Characterization of intestinal immune response to Clostridium perfringens infection in broiler chickens

Alternative to antimicrobial growth promoters in the diets of broilers challenged with subclinical necrotic enteritis

Necrotic enteritis (NE) is a disease of worldwide distribution, which affects young broilers and causes economic losses on a scale of 6 billion dollars per year. For decades, NE was controlled in poultry flocks by dietary administration of low doses of antimicrobial growth promoters (AGPs). However, an increase in NE incidence was noted after the AGP ban. This study aimed to compare the effect of an antibiotic (Enramycin) diet to a combination of sodium butyrate, hydrolyzed yeast, and zinc proteinate (ViligenTM) on broiler diets regarding performance, blood parameters, intestinal permeability, morphology and lesions, and carcass yield of broilers challenged with Eimeria spp. and Clostridium perfringens to simulate subclinical necrotic enteritis. A total of 1,150 one-day-old male broiler chickens with an initial average weight of 43.9 ± 0.65 g were allocated to 50 experimental pens. Animals were divided into 5 groups: Negative control (NC) without additives; Positive control (PC) with 0.12 g/ton of Enramycin (8%); V500, V1000, and V1500 with the addition of 500, 1.000, and 1.500 g/ton of Viligen, respectively. All animals were challenged by Eimeria spp. at 7 d of age and by C. perfringens at 17, 18, and 19 d for induction of subclinical NE. The broilers fed with all concentrations of Viligen showed similar performance, blood parameters, intestinal permeability, and carcass yield compared to PC broilers. However, NC broilers showed higher FCR compared to PC broilers from 1 to 33 d (1.42 vs. 1.39) (P = 0.048) and from 1 to 42 d (1.51 vs. 1.49) (P < 0.001). V1500 broilers had fewer intestinal lesions at 28 d when compared to the PC treatment (P < 0.05) and showed that higher Viligen inclusion resulted in lower intestinal damage. At 21 d, the V500 group showed higher intestinal morphology characteristics (VH:VD 4.9 vs. 3.5) compared to the PC treatment (P < 0.001). Thus, in this study, the dietary addition of Viligen to broilers challenged by an experimental model of subclinical NE resulted in lower intestinal damage and similar performance to that obtained by the addition of Enramycin.

Characterization of spray-dried plasma-induced immune response in Salmonella-challenged broiler chicks

Spray-dried plasma (SDP) is a functional feed additive that has been established to improve performance and health of livestock. Understanding the effect of SDP in immune response modulation is essential to optimize its use for controlling Salmonella Enteritidis (SE) infection in chickens. This study was conducted to determine the levels of expression of selected cytokine genes in the ileum and cecal tonsil of SE-challenged broiler chicks. In a floor-pen housing, 320 broilers chicks were randomly assigned to 6 treatment groups: CX (unmedicated corn-soybean meal (SBM) basal without SDP), MX (unmedicated corn-SBM basal with antibiotic bacitracin methylene disalicylate (BMD) added at 0.055g/kg diet), PCX (unmedicated corn-SBM basal with SDP added at 30g/kg diet). Treatments SE, MSE, and PSE consisted of chicks inoculated with 7.46 × 108 CFU SE /mL at 1 d of age and given diets similar to CX, MX, and PCX, respectively. Samples of cecal tonsils and ileum were collected on d 3, 7 and 14 post infection for qRT-PCR analysis to determine the expression levels of interleukin (IL)-1β, interferon-γ (IFN-γ), IL-13, IL-17, IL-6, and transforming growth factor (TGF)-β genes. In the ceca tonsils, expression of IFN-γ was not affected by the interaction of Day and Treatment (P > 0.05). The level of the anti-inflammatory cytokine IL-13 was lower in MX and PCX on d 7 whereas high levels were expressed (P < 0.05) in MSE and PSE. In the ileum, expression of IL-17 and IFN-γ was significantly lower (P < 0.05) in PSE and MSE, but only PSE expressed lower IL-6 comparable to unchallenged treatments. On d 28 postchallenge, concentrations of anti-SE IgY and IL-6 protein were higher (P < 0.05) in the SE-challenged treatments compared to the unchallenged treatments. Overall, these results suggest that dietary SDP showed similar potency to BMD in modulating intestinal cytokine response against intestinal SE colonization in broiler chicks and therefore can be considered suitable alternative replacement for antibiotics in broiler production.

Black soldier fly larvae oil (Hermetia illucens L.) calcium salt enhances intestinal morphology and barrier function in laying hens

This study aimed to determine the influence of black soldier fly larvae oil calcium salt (BSFLO-SCa) supplementation on performance, jejunal histomorphology and gene expression of tight junctions and inflammatory cytokines in laying hens. A total of 60 ISA Brown laying hens (40 wk of age) were divided into 3 treatment groups, including a control group fed a basal diet (T0) and basal diets supplemented with 1% (T1) and 2% (T2) of BSFLO-SCa. Each treatment group consisted of 5 replicates with 4 laying hens each. Results showed that 1% and 2% BSFLO-SCa supplementation significantly reduced (P < 0.05) feed conversion ratio (FCR), while egg weight (EW) increased (P < 0.05). The inclusion with 2% increased (P < 0.05) both egg production (HDA) and mass (EM). The addition of 1% and 2% BSFLO-SCa significantly increased (P < 0.05) villus height (VH) and villus width (VW), while crypt depth (CD) significantly increased (P < 0.05) with 2% BSFLO-SCa. The tight junction and gene expression of claudin-1 (CLDN-1), junctional adhesion molecules-2 (JAM-2), and occludin (OCLN) were significantly upregulated (P < 0.05) with 2% BSFLO-SCa. The pro-inflammatory cytokines and gene expression of interleukin-6 (IL-6) was significantly downregulated (P < 0.05) with the addition of BSFLO-SCa, while gene expression of interleukin-18 (IL-18), toll-like receptor 4 (TLR-4), and tumor necrosis factor-α (TNF-α) were downregulated with 2% BSFLO-SCa. On the other hand, the anti-inflammatory cytokines and gene expression of interleukin-13 (IL-13) and interleukin-10 (IL-10) were significantly upregulated (P < 0.05) at 2% BSFLO-SCa. In conclusion, dietary supplementation with 2% BSFLO-SCa improved productivity, intestinal morphology and integrity by upregulating tight junction-related protein of gene expression of laying hens. In addition, supplementation with BSFLO-SCa enhanced intestinal immune responses by upregulating anti-inflammatory and downregulating pro-inflammatory cytokine gene expression.

The Effects of Bacillus amyloliquefaciens SC06 on Behavior and Brain Function in Broilers Infected by Clostridium perfringens

Poultry studies conducted on Clostridium perfringens (CP) mainly focus on the effects of intestinal health and productive performance. Notably, the probiotic Bacillus amyloliquefaciens SC06 (BaSC06) is known to play a role in preventing bacterial infection. However, whether CP could induce the changes in brain function and behaviors and whether BaSC06 could play roles in these parameters is yet to be reported. The aim of this study was to evaluate the effects of BaSC06 on stress-related behaviors and gene expression, as well as the brain morphology and mRNA sequence of the hypothalamus in broiler chickens. A total of 288 one-day-old chicks were randomly divided into four groups: (1) a control group with no treatment administered or infection; (2) birds treated with the BaSC06 group; (3) a CP group; and (4) a BaSC06 plus CP (Ba_CP) group. The results showed that stress and fear-related behaviors were significantly induced by a CP infection and decreased due to the treatment of BaSC06. CP infection caused pathological damage to the pia and cortex of the brain, while BaSC06 showed a protective effect. CP significantly inhibited hypothalamic GABA and promoted HTR1A gene expression, while BaSC06 promoted GABA and decreased HTR1A gene expression. The different genes were nearly found between the comparisons of control vs. Ba group and Ba vs. CP group, while there were a great number of different genes between the comparisons of control vs. Ba_CP as well as CP vs. Ba_CP. Several different gene expression pathways were found that were related to disease, energy metabolism, and nervous system development. Our results will help to promote poultry welfare and health, as well as provide insights into probiotics to replace antibiotics and reduce resistance in the chicken industry.

Bacillus subtilis HW2 enhances growth performance and alleviates gut injury via attenuation of endoplasmic reticulum stress and regulation of gut microbiota in broilers under necrotic enteritis challenge

This study investigated the effects of Bacillus subtilis HW2 on the growth performance, immune response, endoplasmic reticulum (ER) stress, and intestinal health in broilers with necrotic enteritis. Three hundred 1-day-old male Cobb 500 broilers (33.88 ± 2.34 g) were randomly allocated to 5 groups including non-infected control (NC group), basal diet + necrotic enteritis challenge (NE group), basal diet + 1 × 106 CFU/g B. subtilis HW2 + necrotic enteritis challenge (L-Pro group), basal diet + 5 × 106 CFU/g B. subtilis HW2 + necrotic enteritis challenge (M-Pro group), and basal diet + 1 × 107 CFU/g B. subtilis HW2 + necrotic enteritis challenge (H-Pro group), with 6 replicates per group. All broilers except NC group were orally given with sporulated coccidian oocysts at day 14 and Clostridium perfringens from days 19 to 21. Results showed that L-Pro and M-Pro groups improved growth performance and intestinal morphology in necrotic enteritis-challenged broilers, and L-Pro, M-Pro, and H-Pro groups improved intestinal barrier function and immune response and decreased ER stress in necrotic enteritis-challenged broilers. Analysis of the gut microbiota revealed that L-Pro group increased the abundances of Alistipes, Coprobacter, Barnesiella, and Limosilactobacillus, decreased Erysipelatoclostridium abundance on day 42 in necrotic enteritis-challenged broilers. M-Pro group increased Turicibacter abundance on day 28 and the abundances of Alistipes, Barnesiella, and Limosilactobacillus on day 42 in necrotic enteritis-challenged broilers. H-Pro group decreased Romboutsia abundance on day 28 and unidentified_Clostridia abundance on day 42 in necrotic enteritis-challenged broilers. Analysis of short-chain fatty acids (SCFAs) revealed higher isobutyric acid and isovaleric acid levels in L-Pro and M-Pro groups than NE group. Correlation analysis revealed the correlations between the biochemical parameters and gut microbiota as well as SCFAs, especially Romboutsia, Barnesiella, Coprobacter, isobutyric acid, and isovaleric acid. Overall, our results indicated that B. subtilis HW2 supplementation could ameliorate necrotic enteritis infection-induced gut injury. The optimal dietary supplementation dosage of Bacillus subtilis HW2 was 5 × 106 CFU/g.

Immunization of turkeys with Clostridium septicum alpha toxin-based recombinant subunit proteins can confer protection against experimental Clostridial dermatitis

Clostridial dermatitis (CD), caused by Clostridium septicum, is an emerging disease of increasing economic importance in turkeys. Currently, there are no effective vaccines for CD control. Here, two non-toxic domains of C. septicum alpha toxin, namely ntATX-D1 and ntATX-D2, were identified, cloned, and expressed in Escherichia coli as recombinant subunit proteins to investigate their use as potential vaccine candidates. Experimental groups consisted of a Negative control (NCx) that did not receive C. septicum challenge, while the adjuvant-only Positive control (PCx), ntATX-D1 immunization (D1) and ntATX-D2 immunization (D2) groups received C. septicum challenge. Turkeys were immunized subcutaneously with 100 μg of protein at 7, 8 and 9 weeks of age along with an oil-in-water nano-emulsion adjuvant, followed by C. septicum challenge at 11 weeks of age. Results showed that while 46.2% of birds in the PCx group died post-challenge, the rate of mortality in D1- or D2-immunization groups was 13.3%. The gross and histopathological lesions in the skin, muscle and spleen showed that the disease severity was highest in PCx group, while the D2-immunized birds had significantly lower lesion scores when compared to PCx. Gene expression analysis revealed that PCx birds had significantly higher expression of pro-inflammatory cytokine genes in the skin, muscle and spleen than the NCx group, while the D2 group had significantly lower expression of these genes compared to PCx. Peripheral blood cellular analysis showed increased frequencies of activated CD4+ and/or CD8+ cells in the D1 and D2-immunized groups. Additionally, the immunized turkeys developed antigen-specific serum IgY antibodies. Collectively, these findings indicate that ntATX proteins, specifically the ntATX-D2 can be a promising vaccine candidate for protecting turkeys against CD and that the protection mechanisms may include downregulation of C. septicum-induced inflammation and increased CD4+ and CD8+ cellular activation.

Cell-Free Culture Supernatant of Lactobacillus acidophilus AG01 and Bifidobacterium animalis subsp. lactis AG02 Reduces the Pathogenicity of NetB-Positive Clostridium perfringens in a Chicken Intestinal Epithelial Cell Line

The worldwide reduction in the use of antibiotics in animal feed is fueling the need for alternatives for the prevention and control of poultry intestinal diseases such as necrotic enteritis (NE), which is caused by Clostridium perfringens. This is the first report on the use of an intestinal epithelial chicken cell line (CHIC-8E11) to study the pathogenic traits of C. perfringens and to investigate the mode of action of cell-free supernatants (CFS) from probiotic Lactobacillus acidophilus AG01 and Bifidobacterium animalis subsp. lactis AG02 in reducing the pathogenicity of C. perfringens. The cell adhesion, permeability and cytotoxicity were assessed under challenge with four C. perfringens strains isolated from broiler NE episodes of differing geographical origin (CP1-UK; CP10-Sweden; 25037-CP01 and CP22-USA). All the C. perfringens strains could adhere to the CHIC-8E11 cells, with varying affinity (0.05-0.48% adhesion across the strains). The CFS from one out of two strains (CP22) increased the cell permeability (+4.5-fold vs. the control, p < 0.01), as measured by the fluorescein isothiocyanate-dextran (FD4) content, with NetB toxin implicated in this effect. The CFS from all the strains was cytotoxic against the CHIC-8E11 cells in a dose- and strain-dependent manner (cytotoxicity 23-62% across the strains when dosed at 50 µL/mL, as assessed by the MTT cell viability assay). Pre-treatment of the cells with CFS from B. animalis subsp. lactis AG02 but not L. acidophilus AG01 reduced the cell adhesion of three out of four C. perfringens strains (by 77-85% vs. the control, p < 0.001) and reduced the negative effect of two NetB-positive strains on the cell permeability. The CFS of both probiotics alleviated the cytotoxicity of all the C. perfringens strains, which was dependent on the dose. The results confirm the suitability of the CHIC-8E11 cell line for the study of host-pathogen cell interactions in the context of NE caused by C. perfringens and reveal a beneficial mode of action of B. animalis subsp. lactis AG02 in reducing C. perfringens cell adhesion and, together with L. acidophilus AG01, in reducing C. perfringens cytotoxicity.

Unraveling frontiers in poultry health (part 1) - Mitigating economically important viral and bacterial diseases in commercial Chicken and Turkey production

This symposium offered up-to-date perspectives on field experiences and the latest research on significant viral and bacterial diseases affecting poultry. A highlight was the discussion on the use of enteroids as advanced in vitro models for exploring disease pathogenesis. Outcomes of this symposium included identifying the urgent need to improve the prevention and control of avian influenza by focusing research on vaccine effectiveness. In this regard, efforts should focus on enhancing the relatedness of vaccine antigen to the field (challenge) virus strain and improving immunogenicity. It was also revealed that gangrenous dermatitis could be controlled through withholding or restricting the administration of ionophores during broiler life cycle, and that administration of microscopic polymer beads (gel) based-live coccidia vaccines to chicks could be used to reduce necrotic enteritis-induced mortality. It was emphasized that effective diagnosis of re-emerging Turkey diseases (such as blackhead, fowl cholera, and coccidiosis) and emerging Turkey diseases such as reoviral hepatitis, reoviral arthritis, Ornithobacterium rhinotracheale infection, and strepticemia require complementarity between investigative research approaches and production Veterinarian field approaches. Lastly, it was determined that the development of a variety of functionally-specific enteroids would expedite the delineation of enteric pathogen mechanisms and the identification of novel vaccine adjuvants.

How did antibiotic growth promoters increase growth and feed efficiency in poultry?

It has been hypothesized that reducing the bioenergetic costs of gut inflammation as an explanation for the effect of antibiotic growth promoters (AGPs) on animal efficiency, framing some observations but not explaining the increase in growth rate or the prevention of infectious diseases. The host's ability to adapt to alterations in environmental conditions and to maintain health involves managing all physiological interactions that regulate homeostasis. Thus, metabolic pathways are vital in regulating physiological health as the energetic demands of the host guides most biological functions. Mitochondria are not only the metabolic heart of the cell because of their role in energy metabolism and oxidative phosphorylation, but also a central hub of signal transduction pathways that receive messages about the health and nutritional states of cells and tissues. In response, mitochondria direct cellular and tissue physiological alterations throughout the host. The endosymbiotic theory suggests that mitochondria evolved from prokaryotes, emphasizing the idea that these organelles can be affected by some antibiotics. Indeed, therapeutic levels of several antibiotics can be toxic to mitochondria, but subtherapeutic levels may improve mitochondrial function and defense mechanisms by inducing an adaptive response of the cell, resulting in mitokine production which coordinates an array of adaptive responses of the host to the stressor(s). This adaptive stress response is also observed in several bacteria species, suggesting that this protective mechanism has been preserved during evolution. Concordantly, gut microbiome modulation by subinhibitory concentration of AGPs could be the result of direct stimulation rather than inhibition of determined microbial species. In eukaryotes, these adaptive responses of the mitochondria to internal and external environmental conditions, can promote growth rate of the organism as an evolutionary strategy to overcome potential negative conditions. We hypothesize that direct and indirect subtherapeutic AGP regulation of mitochondria functional output can regulate homeostatic control mechanisms in a manner similar to those involved with disease tolerance.

Effect of treatment with Lactococcus lactis NZ9000 on intestinal microbiota and mucosal immune responses against Clostridium perfringens in broiler chickens

Alterations in intestinal microbiota can modulate the developing avian intestinal immune system and, subsequently, may impact on resistance to enteric pathogens. The aim was to demonstrate that early life exposure to Lactococcus lactis, could affect either susceptibility or resistance of broilers to necrotic enteritis (NE). L. lactis NZ9000 (rL. lactis) pre-treatment at 1, 7, 14 and 21 days of age (DOA) led to a significant decrease in NE lesion scores in Clostridium perfringens infected chickens. C. perfringens Infection was associated with spatial and temporal decreases in mononuclear phagocytes and CD4+ αβ T cells. However, rL. Lactis pre-treatment and subsequent C. perfringens infection led to a significant increase in mononuclear phagocytes, CD8α + γδ T, αβ T cells (CD4+ and CD8α+) and B cells (IgM+, IgA+ and IgY+), as well as IL-12p40, IFN-γ and CD40. Differential expression of interleukin (IL)-6, IL-8, IL-10, IL-13, IL-18, IL-22, and transforming growth factor (TGF)-β were observed in L. lactis treated chickens when compared to C. perfringens infected chickens. Microbiota analysis in C. perfringens infected chickens demonstrated an increase in abundance of Bacillota, Bacteroidota, Pseudomonadota and Actinomycetota. These findings suggests that modulation of the chicken intestinal immune system by L. lactis confers partial protection 30 against NE.

Microencapsulated Sodium Butyrate Alleviates Immune Injury and Intestinal Problems Caused by Clostridium Perfringens through Gut Microbiota

Microencapsulated sodium butyrate (MS-SB) is an effective sodium butyrate additive which can reduce the release of sodium butyrate (SB) in the fore gastrointestinal tract. In this study, we assess the protective effects and mechanisms of MS-SB in Clostridium perfringens (C. perfringens)-challenged broilers. Broiler chickens were pre-treated with SB or MS-SB for 56 days and then challenged with C. perfringens three times. Our results indicate that the addition of MS-SB or SB before C. perfringens infection significantly decreased the thymus index (p < 0.05). Serum IgA, IgY, and IgM concentrations were significantly increased (p < 0.05), while pro-inflammatory IL-1β, IL-6, and TNF-α were significantly decreased (p < 0.05) under MS-SB or SB supplementation. Compared with SB, MS-SB presented a stronger performance, with higher IgA content, as well as a lower IL-1β level when normal or C. perfringens-challenged. While C. perfringens challenge significantly decreased the villus height (p < 0.05), MS-SB or SB administration significantly increased the villus height and villus height/crypt depth (V/C ratio) (p < 0.05). Varying degrees of SB or MS-SB increased the concentrations of volatile fatty acids (VFAs) during C. perfringens challenge, where MS-SB presented a stronger performance, as evidenced by the higher content of isovaleric acid and valeric acid. Microbial analysis demonstrated that both SB or MS-SB addition and C. perfringens infection increase variation in the microbiota community. The results also indicate that the proportions of Bacteroides, Faecalibacterium, Clostridia, Ruminococcaceae, Alistipes, and Clostridia were significantly higher in the MS-SB addition group while, at same time, C. perfringens infection increased the abundance of Bacteroides and Alistipes. In summary, dietary supplementation with SB or MS-SB improves the immune status and morphology of intestinal villi, increases the production of VFAs, and modulates cecal microbiota in chickens challenged with C. perfringens. Moreover, MS-SB was more effective than SB with the same supplemental amount.

Dietary methionine sources and levels modulate the intestinal health status of broiler chickens

Given the key role of methionine in biological processes, adequate methionine should be provided to meet the nutritional requirements. DL-2-hydroxy-4-(methylthio)-butanoic acid (DL-HMTBA) has been considered as an important source of methionine. However, the effects of different sources and levels of methionine on the intestinal health status have not been clarified yet. An experiment was carried out to investigate the effects of different dietary sources and levels of methionine on the intestinal epithelial barrier, inflammatory cytokines expression, ileal morphology, microbiota composition, and cecal short chain fatty acids (SCFA) profiles. For this purpose, 720 male Arbor Acre broiler chicks at 1 d old were randomly assigned to a 2 × 3 factorial arrangement with 2 methionine sources (DL-methionine and DL-HMTBA) and 3 total sulfur amino acids (TSAA) levels (80%, 100%, and 120% of Arbor Acre recommendation). The results showed that DL-HMTBA supplementation promoted intestinal physical barrier at both gene expression level of claudin-1 and serum diamine oxidase level (P < 0.05), and the inflammatory cytokine IL-6 mRNA expression was down-regulated by dietary DL-HMTBA supplementation compared with the DL-methionine group (P < 0.05). Meanwhile, an upregulated gene expression of claudin-1 and zonula occluden-1 (ZO-1) were observed in the low-TSAA treatment on d 14 (P < 0.05), whereas this treatment increased the expression of IL-1β and IL-6 (P < 0.05). Villus height to crypt depth ratio was high (P < 0.05) in the middle-level TSAA group. Furthermore, DL-HMTBA supplementation optimized the microbiota of the ileum especially the relative abundance of Lactobacillus, where the digestion and absorption were completed, and elevated the concentrations of SCFA (acetate, propionate, and butyrate) in the cecal content on d 21 (P < 0.01). In conclusion, dietary DL-HMTBA supplementation improved the intestinal barrier function, immune homeostasis and optimized the microbiota to promote intestinal health status in broiler chickens.

The potential immunomodulatory role of the gut microbiota in the pathogenesis of asthma: an in vitro study

The aim of this study was to investigate the influence of Bacteroides vulgatus (BV), Clostridium perfringens (CP), Parabacteroides distasonis (PD) and Ruminococcus albus (RA) lysates on secretion of selected cytokines by PBMC, MDM and HT-29 cells, as well as to determine the potential mechanisms of their action in the development of asthma. Enzyme-linked immunosorbent assays were used to analyze the effect of BV, CP, PD and RA lysates on the secretion of IL-1β, IL-6, IL-10 and TNF-α by human PBMC, MDM and HT-29 cells. BV and CP lysates significantly lowered IL-1β secretion by MDM vs. control (p < 0.05 and p < 0.001 respectively) but only at a dose of 400 µg lysate. The secretions of IL-6 by PBMC and MDM were elevated significantly above control values (p < 0.05) after administration of CP and PD lysates. BV, CP and PD lysates (100 µg) significantly increased IL-10 secretion by PBMC vs. control (p < 0.05). CP, PD and RA lysates (400 µg) significantly increased IL-10 secretion by MDM vs. control (p < 0.001). BV lysate (400 µg) also significantly increased IL-10 secretion by MDM as compared to control (p < 0.05). In PBMC and MDM, the production levels of the anti-inflammatory cytokine were increased by all the bacterial lysates used in a dose-dependent manner.

Molecular and cellular characterization of immunity conferred by lactobacilli against necrotic enteritis in chickens

Necrotic enteritis is an important enteric disease of poultry that can be controlled with in-feed antibiotics. However, with the concerns over antimicrobial resistance, there is an increased interest in the use of alternatives. Probiotics are one of the alternatives that have gained considerable attention due to their antimicrobial and immunomodulatory activities. Therefore, in the present study, we evaluated the effects of two different Lactobacillus species alone or as a cocktail on prevention of necrotic enteritis. Day-old male broiler chickens were divided into five groups and on days 1, 8, 15, and 22, birds in groups 2 and 3 received 1×108 colony forming units (CFU) of L. johnsonii and L. reuteri, respectively. Group 4 received probiotic cocktails containing both bacteria (108 CFU/bird) and the negative and positive control groups did not receive any lactobacilli. Starting on day 23 post-hatch, birds in all groups (except the negative control group) were orally challenged twice per day with 3×108 CFU of a pathogenic C. perfringens strain for 3 days. Tissue and cecal samples were collected before and after challenge to assess gene expression, lymphocyte subsets determination, and microbiome analysis. On day 26 of age, lesion scoring was performed. The results demonstrated that the group that received the lactobacilli cocktail had significantly reduced lesion scores compared to the positive control group. In addition, the expression of interleukin (IL)-12 in the jejunum and CXC motif chemokine ligand 8 (CXCL8), IL-13, and IL-17 in the ileum were downregulated in the group that received the lactobacilli cocktail when compared to the positive control. Treating chickens with the lactobacilli cocktail prior to challenge enhanced the percentage of CD3-CD8+ cells and Bu-1+IgY+ B cells in the ileum and increased the frequency of monocyte/macrophages, CD3-CD8+ cells, Bu-1+IgM+, and Bu-1+IgY+ B cells in the jejunum. Treatment with the lactobacilli cocktail reduced the relative expression of Gamma-Protobacteria and Firmicutes compared to the positive control group. In conclusion, the results presented here suggest that treatment with the lactobacilli cocktail containing L. johnsonii and L. reuteri reduced necrotic enteritis lesions in the small intestine of chickens, possibly through the modulation of immune responses.

Effects of Eimeria maxima infection doses on growth performance and gut health in dual-infection model of necrotic enteritis in broiler chickens

The objective of this study was to investigate the effects of the different doses of Eimeria maxima (EM) oocysts on growth performance and intestinal health in broiler chickens challenged with a dual infection model of necrotic enteritis (NE) using EM and NetB+ Clostridium perfringens (CP). A total of 432 fourteen-d-old male Cobb 500 broiler chickens were divided into 6 groups with 6 replicates each. The six different groups were as follows: Control, non-challenged; T0+, challenged with CP at 1 × 109 colony forming unit; T5K+, T0+ + 5,000 EM oocysts; T10K+, T0+ + 10,000 EM oocysts; T20K+; T0+ + 20,000 EM oocysts; and T40K+; T0+ + 40,000 EM oocysts. The challenge groups were orally inoculated with EM strain 41A on d 14, followed by NetB+ CP strain Del-1 on 4 days post inoculation (dpi). Increasing EM oocysts decreased d 21 body weight, body weight gain, feed intake (linear and quadratic, p < 0.001), and feed efficiency (linear, p < 0.001) from 0 to 7 dpi. Increasing EM oocysts increased jejunal NE lesion score and intestinal permeability on 5, 6, and 7 dpi (linear, p < 0.05). On 7 dpi, increasing the infection doses of EM oocysts increased jejunal CP colony counts (linear, p < 0.05) and increased fecal EM oocyst output (linear and quadratic, p < 0.001). Furthermore, increasing the infection doses of EM oocysts decreased the villus height to crypt depth ratios and the goblet cell counts (linear, p < 0.05) on 6 dpi. Increasing EM oocysts downregulated the expression of MUC2, B0AT, B0,+AT, PepT1, GLUT2, AvBD3 and 9, LEAP2, and TLR4, while upregulating CLDN1, CATHL3, IL-1β, IFN-γ, TNFSF15, TNF-α, IL-10, and Gam56 and 82 on 6 dpi (linear, p < 0.05). Additionally, increasing EM oocysts decreased Pielou's evenness and Shannon's entropy (linear, p < 0.01). In conclusion, increasing the infection doses of EM significantly aggravated the severity of NE and exerted negative impact on intestinal health from 5 to 7 dpi.

Effects of Tannic Acid Supplementation on the Intestinal Health, Immunity, and Antioxidant Function of Broilers Challenged with Necrotic Enteritis

Clostridium perfringens causes necrotic enteritis (NE) after proliferation in the intestine of poultry, resulting in considerable losses to the poultry industry. This study aimed to investigate the impact of tannic acid on the antioxidant, immunity, and gut health of broilers with NE. In the experiment, 630 one-day-old Cobb500 male chicks were randomly divided into six treatment groups, with seven replicate cages and with fifteen birds in each cage. The treatment groups were as follows: control group (NC), challenged group (PC), and challenged NE chickens treated with 250, 500, 750, and 1000 mg/kg tannic acid (PTA1, PTA2, PTA3, and PTA4, respectively). To induce NE, coccidia vaccine and Clostridium perfringens were administered on day 19 and days 22-28, respectively. Indexes related to antioxidant, immune, and intestinal health were measured on days 28 and 35. During the infection period, we observed significant increases in fecal water content, D-LA, TNF-α, and malondialdehyde concentrations (p < 0.05). Conversely, significant decreases were noted in chyme pH and in T-AOC, IL-4, and IL-10 concentrations (p < 0.05). The addition of tannic acid exhibited a linear decrease in fecal water content and TNF-α concentration (p < 0.05). Furthermore, tannic acid supplementation resulted in a quadratic curve decrease in D-LA concentration and linear increases in T-AOC, IL-4, and IL-10 (p < 0.05). Cecal microbiological analysis revealed that Ruminococcaceae and Butyricimona were dominant in PTA3. In conclusion, the dietary addition of tannic acid may reduce the negative effects of NE by increasing antioxidant and anti-inflammatory capacity, improving the intestinal barrier, and regulating the intestinal flora.

Cellular Immune Responses in Lymphoid Tissues of Broiler Chickens Experimentally Infected with Necrotic Enteritis-Producing Clostridium perfringens Strains

Host cellular responses against Clostridium perfringens (CP), the causative agent of necrotic enteritis (NE) in chickens, are poorly understood. In the present study, we first tested the NE-producing ability of seven netB+ CP strains (CP5, CP18, CP26, CP64, CP67, CP68, and NCNE-1), using an experimental infection model of broiler chickens. Evaluation of intestinal gross lesions showed that all the strains, except CP5, were able to produce NE, while CP26 and CP64 strains produced relatively more severe lesions when compared with other groups. Next, cellular responses in the cecal tonsil (CT), bursa of Fabricius, and spleen were evaluated in chickens infected with strains representing variation in the level of virulence, namely, avirulent CP5, virulent CP18, and a relatively more virulent CP26 strain. Immunophenotyping analysis showed that CT or splenic macrophage frequencies were significantly higher in CP18- and CP26-infected chickens compared with uninfected controls, while the frequencies of γδ T-cells and B-cells in the CT of CP26-infected chickens were significantly higher than those in the uninfected, CP5- or CP18-infected groups. The T-cell analysis showed that chickens infected with CP18 and CP26 had a significantly higher number of splenic CD4+ and CD8+ T-cells expressing CD44 and CD28 activation molecules, while CP26-infected chickens also had significantly increased CT frequency of these activated CD4+ and CD8+ T-cells when compared with uninfected or CP5-infected groups. Collectively, our findings suggested that cellular responses, including activation of T-cells, are selectively induced against virulent CP strains and that the NE-producing characteristics of this pathogen may influence the outcome of immunity to NE.

Osteoimmunology: A Link between Gastrointestinal Diseases and Skeletal Health in Chickens

Bone serves as a multifunctional organ in avian species, giving structural integrity to the body, aiding locomotion and flight, regulating mineral homeostasis, and supplementing calcium for eggshell formation. Furthermore, immune cells originate and reside in the bone marrow, sharing a milieu with bone cells, indicating a potential interaction in functions. In avian species, the prevalence of gastrointestinal diseases can alter the growth and the immune response, which costs a great fortune to the poultry industry. Previous studies have shown that coccidiosis and necrotic enteritis can dramatically reduce bone quality as well. However, possible mechanisms on how bone quality is influenced by these disease conditions have not yet been completely understood, other than the reduced feed intake. On the other hand, several mediators of the immune response, such as chemokines and cytokines, play a vital role in the differentiation and activation of osteoclasts responsible for bone resorption and osteoblasts for bone formation. In the case of Eimeria spp./Clostridium perfringens coinfection, these mediators are upregulated. One possible mechanism for accelerated bone loss after gastrointestinal illnesses might be immune-mediated osteoclastogenesis via cytokines-RANKL-mediated pathways. This review article thus focuses on osteoimmunological pathways and the interaction between host immune responses and bone biology in gastrointestinal diseases like coccidiosis and necrotic enteritis affecting skeletal health.

Effects of Vitamin A on Immune Responses and Vitamin A Metabolism in Broiler Chickens Challenged with Necrotic Enteritis

Necrotic enteritis (NE) is an important enteric inflammatory disease of poultry, and the effects of vitamin A (VitA) on NE birds are largely unknown. The present study was conducted to investigate the effects of VitA on the immune responses and VitA metabolism of NE broilers as well as the underlying mechanisms. Using a 2 × 2 factorial arrangement, 336 1-day-old Ross 308 broiler chicks were randomly assigned to 4 groups with 7 replicates. Broilers in the control (Ctrl) group were fed a basal diet without extra VitA supplementation. Broilers in the VitA group were fed a basal diet supplemented with 12,000 IU/kg of VitA. Birds in NE and VitA + NE groups were fed corresponding diets and, in addition, co-infected with Eimeria spp. and Clostridium perfringens on days 14 to 20. Samples of the blood, jejunum, spleen and liver were obtained on day 28 for analysis, and meanwhile, lesion scores were also recorded. The results showed that NE challenge increased lesion score in the jejunum and decreased serum glucose, total glyceride, calcium, phosphorus and uric acid levels (p < 0.05). VitA supplementation reduced the levels of serum phosphorus, uric acid and alkaline phosphatase in NE-challenged birds and increased serum low-density lipoprotein content and the activity of aspartate aminotransferase and creatine kinase (p < 0.05). Compared with the Ctrl group, the VitA and NE groups had higher mRNA expression of interferon-γ in the jejunum (p < 0.05). NE challenge up-regulated mRNA expression of interleukin (IL)-13, transforming growth factor-β4, aldehyde dehydrogenase (RALDH)-2 and RALDH-3 in the jejunum, while VitA supplementation increased jejunal IL-13 mRNA expression and hepatic VitA content, but down-regulated splenic IL-13 mRNA expression (p < 0.05). The VitA + NE group had higher serum prostaglandin E₂ levels and the Ctrl group had higher splenic RALDH-3 mRNA expression than that of the other three groups (p < 0.05). NE challenge up-regulated jejunal retinoic acid receptor (RAR)-β and retinoid X receptor (RXR)-α as well as splenic RAR-α and RAR-β mRNA expression (p < 0.05). VitA supplementation up-regulated jejunal RAR-β expression but down-regulated mRNA expression of RXR-α, RXR-γ, signal transducers and activators of transcription (STAT) 5 and STAT6 in the spleen (p < 0.05). Moreover, compared with the Ctrl group, the VitA and NE groups had down-regulated mRNA expression of jejunal and splenic Janus kinase (JAK) 1 (p < 0.05). In conclusion, NE challenge induced jejunal injury and expression of Th2 and Treg cell-related cytokines and enhanced RALDH and RAR/RXR mRNA expression, mainly in the jejunum of broilers. VitA supplementation did not alleviate jejunal injury or Th2 cell-related cytokine expression; however, it improved hepatic VitA deposition and inhibited the expression of RALDH-3, RXR and the JAK/STAT signaling pathway in the spleen of broilers. In short, the present study suggested the modulatory effects of vitamin A on the immune responses and vitamin A metabolism in broiler chickens challenged with necrotic enteritis.

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.

Mucosal and systemic lymphoid immune responses against Clostridium perfringens strains with variable virulence in the production of necrotic enteritis in broiler chickens

Necrotic enteritis (NE), caused by Clostridium perfringens, is an economically important disease of chickens. Although NE pathogenesis is moderately well studied, the host immune responses against C. perfringens are poorly understood. The present study used an experimental NE model to characterize lymphoid immune responses in the caecal tonsils (CT), bursa of Fabricius, Harderian gland (HG) and spleen tissues of broiler chickens infected with four netB+ C. perfringens strains (CP1, CP5, CP18, and CP26), of which CP18 and CP26 strains also carried the tpeL gene. The gross and histopathological lesions in chickens revealed CP5 to be avirulent, while CP1, CP18, and CP26 strains were virulent with CP26 being "very virulent". Gene expression analysis showed that, while the virulent strains induced a significantly upregulated expression of pro-inflammatory IL-1β gene in CT, the CP26-infected birds had significantly higher CT transcription of IFNγ and IL-6 pro-inflammatory genes compared to CP5-infected or uninfected chickens. Furthermore, CP26 infection also led to significantly increased bursal and HG expression of the anti-inflammatory/regulatory genes, IL-10 or TGFβ, compared to control, CP5 and CP1 groups. Additionally, the splenic pro- and anti-inflammatory transcriptional changes were observed only in the CP26-infected chickens. An antibody-mediated response, as characterized by increased IL-4 and/or IL-13 transcription and elevated IgM levels in birds infected with virulent strains, particularly in the CP26-infected group compared to uninfected controls, was also evident. Collectively, our findings suggest that lymphoid immune responses during NE in chickens are spatially regulated such that the inflammatory responses against C. perfringens depend on the virulence of the strain.

Intracloacal Inoculation of Broiler Chickens with Clostridium perfringens Strains: Evaluation of Necrotic Enteritis Disease Development and Lymphoid Immune Responses

Necrotic enteritis (NE) is an economically important disease of chickens. We have recently shown that inflammatory responses in chickens inoculated orally with virulent Clostridium perfringens were spatially regulated. Here, we used previously virulence-characterized netB+ C. perfringens strains, avirulent CP5 and virulent CP18 and CP26, to assess the severity of NE and immune responses in broiler chickens when inoculated intracloacally. The results showed that CP18- and CP26-infected birds had a reduced weight gain and developed milder/less severe NE lesions, as determined by the gross lesions scores, suggesting a subclinical-grade infection. Gene expression analysis in infected birds revealed three statistically significant observations compared to uninfected-control: (1) Increased expression of anti-inflammatory/immunoregulatory interleukin (IL)-10/transforming growth factor (TGF)β in cecal tonsil (CT) and bursa of Fabricius in the CP18/CP26-infected groups. (2) Increased CT transcription of pro-inflammatory IL-1β, IL-6 and interferon (IFN)γ and decreased Harderian gland (HG) expression of IFNγ in the CP18/CP26-infected birds. (3) Increased HG or bursal expression of IL-4 and IL-13 in CP5-infected birds. Collectively, intracloacal C. perfringens inoculation seems to induce a highly regulated inflammatory response in the CT and other mucosal lymphoid organs and an intracloacal infection model may be useful in evaluating immune responses in chickens with subclinical NE.

Immune Response Evaluation in Commercial Turkeys Affected with Clostridial Dermatitis

Clostridial dermatitis (CD), caused by Clostridium septicum and Clostridium perfringens, is an economically important emerging disease of turkeys characterized by sudden deaths and necrotic dermatitis. Immune responses in CD-affected commercial turkeys are poorly understood. In the present study, C. septicum was isolated from CD-affected commercial turkeys during a recent outbreak, and the tissues (skin, muscle, and spleen) were collected and analyzed for immune gene expression, along with samples from clinically healthy birds. The results showed that CD-affected turkeys had significantly higher levels of IL-1β, IL-6, IFNγ, and iNOS transcripts in the skin, muscle, and spleen tissues compared to healthy birds. Affected turkeys also had a significantly elevated transcription of toll-like receptor (TLR21) gene in the skin and spleen tissues, suggesting a role for this receptor in the immune recognition. The expression of IL-4 and IL-13 genes in the spleen and muscle was also significantly higher in the affected birds. Additional birds from the same affected and healthy farms examined for serology revealed that the CD-affected turkeys had significantly higher levels of serum IgM and IgY antibodies. Furthermore, in vitro stimulation of MQ-NCSU macrophages with C. septicum led to a significant transcriptional upregulation of IL-1β and IFNγ genes, while the IL-10 gene expression was downregulated. The surface expression of MHC-II protein and cellular production of nitric oxide were also significantly increased in the C. septicum-stimulated macrophages, indicating cellular activation. Collectively, our findings suggest that the host responses in CD-affected turkeys involve a robust inflammatory response as well as a response mediated by IL4/IL-13 cytokines that may aid in antibody-mediated immunity.

Glucose oxidase as an alternative to antibiotic growth promoters improves the immunity function, antioxidative status, and cecal microbiota environment in white-feathered broilers

This study aimed to demonstrate the effects of glucose oxidase (GOD) on broilers as a potential antibiotic substitute. A total of four hundred twenty 1-day-old male Cobb500 broilers were randomly assigned into five dietary treatments, each with six replicates (12 chicks per replicate). The treatments included two control groups (a basal diet and a basal diet with 50 mg/kg aureomycin) and three GOD-additive groups involving three different concentrations of GOD. Analysis after the t-test showed that, on day 21, the feed:gain ratio significantly decreased in the 1,200 U/kg GOD-supplied group (GOD1200) compared to the antibiotic group (Ant). The same effect was also observed in GOD1200 during days 22-42 and in the 600 U/kg GOD-supplied group (GOD600) when compared to the control group (Ctr). The serum tests indicated that, on day 21, the TGF-β cytokine was significantly decreased in both GOD600 and GOD1200 when compared with Ctr. A decrease in malondialdehyde and an increase in superoxide dismutase in GOD1200 were observed, which is similar to the effects seen in Ant. On day 42, the D-lactate and glutathione peroxidase activity changed remarkably in GOD1200 and surpassed Ant. Furthermore, GOD upregulated the expression of the jejunal barrier genes (MUC-2 and ZO-1) in two phases relative to Ctr. In the aureomycin-supplied group, the secretory immunoglobulin A significantly decreased in the jejunum at 42 days. Changes in microbial genera were also discovered in the cecum by sequencing 16S rRNA genes at 42 days. The biomarkers for GOD supplementation were identified as Colidextribacter, Oscillibacter, Flavonifractor, Oscillospira, and Shuttleworthia. Except for Shuttleworthia, all the abovementioned genera were n-butyrate producers known for imparting their various benefits to broilers. The PICRUSt prediction of microbial communities revealed 11 pathways that were enriched in both the control and GOD-supplied groups. GOD1200 accounted for an increased number of metabolic pathways, demonstrating their potential in aiding nutrient absorption and digestion. In conclusion, a diet containing GOD can be beneficial to broiler health, particularly at a GOD concentration of 1,200 U/kg. The improved feed conversion ratio, immunity, antioxidative capacity, and intestinal condition demonstrated that GOD could be a valuable alternative to antibiotics in broiler breeding.

Dietary yeast cell wall enhanced intestinal health of broiler chickens by modulating intestinal integrity, immune responses, and microbiota

This study was conducted to determine the effects of dietary yeast cell wall (YCW) on growth performance, intestinal health, and immune responses of broiler chickens. In a randomized completely block design (block: initial body weight), a total of 800 broilers (Ross 308; 45.18 ± 3.13 g of initial body weight) were assigned to 2 dietary treatments (40 birds/pen; 10 replicates/treatment) and fed for 5 wk: 1) a basal broiler diet based on corn-soybean meal (CON) and 2) CON + 0.05% dietary YCW. Growth performance was measured at intervals in 3 phase feed program. On the final day of the study, one bird per pen was randomly selected and euthanized for sample collection. Broilers fed YCW had decreased (P < 0.05) feed conversion ratio during the grower phase compared with those fed CON. The YCW increased (P < 0.05) villus height to crypt depth ratio in the duodenum, jejunum, and ileum compared with the CON. In addition, the YCW tended to higher (P < 0.10) number of goblet cells in the duodenum than in the CON. Broilers fed YCW had increased (P < 0.05) serum TGF- β1, ileal gene expression of the claudin family, and relative abundance of Lactobacillus, Prevotella, and Enterococcus compared with the CON, but decreased serum TNF-α (P < 0.05), IL-1β (P < 0.05), and IL-6 (P < 0.10), ileal gene expression of IL-6 (P < 0.05), and relative abundance of Clostridium (P < 0.05). The present study demonstrated that the addition of dietary YCW in broiler diets enhanced the intestinal health of broiler chickens and may be associated with modulated intestinal morphology and integrity by upregulating tight junction-related protein gene expression and modifying the ileal microbiota. In addition, dietary YCW modulated immune responses and inflammatory cytokine gene expression in the ileum.

Evolution of developmental and comparative immunology in poultry: The regulators and the regulated

Avian has a unique immune system that evolved in response to environmental pressures in all aspects of innate and adaptive immune responses, including localized and circulating lymphocytes, diversity of immunoglobulin repertoire, and various cytokines and chemokines. All of these attributes make birds an indispensable vertebrate model for studying the fundamental immunological concepts and comparative immunology. However, research on the immune system in birds lags far behind that of humans, mice, and other agricultural animal species, and limited immune tools have hindered the adequate application of birds as disease models for mammalian systems. An in-depth understanding of the avian immune system relies on the detailed studies of various regulated and regulatory mediators, such as cell surface antigens, cytokines, and chemokines. Here, we review current knowledge centered on the roles of avian cell surface antigens, cytokines, chemokines, and beyond. Moreover, we provide an update on recent progress in this rapidly developing field of study with respect to the availability of immune reagents that will facilitate the study of regulatory and regulated components of poultry immunity. The new information on avian immunity and available immune tools will benefit avian researchers and evolutionary biologists in conducting fundamental and applied research.

Effects of Treatment with Lactobacilli on Necrotic Enteritis in Broiler Chickens

Growth promoter antibiotics have been commonly used for the control of necrotic enteritis (NE) in broilers for decades. However, due to a ban on the use of these antibiotics, alternatives such as probiotics have been tested widely for NE control. The present study tested the efficacy of four different species of lactobacilli (two isolates of Lactobacillus johnsonii and one of Ligilactobacillus (L.) salivarius, Limosilactobacillus (L.) reuteri, and L. crispatus) against NE. Day-old male broiler chickens were divided into six groups and orally inoculated with 1 × 10⁷ or 1 × 10⁸ colony-forming units (CFU) of lactobacilli on 1, 7, 14, and 20 days of age. While negative and positive control groups did not receive lactobacilli, the latter was challenged with Clostridium perfringens (CP). Chickens, at 21 days old, were challenged for 3 days with 3 × 10⁸ CFU of a virulent strain of CP. Tissues were collected for immune system gene expression, immunophenotyping, intestinal histomorphometry, and microbiota analysis. Lactobacilli inoculation conferred partial protection in chickens against NE, marked by lowered lesion scores and improved villus:crypt ratio. Immunomodulatory effects were demonstrated by the significant alteration of interferon (IFN)-γ, interleukin (IL)-1β, IL-2, IL-12p35, IL-17, and transforming growth factor beta (TGF-β) gene transcription in the duodenum and jejunum as well as subtle changes in the frequency of CD8 + T cells and B cells in the cecal tonsil of the treated chickens. Microbiota analysis showed increased levels of some bacterial phyla including Actinobacteria, Lactobacillaceae, and Firmicutes. In conclusion, these findings suggest that the use of certain lactobacilli can reduce NE severity and modulate immune responses and intestinal microbiota composition in chickens.

The Effect of Necrotic Enteritis Challenge on Production Performance, Cecal Microbiome, and Cecal Tonsil Transcriptome in Broilers

The objective of this study was to identify the effects of experimental necrotic enteritis (NE) infection on the production performance, gut microbiome, and cecal tonsil transcriptome in broiler birds. A total of 192 chicks were not-induced (control) or induced with NE. NE was induced by inoculating Eimeria maxima at 14 d of age and Clostridium perfringens at 19, 20, and 21 d of age. NE challenge increased (p < 0.01) NE lesion score at 7 days post-E.maxima infection (dpi), decreased (p < 0.01) average weight gain and increased (p < 0.01) mortality at 7 and 14 dpi. NE challenge increased (p < 0.05) gut permeability at 5, 6, and 7 dpi and increased ileal C. perfringens load at 5 dpi. NE challenge increased (p < 0.01) Eimeria oocyst shedding at 5, 6, 7, 8 and 14 dpi. NE challenge decreased (p < 0.05) the relative abundance of Lactobacillaceae and increased (p < 0.05) the relative abundance of Campylobacteriaceae, Comamonadaceae, and Ruminococcaceae at 6 dpi. NE challenge upregulated (p < 0.05) genes related to immune response and downregulated (p < 0.05) genes related to lipid metabolism at 6 dpi. It can be concluded that NE infection decreased beneficial bacteria and increased gut permeability.

Evaluation of Predisposing Factors of Necrotic Enteritis in Experimentally Challenged Broiler Chickens

Simple Summary

The ban of antibiotic growth promoters in animal feed increased the number of cases of necrotic enteritis (NE) in broilers, greatly affecting the poultry industry. The induction of experimental NE faces challenges, as it is a multifactorial disease and the pathogenesis is not fully understood, hampering the development of in vivo studies for disease control and prevention strategies. The literature reports several protocols using different factors to assist in NE induction. This study assessed predisposing factors, such as immunosuppression, infection or both, by Eimeria spp. in broilers (n = 99) fed a wheat-based diet and challenged with three different strains of Clostridium perfringens (CP). Under microscopy, Eimeria spp. had a negative effect on intestinal morphometry and favored the increase of intraepithelial lymphocytes. However, the macroscopic analysis did not show which factor was more effective in potentiating the lesions, suggesting a synergistic effect between the strain of CP used and the predisposing factors. Therefore, each experimental protocol should first be evaluated for the association of the CP strain with the predisposing factors.

Abstract

Clostridium perfringens is the etiological agent of NE, a disease that greatly affects the poultry industry. Experiments on the induction of NE are difficult to carry out, as it is a multifactorial disease, and thus different predisposing factors have been used. This study evaluated the effect of the Gumboro disease vaccine virus vaccine (IBDV-vac) associated or not with infection by Eimeria spp. in broilers, as a predisposing factor for NE. Broilers (n = 99) were divided into groups (11) challenged with IBDV-vac, Eimeria spp. CP type G (CP13, CP14 and CP03) or both. The macroscopic evaluation revealed that the highest average (3.45) of injury occurred for the CP13 + IBDV-vac group. The microscopic analysis showed that Eimeria spp. increased the population of intraepithelial lymphocytes and reduced the villus/crypt ratio in duodenum and jejunum when associated with CP13 or CP14. There was a synergistic effect between the CP strain used and the predisposing factors; nevertheless, it was not clear which was the most effective predisposing factor to potentiate the lesions, suggesting that the association of the strain with the factors should first be evaluated for each experimental protocol.

Immunological characterization of chicken tumor necrosis factor-α (TNF-α) using new sets of monoclonal antibodies specific for poultry TNF-α

Tumor necrosis factor-α (TNF-α) is a type II transmembrane protein with either membrane-bound or soluble forms and is a prototypical member of the TNF superfamily. TNF-α is a pleiotropic cytokine associated with the regulation of systemic inflammation and host defense. Chicken TNF-α (chTNF-α) is a long-missed avian ortholog, and its immunological properties remain largely unknown compared to those of its mammalian counterparts. Here, we report the functional characterization and immunomodulatory properties of chTNF-α using a panel of newly developed anti-chTNF-α mouse monoclonal antibodies (mAbs). Using anti-chTNF-α mAbs, we determined the tissue expression of chTNF-α in lymphoid and non-lymphoid organs. A chTNF-α-specific antigen-capture sandwich ELISA was developed using compatible mAb partners by screening and validation of ten different mAbs. Employing 3G11 and 12G6 as capture and detection antibodies, respectively, the levels of native chTNF-α in the circulation of Clostridium perfringens, Eimeria, or dual C. perfringens/Eimeria-infected chickens were determined. Furthermore, intracellular expression of chTNF-α in primary immune cells or cell lines derived from chickens was validated by immunocytochemistry and flow cytometry assays using both 3G11 and 12G6 mAbs. Notably, both 3G11 and 12G6 neutralized chTNF-α-induced nitric oxide production in chicken HD11 cells in vitro. Collectively, our results enhance our understanding of the functional characteristics of chTNF-α, and these anti-chTNF-α mAbs will serve as valuable immune reagents to inform on inflammatory responses and disease pathogenesis in the fundamental and applied studies of avian species.

Clostridium perfringens-Induced Necrotic Diseases: An Overview

Clostridium perfringens, a prevalent Gram-positive bacterium, causes necrotic diseases associated with abundant life loss and economic burdens of billions of USD. The mechanism of C. perfringens-induced necrotic diseases remains largely unknown, in part, because of the lack of effective animal models and the presence of a large array of exotoxins and diverse disease manifestations from the skin and deep tissues to the gastrointestinal tract. In the light of the advancement of medical and veterinary research, a large body of knowledge is accumulating on the factors influencing C. perfringens-induced necrotic disease onset, development, and outcomes. Here, we present an overview of the key virulence factors of C. perfringens exotoxins. Subsequently, we focus on comprehensively reviewing C. perfringens-induced necrotic diseases such as myonecrosis, acute watery diarrhea, enteritis necroticans, preterm infant necrotizing enterocolitis, and chicken necrotic enteritis. We then review the current understanding on the mechanisms of myonecrosis and enteritis in relation to the immune system and intestinal microbiome. Based on these discussions, we then review current preventions and treatments of the necrotic diseases and propose potential new intervention options. The purpose of this review is to provide an updated and comprehensive knowledge on the role of the host–microbe interaction to develop new interventions against C. perfringens-induced necrotic diseases.

Ex Vivo Differential Responsiveness to Clostridium perfringens and Lactococcus lactis by Avian Small Intestine Macrophages and T Cells

Tissue resident immune system cells in the chicken intestine play a significant role in the protection against pathogens. However, very little is known about these cells. The current study was conducted to further characterize chicken intestinal immune system cells. Furthermore, this study aimed to assess the immune modulatory action of a highly virulent Clostridium perfringens, a commonly found chicken intestinal microbe, in comparison with a non-commensal, Lactococcus lactis, on intestine-derived immune system cells. The results demonstrated varying distribution of innate and adaptive immune cells along the avian gut-associated lymphoid tissue (GALT) in the duodenum, jejunum, ileum, and cecal tonsils. In addition, steady-state and tissue-specific presence of CD25+ cells among αβ and γδ T-cell subsets was assessed along the intestine. Ex vivo stimulation with C. perfringens or L. lactis resulted in a significant increase in the frequency of CD25+ T cells (γδ and αβ T cells). In addition, significantly more cell death was observed in ex vivo stimulation with C. perfringens, which was indirectly correlated with a decrease in macrophage activation based on nitric oxide (NO) production with no effect on lymphoid cell responsiveness as per intracellular interferon (IFN)-gamma (γ) staining. Ex vivo stimulation with L. lactis activated γδ T cells and αβ T cells, based on intracellular IFN-γ staining, while it had limited effect on macrophages. However, the ability of γδ and αβ T cells to produce IFN-γ and the ability of macrophages production of NO was rescued in the presence of L. lactis. These results demonstrate the potential application of L. lactis, as a probiotic, against virulent C. perfringens infection in chicken.

Antimicrobial activity of sophorolipids against Eimeria maxima and Clostridium perfringens, and their effect on growth performance and gut health in necrotic enteritis

The in vitro antimicrobial activity of sophorolipids (SLs) against Eimeria maxima and Clostridium perfringens, and the in vivo effects of SLs on growth performance and gut health in necrotic enteritis (NE)-afflicted broiler chickens were studied. To test the direct killing effects of SLs on enteric pathogens, 2.5 × 105 freshly prepared sporozoites of each Eimeria acervulina, E. maxima, and E. tenella were placed in each well of a 96-well plate, and the vegetative stage of Clostridium perfringens was prepared at 1 × 109 cfu/well. Four different SLs (C18:1 lactonic diacetyled SL [SL1], C18:1 deacetyled SL [SL2], C18:1 monoacetyled SL [SL3], and C18:1 diacetyled SL [SL4]), and 2 anticoccidial chemical controls, decoquinate and monensin, were evaluated at 3 dose levels (125 µg/mL, 250 µg/mL, and 500 µg/mL). Samples were incubated at 41°C for 3 h, and microbial survival ratios were measured by using a cell counter to quantify the number of live microbes stained by fluorescent dye. A total of 336 (0-day-old) male commercial broiler chickens were used to assess the effects of SLs in vivo. Chickens were randomly allocated to 6 treatment groups (7 chickens per cage, 8 cages per treatment) as follows: a control group which received a basal diet (CON), a negative control group (NC) which received a basal diet and NE challenge, and 4 SL treatment groups with NE (NC+SL1, NC+SL2, NC+SL3, and NC+SL4). The inclusion rates of SLs in each group were 200 mg/kg of feed. NE-induced chickens were orally infected with E. maxima (10,000 oocysts/chicken) on d 14, followed by C. perfringens (1 × 109 cfu/chicken) on d 19. Disease parameters measured included gut lesion scores, intestinal cytokine production, and level of tight junction protein expression. Data were analyzed using a Mixed Model (PROC MIXED) in SAS. In vitro (Experiment 1), all SLs dose-dependently decreased (P < 0.001) the viability of the three species of Eimeria sporozoites and C. perfringens. In vivo (Experiment 2), dietary SLs increased (P < 0.001) body weight and average daily gain of broiler chickens infected with NE. Dietary SL1 and SL4s increased (P < 0.05) feed conversion ratio compared to NC. Furthermore, SL1 and SL4 decreased (P < 0.05) gut lesion scores in combination with increased expression of IL1β, IL8, TNFSF15, and IL10 genes (P < 0.05) in NE-afflicted chickens. Overall, dietary SLs promoted growth performance, intestinal immune responses, and intestinal barrier integrity of NE-afflicted, young broiler chickens.

In Vivo Recovery of Bacteriophages and Their Effects on Clostridium perfringens-Infected Broiler Chickens

The objectives of this study were to recover bacteriophages (BPs) from the intestinal digesta of BP-fed broilers and to evaluate the antibacterial effects of encapsulated or powdered BPs in broiler chickens challenged with Clostridium perfringens. Day-old broiler chicks (n = 320/experiment) were randomly assigned to 32 pens (n = 10 broilers/pen) and allocated to one of four dietary groups: (1) unchallenged group (NEG); (2) C. perfringens-challenged group (POS); (3) POS group fed a diet supplemented with powdered BPs; and (4) POS group fed a diet supplemented with encapsulated BPs. On days 21, 22, and 23 post-hatch, all chickens except NEG were orally inoculated twice a day with 2 mL C. perfringens (1.0 × 10⁸ cfu/mL). Varying BP levels were detected in gut digesta at all ages and were numerically or significantly higher in the encapsulated BP group than in the powdered BP group. Dietary powder or encapsulated BPs reversed the C. perfringens-mediated increase in crypt depth. In addition, villus height to crypt depth ratio was elevated in the NEG and BP-treated/challenged groups compared with that in the POS group. C. perfringens counts in the cecum were significantly lower in the BP-fed chickens than in the POS group. The encapsulated BP-supplemented diet-fed chickens had the highest serum IgA levels. Collectively, our results suggest that dietary BP remains viable in intestinal digesta upon ingestion and can inhibit cecal C. perfringens counts.

Necrotic enteritis in chickens: a review of pathogenesis, immune responses and prevention, focusing on probiotics and vaccination

Necrotic enteritis (NE), caused by Clostridium perfringens (CP), is one of the most common of poultry diseases, causing huge economic losses to the poultry industry. This review provides an overview of the pathogenesis of NE in chickens and of the interaction of CP with the host immune system. The roles of management, nutrition, probiotics, and vaccination in reducing the incidence and severity of NE in poultry flocks are also discussed.

Avian Macrophage Responses to Virulent and Avirulent Clostridium perfringens

The present study evaluated the avian macrophage responses against Clostridium perfringens that varied in their ability to cause necrotic enteritis in chickens. Strains CP5 (avirulent-netB+), CP1 (virulent-netB+), and CP26 (highly virulent-netB+tpeL+) were used to evaluate their effect on macrophages (MQ-NCSU cells) and primary splenic and cecal tonsil mononuclear cells. The bacilli (whole cells) or their secretory products from all three strains induced a significant increase in the macrophage transcription of Toll-like receptor (TLR)21, TLR2, interleukin (IL)-1β, inducible nitric oxide synthase (iNOS), and CD80 genes as well as their nitric oxide (NO) production and major histocompatibility complex (MHC)-II surface expression compared to an unstimulated control. The CP1 and CP26-induced expression of interferon (IFN)γ, IL-6, CD40 genes, MHC-II upregulation, and NO production was significantly higher than that of CP5 and control groups. Furthermore, splenocytes and cecal tonsillocytes stimulated with bacilli or secretory products from all the strains showed a significant increase in the frequency of macrophages, their surface expression of MHC-II and NO production, while CP26-induced responses were significantly higher for the rest of the groups. In summary, macrophage interaction with C. perfringens can lead to cellular activation and, the ability of this pathogen to induce macrophage responses may depend on its level of virulence.

Relationship between Mucosal Barrier Function of the Oviduct and Intestine in the Productivity of Laying Hens

The mucosa of the intestine and oviduct of hens are susceptible to pathogens. Pathogenic infections in the mucosal tissues of laying hens lead to worsened health of the host animal, decreased egg production, and bacterial contamination of eggs. Therefore, better understanding of the mechanisms underlying mucosal barrier function is needed to prevent infection by pathogens. In addition, pathogen infection in the mucosal tissue generally causes mucosal inflammation. Recently, it has been shown that inflammation in the oviduct and intestinal tissue caused by disruption of the mucosal barrier function, can affect egg production. Therefore, it is vitla to understand the relationship between mucosal barrier function and egg production to improve poultry egg production. This paper reviews the studies on (1) oviductal mucosal immune function and egg production, (2) intestinal inflammation and egg production, and (3) improvement of mucosal immune function by probiotics. The findings introduced in this review will contribute to the understanding of the mucosal barrier function of the intestine and oviduct and improve poultry egg production in laying hens.

Effects of dietary glucose oxidase on growth performance and intestinal health of AA broilers challenged by Clostridium perfringens

Arbor Acre (AA) broilers were used as the research object to investigate whether glucose oxidase (GOD) has preventive and relieving effects on necrotic enteritis. The experiment was designed as a factorial arrangement of 2 dietary treatments × 2 infection states. Chickens were fed a basal diet or a diet with 150 U/kg GOD, and were challenged with Clostridium perfringens (Cp) or sterile culture medium. In our study, Cp challenge led to intestinal injury, as evidenced by reducing the average daily gain and the average daily feed intake of AA broilers of 14 to 21 d (P < 0.05), increasing the intestinal jejunal lesion score (P < 0.05), reducing the jejunal villi height and villi height/crypt depth (P < 0.05), upregulating the mRNA expression levels jejunal IFN-γ (P < 0.05). The dietary GOD had no significant effects on the growth performance of each growth period, but significantly decreased the ileal pH, increased the height of villi and the ratio of villi height to crypt depth (P < 0.05) and the expression levels of Occludin and Zonula occludens-1 (ZO-1) at d 21. Moreover, dietary GOD and the Cp challenge significantly altered the composition of 21-d ileal microbiota. The Cp challenge decreased the relative abundance of genus Lactobacillus (P = 0.057), and increased the relative abundance of genus Romboutsia (P < 0.05) and genus Veillonella (P = 0.088). The dietary GOD tended to increase the relative abundance of genus Helicobacter (P = 0.066) and decrease the relative abundance of genus Streptococcus (P = 0.071). This study has shown that the supplementation of GOD could promote the integrity of intestinal barrier and the balance of ileal microbiota, but the effects of GOD on NE broilers and its application in actual production need to be further confirmed.

Clostridium perfringens-Induced Host-Pathogen Transcriptional Changes in the Small Intestine of Broiler Chickens

Clostridium perfringens is an important opportunistic pathogen that may result in toxin-mediated diseases involving food poisoning/tissue gangrene in humans and various enterotoxaemia in animal species. It is a main etiological agent for necrotic enteritis (NE), the most financially devastating bacterial disease in broiler chickens, especially if raised under antibiotic-free conditions. Importantly, NE is responsible for losses of six billion US dollars annually in the global poultry industry. To investigate the molecular mechanisms of C. perfringens-induced pathogenesis in the gut and its microbiome mRNA levels in C. perfringens-infected and non-infected hosts, we used RNA sequencing technology to perform transcriptional analysis of both host intestine and microbiome using our NE model. The growth rate was significantly impaired in chickens infected by C. perfringens. In total, 13,473 annotated chicken genes were differentially expressed between these two groups, with ninety-six genes showing statistical significance (|absolute fold changes| > 2.0, adjusted p value < 0.05). Genes involved in energy production, MHC Class I antigen, translation, ribosomal structures, and amino acid, nucleotide and carbohydrate metabolism from infected gut tissues were significantly down-regulated. The upregulated genes were mainly engaged in innate and adaptive immunity, cellular processes, genetic information processing, and organismal systems. Additionally, the transcriptional levels of four crucial foodborne pathogens were significantly elevated in a synergic relationship with pathogenic C. perfringens infection. This study presents the profiling data that would likely be a relevant reference for NE pathogenesis and may provide new insights into the mechanism of host-pathogen interaction in C. perfringens-induced NE infection in broiler chickens.

Clostridium butyricum Supplement Can Ameliorate the Intestinal Barrier Roles in Broiler Chickens Experimentally Infected With Clostridium perfringens

Necrotic enteritis (NE), caused by Clostridium perfringens, is an economically important disease in the broiler. Among normal flora in the broiler intestinal region, Clostridium butyricum has been identified as a probiotic agent that reduces the susceptibility of broilers to C. perfringens. However, the effects of C. butyricum supplement on broiler intestinal integrity during NE are largely unknown. In this study, we investigated the effects of C. butyricum on the growth performance, intestinal morphology and barrier function, and the functions of immune-related cytokines under NE in broilers. Chickens were divided into five groups: control group (NC), supplement C. butyricum only group (CB), NE-infected group (PC), supplement C. butyricum from Day 14 (NECB1) to Day 22 NE-infected group, and supplement C. butyricum from Day 1 (NECB2) to Day 22 NE-infected group. The results showed that there were significantly decreased average daily weight gain and increased feed conversion rate in the infected group (PC) compared with the C. butyricum-supplemented groups (NECB1 and NECB2) through the diet. Histopathological observation on the Hematoxylin–Eosin staining avian small intestine sections revealed that supplementation of C. butyricum (NECB1 and NECB2) could increase the intestinal villus height/crypt depth and lessen the intestinal damage under NE. ELISA and Limulus test showed that broilers infected with NE (PC) had higher serum IgA and lipopolysaccharide content; however, after C. butyricum supplementation (NECB1 and NECB2), they returned to a normal level. Furthermore, real-time PCR and Western blot results indicated that compared with PC, supplementing C. butyricum (NECB1 and NECB2) could initialize the expressions of genes related to the intestinal barrier-associated molecules (such as CLDN-1, CLDN-3, OCLN, MUC2, ZO-1, and CLDN5), cytokines (such as IL-10, IL-6, and TGFB1), and C. perfringens plc gene expression. Moreover, the results detected by the Ussing chamber suggested that C. butyricum (NECB1 and NECB2) could amend the decrease in conductivity value and short-circuit current value caused by NE. In addition, NECB2 significantly reduced the upregulation of fluorescein isothiocyanate–dextran flux caused by the NE disease. In conclusion, these findings suggest that dietary supplementation of C. butyricum in broilers with NE improved chicken growth performance, intestinal integrity and barrier function, and immunological status. Notably, no statistical difference was observed with the addition of C. butyricum on day 1 or day 14.

Bacillus subtilis DSM29784 Alleviates Negative Effects on Growth Performance in Broilers by Improving the Intestinal Health Under Necrotic Enteritis Challenge

Along with banning antibiotics, necrotic enteritis (NE), especially subclinical enteritis (SNE), poses a significant threat to the chicken industry; however, probiotics are a potentially promising intervention. We aimed to investigate the beneficial effects of Bacillus subtilis DSM29784 (BS) on the treatment of Clostridium perfringens (CP)-induced SNE in broilers. A total of 360 1-day-old broiler chicks were divided into three treatment groups, namely control (Ctr), SNE, and BS treatment (BST) groups, all of which were fed with a basal died for 21days, and then from day 22 onward, only the BST group had a BS supplemented diet (1×10⁹ colony-forming units BS/kg). On day 15, all chicks, except the Ctr group, were challenged with a 20-fold dose coccidiosis vaccine and 1ml CP (2×10⁸) on days 18–21 for SNE induction. Beneficial effects were observed on growth performance in BST compared to SNE broilers. BST treatment alleviated intestinal lesions and increased the villus height/crypt depth ratio. Further, BST broilers showed increased maltase activity in the duodenum compared with SNE chicks, and a significantly decreased caspase-3 protein expression in the jejunum mucosa. Moreover, an increased abundance of Ruminococcaceae and Bifidobacterium beneficial gut bacteria and an altered gut metabolome were observed. Taken together, we demonstrate that the manipulation of microbial gut composition using probiotics may be a promising prevention strategy for SNE by improving the composition and metabolism of the intestinal microbiota, intestinal structure, and reducing inflammation and apoptosis. Hence, BS potentially has active ingredients that may be used as antibiotic substitutes and effectively reduces the economic losses caused by SNE. The findings of this study provide a scientific foundation for BS application in broiler feed in the future.

Centennial Review: Recent developments in host-pathogen interactions during necrotic enteritis in poultry

Necrotic enteritis (NE) is a significant enteric disease in commercial poultry with considerable economic effect on profitability manifested by an estimated $6 billion in annual losses to the global industry. NE presents a unique challenge, being a complex enteric disease that often leads to either clinical (acute) or subclinical (chronic) form. The latter typically results in poor performance (reduced feed intake, weight gain and eventually higher feed conversion ratio [FCR]) with low mortality rates, and represents the greatest economic impact on poultry production. The use of antibiotic growth promoters (AGPs) has been an effective tool in protecting birds from enteric diseases by maintaining enteric health and modifying gut microbiota, thus improving broilers’ production efficiency and overall health. The removal of AGPs presented the poultry industry with several challenges, including reduced bird health and immunity as well as questioning the safety of poultry products. Consequently, research on antibiotic alternatives that can support gut health was intensified. Probiotics, prebiotics, essential oils, and organic acids were among various additives that have been tested for their efficacy against NE with some being effective but not to the level of AGPs. The focus of this review is on the relationship between NE pathogenesis, microbiome, and host immune responses, along with references to recent reviews addressing production aspects of NE. With a comprehensive understanding of these dynamic changes, new and programmed strategies could be developed to make use of the current products more effectively or build a stepping stone toward the development of a new generation of supplements.

Dietary Lactobacillus fermentum and Bacillus coagulans Supplementation Modulates Intestinal Immunity and Microbiota of Broiler Chickens Challenged by Clostridium perfringens

Preventative effects of Lactobacillus fermentum and Bacillus coagulans against Clostridium perfringens infection in broilers have been well-demonstrated. The present study was conducted to investigate the modulation of these two probiotics on intestinal immunity and microbiota of C. perfringens-challenged birds. The 336 one-day-old broilers were assigned to four groups with six replicates in each group. Birds in the control were unchallenged and fed a basal diet, and birds in the three challenged groups were dietary supplemented with nothing (Cp group), 1 × 10⁹ CFU/kg of L. fermentum (Lf_Cp group), or 1 × 10¹⁰ CFU/kg of B. coagulans (Bc_Cp group). Challenge was performed from days 14 to 20, and samples were collected on days 21 and 28. Challenge upregulated interleukin (IL)-1β and transforming growth factor (TGF)-β4 mRNA expression in jejunum on day 21, which was downregulated by B. coagulans and L. fermentum, respectively (P < 0.05). Both probiotic groups upregulated jejunal IL-1β, interferon (IFN)-γ, IL-17, and TGF-β4 on day 28 as well as IFN-γ on day 21 (P < 0.05). The Bc_Cp group increased CD3⁺ T cell counts in the jejunal crypt on day 21 (P < 0.05). Challenge decreased the ileal ACE index on day 21 and cecal microbial richness on day 28, which were increased by probiotic treatments, and ileal bacterial richness decreased in the Bc_Cp group on day 28 (P < 0.05). Only ileal microbiota on day 21 was distinctly affected with an R-value at 0.3116 by ANOSIM analysis (P < 0.05). Compared with the control, ileal Firmicutes increased on day 21, and ileal Bacteroidetes and cecal Proteobacteria decreased on day 28 in challenged groups (P < 0.05). Challenge increased Romboutsia spp. in the ileum as well as unclassified f_Lachnospiraceae and Ruminococcus_torques group in the cecum, and decreased Lactobacillus spp. in the ileum on day 21, which were all conversely modulated by L. fermentum (P < 0.05). Challenge increased amino acid metabolism of ileal microbiota and membrane transport of cecal microbiota, and decreased amino acid metabolism of cecal microbiota on day 21, which were conversely regulated by both probiotics (P < 0.05). In conclusion, L. fermentum and B. coagulans attenuated the intestinal inflammation and microbial dysbiosis soon after C. perfringens challenge.

Probiotics Bacillus licheniformis Improves Intestinal Health of Subclinical Necrotic Enteritis-Challenged Broilers

Necrotic enteritis infection poses a serious threat to poultry production, and there is an urgent need for searching effective antibiotic alternatives to control it with the global ban on in-feed antibiotics. This study was conducted to investigate the effects of dietary Bacillus licheniformis replacing enramycin on the growth performance and intestinal health of subclinical necrotic enteritis (SNE)-challenged broilers. In total, 504 1-day-old Arbor Acres male chickens were selected and subsequently assigned into three treatments, including PC (basal diet + SNE challenge), PA (basal diet extra 10 mg/kg enramycin + SNE challenge), and PG (basal diet extra 3.20 × 109 and 1.60 × 109 CFU B. licheniformis per kg diet during 1-21 days and 22-42 days, respectively + SNE challenge). Results showed that B. licheniformis significantly decreased the intestinal lesion scores and down-regulated the Claudin-3 mRNA levels in jejunum of SNE-infected broilers on day 25, but increased the mucin-2 gene expression in broilers on day 42. In addition, B. licheniformis significantly up-regulated the mRNA levels of TRIF and NF-κB of SNE-challenged broilers compared with the control group on day 25 and TLR-4, TRIF compared with the control and the antibiotic group on day 42. The mRNA expression of growth factors (GLP-2 and TGF-β2) and HSPs (HSP60, HSP70, and HSP90) were up-regulated in B. licheniformis supplementary group on days 25 and 42 compared with group PC. LEfSe analysis showed that the relative abundance of Lachnospiraceae_UCG_010 was enriched in the PG group; nevertheless, Clostridiales_vadinBB60 and Rnminococcaceae_NK4A214 were in PA. PICRUSt analysis found that the metabolism of cofactors and vitamins, amino acid metabolism, and carbohydrate metabolism pathways were enriched, whereas energy metabolism, membrane transport, cell motility, and lipid metabolism were suppressed in B. licheniformis-supplemented groups as compared with the PC control. In conclusion, dietary supplementation of B. licheniformis alleviated the intestinal damage caused by SNE challenge that coincided with modulating intestinal microflora structure and barrier function as well as regulating intestinal mucosal immune responses.

The Acute Host-Response of Turkeys Colonized With Campylobacter coli

Consumption of contaminated poultry products is one of the main sources of human campylobacteriosis, of which Campylobacter jejuni subsp. jejuni (C. jejuni) and C. coli are responsible for ~98% of the cases. In turkeys, the ceca are an important anatomical site where Campylobacter asymptomatically colonizes. We previously demonstrated that commercial turkey poults colonized by C. jejuni showed acute changes in cytokine gene expression profiles, and histological intestinal lesions at 2 days post-inoculation (dpi). Cecal tonsils (CT) are an important part of the gastrointestinal-associated lymphoid tissue that surveil material passing in and out of the ceca, and generate immune responses against intestinal pathogens. The CT immune response toward Campylobacter remains unknown. In this study, we generated a kanamycin-resistant C. coli construct (CcK) to facilitate its enumeration from cecal contents after experimental challenge. In vitro analysis of CcK demonstrated no changes in motility when compared to the parent isolate. Poults were inoculated by oral gavage with CcK (5 × 107 colony forming units) or sterile-media (mock-colonized), and euthanized at 1 and 3 dpi. At both time points, CcK was recovered from cecal contents, but not from the mock-colonized group. As a marker of acute inflammation, serum alpha-1 acid glycoprotein was significantly elevated at 3 dpi in CcK inoculated poults compared to mock-infected samples. Significant histological lesions were detected in cecal and CT tissues of CcK colonized poults at 1 and 3 dpi, respectively. RNAseq analysis identified 250 differentially expressed genes (DEG) in CT from CcK colonized poults at 3 dpi, of which 194 were upregulated and 56 were downregulated. From the DEG, 9 significantly enriched biological pathways were identified, including platelet aggregation, response to oxidative stress and negative regulation of oxidative stress-induced intrinsic apoptotic signaling pathway. These data suggest that C. coli induced an acute inflammatory response in the intestinal tract of poults, and that platelet aggregation and oxidative stress in the CT may affect the turkey's ability to resist Campylobacter colonization. These findings will help to develop and test Campylobacter mitigation strategies to promote food safety in commercial turkeys.

Transversal gene expression panel to evaluate intestinal health in broiler chickens in different challenging conditions

There is a high interest on gut health in poultry with special focus on consequences of the intestinal diseases, such as coccidiosis and C. perfringens-induced necrotic enteritis (NE). We developed a custom gene expression panel, which could provide a snapshot of gene expression variation under challenging conditions. Ileum gene expression studies were performed through high throughput reverse transcription quantitative real-time polymerase chain reaction. A deep review on the bibliography was done and genes related to intestinal health were selected for barrier function, immune response, oxidation, digestive hormones, nutrient transport, and metabolism. The panel was firstly tested by using a nutritional/Clostridium perfringens model of intestinal barrier failure (induced using commercial reused litter and wheat-based diets without exogenous supplementation of enzymes) and the consistency of results was evaluated by another experiment under a coccidiosis challenge (orally gavaged with a commercial coccidiosis vaccine, 90× vaccine dose). Growth traits and intestinal morphological analysis were performed to check the gut barrier failure occurrence. Results of ileum gene expression showed a higher expression in genes involved in barrier function and nutrient transport in chickens raised in healthy conditions, while genes involved in immune response presented higher expression in C.perfringens-challenged birds. On the other hand, the Eimeria challenge also altered the expression of genes related to barrier function and metabolism, and increased the expression of genes related to immune response and oxidative stress. The panel developed in the current study gives us an overview of genes and pathways involved in broiler response to pathogen challenge. It also allows us to deep into the study of differences in gene expression pattern and magnitude of responses under either a coccidial vaccine or a NE.

Slight Disruption in Intestinal Environment by Dextran Sodium Sulfate Reduces Egg Yolk Size Through Disfunction of Ovarian Follicle Growth

Intestinal environments such as microbiota, mucosal barrier function, and cytokine production affect egg production in laying hens. Dextran sodium sulfate (DSS) is an agent that disrupts the intestinal environment. Previously, we reported that the oral administration of dextran sodium sulfate (DSS: 0.9 g/kg BW) for 5 days caused severe intestinal inflammation in laying hens. However, the DSS concentration in the previous study was much higher to induce a milder disruption of the intestinal environment without heavy symptoms. Thus, the goal of this study was to determine the effects of a lower dose of DSS on the intestinal environment and egg production in laying hens. White Leghorn laying hens (330-day old) were oral administered with or without 0.225 g DSS/kg BW for 28 days (DSS and control group: n = 7 and 8, respectively). Weekly we collected all laid eggs and blood plasma samples. Intestinal tissues, liver, ovarian follicles, and the anterior pituitary gland were collected 1 day after the final treatment. Lower concentrations of orally administered DSS caused (1) a decrease in the ratio of villus height/crypt depth, occludin gene expressions in large intestine and cecal microbiota diversity, (2) a decrease in egg yolk weight, (3) an increase in VLDLy in blood plasma, (4), and enhanced the egg yolk precursor accumulation in the gene expression pattern in the follicular granulosa layer, (5) an increase in FSH and IL-1β gene expression in the pituitary gland, and (6) an increase in concentration of plasma lipopolysaccharide binding protein. These results suggested that the administration of the lower concentration of DSS caused a slight disruption in the intestinal environment. This disruption included poor intestinal morphology and decreased cecal microbiome diversity. The change in the intestinal environment decreases egg yolk size without decreasing the VLDLy supply from the liver. The decrease in egg yolk size is likely to be caused by the dysfunction of egg-yolk precursor uptake in ovarian follicles. In conclusion, the oral administration of a lower dose of DSS is an useful method to cause slight disruptions of intestinal environment, and the intestinal condition decreases egg yolk size through disfunction of ovarian follicle.