Effects of Dietary Supplementation With Bacillus subtilis, as an Alternative to Antibiotics, on Growth Performance, Serum Immunity, and Intestinal Health in Broiler Chickens

Dietary Bacillus velezensis KNF-209 supplementation improves growth performance, enhances immunity, and promotes gut health in broilers

This study aimed to investigate the effects of dietary Bacillus velezensis KNF-209 (BV-KNF-209) on the growth performance, immunity, and gut health of broilers. A total of 540 one-day-old male Cobb-500 broilers were randomly divided into 5 groups of 6 replicates with 18 broilers per replicate. Dietary treatments were corn-soybean meal basal diets supplemented with 0, 50, 100, 200, and 400 mg/kg BV-KNF-209 (CON, BV 50, BV 100, BV 200, and BV 400 groups, respectively) for 42 d. Compared with the CON group, the average daily gains (ADG) at 0 to 42 d in the BV 100 and BV 200 groups were significantly increased (P < 0.01), and the feed-to-gain (F:G) ratios were significantly decreased at 0 to 21 d (P < 0.01) and 0 to 42 d (P < 0.05). The BV 200 and BV 400 groups had higher serum immunoglobulin M (IgM) levels at d 21 and 42 (P < 0.05). The serum levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) were significantly decreased in the BV 50, BV 100, and BV 200 groups at d 21 (P < 0.05), and serum IL-1β and IL-6 levels were also reduced in the BV 100 and BV 200 groups at d 42 (P < 0.05). Meanwhile, increased interleukin-10 (IL-10) levels in the jejunal and ileal mucosa at d 42 were observed in the BV 100, BV 200, and BV 400 groups (P < 0.05), while the IL-1β and IL-6 levels (P < 0.01) were decreased. The BV 200 and BV 400 groups showed significantly higher activities of lipase and trypsin (P < 0.05) in jejunal digesta as well as higher activities of amylase and trypsin (P < 0.01) in ileal digesta at d 42. The cecal acetic acid and propionic acid levels in the BV groups and lactic acid levels in the BV 50, BV 100, and BV 200 groups (P < 0.05) were significantly higher compared to those in the CON group. Overall, dietary BV-KNF-209 supplementation significantly improved broiler growth performance, an effect that may have been achieved by heightening immunity, increasing digestive enzyme activity, and raising intestinal short-chain fatty acids and lactic acid levels.

Postbiotic derived from Bacillus subtilis ACCC 11025 improves growth performance, mortality rate, immunity, and tibia health in broiler chicks

Introduction

The objective of this study was to evaluate the effects of dietary supplementation of postbiotics on growth performance, mortality rate, immunity, small intestinal health, tibia characteristics, and hematological parameters of broiler chicks. he postbiotics were derived from Bacillus subtilis ACCC 11025.

Methods

A total of 480 day-old Arbor acre broiler chicks (52.83 ± 1.38 g) were used in a 42-day study and were randomly allocated into four groups. Each group comprised 6 replicate cages, each containing 20 birds. Dietary treatments were based on a basal diet, supplemented with postbiotics at concentrations of 0.000%, 0.015%, 0.030%, or 0.045%.

Results and discussion

The results demonstrated an improvement in growth performance, antibody titers against avian influenza virus and Newcastle disease virus, serum albumin levels, and serum total protein levels, as well as a reduction in mortality rate among broiler chicks with increasing levels of postbiotic supplementation. The most significant effect were observed in the group receiving 0.015% postbiotics. Furthermore, a dose-dependent enhancement in tibia weight and tibia weight to length ratio, coupled with a reduction in the robusticity index, was noted. The most favorable outcomes for tibia health were observed in the group receiving 0.030% postbiotics. This improvement in tibia health corresponded to a linear increase in serum calcium and inorganic phosphorus contents. In summary, supplementing broiler chicks with 0.015% postbiotics effectively enhances immunity, leading to improved growth performance and reduced mortality rates. Additionally, a postbiotic dose of 0.030% is suitable for optimizing tibia health.

Important role of Bacillus subtilis as a probiotic and vaccine carrier in animal health maintenance

Bacillus subtilis is a widespread Gram-positive facultative aerobic bacterium that is recognized as generally safe. It has shown significant application value and great development potential in the animal farming industry. As a probiotic, it is frequently used as a feed growth supplement to effectively replace antibiotics due to its favourable effects on regulating the intestinal flora, improving intestinal immunity, inhibiting harmful microorganisms, and secreting bioactive substances. Consequently, the gut health and disease resistance of farmed animals can be improved. Both vegetative and spore forms of B. subtilis have also been utilized as vaccine carriers for delivering the antigens of infectious pathogens for over a decade. Notably, its spore form is regarded as one of the most prospective for displaying heterologous antigens with high activity and stability. Previously published reviews have predominantly focused on the development and applications of B. subtilis spore surface display techniques. However, this review aims to summarize recent studies highlighting the important role of B. subtilis as a probiotic and vaccine carrier in maintaining animal health. Specifically, we focus on the beneficial effects and underlying mechanisms of B. subtilis in enhancing disease resistance among farmed animals as well as its potential application as mucosal vaccine carriers. It is anticipated that B. subtilis will assume an even more prominent role in promoting animal health with in-depth research on its characteristics and genetic manipulation tools.

Lignocellulose and probiotic supplementation in broiler chicken diet: effect on growth performance, digestive health, litter quality, and genes expression

Three hundred one-day-old Avian 48 broiler chicks were used to investigate the effect of lignocellulose (LC) and probiotic supplementation in broiler chicken diet on growth performance, digestive health, litter quality, and some gene expression. Experimental treatments consisted of 3 × 2 factorial arrangements with 3 levels of LC without or with probiotics to formulate 6 experimental groups. Groups 1, 2, and 3 were fed on the basal diet with dietary LC inclusion at 0, 0.5, and 1.0%, respectively, while groups 4, 5, and 6 were fed on the previously mentioned design with Bacillus subtilis at 100 gm/ton. The results revealed that Dietary LC inclusion nonsignificantly (P ≥ 0.05) reduced body weight (BW), body weight gain (BWG), and feed intake. Meanwhile, B. subtilis supplementation improved BW and BWG and enhanced the effect of LC on the broilers' weight. The group fed a 0.5% LC and B. subtilis-supplemented diet recorded the best (P ≥ 0.05) BW, BWG, FCR, PER, EEU, and PI. LC and or B. subtilis supplementation improved carcass traits of broiler (higher dressing% with lower abdominal fat% compared with a control group), intestinal health, and absorptive capacity. LC potentiates the effect of B. subtilis supplementation in broilers' diet in modulating intestinal microflora (lowered (P ≥ 0.05) cecal Coliform and increased Lactobacillus counts), the highest Coliform counts were recorded in group fed 0.5 or 1.0% LC plus B. subtilis. LC at 0.5 or 1.0% and or B. subtilis supplementation reduced (P ≥ 0.05) litter moisture% at the 2nd, 4th, and 6th wk compared to the control group. Dietary inclusion of LC and or B. subtilis supplementation significantly (P < 0.001) up-regulated hepatic growth-related genes (growth hormone receptor (GHR) and insulin growth factor1 (IGF-1)) and antioxidant-related genes (superoxide dismutase 1 (SOD1), glutathione peroxidase (GPX1) and uncoupling protein (UCP) and down-regulated (P < 0.001) splenic toll-like receptor 4 (TLRP) gene expression while had no significant effect on splenic interleukin 8 (IL8) and tumor necrosis factor (TNF) with the best-obtained results with 1.0% followed by 0.5% LC with B. subtilis supplementation. We concluded that dietary LC and/or B. subtilis supplementation positively affected the growth performance, feed efficiency, carcass quality, intestinal absorptive capacity and health, litter quality and growth, and antioxidant and immune-related gene expression.

Effects of duo-strain probiotics on growth, digestion, and gut health in broiler chickens

The goal of this inquiry was to analyze the impact of incorporating Enterococcus faecium and Streptococcus thermophilus using a novel premix-spray method on the following aspects: growth rate, digestive enzyme activity, antioxidant levels, gut microbiome composition, and the morphological characteristics of the duodenum, jejunum, and ileum in broiler chickens. Furthermore, this study explored the potential benefits of duo strains of probiotics (DSP) in reducing flatulence, regulating stool microbial population, and improving diarrhea symptoms. A total of 360 one-day-old mixed-sex Plymouth Rock chicks (IW: 51 ± 33 g) were randomly divided into two treatment groups. Each treatment group was further divided into 9 replicated cages, with 20 chicks housed in each cage. The control group (CG) received a basal diet composed of a soy-corn mixture, whereas the experimental group was provided with DSP (CON + 0.5 % probiotic). The results showed that the increase in the body weight of broilers at the end of the fourth week in the control group and the treatment group was 1.576 versus 1.847 kg, respectively. Throughout the 30-day trial period, the DSP diet significantly improved the specific growth rate (SGR), survival rate (SR), and body weight gain (BWG) while decreasing the feed conversion ratio (FCR) (P < 0.05). The DSP diet also enhanced the Enzymatic digestion (protease, amylase, lipase, and trypsin) and antioxidant potential (SOD, MDA, and catalase) of the broilers compared to those in the CG. The results revealed significant enhancements in the tissue morphology of the duodenum and jejunum following the combined treatment for a duration of 4 weeks. The DSP treatments significantly increased microvillus height in the duodenum and jejunum but had no notable effects in the ileum. Incorporating 0.5 % DSP in poultry feed improved the relative abundance of Ruminococcaceae and Faecalibacteriumin, leading to better management of diarrhea and reduced presence of E. coli compared to the control diet. Additionally, including probiotics in the basal diet reduced H2S, CO2, NH3, and CH4 levels. Overall, the study suggests that the new spray-drying approach with these strains has potential for supplementing probiotics in poultry feed processing, and including DSP in broiler chicken diets has beneficial effects.

Diet xylo-oligosaccharide supplementation improves growth performance, immune function, and intestinal health of broilers

The effects of xylo-oligosaccharides (XOS) on broiler growth performance, immune function, and intestinal health were investigated. A total of 540 one-d-old Arbor Acres Plus broilers were randomly divided into 5 groups with 6 replicates per group and 18 chickens per replicate. Broilers in the control (CON) group received a corn-soybean meal based basal diet, those in the antibiotics (ANT) group received the basal diet plus 500 mg/kg oxytetracycline, and those in XOS groups received the basal diet plus 150, 300, or 450 mg/kg XOS. Compared with CON, the body weight at 42 d and average daily gain from 1 to 42 d were significantly increased in the 150, 450 mg/kg XOS-added and ANT groups (P = 0.018), and the relative expression of claudin-1 and ZO-1 mRNA in the ileum was significantly higher in the 300 and 450 mg/kg XOS-added groups (P < 0.001). The feed conversion ratios (P < 0.001) and abdominal fat rates (P = 0.012) of broilers from 1 to 42 d of age were significantly lower in all XOS-added groups than in the control group. Splenic index (P = 0.036) and bursa of Fabricius index (P = 0.009) were significantly better in the ANT group and each XOS-added group than in the control group. Compared to CON and ANT, serum IgA (P = 0.007) and IgG (P = 0.002) levels were significantly higher in the 300 mg/kg XOS-added group, and the relative abundance of short-chain fatty acid-producing genera (Alistipes) was also significantly higher (P < 0.001). Meanwhile, ileal villus height (P < 0.001) and ratio of villus height to crypt depth (V:C) (P = 0.001) were significantly increased in XOS-added broilers. In analysis of relationships between cecal microbes and the physical barrier of the gut, [Ruminococcus]_torques_group was positively correlated with mRNA expression of ileal ZO-1 and claudin-1 (P < 0.05), and Bacteroides was positively correlated with increased ileal villus height and V:C (P < 0.05). Overall, XOS addition to broiler diets improved growth performance, promoted intestinal health by enhancing intestinal barrier function and regulating cecal microbiota diversity, and had positive effects on immunity.

Systematic review on microbiome-related nutritional interventions interfering with the colonization of foodborne pathogens in broiler gut to prevent contamination of poultry meat

This systematic review aimed to compile the available body of knowledge about microbiome-related nutritional interventions contributing to improve the chicken health and having an impact on the reduction of colonization by foodborne pathogens in the gut. Original research articles published between 2012 and 2022 were systematically searched in Scopus and PubMed. A total of 1,948 articles were retrieved and 140 fulfilled the inclusion criteria. Overall, 73 papers described 99 interventions against colonization by Escherichia coli and related organisms; 10 papers described 15 interventions against Campylobacter spp.; 36 papers described 54 interventions against Salmonella; 40 papers described 54 interventions against Clostridium perfringens. A total of 197 microbiome-related interventions were identified as effective against one or more of the listed pathogens and included probiotics (n = 80), prebiotics (n = 23), phytobiotics (n = 25), synbiotics (n = 12), organic acids (n = 12), enzymes (n = 4), essential oils (n = 14) and combination of these (n = 27). The identified interventions were mostly administered in the feed (173/197) or through oral gavage (11/197), in the drinking water (7/197), in ovo (2/197), intra amniotic (2/197), in fresh or reused litter (1/197) or both in the feed and water (1/197). The interventions enhanced the beneficial microbial communities in the broiler gut as Lactic acid bacteria, mostly Lactobacillus spp., or modulated multiple microbial populations. The mechanisms promoting the fighting against colonization by foodborne pathogens included competitive exclusion, production of short chain fatty acids, decrease of gut pH, restoration of the microbiome after dysbiosis events, promotion of a more stable microbial ecology, expression of genes improving the integrity of intestinal mucosa, enhancing of mucin production and improvement of host immune response. All the studies extracted from the literature described in vivo trials but performed on a limited number of animals under experimental settings. Moreover, they detailed the effect of the intervention on the chicken gut without details on further impact on poultry meat safety.

Investigating antibiotic free feed additives for growth promotion in poultry: effects on performance and microbiota

The poultry industry is evolving towards antibiotic-free production to meet market demands and decelerate the increasing spread of the antimicrobial resistance. The growing need for antibiotic free products has challenged producers to decrease or completely stop using antimicrobials as feed supplements in broiler diet to improve feed efficiency, growth rate, and intestinal health. Natural feed additives (e.g., probiotics and phytobiotics) are promising alternatives to substitute antimicrobial growth promoters. The goal of our study was to characterize the effects of a Probiotic and an Essential Oils blend on broilers' performance and perform a time-series analysis to describe their excreta microbiome. A total of 320 Cobb 500 (1-day-old) chicks were raised for 21 d in 32 randomly allocated cages. Treatments consisted of 4 experimental diets: a basal diet, and a basal diet mixed with an Antibiotic (bacitracin methylene disalicylate), an essential oils blend (oregano oil, rosemary, and red pepper), or a Probiotic (Bacillus subtilis). Body weight (on 1, 10, and 21d), and feed intake (10d and 21d) were recorded and feed conversion ratio was calculated. Droppings were collected daily (1-21d) to characterize broilers' excreta microbiota by targeted sequencing of the bacterial 16S rRNA gene. The Probiotic significantly improved feed conversion ratio for starter phase 1 to 10d (P = 0.03), grower phase 10 to 21d (P = 0.05), and total period 1 to 21d (P = 0.01) compared to the Antibiotic. Feed supplements did not affect alpha diversity but did impact microbial beta diversity (P < 0.01). Age also impacted microbiome turnover as differences in alpha and beta diversity were detected. Furthermore, when compared to the basal diet, the probiotic and antibiotic significantly impacted relative abundance of Bifidobacterium (log2 fold change -1.44, P = 0.03), Intestinimonas (log2 fold change 0.560, P < 0.01) and Ligilactobacillus (log2 fold change -1.600, P < 0.01). Overall, Probiotic supplementation but not essential oils supplementation positively impacted broilers' growth performance by directly causing directional shifts in broilers' excreta microbiota structure.

Effects of dietary supplementation of postbiotic derived from Bacillus subtilis ACCC 11025 on growth performance, meat yield, meat quality, excreta bacteria, and excreta ammonia emission of broiler chicks

The primary aim of this study was to explore the impact of dietary supplementation with a postbiotic derived from Bacillus subtilis ACCC 11025 on growth performance, meat yield, meat quality, excreta bacterial populations, and excreta ammonia emissions of broiler chicks. A total of 480 day-old Arbor Acre broiler chicks, initially weighing 52.83 ± 1.38 g, were randomly allocated into 4 distinct groups. Each group was housed in 6 separate cages, each containing 20 birds. The experimental phase spanned 42 d, divided into 2 periods (d 1-21 and d 22-42). Dietary interventions were based on a basal diet, with postbiotic supplementation at levels of 0.000, 0.015, 0.030, or 0.045%. Our findings indicate that dietary supplementation with postbiotic had a positive influence on body weight gain (BWG) and feed efficiency. The most substantial improvements in BWG and feed efficiency were observed in the group of broiler chicks fed a diet containing 0.015% postbiotic. Furthermore, the inclusion of postbiotic in the diet led to an increase in the yield of breast and leg muscles, with a significant difference in meat yields observed between the control group and the group receiving 0.015% postbiotic supplementation. It's noteworthy that dietary manipulation did not exert any discernible impact on the quality of breast and leg muscle samples. Concurrently, we observed an elevation in serum albumin and total protein contents corresponding to the increasing postbiotic dosage in the diet. Additionally, dietary supplementation with postbiotic effectively controlled the emission of ammonia from excreta and reduced the abundance of Salmonella in excreta while enhancing the presence of Lactobacillus bacteria. The group receiving 0.015% postbiotic supplementation displayed the lowest levels of ammonia emission and the highest counts of Lactobacillus bacteria in excreta. In light of these results, we conclude that dietary supplementation with 0.015% postbiotic represents an efficacious strategy for increasing BWG and meat yield of broiler chicks by enhancing feed efficiency as well as mitigating ammonia emissions from excreta by modulating the composition of excreta bacterial communities.

Effects of Succinate on Growth Performance, Meat Quality and Lipid Synthesis in Bama Miniature Pigs

Succinate, one of the intermediates of the tricarboxylic acid cycle, is now recognized to play a role in a broad range of physiological and pathophysiological settings, but its role in adipogenesis is unclear. Our study used Bama miniature pigs as a model to explore the effects of succinate on performance, meat quality, and fat formation. The results showed that adding 1% succinate significantly increased the average daily gain, feed/gain ratio, eye muscle area, and body fat content (p < 0.05), but had no effect on feed intake. Further meat quality analysis showed that succinate increased the marbling score and intramuscular fat content of longissimus dorsi muscle (LM), while decreasing the shear force and the cross-sectional area of LM (p < 0.05). Metabolomics analysis of LM revealed that succinate reshaped levels of fatty acids, triglycerides, glycerophospholipids, and sphingolipids in LM. Succinate promotes adipogenic differentiation in porcine primary preadipocytes. Finally, dietary succinate supplementation increased succinylation modification rather than acetylation modification in the adipose tissue pool. This study elucidated the effects of succinate on the growth and meat quality of pigs and its mechanism of action and provided a reference for the role of succinate in the nutrition and metabolism of pigs.

Probiotic cocktails accelerate baicalin metabolism in the ileum to modulate intestinal health in broiler chickens

BACKGROUND

Baicalin and probiotic cocktails are promising feed additives with broad application prospects. While probiotic cocktails are known to enhance intestinal health, the potential synergistic impact of combining baicalin with probiotic cocktails on the gut health of broiler chickens remains largely unexplored. Therefore, this study aims to investigate the influence of the combined administration of baicalin and probiotic cocktails on the composition of ileal and cecal microbiota in broiler chickens to elucidate the underlying mechanisms responsible for the health-promoting effects.

RESULTS

A total of 320 1-day-old male Arbor Acres broilers were divided into 4 groups, each with 8 replicates of 10 chicks per replicate. Over a period of 42 d, the birds were fed a basal diet or the same diet supplemented with 37.5 g/t baicalin (BC), 1,000 g/t probiotic cocktails (PC), or a combination of both BC (37.5 g/t) and PC (1,000 g/t). The results demonstrated that BC + PC exhibited positive synergistic effects, enhancing intestinal morphology, immune function, and barrier function. This was evidenced by increased VH/CD ratio, sIgA levels, and upregulated expression of occludin and claudin-1 (P < 0.05). 16S rRNA analysis indicated that PC potentiated the effects of BC, particularly in the ileum, where BC + PC significantly increased the α-diversity of the ileal microbiota, altered its β-diversity, and increased the relative abundance of Flavonifractor (P < 0.05), a flavonoid-metabolizing bacterium. Furthermore, Flavonifractor positively correlated with chicken ileum crypt depth (P < 0.05). While BC + PC had a limited effect on cecal microbiota structure, the PC group had a very similar microbial composition to BC + PC, suggesting that the effect of PC at the distal end of the gut overshadowed those of BC.

CONCLUSIONS

We demonstrated the synergistic enhancement of gut health regulation in broiler chickens by combining baicalin and probiotic cocktails. Probiotic cocktails enhanced the effects of baicalin and accelerated its metabolism in the ileum, thereby influencing the ileal microbiota structure. This study elucidates the interaction mechanism between probiotic cocktails and plant extract additives within the host microbiota. These findings provide compelling evidence for the future development of feed additive combinations.

Dietary novel alkaline protease from Bacillus licheniformis improves broiler meat nutritional value and modulates intestinal microbiota and metabolites

BACKGROUND

Different types of exogenous protease supplements have a positive impact on animal performance, but their effects on the nutritional value of meat and the gut microbial community of broilers have not been extensively studied. The objective of this investigation was to determine the impact of supplementation with a novel alkaline protease derived from Bacillus licheniformis (at doses of 0, 100, 200, 300, and 400 g/t) on the fatty acid and amino acid profiles, inosine monophosphate (IMP) levels, total volatile basic nitrogen (TVB-N) content found within the breast muscle, as well as the impact on the cecal microbiota and metabolites.

RESULTS

Supplementation with 200-400 g/t of the novel protease resulted in a significant elevation in the concentration of essential amino acids (P < 0.001), flavor amino acids (P < 0.001), and total protein (P = 0.013) within the breast muscle. Results derived from the 16S rRNA sequencing and untargeted metabolomics analysis of the cecal content revealed that the novel protease reshaped the cecal microbial and metabolite profiles. In particular, it led to increased relative abundances of Bacteroides, Lactobacillus, Alistipes, and Eubacterium, while simultaneously causing a reduction in the metabolites of D-lactic acid and malonic acid. Moreover, correlation analyses unveiled significant relationships between distinct microbes and metabolites with the contents of IMP, fatty acids, and amino acids in the broiler's breast muscle.

CONCLUSION

In summary, the novel protease regulated the intestinal microbial community and metabolism, thereby inducing changes in the compositions of fatty acids and amino acids profiles, as well as IMP levels in broiler meat. These alterations significantly contributed to the enhancement of the nutritional value and flavor of the meat.

Selenium-enriched Bacillus subtilis Improves Growth Performance, Antioxidant Capacity, Immune Status, and Gut Health of Broiler Chickens

This study aimed to investigate the effects of selenium (Se)-enriched Bacillus subtilis (Se-BS) on growth performance, antioxidant capacity, immune status, and gut health in broilers. A total of 240 one-day-old Arbor Acres broilers were randomly allotted to four groups and fed with basal diet (control group), 0.30 mg/kg Se (SS group), 3 × 109 CFU/g B. subtilis (BS group), and 0.30 mg/kg Se + 3 × 109 CFU/g B. subtilis (Se-BS group) for 42 days. The results showed that Se-BS supplementation increased body weight (BW), average daily gain, the activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), and peroxidase (POD), total antioxidant capacity (T-AOC), and the contents of interleukin (IL)-2, IL-4, and immunoglobulin (Ig) G in plasma, the index and wall thickness of the duodenum, the villus height and crypt depth of the jejunum, and GPx-1 and thioredoxin reductase 1 mRNA levels in liver and intestine and decreased feed conversion ratio (FCR) and plasma malondialdehyde (MDA) content compared with the control group on day 42 (P < 0.05). Compared with groups SS and BS, Se-BS supplementation increased BW, the activities of GPx, CAT, and POD, and the contents of IL-2, IL-4, and IgG in plasma, the index and wall thickness of the duodenum, the crypt depth and secretory IgA content of the jejunum, and GPx-1 mRNA levels in liver and intestine and decreased FCR and plasma MDA content on day 42 (P < 0.05). In conclusion, Se-BS supplementation effectively improved the growth performance antioxidant capacity, immune status, and gut health of broilers.

A combination of selenium and Bacillus subtilis improves the quality and flavor of meat and slaughter performance of broilers

This study aimed to investigate the effects of the combination of selenium and Bacillus subtilis (Se-BS) on the quality and flavor of meat and slaughter performance of broilers. A total of 240 one-day-old Arbor Acres broilers were randomly allotted to four treatments of a basal diet supplemented with no selenium (control), sodium selenite (SS), BS, or Se-BS and raised for 42 days. Compared with the control group, Se-BS significantly increased the carcass weight, the half-eviscerated weight, the completely eviscerated weight, the carcass rate, and redness in broiler muscles; improved the antioxidant state by increasing glutathione peroxidase (GPx) and glutathione S-transferase activities, the total antioxidant capacity, and GPx-1 and thioredoxin reductase 1 messenger RNA (mRNA) levels; promoted biological activity by increasing the contents of glutamate, phenylalanine, lysine, and tyrosine; and increased Se and five types of nitrogenous volatile substances in muscles. On the other hand, Se-BS treatment decreased the shear force, drip loss, and the malondialdehyde, glutathione, and lead contents in muscles. Se-BS exerted a better effect on slaughter performance, the physicochemical quality of meat, the redox status, the amino acid contents, the trace element contents, and volatile substances compared with SS and BS. In conclusion, Se-BS had a positive effect on the quality and flavor of meat and slaughter performance of broilers, suggesting that Se-BS may be a beneficial feed additive.

Bacillus Subtilis (BG01-4TM) Improves Self-Reported Symptoms for Constipation, Indigestion, and Dyspepsia: A Phase 1/2A Randomized Controlled Trial

BACKGROUND

Functional gastrointestinal disorders (FGIDs) are common, difficult-to-manage conditions. Probiotics are emerging as a dietary component that influence gastrointestinal (GI) health. We conducted a double-blinded randomised controlled trial of a proprietary strain of deactivated Bacillus subtilis (BG01-4™) high in branched-chain fatty acids (BCFA) to treat self-reported FGID.

METHODS

Participants (n = 67) completed a four-week intervention of BG01-4™ (n = 34) or placebo (n = 33). The Gastrointestinal Symptom Rating Scale (GSRS) served as the outcome measure, collected prior to, at two weeks, and at four weeks after completion of the intervention.

RESULTS

At four weeks, one of three primary outcomes, constipation in the experimental group, was improved by 33% compared to placebo (15%); both other primary outcomes, Total GSRS and diarrhoea, were significantly improved in both the experimental and placebo groups (32%/26% and 20%/22%, respectively). The pre-planned secondary outcome, indigestion, was improved at four weeks (32%) but compared to the placebo (21%) was not significant (p = 0.079). Exploratory analysis, however, revealed that clusters for constipation (18% improvement, p < 0.001), indigestion (11% improvement, p = 0.04), and dyspepsia (10% improvement, p = 0.04) were significantly improved in the intervention group compared to the placebo.

CONCLUSIONS

These initial findings suggest that in people with self-reported FGID, BG01-4™ improves specific symptoms of constipation and related GI dysfunction. Longer-term confirmatory studies for this intervention are warranted.

TRIAL REGISTRATION

This study was registered prospectively (25 October 2021) at the Australian New Zealand Clinical Trials Registry (ACTRN12621001441808p).

Comparison of the Effects of Feeding Compound Probiotics and Antibiotics on Growth Performance, Gut Microbiota, and Small Intestine Morphology in Yellow-Feather Broilers

This study was devoted to the comparison of the probiotic effect of compound probiotics to antibiotics as a feed additive for chicken. Two hundred and seventy newly hatched yellow-feather broilers were randomly divided into three groups: the control group (Con), probiotics (Pb), and antibiotics group (Ab). The Pb group received compound probiotics (Bifidobacterium, Lactobacillus acidophilus, Streptococcus faecalis, and yeast) via drinking water for 24 days. The Ab group received antibiotics (zinc bacitracin and colistin sulfate) in their diet for 24 days. All broilers were slaughtered on day 42. Compared with the Con group, the body weight was significantly increased on days 13, 28, and 42 in the Pb group (p < 0.05), and markedly increased on day 28 in the Ab group (p < 0.05). Compared with the Ab group, the body weight of the broilers in the Pb group increased significantly on day 13 (p < 0.05). Compared to the Con and Pb groups, the antibiotics treatment reduced the feed intake (p < 0.05), but there was no significant difference in the feed conversion ratio between the Ab and Pb groups (p > 0.05). The feed conversion ratio of the broilers treated with antibiotics or probiotics significantly decreased compared to the Con group (p < 0.05). The depth of duodenum, jejunum, and ileum crypts in the Pb group decreased significantly compared to the Con and Ab group (p < 0.05). The ratio of the villi length to crypt depth of duodenum, jejunum, and ileum epithelium was significantly increased in the Pb group compared to the Con group (p < 0.05). The genera Bacteroides and Barnesiella were the most significantly enriched bacteria in the Ab and Pb groups, respectively (p < 0.05). The expression of the genes related to antibiotic resistance was significantly decreased in the Pb group compared to the Ab group (p < 0.05). Although both compound probiotics and antibiotics can improve growth performance, antibiotics increased the abundance of harmful bacteria and drug-resistant genes, while probiotics increased Barnesiella abundance, which is related to a decrease in the drug-resistant gene expression. Moreover, the probiotics treatment improved small intestinal morphology and fecal emissions, while antibiotics have no significant effect on these indicators, indicating a bright future for probiotics as an alternative to feed antibiotics in the yellow-feather broiler industry.

Bacillus subtilis KC1 prevents Mycoplasma gallisepticum-induced lung injury by enhancing intestinal Bifidobacterium animalis and regulating indole metabolism in chickens

It has been reported that dietary administration of Bacillus subtilis KC1 is effective in alleviating lung injury induced by Mycoplasma gallisepticum (MG) infection in chickens. However, the underlying molecular mechanism of B. subtilis KC1 against MG infection is still unclear. The purpose of this study was to determine whether B. subtilis KC1 could alleviate MG infection-induced lung injury in chickens by regulating their gut microbiota. The results of this study indicate that B. subtilis KC1 supplementation has the potential to alleviate MG infection-induced lung injury as reflected by reduced MG colonization, reduced pathologic changes, and decreased production of pro-inflammatory cytokines. In addition, B. subtilis KC1 supplementation was partially effective in alleviating the gut microbiota disorder caused by MG infection. Importantly, B. subtilis KC1 enriched the beneficial Bifidobacterium animalis in gut and thus reversed indole metabolic dysfunction caused by MG infection. B. subtilis KC1 supplementation increased levels of indole, which enhanced aryl hydrocarbon receptor activation, improving barrier function and alleviating lung inflammation caused by MG. Overall, this study indicates that B. subtilis KC1 has a "gut-lung axis" mechanism that can reduce the severity of MG infection by enriching intestinal B. animalis and regulating indole metabolism.

Protective Effects of Bacillus subtilis HH2 against Oral Enterotoxigenic Escherichia coli in Beagles

This study evaluated the protective effect of Bacillus subtilis HH2 on beagles orally challenged with enterotoxigenic Escherichia coli (ETEC). We assessed the physiological parameters and the severity of diarrhea, as well as the changes in three serum immunoglobulins (IgG, IgA, and IgM), plasma diamine oxidase (DAO), D-lactate (D-LA), and the fecal microbiome. Feeding B. subtilis HH2 significantly reduced the severity of diarrhea after the ETEC challenge (p < 0.05) and increased serum levels of IgG, IgA, and IgM (p < 0.01). B. subtilis HH2 administration also reduced serum levels of DAO at 48 h after the ETEC challenge (p < 0.05), but no significant changes were observed in D-LA (p > 0.05). Oral ETEC challenge significantly reduced the richness and diversity of gut microbiota in beagles not pre-fed with B. subtilis HH2 (p < 0.05), while B. subtilis HH2 feeding and oral ETEC challenge significantly altered the gut microbiota structure of beagles (p < 0.01). Moreover, 14 days of B. subtilis HH2 feeding reduced the relative abundance of Deinococcus-Thermus in feces. This study reveals that B. subtilis HH2 alleviates diarrhea caused by ETEC, enhances non-specific immunity, reduces ETEC-induced damage to the intestinal mucosa, and regulates gut microbiota composition.

Dietary Probiotics Modulate Gut Barrier and Immune-Related Gene Expression and Histomorphology in Broiler Chickens under Non- and Pathogen-Challenged Conditions: A Meta-Analysis

Data published in the literature about the favorable effects of dietary probiotics on gut health in broiler chickens are inconsistent. To obtain a more comprehensive understanding, we conducted a meta-analysis to assess the effects of probiotics on the gut barrier and immune-related gene expression, histomorphology, and growth in chickens that were either challenged or non-challenged with pathogens. From the 54 articles published between 2012 and 2022, subsets of data, separately for non-challenged and challenged conditions, for response variables were created. The mean dietary probiotic concentrations ranged from 4.7 to 6.2 and 4.7 to 7.2 log₁₀ colony-forming unit/kg under non-challenged and challenged conditions, respectively. Probiotics increased the expression of genes for mucins and tight junction proteins in the jejunum and ileum at weeks 3 and 6. The stimulatory effect of probiotics on tight junction protein expression was partly stronger in challenged than in non-challenged birds. Meta-regressions also showed an anti-inflammatory effect of probiotics under challenged conditions by modulating the expression of cytokines. Probiotics improved villus height at certain ages in the small intestine while not influencing growth performance. Dietary metabolizable energy, crude protein, and days post-infection modified the effects of probiotics on the observed variables. Overall, meta-regressions support the beneficial effects of probiotics on gut integrity and structure in chickens.

Recent Trends on Mitigative Effect of Probiotics on Oxidative-Stress-Induced Gut Dysfunction in Broilers under Necrotic Enteritis Challenge: A Review

Gut health includes normal intestinal physiology, complete intestinal epithelial barrier, efficient immune response, sustained inflammatory balance, healthy microbiota, high nutrient absorption efficiency, nutrient metabolism, and energy balance. One of the diseases that causes severe economic losses to farmers is necrotic enteritis, which occurs primarily in the gut and is associated with high mortality rate. Necrotic enteritis (NE) primarily damages the intestinal mucosa, thereby inducing intestinal inflammation and high immune response which diverts nutrients and energy needed for growth to response mediated effects. In the era of antibiotic ban, dietary interventions like microbial therapy (probiotics) to reduce inflammation, paracellular permeability, and promote gut homeostasis may be the best way to reduce broiler production losses. The current review highlights the severity effects of NE; intestinal inflammation, gut lesions, alteration of gut microbiota balance, cell apoptosis, reduced growth performance, and death. These negative effects are consequences of; disrupted intestinal barrier function and villi development, altered expression of tight junction proteins and protein structure, increased translocation of endotoxins and excessive stimulation of proinflammatory cytokines. We further explored the mechanisms by which probiotics mitigate NE challenge and restore the gut integrity of birds under disease stress; synthesis of metabolites and bacteriocins, competitive exclusion of pathogens, upregulation of tight junction proteins and adhesion molecules, increased secretion of intestinal secretory immunoglobulins and enzymes, reduction in pro-inflammatory cytokines and immune response and the increased production of anti-inflammatory cytokines and immune boost via the modulation of the TLR/NF-ĸ pathway. Furthermore, increased beneficial microbes in the gut microbiome improve nutrient utilization, host immunity, and energy metabolism. Probiotics along with biosecurity measures could mitigate the adverse effects of NE in broiler production.

Compound probiotics can improve intestinal health by affecting the gut microbiota of broilers

Probiotics, as a widely used additive, have played a unique advantage in replacing antibiotic products. As a result, the probiotic effects on broiler development, intestinal flora, intestinal barrier, and immunity were assessed by this investigation. Four hundred and eighty 1-day-old Arbor Acres broilers were randomly allotted to 4 groups of 5 replicates with 24 broilers each. The control was fed only a basal corn-soybean meal diet. Probiotics I, probiotics II, and probiotics III were fed basal diet and 1, 5, and 10 g/kg compound probiotics (Lactobacillus casei: Lactobacillus acidophilus: Bifidobacterium = 1:1:2), respectively. We found that broilers in the compound probiotic group exhibited better growth performance and carcass characteristics compared with control, especially among probiotics III group. The intestinal barrier-related genes relative expression of Claudin, Occludin, MUC2, and ZO-1 mRNA in the probiotic group increased at 21 and 42 d compared with control, especially among probiotics III group (P < 0.05). The early gut immune-related genes (TLR2, TLR4, IL-1β, and IL-2) mRNA increased compared with control, while the trend at 42 d was completely opposite to that in the earlier stage (P < 0.05). Among them, probiotics III group showed the most significant changes compared to probiotics II group and probiotics I group. Select probiotics III group and control group for 16S rDNA amplicon sequencing analysis. The 16S rDNA amplicon sequencing results demonstrated that probiotics increased the relative abundance of beneficial microbes such as o_Bacteroidales, f_Rikenellaceae, and g_Alistipes and improved the cecum's gut microbiota of 42-day-old broilers. Additionally, adding the probiotics decreased the relative abundance of harmful microbes such as Proteobacteria. PICRUSt2 functional analysis revealed that most proteins were enriched in DNA replication, transcription, and glycolysis processes. Therefore, this study can provide theoretical reference value for probiotics to improve production performance, improve intestinal barrier, immunity, intestinal flora of broilers, and the application of probiotics.

Effects of dietary supplementation probiotic complex on growth performance, blood parameters, fecal harmful gas, and fecal microbiota in AA+ male broilers

In this study, Bacillus subtilis, Clostridium butyricum and Enterococcus faecalis were made into a probiotic complex (PC). The PC was supplemented in AA+ male broilers' diets to investigate the effects of PC on broiler growth performance, carcass traits, blood indicators, harmful gas emissions in feces and microbiota. Three hundred and sixty 1-day-old AA+ male broilers with an average initial body weight (data) were randomly divided into 3 dietary treatments of 6 replicates each, with 20 birds per replicate. The control group (T0) was fed a basal diet, while the test groups (T1 and T2) were supplemented with 0.025 and 0.05% PC in the basal diet, respectively. The trail was 42 days. The results showed that the supplementation of 0.05% PC significantly (p < 0.05) improved average daily gain (ADG) and average daily feed intake (ADFI) of broilers from 22 to 42 days and 1-42 days. Compared to the control group, the breast rate was significantly higher in T2, and the thymic index was significantly higher than that in T1 treatment (p < 0.05). The addition of PC had no significant effects on antibody potency in broiler serum (p > 0.05), but significantly increased albumin and total protein content in serum (p < 0.05). The addition of PC reduced H₂S and NH₃ emissions in the feces; the levels of Escherichia coli and Salmonella in the feces were significantly reduced and the levels of Lactobacillus were increased. And the most significant results were achieved when PC was added at 0.05%. Correlation analysis showed a significant positive correlation (p < 0.05) between the levels of E. coli and Salmonella and the emissions of H₂S and NH₃. Conclusion: Dietary supplementation with a 0.05% probiotic complex could improve the growth performance of broilers and also reduced fecal H₂S and NH₃ emissions, as well as fecal levels of E. coli and Salmonella, and increased levels of Lactobacillus. Thus, PC made by Bacillus subtilis, Clostridium butyricum and Enterococcus faecalis is expected to be an alternative to antibiotics. And based on the results of this trial, the recommended dose for use in on-farm production was 0.05%.

Oregano Oil Combined with Macleaya Cordata Oral Solution Improves the Growth Performance and Immune Response of Broilers

Simple Summary

Developing safe and effective antibiotic growth promoters (AGPs) substitutes is particularly important to improve animal health and production performance. As an essential plant oil, the oregano oil's main bioactive substance is carvacrol, which has been proven to have antioxidant, anti-inflammatory, antibacterial, and antiviral properties. The sanguinarine from macleaya cordata is the primary bioactive substance. Sanguinarine has anti-tumor, immune-enhancing, antibacterial, and anti-inflammatory effects. However, it has not been reported whether the compatibility of oregano oil and macleaya cordata extract could produce better results. This study is the first to report the effect of oregano oil combined with macleaya cordata oral solution on the growth of broilers. The oregano oil combined with macleaya cordata oral solution significantly improved the growth performance of broilers. At the same time, serum biochemical indices, serum antioxidant indices, serum immune indices, serum cytokines, and intestinal morphology were significantly improved. In summary, our results demonstrated that the mixed solution of oregano oil and macleaya cordata has substantial potential to be an alternative to AGPs for broilers to reduce costs and improve benefits. This study provides basic data and technical support for further research.

Abstract

The abuse of AGPs in animal husbandry has led to severe problems such as drug resistance and ecological, and environmental destruction, which seriously threaten human health and public health security. In recent years, extracts of oregano oil and macleaya cordata have become a hot spot in the research and application of AGP substitutes for their safety and high efficiency. This study is the first to report the effect of oregano oil combined with macleaya cordata oral solution on broiler growth performance. A total of 960 one-day-old broiler chickens were randomly divided into four treatment groups (240 chickens per group). Each treatment group was divided into six replicate groups (40 birds per replicate group). There were four groups in this study: the solvent control group, the oregano essential oil combined with macleaya cordata extract oral solution group (OS group), the oregano essential oil oral solution group (OEO group), and the macleaya cordata extract oral solution group (MCE group). Two chickens from each replicate group were collected and mixed into a composite sample. Six composite samples were obtained for each treatment group. The results showed that the oregano oil combined with macleaya cordata oral solution significantly improved the growth performance of broiler chickens. At the same time, serum biochemical indices, serum antioxidant indices, serum immune indices, serum cytokines, and intestinal morphology were significantly improved by the OS group. This study shows that oregano oil combined with macleaya cordata oral solution has substantial potential to be an alternative to AGPs for broilers.

Enhancing egg production and quality by the supplementation of probiotic strains (Clostridium and Brevibacillus) via improved amino acid digestibility, intestinal health, immune response, and antioxidant activity

This study focused on evaluating the influence of Clostridium butyricum and Brevibacillus strains on egg production, egg quality, immune response and antioxidant function, apparent fecal amino acid digestibility, and jejunal morphology when supplemented as probiotics in the diets of laying hens in the peak phase. A total of 288 healthy 30-week-old Hy-Line Brown laying hens were arbitrarily assigned to four dietary groups, which included control diet and control diet supplemented with 0.02% C. butyricum zlc-17, C. butyricum lwc-13, or Brevibacillus zlb-z1, for 84 days. The results showed that dietary C. butyricum and Brevibacillus sp. exerted a positively significant influence (P ≤ 0.05) compared to the control group on the performance, egg quality, and physiological response of the birds. The diets could reduce mortality rate and enhance (P ≤ 0.05) egg weight and egg mass, egg production rate, and feed efficiency. Further analysis suggested that the probiotic strains can enhance (P ≤ 0.05) eggshell quality, Haugh unit, thick albumen content, and albumen height. Also, probiotics enhanced (P ≤ 0.05) the antioxidant status via increased antioxidant enzymes and jejunal morphology as evidenced by increased villi surface area (VSA), the ratio of villi height to crypt depth, villi width, and villi height, and a significant reduction in crypt depth. Besides, nutrient absorption and retention were enhanced, as apparent fecal amino acid digestibility of key essential amino acids was substantially improved in the diet-based group. The concentrations of immunoglobulin M and A (IgM and IgA) increased significantly (P ≤ 0.05) in the probiotics group and the same effect was notable for complement proteins (C3) and immune organ (Spleen). Conclusively, the supplementation of Clostridium butyricum zlc-17 in comparison to Clostridium butyricum lwc-13 and Brevibacillus zlb-z1 strains significantly (P ≤ 0.05) promoted the antioxidant status, modulated the intestinal structure, enhanced amino acid digestibility, and regulated the immunity index of the laying hens, which finally improves the laying performance and egg quality of the laying hens.

Comparing the potential of Bacillus amyloliquefaciens CGMCC18230 with antimicrobial growth promoters for growth performance, bone development, expression of phosphorus transporters, and excreta microbiome in broiler chickens

Bone health of broiler chickens is essential for welfare and production. In this study, the probiotic Bacillus amyloliquefaciens (BA) CGMCC18230 was compared with antimicrobial growth promoters (AGPs) for its ability to promote growth and bone health. To address this, a total of 180 Arbor Acres (AA) 1-day-old, male, broiler chicks were randomly allocated into 3 treatment groups, with 6 replicates, containing 10 chicks in each replicate. The treatment groups were: control group (CON) fed a corn-soybean based diet; BA treatment group fed the basal diet supplemented with 2.5 × 10¹⁰ CFU/kg BA CGMCC18230; AGPs treatment group was fed the basal diet containing the antibiotics aureomycin (75 mg/kg), flavomycin (5 mg/kg) and kitasamycin (20 mg/kg). Over the 42 d experiment, broilers fed BA and AGPs diets both had higher BW, and the ADG was significantly (P < 0.05) higher than that of the CON group both in the grower phase (22–42 d) and overall. Moreover, with BA birds had higher (P < 0.05) serum concentrations of phosphorus (P, day 42) and alkaline phosphatase (ALP, days 21 and 42). Conversely, the content of P in excreta decreased significantly (P < 0.05) on days 21 and 42. Tibia bone mineralization was improved in BA, and the mRNA of P transport related genes PiT-1,2 in the duodenum and jejunum were significantly up-regulated in the BA group than in the CON group (P < 0.05). 16S rRNA gene sequencing revealed that dietary BA supplementation increased the relative abundance of butyrate-producing bacteria (Ruminococcaceae) and polyamine-producing bacteria (Akkermansia and Alistipes), which had a positive effect on bone development. These data show that dietary supplementation of BA CGMCC18320 improves broiler growth performance and bone health similar to supplementation with AGPs through up-regulation of intestinal P transporters, microbial modulation and increase P retention. However, no significant influence of BA CGMCC18320 supplementation on the retention of Ca was found.

Effects of Dietary Macleaya cordata Extract Containing Isoquinoline Alkaloids Supplementation as an Alternative to Antibiotics in the Diets on Growth Performance and Liver Health of Broiler Chickens

This study aimed to investigate the effects of dietary supplementation with Macleaya cordata extract (MCE) containing protopine and allotypotopine on the growth performance and liver health in broiler chickens. A total of 486 1-day-old male AA broiler chickens were randomly assigned to the following three groups: (1) control (CON) group, broiler chickens fed a basal diet; (2) AGP group (positive control), broiler chickens fed a basal diet supplemented with 50 mg/kg aureomycin; (3) MCE group, broiler chickens fed a basal diet supplemented with 0.6 mg/kg MCE including 0.4 mg/kg protopine and 0.2 mg/kg allotypotopine. The results showed that the MCE group had significantly higher final body weight and average daily gain from d 0 to 42 than the other groups (p < 0.05), and groups MCE and AGP both had significantly lower feed-to-gain ratio from d 0 to 42 than the CON group (p < 0.05). Serum total protein, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, total cholesterol, glucose, immunoglobulin A, immunoglobulin M, and complements (C3, C4) concentrations in the MCE group were significantly higher than in the CON group (p < 0.05). Dietary MCE or aureomycin supplementation significantly reduced the hepatic contents of 8-hydroxy-2'-deoxyguanosine, malondialdehyde, interleukin (IL)-1β, IL-6, NLRs family pyrin domain containing 3 (NLRP3), and caspase-1 in the liver (p < 0.05). Moreover, MCE or aureomycin supplementation significantly inhibited mRNA expressions of Toll-like receptor 4, myeloid differentiation factor 88, nuclear factor-κB, and NLRP3, as well as the expression ratio of Bax to Bcl-2 mRNA (p < 0.05). Therefore, our study suggested that dietary supplementation with 0.6 mg/kg MCE containing protopine and allocryptopine improved growth performance and benefited liver health in broiler chickens possibly through inhibiting caspase-1-induced pyroptosis by inactivating TLR4/MyD88/NF-κB/NLRP3 signaling pathway, and provided support for the application of MCE containing protopine and allocryptopine as an alternative to antibiotics in the feed industry.

Dietary supplementation of Bacillus velezensis improves Vibrio anguillarum clearance in European sea bass by activating essential innate immune mechanisms

Bacillus spp. supplementation as probiotics in cultured fish diets has a long history of safe and effective use. Specifically, B. velezensis show great promise in fine-tuning the European sea bass disease resistance against the pathogenicity caused by several members of the Vibrio family. However, the immunomodulatory mechanisms behind this response remain poorly understood. Here, to examine the inherent immune variations in sea bass, two equal groups were fed for 30 days with a steady diet, with one treatment supplemented with B. velezensis. The serum bactericidal capacity against live cells of Vibrio anguillarum strain 507 and the nitric oxide and lysozyme lytic activities were assayed. At the cellular level, the phagocytic response of peripheral blood leukocytes against inactivated Candida albicans was determined. Moreover, head-kidney (HK) total leukocytes were isolated from previously in vivo treated fish with LPS of V. anguillarum strain 507. Mechanistically, the expression of some essential proinflammatory genes (interleukin-1 (il1b), tumor necrosis factor-alpha (tnfa), and cyclooxygenase 2 (cox2) and the sea bass specific antimicrobial peptide (AMP) dicentracin (dic) expressions were assessed. Surprisingly, the probiotic supplementation significantly increased all humoral lytic and cellular activities assayed in the treated sea bass. In addition, time-dependent differences were observed between the control and probiotic treated groups for all the HK genes markers subjected to the sublethal LPS dose. Although the il1b was the fastest responding gene to a significant level at 48 h post-injection (hpi), all the other genes followed 72 h in the probiotic supplemented group. Finally, an in vivo bacteria challenge against live V. anguillarum was conducted. The probiotic fed fish observed a significantly higher survival. Overall, our results provide clear vertical evidence on the beneficial immune effects of B. velezensis and unveil some fundamental immune mechanisms behind its application as a probiotic agent in intensively cultured European sea bass.