Effect of in ovo-delivered prebiotics and synbiotics on the morphology and specific immune cell composition in the gut-associated lymphoid tissue

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.

Inter- and Transgenerational Effects of In Ovo Stimulation with Bioactive Compounds on Cecal Tonsils and Cecal Mucosa Transcriptomes in a Chicken Model

Exploring how early-life nutritional interventions may impact future generations, this study examines the inter- and transgenerational effects of in ovo injection of bioactive compounds on gene expression in the cecal tonsils and cecal mucosa using a chicken model. Synbiotic PoultryStar® (Biomin) and choline were injected in ovo on the 12th day of egg incubation. Three experimental groups were established in the generation F1: (1) a control group (C) receiving 0.9% physiological saline (NaCl), (2) a synbiotic group (SYN) receiving 2 mg/embryo, and (3) a combined synbiotic and choline group (SYNCH) receiving 2 mg synbiotic and 0.25 mg choline per embryo. For the generations F2 and F3, the SYN and SYNCH groups were each divided into two subgroups: (A) those injected solely in F1 (SYNs and SYNCHs) and (B) those injected in each generation (SYNr and SYNCHr). At 21 weeks posthatching, cecal tonsil and cecal mucosa samples were collected from F1, F2, and F3 birds for transcriptomic analysis. Gene expression profiling revealed distinct intergenerational and transgenerational patterns in both tissues. In cecal tonsils, a significant transgenerational impact on gene expression was noted in the generation F3, following a drop in F2. In contrast, cecal mucosa showed more gene expression changes in F2, indicating intergenerational effects. While some effects carried into F3, they were less pronounced, except in the SYNs group, which experienced an increase compared to F2. The study highlights that transgenerational effects of epigenetic modifications are dynamic and unpredictable, with effects potentially re-emerging in later generations under certain conditions or fading or intensifying over time. This study provides valuable insights into how epigenetic nutritional stimulation during embryonic development may regulate processes in the cecal tonsils and cecal mucosa across multiple generations. Our findings provide evidence supporting the phenomenon of epigenetic dynamics in a chicken model.

Effect of In Ovo Supplementation of Slab51 Probiotic Mixture, Associated with Marek's Disease Vaccine, on Growth Performance, Intestinal Morphology and Eimeria spp. Infection in Broiler Chickens

The interest for in ovo feeding has grown in the last decades mainly concerning probiotics, live microorganisms that can actively interact with the embryo. The aim of this study was to evaluate the effects of a multi-strain probiotic diluted in Marek's disease vaccine (MDV) on zootechnical performances, intestinal morphology and Eimeria spp. infection. One hundred and twenty eggs of Ross 308 broiler chickens were incubated until 18 d, when 105 fertilised and vital eggs were randomly allocated into three groups. A control group (C) was inoculated with MDV; two treated groups (P1 and P2) were inoculated with MDV and different concentrations of probiotics: 1 × 105 CFU/100 μL in P1 and 1 × 106 CFU/100 μL in P2. After hatching, chickens were separated into three replicates (10/replicate). Zootechnical parameters were determined. At the end of the cycle (35 d), chickens were slaughtered, and the intestine was collected for morphological analysis from nine chickens per group (three/replicate). Eimeria spp. oocyst shedding was determined weekly, and parasitic lesions were analysed on the histological sample. In ovo treatment with probiotic did not influence hatching rate but significantly improved body weight and positively influenced intestinal morphometric data compared to C. Oocyst shedding in faeces resulted in an increase in C, with significant differences at sampling performed at 14, 21 and 28 d of age. These results suggest that the tested probiotic compound is safe for in ovo supplementation and effectively improves zootechnical performances and coccidian resistance.

N-Carbamylglutamate in ovo feeding improves carcass yield, muscle fiber development, and meat quality in broiler chickens

BACKGROUND

Insufficient endogenous nutrients in the broiler embryo can lead to muscle gluconeogenesis, which ultimately affects the post-hatching performance of chicks. This study investigated the effects of in ovo feeding (IOF) of N-carbamylglutamate (NCG) on the growth hormones, carcass yield, and meat quality in broilers. Fertile eggs from a 30-week-old Ross 308 breeder flock were divided into three treatment groups: NC (non-injection), SC (100 μL saline-injection), and NCG (2 mg NCG injection). Each group had six replicates, with 70 eggs per replicate during incubation. Injections were administered on the 17.5th day of embryonic development. After hatching, 270 chicks were selected for 42-day rearing for further sampling.

RESULTS

Chicks in the NCG group had significantly higher body weight (BW) and average daily gain (ADG) at the growing phase, increased growth and testosterone hormone in both feeding phases (21 and 42 days), and improved average daily gain (ADG) and food conversion ratio (FCR) in both grower and entire feeding phases (P < 0.05). Triiodothyronine (T3) and tetraiodothyronine (T4) levels, carcass yield, dressing, drum weight, breast muscle weight, drumstick weights, thighs, pectoralis major, and their part percentage of carcass were improved in the NCG group (P < 0.05), these effects were varied along feeding phases. Moreover, IOF of the NCG also improved pectoralis breast muscle color values at 24 h post mortem (P < 0.05).

CONCLUSION

These results suggest that NCG injection at the late embryonic age of broiler enhances growth performance and meat quality throughout the lifespan and this can probably be attributed to an increase in thyroid and testosterone hormones, indicating potential involvement in metabolic and nutrient partitioning pathway regulation. © 2024 Society of Chemical Industry.

Chicken Secondary Lymphoid Tissues-Structure and Relevance in Immunological Research

Recent discoveries have indicated the importance of developing modern strategies for vaccinations, more ethical research models, and effective alternatives to antibiotic treatment in farm animals. Chickens (Gallus gallus) play a crucial role in this context given the commercial and economic relevance of poultry production worldwide and the search for analogies between the immune systems of humans and birds. Specifically, chicken secondary lymphoid tissues share similar features to their human counterparts. Chickens have several secondary or peripheral lymphoid tissues that are the sites where the adaptive immune response is initiated. The more general classification of these organs divides them into the spleen and skin-, pineal-, or mucosa-associated lymphoid tissues. Each of these tissues is further subdivided into separate lymphoid structures that perform specific and different functions along the animal's body. A review summarizing the state of the art of research on chicken secondary lymphoid organs is of great relevance for the design of future studies.

Impact of early posthatch feeding on the immune system and selected hematological, biochemical, and hormonal parameters in broiler chickens

Under commercial conditions, chicks hatch within a 24 to 48 h window, a period known as the hatching window. Subsequently, they undergo various treatments before finally being transported to the broiler farm. These procedures may delay the chicks' access to food and water, sometimes receiving them as late as 72 h after hatching. Previous studies have indicated that fasting during this initial period is detrimental, leading to impaired body growth, compromised immune system response, and hindered muscle development. The objective of this study was to assess the impact of early posthatch feeding on immune system organs and selected hematological, biochemical, and hormonal parameters. The experiment utilized Ross 308 broiler eggs incubated under typical commercial hatchery conditions. The experimental group's eggs were hatched in HatchCare hatchers (HC) with immediate access to feed and water, while the control group's eggs were hatched under standard conditions (ST). Thirty chickens from each group were assessed on the 1st (D1), 7th (D7), 21st (D21), and 35th (D35) day after hatching. On D1, the HC group exhibited lower hemoglobin, hematocrit, and total serum protein values, suggesting that early access to water prevents initial dehydration in newborn chicks. Conversely, the ST group showed a stress reaction on D1 due to feed deprivation, leading to an almost 2-fold higher serum corticosterone concentration compared to the HC group. However, this increase did not result in a significant change in the heterophil/lymphocyte ratio. Furthermore, the HC group displayed an increase in triglyceride concentration and a decrease in HDL concentration on D1. On D7, the HC group exhibited an increased relative weight of the bursa and a higher CD4+ cell number in the cecal tonsil (CT), indicating a more rapid development of these organs resulting from early stimulation of the gastrointestinal tract. However, early feeding did not influence the numbers of Bu-1+, CD4+, and CD8+ cells or the germinal center (GC) areas in the spleen. In conclusion, early feeding contributes to the welfare of newborn chicks by reducing dehydration and stress levels and stimulating the development of gut-associated lymphoid tissue.

Effect of fecal microbiota transplantation on early intestinal immune function and histomorphology of immune organs in chicks

The intestinal microbiota drives the maturation of the immune system, which is essential for maintaining lifetime homeostasis. Whether fecal microbiota transplantation can promote the development of the immune system in chicks? On days 1, 3, and 5, the post-hatch Hy-line Brown chicks were treated with fecal suspension from breeding hens. Intestinal length, blood biochemical indicators, the morphology of immune organs, and intestinal immunity-related indicators were focused on days 7 and 14. Short-chain fatty acids were determined by gas chromatography. We discovered that fecal microbial transplantation significantly increased the area of the follicles and medulla from the bursa of Fabricius, as well as the area of the medulla, cortex, and both ratios from the thymus on 14 d, the concentration of butyric acid in feces, the levels of immunologically active substances (transforming growth factor-β, interleukin 10, forkhead box protein P3, G-Protein Coupled Receptor 43, immunoglobulin A, etc.) in serum or the intestine, and the number of goblet cells. Correlation analysis indicated that short-chain fatty acids, as metabolites of the gut microbiota, were correlated with intestinal immunity. In short, fecal microbiota transplantation regulated early intestinal immunity, which provided the possibility for the processing and utilization of gut microbiota as germplasm resources.

IMPACT STATEMENT

Modern management of eggs causes the normal vertical transmission of microbiota from hens to be significantly reduced. The risk of environmental threats to newborn chicks is raised. The microbial community helps to mature the immune system of chicks and protect them from pathogen invasion. We still have doubts about whether transplanting the microbiota can regulate gut immunity. Using the gut microbiota of hens as an excellent resource to improve the immunity of chicks may provide new ideas for the development of the poultry industry.

Biophysiology of in ovo administered bioactive substances to improve gastrointestinal tract development, mucosal immunity, and microbiota in broiler chicks

Early embryonic exogenous feeding of bioactive substances is a topic of interest in poultry production, potentially improving gastrointestinal tract (GIT) development, stimulating immunization, and maximizing the protection capability of newly hatched chicks. However, the biophysiological actions and effects of in ovo administered bioactive substances are inconsistent or not fully understood. Thus, this paper summarizes the functional effects of bioactive substances and their interaction merits to augment GIT development, the immune system, and microbial homeostasis in newly hatched chicks. Prebiotics, probiotics, and synbiotics are potential bioactive substances that have been administered in embryonic eggs. Their biological effects are enhanced by a variety of mechanisms, including the production of antimicrobial peptides and antibiotic responses, regulation of T lymphocyte numbers and immune-related genes in either up- or downregulation fashion, and enhancement of macrophage phagocytic capacity. These actions occur directly through the interaction with immune cell receptors, stimulation of endocytosis, and phagocytosis. The underlying mechanisms of bioactive substance activity are multifaceted, enhancing GIT development, and improving both the innate and adaptive immune systems. Thus summarizing these modes of action of prebiotics, probiotics and synbiotics can result in more informed decisions and also provides baseline for further research.

Influence of a Commercial Synbiotic Administered In Ovo and In-Water on Broiler Chicken Performance and Meat Quality

The present study aimed to test the synbiotic PoultryStar^® sol^US delivered in ovo to evaluate its effect on hatchability, productive performance and meat quality, compared to its post-hatch administration in water. On the twelfth day of embryonic incubation, 1200 fertile eggs were divided into synbiotic groups injected with 2 mg/embryo (T1) and 3 mg/embryo (T2), a saline group injected with physiological saline and an uninjected control group (C). After hatching, 120 male chicks/group were reared and chicks from the saline group were supplemented with the synbiotic via drinking water (T3). Hatchability was low in both T1 and T2 groups. Growth performance was not affected by the treatments. However, in the second rearing phase (15-36 days), birds from the C and T3 groups were heavier than T1 birds, due to a higher feed intake and daily weight gain. Neither route of synbiotic administration influenced final body weight (at 56 days), weight and yield of the carcass or commercial cuts. Physico-chemical properties, total lipid, cholesterol and fatty acid composition of breast muscle were not affected by the treatments. Considering its exploratory nature, this study has raised many questions that need further investigation, such as the bioactive combination and the effect on embryonic development.

RNA-Seq-based discovery of genetic variants and allele-specific expression of two layer lines and broiler chicken

Recent advances in the selective breeding of broilers and layers have made poultry production one of the fastest-growing industries. In this study, a transcriptome variant calling approach from RNA-seq data was used to determine population diversity between broilers and layers. In total, 200 individuals were analyzed from three different chicken populations (Lohmann Brown (LB), n = 90), Lohmann Selected Leghorn (LSL, n = 89), and Broiler (BR, n = 21). The raw RNA-sequencing reads were pre-processed, quality control checked, mapped to the reference genome, and made compatible with Genome Analysis ToolKit for variant detection. Subsequently, pairwise fixation index (F ST) analysis was performed between broilers and layers. Numerous candidate genes were identified, that were associated with growth, development, metabolism, immunity, and other economically significant traits. Finally, allele-specific expression (ASE) analysis was performed in the gut mucosa of LB and LSL strains at 10, 16, 24, 30, and 60 weeks of age. At different ages, the two-layer strains showed significantly different allele-specific expressions in the gut mucosa, and changes in allelic imbalance were observed across the entire lifespan. Most ASE genes are involved in energy metabolism, including sirtuin signaling pathways, oxidative phosphorylation, and mitochondrial dysfunction. A high number of ASE genes were found during the peak of laying, which were particularly enriched in cholesterol biosynthesis. These findings indicate that genetic architecture as well as biological processes driving particular demands relate to metabolic and nutritional requirements during the laying period shape allelic heterogeneity. These processes are considerably affected by breeding and management, whereby elucidating allele-specific gene regulation is an essential step towards deciphering the genotype to phenotype map or functional diversity between the chicken populations. Additionally, we observed that several genes showing significant allelic imbalance also colocalized with the top 1% of genes identified by the FST approach, suggesting a fixation of genes in cis-regulatory elements.

Immunomodulation of B Lymphocytes by Prebiotics, Probiotics and Synbiotics: Application in Pathologies

INTRODUCTION

Prebiotics, probiotics and synbiotics are known to have major beneficial effects on human health due to their ability to modify the composition and the function of the gut mucosa, the gut microbiota and the immune system. These components largely function in a healthy population throughout different periods of life to confer homeostasis. Indeed, they can modulate the composition of the gut microbiota by increasing bacteria strands that are beneficial for health, such as Firmicute and Bifidobacteria, and decreasing harmful bacteria, such as Enteroccocus. Their immunomodulation properties have been extensively studied in different innate cells (dendritic cells, macrophages, monocytes) and adaptive cells (Th, Treg, B cells). They can confer a protolerogenic environment but also modulate pro-inflammatory responses. Due to all these beneficial effects, these compounds have been investigated to prevent or to treat different diseases, such as cancer, diabetes, allergies, autoimmune diseases, etc. Regarding the literature, the effects of these components on dendritic cells, monocytes and T cells have been studied and presented in a number of reviews, but their impact on B-cell response has been less widely discussed.

CONCLUSIONS

For the first time, we propose here a review of the literature on the immunomodulation of B-lymphocytes response by prebiotics, probiotics and synbiotics, both in healthy conditions and in pathologies.

DISCUSSION

Promising studies have been performed in animal models, highlighting the potential of prebiotics, probiotics and synbiotics intake to treat or to prevent diseases associated with B-cell immunomodulation, but this needs to be validated in humans with a full characterization of B-cell subsets and not only the humoral response.

Administration of a Multi-Genus Synbiotic to Broilers: Effects on Gut Health, Microbial Composition and Performance

In recent years, the applicability of prebiotics, probiotics and their mixtures, defined as synbiotics, in poultry production has received considerable attention. Following the increasing regulation of antibiotic use, these nutraceuticals are seen as an alternative way to sustain production efficiency and resistance to pathogens and stressors by modulating birds' gut health. The aim of this study was to evaluate the benefits provided under field conditions by administering the multi-species synbiotic PoultryStar^® sol to broilers in drinking water. To this purpose, three Ross 308 broiler flocks, representing separate progenies of a breeder flock which was treated with the same synbiotic, were housed in separate farms, divided into treatment and control groups, and followed throughout the productive cycle. Synbiotic administration was shown to improve gut health even in absence of a challenge, with limited changes in terms of macroscopic intestinal lesions and more overt differences related to histopathological scores and villi length. Synbiotic-fed chickens performed consistently better in terms of body weight gain, feed conversion ratio and survivability. Lastly, the evaluation of the caecal microbiome through next-generation sequencing highlighted the effects of synbiotic supplementation on the composition of the bacterial population, the implications of which will, however, require further studies to be better comprehended.

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

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

Effects of in ovo delivered xylo- and mannan- oligosaccharides on growth performance, intestinal immunity, cecal short-chain fatty acids, and cecal microbiota of broilers

Background

This study investigated a novel in ovo feeding strategy to determine the prebiotic effects of xylo- and mannan- oligosaccharides (XOS and MOS) differing in the degree of polymerization. A total of 192 fertilized eggs were divided into 6 treatment groups: i) normal saline control (NSC), ii) xylotriose (XOS3), iii) xylotetraose (XOS4), iv) mannotriose (MOS3), v) mannotetraose (MOS4), and vi) no injection control (NIC), each containing 4 replicate trays with 8 eggs per replicate. On d 17 of incubation, 3 mg of oligosaccharides (except for controls) dissolved in 0.5 mL of 0.85% normal saline were injected into the amnion of Cobb 500 broilers eggs. After hatch, the chicks were raised for 28 d under standard husbandry practices and were fed a commercial broilers diet ad libitum, and samples were collected periodically.

Results

The hatchability, growth performance, and relative weights of breast, drumstick, liver, and proventriculus were not different among the treatments (P > 0.05). The XOS3 injection increased the total short-chain fatty acid production at d 28 compared with both control groups (P < 0.05). The villus height to crypt depth ratio was significantly higher in the XOS4 group than both controls on the hatch day (P < 0.01) but were not different among any treatments on d 7 and 28 (P > 0.05). On the hatch day, the expression level of the CD3 gene (a T cell marker) was increased by XOS3, while the IL-10 gene (a marker of anti-inflammatory cytokine) was reduced by MOS4 (P < 0.05) compared with both controls. Compared with both controls, XOS3 exhibited a trend of reduction for IL-10 (P = 0.074). No cytokines or lymphocyte markers were affected by the treatments on d 7 (P > 0.05), except XOS4 increased IL-4 compared with NSC (P < 0.05). The broilers in the MOS4 group had higher operational taxonomic units (OTUs) and had more differentially abundant taxa, including order Lactobacillales and family Leuconostocaceae (P < 0.05) than both controls on d 28. The predictive functional profiling indicated that the linoleic acid metabolism pathway was enriched in the cecal microbiota of the XOS3 group compared with both controls (P < 0.05).

Conclusion

The effects of these XOS and MOS on ileal mucosa and immunity are transient, but the effects on fermentation and cecal microbiota are prolonged, and further research is warranted to determine their use as a gut health promoter in poultry.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00666-z.

Modulation of Intestinal Histology by Probiotics, Prebiotics and Synbiotics Delivered In Ovo in Distinct Chicken Genotypes

Simple Summary

Probiotics, prebiotics and synbiotics are biologically active substances that are commonly used in poultry feeding as an alternative to antibiotic growth promoters. It was found that they could improve the intestinal microstructure as well as the health status and productivity of animals. The aim of this study was to determine the effect of probiotics, prebiotics and synbiotics administrated in ovo on the 12th day of embryonic development on selected morphological parameters of the small intestine in broiler and native chickens. After hatching, the chicks were placed in pens and housed for 42 days. On the last day of the experiment, all birds were individually weighed and slaughtered, and samples for histological analysis were taken from the duodenum, jejunum and ileum. The following parameters were determined: the height, width and surface area of the villi, the thickness of the muscular layer and the depth of the crypts, as well as the ratio of the villi height to the crypt depth. Based on the obtained data, it can be concluded that the substances used have an impact on the production parameters and intestinal morphology in various utility types of poultry. In addition, the obtained results indicate that chickens with different genotypes react differently to a given substance; therefore, the substances should be chosen in relation to the genotype.

Abstract

The aim of the study was to determine the effect of probiotics, prebiotics and synbiotics administered in ovo on selected morphological parameters of the small intestine (duodenum, jejunum, ileum) in broiler chickens (Ross 308) and native chickens (Green-legged Partridge, GP). On the 12th day of embryonic development (the incubation period), an aqueous solution of a suitable bioactive substance was supplied in ovo to the egg’s air cell: probiotic—Lactococcus lactis subsp. cremoris (PRO), prebiotic—GOS, galacto-oligosaccharides (PRE) or symbiotic—GOS + Lactococcus lactis subsp. cremoris (SYN). Sterile saline was injected into control (CON) eggs. After hatching, the chicks were placed in pens (8 birds/pen, 4 replicates/group) and housed for 42 days. On the last day of the experiment, all birds were individually weighed and slaughtered. Samples for histological analysis were taken directly after slaughter from three sections of the small intestine. In samples from the duodenum, jejunum and ileum, the height and width of the intestinal villi (VH) were measured and their area (VA) was calculated, the depth of the intestinal crypts (CD) was determined, the thickness of the muscularis was measured and the ratio of the villus height to the crypt depth (V/C) was calculated. On the basis of the obtained data, it can be concluded that the applied substances administered in ovo affect the production parameters and intestinal morphology in broiler chickens and GP. The experiment showed a beneficial effect of in ovo stimulation with a prebiotic on the final body weight of Ross 308 compared to CON, while the effect of the administered substances on the intestinal microstructure is not unequivocal. In GP, the best effect in terms of villi height and V/C ratio was found in the in ovo synbiotic group. Taking into account the obtained results, it can be concluded that chickens of different genotypes react differently to a given substance; therefore, the substances should be adapted to the genotype.

Chicken embryo as a model in epigenetic research

Epigenetics is defined as the study of changes in gene function that are mitotically or meiotically heritable and do not lead to a change in DNA sequence. Epigenetic modifications are important mechanisms that fine tune the expression of genes in response to extracellular signals and environmental changes. In vertebrates, crucial epigenetic reprogramming events occur during early embryogenesis and germ cell development. Chicken embryo, which develops external to the mother's body, can be easily manipulated in vivo and in vitro, and hence, it is an excellent model for performing epigenetic studies. Environmental factors such as temperature can affect the development of an embryo into the phenotype of an adult. A better understanding of the environmental impact on embryo development can be achieved by analyzing the direct effects of epigenetic modifications as well as their molecular background and their intergenerational and transgenerational inheritance. In this overview, the current possibility of epigenetic changes during chicken embryonic development and their effects on long-term postembryonic development are discussed.

Immunosecurity: immunomodulants enhance immune responses in chickens

The global population has increased with swift urbanization in developing countries, and it is likely to result in a high demand for animal-derived protein-rich foods. Animal farming has been constantly affected by various stressful conditions, which can be categorized into physical, environmental, nutritional, and biological factors. Such conditions could be exacerbated by banning on the use of antibiotics as a growth promoter together with a pandemic situation including, but not limited to, African swine fever, avian influenza, and foot-and-mouth disease. To alleviate these pervasive tension, various immunomodulants have been suggested as alternatives for antibiotics. Various studies have investigated how stressors (i.e., imbalanced nutrition, dysbiosis, and disease) could negatively affect nutritional physiology in chickens. Importantly, the immune system is critical for host protective activity against pathogens, but at the same time excessive immune responses negatively affect its productivity. Yet, comprehensive review articles addressing the impact of such stress factors on the immune system of chickens are scarce. In this review, we categorize these stressors and their effects on the immune system of chickens and attempt to provide immunomodulants which can be a solution to the aforementioned problems facing the chicken industry.

Effects of Selected Prebiotics or Synbiotics Administered in ovo on Lymphocyte Subsets in Bursa of the Fabricius, Thymus, and Spleen in Non-Immunized and Immunized Chicken Broilers

Simple Summary

Probiotics, prebiotics, and synbiotics may be used as feed additives instead of banned antibiotic-based growth promoters. These bioactive compounds applied in ovo have beneficial effects on intestinal bifidobacteria, decrease the number of detrimental bacteria in the gut, stimulate the development of gut-associated lymphoid tissues (GALT), and modulate the development of lymphoid organs. The aim of our study was to determine whether the specific in ovo-delivered prebiotics and synbiotics affected the lymphocyte subsets of the bursa of the Fabricius, thymus, and spleen in non-immunized chicken broilers and in birds immunized with T-dependent (sheep red blood cells—SRBC) and T-independent (dextran—DEX) antigens. This study demonstrated that in ovo administration of prebiotics and synbiotics is a promising approach for enhancing chicken immune system functions. We conclude that a combination of inulin and Lactococcus lactis subsp. lactis IBB SL1 was the most effective of the tested compounds in the stimulation of the chicken immune system.

Abstract

The effects of in ovo-delivered prebiotics and synbiotics on the lymphocyte subsets of the lymphoid organs in non-immunized 7-day-old broiler chickens and in non-immunized, sheep red blood cells (SRBC)-immunized, and dextran (DEX)-immunized 21- and 35-day-old birds were studied. The substances were injected on the 12th day of egg incubation: Prebiotic1 group (Pre1) with a solution of inulin, Prebiotic2 group (Pre2) with a solution of Bi²tos (non-digestive transgalacto-oligosaccharides), Synbiotic1 group (Syn1) with inulin and Lactococcus lactis subsp. lactis IBB SL1, and Synbiotic2 group (Syn2) with Bi²tos and Lactococcus lactis subsp. cremoris IBB SC1. In 7-day-old chicks, a decrease in T splenocytes was noticed in all groups. The most pronounced effect in 21- and 35-day-old birds was an increase in TCRγδ⁺ cells in Syn1 and Syn2 groups. A decrease in bursal B cells was observed in DEX-immunized Pre1 group (21-day-old birds), and in the Syn1 group in non-immunized and SRBC-immunized 35-day-old birds. An increase in double-positive lymphocytes was observed in Pre1 (35-day-old birds) and Pre2 (immunized 21-day-old birds) groups. In Pre1 and Syn1 groups (21- and 35-day-old), an increase in B splenocytes and a decrease in T splenocytes were observed. We concluded that Syn1 was the most effective in the stimulation of the chicken immune system.

Molecular Response in Intestinal and Immune Tissues to in Ovo Administration of Inulin and the Combination of Inulin and Lactobacillus lactis Subsp. cremoris

Intestinal microbiota are a key factor in maintaining good health and production results in chickens. They play an important role in the stimulation of immune responses, as well as in metabolic processes and nutrient digestion. Bioactive substances such as prebiotics, probiotics, or a combination of the two (synbiotic) can effectively stimulate intestinal microbiota and therefore replace antibiotic growth promoters. Intestinal microbiota might be stimulated at the early stage of embryo development in ovo. The aim of the study was to analyze the expression of genes related to energy metabolism and immune response after the administration of inulin and a synbiotic, in which lactic acid bacteria were combined with inulin in the intestines and immune tissues of chicken broilers. The experiment was performed on male broiler chickens. Eggs were incubated for 21 days in a commercial hatchery. On day 12 of egg incubation, inulin as a prebiotic and inulin with Lactobacillus lactis subsp. cremoris as a synbiotic were delivered to the egg chamber. The control group was injected with physiological saline. On day 35 post-hatching, birds from each group were randomly selected and sacrificed. Tissues (spleen, cecal tonsils, and large intestine) were collected and intended for RNA isolation. The gene panel (ABCG8, HNF4A, ACOX2, APBB1IP, BRSK2, APOA1, and IRS2) was selected based on the microarray dataset and biological functions of genes related to the energy metabolism and immune responses. Isolated RNA was analyzed using the RT-qPCR method, and the relative gene expression was calculated. In our experiment, distinct effects of prebiotics and synbiotics following in ovo delivery were manifested in all analyzed tissues, with the lowest number of genes with altered expression shown in the large intestines of broilers. The results demonstrated that prebiotics or synbiotics provide a potent stimulation of gene expression in the spleen and cecal tonsils of broiler chickens. The overall number of gene expression levels and the magnitude of their changes in the spleen and cecal tonsils were higher in the group of synbiotic chickens compared to the prebiotic group.

The effects of in ovo nicotinamide riboside dose on broiler myogenesis

The objective of this study was to determine the effects of in ovo injection of nicotinamide riboside (NR) on broiler embryonic myogenesis. Fertilized Cobb 500 broiler eggs (N = 240) were sorted by weight and within each strata, randomly assigned to 1 of 4 NR dose treatments (0 mmol, 250 mmol, 500 mmol, or 1 mol; final concentration in yolk of 0, 2.5, 5.0, or 10.0 mmol) of NR. At day 10 of incubation, 100 μL of the assigned NR dose was injected into the yolk sac of the developing embryo, and chicks were euthanized within 24 h of hatching. Pectoralis major muscle (PMM) and individual fiber morphometrics were collected. Chicks injected with NR had greater PMM weight and length (P < 0.01), but did not differ from each other (P > 0.14). Chicks from eggs injected with NR had greater PMM weight and width than control chicks (P < 0.01), but did not differ from each other (P = 0.86). Chicks from eggs injected with 500 mmol NR had greater PMM depth than control and 1M chicks (P < 0.04), which did not differ (P = 0.24) from each other. Chicks from eggs injected with 250 mmol NR did not differ in PMM length compared with all other treatments (P > 0.06). There was no treatment effect (P = 0.20) for PMM fiber cross-sectional area; however, there was a treatment effect (P < 0.01) for muscle fiber density. Chicks from eggs injected with 1 mol NR had greater fiber density than all other treatments (P < 0.01). Chicks injected with 250 and 500 mmol NR had greater fiber density than control chicks (P < 0.01), but did not differ (P < 0.06) from each other. Injecting developing embryos at day 10 of incubation increased hatched chick PMM morphometrics, which were partly because of the NR catalyzed increase in muscle fiber density.

Genotype-dependent development of cellular and humoral immunity in the spleen and cecal tonsils of chickens stimulated in ovo with bioactive compounds

Prebiotics, probiotics, and synbiotics, delivered in ovo influence the colonization and development of the peripheral immune system in poultry. This study aimed to investigate the influence of the host genotype (broiler chickens [Ross 308] and old native Polish breed Green-legged Partridgelike [GP] chickens) on the number of B and T cells in the spleen and cecal tonsils (CT). The solution of a bioactive compound was injected in ovo on day 12 of egg incubation: prebiotics (galactooligosaccharides [GOS]), probiotics (Lactococcus lactis subsp. cremoris IBB477), and synbiotics (GOS + L. lactis). The samples were collected on day 7, day 21, and day 42 after hatching (n = 8). The number of Bu-1⁺ (B) cells, CD4⁺ cells, and CD8⁺ cells in the spleen and CT was estimated using immunohistochemistry. The number of germinal centers (GC) was determined in the spleen. In broilers, probiotics increased (P < 0.05) the number of CD4⁺ cells in the CT on day 7. On day 21, prebiotics raised (P < 0.01) the number of cells involved in cellular immunity in the CT (CD4⁺ and CD8⁺ cells) and spleen (CD8⁺ cells). On day 42, it was synbiotics that stimulated the colonization of both the CT and spleen by B cells, but colonization of the spleen only by CD4⁺ and CD8⁺ cells. In GP chickens, synbiotics enforced the cellular immunity (CD4⁺ or CD8⁺ cells) in the spleen at all time points. Synbiotics also stimulated the GC appearance on day 21 and day 42. In GP chickens, the influence of bioactive compounds on colonization of the CT was very limited. In broilers, we determined pronounced and age-dependent effects of prebiotics and synbiotics on the number of B and T cells in both the CT and spleen. In GP chickens, the most potent compound was synbiotics, which stimulated cellular immunity in the spleen but not in the CT. However, given the long-term effects on adaptive immune cells, synbiotics were the most potent compounds in both chicken genotypes.

Effect of a Synbiotic Mix on Lymphoid Organs of Broilers Infected with Salmonella typhimurium and Clostridium perfringens

Simple Summary

The use of synbiotics in the poultry industry could be a tool to regulate immunological activity and generate beneficial effects against pathogens, like Salmonella typhimurium and Clostridium perfringens, particularly in those cases where the use of antibiotics during poultry production was excluded. Either through the generation of short-chain fatty acids (SCFA) that contribute to mucosa proliferation or promoting the growth of beneficial gut bacteria, synbiotics could favor a microenvironment that improves the activity of the immune system. However, the organization and response of lymphocytes in lymphoid tissues could be modified by the type of active compound of the synbiotic. Therefore, the present work investigated the effect of a synbiotic mix on lymphoid tissues of broilers infected with Salmonella typhimurium and Clostridium perfringens. The results showed that the mix of probiotics Lactobacillus rhamnosus HN001, Pediococcus acidilactici MA18/5Ma and a prebiotic can stimulate the bursa and the IgA production, increasing the size of its follicles and promoting the ability to resist infections caused by S.typhimurium in broilers.

Abstract

Synbiotic consumption can modulate immune response. This work involves studying the effect of a synbiotic on lymphoid organs and IgA of broilers infected with Salmonella typhimurium and Clostridium perfringens. A total of 258 one-day-old male broilers (Gallus gallus domesticus), line COBBAvian48 (free of growth-promoting antibiotics), were distributed into eight treatment groups. A symbiotic mix comprising Lactobacillus rhamnosus HN001 and Pediococcus acidilactici MA18/5 M as probiotics and 4.5% (0.045 g g⁻¹) of Agave tequilana fructans as prebiotic per dose (one milliliter) was administered through drinking water the first day of life. Bursa, spleen and thymus were analyzed. Broilers treated with the synbiotic, whether or not infected with pathogens, had bigger bursa follicles than the non-treated (p < 0.05), and the ones from the synbiotic group had more lymphocytes than the control group (p < 0.05). Thymus follicles of the synbiotic group were bigger than the control group (p < 0.05). Lesions associated with Salmonella infection were found in the bursa, however, in the broilers treated with the synbiotic, the lesions were less intense and were not present after 32 days of life. The synbiotic mix can stimulate the bursa, increasing the size of their follicles and promoting the ability to resist infections caused by S.typhimurium in broilers.

The potential for inoculating Lactobacillus animalis and Enterococcus faecium alone or in combination using commercial in ovo technology without negatively impacting hatch and post-hatch performance

The poultry industry has recently undergone transitions into antibiotic free production, and viable antibiotic alternatives, such as probiotics, are necessary. Through in ovo probiotic inoculation, beneficial microflora development in the gastrointestinal tract may occur prior to hatch without negatively impacting chick performance. Therefore, the objective of the present study was to observe the impacts of the injection of probiotic bacteria individually or combined into fertile broiler hatching eggs on hatch and live performance characteristics. A total of 2,080 fertile broiler hatching eggs were obtained from a commercial source. On day 18 of incubation, 4 in ovo injected treatments were applied: 1.) Marek's Disease (HVT) vaccination, 2.) L. animalis (∼10⁶ cfu/50μl), 3.) E. faecium (∼10⁶ cfu/50μl), and 4.) L. animalis + E. faecium (∼10⁶ cfu & ∼10⁶ cfu/50μl each). On day of hatch, hatchability and hatch residue data were recorded. A portion of male chicks from each treatment were placed in a grow-out facility for a 21 d grow-out (18 chicks/pen × 10 pens/treatment = 720 male chicks) with a corn and soy bean meal-based diet without antibiotics or antibiotic alternatives. Performance data and gastrointestinal samples were collected on days 0, 7, 14, and 21. Results indicated no differences in all hatch parameters between treatments (P > 0.05) except for % pipped, where the L. animalis treatment had lower % pipped eggs compared to the HVT control and E. faecium treatments (P = 0.04). No differences were observed in body weight gain or mortality (P > 0.05). Probiotic treatments altered gastrointestinal tissue length, weight, and pH. This resulted in all in ovo injected probiotic treatments increasing feed conversion ratio (FCR) from days 7 to 14 as compared to the control (P = 0.01). Differences in FCR were not observed in any other week of data collection (days 0 to 7, 14 to 21, or 0 to 21; P > 0.05). Although probiotics altered live performance from days 7 to 14, these data suggest that in ovo inoculations of L. animalis and E. faecium in combination are viable probiotic administration practices that potentially improve hatch characteristics and gastrointestinal tract development.

Impact of Prebiotics and Synbiotics Administered in ovo on the Immune Response against Experimental Antigens in Chicken Broilers

Simple Summary

The immune system of chickens matures in the course of embryonic development. Early in ovo supplementation with bioactive substances leads to the long-term maintenance of a high level of intestine bifidobacteria, reduces the number of detrimental microorganisms in the gut, modulates the central and peripheral lymphatic organ development in broilers, and stimulates gut-associated lymphoid tissues (GALT) development after hatching. In this investigation, we studied whether the early in ovo application (at the 12th day of embryo incubation) of selected bioactives (prebiotics and synbiotics) influences the humoral immune response against experimental antigens, and the delayed-type hypersensitivity (DTH) skin reaction to experimental mitogen. This study demonstrated that the in ovo application of bioactives did not significantly influence the humoral immune response against T-dependent and T-independent model antigens. Prebiotics in chickens immunized with T-dependent antigen (SRBC) protected them from a retarded rise of the IgG concentration. Bioactives reduced the mortality of birds, markedly with inulin (−6.4%), and the DTH reaction to phytohemagglutinin on the 7^th and 21^st day after hatching.

Abstract

The effect of the in ovo application of selected prebiotics and synbiotics on the humoral immune response against T-dependent (SRBC) and T-independent (dextran) antigens and delayed-type hypersensitivity (DTH) to phytohemagglutinin was studied. On the 12th day of incubation, 800 eggs (Ross 308) were divided into five groups and injected into the egg air chamber with prebiotic inulin (Pre1), Bi²tos (Pre2), a synbiotic composed of inulin and Lactococcus lactis subsp. lactis IBB SL1 (Syn1), a synbiotic composed of Bi²tos and L. lactis subsp. cremoris IBB SC1 (Syn2), and physiological saline (control group; C). The chickens were immunized twice at the 7th and 21st day of life with SRBC and dextran. A DTH test was performed on the 7th, 21st, and 35th day. The application of prebiotics and synbiotics had no significant effect on the humoral immune response. SRBC-immunized in ovo Pre1- and Pre2-treated chickens showed significantly higher serum IgG levels than the control. A significant effect on the DTH reaction was detected on the 7th (Pre1 < C) and 21st (Pre2 > Syn2) day. However; Bi²tos may transiently stimulate the cellular immune response on the 21st day. It may be concluded that the application of inulin in an egg air chamber on the 12th day of incubation may stimulate the secondary immune response. The inulin-treated group exhibited a lower mortality rate than the control group.

A Proteomic View of the Cross-Talk Between Early Intestinal Microbiota and Poultry Immune System

Proteomics has been used to investigate cross-talk between the intestinal microbiome and host biological processes. In this study, an in ovo technique and a proteomics approach was used to address how early bacterial colonization in the gastrointestinal tract (GIT) could modulate inflammatory and immune responses in young broilers. Embryos at 18 embryogenic days were inoculated with saline (S), 102 CFU of Citrobacter freundii (CF), Citrobacter species (C2), or lactic acid bacteria mixture (L) into the amnion. At 10 days posthatch, ileum samples from 12 birds per treatment were selected for tandem mass spectrometry analysis. Our further findings indicated that treatment-specific influences on early GIT microbiota resulted in different immune responses in mature broilers. Predicted functional analyses revealed activation of inflammation pathways in broilers treated in ovo with L and CF. Exposure to L enhanced functional annotation related to activation, trafficking of immune cells, and skeletal growth based-network, while CF inhibited biological functions associated with immune cell migration and inflammatory response. These results highlighted that proper immune function was dependent on specific GIT microbiota profiles, in which early-life exposure to L-based probiotic may have modulated the immune functions, whereas neonatal colonization of Enterobacteriaceae strains may have led to immune dysregulation associated with chronic inflammation.

Evaluation of the impact of in ovo administered bacteria on microbiome of chicks through 10 days of age

Initial inoculation and colonization of the chicken gastrointestinal tract (GIT) by microbiota have been suggested to have a major influence on the growth performance and health of birds. Commercial practices in chicken production may alter or delay microbial colonization by pioneer colonizing bacteria that can have an impact on the development and maturation of the GIT and intestinal microflora. The objective of this study was to compare the impact of apathogenic Gram-negative isolates or lactic acid bacteria (LAB) as pioneer colonizers on the microbiome at the day of hatch (DOH) and evaluate the influence through 10 D of age on ceca. At 18 embryonic days (E), the amnion of embryos was inoculated with either saline (S), approximately 102 CFU of LAB (L), Citrobacter freundii (C), or Citrobacter species (C2). Once DNA was isolated from mucosal and digesta contents, samples underwent 2 × 300 paired-end Illumina MiSeq library preparation for microbiome analysis. An increased abundance of Lactobacillaceae family and Lactobacillus genus was observed in the L group at DOH (P < 0.05), whereas the abundance of Enterococcaceae and Enterococcus was numerically decreased. While Lactobacillus salivarius was one of the pioneer colonizers in the L group at 18E, the population decreased by 10 D (39.59 to 0.09%) and replaced with a population of undefined Lactobacillus (10.36%) and Lactobacillus reuteri (3.63%). Results suggest that L treatment may have accelerated a mature microbiota. Enterobacteriaceae was the dominant family (57.44%) in C group at DOH (P < 0.05). The C2 group only showed some abundance of the C2 species (7.92%) at DOH but had the highest overall abundance of undefined Lactobacillus in the ceca by 10 D (25.28%). Taken together, different isolates provided in ovo can have an impact on the initial microbiome of the GIT, and some of these differences in ceca remain notable at 10 D.

Effects of in ovo injection of prebiotics and synbiotics on the productive performance and microstructural features of the superficial pectoral muscle in broiler chickens

The aim of the study was to compare the effects of 2 prebiotics and 2 synbiotics injected in ovo on productivity parameters, quality, and microstructure of the superficial pectoral muscle in 35-day-old broiler chickens. On day 12 of incubation, 9,000 eggs Ross 308 were randomly divided into 5 experimental groups treated with different bioactives in ovo injected: C, control with physiological saline; PI, with 1.760 mg inulin; PB, with 0.528 mg of commercial prebiotic Bi2tos; SI, with 1.760 mg inulin and 1,000 CFU Lactococcus lactis spp. lactis IBB SL1; SB, with 0.528 mg Bi2tos and 1,000 CFU Lactococcus lactis spp. cremoris IBB SC1. The synbiotic solution contained 20 μl bacterial suspension and 180 μl prebiotic solution. For productive parameters and further tests ten male birds for each experimental group were used. The birds were slaughtered on day 35 of age. At slaughter, samples of the left pectoral muscles were taken and preserved by freezing in liquid nitrogen. The pH and color of the meat were evaluated at 45 min and 24 h post-mortem. Water holding capacity (WHC) was measured and expressed as the percentage of free water in meat. Microscopic specimens were analysed using MultiScan software for the measurement of the percentage of oxidative and glycolytic fibres and mean diameter of the muscle fibres. In ovo injection of prebiotics Bi2tos had a positive effect on body weight. In prebiotic group (PI) a negative impact on hatchability was observed. Prebiotics and synbiotics had no influence on the yield of the carcass and pectoral muscle. Bioactive compounds had a significant effect on the quality of meat parameters such as: pH 24 h (PI and PB group), L* 45' (SI and SB group), and WHC (groups PB, SI, and SB). The analysis of the enzymatic profile showed a significant increase in the percentage of glycolytic fibres in the pectoral muscle from chicken treated with a synbiotic with the addition of inulin (group SI).

Evaluating bacterial colonization of a developing broiler embryo after in ovo injection with a bioluminescent bacteria

In ovo injection of probiotics has been of interest for achieving early health benefits. However, there is limited research demonstrating where bacteria could migrate within the embryo after injection. The objective of this study was to evaluate bacterial colonization or migration after in ovo injection of broiler embryo with bioluminescent Escherichia coli. Injection using 106 CFU/mL nonpathogenic E. coli was applied to amniotic and air cell regions on day 18 of incubation. On days 18, 19, 20, and 21 the amnion, skin, lung, gastrointestinal tract (GIT), bursa, and spleen were collected. On day 21, the GIT was separated into crop, duodenum, jejunum, ileum, and ceca sections. All tissues were visualized using anin vivo imaging system to confirm the presence of bioluminescent E. coli. Samples were homogenized, 10-fold serially diluted, and spread onto appropriate agar to determine bacterial loads in all tissues. Results indicated that eggs injected into the amnion had significantly high numbers of E. coli cells in all tissues compared to air cell injected and control treatments 2 h post-injection (P < 0.0001). E. coli was also found on the lungs, spleen, and bursa of eggs injected either in the amnion or air cell (P < 0.05). Results indicated that in ovo injection into the amnion was more efficient than air cell injection, yielding a higher bacterial concentration in the evaluated tissues, specifically the ileum and ceca. Future research using bioluminescent probiotic bacteria may establish sites of preference for different probiotics leading to site-specific application that can maximize their overall impact when in ovo injected.

In ovo delivery of various biological supplements, vaccines and drugs in poultry: current knowledge

The technique of delivering various nutrients, supplements, immunostimulants, vaccines, and drugs via the in ovo route is gaining wide attention among researchers worldwide for boosting production performance, immunity and safeguarding the health of poultry. It involves direct administration of the nutrients and biologics into poultry eggs during the incubation period and before the chicks hatch out. In ovo delivery of nutrients has been found to be more effective than post-hatch administration in poultry production. The supplementation of feed additives, nutrients, hormones, probiotics, prebiotics, or their combination via in ovo techniques has shown diverse advantages for poultry products, such as improved growth performance and feed conversion efficiency, optimum development of the gastrointestinal tract, enhancing carcass yield, decreased embryo mortality, and enhanced immunity of poultry. In ovo delivery of vaccination has yielded a better response against various poultry pathogens than vaccination after hatch. So, this review has aimed to provide an insight on in ovo technology and its potential applications in poultry production to deliver different nutrients, supplements, beneficial microbes, vaccines, and drugs directly into the developing embryo to achieve an improvement in post-hatch growth, immunity, and health of poultry. © 2019 Society of Chemical Industry.

Selected prebiotics and synbiotics administered in ovo can modify innate immunity in chicken broilers

BACKGROUND

A previous study showed that prebiotics and synbiotics administered in ovo into the egg air cell on the 12th day of incubation enhance the growth and development of chickens. However, the influence of this procedure on the development and efficiency of the innate immune system of broiler chickens is unclear. Therefore, the aim of this study was to evaluate whether the early (on the 12th day of embryo development) in ovo administration of selected prebiotics (inulin - Pre1 and Bi2tos - Pre2) and synbiotics (inulin + Lactococcus lactis subsp. lactis IBB SL1 - Syn1 and Bi2tos + L. lactis subsp. cremoris IBB SC1 - Syn2) influences the innate immune system.

RESULTS

Chickens (broiler, Ross 308) that were treated with Pre1 exhibited a decreased H/L ratio on D7, but an increased H/L ratio was observed on D21 and D35. In the remaining experimental groups, an increase in the H/L ratio was observed on D21 and D35. The oxidative potential of leukocytes measured using the NBT test increased on D21 in Pre2 and Syn1 groups. The rate of the phagocytic ability of leukocytes increased in Pre1 and Syn1 groups on D21. The phagocytic index decreased in Pre1 and Syn2 groups on D21 and D35. Concurrently, the count of WBC in circulating blood decreased on D21 in Pre1, Pre2, and Syn1 groups. The hematocrit value was increased in Syn1 chickens on D21, in Pre1 chickens on D35, and in Syn2 chickens on both time points.

CONCLUSIONS

Early in ovo treatment of chicken embryos with prebiotics and synbiotics may temporarily modulate not only the production/maturation of leukocytes but also their reactivity.

Early Nutrition Programming (in ovo and Post-hatch Feeding) as a Strategy to Modulate Gut Health of Poultry

Healthy gastrointestinal tract (GIT) is crucial for optimum performance, better feed efficiency, and overall health of poultry. In the past, antibiotic growth promoters (AGP) were commonly used to modulate the gut health of animals. However, considering the public health concern, the use of AGP in animal feeding is banned or regulated in several jurisdictions around the world. This necessitates the need for alternative nutritional strategies to produce healthy poultry. For that, several alternatives to AGP have been attempted with some success. However, effective modulation of the gut health parameters depends on the methods and timing of the compound being available to host animals. Routinely, the alternatives to AGP and other nutrients are provided in feed or water to poultry. However, the GIT of the newly hatched poultry is functionally immature, despite going through significant morphological, cellular, and molecular changes toward the end of incubation. Thus, early growth and development of GIT are of critical importance to enhance nutrients utilization and optimize the growth of poultry. Early nutrition programming using both in ovo and post-hatch feeding has been used as a means to modulate the early growth and development of GIT and found to be an effective strategy but with inconsistent results. This review summarizes the information on in ovo and post-hatch-feeding of different nutrients and feeds additives and their effects on gut development, histomorphology, microbiology, and immunology. Furthermore, this review will provide insight on the future of early nutrition programming as a strategy to enhance gut health, thereby improving overall health and production so that the poultry industry can benefit from this technique.

Possibilities of early life programming in broiler chickens via intestinal microbiota modulation

The strong selection in search for a higher growth rate in broilers has resulted in adverse effects such as metabolic disorders, low responsiveness of the immune system, and decreased resistance to pathogens. On the other hand, newly hatched chicks rely mostly on innate immune responses until their gut gets colonized with microbiota. In consequence, early access to active substances or bacteria (pre- and post-hatch) is particularly relevant here because in broilers much of the immune system development occurs early in life. Therefore, early stimulation of beneficial microflora is critical, as it affects, to a great extent, the entire life-span of an individual, and also because the nutritional manipulations of the gastrointestinal tract (GIT) microbiome to enhance productivity and health are rather limited by the resilience of the ecosystem once established in the chicken´s gut. Early life or developmental programming is based on the assumption that the development of diseases later in life can be modulated by perturbations or environmental exposures during critical pre- or early post-natal life. Substances such as plant derivatives, Na butyrate, pre- and probiotics, and β-glucans have been shown to induce beneficial microbiological and immunological changes within the GIT, and therefore are potential candidates to be used as tools to manipulate GIT functionality in the young chicken. Accordingly, substances as these might represent promising candidates to study intestinal microbiota/immune system modulation in broilers´ early stages of breeding. In ovo-delivered prebiotics and synbiotics have been shown to have no adverse effect on the development of the immune system in exposed chickens, while being able to affect lymphoid-organs' morphology in chickens. In ovo procedures have also been proposed as means of promoting a healthy microflora in embryonic guts and stimulating maturation of the cellular and humoral immune responses in central and peripheral immune organs, including those in the GIT. The purpose of this presentation is to discuss the potential usefulness of the instruments currently available to induce early life programming in broilers.

Modulation of microbial communities and mucosal gene expression in chicken intestines after galactooligosaccharides delivery In Ovo

Intestinal mucosa is the interface between the microbial content of the gut and the host's milieu. The goal of this study was to modulate chicken intestinal microflora by in ovo stimulation with galactooligosaccharides (GOS) prebiotic and to demonstrate the molecular responses of the host. The animal trial was performed on meat-type chickens (Ross 308). GOS was delivered by in ovo injection performed into the air cell on day 12 of egg incubation. Analysis of microbial communities and mucosal gene expression was performed at slaughter (day 42 post-hatching). Chyme (for DNA isolation) and intestinal mucosa (for RNA isolation) from four distinct intestinal segments (duodenum, jejunum, ileum, and caecum) was sampled. The relative abundance of Bifidobacterium spp. and Lactobacillus spp. in DNA isolated from chyme samples was determined using qPCR. On the host side, the mRNA expression of 13 genes grouped into two panels was analysed with RT-qPCR. Panel (1) included genes related to intestinal innate immune responses (IL-1β, IL-10 and IL-12p40, AvBD1 and CATHL2). Panel (2) contained genes involved in intestinal barrier function (MUC6, CLDN1 and TJAP1) and nutrients sensing (FFAR2 and FFAR4, GLUT1, GLUT2 and GLUT5). GOS increased the relative abundance of Bifidobacterium in caecum (from 1.3% to 3.9%). Distinct effects of GOS on gene expression were manifested in jejunum and caecum. Cytokine genes (IL-1β, IL-10 and IL-12p40) were up-regulated in the jejunum and caecum of the GOS-treated group. Host defence peptides (AvBD1 and CATHL2) were up-regulated in the caecum of the GOS-treated group. Free fatty acid receptors (FFAR2 and FFAR4) were up-regulated in all three compartments of the intestine (except the duodenum). Glucose transporters were down-regulated in duodenum (GLUT2 and GLUT5) but up-regulated in the hindgut (GLUT1 and GLUT2). In conclusion, GOS delivered in ovo had a bifidogenic effect in adult chickens. It also modulated gene expression related to intestinal immune responses, gut barrier function, and nutrient sensing.

Prebiotics and synbiotics - in ovo delivery for improved lifespan condition in chicken

Commercially produced chickens have become key food-producing animals in the global food system. The scale of production in industrial settings has changed management systems to a point now very far from traditional methods. During the perinatal period, newly hatched chicks undergo processing, vaccination and transportation, which introduces a gap in access to feed and water. This gap, referred to as the hatching window, dampens the potential for microflora inoculation and as such, prevents proper microbiome, gastrointestinal system and innate immunity development. As a consequence, the industrial production of chickens with a poor microbial profile leads to enteric microbial infestation and infectious disease outbreaks, which became even more prevalent after the withdrawal of antibiotic growth promoters on many world markets (e.g., the EU).This review presents the rationale, methodology and life-long effects of in ovo stimulation of chicken microflora. In ovo stimulation provides efficient embryonic microbiome colonization with commensal microflora during the perinatal period. A carefully selected bioactive formulation (prebiotics, probiotics alone or combined into synbiotics) is delivered into the air cell of the egg on day 12 of egg incubation. The prebiotic penetrates the outer and inner egg membranes and stimulates development on the innate microflora in the embryonic guts. Probiotics are available after the mechanical breakage of the shell membranes by the chick's beak at the beginning of hatching (day 19). The intestinal microflora after in ovo stimulation is potent enough for competitive exclusion and programs the lifespan condition. We present the effects of different combinations of prebiotic and probiotic delivered in ovo on day 12 of egg incubation on microflora, growth traits, feed efficiency, intestinal morphology, meat microstructure and quality, immune system development, physiological characteristics and the transcriptome of the broiler chickens.We discuss the differences between in ovo stimulation (day 12 of egg incubation) and in ovo feeding (days 17-18 of egg incubation) and speculate about possible future developments in this field. In summary, decades of research on in ovo stimulation and the lifelong effects support this method as efficient programming of lifespan conditions in commercially raised chickens.

Review: Roles of Prebiotics in Intestinal Ecosystem of Broilers

In recent years, prebiotics have been considered as potential alternatives to antibiotics. Mechanisms by which prebiotics modulate the ecosystem of the gut include alternation of the intestinal microbiota, improvement of the epithelium, and stimulation of the immune system. It is suggested that the administration of prebiotics not only influences these aspects but also regulates the interaction between the host and the intestinal microbiota comprehensively. In this review, we will discuss how each prebiotic ameliorates the ecosystem by direct or indirect mechanisms. Emphasis will be placed on the effects of prebiotics, including mannan oligosaccharides, β-glucans, and fructans, on the interaction between the intestinal microbiota, gut integrity, and the immunity of broilers. We will highlight how the prebiotics modulate microbial community and regulate production of cytokines and antibodies, improving gut development and the overall broiler health. Understanding the cross talk between prebiotics and the intestinal ecosystem may provide us with novel insights and strategies for preventing pathogen invasion and improving health and productivity of broilers. However, further studies need to be conducted to identify the appropriate dosages and better resources of prebiotics for refinement of administration, as well as to elucidate the unknown mechanisms of action.

The role of the gut microbiome in shaping the immune system of chickens

Most animals are colonised by at least as many microbial cells as somatic cells, potentially comprising at least 100 times more genes within just the gut microbiota than the host itself. It is, therefore, evident that such a conglomeration can have a profound effect on various bodily systems, particularly the (gut) immune system. Chickens are major providers of efficiently produced protein for humans but also harbour common foodborne pathogens and are susceptible to significant and costly diseases, making a thorough understanding of the influence of the gut microbiome on the immune system very pertinent. Major colonisation of the chicken intestine occurs after hatch and this, along with subsequent microbiota composition and activity, are influenced by numerous host and environmental factors, such that each individual has a unique microbiome signature. However, both extreme (e.g. germ free) and more subtle (e.g. diet changes) microbiome modifications can profoundly impact the development of the gut immune system, particularly adaptive immune apparatus and function. This review will consider the influence of the chicken gut microbiome on immune system development, the implications of this relationship in terms of disease susceptibility, vaccine response, optimal health and productivity, and thus exogenous approaches to positively shape microbiome-immune system interactions.

Effect of in ovo injection of raffinose on growth performance and gut health parameters of broiler chicken

The effects of in ovo injection of raffinose (RFO) as a prebiotic on growth performance, relative weight of proventriculus, gizzard, drumstick and breast muscles, and ileum mucosa morphology were examined in Cobb 500 broilers. A total of 240 fertilized eggs were divided into 4 groups: a non-injected with intact shell and 3 levels of RFO solution (1.5, 3.0, and 4.5 mg in 0.2 mL of an aqueous diluents). The RFO solution was injected into the air sac on d 12 of incubation. In total 144 birds were fed a standard diet and management and sacrificed at d 21 post hatch for collection of samples. Total RNA was extracted from the small intestine, and RT-qPCR was performed to quantify mRNA levels of marker genes of immune cells. Injection of RFO had no significant effect (P > 0.05) on d one body weight of chicks. On d 21, the relative weight of the proventriculus, drumstick, breast, and gizzard was not affected (P > 0.05) by RFO. On hatch d, the villus height increased linearly (P < 0.01) with an increasing dose of RFO. Also, an increasing dose of RFO increased the villus height and villus height:crypt depth ratio (P < 0.05) but did not affect the crypt depth on d 21. The expression levels of CD3 and chB6, which are T cell and B cell marker genes, respectively, were significantly enhanced by high dose RFO (4.5 mg). In conclusion, although an increasing dose of RFO in ovo injection did not significantly influence growth performance or slaughter yield of broilers, RFO has the potential of enhancing ileum mucosa morphology and improving immunity in the small intestine, which are indicators of improved gut health.

Gut immunity: its development and reasons and opportunities for modulation in monogastric production animals

The intestine performs the critical roles of nutrient acquisition, tolerance of innocuous and beneficial microorganisms, while retaining the ability to respond appropriately to undesirable microbes or microbial products and preventing their translocation to more sterile body compartments. Various components contribute to antimicrobial defenses in the intestine. The mucus layer(s), antimicrobial peptides and IgA provide the first line of defense, and seek to trap and facilitate the removal of invading microbes. If breached, invading microbes next encounter a single layer of epithelial cells and, below this, the lamina propria with its associated immune cells. The gut immune system has developmental stages, and studies from different species demonstrate that innate capability develops earlier than acquired. In addition, various factors may influence the developmental process; for example, the composition and activity of the gut microbiota, antimicrobials, maternally derived antibodies, host genetics, and various stressors (e.g. feed deprivation). Therefore, it is clear that particularly younger (meat-producing) animals are reliant on innate immune responses (as well as passive immunity) for a considerable period of their productive life, and thus focusing on modulating appropriate innate responses should be an intervention priority. The gut microbiota is probably the most influential factor for immune development and capability. Interventions (e.g. probiotics, prebiotics, antibodies, etc.) that appropriately modulate the composition or activity of the intestinal microbiota can play an important role in shaping the desired functionality of the innate (and acquired) response. In addition, innate immune mediators, such as toll-like receptor agonists, cytokines, etc., may provide more specific ways to suitably modulate the response. A better understanding of mucosal immunology, signaling pathways, and processes, etc., will provide even more precise methods in the future to boost innate immune capability and minimize any associated (e.g. nutrient) costs. This will provide the livestock industry with more effective options to promote robust and efficient productivity.

The In Ovo Feeding Administration (Gallus Gallus)-An Emerging In Vivo Approach to Assess Bioactive Compounds with Potential Nutritional Benefits

In recent years, the in ovo feeding in fertilized broiler (Gallus gallus) eggs approach was further developed and currently is widely applied in the evaluation process of the effects of functional foods (primarily plant origin compounds) on the functionality of the intestinal brush border membrane, as well as potential prebiotic properties and interactions with the intestinal microbial populations. This review collates the information of potential nutrients and their effects on the mineral absorption, gut development, brush border membrane functionality, and immune system. In addition, the advantages and limitations of the in ovo feeding method in the assessment of potential prebiotic effects of plant origin compounds is discussed.

In ovo validation model to assess the efficacy of commercial prebiotics on broiler performance and oxidative stability of meat

The purpose of this study was to examine the effect of in ovo injection of 2 different prebiotics, DiNovo (DN; Laminaria spp., extract containing laminarin and fucoidan) and Bi2tos (BI; non-digestive trans-galactooligosaccharides from milk lactose digested with Bifidobacterium bifidum NCIMB 41171), on growth, slaughter traits, intramuscular fat percentage (IF) and muscle fiber diameter, and lipid oxidation of meat in chickens reared under commercial conditions, following an in ovo trial protocol. On d 12 of embryonic incubation, 350,560 Ross 308 eggs were randomly divided into 3 experimental groups and automatically injected in ovo with: physiological saline (control group), BI at dose of 3.5 mg/embryo and DN at dose of 0.88 mg/embryo. Hatched chicks (males and females) were allocated dependent on treatment group into 3 poultry houses on each farm (3 farms in total) with a stocking density of 21.2 to 21.5 chicks/m2 At 42 d of age, 14 randomly chosen birds (7 males and 7 females), per each treatment from each farm, were individually weighed and slaughtered. The results showed no significant differences of final number of chickens/chicken house, mortality, BW per treatment, stocking density (kg/m2), feed intake, feed conversion rate (FCR), and European Broiler Index among 3 experimental groups. Treatments with BI and DN were associated with slight increases (P > 0.05) in average BW and a minor improvement (P > 0.05) of FCR in BI group. Slaughtered chickens from DN and BI treated groups had significantly increase of BW, carcass weight, carcass yield, and breast muscle weight compared with the control group. IF and muscle fiber diameter were similar among groups. Males had significantly higher slaughter traits compared to females, except for breast muscle yield. The prebiotic treatments led to a higher lipid oxidation in meat, even if the detected TBA reactive substances were below the critical value recognized for meat acceptability. In conclusion, in ovo administration of prebiotics was associated with improvements in a number of parameters of relevance to commercial poultry production.

Synbiotics for Broiler Chickens-In Vitro Design and Evaluation of the Influence on Host and Selected Microbiota Populations following In Ovo Delivery

Synbiotics are synergistic combinations of prebiotics and probiotics. In chickens, synbiotics can be delivered in ovo to expedite colonization of the gut by beneficial bacteria. We therefore aimed to design synbiotics in vitro and validate them in broiler chickens upon in ovo delivery. The probiotic components of the synbiotics were Lactobacillus salivarius and Lactobacillus plantarum. Their growth was assessed in MRS medium supplemented with different prebiotics. Based on in vitro results (hatchability and growth curve), two synbiotics were designed: S1 –Lactobacillus salivarius with galactooligosaccarides (GOS) and S2 –Lactobacillus plantarum with raffinose family oligosaccharides (RFO). These synbiotics were delivered to Cobb broiler chicken embryos on day 12 of incubation at optimized doses (10⁵ cfu egg^-1 of probiotic, 2 mg egg^-1 of prebiotic). Post hatching, 2,400 roosters were reared (600 individuals group^-1 divided into eight replicate pens). Microbial communities were analyzed in ileal and cecal digesta on day 21 using FISH. Gene expression analysis (IL1β, IL4, IL6, IL8, IL12, IL18, IFNβ, and IFNγ) was performed on days 7, 14, 21, and 42 for the spleen and cecal tonsils with RT-qPCR. Body weight and feed intake of the roosters did not differ by the treatments. Microbial populations of Lactobacillus spp. and Enterococcus spp. in the ileum were higher in S1 and S2 than in the control. In the cecum, the control had the highest bacterial counts. S1 caused significant up-regulation of IL6, IL18, IL1β, IFNγ, and IFNβ in the spleen on day 21 and IL1β on day 7 (P < 0.05). In cecal tonsils, S1 caused significant down-regulation of IL12, IL8, and IL1β on day 42 and IFNβ on day 14 (P < 0.05). S2 did not elicit such patterns in any tissues investigated. Thus, we demonstrate that divergent effects of synbiotics in broiler chickens were reflected in in vitro tests.

Effect of in ovo injected prebiotics and synbiotics on the caecal fermentation and intestinal morphology of broiler chickens

Manipulations of the intestinal microbiota composition may improve the health and performance of chickens. In ovo technology allows the administration of a bioactive substance to enter directly into the incubating egg. The objective of the present study was to investigate the effect of in ovo administered prebiotics or synbiotics on microbial activity products in the caeca and the development of the small intestine of broiler chickens. Ross 308 male chickens hatched from eggs injected in ovo with prebiotics or synbiotics were used in this study. Five experimental groups were formed: C (Control) – injected with 0.9% NaCl, the Pre-1 and Pre-2 groups – injected with prebiotics: inulin or Bi2tos, respectively, and the Syn-1 and Syn-2 groups – injected with synbiotics: inulin with Lactococcus lactis subsp. lactis IBB SL1 or Bi2tos with Lactococcus lactis subsp. cremoris IBB SC1, respectively. At the age of 7, 21 and 35 days, 10 chicks of each group were randomly selected, weighed and slaughtered, and the jejunal samples were collected for histological examinations, whereas caecal samples were collected to analyse the end products of microbial fermentation. Synbiotic treatment increased bodyweight, as observed in the Syn-1 group (P < 0.05). The propionate molar proportion was highest in the groups treated with synbiotics, especially in the Syn-1 group (P < 0.01). Furthermore, the molar proportion of acetate was also lowest in the Syn-1 group (P < 0.05). In ovo synbiotics treatment increased the villus length : crypt depth ratio in the jejunal mucosa, which might improve nutrient absorption and contribute to the increased weight of chickens. These effects suggest that the in ovo administration of synbiotics may be an effective method to increase bodyweight, improve the short-chain fatty acid caecal profile and increase the villus length : crypt depth ratio in the jejunal mucosa. These effects were more pronounced in the Syn-1 group than the Syn-2 group.

Long-Term Transcriptomic Effects of Prebiotics and Synbiotics Delivered In Ovo in Broiler Chickens

In ovo delivery of prebiotics and synbiotics in chickens allows for the development of intestinal microflora prior to hatching, which boosts their robustness. The goal of this study was to determine the transcriptomic profile of the spleen (S), cecal tonsils (CT), and large intestine (LI) of adult chickens injected with prebiotics and synbiotics in ovo. On day 12 of embryo development, incubating eggs were injected with prebiotics: inulin alone (P1) or in combination with Lactococcus lactis subsp. lactis IBB2955 (S1), galactooligosaccharides (GOS) alone (P2) or in combination with Lactococcus lactis subsp. cremoris IBB477 (S2); control group (C) was mock injected with physiological saline. Gene expression analysis was conducted using an Affymetrix Chicken Gene 1.1 ST Array Strip. Most of the differentially expressed genes (DEG) were detected in the cecal tonsils of P2 (378 DEG), and were assigned to gene ontology categories: lymphocyte proliferation, activation and differentiation, and cytokine production. Ingenuity pathway analysis of the DEG (CT of P2) indicated the inhibition of humoral and cellular immune responses, e.g., role of NFAT in regulation of immune responses, phagocytosis, production of nitric oxide, NF-κB, IL-8, and CXCR4 signaling. The DEG with the highest up-regulation from S1 and P2 were involved in gene expression (PAPOLA, RPL27A, RPLP1, and RPS29) from P1 and P2 in transport (BEST4, SLC9A3, and SLC13A2), metabolism (OGT, ALPP, CA4, and CA7), signaling (FGG, G3BP2, UBB, G3BP2, CACNA1G, and ATP6V0A4), and immune responses (MSMB, LGALS3, CABIN1, CXCR5, PAX5, and TNFRSF14). Two DEG influencing the complement system (SERPING1 and MIR1674) were down-regulated in P2 and S1. In conclusion, GOS injected in ovo provided the most potent stimulation of the host transcriptome. This is likely due to its strong bifidogenic effect, which triggers proliferation of indigenous embryonic microflora in ovo, and indirectly influences gene expression regulation in host tissues, especially cecal tonsils.

Applications of In Ovo Technique for the Optimal Development of the Gastrointestinal Tract and the Potential Influence on the Establishment of Its Microbiome in Poultry

As the current poultry production system stands, there is a period of time when newly hatched chicks are prevented from access to feed for approximately 48-72 h. Research has indicated that this delay in feeding may result in decreased growth performance when compared to chicks that are fed immediately post-hatch. To remedy this issue, in ovo methodology may be applied in order to supply the embryo with additional nutrients prior to hatching and those nutrients will continue to be utilized by the chick post-hatch during the fasting period. Furthermore, in ovo injection of various biologics have been researched based on the ability of not only supplying the chick embryo with additional nutrients that would promote improved growth but also compounds that may benefit the future health of the chicken host. Such compounds include various immunostimulants, live beneficial bacteria, prebiotics, and synbiotics. However, it is important to determine the site and age of the in ovo injection for the most productive effects. The primary focus of the current review is to address these two issues [the most effective site(s) and age(s) of in ovo injection] as well as provide the framework for the development of the gastrointestinal tract (GIT) of the chick embryo. Additionally, recent research suggests the colonization of the microbiota in the developing chick may occur during the late stages of embryogenesis. Therefore, we will also discuss the potentials of the in ovo injection method in establishing a healthy and diverse community of microorganisms to colonize the developing GIT that will provide both protection from pathogen invasion and improvement in growth performance to developing chicks.