In ovo feeding of probiotic lactobacilli differentially alters expression of genes involved in the development and immunological maturation of bursa of Fabricius in pre-hatched chicks

Treatment of chickens with probiotics under conditions conducive to necrotic enteritis development

Necrotic enteritis (NE) poses a significant challenge to the global broiler industry, particularly with the increasing restrictions on using antibiotic growth promoters. Probiotics have emerged as a promising alternative for effective disease control. This study evaluated the efficacy of a probiotic cocktail consisting of Lactobacillus crispatus, Ligilactobacillus johnsonii, Limosilactobacillus reuteri, and 2 strains of Ligilactobacillus salivarius, under experimental conditions conducive to NE. Chickens were divided into two groups based on stocking density: high stocking density (30 birds/m2) and normal stocking density (15 birds/m2). Within each group, one subgroup received 108 colony-forming units (CFUs) of lactobacilli on days 1, 7, 14, and 20 of age, while the other received phosphate-buffered saline. Body weight and lesion scores were recorded on days 21 and 24, respectively. Tissues from the intestine were collected for analysis of immunoregulatory genes and lymphocyte population. Cecal contents were collected for microbiome analysis. Probiotic treatment improved body weight gain compared to non-treated controls and reduced gut lesion scoring in the birds raised under high stocking density. Probiotic treatment increased the frequency of Bu-1+ B cells and CD3+CD4+ T cells in the cecal tonsils and enhanced the relative expression of antimicrobial peptides (zonula occludens and occludin) in the ileum. However, it decreased the expression of heat shock proteins, interleukin (IL)-18, IL-1β, and interferon (IFN)-γ. Probiotics also enhanced alpha diversity and the abundance of Christensenellaceae_R-7 group, Angelakisella, and Clostridia_vadinBB60 group compared to the high stocking density control group. These findings underscore the potential of probiotics to mitigate NE in broiler chickens, particularly under conditions of high stocking density.

Fecal microbiota transplantation combined with inulin promotes the development and function of early immune organs in chicks

Modern management of chicks hinders the vertical transmission of intestinal microbiota, which is closely related to immunity. Inulin is a substrate that can be utilized by the microbiota. This study aimed to determine whether fecal microbiota transplantation (FMT) combined with inulin played a "1 + 1 > 2" role in enhancing the development and function of immune organs. Chicks were treated with 1 % inulin and/or fecal microbiota suspension on days 1-6. The growth performance, immune organ development, and immune indicators were evaluated on days 7, 14, and 21. Results showed that the combination of FMT and inulin significantly increased the immune organ index on day 7 and promoted the morphological structure and the expression of proliferating cell nuclear antigen (PCNA) in immune organs on days 7, 14, and 21. Each treatment increased the gene expression of interferon-gamma (IFN-γ), interleukin-4 (IL-4), interleukin-2 (IL-2), B cell-activating factor receptor (BAFFR), B cell linker (BLNK), C-X-C Motif Chemokine Ligand 12 (CXCL12), C-X-C Motif Chemokine Receptor 4 (CXCR4), and Biotin (Bu-1) to varying degrees. FMT combined with inulin significantly increased the expression of IgA-positive cells on days 7 and 14. In conclusion, the synergistic effect of FMT and inulin had beneficial impacts on the development and function of immune organs.

Differential Expression of Key Immune Markers in the Intestinal Tract of Developing Chick Embryos

Research on the immunological development of lymphoid organs in chicks has been extensive, yet a significant gap exists in our understanding of innate immunity during embryonic life within the intestinal tract. This study investigated the developmental trajectory of intestinal immunity in chick embryos by evaluating basal gene expression levels of key immune markers at embryonic days (ED) 14, 17, and 20. The results indicated variable expression levels of cytokines, antimicrobial peptides (AMPs), and Toll-like receptor (TLRs) genes throughout the intestinal tract. Most cytokines and chemokines exhibited elevated expression in the cecum, while AMPs, including avian-β-defensins (AvBDs) and cathelicidins (CATHs) genes, showed increased levels in the jejunum at ED20. The findings from the developmental trajectory analysis of these genes revealed elevated expression levels of cytokines, including interferon (IFN)-γ, interleukin (IL)-6, IL-13, and transforming-growth factor (TGF)-β in the cecum at ED20. However, no consistent patterns were observed for AvBDs, CATHs, and TLRs, as their expression varied across different developmental stages of the chick embryo. These findings significantly contribute to our understanding of intestinal immune system development in chick embryos and provide a foundation for further research aimed at enhancing immune capabilities, especially in segments with lower expression levels of immunomodulatory genes.

Comparative Effectiveness of Various Multi-Antigen Vaccines in Controlling Campylobacter jejuni in Broiler Chickens

This study was undertaken to evaluate and compare the efficacy of different multi-antigen vaccines, including heat-inactivated, whole lysate, and subunit (outer membrane proteins [OMPs]) C. jejuni vaccines along with the immunostimulant CpG ODN in controlling Campylobacter colonization in chickens. In the first trial, 125 μg of C. jejuni OMPs and 50 μg of CpG ODN were administered individually or in combination, either in ovo to chick embryos or subcutaneously (SC) to one-day-old chicks. In the second trial, different concentrations of C. jejuni antigens (heat-killed, whole lysate, and OMPs) were administered SC to one-day-old chicks. The results of the first trial revealed that SC immunization with the combination of CpG ODN and C. jejuni OMPs elevated interferon (IFN)-γ, interleukin (IL)-1β, and IL-13 gene expression in the spleen, significantly increased serum IgM and IgY antibody levels, and reduced cecal C. jejuni counts by approximately 1.2 log10. In contrast, in ovo immunization did not elicit immune responses or confer protection against Campylobacter. The results of the second trial showed that SC immunization with C. jejuni whole lysate or 200 μg OMPs reduced C. jejuni counts by approximately 1.4 and 1.1 log10, respectively. In conclusion, C. jejuni lysate and OMPs are promising vaccine antigens for reducing Campylobacter colonization in chickens.

The effect and potential mechanism of inulin combined with fecal microbiota transplantation on early intestinal immune function in chicks

Our previous research found that fecal microbiota transplantation (FMT) and inulin synergistically affected the intestinal barrier and immune system function in chicks. However, does it promote the early immunity of the poultry gut-associated lymphoid tissue (GALT)? How does it regulate the immunity? We evaluated immune-related indicators in the serum, cecal tonsil, and intestine to determine whether FMT synergistic inulin had a stronger impact on gut health and which gene expression regulation was affected. The results showed that FMT synergistic inulin increased TGF-β secretion and intestinal goblet cell number and MUC2 expression on day 14. Expression of BAFFR, PAX5, CXCL12, and IL-2 on day 7 and expression of CXCR4 and IL-2 on day 14 in the cecal tonsils significantly increased. The transcriptome indicated that CD28 and CTLA4 were important regulatory factors in intestinal immunity. Correlation analysis showed that differential genes were related to the immunity and development of the gut and cecal tonsil. FMT synergistic inulin promoted the development of GALT, which improved the early-stage immunity of the intestine by regulating CD28 and CTLA4. This provided new measures for replacing antibiotic use and reducing the use of therapeutic drugs while laying a technical foundation for achieving anti-antibiotic production of poultry products.