ratio, and protein productive value were recorded by a fish-fed mixed plant protein diet (FSM + CG + Meth). Also, Hematocrit and red blood cells were not significantly affected including the FSM.

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 Bacillus spp. Mixture on Growth, Immune Responses, Expression of Immune-Related Genes, and Resistance of Nile Tilapia Against Streptococcus agalactiae Infection

The purpose of this study was to evaluate the effect of Bacillus spp. mixture (Bacillus subtilis TISTR001, Bacillus megaterium TISTR067, and Bacillus licheniformis DF001) (1 × 10⁶ CFU/g) on growth, immune parameters, immune-related gene expression, and resistance of Nile tilapia against Streptococcus agalactiae AAHM04. Fish were fed different concentrations of Bacillus spp. 0 (control; T1), 1 (T2), 3 (T3), and 5 (T4) g/kg diets for 120 days. The results showed that weight gain, average daily gain, specific growth rate, feed conversion ratio in T3 diet were significantly higher than the control group and other tested diets (p < 0.05). Immune parameters, such as myeloperoxidase and lysozyme, were significantly higher in the T3 and T4 diets compared to the control group (p < 0.05). Similarly, IL-1β and TNF-α gene expressions in the spleen of fish fed T2, T3, and T4 diets were significantly higher than the control group (p < 0.05). However, no significant differences in survival rate, hematology, blood chemical indices, malondialdehyde (MDA) levels, body chemical composition, and organosomatic indices (p > 0.05) were noticed in all treatments. No significant differences in survival rate after the challenge test with S. agalactiae AAHM04 were found in fish fed Bacillus spp. mixture diets, except for the T3 diet. These results suggest that Bacillus spp. mixture diet at 3 g/kg diet (T3) could improve growth, immune response, and disease resistance of Nile tilapia.

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.

Growth performance, feed utilization, hematological parameters, and histological features of Nile tilapia (Oreochromis niloticus) fed diets with supplementary herbal extracts under prolonged water exchange

Nile tilapia is known for its relative tolerance to some biotic and abiotic stressors. However, long-period water exchange may impair the health status and, thereby, the growth performance and feed utilization. In this regard, using herbal extracts may help to relieve the adverse impacts of low water quality on the productivity of this fish species. A 100-day feeding trial was designed to examine the effects of dietary supplements of Aloe vera leaves (AVE), and chamomile flowers, Matricaria chamomilla (CFE) extracts on water quality, growth performance, and well-being of Nile tilapia. Fish (3.95±0.05 g, n=1200) were distributed into five groups (15 fiberglass tanks, 2 m3) under a water exchange rate of 20% every two days for standard control (T0) without herbal supplements. In groups (T1, T2, T3, and T4), a long period water exchange period of 50% every month, wherein T1 (stressed control), T2, T3, and T4 groups were fed a diet supplemented with 0% herbal extract, 1% AVE, 1% CFE and 0.5% AVE +0.5% CFE, respectively. Results showed that feeding on a T2 diet exhibited a clear improvement under a long period of water exchange stress, and it is almost similar to their counterparts under normal conditions (T0) in terms of specific growth rate, survival rate, feed intake, feed conversion ratio, and protein efficiency ratio. Moreover, the lowest levels of aspartate aminotransferase were obtained with T2 and T0. In addition, the highest white blood cell count and hemoglobin values were recorded with group T0, followed by T2, and T4, while no significant difference between T3 and T1. Fish under stressed conditions without herbal extracts (T1) showed the lowest performance and survival rate compared to T0 and T2 groups. In conclusion, feeding diet supplied with 1% A. vera extract to stressed fish restored their performance and well-being to the level of their counterparts under normal conditions.

Immunomodulatory effects of bacteriocinogenic and non-bacteriocinogenic Lactococcus cremoris of aquatic origin on rainbow trout (Oncorhynchus mykiss, Walbaum)

Lactic Acid Bacteria (LAB) are a group of bacteria frequently proposed as probiotics in aquaculture, as their administration has shown to confer positive effects on the growth, survival rate to pathogens and immunological status of the fish. In this respect, the production of antimicrobial peptides (referred to as bacteriocins) by LAB is a common trait thoroughly documented, being regarded as a key probiotic antimicrobial strategy. Although some studies have pointed to the direct immunomodulatory effects of these bacteriocins in mammals, this has been largely unexplored in fish. To this aim, in the current study, we have investigated the immunomodulatory effects of bacteriocins, by comparing the effects of a wild type nisin Z-expressing Lactococcus cremoris strain of aquatic origin to those exerted by a non-bacteriocinogenic isogenic mutant and a recombinant nisin Z, garvicin A and Q-producer multi-bacteriocinogenic strain. The transcriptional response elicited by the different strains in the rainbow trout intestinal epithelial cell line (RTgutGC) and in splenic leukocytes showed significant differences. Yet the adherence capacity to RTgutGC was similar for all strains. In splenocyte cultures, we also determined the effects of the different strains on the proliferation and survival of IgM⁺ B cells. Finally, while the different LAB elicited respiratory burst activity similarly, the bacteriocinogenic strains showed an increased ability to induce the production of nitric oxide (NO). The results obtained reveal a superior capacity of the bacteriocinogenic strains to modulate different immune functions, pointing to a direct immunomodulatory role of the bacteriocins, mainly nisin Z.

Single and Multi-Strain Probiotics Supplementation in Commercially Prominent Finfish Aquaculture: Review of the Current Knowledge

The Nile tilapia Oreochromis niloticus, Atlantic salmon Salmo salar, rainbow trout Oncorhynchus mykiss, olive flounder Paralichthys olivaceus, common carp Cyprinus carpio, grass carp Ctenopharyngodon idella and rohu carp Labeo rohita are farmed commercially worldwide. Production of these important finfishes is rapidly expanding, and intensive culture practices can lead to stress in fish, often reducing resistance to infectious diseases. Antibiotics and other drugs are routinely used for the treatment of diseases and sometimes applied preventatively to combat microbial pathogens. This strategy is responsible for the emergence and spread of antimicrobial resistance, mass killing of environmental/beneficial bacteria, and residual effects in humans. As an alternative, the administration of probiotics has gained acceptance for disease control in aquaculture. Probiotics have been found to improve growth, feed utilization, immunological status, disease resistance, and to promote transcriptomic profiles and internal microbial balance of host organisms. The present review discusses the effects of single and multi-strain probiotics on growth, immunity, heamato-biochemical parameters, and disease resistance of the above-mentioned finfishes. The application and outcome of probiotics in the field or open pond system, gaps in existing knowledge, and issues worthy of further research are also highlighted.

Probiotics, prebiotics and synbiotics improved the functionality of aquafeed: Upgrading growth, reproduction, immunity and disease resistance in fish

Aquaculture plays an increasingly significant role in improving the sustainability of global fish production. This sector has been intensified with the advent of new husbandry practices and the development of new technology. However, the increasing intensification and indiscriminate commercialized farming has enhanced the vulnerability of cultivated aquatic species to damage from pathogens. In efforts to confront these various diseases, frequent use of drugs, antibiotics, chemotherapeutics, and agents for sterilization have unintentionally added to the risk of transmission of pathogens and harmful chemical compounds to consumers. Some natural dietary supplements are believed to have the potential to offset this setback in aquaculture. Application of bio-friendly feed additives such as probiotics, prebiotics and synbiotics are becoming popular dietary supplements with the potential to not only improve growth performance, but in some cases can also enhance immune competence and the overall well-being of fish and crustaceans. The present review discusses and summarizes the effects of probiotics, prebiotics and synbiotics application on growth, stress mitigation, microbial composition of intestine, immune system and health condition of aquatic animals in association with existing constraints and future perspectives in aquaculture.

Dietary chitosan promotes the growth, biochemical composition, gut microbiota, hematological parameters and internal organ morphology of juvenile Barbonymus gonionotus

In this study, we determined the effects of dietary chitosan on the growth, biochemical composition, gut microbiota, and hematological and histological parameters of juvenile Barbonymus gonionotus. Three test diets containing three different concentrations (1, 2, and 3 g kg-1 feed) of dietary chitosan were formulated. A basal diet without dietary chitosan was considered a control, and the fish were reared for 60 days. Comparing the effects of the dietary chitosan-containing diets with those of the control diet, we found that dietary chitosan significantly improved the muscle growth, nutrient and mineral contents, hematological parameters, lactic acid bacterium abundance, and digestive enzyme activities of B. gonionotus. Moreover, dietary chitosan significantly inhibited the growth of pathogenic bacteria in fish. Interestingly, an increase in the dietary chitosan level significantly enhanced the protein contents of the muscles and inversely significantly decreased the lipid contents compared to those with the basal diet. Quantitative study revealed that dietary chitosan significantly enhanced the length of intestinal villi, and qualitative study showed that dietary chitosan considerably reduced the fat content in the liver and improved the morphology of the kidney compared to those with the basal diet. Taken together, our results suggest that the application of dietary chitosan at a dose of 1 g kg-1 feed produced the highest benefit to treated B. gonionotus, indicating its potential for safe use in aquaculture.

Probiotics-Live Biotherapeutics: a Story of Success, Limitations, and Future Prospects-Not Only for Humans

In livestock production, lactic acid bacteria (LAB) represent the most widespread microorganisms used as probiotics. For such critical use, these bacteria must be correctly identified and characterized to ensure their safety and efficiency. Recently, probiotics have become highly recognized as supplements for humans and in particular for animals because of their beneficial outcome on health improvement and well-being maintenance. Various factors, encompassing dietary and management constraints, have been demonstrated to tremendously influence the structure, composition, and activities of gut microbial communities in farm animals. Previous investigations reported the potential of probiotics in animal diets and nutrition. But a high rate of inconsistency in the efficiency of probiotics has been reported. This may be due, in a major part, to the dynamics of the gastrointestinal microbial communities. Under stressing surroundings, the direct-fed microbials may play a key role as the salient limiting factor of the severity of the dysbiosis caused by disruption of the normal intestinal balance. Probiotics are live microorganisms, which confer health benefits on the host by positively modifying the intestinal microflora. Thus, the aim of this review is to summarize and to highlight the positive influence of probiotics and potential probiotic microbe supplementation in animal feed with mention of several limitations.

Gut probiotic bacteria of Barbonymus gonionotus improve growth, hematological parameters and reproductive performances of the host

This study aimed to isolate and identify probiotic bacteria from the gut of Barbonymus gonionotus and evaluate their effects on growth, hematological parameters, and breeding performances of the host. Five probiotic bacteria viz. Enterococcus xiangfangensis (GFB-1), Pseudomonas stutzeri (GFB-2), Bacillus subtilis (GFB-3), Citrobacter freundii (GFB-4), and P. aeruginosa (GFB-5) were isolated and identified using 16S rRNA gene sequencing. Application of a consortium of probiotic strains (1-3 × 1.35 × 109 CFU kg-1) or individual strain such as GFB-1 (1.62 × 109 CFU kg-1), GFB-2 (1.43 × 109 CFU kg-1), GFB-3 (1.06 × 109 CFU kg-1), GFB-4 (1.5 × 109 CFU kg-1) or GFB-5 (1.43 × 109 CFU kg-1feed) through feed significantly improved growth, histological and hematological parameters and reproductive performances of B. gonionotus compared to untreated control. Moreover, the application of these probiotics significantly increased gut lactic acid bacteria and activities of digestive enzymes but did not show any antibiotic resistance nor any cytotoxicity in vitro. The highest beneficial effects on treated fishes were recorded by the application of GFB-1, GFB-2, GFB-3, and a consortium of these bacteria (T2). This is the first report of the improvement of growth and health of B. gonionotus fishes by its gut bacteria.

Scope of Archaea in Fish Feed: a New Chapter in Aquafeed Probiotics?

The outbreak of diseases leading to substantial loss is a major bottleneck in aquaculture. Over the last decades, the concept of using feed probiotics was more in focus to address the growth and health of cultivable aquatic organisms. The objective of this review is to provide an overview of the distinct functionality of archaea from conventional probiotics in nutrient utilization, specific caloric contribution, evading immune response and processing thermal resistance. The prime limitation of conventional probiotics is the viability of desired microbes under harsh feed processing conditions. To overcome the constraints of commercial probiotics pertaining to incompatibility towards industrial processing procedure, a super microbe, archaea, appears to be a potential alternative approach in aquaculture. The peculiarity of the archaeal cell wall provides them with heat stability and rigidity under industrial processing conditions. Besides, archaea being one of the gut microbial communities participates in various health-oriented biological functions in animals. Thus, the current review devoted that administration of archaea in aquafeed could be a promising strategy in aquaculture. Archaea may be used as a potential probiotic with the possible modes of functions and advantages over conventional probiotics in aquafeed preparation. The present review also provides the challenges associated with the use of archaea for aquaculture and a brief outline of the patents on archaea to highlight the various use of archaea in different sectors.

Illicium verum extracts and probiotics with added glucose oxidase promote antioxidant capacity through upregulating hepatic and jejunal Nrf2/Keap1 of weaned piglets

Accumulating evidences indicate that plant extracts and probiotics are effective antioxidant substitutes which play important roles in animal production. However, the comparative study of the mechanism underlying the antioxidant property of Illicium verum extracts (IVE) and probiotics with added glucose oxidase (PGO) on piglets remains to be explored. This study evaluated the difference and the interaction effect of IVE and PGO on serum, liver, and jejunum antioxidant capacity of weaned piglets. A total of 32 weaned piglets (Duroc × Landrace × Yorkshire) at the age of 28 d with an average body weight of 14.96 ± 0.32 kg were randomly divided into four treatments with eight replicates per treatment in a 2 × 2 factorial arrangement. Treatments included basal diet (IVE-PGO-), basal diet + 1,000 mg/kg PGO (IVE-PGO+), basal diet + 500 mg/kg IVE (IVE+PGO-), and basal diet + 500 mg/kg IVE + 1,000 mg/kg PGO (IVE+PGO+). All the piglets were housed individually for the 42-d trial period after 7-d adaptation. The piglets were euthanized at the end of the experiment and the liver and jejunum samples were taken and subjected to immunohistochemistry, Western blotting, as well as antioxidant and qRT-PCR analysis. Significant interactions were observed between IVE and PGO for total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-Px) in serum (42 d), liver, and jejunum; malondialdehyde (MDA) in serum (21 d); and mRNA and protein expression of kelch sample related protein-1 (Keap1) and nuclear factor erythroid-2 related factor (Nrf2)/Keap1 in the liver and jejunum (P < 0.05). Both IVE and PGO improved (P < 0.05) T-SOD and GSH-Px in the serum (42 d), liver, and jejunum, and the mRNA and protein expression of Nrf2 and Nrf2/Keap1 in the liver and jejunum, but decreased (P < 0.05) MDA in the serum (21 d) and the mRNA and protein expression of Keap1 in the liver and jejunum. Immunohistochemical results confirmed that IVE and PGO enhanced the positive reactions of Nrf2 but weakened Keap1 in both the liver and jejunum. In conclusion, the results confirmed that IVE (500 mg/kg) and PGO (1,000 mg/kg) can improve the antioxidant capacity of weaned piglets and that the interaction effect between IVE and PGO is significant. At the same time, the fact that IVE and PGO activate the Nrf2/Keap1 in the liver and jejunum signaling pathway suggests that they play an important role in the ameliorative antioxidant capacity of weaned piglets. Therefore, the combination of IVE and PGO could be recommended as a new potential alternative to antibiotics in piglets' diets.

Effects of probiotics Lactobacillus plantarum 16 and Paenibacillus polymyxa 10 on intestinal barrier function, antioxidative capacity, apoptosis, immune response, and biochemical parameters in broilers

This study aimed to investigate the effects of Lactobacillus plantarum 16 (Lac16) and Paenibacillus polymyxa 10 (BSC10) on intestinal barrier function, antioxidative capacity, apoptosis, immune response, and biochemical parameters in broilers. A total of 540 one-day-old broiler chicks (Cobb500) were randomly allocated to three groups of 180 birds, and fed either a basal diet or a basal diet supplemented with 108 colony-forming units Lac16 or BSC10 per kilogram feed for 21 D. The results revealed that both Lac16 and BSC10 maintained ileal mucosal morphology, and BSC10 regulated the expression of barrier function-related genes. Birds fed with probiotics decreased malondialdehyde level in jejunal mucosa and serum, and the increased activities of hepatic GSH-Px and jejunal CAT were observed in BSC10 group (P < 0.05). Immunohistochemistry of Bax, Bcl-2 and proliferating cell nuclear antigen and TUNEL-immunofluorescence assay demonstrated that Lac16 and BSC10 exerted beneficial effects on cell apoptosis and proliferation, as indicated by the gene expression of down-regulated Bax and p53 as well as a significant upregulation of Bcl-2 (P < 0.05). In addition, Lac16 and BSC10 significantly increased NO production and iNOS activity in liver and jejunal mucosa, and gene expression of IFN-γ (P < 0.01), IL-6 (P < 0.05), and IL-10 (P < 0.05 and P < 0.01, respectively) in ileum mucosa, whereas markedly decreased the expression of Cox2 (P < 0.05). Furthermore, it was found that Lac16 and BSC10 significantly reduced levels of alkaline phosphatase (P < 0.05 and P < 0.01, respectively) and creatine kinase (P < 0.05). Moreover, BSC10 significantly reduced uric acid (P < 0.05) and low-density lipoprotein levels (P < 0.01). Taken together, Lac16 and BSC10 could improve intestinal and body health status of broilers by increasing intestinal barrier function, anti-oxidative capacity and immunity, and decreasing cell apoptosis with strain-specificity.

Evaluation of commercial application of dietary encapsulated probiotic (Geotrichum candidum QAUGC01): Effect on growth and immunological indices of rohu (Labeo rohita, Hamilton 1822) in semi-intensive culture system

Encapsulated probiotic administration can be a nutritional strategy to improve the growth performance and immune status of fish. Here commercial application of encapsulated G. candidum was evaluated as a feed supplement to fingerlings of L. rohita reared in earthen ponds under semi-intensive culture conditions. Fingerlings with an average body weight of 20 ± 2.34 g were distributed randomly in three groups and experiment was conducted in triplicate. The control group (P0) was fed 35% protein basal diet while the two treated groups, P1 and P2 were fed basal diet supplemented with 10⁹ CFU g^-1 un-encapsulated (free) and encapsulated G. candidum, respectively, for eleven weeks. Results indicated significantly (P < 0.05) improved growth rate, intestinal enzyme activities (protease, amylase and cellulase) and hemato-immunological indices (RBCs, Hb, HCT, WBCs, MCHC, respiratory bursts and phagocytic activity, total protein, lysozyme, IgM), upregulation of heat shock protein HSP 70 gene in muscle, intestine and liver tissues and reduction of serum AST and ALT activities, total cholesterol and triglyceride in fish fed G. candidum supplemented diets (P1 and P2 groups) as compared to basal diet (P0 group). However, diet supplemented with encapsulated G. candidum showed the most significant (p < 0.001) positive effect in comparison to un-encapsulated probiotic. In conclusion, a pronounced effect of G. candidum especially in the encapsulated form on the growth, health status and immunity of L. rohita reared in semi intensive culture system, suggesting its application as a feed additive in practical/commercial semi-intensive earthen pond culture system.

Dietary administration of probiotics modulates non-specific immunity and gut microbiota of Nile tilapia (Oreochromis niloticus) cultured in low input ponds

Poor culture conditions in low input ponds make fish highly susceptible to infectious pathogens which lead to diseases and mortalities yet the effects of probiotics on immunity, gut microbiota and microbiological quality of fish in low input ponds are unknown. Nile tilapia, Oreochromis niloticus fingerlings (40 g) were randomly stocked at 50 fish m⁻³ in 1.25 m³ cages in low input ponds. The fish were fed on diets supplemented with either Saccharomyces cerevisiae (1 × 10¹⁰ CFU g⁻¹) or Bacillus subtilis (1 × 10⁹ CFU g⁻¹) at six levels: Diet 0 (No probiotic); S. cerevisiae at 2 g kg⁻¹ (Diet 1); 4 g kg⁻¹ (Diet 2) and 6 g kg⁻¹ (Diet 3) and B. subtilis at 5 g kg⁻¹ (Diet 4); 10 g kg⁻¹ (Diet 5) and 15 g kg⁻¹ (Diet 6) for 180 days. Results indicate that hemato-immunological parameters (hemoglobin (Hb), red blood cells (RBC), white blood cells (WBC) serum protein, albumin, globulin and lysozyme activity) were significantly higher in fish fed on probiotic treated diets compared to the control (P < 0.05). On the contrary, fish fed on Diet 6 presented significantly similar Hb and globulin values compared to the control (P > 0.05). Additionally, fish fed on probiotic treated diets retained the probiotics in their guts and lower microbial load was realized in their muscle (P < 0.05). In conclusion, B. subtilis and S. cerevisiae supplementation in diets of Nile tilapia reared in low input ponds improves immunity, manipulates gut microbiota and enhances fish flesh quality.

Effect of Bacillus cereus against cadmium induced hematological disturbances and immunosuppression in Carassius auratus gibelio

Cadmium (Cd) is the most common heavy metal and is easily detected in aquatic environments worldwide. The genus Bacillus was one of dominant probiotics, which was commonly used in aquaculture. The present study was undertaken to explore the effects of Bacillus cereus (B. cereus) supplementation on hematological parameters and the immune response of Carassius auratus gibelio (C. gibelio) following Cd exposure. Fish were exposed to waterborne Cd (0, 1 and 2 mg/L) and/or treated with dietary B. cereus at 10⁸ cfu/g for four weeks. The hematological disturbances observed after exposure of waterborne Cd included significant decreases in red blood cell (RBC) count, hemoglobin (Hb) concentration and hematocrit (HCT). While significant elevation (P < 0.05) of RBC count, HCT and Hb levels in the 1 and 2 mg/L Cd-B. cereus administration group at 4 weeks, compared with the Cd-only group. Among serum enzymatic activities, aspartate aminotransferase (AST) and alanine transaminase (ALT) activities by Cd exposure were significantly higher than controls, but this increase was effectively inhibited in Cd-B. cereus administration groups. In the Cd-B. cereus administration group, significant down-regulation of Hsp70, Hsp90, IL-1β, IL-6, IL-10 and TNF-α in conjunction with the up-regulation of IgM and LZM in the spleen indicated that B. cereus alleviated the Cd-induced damage to the immune system to some degree. The results of this study suggested that B. cereus has the potential to countermeasure Cd-induced hematological disturbances and immunosuppression in C. gibelio.

Immunomodulatory and ameliorative effects of Lactobacillus and Saccharomyces based probiotics on pathological effects of eimeriasis in broilers

Eimeria infection is very important in broilers and causes heavy economic losses in extensive farming system due to reduced weight gains, high mortality and poor feed conversion ratio (FCR). Under the circumstances, there is a dire need to devise effective control strategies to avoid/counteract this infectious threat. This study was conducted to assess the immunomodulatory and ameliorative effects of Lactobacillus and Saccharomyces based probiotics against Eimeria infection in broilers. The results showed statistically higher (P < 0.05) lymphoproliferative responses in experimental groups treated either with Lactobacillus or Saccharomyces based probiotics, as compared to control group. Further higher antibody titers (geomean titers) were also recorded in chickens of experimental groups treated with probiotics as compared to those of control group. The probiotic treated groups also revealed significantly improved (P < 0.05) FCRs as compared to control group. In challenge experiment, significantly lower (P < 0.05) oocyst counts were recorded in broilers treated with probiotics, when compared with control group. Further, experimental groups also revealed significantly higher (P < 0.05) daily weight gains and protection rates as compared to control. The data regarding the lesion scoring showed that chickens treated with probiotics had higher values of percent protection against intestinal and caecal lesion, when compared with those of control group. In conclusion, supplementation of probiotics proved very useful to enhance the immunological and performance potentials of broilers which subsequently provided protection against Eimeria infection. Further studies on the physico-chemical properties along with commercial feasibility and cost benefit analysis of these probiotic species are needed for wise selection to get maximum profit from broiler industry.

Therapeutic Effect of Intestinal Autochthonous Lactobacillus reuteri P16 Against Waterborne Lead Toxicity in Cyprinus carpio

Harmful effects of heavy metals are myriad. Lead (Pb) from soil and atmosphere contaminates water bodies and affects the aquatic animals. Our previous study confirmed the in vitro probiotic potential of Lactobacillus reuteri against Pb toxicity, but further investigation is necessary for gaining insights into the related protection mode. Therefore, in this study, we investigated the protective effects of the potential probiotic L. reuteri P16 against waterborne Pb exposure-induced toxicity in the freshwater fish Cyprinus carpio. Fish (average weight: 23.16 ± 0.73 g) were allocated to four groups (control, Pb only, Pb + L. reuteri P16, and L. reuteri P16 only) and Pb groups were exposed to waterborne Pb (1 mg L⁻¹) for 6 weeks. L. reuteri P16 (10⁸ CFU g⁻¹) supplemented diet was provided twice daily. Growth performances, hemato-biochemical parameters, innate immune responses, intestinal microbiota, and Pb accumulation in tissues were measured at the end of the trial. When the fish were exposed to Pb, dietary supplementation of L. reuteri P16 effectively decreased mortality and accumulation of Pb in tissues, and improved the growth performance. Co-treatment with Pb and L. reuteri P16 alleviated Pb exposure-induced oxidative stress, reversed alterations in hemato-biochemical parameters, improved innate immune parameters, and restored intestinal enzymatic activities. Moreover, L. reuteri P16 supplementation reversed the changes in intestinal microbiota in Pb-exposed fish. Furthermore, Pb exposure decreased the expressions of pro-inflammatory cytokines (TNF-α, IL-1β). However, the expression of heat shock proteins (HSP70 and HSP90) increased, which might have increased the cellular stress. Interestingly, the Pb-induced alterations of gene expressions were reversed by L. reuteri P16 supplementation. Thus, dietary administration of the potential probiotic L. reuteri P16 had several beneficial effects on growth performance and immune responses, decreased Pb accumulation in tissues, and reversed alterations in hematological responses of C. carpio. Furthermore, it offered direct protection against Pb-induced oxidative stress. Therefore, L. reuteri P16 may be a novel dietary supplement for enhancing growth performance and preventing Pb-exposure-induced toxicity in fish in aquaculture and aquatic products.

Apoptosis in fish: environmental factors and programmed cell death

Apoptosis, a form of programmed cell death, is a critical component in maintaining homeostasis and growth in all tissues and plays a significant role in immunity and cytotoxicity. In contrast to necrosis or traumatic cell death, apoptosis is a well-controlled and vital process characterized mainly by cytoplasmic shrinkage, chromatin condensation, DNA fragmentation, membrane blebbing and apoptotic bodies. Our understanding of apoptosis is partly based on observations in invertebrates but mainly in mammals. Despite the great advantages of fish models in studying vertebrate development and diseases and the tremendous interest observed in recent years, reports on apoptosis in fish are still limited. Although apoptotic machinery is well conserved between aquatic and terrestrial organisms throughout the history of evolution, some differences exist in key components of apoptotic pathways. Core parts of apoptotic machinery in fish are virtually expressed as equivalent to the mammalian models. Some differences are, however, evident, such as the extrinsic and intrinsic pathways of apoptosis including lack of a C-terminal region in the Fas-associated protein with a death domain in fish. Aquatic species inhabit a complex and highly fluctuating environment, making these species good examples to reveal features of apoptosis that may not be easily investigated in mammals. Therefore, in order to gain a wider view on programmed cell death in fish, interactions between the main environmental factors, chemicals and apoptosis are discussed in this review. It is indicated that apoptosis can be induced in fish by exposure to environmental stressors during different stages of the fish life cycle.

Autochthonous Bacterial Isolates Successfully Stimulate In vitro Peripheral Blood Leukocytes of the European Sea Bass (Dicentrarchus labrax)

Commercially available probiotics are routinely administered as feed supplements in aquaculture important species. Among them, the European sea bass (Dicentrarchus labrax) is the most widely reared fish in the Mediterranean, whose rearing systems are highly variable between countries, affecting at some level the sustainability of production. After random isolation of autochthonous gut bacteria of the sea bass, their identification and pathogenicity testing, we have selected three potentially probiotic isolates; Pseudoalteromonas sp., Alteromonas sp., and Enterovibrio coralii. Selected isolates were tested and their immunostimulative efficiency was compared with a commercially available Lactobacillus casei isolate, inferring inflammatory, apoptotic and anti-pathogen response of sea bass’ peripheral blood leukocytes. Phagocytic activity, respiratory burst, and expression of lysozyme, Mx protein, caspase 3, TNF-α, IL-10 genes was measured 1, 3, 5, and 12 h post-stimulation by four bacterial isolates to evaluate early kinetics of the responses. Best immunostimulative properties were observed in Pseudoalteromonas-stimulated leukocytes, followed by Alteromonas sp. and L. casei, while Enterovibrio coralii failed to induce significant stimulation. Based on such in vitro assay intestinal autochthonous bacterial isolates showed to have better immunostimulative effect in sea bass compared to aquaculture-widely used L. casei, and further steps need to engage tank and field feeding trials to evaluate long-term prophylactic suitability of the chosen isolates. A panel of biomarkers that represent pro-/anti-inflammatory, pro-/anti-apoptotic, and anti-bacteria/viral responses of the fish should be taken into consideration when evaluating the usefulness of the potential probiotic in aquaculture.

Modulation of immunity and gut microbiota after dietary administration of alginate encapsulated Shewanella putrefaciens Pdp11 to gilthead seabream (Sparus aurata L.)

The potential benefits of probiotics when administering to fish could improve aquaculture production. The objective of this study was to examine the modulation of immune status and gut microbiota of gilthead seabream (Sparus aurata L.) specimens by a probiotic when administered encapsulated. Commercial diet was enriched with Shewanella putrefaciens Pdp11 (SpPdp11, at a concentration of 10(8) cfu g(-1)) before being encapsulated in calcium alginate beads. Fish were fed non-supplemented (control) or supplemented diet for 4 weeks. After 1, 2 and 4 weeks the main humoral and cellular immune parameters were determined. Furthermore, gene expression profile of five immune relevant genes (il1β, bd, mhcIIα, ighm and tcrβ) was studied by qPCR in head kidney. On the other hand, intestinal microbiota of fish was analysed at 7 and 30 days by DGGE. Results demonstrated that administration of alginate encapsulated SpPdp11 has immunostimulant properties on humoral parameters (IgM level and serum peroxidase activity). Although no immunostimulant effects were detected on leucocyte activities, significant increases were detected in the level of mRNA of head-kidney leucocytes for mhcIIα and tcrβ after 4 weeks of feeding the encapsulated-probiotic diet. The administration of SpPdp11 encapsulated in alginate beads produced important changes in the DGGE patterns corresponding to the intestinal microbiota. Predominant bands related to lactic acid bacteria, such as Lactococcus and Lactobacillus strains, were sequenced from the DGGE patterns of fish fed the probiotic diet, whereas they were not sequenced from fish receiving the control diet. The convenience or not of probiotic encapsulation is discussed.

Prospects of host-associated microorganisms in fish and penaeids as probiotics with immunomodulatory functions

Aquatic animals harbor a great number of microorganisms with interesting biological and biochemical diversity. Besides serving as the natural defense system of the host, the utilization potential of this microbial association has been identified particularly as reservoirs of candidate probiotics. Host-derived probiotics have gained popularity in recent years as they offer an alternative source of beneficial microbes to the industry that is customarily dependent on the use of terrestrial microorganisms. At present, there is an overwhelming number of candidate probiotics in aquaculture but their large-scale application is restricted by bio-technological concerns and fragmentary documented probiotic actions. This paper presents the current understanding on the use of probiotics as a sustainable alternative that promotes health and welfare in fish and penaeids. In particular, this paper discusses the relevance of host microbiota and its potential as a source of candidate probiotics. It also revisits the interaction between probiotics and host immunity to provide the foundation of the immunomodulatory functions of host-derived probiotics. Several studies demonstrating the immunomodulatory capabilities of host-derived candidate probiotics are given to establish the current knowledge and provide avenues for future research and development in this thematic area of probiotics research in aquaculture.