Host responses to Clostridium perfringens challenge in a chicken model of chronic stress

Background

This study utilized a chicken model of chronic physiological stress mediated by corticosterone (CORT) administration to ascertain how various host metrics are altered upon challenge with Clostridium perfringens. Necrotic enteritis (NE) is a disease of the small intestine of chickens incited by C. perfringens, which can result in elevated morbidity and mortality. The objective of the current study was to investigate how physiological stress alters host responses and predisposes birds to subclinical NE.

Results

Birds administered CORT exhibited higher densities of C. perfringens in their intestine, and this corresponded to altered production of intestinal mucus. Characterization of mucus showed that C. perfringens treatment altered the relative abundance of five glycans. Birds inoculated with C. perfringens did not exhibit evidence of acute morbidity. However, histopathologic changes were observed in the small intestine of infected birds. Birds administered CORT showed altered gene expression of tight junction proteins (i.e. CLDN3 and CLDN5) and toll-like receptors (i.e. TLR2 and TLR15) in the small intestine. Moreover, birds administered CORT exhibited increased expression of IL2 and G-CSF in the spleen, and IL1β, IL2, IL18, IFNγ, and IL6 in the thymus. Body weight gain was impaired only in birds that were administered CORT and challenged with C. perfringens.

Conclusion

CORT administration modulated a number of host functions, which corresponded to increased densities of C. perfringens in the small intestine and weight gain impairment in chickens. Importantly, results implicate physiological stress as an important predisposing factor to NE, which emphasizes the importance of managing stress to optimize chicken health.

Feeding of yeast cell wall extracts during a necrotic enteritis challenge enhances cell growth, survival and immune signaling in the jejunum of broiler chickens

Necrotic enteritis (NE) is one of the most common and costly diseases in the modern broiler industry, having an estimated economic impact of $6 billion dollars annually. Increasing incidents of NE have resulted from restrictions on the use of antibiotic feed additives throughout the broiler industry. As such, finding effective antibiotic alternatives has become a priority. In this study, an experimental model of NE was used, comprising a commercial infectious bursal disease virus vaccine and Clostridium perfringens (C. perfringens) inoculation. Yeast cells wall (YCW) components, β-glucan (BG), and mannoproteins (MPTs) were evaluated for their effects on disease development. Chicken-specific immunometabolic kinome peptide arrays were used to measure differential phosphorylation between control (uninfected), challenged (infected), and challenged and treated birds in duodenal, jejunal, and ileal tissues. Treatment groups included crude YCW preparation, BG, MPT, or BG+MPT as feed additives. Data analysis revealed kinome profiles cluster predominantly by tissue, with duodenum showing the greatest relative signaling and jejunum showing the greatest response to treatment. BG, MPT, and BG+MPT cluster together, separate from controls and challenge birds in each tissue. Changes in signaling resulting from the treatments were observed in cell growth and survival responses as well as immune responses. None of the treatments of disease challenge returned the profiles to control-like. This is attributable to immune modulation and metabolic effects of the treatments generating distinct profiles from control. Importantly, all the treatments are distinct from the challenge group despite being challenged themselves. Only BG+MPT treatment had a significant effect on bird weight gain compared with the NE challenge group, and this treatment had the greatest impact on gut tissue signaling in all segments. The signaling changes elicited by BG+MPT during an NE challenge were increased cell growth and survival signaling, reducing cell death, apoptosis and innate inflammatory responses, and generating compensatory signaling to reduce disease severity.

Effect of Antibiotic, Phytobiotic and Probiotic Supplementation on Growth, Blood Indices and Intestine Health in Broiler Chicks Challenged with Clostridium perfringens

Simple Summary

Necrotic enteritis is one of the most important economic issues in the poultry industry, associated with sudden death rates of up to 50%. However, there is limited information on the role of probiotics and/or phytobiotic compounds on the treatment and prevention of Clostridium perfringens infections in broiler chicks. This study aimed to assess the effects of probiotic compounds (Maxus, CloStat, Sangrovit Extra, CloStat + Sangrovit Extra and Gallipro Tech) on the growth performance, blood biochemistry and intestinal health of broiler chicks in vivo. The results demonstrated that the inclusion of probiotic and/or phytobiotic compounds has a positive effect on performance, blood constituents, liver histopathology, intestinal morphology and histopathology. Furthermore, a notable reduction in both lesion scores was observed when probiotics and phytobiotics alone or in combination were included in the diets.

Abstract

This study evaluated the effects of feed additives on the growth, blood biochemistry and intestinal health of broiler chicks. A total of 378 of broiler chicks (Ross 308) were randomly allotted to seven groups. Chicks were fed a basal diet with 0.0 (control negative), 0.0 (control positive), 0.1, 0.5, 0.12, 0.5 + 0.12 and 0.2 g Kg⁻¹ of Maxus, CloStat, Sangrovit Extra, CloStat + Sangrovit Extra and Gallipro Tech, respectively for 35 days. After 15 days, the chicks were inoculated with Clostridium perfringens. All feed additives were found to enhance growth performance and feed efficiency. The best feed conversion ratio was found in the Negative Control, CloStat + Sangrovit Extra and Gallipro Tect groups, respectively. A notable increase in villus length, total villus area, small intestine weight, ilium weight and total lesion score was found in chicks supplemented with Bacillus subtilis. Besides, the dietary inclusion of phytobiotic compounds showed potential in reducing the serum Alanine aminotransferase (ALT) concentration and increasing the glucose levels. All intestine and liver histopathological signs were reduced in chicks fed a probiotic-supplemented diet. Our findings indicate that supplementation with probiotics and phytobiotics alone or in combined form can be used to enhance performance, intestine health and blood constituents against C. perfringens infection in broiler chicks.

Developing an experimental necrotic enteritis model in turkeys - the impact of Clostridium perfringens, Eimeria meleagrimitis and host age on frequency of severe intestinal lesions

BACKGROUND

Necrotic enteritis is a significant problem to the poultry industry globally and, in Norway up to 30% of Norwegian turkey grow-outs can be affected. However, despite an awareness that differences exist between necrotic enteritis in chickens and turkeys, little information exists concerning the pathogenesis, immunity, microbiota or experimental reproduction of necrotic enteritis in turkeys. In particular, it is important to determine the appearance of the gross lesions, the age dependency of the disease and the role of netB toxin of Clostridium perfringens. To this end, we report our findings in developing an in vivo experimental model of necrotic enteritis in turkeys.

RESULTS

A four tier (0-3) scoring system with clearly defined degrees of severity of macroscopic intestinal lesions was developed, based on 2312 photographic images of opened intestines from 810 B.U.T. 10 or B.U.T. Premium turkeys examined in nine experiments. Loss of macroscopically recognizable villi in the anterior small intestine was established as the defining lesion qualifying for a score 3 (severe intestinal lesions). The developed scoring system was used to identify important factors in promoting high frequencies of turkeys with severe lesions: a combined Eimeria meleagrimitis and Clostridium perfringens challenge, challenge at five rather than 3 weeks of age, the use of an Eimeria meleagrimitis dose level of at least 5000 oocysts per bird and finally, examination of the intestines of 5-week-old turkeys at 125 to 145 h after Eimeria meleagrimitis inoculation. Numbers of oocysts excreted were not influenced by Clostridium perfringens inoculation or turkey age. Among three different lesion score outcomes tested, frequency of severe lesions proved superior in discriminating between impact of four combinations of Clostridium perfringens inoculation and turkey age at challenge.

CONCLUSIONS

This study provides details for the successful establishment of an in vivo model of necrotic enteritis in turkeys.

Protected Blend of Organic Acids and Essential Oils Improves Growth Performance, Nutrient Digestibility, and Intestinal Health of Broiler Chickens Undergoing an Intestinal Challenge

The growing restriction of antibiotic growth promoters (AGP) use in farming animals has raised a concern regarding the viability of the animal production system. In this new context, feed additives with proven positive impact on intestinal health may be used as strategy to avoid losses on performance. The aim of this study was to evaluate the effects of a protected blend of organic acids and essential oils [P(OA+EO)] on growth performance, nutrient digestibility, and intestinal health of broiler chickens. A total of 1,080 Cobb × Cobb 500 male broilers were randomly distributed in four treatments with 10 replicates (27 birds/each). Treatments were as follow: non-challenged control; challenged control; AGP (enramycin at 10 g/t); and P(OA+EO) at 300 g/t. All birds on challenged groups were challenged with Eimeria spp. at 1 day and with Clostridium perfringens at 11, 12, and 13 days. Body weight gain (BWG), feed intake and feed conversion ratio (FCR) were evaluated until 42 days. At 17 days, one bird per pen was orally gavaged with fluorescein isothiocyanate-dextran (FITC-d) and blood samples were collected for FITC-d detection to assess intestinal permeability. At 21 days, apparent ileal nutrient and energy (IDE) digestibility, intestinal macroscopic and histologic alterations (ISI) and, expression of mucin2 (MUC2), claudin1 (CLDN1), and occludin (OCLN) genes in the jejunum were evaluated. From 1 to 42 days, birds from the non-challenged and P(OA+EO) groups had greater (P < 0.001) BWG compared to challenged control and AGP groups. The challenged control group presented the worst FCR (P < 0.001). IDE was 106 kcal/kg greater when broilers were fed P(OA+EO) compared to the challenged control group. Broilers supplemented with P(OA+EO) had improved intestinal integrity with lower blood FITC-d concentration and ISI scores, and greater expression of MUC2, CLDN1, and OCLN genes compared to the challenged control group (P < 0.05). In conclusion, the P(OA+EO) and the AGP led to increased growth performance, nutrient digestibility and intestinal health of challenged broilers. A marked difference occurred in favor of the P(OA+EO), suggesting that this blend may be used to improve intestinal health and broiler growth performance in AGP free programs.

MicroRNA gga-miR-10a-mediated transcriptional regulation of the immune genes in necrotic enteritis afflicted chickens

miRNAs are involved in both adaptive and innate immune systems of host animals; and play important roles in many immune-related pathways. The systemic biological roles of gga-miR-10a-5p chicken microRNA on immune response were investigated in two necrotic enteritis (NE) induced chicken lines, Marek's disease (MD) resistant (line 6.3) and susceptible (line 7.2). We determined the expression patterns of gga-miR-10a in the intestinal mucosal layer of chickens upon NE induction, and identified the target genes (MyD88, and SKP1) related to the host immune response to pathogens. We found that gga-miR-10a expression in the intestinal mucosal layer of MD-resistant chicken line 6.3 gga-miR-10a was significantly down-regulated (p < 0.01) during NE. Overexpression analysis of gga-miR-10a and reporter gene analysis using a wild- or mutant-type MyD88 3' untranslated region (3' UTR)-luciferase construct in chicken macrophage cell line HD11 and chicken fibroblast cell line OU2 showed that gga-miR-10a acted as a direct translational repressor of MyD88 by targeting the 3' UTR of this gene. Furthermore, miR-10a indirectly negatively influenced the expression of signaling molecules related to the MyD88-dependent pathway, including TRAF6, TAK1, and NF-κB1 at both transcriptional and translational levels. Downstream of the MyD88-dependent pathway, several proinflammatory cytokines such as IL-1β, IFN-γ, IL-12p40, TNFSF15, and LITAF were down-regulated by overexpression of gga-miR-10a. These results suggest that gga-miR-10a is an important regulator of the Toll-like receptor signaling pathway. The findings of this study improve our understanding of the biological functions of miR-10a and the mechanisms underlying the TLR signaling pathway upon NE afflicted chickens, as well improving the overall understanding of the immune system function in domestic animals.

Antibacterial activity of Bacillus species-derived surfactin on Brachyspira hyodysenteriae and Clostridium perfringens

Swine dysentery and necrotic enteritis are a bane to animal husbandry worldwide. Some countries have already banned the use of antibiotics as growth promoters in animal production. Surfactin is a potential alternative to antibiotics and antibacterial agents. However, the antibacterial activity of Bacillus species-derived surfactin on Brachyspira hyodysenteriae and Clostridium perfringens are still poorly understood. In the current study, the antibacterial effects of surfactin produced from Bacillus subtilis and Bacillus licheniformis on B. hyodysenteriae and C. perfringens were evaluated. Results showed that multiple surfactin isoforms were detected in B. subtilis, while only one surfactin isoform was detected in B. licheniformis fermented products. The surfactin produced from B. subtilis exhibited significant antibacterial activity against B. hyodysenteriae compared with surfactin produced from B. licheniformis. B. subtilis-derived surfactin could inhibit bacterial growth and disrupt the morphology of B. hyodysenteriae. Furthermore, the surfactin produced from B. subtilis have the highest activity against C. perfringens growth. In contrast, B. licheniformis fermented product-derived surfactin had a strong bacterial killing activity against C. perfringens compared with surfactin produced from B. subtilis. These results together suggest that Bacillus species-derived surfactin have potential for development as feed additives and use as a possible substitute for antibiotics to prevent B. hyodysenteriae and C. perfringens-associated disease in the animal industry.

In Vitro Antimicrobial Activities of Organic Acids and Their Derivatives on Several Species of Gram-Negative and Gram-Positive Bacteria

The objective of this study was to determine the in vitro antimicrobial activity of several organic acids and their derivatives against Gram-positive (G+) and Gram-negative (G-) bacteria. Butyric acid, valeric acid, monopropionin, monobutyrin, monovalerin, monolaurin, sodium formate, and ProPhorce-a mixture of sodium formate and formic acid (40:60 w/v)-were tested at 8 to 16 concentrations from 10 to 50,000 mg/L. The tested bacteria included G- bacteria (Escherichia coli, Salmonella enterica Typhimurium, and Campylobacter jejuni) and G+ bacteria (Enterococcus faecalis, Clostridium perfringens, Streptococcus pneumoniae, and Streptococcus suis). Antimicrobial activity was expressed as minimum inhibitory concentration (MIC) of tested compounds that prevented growth of tested bacteria in treated culture broth. The MICs of butyric acid, valeric acid, and ProPhorce varied among bacterial strains with the lowest MIC of 500-1000 mg/L on two strains of Campylobacter. Sodium formate at highest tested concentrations (20,000 mg/L) did not inhibit the growth of Escherichia coli, Salmonella Typhimurium, and Enterococcus faecalis, but sodium formate inhibited the growth of other tested bacteria with MIC values from 2000 to 18,800 mg/L. The MIC values of monovalerin, monolaurin, and monobutyrin ranged from 2500 to 15,000 mg/L in the majority of bacterial strains. Monopropionin did not inhibit the growth of all tested bacteria, with the exception that the MIC of monopropionin was 11,300 mg/L on Clostridia perfringens. Monolaurin strongly inhibited G+ bacteria, with the MIC value of 10 mg/L against Streptococcus pneumoniae. The MIC tests indicated that organic acids and their derivatives exhibit promising antimicrobial effects in vitro against G- and G+ bacteria that are resistant to antimicrobial drugs. The acid forms had stronger in vitro antimicrobial activities than ester forms, except that the medium chain fatty acid ester monolaurin exhibited strong inhibitory effects on G+ bacteria.

Effect of different challenge models to induce necrotic enteritis on the growth performance and intestinal microbiota of broiler chickens

The objective of this study was to evaluate performance, diversity, composition, and predicted function of the intestinal microbiota of broilers raised under 3 different methods to induce necrotic enteritis (NE). The chicks in Experiments 1 and 2 were vaccinated against coccidiosis on day 1. Experiment 1: non-challenged and challenged birds were raised in floor pens with new litter and 58 birds/pen. The challenge consisted of Eimeria maxima inoculation on day 14 and Clostridium perfringens via water on days 18 to 19. Cecal microbiota was evaluated on days 18, 21, and 28. Experiment 2: non-challenged and challenged birds were raised in floor pens with recycled litter and 50 birds/pen. The challenge consisted of C. perfringens via feed from days 18 to 20. Ileal and cecal microbiota were evaluated on day 21. In Experiment 3, non-challenged and challenged birds were raised in battery cages with 8 birds/cage. Challenged birds were inoculated with E. maxima on day 14 and with C. perfringens on days 19 to 21. In the 3 experiments, ileal or cecal microbiota or both were analyzed through 16S rRNA sequencing. The performance of the birds was impaired in the 3 studies, regardless of the method used to induce NE. In Experiment 1, the microbiota did not significantly change across ages. In Experiment 2, α-diversity indices were lower in challenged vs. non-challenged birds in both ileal and cecal microbiota. The cecal microbiota composition and function was more affected than the ileal microbiota. In Experiment 3, Chao index (α-diversity) increased in challenged vs. non-challenged birds, and the composition of the ileal and cecal microbiota was not significantly affected. In conclusion, the overall feed conversion ratio was more affected in Experiment 3 (5.2, 11.1, and 30% for Experiments 1, 2, and 3, respectively), which also showed the highest degree of NE lesions. However, the largest variations of diversity and composition of the microbiota were observed in Experiment 2, when birds were raised in floor pens with reused litter, vaccinated against coccidiosis, and challenged with C. perfringens on days 19 to 21.

Administration of a Postbiotic Causes Immunomodulatory Responses in Broiler Gut and Reduces Disease Pathogenesis Following Challenge

With the reemergence of poultry diseases such as necrotic enteritis following the restriction of in-feed antibiotics, the search for antibiotic alternatives has become critically important. Postbiotics are non-viable bacterial products or metabolic byproducts from probiotic microorganisms that have positive effects on the host or microbiota. These are a promising alternative to antibiotics. Here, we describe the mechanism of action of a postbiotic in the context of a Clostridium perfringens (C. perfringens) challenge model. By using performance measurements and a peptide array kinome analysis, we describe the kinotypes and signal transduction changes elicited by the postbiotic with and without C. perfringens challenge. The postbiotic improves lesion scores, C. perfringens counts and mortality compared to challenge groups without the postbiotic, and it improves weight gain in the most severely challenged birds. The postbiotic predominantly affects the innate immune response and appears immunomodulatory. In the context of infection, it reduces the proinflammatory responses and generates a homeostatic-like response. This postbiotic is a viable alternative to antibiotics to improve poultry health in the context of C. perfringens pathogen challenge.

Dietary Non-Drug Feed Additive as an Alternative for Antibiotic Growth Promoters for Broilers During a Necrotic Enteritis Challenge

Necrotic enteritis, caused by Clostridium perfringens, is an enteric disease that leads to poor performance and increased mortality, resulting in significant economic losses in poultry production. This study evaluated the effects of a proprietary prebiotic, probiotic, and plant extract blend on performance of broilers during coccidiosis challenge leading to necrotic enteritis (NE). In total, 744 Cobb500 male broilers were randomly allocated to 3 treatments (8 replicates, 31 birds/pen) including, the negative control (NC) fed a basal diet; the positive control (PC) fed a basal diet with Virginiamycin; and the additive group fed basal diet with a blend of prebiotic, probiotic, and plant extract (BSN). A unique, naturally occurring NE model developed to mimic field conditions was implemented to challenge the birds. This model consists of spraying a concentrated commercial coccidiosis vaccine on litter and feed upon bird placement, which, in conjunction with the presence of C. perfringens spores in the environment, leads to the development of a NE outbreak one week post vaccine application. At the onset of NE on d7, three birds/pen were selected for scoring NE lesions. Body weight gain (BWG), feed intake (FI), and feed conversion ratio (FCR) were recorded on days 7, 14, 28, and 42. Carcass composition was assessed by dual energy X-ray absorptiometry (DXA) analysis on day 42. Dietary supplementation of BSN significantly (p < 0.05) improved FCR during starter and grower periods. Dietary treatments had no effect on NE lesions in the small intestine. DXA analysis revealed slightly higher lean content in BSN birds compared to NC. These results showed that dietary supplementation of the BSN blend significantly improved broilers performance during the early NE challenge phase, as well as in the grower period.

Evaluation of the Dietary Supplementation of a Formulation Containing Ascorbic Acid and a Solid Dispersion of Curcumin with Boric Acid against Salmonella Enteritidis and Necrotic Enteritis in Broiler Chickens

Two experiments were conducted to evaluate the effect of the prophylactic or therapeutic administration of a 0.1% mixture containing ascorbic acid and a solid dispersion of curcumin with polyvinylpyrrolidone and boric acid (AA-CUR/PVP-BA) against Salmonella Enteritidis (S. Enteritidis) in broiler chickens. A third experiment was conducted to evaluate the impact of the dietary administration of 0.1% AA-CUR/PVP-BA in a necrotic enteritis (NE) model in broiler chickens. The prophylactic administration of 0.1% AA-CUR/PVP-BA significantly decreased S. Enteritidis colonization in cecal tonsils (CT) when compared to the positive control group (PC, p < 0.05). The therapeutic administration of 0.1% AA-CUR/PVP-BA significantly reduced the concentration of S. Enteritidis by 2.05 and 2.71 log in crop and CT, respectively, when compared with the PC on day 10 post-S. Enteritidis challenge. Furthermore, the serum FITC-d concentration and total intestinal IgA levels were also significantly lower in chickens that received 0.1% AA-CUR/PVP-BA. Contrary, the PC group showed significantly higher total intestinal IgA levels compared to the negative control or AA-CUR/PVP-BA groups in the NE model. However, 0.1% AA-CUR/PVP-BA showed a better effect in reducing the concentration of S. Enteritidis when compared to the NE model. Further studies with higher concentration of AA-CUR/PVP-BA into the feed to extend these preliminary results are currently being evaluated.

Heat stress, Eimeria spp. and C. perfringens infections alone or in combination modify gut Th1/Th2 cytokine balance and avian necrotic enteritis pathogenesis

Information on the dynamics of the chicken immune system during bacterial or parasite challenge in the presence or absence of stressful situations may provide a better understanding of the complex mechanisms behind these diseases. Necrotic enteritis (NE) had been controlled previously by the proper use of antimicrobial agents; however, more recently, NE has reemerged in many countries. The imposed restrictions on antimicrobial use and/or the intensive productive programs implemented by producers are challenges the birds, leading to large host adaptive responses that in many instances are like those elicited by stressors. This study analyses the effects of heat stress on Th1/Th2 cytokine balance, pathological features, and Toll-like receptor expression in the small intestine of broiler chickens infected with Clostridium perfringens type A in the presence or absence of Eimeria spp. co-infection. This co-infection model was experimentally used because it reproduces the findings commonly observed in the field during avian NE. For this purpose, broiler chickens infected with C. perfringens and/or Eimeria spp. were reared in isolator chambers subjected or not to heat stress intermittently. It was observed that heat stress directs the expression of Th2-type cytokines, increases Toll-like receptor 4 expression in the intestine and reduces the disease severity induced by Eimeria spp. and C. perfringens infections alone or in combination, most likely as a consequence of stress-induced changes in brain-gut axis activity.

Heat Stress Modulates Brain Monoamines and Their Metabolites Production in Broiler Chickens Co-Infected with Clostridium perfringens Type A and Eimeria spp

Heat stress has been related to the impairment of behavioral and immunological parameters in broiler chickens. However, the literature is not clear on the involvement of neuroimmune interactions in a heat stress situation associated with bacterial and parasitic infections. The present study evaluated the production of monoamines and their metabolites in brain regions (rostral pallium, hypothalamus, brain stem, and midbrain) in broiler chickens submitted to chronic heat stress and/or infection and co-infection with Eimeria spp. and Clostridium perfringens type A. The heat stress and avian necrotic enteritis (NE) modulated the neurochemical profile of monoamines in different areas of the central nervous system, in particular, those related to the activity of the hypothalamus-hypophysis-adrenal (HPA) axis that is responsible for sickness behavior. C. perfringens and/or Eimeria infection, heat stress increased 5-hydroxytryptamine (5-HT), 4,4 dihydroxyphenylacetic acid (DOPAC), and DOPAC/dopamine (DA) in the rostral pallium; 3-methoxy-4-hydroxyphenylethylene glycol (MHPG), homovanillic acid (HVA), HVA/DA, DOPAC/DA, and 5-hydroxyindoleacetic acid (5-HIAA)/5-HT in the hypothalamus; MHPG, 5-HIAA/5-HT, DOPAC/DA, and HVA/DA in the midbrain; and MHPG, DOPAC, HVA, HVA/DA, DOPAC/DA, and 5-HIAA/5-HT in the brainstem. Heat stress decreased noradrenaline + norepinephrine (NOR + AD) in all brain regions analyzed; 5-HT in the hypothalamus, midbrain, and brainstem; and DA in the midbrain. The results also showed the existence and activity of the brain-gut axis in broiler chickens. The brain neurochemical profile and corticosterone production are consistent with those observed in chronic stressed mammals, in animals with sickness behavior, and an overloading of the HPA axis.

Pleiotropic Anti-Infective Effects of Defensin-Derived Antimicrobial Compounds

We identified low-molecular weight compounds derived from the antimicrobial peptide human neutrophil peptide-1 that bind to Lipid II, an essential precursor of bacterial cell wall biosynthesis. These compounds act as antibacterials on multiple biosynthesis pathways with specificity against gram-positive organisms. Here, we have tested a small subset of our most promising leads against the bacterium Clostridium perfringens and sporozoites of Eimeria tenella, an intracellular protozoan parasite that causes intestinal disease in poultry. We found one compound, 1611-0203 (2-{2,3,5,6-tetrafluoro-4-[2,3,5,6-tetrafluoro-4-(2-hydroxyphenoxy)phenyl]phenoxy}phenol), specifically to inhibit growth of both agents out of all compounds tested. Additionally, compound 1611-0203 inhibits Staphylococcus aureus and Enterococcus spp. Mechanism-of-action studies further reveal that 1611-0203 affects cell wall biosynthesis and inhibits additional biosynthetic pathways. Combined, our results indicate that compounds such as 1611-0203 have therapeutic potential to act as anti-infectives against various organisms simultaneously.

Histological parameters to evaluate intestinal health on broilers challenged with Eimeria and Clostridium perfringens with or without enramycin as growth promoter

The maintenance of integrity of the gastrointestinal tract is an important aspect for animal productivity, since it is able to absorb nutrients more efficiently and serves as a barrier against microorganisms. To control agents detrimental to intestinal integrity, growth-promoting antibiotics (AGP) are used, which reduce the number of toxin-producing microorganisms in the intestinal lumen, acting as anti-inflammatory agents. There is a demand for restriction of use of AGP in animal feed, but there are few studies showing what parameters we should observe to search for alternative additives. The aim of this study was to establish histological parameters that explain the effect of enramycin as growth promoter on intestinal health in broilers challenged with Eimeria and Clostridium perfringens. The zootechnical performance and the histology by I See Inside (ISI) methodology were evaluated on liver and ileum samples. Chickens challenged without AGP have the worst BWG, FCR, and histological ISI score (ISI score 9) in the ileum compared to non-challenged (ISI score 5). The use of enramycin on challenged group significantly minimized the ISI score in the ileum at 21 and 28 d (ISI score 7.4 and 8.0, respectively) compared with the challenged group not fed with enramycin (ISI score 9.2 and 9.9, respectively), associated with reduced lamina propria thickness and inflammatory cell infiltration. We suggest these 2 histological parameters as a standard to compare products for gut health.

A Comparative Review on Microbiota Manipulation: Lessons From Fish, Plants, Livestock, and Human Research

During recent years the impact of microbial communities on the health of their host (being plants, fish, and terrestrial animals including humans) has received increasing attention. The microbiota provides the host with nutrients, induces host immune development and metabolism, and protects the host against invading pathogens (1-6). Through millions of years of co-evolution bacteria and hosts have developed intimate relationships. Microbial colonization shapes the host immune system that in turn can shape the microbial composition (7-9). However, with the large scale use of antibiotics in agriculture and human medicine over the last decades an increase of diseases associated with so-called dysbiosis has emerged. Dysbiosis refers to either a disturbed microbial composition (outgrowth of possible pathogenic species) or a disturbed interaction between bacteria and the host (10). Instead of using more antibiotics to treat dysbiosis there is a need to develop alternative strategies to combat disturbed microbial control. To this end, we can learn from nature itself. For example, the plant root (or "rhizosphere") microbiome of sugar beet contains several bacterial species that suppress the fungal root pathogen Rhizoctonia solani, an economically important fungal pathogen of this crop (11). Likewise, commensal bacteria present on healthy human skin produce antimicrobial molecules that selectively kill skin pathogen Staphylococcus aureus. Interestingly, patients with atopic dermatitis (inflammation of the skin) lacked antimicrobial peptide secreting commensal skin bacteria (12). In this review, we will give an overview of microbial manipulation in fish, plants, and terrestrial animals including humans to uncover conserved mechanisms and learn how we might restore microbial balance increasing the resilience of the host species.

Dietary L-glutamine supplementation improves growth performance, gut morphology, and serum biochemical indices of broiler chickens during necrotic enteritis challenge

Necrotic enteritis (NE) causes significant economic losses in the broiler chicken industry, especially in birds raised without in-feed antibiotics. L-glutamine (Gln) is an amino acid that may compensate for metabolic losses from infection and improve the intestinal development. This study investigated the effects of dietary Gln (10 g/kg) supplementation on growth performance, intestinal lesions, jejunum morphology, and serum biochemical indices of broiler chickens during NE challenge. The study employed a factorial arrangement of treatments with factors: NE challenge, no or yes; dietary Gln inclusion, 0 g/kg in starter (S), d 0 to 10, grower (G) d 10 to 24, and finisher (F) d 24 to 35; 10 g/kg in S, G, F, or 10 g/kg in S, G only. Each treatment was replicated in 6 floor pens with 17 birds per pen as the experimental unit for performance and 2 birds for other measurements. Challenge significantly reduced bird performance, increased incidence of intestinal lesions, and affected intestinal development and serum biochemical indices. Regardless of challenge, Gln supplementation increased gain (P < 0.05), feed intake (P < 0.05), and decreased FCR (P < 0.05) on d 24. On d 35, Gln improved gain (P < 0.05) and FCR (P < 0.001) whereas withdrawing Gln from finisher tended to diminish the beneficial effect on weight gain but not FCR. Dietary Gln reduced lesion scores in the jejunum (P < 0.01) and ileum (P < 0.01) in challenged birds. On d 16, Gln increased villus height to crypt depth ratio in unchallenged birds (P < 0.05) and reduced crypt depth of challenged birds on d 24 (P < 0.05). Regardless of challenge, supplementation with Gln reduced crypt depth on d 16 (P < 0.05), and increased villus height (P < 0.01) and the villus height to crypt depth ratio (P < 0.001) on d 24. Dietary Gln lowered serum uric acid level regardless of challenge (P < 0.05). The current study indicates that dietary Gln alleviates adverse effects of NE and may be useful in antibiotic-free diets.

Optimization of surfactin production from Bacillus subtilis in fermentation and its effects on Clostridium perfringens-induced necrotic enteritis and growth performance in broilers

Bacillus species are commonly used as probiotics in the poultry feed industry for preventing infectious diseases and improving productivity by altering gastrointestinal microbiota. The growth parameters of Bacillus subtilis for surfactin production in fermentation and the benefits of surfactin on broiler chickens remain unclear. In this study, we examined the growth parameters of B. subtilis in fermentation and evaluated the effects of surfactin from B. subtilis-fermented products on Clostridium perfringens-induced necrotic enteritis and growth performance in broilers. Results showed that the highest viable biomass of B. subtilis was observed at 10% molasses and 2% yeast supplementation during fermentation. The 4- and 6-day fermented B. subtilis products were heat-, acid- and bile-resistant. Furthermore, the 4-day fermented B. subtilis products with the highest surfactin concentration showed the maximal antimicrobial activity against pathogens, including Escherichia coli, Staphylococcus aureus, Salmonella typhimurium and C. perfringens. Dietary B. subtilis-fermented product supplementation in broilers significantly improved intestinal morphology and necrotic lesions under C. perfringens challenge. Bacillus subtilis treatments could enhance broiler productivity, as well as promote bone quality and intestinal morphology. These results together indicate that B. subtilis-fermented products containing surfactin have potential for the development as feed additives and use as possible substitutes for antibiotics to treat C. perfringens in the poultry industry.

Effects of commercial organic acid blends on male broilers challenged with E. coli K88: Performance, microbiology, intestinal morphology, and immune response

This study assessed the effects of 3 commercial organic acid (OA) preparations on growth performance, intestinal morphology, cecal microbiology, and immunity of Escherichia coli K88-challenged (ETEC) broiler chickens. One thousand one-day-old male broiler chickens were divided into 8 treatments of 5 replicate pens: Negative control (NC) birds received a basal diet (BD) and were not challenged with ETEC; positive control (PC) birds fed the BD and challenged with ETEC; BD + 0.2% (S1) or 0.4% (S2) of an OA mixture (Salkil) from one to 35 d; BD + 0.1, 0.075, and 0.05% (O1) of another OA mixture (Optimax) in the starter (one to 10 d), grower (11 to 24 d), and finisher (25 to 35 d) diets, respectively, or 0.1% (O2) from one to 35 d; BD + 0.07, 0.05, and 0.05% (P1) or 0.1, 0.07, and 0.05% (P2) of a further OA mixture (pHorce) in the starter, grower, and finisher diets, respectively. All groups (not NC) were challenged with one mL of ETEC (1 × 108 cfu/mL) at 7 d of age. The 3 OA mixtures are commercial formic and propionic acid preparations. Birds challenged with ETEC (PC) had reduced (P < 0.05) growth performance, ileal morphological parameters (not crypt depth, which was increased), cecal lactobacilli, and immune responses, and increased cecal E. coli compared with unchallenged, NC birds. The addition of OA to the diets of ETEC challenged birds (S1-P2) either numerically or significantly (P < 0.05) improved growth performance, ileal morphology and immune responses, increased cecal lactobacilli, and reduced cecal E. coli. For most OA additions, the assessed parameters were generally enhanced to equivalence to NC birds. The results suggest that dietary OA supplementation can enhance the growth performance, ileal morphology, cecal microbiota, and immunity of ETEC-challenged broilers to an extent that, under such circumstances, the formulations used in this study provided similar performance and assessed parameters as non-challenged birds.

Growth-Promoting and Antioxidant Effects of Magnolia Bark Extract in Chickens Uninfected or Co-Infected with Clostridium perfringens and Eimeria maxima as an Experimental Model of Necrotic Enteritis

BACKGROUND

Magnolia tree bark has been widely used in traditional Asian medicine. However, to our knowledge, no studies have been reported investigating the effects of dietary supplementation with magnolia bark extract in chickens.

OBJECTIVE

We tested the hypothesis that dietary supplementation of chickens with a Magnolia officinalis bark extract would increase growth performance in uninfected and Eimeria maxima/Clostridium perfringens co-infected chickens.

METHODS

A total of 168 chickens were fed from hatch either a standard diet or a diet supplemented with 0.33 mg or 0.56 mg M. officinalis bark extract/kg (M/H low or M/H high, respectively) from days 1 to 35. At day 14, half of the chickens were orally infected with E. maxima, followed by C. perfringens infection at day 18 to induce experimental avian necrotic enteritis. Daily feed intake, feed conversion ratio, body weight gain, and final body weight were measured as indicators of growth performance. Serum α1-acid glycoprotein (AGP) concentrations were measured as an indicator of systemic inflammation, and intestinal lesion scores were determined as a marker of disease progression. Transcript levels for catalase, heme oxygenase 1, and superoxide dismutase in the intestine, liver, spleen, and skeletal muscle were measured as indicators of antioxidant status.

RESULTS

Growth performance increased between days 1 and 35 in uninfected and E. maxima/C. perfringens co-infected chickens fed M/H-low or M/H-high diets compared with unsupplemented controls. Gut lesion scores were decreased, whereas AGP concentrations were unchanged, in co-infected chickens fed magnolia-supplemented diets compared with unsupplemented controls. In general, transcripts for antioxidant enzymes increased in chickens fed magnolia-supplemented diets compared with unsupplemented controls, and significant interactions between dietary supplementation and co-infection were observed for all antioxidant enzyme transcript levels.

CONCLUSION

Magnolia bark extract might be useful for future development of dietary strategies to improve poultry health, disease resistance, and productivity without the use of antibiotic growth promoters.

Genetics and genomics of susceptibility and immune response to necrotic enteritis in chicken: a review

Global poultry production is facing many challenges and is currently under pressure due to the presence of several diseases like Necrotic Enteritis (NE). It is estimated that NE-caused global economic losses has increased from 2 billion to 6 billion US$ in 2015 because it is not easy to diagnose and control disease at the earlier stage of occurrence. Additionally, ban on the in-feed antibiotics and some other genetic and non-genetic predisposing factors affect the occurrence of the disease. Though the incidence of the disease can be reduced by minimizing the predisposing factors and through immunization of birds but there is no single remedy to control the disease. Therefore, we suggest that there is need to find out the genetic variants that could help to select the birds resistant to NE. The current review details the pertinent features about the genetic and genomics of susceptibility and immune response of birds to Necrotic Enteritis. We report here the list of candidate gene reported for their involvement with the susceptibility and/or resistance to the disease. However, most of these genes are involved in immune-related functions. For better understanding of the role of Clostridium perfringens and its toxins in the pathogenesis of disease there is need to unveil the association between any specific genetic variation and clinical status of NE. However, the presence of substantial genetic variations among different breeds/strains of chicken shows that it is possible to develop broiler strain with genetic resistant against NE. It would help in the cost-effective and sustainable production of safe broiler meat.

The role of host genetic factors and host immunity in necrotic enteritis

The increasing number of legislative restrictions and the voluntary withdrawal of antibiotic growth promoters worldwide will continue to impact poultry health and production. The rising incidence of Clostridium infections and development of necrotic enteritis (NE) in commercial chickens has been associated with the withdrawal of antibiotics. High-throughput genomic analysis of intestinal tissues from NE-afflicted chickens showed alterations in the local immunity and gut microbiota. Therefore, a better understanding of host- and environmentally related factors on Clostridium perfringens infections will be necessary for the development of effective sustainable strategies aimed to reduce the negative consequences of NE. In this short review, we summarize the current knowledge on the role of host genomics and immunity in NE. The limited progress in understanding the complexity of host-pathogen interactions in NE underscores the urgent need for more fundamental research in host immunity against Clostridium pathogens in order to develop effective control strategies against NE.

Experimental reproduction of necrotic enteritis in chickens: a review

This review discusses key factors important in successful experimental reproduction of necrotic enteritis (NE) in chickens, and how these factors can be adjusted to affect the severity of the lesions induced. The critical bacterial factor is the need to use virulent, netB-positive, strains of Clostridium perfringens; disease severity can be enhanced by using netB-positive C. perfringens strains that are also tpeL-positive, by the use of young rather than old broth cultures, and by the number of days of inoculation and the number of bacteria used. Use of cereals rich in non-starch polysaccharides can enhance disease, as does use of animal proteins. Administration of coccidia, including coccidial vaccines, combined with netB-positive C. perfringens, increases the severity of experimentally-induced NE. Dietary manipulation may be less important in coccidia-based models since the latter are so effective. Disease scoring systems and welfare considerations are discussed.

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.

Probiotic Enhanced Intestinal Immunity in Broilers against Subclinical Necrotic Enteritis

Along with banning of antibiotics, necrotic enteritis (NE), especially subclinical NE (SNE) whereby no clinical signs are present in chicks, has become one of the most threatening problems in poultry industry. Therefore, increasing attention has been focused on research and application of effective probiotic strains, as an alternative to antibiotics, to prevent SNE in broilers. In the present study, we evaluated the effects of Lactobacillus johnsonii BS15 on the prevention of SNE in broilers. Specifically, assessment determined the growth performance and indexes related to intestinal mucosal immunity in the ileum and cecal tonsil of broilers. A total of 300 1-day-old Cobb 500 chicks were randomly distributed into the following 5 groups: control group (fed with basal diet + de Man, Rogosa, and Sharpe liquid medium [normal diet]), SNE group (normal diet), BS15 group (basal diet + 1 × 10⁶ colony-forming units BS15/g as fed [BS15 diet]), treatment group (normal diet [days 1-28] + BS15 diet [days 29-42]), and prevention group (BS15 diet [days 1-28] + normal diet [days 29-42]) throughout a 42-day experimental period. SNE infection was treated for all chicks in the SNE, BS15, treatment, and prevention groups. The present results demonstrated that BS15 supplementation of feeds in BS15 and prevention groups exerted a positive effect on preventing negative influences on growth performance; these negative influences included low body weight gain and increased feed conversion ratio caused by SNE. Although no changes were detected in all determined indexes in cecal tonsils, BS15-treated broilers were free from SNE-caused damage in villi in the ileum. BS15 inhibited SNE-caused decrease in immunoglobulins in the ileum. In the lamina propria of ileum, T cell subsets of lymphocytes influenced by SNE were also controlled by BS15. BS15 affected antioxidant abilities of the ileum and controlled SNE-induced mitochondrion-mediated apoptosis by positively changing contents and/or mRNA expression levels of apoptosis-related proteins. These findings indicate that BS15 supplementation may prevent SNE-affected growth decline mainly through enhancing intestinal immunity in broilers.

In ovo vaccination using Eimeria profilin and Clostridium perfringens NetB proteins in Montanide IMS adjuvant increases protective immunity against experimentally-induced necrotic enteritis

OBJECTIVE

The effects of vaccinating 18-day-old chicken embryos with the combination of recombinant Eimeria profilin plus Clostridium perfringens (C. perfringens) NetB proteins mixed in the Montanide IMS adjuvant on the chicken immune response to necrotic enteritis (NE) were investigated using an Eimeria maxima (E. maxima)/C. perfringens co-infection NE disease model that we previously developed.

METHODS

Eighteen-day-old broiler embryos were injected with 100 μL of phosphate-buffered saline, profilin, profilin plus necrotic enteritis B-like (NetB), profilin plus NetB/Montanide adjuvant (IMS 106), and profilin plus Net-B/Montanide adjuvant (IMS 101). After post-hatch birds were challenged with our NE experimental disease model, body weights, intestinal lesions, serum antibody levels to NetB, and proinflammatory cytokine and chemokine mRNA levels in intestinal intraepithelial lymphocytes were measured.

RESULTS

Chickens in ovo vaccinated with recombinant profilin plus NetB proteins/IMS106 and recombinant profilin plus NetB proteins/IMS101 showed significantly increased body weight gains and reduced gut damages compared with the profilin-only group, respectively. Greater antibody response to NetB toxin were observed in the profilin plus NetB/IMS 106, and profilin plus NetB/IMS 101 groups compared with the other three vaccine/adjuvant groups. Finally, diminished levels of transcripts encoding for proinflammatory cytokines such as lipopolysaccharide-induced tumor necrosis factor-α factor, tumor necrosis factor superfamily 15, and interleukin-8 were observed in the intestinal lymphocytes of chickens in ovo injected with profilin plus NetB toxin in combination with IMS 106, and profilin plus NetB toxin in combination with IMS 101 compared with profilin protein alone bird.

CONCLUSION

These results suggest that the Montanide IMS adjuvants potentiate host immunity to experimentally-induced avian NE when administered in ovo in conjunction with the profilin and NetB proteins, and may reduce disease pathology by attenuating the expression of proinflammatory cytokines and chemokines implicated in disease pathogenesis.

The safe enterocin DD14 is a leaderless two-peptide bacteriocin with anti-Clostridium perfringens activity

Enterococcus faecalis 14, a strain previously isolated from meconium, displayed activity against four Clostridium perfringens isolates when co-cultured on agar plates. The anti-Clostridium activity was ascribed to the production of enterocin DD14, which was subsequently purified. The minimum inhibitory concentration (MIC) of enterocin DD14 against one collection strain and one clinical C. perfringens strain was determined at 50 µg/mL. Furthermore, using the intestinal epithelial cell line IPEC-1, it was shown that E. faecalis 14 was not cytotoxic after 24 h of contact, and no cytotoxicity was observed when IPEC-1 cells were incubated with pure enterocin DD14 for 4 h. Enterocin DD14 was characterised using mass spectrometry and was shown to consist of two small proteins of 5200.74 Da and 5206.41 Da, respectively. The two peptides (DD14A and DD14B) have highly similar amino acid sequences and no signal peptide, which classifies enterocin DD14 as a class IIb leaderless two-peptide bacteriocin. The genes encoding DD14A and DD14B were sequenced and were shown to be 100% identical to other previously described enterocins MR10A and MR10B, in contrast to the producing strains, which are different. Consequently, the present in vitro study supports the potential of this E. faecalis 14 strain and/or its purified enterocin DD14 as putative anti-C. perfringens compounds in chickens.

An early feeding regime and a high-density amino acid diet on growth performance of broilers under subclinical necrotic enteritis challenge

Broilers that have early access to feed have been shown to have enhanced immune system and gut development and heightened resilience against necrotic enteritis (NE). This study examined the effect of early feeding a high amino acid density diet on performance of broilers under a sub-clinical NE challenge model. Ross 308 broilers (n = 576) were assigned to a 2 × 2 × 2 factorial design with 2 feeding regimes (feed access either within 6 h post-hatch or after 48 h post-hatch), 2 diets (control diet or the control diet with an additional 10% digestible amino acids [HAA]) and either presence or absence of NE challenge. Oral administrations of Eimeria species (d 9) and a field strain of Clostridium perfringens (d 14) were used to induce NE. Broiler performance was analysed at d 13, 23, 30 and 35. Intestinal lesion score and bacterial count were analysed on d 16. The NE challenge reduced overall bird performance and induced severe intestinal lesions, without causing notable mortality. At d 23 bird weight was significantly lower (P < 0.001) in the challenged birds compared with the unchallenged birds, but by d 30 the challenged birds had recovered and challenge no longer had an impact on bird performance. Birds fed the HAA diet had greater body weight by d 35 and heightened Lactobacillus content in the ileum at d 16 (P < 0.05). Birds that were fed the HAA diet after a period of fasting performed better in terms of feed conversion ratio (FCR) under challenge. The findings from this study suggest there are beneficial effects of feeding high amino acid diets to birds in response to external stresses, such as post-hatch fasting and subclinical NE.

Managing gut health without reliance on antimicrobials in poultry

It is well established that antimicrobials in animal feed enhance feed efficiency, promote animal growth and improve the quality of animal products. However, resistance development in bacterial populations, and hence consumer demand for products free of antimicrobial residues, has prompted efforts to develop alternatives that can replace antimicrobials without causing loss of productivity or product quality. One of the key barriers to complete withdrawal from antimicrobial use is microbial infection, for example, necrotic enteritis. There is much interest in using in-feed nutraceuticals such as prebiotics, probiotics, organic acids and plant extracts as alternatives to antimicrobials to create a healthy gastrointestinal environment and to prevent and treat enteric infections. Enzymes are generally used to alleviate anti-nutritional factors in feed, but there is growing awareness of their beneficial effects on the gastrointestinal environment, and consequently on gut health. An example of this is production of prebiotic xylo-oligosaccharides when xylanase is added to feed. This review discusses developments in alternatives to antimicrobials that can aid in managing gut health in a post-antimicrobial era, with particular reference to recent nutritional strategies.

An update on direct-fed microbials in broiler chickens in post-antibiotic era

In a post-antibiotic era, applying dietary alternatives to antibiotics into diets of chickens has become a common practice to improve the productivity and health status of chickens. It is generally accepted that direct-fed microbials (DFMs), defined as a source of viable, naturally occurring microorganisms, as an alternative to antibiotics, have a long history for their safe use and health benefit and are generally regarded for therapeutic, prophylactic and growth-promotion uses in poultry industry. It has been suggested that two primary modes of action by DFMs are balancing gut microbiota and modulating host immunity. Recent findings have suggested that gut microbiota plays an important role in developing immune system and maintaining the homeostasis of mature immune system in mammals and chickens. With the help of molecular and bioinformatics tools, it is now scientifically proven that gut microbiota is diverse, dynamic, and varies according to age, breed, diet composition, environment and feed additives. Broiler chickens are commonly raised on the floor with bedding materials, which facilitates the acquisition of microorganisms present in the bedding materials. Thus, it is expected that environmental factors, including the type of litter, influence host immunity in a positive or negative way. In this regard, adding DFMs into diets of chickens will affect host–microbe interaction, shaping host immunity towards increasing resistance of chickens to enteric diseases.

Analysis of Differentially Expressed Genes in Necrotic Enteritis-infected Fayoumi Chickens using RNA Sequencing

We identified and evaluated differentially expressed genes (DEGs) by RNA-Sequencing (RNA-Seq) in the intestinal mucosa of two Fayoumi chicken lines, M5.1 and M15.2, that are affected by necrotic enteritis (NE); these chicken lines share the same genetic background but have different major histocompatibility complexes. RNA-Seq generated over 49 and 40 million reads for lines M5.1 and M15.2, respectively. The alignment of these sequences with the Gallus gallus genome database revealed the expression of more than 14,500 genes in two lines, among which 581, 1270, and 1140 DEGs were detected when lines M15.2 and M5.1 were compared with the control and compared between each other. The analysis of all DEGs using the gene ontology database revealed annotations for 111 biological processes, 32 cellular components, and 17 molecular functions, and KEEG pathway mapping indicated that the DEGs were primarily involved in immunity, responses to various stimuli, and signal transduction. In addition, we analyzed 183 innate immune genes that were differentially expressed in NE-induced chicken lines, including 46 CD molecular genes, 89 immune-related genes, and 13 β-defensin genes with 3 lineage-specific duplications. Taken together, the transcriptional profiles showed that line M5.1 was more resistant to NE than line M15.2 and that differential gene expression patterns were associated with host genetic differences in resistance to NE. qRT-PCR and RNA-Seq analyses showed that all the genes examined had similar responses to NE (correlation coefficient R=0.84 to 0.88, p<0.01) in both lines. To the best of our knowledge, this is the first study that describes NE-induced DEGs using RNA-seq in two lines with different levels of susceptibility to NE. These results will lead to increased insights on NE disease resistance mechanisms and the role of host genes in the control of the host immune response.

In Vitro Selective Growth-Inhibitory Effect of 8-Hydroxyquinoline on Clostridium perfringens versus Bifidobacteria in a Medium Containing Chicken Ileal Digesta

Clostridium perfringens-induced necrotic enteritis is generally controlled by antibiotics. However, because of increasing antibiotic resistance, other antibacterial agents are required, preferably ones that do not affect the beneficial intestinal microbiota of the host. This study evaluated the in vitro selective growth-inhibitory effect of 8-hydroxyquinoline (8HQ) on C. perfringens vs. bifidobacteria in a medium containing chicken ileal digesta. Prior to the experiments, the minimum inhibitory concentrations of 8HQ and penicillin G were determined by broth microdilution assay. The minimum inhibitory concentration values of 8HQ for C. perfringens were 16-32 times lower than the values for bifidobacteria. Treatment of autoclaved and non-autoclaved chicken ileal digesta with 8HQ showed a selective anticlostridial effect. After incubation of C. perfringens with autoclaved ileal digesta for 3 h, all 8HQ concentrations tested (32-2048 μg/mL) significantly reduced C. perfringens bacterial count. In contrast, the same treatment had no or only a slight effect on bifidobacteria counts. Unlike 8HQ, penicillin G did not exhibit any selectivity. Similar results were obtained after incubation for 24 h. In non-autoclaved ileal digesta, all 8HQ concentrations tested significantly reduced C. perfringens bacterial counts after incubation for 30 min and 3 h, while no effect was observed on bifidobacteria. These results suggest that 8HQ may serve as a prospective veterinary compound for use against necrotic enteritis in poultry.

A chicken intestinal ligated loop model to study the virulence of Clostridium perfringens isolates recovered from antibiotic-free chicken flocks

Necrotic enteritis (NE) is a major problem in antibiotic-free (ABF) chicken flocks and specific strains of Clostridium perfringens are known to induce NE. The objective of this study was to develop a chicken intestinal ligated loop model in order to compare the virulence of various C. perfringens strains recovered from consecutive ABF flocks with and without NE. Intestinal loops were surgically prepared in 10 anaesthetized specific-pathogen-free chickens and alternately inoculated with C. perfringens isolates or brain heart infusion (BHI) media. Histological lesion scoring was performed for each loop. All strains from NE-affected flocks induced histological lesions compatible with NE whereas inoculation of loops with a commensal C. perfringens strain or BHI did not. Among inoculated strains, CP0994 (netB-positive and cpb2-positive) and CP-2003-1256 (netB-positive) demonstrated mean histological lesion scores significantly higher (P < 0.01) than those obtained with a commensal strain or BHI whereas strain CP1073 (netB-negative and cpb2-positive) induced intestinal lesions without significantly higher scores. In loops where villi were colonized by Gram-positive rods, significantly higher (P < 0.01) mean histological lesion scores were observed. This result supports the hypothesis that colonization of the intestinal mucosa by C. perfringens is a critical step in the pathogenesis of NE. Finally, we demonstrated the importance of controlling virulent C. perfringens strains in ABF chicken flocks as a highly virulent strain can be present in consecutive flocks with NE and possibly affect multiple flocks.

The antimicrobial peptide sublancin ameliorates necrotic enteritis induced by Clostridium perfringens in broilers

Sublancin is an antimicrobial peptide produced by 168 containing 37 amino acids. The objective of this study was to investigate its inhibitory efficacy against both in vitro and in vivo. In the in vitro study, we determined that sublancin had a minimum inhibitory concentration of 8 μM against , which was much higher than the antibiotic lincomycin (0.281 μM). Scanning electron microscopy showed that sublancin damaged the morphology of . The in vivo study was conducted on broilers for a 28-d period using a completely randomized design. A total of 252 chickens at 1 d of age were randomly assigned to 1 of 6 treatments including an uninfected control; an infected control; 3 infected groups supplemented with sublancin at 2.88, 5.76, or 11.52 mg activity/L of water; and an infected group supplemented with lincomycin at 75 mg activity/L of water (positive control). Necrotic enteritis was induced in the broilers by oral inoculation of on d 15 through 21. Thereafter, the sublancin or lincomycin were administered fresh daily for a period of 7 days. The challenge resulted in a significant decrease in ADG ( < 0.05) and a remarkable deterioration in G:F ( < 0.05) during d 15 to 21 of the experiment. There was a sharp increase of numbers in the cecum ( < 0.05). The addition of sublancin or lincomycin reduced caecal counts ( < 0.05). The counts had a tendency to decrease in the lincomycin treatment ( = 0.051) but were the highest in the sublancin treatment (5.76 mg activity/L of water). A higher villus height to crypt depth ratio in the duodenum and jejunum as well as a higher villus height in the duodenum were observed in broilers treated with sublancin or lincomycin ( < 0.05) compared with infected control broilers. It was observed that sublancin and lincomycin decreased IL-1β, IL-6, and tumor necrosis factor-α levels ( < 0.05) in the ileum compared with the infected control. In conclusion, although sublancin's minimum inhibitory concentration is much higher than lincomycin in vitro, less sublancin is needed to control necrotic enteritis induced by in vivo than lincomycin. These novel findings indicate that sublancin could be used as a potential antimicrobial agent to control necrotic enteritis.

Role of Wheat Based Diet on the Pathology of Necrotic Enteritis in Turkeys

The study was conducted to investigate the effects of wheat based diet on the pathology of necrotic enteritis in turkeys. Turkeys were divided into four groups. Groups A and B were kept as noninoculated and fed normal commercial diet while groups C and D were challenged orally with C. perfringens and fed wheat based diet to promote the development of experimental disease. Infected turkeys showed clinical signs of depression, ruffled feathers, and dark yellowish faeces showing the most prominent disease signs in turkeys of group D with 30% mortality. Similarly, turkeys of group D showed more striking gross and histopathologic lesions as compared to turkeys of group C. The most severe gross lesions comprised intestinal distension, small necrotic spots and haemorrhages on intestine, fragile intestinal wall, and gas bubble formation in the small intestine. Histologically, inoculated turkeys showed patchy necrosis, desquamation of intestinal epithelium, and intense leukocyte infiltration in the intestine. Microscopic examination showed significant decrease in the height of intestinal villi of inoculated birds. Haematological studies showed significant influence of necrotic enteritis on the blood profile of turkeys in group D. The findings revealed that simultaneous feeding of wheat enhanced the pathology of necrotic enteritis in turkeys.

Effects of Bacillus licheniformis on the growth performance and expression of lipid metabolism-related genes in broiler chickens challenged with Clostridium perfringens-induced necrotic enteritis

Background

Necrotic enteritis (NE), caused by Clostridium perfringens, has cost the poultry industry $2 billion in losses. This study aimed to investigate the effect of Bacillus licheniformis as dietary supplement on the growth, serum antioxidant status, and expression of lipid-metabolism genes of broiler chickens with C. perfringens-induced NE.

Methods

A total of 240 one-day-old broilers were randomly grouped into four: a negative control, an NE experimental model (PC), chickens fed a diet supplemented with 30 % of fishmeal from day 14 onwards and challenged with coccidiosis vaccine (FC), and NE group supplied with feed containing 1.0 × 10⁶ CFU/g B. licheniformis (BL).

Results

Body weight gain, feed conversion ratio, serum antioxidant status, and lipid-metabolism-gene expression were analyzed. In the PC group, FCR increased significantly whereas serum catalase and glutathione peroxidase activity decreased compared with NC group. Dietary B. licheniformis supplementation improved FCR and oxidative stress in experimental avian NE. Using Bacillus licheniformis as a direct-fed microbial (DFM) could also significantly upregulate catabolism-related genes, namely, peroxisome proliferator-activated receptor-α and carnitine palmitoyltransferase-1, in livers and changed the expression of lipid-anabolism genes.

Conclusion

These results suggested that dietary B. licheniformis supplementation can enhance growth and antioxidant ability, as well as change the expression of genes related to fatty-acid synthesis and oxidation in the livers of NE-infected broilers.

Calcium Montmorillonite-Based Dietary Supplement Attenuates Necrotic Enteritis Induced by Eimeria maxima and Clostridium perfringens in Broilers

Necrotic enteritis (NE) is a poultry disease caused by Clostridium perfringens and characterized by severe intestinal necrosis. The incidence of avian NE has been progressively increasing following the removal of antibiotics from poultry feed. We evaluated the effect of diets supplemented with the thermally-processed clays, calcium montmorillonite (CaMM) on clinical signs, immunopathology, and cytokine responses in broiler chickens using an experimental model of NE consisting of co-infection with Eimeria maxima and C. perfringens. In Trial 1, Ross/Ross chickens were fed from hatch with a normal basal diet or a CaMM-supplemented diet with or without a fermentable fiber, an organic acid, and/or a plant extract, and co-infected with E. maxima and C. perfringens under conditions simulating clinical infection in the field. Chickens fed a diet supplemented with CaMM plus a fermentable fiber and an organic acid had increased body weight gain, reduced gut lesions, and increased serum antibody levels to C. perfringens α-toxin and NetB toxin compared with chickens fed the basal diet alone. Levels of transcripts for interleukin-1β (IL-1β), IL-6, inducible nitric oxide synthase, and tumor necrosis factor-α superfamily-15 were significantly altered in the intestine and spleen of CaMM-supplemented chickens compared with unsupplemented controls (p<0.05). In Trial 2, Cobb/Cobb chickens were fed an unsupplemented diet or a diet supplemented with CaMM or Varium^®, each with a fermentable fiber and an organic acid, and co-infected with E. maxima and C. perfringens under subclinical infection conditions. Compared with unsupplemented controls, broilers fed with CaMM plus a fermentable fiber and an organic acid had increased body weight gain, and reduced feed conversion ratio, mortality, and intestinal lesions, compared with chickens fed an unsupplemented diet (p<0.05). Dietary supplementation of broiler chickens with CaMM plus a fermentable fiber and an organic acid might be useful to control avian NE in the field.

Alternatives to Antibiotics to Prevent Necrotic Enteritis in Broiler Chickens: A Microbiologist's Perspective

Since the 2006 European ban on the use of antibiotics as growth promoters in animal feed, numerous studies have been published describing alternative strategies to prevent diseases in animals. A particular focus has been on prevention of necrotic enteritis in poultry caused by Clostridium perfringens by the use of microbes or microbe-derived products. Microbes produce a plethora of molecules with antimicrobial properties and they can also have beneficial effects through interactions with their host. Here we review recent developments in novel preventive treatments against C. perfringens-induced necrotic enteritis in broiler chickens that employ yeasts, bacteria and bacteriophages or secondary metabolites and other microbial products in disease control.

Passive immunization with hyperimmune egg-yolk IgY as prophylaxis and therapy for poultry diseases – A review

Passive immunization with pathogen-specific egg yolk antibodies (IgY) is emerging as a potential alternative to antibiotics for the treatment and prevention of various human and animal diseases. Laying hens are an excellent source of high-quality polyclonal antibodies, which can be collected noninvasively from egg yolks. The use of IgY offers several advantages in that it is environmentally friendly, nontoxic, and reduces the numbers of animals required for antibody production. This paper reviews the use of IgY antibodies in the treatment and prevention of enteric pathogen infections in poultry. Brief descriptions of the production, structure, and properties of IgY are also presented. Some limitations of the technology and future perspectives are discussed.

Selection of Bacillus spp. for Cellulase and Xylanase Production as Direct-Fed Microbials to Reduce Digesta Viscosity and Clostridium perfringens Proliferation Using an in vitro Digestive Model in Different Poultry Diets

Previously, our laboratory has screened and identified Bacillus spp. isolates as direct-fed microbials (DFM). The purpose of the present study was to evaluate the cellulase and xylanase production of these isolates and select the most appropriate Bacillus spp. candidates for DFM. Furthermore, an in vitro digestive model, simulating different compartments of the gastrointestinal tract, was used to determine the effect of these selected candidates on digesta viscosity and Clostridium perfringens proliferation in different poultry diets. Production of cellulase and xylanase were based on their relative enzyme activity. Analysis of 16S rRNA sequence classified two strains as Bacillus amyloliquefaciens and one of the strains as Bacillus subtilis. The DFM was included at a concentration of 10⁸ spores/g of feed in five different sterile soybean-based diets containing corn, wheat, rye, barley, or oat. After digestion time, supernatants from different diets were collected to measure viscosity, and C. perfringens proliferation. Additionally, from each in vitro simulated compartment, samples were taken to enumerate viable Bacillus spores using a plate count method after heat-treatment. Significant (P < 0.05) DFM-associated reductions in supernatant viscosity and C. perfringens proliferation were observed for all non-corn diets. These results suggest that antinutritional factors, such as non-starch polysaccharides from different cereals, can enhance viscosity and C. perfringens growth. Remarkably, dietary inclusion of the DFM that produce cellulase and xylanase reduced both viscosity and C. perfringens proliferation compared with control diets. Regardless of diet composition, 90% of the DFM spores germinated during the first 30 min in the crop compartment of the digestion model, followed by a noteworthy increased in the intestine compartment by ~2log₁₀, suggesting a full-life cycle development. Further studies to evaluate in vivo necrotic enteritis effects are in progress.

Towards the control of necrotic enteritis in broiler chickens with in-feed antibiotics phasing-out worldwide

Poultry production has undergone a substantial increase compared to the livestock industries since 1970. However, the industry worldwide is now facing challenges with the removal of in-feed antibiotics completely or gradually, as the once well-controlled poultry diseases have re-emerged to cause tremendous loss of production. Necrotic enteritis (NE) is one of the most important diseases which costs the industry over two billion dollars annually. In this paper, we review the progress on the etiology of NE and its control through dietary modifications, pre- and probiotics, short chain fatty acids, and vaccination. The other likely measures resulted in the most advances in the toxin characterization are also discussed. Vaccine strategies may have greater potential for the control of NE mainly due to clearer etiology of NE having been elucidated in recent years with the identification of necrotic enteritis toxin B-like (NetB) toxin. Therefore, the use of alternatives to in-feed antibiotics with a better understanding of the relationship between nutrition and NE, and limiting exposure to infectious agents through biosecurity and vaccination, might be a tool to reduce the incidence of NE and to improve gut health in the absence of in-feed antibiotics. More importantly, the combinations of different measures may achieve greater protection of birds against the disease. Among all the alternatives investigated, prebiotics, organic acids and vaccination have shown improved gastrointestinal health and thus, have potential for the control of NE.

Natural resin acid –enriched composition as a modulator of intestinal microbiota and performance enhancer in broiler chicken

Resin acids extracted from coniferous trees are known for their antimicrobial and antifungal effects. This trial investigated the effect of a natural resin acid-enriched composition (RAC) on the gastrointestinal microbiota and productive performance of broiler chicken. The results demonstrated that at or above 5 mg/l, RAC prevented the growth of a pure culture ofClostridium perfringens, a causative agent of necrotic enteritis in poultry. Next, the effects of RAC on the microbial community were studied in a fermentation model with both the microbial inoculum and substrate for the microbes isolated from the ileum of broiler chickens. RAC was included at 0, 0.1 and 1 g/kg digesta, and supplementation decreased the relative proportion of lactic acid and increased that of acetic acid produced during the fermentation in a dose-dependent manner. At 1 g/kg inclusion, RAC decreased the density of lactobacilli. The final part of the experiment investigated the influence of RAC on the performance and intestinal microbiota of necrotic enteritis (NE)-challenged broiler chickens. A wheat and soy -based diet was supplemented with RAC at 0, 0.5, 1 and 3 g/kg. The chickens were challenged withEimeria maximaoocysts on day 11, and a pure culture ofC. perfringenson day 14. On day 17, the final day of the trial, RAC inclusion at 1 and 3 g/kg of feed significantly increased body weight. At 3 g/kg RAC numerically decreased the daily mortality seen during the challenge period. In the ileum, RAC at 1 g/kg reduced the NE-associated peak of microbial lactic acid production. Overall, the data suggested that the dietary ingredient RAC has the potential to act as a performance-enhancer and microbial modulator in broiler chickens.