Optimized necrotic enteritis model producing clinical and subclinical infection of Clostridium perfringens in broiler chickens

Elucidating the Varying Impact of Necrotic Enteritis Using Performance and Health Indicators in Broiler Infection Models

Necrotic enteritis (NE) continues to be a significant burden to the poultry industry, compounded by pressure to reduce antibiotic use. Researchers use NE-challenge models to study the infection biology of NE and as screening tools to develop potential novel interventions. Currently, data are limited comparing such models between research establishments, and few indicate which quantitative metrics provide the most accurate measure for determining the efficacy of interventions. We compared data from 10 independent NE-challenge trials incorporating six challenge models employed in four geographical regions to determine the extent of variability in bird responses and to determine, using principal component analysis (PCA), which variables discriminated most effectively between nonchallenged control (NC) and challenged control (CC) groups. Response variables related to growth performance (weight gain, feed intake, feed conversion), health (mortality, lesion scores, NE induction rate), and, in three trials only, gut integrity (tight junction protein claudin-1, claudin-2, and zonula occludens-1 expression, coccidia counts, and intestinal permeability [assessed by FITC-dextran assay]). Treatments included a CC, which varied between trials (for example, in Eimeria predisposition, Clostridium perfringens strain, and days of inoculation), and a NC. The degree of response to challenge in CC birds varied significantly among models and trials. In all trials, lesion scores 1 to 4 days postchallenge were increased in CC vs. NC birds and varied both within and among models (by 0.29-1.17 points and 0.05-2.50 points, respectively). In addition, NE-related mortality at day 28 was increased in CC vs. NC, both within and among models (by 1.79%-4.72% and 0.02%-16.70%, respectively), and final (day 35 or 42) body weight was reduced by 3.9%-14.4% and overall FCR increased by up to 27% across trials (P , 0.05). A PCA on the combined dataset including only performance indicators failed to adequately differentiate NC and CC groups. However, the combination of performance and gut integrity variables and standardization of data by trial and phase achieved greater resolution between groups. This indicated that the inclusion of both types of variables in future NE-challenge studies would enable the generation of more robust predictions about intervention efficacy from different types of infection models. A final PCA based on a subset of key indicator variables, including body weight, feed intake, feed conversion ratio, mortality, and lesion score, achieved a good level of separation between NC and CC status of birds and could, with further research, be a useful supplement to existing approaches for assessing and predicting the NE status of birds in the field.

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.

Effect of synbiotic supplementation on production performance and severity of necrotic enteritis in broilers during an experimental necrotic enteritis challenge

To evaluate the efficacy of synbiotic during a necrotic enteritis (NE) infection, a total of 360 day-old chicks were randomly assigned into 4 experimental groups in a 2 × 2 factorial setup: control, challenge, synbiotic (1 g/kg), and challenge + synbiotic, with 6 replicates. NE was induced by gavaging 1 × 104Eimeria maxima oocysts and 1 × 108 CFU/mL of Clostridium perfringens on d 14 (D14) and D19, 20, and 21, respectively. At D35, the NE challenge decreased the BW gain (P < 0.001) and increased feed conversion ratio (P = 0.03), whereas synbiotic supplementation decreased the feed intake (P = 0.04). At D21, NE challenge increased gut permeability (P < 0.001), decreased regulatory T cells (Tregs) in the cecal tonsil (CT) (P = 0.02), increased Tregs in the spleen (P = 0.02), decreased nitric oxide (NO) production in the spleen (P = 0.04) and decreased IL-10 expression in CT (P = 0.02), whereas synbiotic supplementation increased CD4+:CD8+ T cells in the spleen (P < 0.001) and decreased interferon (IFN)-γ expression in the jejunum (P = 0.07), however, synbiotic supplementation during NE challenge decreased mid-gut lesion score (P < 0.001), increased CD4+:CD8+ T cells in CT and decreased IgA production in bile (P < 0.001), compared to the control group. At D28, synbiotic supplementation decreased CD4+:CD8+ T cells in CT (P < 0.001), whereas synbiotic supplementation during NE challenge decreased Tregs in CT (P < 0.001) and increased NO production in the spleen (P = 0.04), compared to the control group. At D35, the NE challenge decreased CD4+:CD8+ T cells in the spleen (P = 0.03), decreased IgA production in bile (P = 0.02), decreased IL-10 expression in CT (P = 0.04), and decreased IL-10 (P = 0.009), IFN-γ (P = 0.03) and inducible nitric oxide synthase (P = 0.02) expression in the jejunum, whereas synbiotic supplementation increased Tregs in the spleen (P = 0.04), compared to control group. Synbiotic supplementation during the NE challenge decreased both IL-1β (P = 0.02) and IFN-γ (P = 0.001) expression in CT, compared to the control group. It can be concluded that synbiotic supplementation increases production performance by decreasing mid-gut lesions and enhancing protective immunity against NE, and efficiency of synbiotic could be improved by blending additional probiotics and prebiotics.

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.

Evaluation of Three Vaccination Schemes Against Clostridium perfringens Alpha Toxin and Their Effects on the Performance, Level of Intestinal Lesions, and Serum Antibody Titers in Broilers

The objective of the trial was to evaluate three vaccination schemes against Clostridium perfringens (CP) alpha-toxoid through drinking water to determine if they can protect against clinical signs of necrotic enteritis and coccidiosis in broiler chickens. Three hundred 1-day-old Cobb 500 male chicks were used in 4 treatments with 10 repetitions. Each group received 1 of the following treatments over the course of 29 days: T1, no vaccination; T2, vaccination on Day 1; T3, vaccination on Day 7; and T4, vaccination on Days 7 and 17. The birds were vaccinated with inactivated CP toxoid type A, administered via drinking water. During the first 14 days, a high-protein diet (27%) consisting of corn, soy, and fish meal was fed. On Day 14 Eimeria acervulina (EA), Eimeria maxima (EMx), Eimeria tenella (ET), Eimeria necatrix, and Eimeria brunetti were used in a coccidial challenge. The field isolate CP type A was then inoculated on Days 18, 19, and 20. Ten birds were slaughtered by treatment to obtain serology samples for antibody titers and intestine samples for CP and Eimeria lesion score and gut integrity indicators. Productive performance was assessed using complete randomized design and compared statistically using the Tukey test, whereas intestinal integrity variables and antibodies against CP alpha toxin were assessed using a Kruskal-Wallis nonparametric method. The results revealed that the treatments had an effect on productive performance (P < 0.05); T3 had better body weight and weight gain than T1. In terms of lesion score at Day 21, T4 had a lower lesion score by EA, EMx, and ET than T1. Cell desquamation in T2 was lower than in T4, and excess mucus (EM) in T1 was the worst in gut integrity indicators at Day 21. On the other hand, T2 had more EM than T3 and T4 at Day 25. In the measurement of antibodies, no statistical differences (P > 0.05) were found. These findings indicate that vaccination on Day 7 (T3) outperformed double vaccination on Days 7 and 17 (T4) and single on Day 1 (T2), in terms of productive performance, gut integrity, and lesion scores; and on the last day of the experiment T3 had the best performance in immunology response.

A lytic bacteriophage isolate reduced Clostridium perfringens induced lesions in necrotic enteritis challenged broilers

Background

Bacteriophages are viral predators of bacteria and are common in nature. Their host-specific infections against specific bacteria make them an attractive natural agent to control bacterial pathogens. Interest in the potential of bacteriophages as antibacterial agents in the production animal industries has increased.

Methods

A total of 18 bacteriophages were isolated from Australian commercial poultry environments, from which three highly active phages were chosen for enrichment. Sequencing libraries were prepared using a Nextera XT kit (Illumina) and sequenced on an Illumina MiSeq instrument using 2 × 300 bp paired-end chemistry. The sequence data were then assembled and aligned with a2 bacteriophage as the reference. An animal trial was performed by oral gavaging Clostridium perfringens netB containing strain EHE-NE18 to the Ross 308 broiler chickens prior inoculation with Eimeria species. The chickens were raised following the management guide for Ross 308 from d 0 to d 21 and fed with starter and grower diets met the specific breed nutrient requirements. Body weight gain and feed intake were measured on d 9 and d 21 and FCR adjusted with mortality was calculated.

Results

The isolated bacteriophages only had only 96.7% similarity to the most closely related, previously characterized, Clostridium bacteriophage indicated that they might represent a novel strain of bacteriophage. A "cocktail" containing the three bacteriophages was capable of lysing four known disease-inducing C. perfringens strains in vitro. Oral administration of the bacteriophages cocktail to broilers challenged with necrotic enteritis markedly alleviated intestinal necrotic lesions in the duodenum and jejunum on day 16 post-hatch. The phage treatment significantly reduced the lesion scores of birds challenged with NE (P < 0.01), and the lesion scores between birds treated with the bacteriophages and the unchallenged birds were not statistically different (P > 0.05). However, no effect on the growth performance was observed during the recorded period of days 9-21.

Conclusion

These findings suggest that bacteriophage treatment is a promising approach to protect intestinal health from C. perfringens induced necrotic enteritis. Further research will be required on the dosing, route of administration, and large scale validation studies to further advance this approach to pathogen control.

Necrotic Enteritis in Broiler Chickens: A Review on the Pathogen, Pathogenesis, and Prevention

Clostridium perfringens type A and C are the primary etiological agents associated with necrotic enteritis (NE) in poultry. The predisposing factors implicated in the incidence of NE changes the physical properties of the gut, immunological status of birds, and disrupt the gut microbial homeostasis, causing an over-proliferation of C. perfringens. The principal virulence factors contributing to the pathogenesis of NE are the α-toxin, β-toxin, and NetB toxin. The immune response to NE in poultry is mediated by the Th1 pathway or cytotoxic T-lymphocytes. C. perfringens type A and C are also pathogenic in humans, and hence are of public health significance. C. perfringens intoxications are the third most common bacterial foodborne disease after Salmonella and Campylobacter. The restrictions on the use of antibiotics led to an increased incidence of NE in poultry. Hence, it is essential to develop alternative strategies to keep the prevalence of NE under check. The control strategies rely principally on the positive modulation of host immune response, nutritional manipulation, and pathogen reduction. Current knowledge on the etiology, pathogenesis, predisposing factors, immune response, effect on the gut microbial homeostasis, and preventative strategies of NE in this post-antibiotic era is addressed in this review.

Stimbiotic supplementation modulated intestinal inflammatory response and improved boilers performance in an experimentally-induced necrotic enteritis infection model

Background

Two experiments were conducted to establish an optimal NE challenge model and evaluate the efficacy of stimbiotic (STB) supplementation in necrotic enteritis (NE) challenged broilers. In Exp. 1, a total of 120 Arbor Acres (AA) broilers (45.0 ± 0.21 g) were randomly assigned to 6 treatments in a 3 × 2 factorial arrangement. Vaccine treatments included non-challenge (0), × 10 the recommended dose (× 10) or × 20 the recommended dose (× 20) by the manufacturer. Clostridium perfringens (CP) treatments were non-challenge (No) or 3 mL of 2.2 × 10⁷ CFU CP challenge (Yes). In Exp. 2, a total of 72 AA broilers (40.17 ± 0.27 g) were randomly assigned to 6 treatments in a 3 × 2 factorial arrangement. Dietary treatments included non-additive (CON), 100 mg/kg STB (STB) and 100 mg/kg STB on top of a typical commercial blend including an essential oil, probiotics, and enzyme (CB). Challenge treatments included non-NE challenge (No) and NE challenge (Yes) as established in Exp. 1.

Results

In Exp. 1, CP and vaccine challenge decreased (P < 0.05) body weight (BW), body weight gain (BWG) and feed intake (FI), and increased (P < 0.05) the number of broilers with diarrhea and intestinal lesions. The oral administration of × 20 recommended dose of vaccines coupled with 3 mL of 2.2 × 10⁷ CFU CP resulted in (P < 0.01) a significantly increased incidence of wet litter and intestinal lesions. Thus, this treatment was chosen as the challenge model for the successful inducement of NE in Exp. 2. In Exp. 2, the NE challenge negatively affected (P < 0.01) growth performance, ileal morphology, immunoglobulin contents in blood, caecal microbiota in the caecum, footpad dermatitis, intestinal lesion scores, tumour necrosis factor (TNF-α) and endotoxin in the serum compared with the non-NE challenged birds. The supplementation of STB and CB in diets enhanced (P < 0.05) growth performance, intestinal microbiota, and blood profiles by stimulating ileal morphology (VH and VH:CD) and propionate production in the cecum, and there were no differences in measured variables between STB and CB supplemented birds.

Conclusion

Overall, these results indicate that STB supplementation was able to reduce the inflammatory response and improve the performance of NE challenged birds, and the supplementation of STB alone was as effective as a typical commercial blend containing a number of other additives.

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.

A Poultry Subclinical Necrotic Enteritis Disease Model Based on Natural Clostridium perfringens Uptake

Necrotic enteritis (NE) in poultry is an opportunistic infection caused by Clostridium perfringens. Well-known as a multifactorial disease, NE development is under the influence of a wide range of environmental risk factors that promote the proliferation of pathogenic C. perfringens at the expense of nonpathogenic strains. Current in vivo NE challenge models typically incorporate pre-exposure to disease risk factors, in combination with exogenous C. perfringens inoculation. Our goal was to enhance current models using a natural uptake of C. perfringens from the barn environment to produce a subclinical infection. We incorporated access to litter, coccidial exposure (either 10× or 15× of the manufacturer-recommended Coccivac B52 Eimeria vaccine challenge; provided unspecified doses of E. acervulina, E. mivati, E. tenella, and two strains of E. maxima), feed composition, and feed withdrawal stress, and achieved the commonly observed NE infection peak at 3 weeks post-hatch. NE severity was evaluated based on gut lesion pathology, clinical signs, and mortality rate. Under cage-reared conditions, 15× coccidial vaccine-challenged birds showed overall NE lesion prevalence that was 8-fold higher than 10× coccidial vaccine-challenged birds. NE-associated mortality was observed only in a floor-reared flock after a 15× coccidial vaccine challenge.

Vaccines Using Clostridium perfringens Sporulation Proteins Reduce Necrotic Enteritis in Chickens

Clostridium perfringens is the prevalent enteric pathogen in humans and animals including chickens, and it remains largely elusive on the mechanism of C. perfringens-induced enteritis because of limited animal models available. In this study, we investigated the role of C. perfringens sporulation proteins as vaccine candidates in chickens to reduce necrotic enteritis (NE). C. perfringens soluble proteins of vegetative cells (CP-super1 and CP-super2) and spores (CP-spor-super1 and CP-spor-super2) were prepared, and cell and chicken experiments were conducted. We found that deoxycholic acid reduced C. perfringens invasion and sporulation using the Eimeria maxima and C. perfringens co-infection necrotic enteritis (NE) model. C. perfringens enterotoxin (CPE) was detected in the CP-spor-super1&2. CP-spor-super1 or 2 induced cell death in mouse epithelial CMT-93 and macrophage Raw 264.7 cells. CP-spor-super1 or 2 also induced inflammatory gene expression and necrosis in the Raw cells. Birds immunized with CP-spor-super1 or 2 were resistant to C. perfringens-induced severe clinical NE on histopathology and body weight gain loss. CP-spor-super1 vaccine reduced NE-induced proinflammatory Ifnγ gene expression as well as C. perfringens luminal colonization and tissue invasion in the small intestine. Together, this study showed that CP-spor-super vaccines reduced NE histopathology and productivity loss.

Ameliorative Effects of Anti-Clostridial Egg Yolk Antibodies (IgYs) in Experimentally-Induced Avian Necrotic Enteritis

Simple Summary

Necrotic enteritis (NE) is an important enteric infection in poultry. Since the ban on the use of antimicrobials growth promoters, NE has re-emerged significantly in commercial poultry. The current study aimed to evaluate the ameliorative effects of anti-clostridial egg yolk antibodies (EYAs) in NE. Passively immunized birds showed improved behavioral signs and gross and microscopic lesions. Although EYAs showed ameliorative potential in our study, studies regarding safe production and reliable application remain overdue.

Abstract

The present study was planned to evaluate the ameliorative effects of egg yolk antibodies (EYAs) in broiler chicken. For this purpose, 80-day-old broiler chickens were divided into four groups (A–D), where group A was kept as negative control. Experimental infection with C. perfringens (1 × 10⁸ cfu/mL) was induced via oral route on days 17, 18 and 19 of the experiment in groups B, C and D. Groups C and D were passively immunized by anti-clostridial IgYs @ 1 mL per bird via oral and oral and intramuscular (I/M) routes respectively, on days 21 to 24, and on days 22 and 24 of the experiment, respectively. Two necropsies were performed (the first on day 26th and the second on day 35th). Birds in group B showed behavioral signs e.g., laziness, depression and diarrhea, gross post-mortem lesions e.g., increase in the relative weights (RW), due to acute swelling and congestion of liver and kidneys and ballooning and hemorrhages of jejunum and microscopic lesions e.g., congestion and necrosis in liver and kidneys’ parenchyma and disrupted epithelium with fewer goblet cells in jejunum, compared to the group A. Birds in groups C and D, showed significant improvements in clinical and behavioral signs, RW of liver, kidneys and jejunum, swelling, congestion and mononuclear cells’ infiltration in liver and kidneys and damages in the jejunal-wall, compared to group B. The most significant changes were found in birds of group C. Our study revealed ameliorative effects of EYAs on certain biological parameters however, further studies would be needed to justify a safer production and a reliable application of EYAs in NE outbreaks.

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.

Organic acid blends improve intestinal integrity, modulate short-chain fatty acids profiles and alter microbiota of broilers under necrotic enteritis challenge

Controlling enteric diseases of broilers is crucial. Among many additives, organic acids (OA) and their blends are gaining attention to combat diseases in the post-antibiotic era. The current study evaluated the potentials of short-chain fatty acids (SCFA) and medium-chain fatty acids (MCFA) blends and/or phenolic compounds on intestinal integrity, intestinal pH, caecal microbiota, and caecal SCFA profiles of broilers under necrotic enteritis (NE) challenge. The additives used were: (A) a blend of SCFA, MCFA, and a phenolic compound (SMP), (B) a blend of free and buffered SCFA with MCFA (SMF), and (C) a blend of free and buffered SCFA with a high concentration of MCFA (SHM). A total of 1,404 male parental chicks of Ross 308 broilers were randomly allocated to 78 floor pens on hatching day with 6 treatments replicated 13 times with 18 birds per pen. The treatments were: UCC, unchallenged control; CHC, challenged control; BAC, challenged group plus zinc bacitracin; SMP, challenged group plus additive SMP; SMF, challenged group plus additive SMF; SHM, challenged group plus additive SHM. Birds were challenged with field-strain Eimeria spp. on d 9 and Clostridium perfringens on d 14. Birds challenged with NE increased fluorescein isothiocyanate dextran (FITC-d) concentration in serum, reduced acetate and butyrate concentrations, and increased Bacteroides and C. perfringens load in the caeca (P < 0.05). Birds fed additives decreased FITC-d from gut to serum, reduced Bacteroides (d 16, P < 0.05) and numerically reduced C. perfringens load compared to CHC group. Birds fed additive SHM had higher concentrations of acetate and butyrate (d 21, P < 0.05) than CHC group but were not different from SMP and SMF groups. All the additives exhibited similar intestinal protection against NE compared to the BAC group indicated by FITC-d concentration in serum, acetate, propionate and butyrate concentrations in the caeca, and caecal bacterial loads except for the C. perfringens (P > 0.05). The SMP group had a higher load compared to BAC (P < 0.05). These findings suggest the promising effects of OA blends as alternatives to BAC to ameliorate the impact of NE challenge of broilers as indicated by improved intestinal health.

Transgenerational effects of innate immune activation in broiler breeders on growth performance and immune responsiveness

The impact of transgenerational effects on growth performance and immunity has not yet been studied extensively within the poultry husbandry sector. An important factor is the impact of the hens on the physical well-being and fitness to the environment of the offspring. This study is the first to investigate the effect of stimulating the maternal innate immune system with lipopolysaccharides (LPS) or β-glucan on growth performance and immune responses in the next generation. Transgenerational effects and consequences of these maternal treatments were further examined using a necrotic enteritis (NE) challenge model in the offspring. We show that offspring of LPS-treated broiler breeders have a higher feed efficiency from 14 to 21 days of age, that is, the period just after the NE challenge. Moreover, more broiler chickens with intestinal lesions after the NE challenge were found in the offspring of the LPS-treated broiler breeders. Both the LPS and β-glucan maternal treatments resulted in transgenerational effects on blood-derived monocytes by showing a tendency of decreased IL1β mRNA levels after ex vivo LPS stimulation. These data are a first indication that broiler breeder hens can affect immune responsiveness and feeding efficiency of their offspring in a transgenerational manner.

Specific Secondary Bile Acids Control Chicken Necrotic Enteritis

Necrotic enteritis (NE), mainly induced by the pathogens of Clostridium perfringens and coccidia, causes huge economic losses with limited intervention options in the poultry industry. This study investigated the role of specific bile acids on NE development. Day-old broiler chicks were assigned to six groups: noninfected, NE, and NE with four bile diets of 0.32% chicken bile, 0.15% commercial ox bile, 0.15% lithocholic acid (LCA), or 0.15% deoxycholic acid (DCA). The birds were infected with Eimeria maxima at day 18 and C. perfringens at day 23 and 24. The infected birds developed clinical NE signs. The NE birds suffered severe ileitis with villus blunting, crypt hyperplasia, epithelial line disintegration, and massive immune cell infiltration, while DCA and LCA prevented the ileitis histopathology. NE induced severe body weight gain (BWG) loss, while only DCA prevented NE-induced BWG loss. Notably, DCA reduced the NE-induced inflammatory response and the colonization and invasion of C. perfringens compared to NE birds. Consistently, NE reduced the total bile acids in the ileal digesta, while dietary DCA and commercial bile restored it. Together, this study showed that DCA and LCA reduced NE histopathology, suggesting that secondary bile acids, but not total bile acid levels, play an essential role in controlling the enteritis.

Comparison of the Pathogenicity of Five Clostridium perfringens Isolates Using an Eimeria maxima Coinfection Necrotic Enteritis Disease Model in Commercial Broiler Chickens

Clostridium perfringens (CP) is the etiologic agent of necrotic enteritis (NE) in broiler chickens that is responsible for massive economic losses in the poultry industry in response to voluntary reduction and withdrawal of antibiotic growth promoters. Large variations exist in the CP isolates in inducing intestinal NE lesions. However, limited information is available on CP isolate genetics in inducing NE with other predisposing factors. This study investigated the ability of five CP isolates from different sources to influence NE pathogenesis by using an Eimeria maxima (EM) coinfection NE model: Str.13 (from soil), LLY_N11 (healthy chicken intestine), SM101 (food poisoning), Del1 (netB+tpeL-) and LLY_Tpel17 (netB+tpeL+) for NE-afflicted chickens. The 2-wk-old broiler chickens were preinfected with EM (5 × 103 oocysts) followed by CP infection (around 1 × 109 colony-forming units per chicken). The group of the LLY_Tpel17 isolate with EM coinfection had 25% mortality. No mortality was observed in the groups infected with EM alone, all CP alone, or dual infections of EM/other CP isolates. In this model of EM/CP coinfections, the relative percentages of body weight gain showed statistically significant decreases in all EM/CP groups except the EM/SM101 group when compared with the sham control group. Evident gut lesions were only observed in the three groups of EM/LLY_N11, EM/Del1, and EM/LLY_Tpel17, all of which possessed an essential NE pathogenesis locus in their genomes. Our studies indicate that LLY_Tpel17 is highly pathogenic to induce severe gut lesions and would be a good CP challenge strain for studies investigating pathogenesis and evaluating the protection efficacy for antibiotic alternative approaches.

Probiotics and gut health: linking gut homeostasis and poultry productivity

The use of probiotics in poultry production has increased rapidly, and this movement has been promoted by global events, such as the prohibition or decline in the use of antibiotic growth promotants in poultry feeds. There has been a persistent search for alternative feed additives, and probiotics have shown that they can restore the composition of the gut microbiota, and produce health benefits to the host, including improvements in performance. Probiotics have shown potential to increase productivity in poultry, especially in flocks challenged by stressors. However, the outcomes of probiotic use have not always been consistent. There is an increasing demand for well defined products that can be applied strategically, and currently, probiotic research is focusing on delineating their mechanisms of action in the gut that contribute to an improved efficacy. In particular, mechanisms involved in the maintenance and protection of intestinal barrier integrity and the role of the gut microbiota are being extensively investigated. It has been shown that probiotics modulate intestinal immune pathways both directly and through interactions with the gut microbiota. These interactions are key to maintaining gut homeostasis and function, and improving feed efficiency. Research has demonstrated that probiotics execute their effects through multiple mechanisms. The present review describes recent advances in probiotic use in poultry. It focuses on the current understanding of gut homeostasis and gut health in chickens, and how it can be assessed and improved through supplementation of poultry diets with probiotics in poultry diets. In particular, cellular and molecular mechanisms involved in the maintenance and protection of gut barrier structure and function are described. It also highlights important factors that influence probiotic efficacy and bird performance.

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.

Probiotic Bacillus subtilis 29,784 improved weight gain and enhanced gut health status of broilers under necrotic enteritis condition

The study investigated the benefit of a Bacillus subtilis probiotic (Bs 29,784) in necrotic enteritis (NE)-challenged broilers. Four treatments were performed with 312 male day-old Ross 308 reared in floor pens from day 0 to day 35: 2 groups fed control diet without or with NE challenge (CtrlNC and CtrlNE); 2 groups fed probiotic and antibiotic supplements in the control diet with NE challenge (ProNE and AntNE). Necrotic enteritis challenge procedures commenced with inoculation of Eimeria spp 1 mL/bird per os at day 9 and Clostridium perfringens EHE-NE18 (approximately 10⁸ cfu/mL) 1 mL/bird per os at day 14 and day 15. Performance parameters were measured on day 16 and day 35. Lesion, cecal microbiota, and jejunal gene expression were analyzed on day 16. Necrotic enteritis challenge significantly suppressed the performance parameters compared with CtrlNC: 27% weight gain reduction, 11 points feed conversion ratio (FCR) increase at day 16, and 12% weight gain reduction, 5-point FCR increase at day 35. By day 35, ProNE and AntNE treatments enabled significantly higher weight gain (4 and 9%, respectively) than CtrlNE. Compared with CtlrNE and contrary to AntNE, ProNE treatment exhibited upregulation of genes coding for tight junctions proteins (CLDN1, JAM2, TJP1), cytokines (IL12, interferon gamma, TGFβ), and Toll-like receptors (TLR5, TLR21) suggesting enhanced immunity and intestinal integrity. 16S NGS analysis of cecal microbiota at day 16 showed a decreased alpha diversity in challenged groups. Principal component analysis of operational taxonomic unit (OTU) abundance revealed that ProNE and AntNE grouped closely while both distantly from CtrlNC and CtrlNE, which were separately grouped, indicating the similar effects of ProNE and AntNE on the OTU diversity that were however different from both CtrlNC and CtrlNE. Microbiota analysis revealed an increase of genera Faecalibacterium, Oscillospira, and Butyricicoccus; and a decrease of genera Ruminococcus, Lactobacillus, and Bacteroides; and an increase of the Firmicutes-to-Bacteroidetes ratio in ProNE and AntNE groups compared with the CtlrNE group. It is concluded that Bs 29,784 may enable improved health of broiler chickens under NE conditions thus performance implications.

Pretreatment with probiotics ameliorate gut health and necrotic enteritis in broiler chickens, a substitute to antibiotics

Necrotic enteritis (NE) is being considered as one of the most important intestinal diseases in the recent poultry production systems, which causes huge economic losses globally. NE is caused by Clostridium perfringens, a pathogenic bacterium, and normal resident of the intestinal microflora of healthy broiler chickens. Gastrointestinal tract (GIT) of broiler chicken is considered as the most integral part of pathogen's entrance, their production and disease prevention. Interaction between C. perfringens and other pathogens such as Escherichia coli and Salmonella present in the small intestine may contribute to the development of NE in broiler chickens. The antibiotic therapy was used to treat the NE; however European Union has imposed a strict ban due to the negative implications of drug resistance. Moreover, antibiotic growth promoters cause adverse effects on human health as results of withdrawal of antibiotic residues in the chicken meat. After restriction on use of antibiotics, numerous studies have been carried out to investigate the alternatives to antibiotics for controlling NE. Thus, possible alternatives to prevent NE are bio-therapeutic agents (Probiotics), prebiotics, organic acids and essential oils which help in nutrients digestion, immunity enhancement and overall broiler performance. Recently, probiotics are extensively used alternatives to antibiotics for improving host health status and making them efficient in production. The aim of review is to describe a replacement to antibiotics by using different microbial strains as probiotics such as bacteria and yeasts etc. having bacteriostatic properties which inhibit growth of pathogens and neutralize the toxins by different modes of action.

Effect of Probiotics and Multi-Component Feed Additives on Microbiota, Gut Barrier and Immune Responses in Broiler Chickens During Subclinical Necrotic Enteritis

The withdrawal of antibiotic growth promoters from poultry feed has increased the risk of necrotic enteritis (NE) outbreaks. This study examined the effects of a probiotic (PROB) or probiotic/prebiotic/essential oil supplement (PPEO) during a subclinical NE challenge. On day (d) of hatch, 960 male broilers were randomized to four groups (8 pens/treatment, 30 birds/pen) including (1) negative control (NC): corn-soybean meal diet; (2) positive control (PC): NC + 20 g Virginiamycin/ton diet; (3) NC + 227 g PROB/ton diet; and (4) NC + 453 g PPEO/ton diet. One d after placement, birds were challenged by a coccidia vaccine to induce NE. Feed intake and body weights were measured on d 8 (NE onset) and end of each feeding period. On d 8, the small intestines of three birds/pen were examined for NE lesions. Jejunum samples and ileal mucosal scrapings from one bird/pen were respectively collected to measure mRNA abundance (d 8 and d 14) and profile the microbiota (d 8 and d 42). Data were analyzed in JMP or QIIME 2 and significance between treatments identified by LSD (P < 0.05). PROB and PPEO had significantly lower mortality (d 0–14) and NE lesion scores compared to NC. Feed conversion ratio was significantly lower in PC, PROB, and PPEO, while average daily gain was higher in PPEO and PC groups compared to NC from d 0–42. On d 8 and d 14, mRNA abundance of claudin-3 was higher in PPEO compared to NC. On d 14, compared to NC, mRNA abundance of sIgA and PGC-1α in PROB and PPEO were lower and higher, respectively. Compared to NC, PPEO increased mTOR abundance on d 14. On d 8, relative abundance of Clostridium sensu stricto 1, Ruminiclostridium9, Prevotellaceae, Prevotellaceae UCG-014, ASF356, and Muribaculaceae was higher in NC compared to PPEO and PROB, while Lactobacillus was lower in NC. Escherichia-Shigella had higher abundance in PC compared to PPEO and PROB. Collectively, these data indicate that during a subclinical naturally occurring NE, supplementation of PROB or PPEO supports performance and reduces intestinal lesions, potentially through modifying tight junction proteins, gut microbiota, immune responses, and cell metabolism.

Characterization of a novel bacteriophage φCJ22 and its prophylactic and inhibitory effects on necrotic enteritis and Clostridium perfringens in broilers

High necrotic enteritis (NE) incidence and mortality rates in poultry can be caused by Clostridium perfringens (CP) coinfected with Eimeria spp., a causative agent of coccidiosis. Banning of prophylactic use of antibiotics in feed has been accompanied by increased NE outbreaks, resulting in economically devastating losses to the broiler industry. To determine alternatives for controlling NE, we isolated CP-specific bacteriophages (BP), characterized their properties, evaluated their inhibitory effects on pathogenic CP, selected a highly effective phage (φCJ22), and used φCJ22 as a dietary supplement in experimental NE-afflicted broiler chickens. Male broilers (n = 780) were randomly assigned to 60 pens (n = 13 broilers/pen) and into 5 groups [CP-uninfected negative control (NC), basal diet (BD) without CP and BP; CP-infected positive control (PC), BD + CP; and 3 BP groups receiving low- (LP; BD + CP+10⁵ BP), medium- (MP; BD + CP+10⁶ BP), and high-phage (HP; BD + CP+10⁷ BP plaque-forming units/kg) concentrations]. The results showed that MP and HP groups presented an antimicrobial activity toward clinical CP isolate strains, and the groups decreased NE lesions and mortality rates without changes in chicken performance at the end of the experimental period. After CP-challenge body weight gain and feed efficiency were significantly lower in phage-fed groups than that in the PC group (P < 0.05), and NE-associated mortality was the lowest in the HP group (P < 0.001). Moreover, histopathology revealed lesser gastrointestinal mucosal damage in the NC and BP-treated (LP, MP, and HP) groups than that in the PC group, and MP and HP significantly lowered viable CP number in the cecum content by up to 1.24log10 relative to only CP-infected PC group (P < 0.05). These findings suggest that addition of φCJ22 to chicken feed might effectively ameliorate NE, which is accompanied by reduced CP strains in the gut and compensate the performance of NE-afflicted broilers.

Probiotic Bacillus amyloliquefaciens H57 ameliorates subclinical necrotic enteritis in broiler chicks by maintaining intestinal mucosal integrity and improving feed efficiency

Subclinical necrotic enteritis (NE) was induced in broiler chicks using a high dose of Eimeria spp. vaccine in the drinking water on day 9, and Clostridium perfringens (Cp) culture mixed in the feed on days 14 and 15. The aim was to evaluate the effects of probiotic Bacillus amyloliquefaciens strain H57 (H57) in preventing NE in chicks. Day-old Ross 308, male broilers were weighed and randomly assigned to 6 treatment groups (6 replicate cages/treatment and 8 birds/cage). Birds in group 1 (control) were fed the basal wheat-soybean diet without H57 or NE infection; in group 2 (Eimeria) were treated with Eimeria alone; in group 3 (Cp) were treated with Cp alone; in group 4 (NE) received both Eimeria and Cp; in group 5 (NE-H57) received NE infection and H57; and group 6 (H57) received H57. The basal diet of chicks in groups 5 and 6 was supplemented with H57 at a density of 2 × 108 spores/g feed from 1 D of age. On day 21, there were no significant treatment effects on BW and feed intake between control and H57 birds. However, on day 21, the feed conversion ratio of NE-H57 birds was significantly improved when compared with NE birds (1.28 vs. 1.36; P < 0.001). Birds challenged with NE had a higher occurrence of pasty vent than birds infected with either Eimeria, Cp, or NE-H57 (41 vs. 27 vs. 29 vs. 19%, respectively; P < 0.001). Intestinal lesion scores of NE birds were also higher than those of Eimeria, Cp, and NE-H57 birds (5.67 vs. 2.56 vs. 2.78 vs. 2.10, respectively; P < 0.001) and correlated with pasty vent (Pearson's r = 0.56; P < 0.001). Microscopic evaluation showed mucosal damage and necrosis in NE birds. In contrast, villi from NE-H57 birds were normal, with no damage or infiltration with Eimeria or Cp. H57 appears to be effective in challenged birds, as it maintained epithelial barrier integrity and improved feed efficiency.

Two different Clostridium perfringens strains produce different levels of necrotic enteritis in broiler chickens

Subclinical necrotic enteritis (NE) is primarily caused by the gram-positive bacterium, Clostridium perfringens (Cp). The trend towards removal of in-feed antimicrobials and subsequent increased emergence of infection in poultry has resulted in a wide interest in better understanding of the mechanism behind this disease. The virulence of NE, to a large extent, depends on the virulence of Cp strains. Thus, this study was to assess how 2 different strains of Cp affect performance and gut characteristics of broiler chickens. Ross 308 male broilers (n = 468) were assigned to a 2 × 3 factorial arrangement of treatments with antibiotics (Salinomycin at 72 ppm and zinc bacitracin at 50 ppm -, or +) and challenge (non-challenge, Cp EHE-NE18, or Cp WER-NE36). Oral administration of Eimeria oocysts (day 9) followed by inoculation with 1 mL 108 CFU Cp strains (day 14 and 15) were used to induce NE. Broiler performance was analyzed at day 10, 24, and 35. On day 16, intestinal lesion score and intestinal pH were evaluated and samples of cecal content were analyzed for bacterial counts and short-chain fatty acid concentrations (SCFA). Birds in both challenged groups showed higher feed conversion ratio (FCR), lower weight gain (P < 0.001), increased lesion scores in the jejunum (P < 0.01), and reduced pH in the ileum and cecum (P < 0.01), compared to the non-challenged birds. They also showed decreased numbers of Bacillus spp. (P < 0.001), and Ruminococcus spp. (P < 0.01) in the cecal content. On day 35, the NE36 challenged birds had a lower weight gain (P < 0.001) and higher FCR (P < 0.001) compared to the NE18 challenged birds. Interestingly, cecal Lactobacillus and lactate were increased by the NE challenge (P < 0.001), and to a greater extent in birds challenged with NE36 compared to the NE18 strain (P < 0.001). This study suggests that Cp strains varying in virulence produce different levels of disease in broiler chickens through modulating the gut environment, intestinal microbiota, and SCFA profile to different extents.

Reducing protein and supplementing crystalline amino acids, to alter dietary amino acid profiles in birds challenged for subclinical necrotic enteritis

Necrotic enteritis (NE) is an infection of the gastrointestinal tract and is estimated to cost the global poultry industry billions of dollars annually. A study was conducted to examine whether reducing the crude protein might offset the severity of NE in broilers experimentally challenged with Eimeria spp. on day 9 and Clostridium perfringens on days 14 and 15. Furthermore, increasing the dietary amino acid (AA) density of the diet was also examined owing to identified benefits of improving performance compromised from low protein (LP) diets or NE. A 2 × 2 × 3 factorial arrangement of treatments at 6 replicates per treatment was used with 972 Ross 308 cockerels fed wheat-sorghum-soy-based diets to 35 D. Factors were NE challenge: no or yes; protein: standard (SP) or LP; and AA density: 100% AA, 115% with only essential AA (115% EAA) increased, and 115% AA with both essential and nonessential AA (115% AA) increased. The performance was measured in grower (days 7–21), finisher (days 21–35), and overall (day 7–35) periods. In addition, on day 16, intestinal lesion score and cecal short-chain fatty acids were measured. Only in nonchallenged birds fed LP diets, 115% AA increased grower feed intake (P < 0.01) and body weight gain (P < 0.05) compared to 115% EAA treatments. Challenge increased jejunal lesions (P < 0.001) with no difference between dietary treatments. Finisher body weight gain was greater in nonchallenged birds fed the 115% AA diets than in challenged birds (P < 0.05). Feeding diets with higher nonessential AA encouraged faster recovery from NE challenge. When fed the SP diets, NE challenge increased cecal butyric acid (P < 0.01) and total short-chain fatty acids (P < 0.05). The nutrient matrix used in LP diets does not favor beneficial butyric acid–producing bacteria. Using LP diets to mitigate NE severity does not offset the predisposing effect of E. spp. when attacking the gastrointestinal tract, and NE recovery is favored when feeding SP diets or additional AA.

Incidence of Bacterial Chondronecrosis with Osteomyelitis (Femoral Head Necrosis) Induced by a Model of Skeletal Stress and its Correlation with Subclinical Necrotic Enteritis

Bacterial chondronecrosis with osteomyelitis (BCO) is a septic necrosis of the skeletal system of unknown origin and an important cause of lameness in broiler chickens. Epithelial inflammation has been proposed as an avenue for bacterial translocation leading to BCO. We evaluated the effect of subclinical necrotic enteritis (SNE), an intestinal inflammatory event, with the development of BCO. In each of two experiments, chickens were divided into three treatments: (1) SNE challenge, including both dietary (wheat- and fish-based diet) and intestinal pathogenic challenges (Eimeria maxima and Clostridium perfringens), (2) dietary challenge only, and (3) control diet (corn-and soy-based diet). Floor ramps were introduced as part of an established method for increasing the frequency of BCO. The efficacy of the SNE challenge was corroborated by necropsy evaluation of a representative sample of the population. At the end of each experiment, all birds were evaluated for BCO. A high incidence of BCO was found, even in birds with no external signs of lameness. However, the incidence of BCO was not correlated with the intestinal challenge. Conclusions: under the conditions used in these studies, a treatment that is associated with severe damage to the intestinal mucosa does not change the incidence of BCO in broiler chickens.

The netB-positive Clostridium perfringens in the experimental induction of necrotic enteritis with or without predisposing factors

The netB-positive Clostridium perfringens has been considered as the requisite to consistently induce necrotic enteritis (NE). However, use of a netB-positive strain did not guarantee consistent NE reproduction unless high protein diets or Eimeria, conceived as 2 major predisposing factors, was incorporated. To establish a refined model, the roles of dietary fishmeal inclusion, Eimeria inoculation, and netB-positive C. perfringens challenge in NE induction and the confounding effects of Eimeria infection on NE were examined. The results showed that the use of netB-positive C. perfringens without a predisposing factor failed to induce NE. Fishmeal incorporation promoted the occurrence of NE but did not significantly affect the incidence of the disease in conjunction with challenge of netB-positive C. perfringens. However, the additional participation of Eimeria infection in the same induction procedure produced significantly higher numbers of NE cases and promoted more severe lesions in chickens (P < 0.05). Inoculation of Eimeria resulted in a significant higher incidence of NE compared to the non-Eimeria treated group (P < 0.05). The results demonstrated that both netB-positive C. perfringens and predisposing factors were required for the reproduction of disease. Mild-to-moderate coccidial infection (coccidial lesion score ≤ 2) was noted in NE cases in this model but severe coccidial infection did not correlate with the occurrence of NE, indicating mild coccidial infection may be beneficial for the development of NE. If multiple species infection of Eimeria precedes the challenge of C. perfringens, days 19 to 21 (1 to 3 D after the last clostridial challenge) was the time period favorable for observations of NE lesions. The time after this period may be subject to bias of severity, incidence, or mortality of NE owing to the profound coccidial lesions in the intestinal region. This study demonstrated that the co-infection with netB-positive C. perfringens and Eimeria species under fishmeal incorporation produced a desirable NE model, being of value in studying the effectiveness of novel feed additives and alternative mitigation strategies to prevent NE.

The influence of indigestible protein on the performance and meat quality of broilers vaccinated for coccidiosis

High dietary protein and the use of poorly digested protein sources have been suggested to negatively impact broiler health, possibly because of protein fermentation in the distal intestinal tract. The effect of dietary protein levels with low or high indigestible protein fractions (LIP or HIP) on male and female broiler performance were evaluated. The trial was completely randomized with a 2 × 3 × 2 factorial arrangement, where gender, dietary protein levels (24, 26, and 28%), and dietary protein digestible fractions were the main factors. Ross 308 male (1944) and female (2232) were allocated to 72 pens with 54 males or 62 females per pen. Six grower diets 24-LIP, 24-HIP, 26-LIP, 26-HIP, 28-LIP, and 28-HIP were fed from 0 to 32 D of age. Birds were vaccinated with Coccivac-B52 on day 5, and feed intake and BW were recorded on 0, 12, 22, and 32 D. On day 32, 24 birds per treatment were processed for meat yield. Males were heavier than females at all post-hatch ages and the LIP birds were heavier than their HIP counterparts on 32 D. On day 22, birds fed 24 and 26% CP were heavier than those fed 28% CP. Birds fed the 28-LIP diet consumed less total feed than their 24 and 26-LIP equivalents. Birds fed 24% CP had the highest total feed to gain ratio, whereas LIP fed birds had a lower total feed to gain than those fed HIP diets. LIP diets resulted in higher total mortality than the HIP diets. Carcass yield was higher for females than males, increased with CP level, and was lower in HIP than LIP birds. An interaction between CP level and protein digestibility resulted in the 26 and 28-LIP having higher breast yield than all other diets. In conclusion, broiler growth performance and meat yield were affected by dietary indigestible protein alone or in combination with gender and dietary CP level.

The Effect of Clostridium butyricum on Gut Microbiota, Immune Response and Intestinal Barrier Function During the Development of Necrotic Enteritis in Chickens

Necrotic enteritis (NE) causes huge economic losses to the poultry industry. Probiotics are used as potential alternatives to antibiotics to prevent NE. It is known that Clostridium butyricum can act as a probiotic that can prevent infection. However, whether or not it exerts a beneficial effect on NE in chickens remains elusive. Therefore, we investigated the impact of C. butyricum on immune response and intestinal microbiota during the development of NE in chickens, including experimental stages with basal diets, high-fishmeal-supplementation diets, and Clostridium perfringens challenge. Chickens were divided into two groups from day 1 to day 20: one group had its diet supplemented with C. butyricum supplementation and one did not. At day 20, the chickens were divided into four groups: C. perfringens challenged and unchallenged chickens with and without C. butyricum supplementation. All groups were fed a basal diet for 13 days and thereafter a basal diet with 50% fishmeal from day 14 to 24. Chickens were infected with C. perfringens from day 21 to 23. At days 13, 20 and 24, samples were collected for analysis of the relative expression of immune response and intestinal mucosa barrier-related genes and intestinal microbes. The results show that C. butyricum can inhibit the increase in IL-17A gene expression and the reduction in Claudin-1 gene induced-expression caused by C. perfringens challenge. Moreover, C. butyricum was found to increase the expression of anti-inflammatory IL-10 in infected chickens. Although C. butyricum was found to have a significant beneficial effect on the structure of intestinal bacteria in the basal diet groups and decrease the abundance of C. perfringens in the gut, it did not significantly affect the occurrence of intestinal lesions and did not significantly correct the shift in gut bacterial composition post C. perfringens infection. In conclusion, although C. butyricum promotes the expression of anti-inflammatory and tight junction protein genes and inhibits pro-inflammatory genes in C. perfringens-challenged chickens, it is not adequate to improve the structure of intestinal microbiota in NE chickens. Therefore, more effective schemes of C. butyricum supplementation to prevent and treat NE in chickens need to be identified.

Necrotic Enteritis in Broiler Chickens: The Role of Tight Junctions and Mucosal Immune Responses in Alleviating the Effect of the Disease

Necrotic enteritis (NE) continues to present major challenges to the poultry industry, and the etiologic agent Clostridium perfringens is the fourth leading cause of bacterially-induced food- borne illnesses in the US. This study was designed to evaluate the effects of a probiotic during naturally occurring NE. On day of hatch, 1080 Cobb 500 male broilers were randomly allocated to three groups (12 replicate pens/treatment, 30 birds/pen) including 1) negative control (NC): corn-soybean meal diet; 2) positive control (PC): NC + 20 mg virginiamycin/kg diet (0.450 kg Stafac®20/ton); and 3) NC + PrimaLac (1.36 and 0.91 kg/ton from 1-21 and 22-42 days, respectively). One day (d) post placement, all birds were challenged by a commercial live oocyst coccidia vaccine as a predisposing factor to NE. Body weight and feed intake were measured at the onset of NE (d 8) and end of each feeding phase. On d 8, small intestines of two birds/pen were examined for NE lesions, and jejunum samples from one bird were collected for mRNA gene expression analysis of tight junction proteins, cytokines, and nutrient transporters. Data were analyzed using the Jump (JMP) software and significance between treatments identified by LSD (P < 0.05). Compared to NC, supplementation of probiotic reduced d 1-42 mortality; however, PC was the only group with significantly lower mortality. Despite significantly improved feed conversion ratio (FCR) in PC and probiotic groups during d 1-42, average daily gain was only higher in PC (77.69 g/bird) compared with NC (74.99 g/bird). Furthermore, probiotic and PC groups had significantly reduced lesion scores in the duodenum and jejunum compared to NC. Expression of claudin-3 was higher, while expression of zonula occluden-2 tended (P = 0.06) to be higher in probiotic-supplemented birds compared to NC. Moreover, birds fed the probiotic diet had significantly higher expression of IL-10, IL-17, AMPK-α1, and SGLT1 mRNA compared to NC birds. The expression of PepT1 was higher for the probiotic-supplemented group compared to PC. IFN-γ expression was lower in PC compared to NC, while there was no difference between probiotic and NC. There were no differences in gene expression of sIgA, TNF-α, IL-1β, and IL-22 among treatments. Collectively, these data indicate that in a naturally occurring NE model, supplementation of a probiotic helps to improve FCR and reduce lesions, potentially due to the improvements in mRNA expression of tight junctions, cytokines, and nutrient transporters.

Nutritional implications of feeding reduced-protein diets to meat chickens

Global interest has emerged for the implementation of reduced-protein diets for meat chickens. The necessity of their development stems from environmental impacts and health and welfare concerns surrounding current meat-chicken production. Reduced crude-protein diets are possible with the increasing affordability of supplemental crystalline amino acids. Supplementing broiler feed with methionine, lysine and threonine is common practice in industry and has enabled a reduction of dietary crude protein to the levels currently used. However, further reduction of dietary protein often results in poor performance. Several nutritional options have been investigated with a focus on crystalline essential and non-essential amino acids such as glycine. However, reducing the crude protein of meat-chicken diets does change the ingredient and nutrient profile aside from the amino acid composition. Alterations in non-protein nitrogen concentrations, dietary electrolyte balance, minerals, fibre and carbohydrates, methyl-donors and polyphenols must be considered in formulations to ensure successful implementation of reduced-protein diets. The ability to maintain performance with reduced-protein diets may benefit sustainability and longevity of the meat-chicken industry.

Temporal Effects of High Fishmeal Diet on Gut Microbiota and Immune Response in Clostridium perfringens-Challenged Chickens

Necrotic enteritis (NE) caused by Clostridium perfringens is responsible for huge financial losses in the poultry industry annually. A diet highly supplemented with fishmeal is one factor predisposing chickens to the development of clinical NE. However, the effects of fishmeal-rich diets on the gut microbiota and immune response in chickens with C. perfringens challenge over the long-term are not well-understood. Here, a chicken NE model was established in which chickens were fed high fishmeal diet and subsequently infected with C. perfringens (FM/CP). Two control groups of chickens, one that was not infected and had a high fishmeal feeding (FM) and another group only infected with C. perfringens with basic diets (CP), were used as comparators. We analyzed the gut microbiota and immune response of the three groups at the age of 20, 24 [1 day post-infection (dpi)] and 30 days (7 dpi) using 16S rDNA sequencing and real-time PCR, respectively. We found that the composition of the gut microbiota had significant shifted in both the CP and FM/CP groups, although the CP group did not have intestinal lesions. The structure of the gut microbiota in C. perfringens-challenged chickens, independent of a high fishmeal diet, had the tendency to return to their non-infection state if the chickens no longer received C. perfringens challenge. Gut microbiota variation with time in challenged chickens with high fishmeal diet feeding was superimposed upon that of non-infected chickens with high fishmeal feeding. For the immune response, the relative expression of IL-8 in the ileum was significantly higher in infected chickens independent of high fishmeal feeding than in non-infected chickens. However, the expression of alpha 1-acid glycoprotein (AGP) and serum amyloid A (SAA) genes in chicken liver were significantly increased in FM/CP compared to the other groups. In conclusion, high fishmeal feeding induced significant changes to the structure of chicken gut microbiota over time and such changes provided an opening for C. perfringens infection to progress to NE. The relative expression of AGP and SAA in liver tissue may be used as diagnostic biomarkers for poultry NE but such an indication requires further investigation.

Necrotic enteritis challenge and high dietary sodium level affect odorant composition or emission from broilers

Necrotic enteritis (NE) challenge and high dietary sodium (from sodium chloride) level on odor flux from broiler litter was investigated using 160 day-old Ross 308 male chicks randomly assigned to 4 dietary treatments with 4 replicates of 10 birds each. A 2 × 2 factorial arrangement of treatments was employed. Factors were: presence or absence of NE challenge and normal (1.6 g/kg) or high (4.0 g/kg) dietary sodium (Na) level. On d 20, odorants were collected from litter headspace with a flux hood and measured using selected ion flow tube mass spectrometry (SIFT-MS). On d 33, while challenge did not lead to higher mortality, it reduced feed intake by 5.48% (P < 0.05) and body weight gain by 9.02% (P < 0.01) and worsened FCR by 5 points (P < 0.01), indicating subclinical necrotic enteritis occurred in challenged birds. Challenge increased (P < 0.01) litter moisture and litter headspace concentrations of dimethyl sulfide (P < 0.05), propyl mercaptan (P < 0.05), total butanols (P < 0.05), acetoin (P < 0.01), skatole (P = 0.05), butyric acid (P < 0.05), and methyl amine (P < 0.05) and tended to increase concentrations of ethyl mercaptan (P = 0.07), carbon disulfide (P = 0.09), indole (P = 0.10), and formic acid (P = 0.10) compared to the unchallenged group. The birds fed a high Na diet produced higher litter moisture (P < 0.01) and higher litter headspace concentration of sulfur compounds and phenol (P < 0.01) compared to those fed a normal Na diet. In the birds fed a high Na diet, challenge increased the litter flux of some additional odorants, which included 2,3-butanedione (P < 0.05), acetic acid (P < 0.01), propionic acid (P < 0.01), isobutyric acid (P < 0.01), isovaleric acid (P < 0.01), pentanoic acid (P < 0.05), 2-butanone (P < 0.05), and 3-methyl-1-butanol (P < 0.05). These findings suggest that both a high Na diet and sub-clinical NE increase the odor nuisance potential of broiler farms.

Dynamics of intestinal metabolites and morphology in response to necrotic enteritis challenge in broiler chickens

Despite the relatively small contribution to metabolizable energy that volatile fatty acids (VFAs) provide in chickens, these organic acids have been reported to play beneficial roles in the gastrointestinal tract (GIT) of birds, for example, inhibition of the growth of some pathogenic bacteria. However, information regarding the dynamics of these metabolites in the GIT of chickens is still scarce, especially under disease conditions such as necrotic enteritis (NE). Here, we investigated the dynamics of VFAs and lactic acid, and intestinal morphology in response to NE predisposing factors, that is, excessive dietary fishmeal and Eimeria inoculation, and causative agent Clostridium perfringens producing NetB toxin. The experiment was designed in a 2 × 2 × 2 factorial arrangement of treatments with or without: fishmeal feeding, Eimeria inoculation and C. perfringens challenge. The results showed that these factors significantly influenced composition and concentration of VFAs and lactic acids, pH and histomorphometry in one way or another. These changes may be important for the onset of NE or only the synergetic responses to micro environmental stress. Eimeria appeared to be more important than fishmeal in predisposing birds to NE, thus the application of Eimeria in NE challenge provides more consistent success in inducing the disease. The metabolic responses to various adverse factors such as excessive dietary fishmeal and Eimeria infection are complex. Thus, intensive efforts are required to better understand NE so as to achieve the control of the disease in the absence of antibiotics.

Necrotic enteritis predisposing factors in broiler chickens

Necrotic enteritis in chickens develops as a result of infection with pathogenic strains of Clostridium perfringens and the presence of predisposing factors. Predisposing factors include elements that directly change the physical properties of the gut, either damaging the epithelial surface, inducing mucus production, or changing gut transit times; factors that disrupt the gut microbiota; and factors that alter the immune status of birds. In the past research into necrotic enteritis predisposing factors was directed by the simple hypothesis that low-level colonization of C. perfringens commonly occurred within the gut of healthy chickens and the predisposing factors lead to a proliferation of those bacteria to produce disease. More recently, with an increasing understanding of the major virulence factors of C. perfringens and the application of molecular techniques to define different clades of C. perfringens strains, it has become clear that the C. perfringens isolates commonly found in healthy chickens are generally not strains that have the potential to cause disease. Therefore, we need to re-evaluate hypotheses regarding the development of disease, the origin of disease causing isolates of C. perfringens, and the importance of interactions with other C. perfringens strains and with predisposing factors. Many predisposing factors that affect the physical and immunological characteristics of the gastrointestinal tract may also change the resident microbiota. Research directed towards defining the relative importance of each of these different actions of predisposing factors will improve the understanding of disease pathogenesis and may allow refinement of experiment disease models.

Influence of feeding crimped kernel maize silage on the course of subclinical necrotic enteritis in a broiler disease model

This experiment was carried out with 375 male broilers (Ross 308) from days 1 to 28 to evaluate the influence of crimped kernel maize silage (CKMS) on the manifestation of subclinical necrotic enteritis, microbiota counts, organic acid production and relative weights of gastrointestinal segments. A necrotic enteritis disease model was applied. Birds were allocated into 3 different dietary treatments: a maize-based feed (MBF, control diet), and 2 diets supplemented with 15% (CKMS15) or 30% (CKMS30) of crimped ensiled kernel maize. The disease model involved a 10-time overdose of an attenuated live vaccine against coccidiosis given orally on day 17, followed by oral inoculation of Clostridium perfringens Type A (S48, 10⁸ to 10⁹ bacteria/bird) twice daily on days 18, 19, 20 and 21. Scoring of intestinal lesions was performed on days 22, 23, 25 and 28. Ileal and caecal digesta samples were collected for the quantification of selected bacterial groups and organic acids. The results showed that there was no effect of dietary treatments on small intestinal lesion scores (P > 0.05). Lesions scores peaked on days 23 and 25 and decreased again on day 28 (P = 0.001). No effect of age on microbiota counts was observed, but feeding of CKMS30 reduced the number of coliforms in ileal contents (P = 0.01). Dietary treatments did not affect organic acid concentrations in ileum and caeca, but there was an effect of age; butyric acid was higher on days 22, 23 and 25 than on day 28 (P = 0.04). Acetic acid and propionic acid concentrations in caeca were the highest on days 22 and 28 but the lowest on days 23 and 25. Relative gizzard and caeca weights were increased, and relative ileum weights were decreased when birds were fed CKMS30 (P < 0.05). In conclusion, the inclusion of CKMS in broiler diets had no effects on the course of necrotic enteritis but had potential benefits in terms of inhibition of potentially harmful microorganisms.

Disruption in the cecal microbiota of chickens challenged with Clostridium perfringens and other factors was alleviated by Bacillus licheniformis supplementation

Clostridium perfringens can induce necrotic enteritis of chickens, which causes large economic losses every year. Bacillus licheniformis, a probiotic, can inhibit the growth of pathogenic bacteria such as Clostridium perfringens, thereby improving the health status of chickens. However, from a microbial ecology perspective, the mechanisms by which alterations to the gut microbiota improve health remain unknown. In this study, we used Illumina MiSeq sequencing to investigate the cecal microbiota of a negative control group (NC), a C. perfringens and Eimeria challenge group with fishmeal supplementation (PC), a group supplemented with fishmeal and infected with coccidia (FC), and group PC with B. licheniformis supplementation (BL). We found that the health status of C. perfringens-challenged chickens was compromised, and that B. licheniformis improved the growth of the chickens challenged with pathogens. Microbial diversity analysis and taxonomic profiling of groups NC, PC, and FC revealed a disturbed cecal microflora of the birds with C. perfringens. We also characterized the microbiota of the chickens in the BL group using several methods. Principal coordinate analysis demonstrated that, compared with group PC, the bacterial community structure of group BL was more similar to that of group NC. Linear discriminant analysis with effect size revealed less differentially represented bacterial taxa between groups BL and NC than between groups PC and NC. In addition, groups BL and NC appeared to have similar overrepresented microbial taxa (such as Bacteroides, Helicobacter, Megamonas, and Akkermansia) compared with group PC. Finally, a phylogenetic investigation of communities by reconstruction of unobserved states analysis indicated that large differences existed between group PC and groups NC and BL. In conclusion, pre-treatment with B. licheniformis reduced the disturbance of the cecal microbiome induced by challenge with C. perfringens and other factors in broiler chickens.

Immune responses following experimental infection with Ascaridia galli and necrotic enteritis in broiler chickens

Broilers commonly suffer from necrotic enteritis (NE). Other gastrointestinal infectious diseases affect poultry, including nematode infections which are considered a re-emerging disease in barn and free-range systems. The aim of this study was to characterize the immune response of broilers after artificial infection with NE and contrast these with responses to the nematode Ascaridia galli and determine whether immune parameters measured during the course of infection can be used to distinguish infected from uninfected birds. A total of 96 one-day-old male Ross 308 broiler chickens were used in this study. At 10 days of age, broilers were randomly assigned to one of the following treatment groups: control birds (n = 32), A. galli infected birds (n = 32), or NE infected birds (n = 32) and inoculated with the appropriate infective agents. The immune response of birds was monitored through evaluation of haematology parameters, acute phase protein production, and intraepithelial intestinal lymphocyte population changes at 11, 16, 20, and 32 days of age. T-helper cells (CD4⁺CD8^-) increased significantly over time, and were significantly higher in A. galli and NE compared to day 10 controls. In conclusion, α-1 glycoprotein levels can distinguish birds with NE from other birds, including those infected with A. galli; also T-helper cell numbers can distinguish both NE and A. galli from uninfected birds and thirdly, 10 days post infection is the best time point to evaluate the bird's immune response for A. galli infections.

Dietary inclusion of arabinoxylo-oligosaccharides in response to broilers challenged with subclinical necrotic enteritis

1. This study investigated the prebiotic properties of arabinoxylo-oligosaccharides (AXOS) produced both in situ and in vitro for their activity against the onset of necrotic enteritis in broiler chickens. 2. A 2 × 3 factorial arrangement was applied, including necrotic enteritis challenge (challenged/unchallenged) and three dietary treatments from d 10 to 21. A wheat-soy commercial-type basal-grower diet was fed with 2% of the wheat proportion replaced by the same amount of either arabinoxylan (AX), AXOS produced from hydrolysing AX with 16 000 BXU (birch xylanase unit) xylanase in vitro or AX fed with 16 000 BXU xylanase (AX + E). Necrotic enteritis (NE) challenge was induced by orally infecting birds with a vaccine strain of Eimeria oocysts at d 9 of age followed by oral gavage of a freshly prepared Clostridium perfringens broth at d 14. 3. The challenge depressed growth performance, induced gross lesions and reduced ileal viscosity at d 10-21. Birds fed on the AXOS diet had numerically less severe gross lesions, improved feed conversion at d 0-16 and lower ileal viscosity at d 16 compared to birds fed on AX. Weight gain of the unchallenged birds ranked as follows in terms of the diets: AXOS > AX + E > AX. AX + E produced a lower ileal viscosity compared to the AX treatment but only led to marginal improvements in performance and intestinal lesion scores. 4. Caecal short-chain fatty acid (SCFA) concentration was higher in birds fed on AXOS and AX + E compared to those fed on AX and was higher in the challenged birds compared to the unchallenged birds. Gizzard pH was lower in birds fed on AX + E compared to those fed on AXOS at d 16. Challenged birds had lower ileum pH compared to the unchallenged birds at d 16 and 21. 5. Results of this study suggest that AXOS appeared to be efficacious prebiotics, as highlighted by improvements in feed conversion ratio and increased SCFA production. Future studies are warranted to elucidate the types of AXOS that are most active against NE and the mechanisms by which different levels of AXOS enhance bird performance.