Advances in Poultry Vaccines: Leveraging Biotechnology for Improving Vaccine Development, Stability, and Delivery

With the rapidly increasing demand for poultry products and the current challenges facing the poultry industry, the application of biotechnology to enhance poultry production has gained growing significance. Biotechnology encompasses all forms of technology that can be harnessed to improve poultry health and production efficiency. Notably, biotechnology-based approaches have fueled rapid advances in biological research, including (a) genetic manipulation in poultry breeding to improve the growth and egg production traits and disease resistance, (b) rapid identification of infectious agents using DNA-based approaches, (c) inclusion of natural and synthetic feed additives to poultry diets to enhance their nutritional value and maximize feed utilization by birds, and (d) production of biological products such as vaccines and various types of immunostimulants to increase the defensive activity of the immune system against pathogenic infection. Indeed, managing both existing and newly emerging infectious diseases presents a challenge for poultry production. However, recent strides in vaccine technology are demonstrating significant promise for disease prevention and control. This review focuses on the evolving applications of biotechnology aimed at enhancing vaccine immunogenicity, efficacy, stability, and delivery.

Intervention Strategies to Control Campylobacter at Different Stages of the Food Chain

Campylobacter is one of the most common bacterial pathogens of food safety concern. Campylobacter jejuni infects chickens by 2-3 weeks of age and colonized chickens carry a high C. jejuni load in their gut without developing clinical disease. Contamination of meat products by gut contents is difficult to prevent because of the high numbers of C. jejuni in the gut, and the large percentage of birds infected. Therefore, effective intervention strategies to limit human infections of C. jejuni should prioritize the control of pathogen transmission along the food supply chain. To this end, there have been ongoing efforts to develop innovative ways to control foodborne pathogens in poultry to meet the growing customers' demand for poultry meat that is free of foodborne pathogens. In this review, we discuss various approaches that are being undertaken to reduce Campylobacter load in live chickens (pre-harvest) and in carcasses (post-harvest). We also provide some insights into optimization of these approaches, which could potentially help improve the pre- and post-harvest practices for better control of Campylobacter.

Effects of therapeutic levels of dietary antibiotics on the cecal microbiome composition of broiler chickens

Dietary antibiotics, including antibiotic growth promoters (AGPs), have been commonly used to improve health and growth of poultry. The present study investigated the effects of therapeutic doses of dietary antibiotics, including bacitracin methylene disalicylate (BMD), penicillin G potassium (PP) and an ionophore (salinomycin, SA), on the cecal microbiome of chickens. BMD and SA treatments were given as dietary supplements from d 1 to 35 of age. The SAPP (salinomycin+ penicillin G potassium) group was given SA as a dietary supplement from d 1 to 35 of age and PP was added to drinking water from d 19 to 24 of age to simulate common practices for control of necrotic enteritis in broilers. The cecal contents were collected from all treatment groups on d 10, 24, and 35 of age and DNA was extracted for metagenomic analysis of the cecal microbiome. The results revealed that dietary or water supplementation of therapeutic levels of antibiotics and ionophores to chickens significantly altered the cecal microbial homeostasis during different stages of the chicken life. The alpha diversity analysis showed that BMD, SA, and SAPP treatments decreased diversity and evenness of the cecal microbiome of treated chickens on d 10 of age. Species richness was also reduced on d 35 following treatment with BMD. Beta diversity analyses revealed that SAPP and BMD induced significant changes in the relative abundance of Gram-positive and -negative bacteria on d 10, while no significant differences were observed on d 24. On d 35, the non-treated control group had higher relative abundance of unclassified Gram-positive and -negative bacteria compared to SA, SAPP, and BMD treatment groups. Overall, despite their beneficial role in controlling necrotic enteritis outbreaks, the findings of this study highlight the potential negative effects of dietary supplementation of therapeutic levels of antibiotics on the gut microbiome and suggest that adjusting gut bacteria may be required to restore microbial richness and diversity of the gut microbiome following treatment with these antibiotics.

Folic acid enhances proinflammatory and antiviral molecular pathways in chicken B-lymphocytes infected with a mild infectious bursal disease virus

1. This study evaluated the effect of folic acid (FA) supplementation on the proinflammatory and antiviral molecular pathways of B-lymphocytes infected with a modified live IBDV (ST-12) mild vaccine strain during a timed post-infection analysis.2. A chicken B-lymphocytes (DT-40) cell line was cultured in triplicate at a concentration of 5 × 10⁵ cells per well in 24-well plates; and was divided into three groups: 1: No virus, FA; 2: Virus, no FA; 3: Virus + FA at a concentration of 3.96 mM. The experiment was repeated three times.3. Cells in groups 2 and 3 were infected with a modified live IBDV (ST-12) mild vaccine strain at one multiplicity of infection (MOI: 1). After 1 hour of virus adsorption, samples were collected at 0, 3, 6, 12, 24 and 36 hours post-infection (hpi).4. The modified live IBDV (ST-12) mild vaccine strain triggered a B-lymphocyte specific immune response associated with the upregulation of genes involved in virus recognition (Igß), virus sensing (TLR-2, TLR-3, TLR-4 and MDA5), signal transduction and regulation (TRIF, MyD88 and IRF7), and the antiviral effector molecules (IFN-α, OAS, PKR, and viperin).5. FA supplementation modulated IBDV replication and regulated the proinflammatory and antiviral downstream molecular pathways.6. In conclusion, the low virulent pathotype serotype I modified live IBDV (ST-12) mild vaccine strain was able to trigger and mount an immune response in chicken B-lymphocytes without affecting B-cell viability. FA supplementation modulated B lymphocytes response and improved their innate immune proinflammatory and antiviral response molecular pathways.

Centennial Review: Effects of vitamins A, D, E, and C on the chicken immune system

Vitamins are nutritional elements which are necessary for essential activities such as development, growth, and metabolism of cells. In addition to these conventional functions, vitamins A, D, E, and C have vital roles in normal function of the immune system as their deficiency is known to impair innate and adaptive host responses. By altering transcription of multiple immune system genes and contributing to antioxidant activities, these vitamins influence the immune system in different ways including modulation of cell-mediated and antibody-mediated responses, immunoregulation, and antiinflammatory effects. Furthermore, supplementation of these vitamins to poultry may assist the immune system to combat microbial pathogens while reducing detrimental effects associated with stress and enhancing responses to vaccines. In this article, the relationship between the chicken immune system and vitamins A, D, E, and C is reviewed, and evidence from the literature pertaining to how these vitamins exert their antiinflammatory, regulatory, and antimicrobial effects is discussed.

Within-host model of respiratory virus shedding and antibody response to H9N2 avian influenza virus vaccination and infection in chickens

Avian influenza virus (AIV) H9N2 subtype is an infectious pathogen that can affect both the respiratory and gastrointestinal systems in chickens and continues to have an important economic impact on the poultry industry. While the host innate immune response provides control of virus replication in early infection, the adaptive immune response aids to clear infections and prevent future invasion. Modelling virus-innate immune response pathways can improve our understanding of early infection dynamics and help to guide our understanding of virus shedding dynamics that could lead to reduced transmission between hosts. While some countries use vaccines for the prevention of H9N2 AIV in poultry, the virus continues to be endemic in regions of Eurasia and Africa, indicating a need for improved vaccine efficacy or vaccination strategies. Here we explored how three type-I interferon (IFN) pathways affect respiratory virus shedding patterns in infected chickens using a within-host model. Additionally, prime and boost vaccination strategies for a candidate H9N2 AIV vaccine are assessed for the ability to elicit seroprotective antibody titres. The model demonstrates that inclusion of virus sensitivity to intracellular type-I IFN pathways results in a shedding pattern most consistent with virus titres observed in infected chickens, and the inclusion of a cellular latent period does not improve model fit. Furthermore, early administration of a booster dose two weeks after the initial vaccine is administered results in seroprotective titres for the greatest length of time for both broilers and layers. These results demonstrate that type-I IFN intracellular mechanisms are required in a model of respiratory virus shedding in H9N2 AIV infected chickens, and also highlights the need for improved vaccination strategies for laying hens.

Yeast cell wall polysaccharides enhanced expression of T helper type 1 and 2 cytokines profile in chicken B lymphocytes exposed to LPS challenge and enzyme treatment

1. The objective of this study was to investigate the potential immunomodulatory effects of yeast (Saccharomyces cerevisiae) and yeast-derived products treated with a cell wall lytic enzyme mixture on the gene expression of toll-like receptors and cytokines of chicken B cell line (DT 40) stimulated with lipopolysaccharide. 2. The effect of brewer's yeast (Y), yeast cell wall (YCW), distilled dried grains with solubles (DDGS) and a processed yeast + nucleotide-rich product (PY/N) treated with a yeast cell wall lytic enzyme (E) was assessed using a chicken B cells and LPS challenge model. 3. Relative gene expression of toll-like receptors (TLRs) and cytokines was investigated. Treatment of cells with Y, YCW, YCW + E and PY/N upregulated the expression of TLR2b following LPS challenge. Gene expression of TLR4 was downregulated in E, YCW and YCW + E treatments compared to control, while adding DDGS and PY/N upregulated the expression of TLR4 either before or after enzyme treatment. Following LPS challenge, expression of IL-4 and IL-10 was upregulated in cells treated with YCW and PY/N, both pre and post enzyme incubation. Adding YCW and PY/N to the cells challenged with LPS upregulated the expression of IFN-γ and IL-12 before and after enzyme treatment. Treatment of cells with YCW, DDGS and PY/N increased the expression of IL-6 prior to LPS challenge. 4. In conclusion, the results suggested that yeast-derived products affected immunomodulatory activities by changing the expression of cytokines involved in the innate immune response.

Epigenetic effect of folic acid (FA) on the gene proximal promoter area and mRNA expression of chicken B cell as antigen presenting cells

1. This study evaluated and characterised the effect of folic acid (FA) on chromosomal DNA methylation and the epigenetic result on gene expression control mechanisms in chicken B cells as a model of antigen presenting cells. 2. After FA supplementation, the methylation pattern on the proximal promoter area and mRNA expression of toll-like receptor (TLR) 2b, TLR4, B cell receptor (BCR) immunoglobulin (Ig) β and major histocompatibility complex (MHC) II β chain genes in chicken B cells was observed 3. Chicken B cell line (DT40) cultures were incubated with 0, 1.72 or 3.96 mM of FA for 4 and 8 h and samples were taken at specific time points. After 4 h of incubation, cells were challenged with 0, 1 or 10 µg/ml of lipopolysaccharide (LPS) and samples were collected 4 h post-challenge. 4. FA supplementation modified the methylation patterns of the proximal promoter regions of TLR4, Igß, and MHCII ß chain at 4 and 8 hours of incubation; however, the single CpG dinucleotide of TLR2b remained methylated regardless of the treatment. 5. A positive association was found between FA concentration and percentage DNA methylation on the promoter area of Igβ and TLR2b. However, there was a negative association between FA and MHCII β chain. 6. There were downregulatory effects in TLR4, Igß and MHCII ß chain gene expression after 8 h of incubation, nut not at 4 h. Although incubation time did not affect TLR2b gene expression, FA concentration did, whereby it increased TLR2b expression at 1.72 mM FA (P < 0.05). 7. LPS significant downregulated TLR2b expression, while an interaction between FA and LPS concentration affected TLR4 and Igβ gene expression. 8. In conclusion, the results showed that FA can have an immunomodulatory effect on chicken B cells, possibly affecting their ability to both recognise antigens through the TLR and BCR pathways, and to present it via the MHCII presentation pathway.

Differential immunomodulatory effect of vitamin D (1,25 (OH)2 D3) on the innate immune response in different types of cells infected in vitro with infectious bursal disease virus

It has been demonstrated that vitamin D (Vit D) included in diets offers a beneficial effect by improving innate immune responses in chickens. However, its mechanisms of action and the effect on immunosuppressive pathogens, such as infectious bursal disease virus, are not yet known. In the present study, we have studied the immunomodulatory effect of Vit D on the innate immune response in 3 cell lines: fibroblast cells (DF-1), macrophages (HD11), and B cells (DT-40) infected with IBDV (intermediate vaccine) at 2 multiplicity of infections (MOI) (1 and 0.1). Genes associated with innate immune responses (TLR-3, TLR-21, MDA-5, MyD88, TRIF, IRF-7, INF-α, INF-β, PKR, OAS, viperin, IL-1β, IL-6, and IL-12) were evaluated at different time points (3, 6, 12, 24, and 36 h after infection, h.p.i). Virus production reached a maximum at 24 h.p.i., which was significantly (P < 0.05) higher in DF-1 cells, followed by HD-11 and DT-40 cells. Mainly in HD-11 cells, there was a significant (P < 0.05) effect of Vit D supplementation on receptors TLR-3, TLR-21, and MDA-5 after 12 h.p.i, independent of MOI. DT-40 cells showed the highest antiviral activity, with a significant (P < 0.05) effect on IRF-7, IFN-β, OAS, and PKR gene expression, where expression of IRF-7 and IFN-β correlated positively with Vit D supplementation, while OAS and PKR were independent of Vit D. Proinflammatory cytokines were significantly (P < 0.05) upregulated and found to be Vit D and MOI dependent. In conclusion, this study demonstrated the capacity of IBDV to trigger a strong innate immune response in chicken cells and contributes to the understanding of the activation pathways of innate immunity induced by IBDV and further shows the benefitial effect of Vit D supplementation as an immunomodulator.

Identification, tissue characterization, and innate immune role of Angiogenin-4 expression in young broiler chickens

Intestinal epithelial cells are major producers of antimicrobial proteins, which play an important role in innate immunity. In addition to defensins, the Ribonuclease A superfamily includes important antimicrobial proteins involved in host-defense mechanisms in vertebrates. Angiogenin-4 (Ang4), a member of this RNase superfamily, has been demonstrated to be secreted by Paneth cells in mice. We have successfully cloned and characterized a new chicken gene (chAng4), found for the first time in a nonmammalian species, from intestinal epithelial and lymphoid cells. Characterization of chAng4 revealed 99% nucleotide and 97% amino acid sequence homology to mouse Ang4. Similar functional regions were identified, suggesting a role in innate immunity and regulation of gut microbiota. Furthermore, the mRNA expression pattern of chAng4 was studied in broilers in the presence or absence of beneficial bacteria (probiotics) and organic acids. The results showed that one-day-old chickens expressed low levels of Ang4 in almost all the evaluated tissues (crop, proventriculus, duodenum, jejunum, ileum, and cecal tonsils), except in the bursa of Fabricius that presented the highest expression level. The addition of probiotics and organic acids for either 7 or 14 consecutive days demonstrated a direct effect of probiotics and organic acids on chAng4 expression; moreover, broilers receiving probiotics and organic acids for only 7 D showed higher levels of chAng4 expression compared with those treated for 14 D. Broilers without treatment had a constant high level of expression in cecal tonsils and bursa. In conclusion, we were able to identify and characterize a new antimicrobial gene in chickens (chAng4) throughout the gastrointestinal tract. chAng4 mRNA gene expression was associated with the presence of naturally occurring and supplemented (probiotic) bacteria. The encoded protein might have a potential bactericidal effect against intestinal nonpathogenic and pathogenic microbes, modulating the intestinal microbiota and the innate immunity, and thereby may help minimize the use of antibiotics in poultry feed.

Development of innate immunity in chicken embryos and newly hatched chicks: a disease control perspective

Newly hatched chickens are confronted by a wide array of pathogenic microbes because their adaptive immune defences have limited capabilities to control these pathogens. In such circumstances, and within this age group, innate responses provide a degree of protection. Moreover, as the adaptive immune system is relatively naïve to foreign antigens, synergy with innate defences is critical. This review presents knowledge on the ontogeny of innate immunity in chickens pre-hatch and early post-hatch and provides insights into possible interventions to modulate innate responses early in the life of the bird. As in other vertebrate species, the chicken innate immune system which include cellular mediators, cytokine and chemokine repertoires and molecules involved in antigen detection, develop early in life. Comparison of innate immune systems in newly hatched chickens and mature birds has revealed differences in magnitude and quality, but responses in younger chickens can be boosted using innate immune system modulators. Functional expression of pattern recognition receptors and several defence molecules by innate immune system cells of embryos and newly hatched chicks suggests that innate responses can be modulated at this stage of development to combat pathogens. Improved understanding of innate immune system ontogeny and functionality in chickens is critical for the implementation of sound and safe interventions to provide long-term protection against pathogens. Next-generation tools for studying genetic and epigenetic regulation of genes, functional metagenomics and gene knockouts can be used in the future to explore and dissect the contributions of signalling pathways of innate immunity and to devise more efficacious disease control strategies.

Responses of broiler chickens to Eimeria challenge when fed a nucleotide-rich yeast extract

Nucleotide-rich yeast extract (YN) was investigated for effects on growth performance, jejunal physiology, and cecal microbial activity in Eimeria-challenged broiler chickens. A total of 360-day-old male chicks (Ross × Ross 708) were placed on floor pens and provided a corn-soybean meal-based diet without or with YN (500 g/MT; n = 12). On d 10, 6 replicates per diet were orally administered with 1 mL of E. acervulina and E. maxima sporulated oocysts and the rest (non-challenged control) were administered with 1 mL of distilled water. On d 15, 5 birds/pen were then necropsied for intestinal lesion scores, histomorphology and cecal digesta pH, short chain fatty acids (SCFA), and microbial community using Illumina Miseq platform. Supplemental YN improved (P = 0.01) Feed conversion ratio (FCR) during the prechallenge phase (d 0 to 10). In the postchallenge period (d 11 to 15), Eimeria depressed (P < 0.05) Body weight gain (BWG) relative to non-challenged birds, whereas YN-fed birds had a higher (P = 0.05) BWG compared to that of non-YN-fed birds. There was an interaction between YN and Eimeria on jejunal villi height (VH) (P = 0.001) and expression of cationic amino acid transporter 1(CAT1) (P = 0.04). Specifically, in the absence of Eimeria, YN-fed birds had a shorter VH (892 vs. 1,020 μm) relative to that of control but longer VH (533 vs. 447 μm) in the presence of Eimeria. With respect to CAT1, YN-fed birds had a higher (1.65 vs. 0.78) expression when subjected to Eimeria than when not challenged. Independently, Eimeria decreased (P < 0.01) the jejunal expression of maltase, Na glucose transporter 1 and occludin genes, ceca digesta abundance of genus Clostridium cluster XlVa and Oscillibacter but increased (P < 0.01) jejunal proliferating cell nuclear antigen and interleukin 10. Interaction between YN and Eimeria was observed for ceca digesta pH (P = 0.04) and total SCFA (P = 0.01) such that YN increased SCFA in the absence of Eimeria but reduced SCFA and increased pH in the presence of Eimeria. In summary, Eimeria impaired performance and gut function and shifted gut microbiome; YN improved performance independently, attenuated Eimeria damage on indices of gut function, and modulated cecal microbiome.

Influenza A virus subtype H9N2 infection disrupts the composition of intestinal microbiota of chickens

The impact of low pathogenic influenza viruses such as subtype H9N2, which infect the respiratory and the gastrointestinal tracts of chickens, on microbial composition are not known. Twenty-day-old specific pathogen-free chickens were assigned to two treatment groups, control (uninfected) and H9N2-infected (challenged via the oral-nasal route). Fecal genomic DNA was extracted, and the V3-V4 regions of the 16S rRNA gene were sequenced using the Illumina Miseq® platform. Sequences were curated using Mothur as described in the MiSeq SOP. Infection of chickens with H9N2 resulted in an increase in phylum Proteobacteria, and differential enrichment with the genera Vampirovibrio, Pseudoflavonifractor, Ruminococcus, Clostridium cluster XIVb and Isobaculum while control chickens were differentially enriched with genera Novosphingobium, Sphingomonas, Bradyrhizobium and Bifidobacterium. Analysis of pre- and post-H9N2 infection of the same chickens showed that, before infection, the fecal microbiota was characterized by Lachnospiracea and Ruminococcaceae family and the genera Clostridium sensu stricto, Roseburia and Lachnospiraceae incertae sedis. However, post-H9N2 infection, class Deltaproteobacteria, orders Clostridiales and Bacteroidiales and the genus Alistipes were differentially enriched. Findings from the current study show that influenza virus infection in chickens results in the shift of the gut microbiota, and the disruption of the host-microbial homeostasis in the gut might be one of the mechanisms by which influenza virus infection is established in chickens.

Dietary selenium supplementation enhances antiviral immunity in chickens challenged with low pathogenic avian influenza virus subtype H9N2

Selenium supplementation in poultry feeds has been known to have beneficial effects on the bird health and performance; however antiviral effects of selenium have remained largely unknown. In this study, we have evaluated the effects of supplementation of chicken diets with organic (Selenium Enriched Yeast; SEY) and inorganic selenium (Sodium Selenite; SS) on low pathogenicity avian influenza virus (H9N2) shedding in the cloacal and oropharyngeal swab samples as well as examined the expression of immune related genes. Chickens were fed two doses (High- 0.30 mg/kg of feed; Low- 0.15 mg/kg of feed) of selenium supplementation for 2 weeks followed by low pathogenicity avian influenza virus challenge. Our results showed that the cloacal shedding of virus in all the selenium supplemented groups was significantly lower when compared to the non-supplemented control groups. In addition, the oropharyngeal shedding of virus in chickens fed with organic selenium supplementation was significantly lower than that in the chickens that received either inorganic selenium supplemented feed or controls. Furthermore, the expression of interferon stimulated genes (Viperin, OAS: 2'-5' oligoadenylate synthetase and MDA5: melanoma differentiation-associated gene) in the cecal tonsils was significantly elevated in the selenium treated groups when compared to controls. Additionally, a significantly higher transcription of interferon (IFN)-α, IFN-β and IFN-γ genes in the cecal tonsils and spleens of chickens receiving SEY-L and SS-H supplemented feed was also observed at post virus challenge time points compared to untreated controls. The results of this study demonstrated that supplementation of chicken diets with selenium, can enhance antiviral defense and thus, may have a beneficial effect in controlling viral infections in poultry.

The effects of in ovo administration of encapsulated Toll-like receptor 21 ligand as an adjuvant with Marek's disease vaccine

Marek’s Disease Virus (MDV) is the causative agent of a lymphoproliferative disease, Marek’s disease (MD) in chickens. MD is only controlled by mass vaccination; however, immunity induced by MD vaccines is unable to prevent MDV replication and transmission. The herpesvirus of turkey (HVT) vaccine is one of the most widely used MD vaccines in poultry industry. Vaccines can be adjuvanted with Toll-like receptor ligands (TLR-Ls) to enhance their efficacy. In this study, we examined whether combining TLR-Ls with HVT can boost host immunity against MD and improve its efficacy. Results demonstrated that HVT alone or HVT combined with encapsulated CpG-ODN partially protected chickens from tumor incidence and reduced virus replication compared to the control group. However, encapsulated CpG-ODN only moderately, but not significantly, improved HVT efficacy and reduced tumor incidence from 53% to 33%. Further investigation of cytokine gene profiles in spleen and bursa of Fabricius revealed an inverse association between interleukin (IL)-10 and IL-18 expression and protection conferred by different treatments. In addition, the results of this study raise the possibility that interferon (IFN)-β and IFN-γ induced by the treatments may exert anti-viral responses against MDV replication in the bursa of Fabricius at early stage of MDV infection in chickens.

Characterization of immunogenicity of avian influenza antigens encapsulated in PLGA nanoparticles following mucosal and subcutaneous delivery in chickens

Mucosal vaccine delivery systems have paramount importance for the induction of mucosal antibody responses. Two studies were conducted to evaluate immunogenicity of inactivated AIV antigens encapsulated in poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs). In the first study, seven groups of specific pathogen free (SPF) layer-type chickens were immunized subcutaneously at 7-days of age with different vaccine formulations followed by booster vaccinations two weeks later. Immune responses were profiled by measuring antibody (Ab) responses in sera and lachrymal secretions of vaccinated chickens. The results indicated that inactivated AIV and CpG ODN co-encapsulated in PLGA NPs (2x NanoAI+CpG) produced higher amounts of hemagglutination inhibiting antibodies compared to a group vaccinated with non-adjuvanted AIV encapsulated in PLGA NPs (NanoAI). The tested adjuvanted NPs-based vaccine (2x NanoAI+CpG) resulted in higher IgG responses in the sera and lachrymal secretions at weeks 3, 4 and 5 post-vaccination when immunized subcutaneously. The incorporation of CpG ODN led to an increase in Ab-mediated responses and was found useful to be included both in the prime and booster vaccinations. In the second study, the ability of chitosan and mannan coated PLGA NPs that encapsulated AIV and CpG ODN was evaluated for inducing antibody responses when delivered via nasal and ocular routes in one-week-old SPF layer-type chickens. These PLGA NPs-based and surface modified formulations induced robust AIV-specific antibody responses in sera and lachrymal secretions. Chitosan coated PLGA NPs resulted in the production of large quantities of lachrymal IgA and IgG compared to mannan coated NPs, which also induced detectable amounts of IgA in addition to the induction of IgG in lachrymal secretions. In both mucosal and subcutaneous vaccination approaches, although NPs delivery enhanced Ab-mediated immunity, one booster vaccination was required to generate significant amount of Abs. These results highlight the potential of NPs-based AIV antigens for promoting the induction of both systemic and mucosal immune responses against respiratory pathogens.

A Comparison of Toll-Like Receptor 5 and 21 Ligands as Adjuvants for a Formaldehyde Inactivated H9N2 Avian Influenza Virus Vaccine in Chickens

Low pathogenic avian influenza virus (AIV) infection in chickens can result in economic losses and has impacts on human health. Poultry vaccination is a tool that can be used to decrease infection and transmission of AIVs. Prior research has demonstrated that Toll-like receptor (TLR) ligands can act as vaccine adjuvants and their addition to inactivated AIV vaccines can enhance immune responses elicited in chickens. The objective of this study was to compare the adjuvant capabilities of TLR5 ligand (flagellin) and TLR21 ligand (CpG ODN 2007) administered either alone or in combination with an intramuscular formaldehyde inactivated H9N2 whole virus vaccine in chickens. Along with the inactivated virus, chickens were administered either a single dose of CpG ODN 2007 (2 or 10 μg), flagellin (0.4 or 2 μg), or a combination of both ligands. An additional group received AddaVax™, an oil emulsion style adjuvant. Chickens were vaccinated twice and serum and lachrymal samples were collected weekly following the primary vaccination, and antibody-mediated immune responses were quantified. Results showed that vaccines containing CpG ODN 2007 induce significantly greater systemic and lachrymal antibody responses than vaccines containing flagellin or AddaVax. Combinations of flagellin and CpG ODN 2007 did not demonstrate inhibitory, additive, or synergistic effects on systemic or lachrymal antibody-mediated immune responses. Additionally, for both flagellin and CpG ODN 2007, a fivefold higher dose of each did not induce significantly higher antibody-mediated immune responses compared with the lesser dose. Future studies should examine the induction of cell-mediated immune responses when flagellin, CpG ODN 2007, or other TLR ligands are administered either alone or combined as adjuvants for inactivated H9N2 AIV vaccines.

Gut microbiota-mediated protection against influenza virus subtype H9N2 in chickens is associated with modulation of the innate responses

Commensal gut microbiota plays an important role in health and disease. The current study was designed to assess the role of gut microbiota of chickens in the initiation of antiviral responses against avian influenza virus. Day-old layer chickens received a cocktail of antibiotics for 12 (ABX-D12) or 16 (ABX-D16) days to deplete their gut microbiota, followed by treatment of chickens from ABX-12 with five Lactobacillus species combination (PROB), fecal microbial transplant suspension (FMT) or sham treatment daily for four days. At day 17 of age, chickens were challenged with H9N2 virus. Cloacal virus shedding, and interferon (IFN)-α, IFN-β and interleukin (IL)-22 expression in the trachea, lung, ileum and cecal tonsils was assessed. Higher virus shedding, and compromised type I IFNs and IL-22 expression was observed in ABX-D16 chickens compared to control, while PROB and FMT showed reduced virus shedding and restored IL-22 expression to levels comparable with undepleted chickens. In conclusion, commensal gut microbiota of chickens can modulate innate responses to influenza virus subtype H9N2 infection in chickens, and modulating the composition of the microbiome using probiotics- and/or FMT-based interventions might serve to promote a healthy community that confers protection against influenza virus infection in chickens.

PLGA-encapsulated CpG ODN and Campylobacter jejuni lysate modulate cecal microbiota composition in broiler chickens experimentally challenged with C. jejuni

Campylobacter jejuni is a leading bacterial cause of human gastroenteritis. Reducing Campylobacter numbers in the intestinal tract of chickens will minimize transmission to humans, thereby reducing the incidence of infection. We have previously shown that oral pre-treatment of chickens with C. jejuni lysate and Poly D, L-lactide-co-glycolide polymer nanoparticles (PLGA NPs) containing CpG oligodeoxynucleotide (ODN) can reduce the number of C. jejuni in infected chickens. In the current study, the effects of these pre-treatments on the composition and functional diversity of the cecal microbiota, in chickens experimentally infected with C. jejuni, were investigated using next-generation sequencing. The taxonomic composition analysis revealed a reduction in cecal microbial diversity and considerable changes in the taxonomic profiles of the microbial communities of C. jejuni-challenged chickens. On the other hand, irrespective of the dose, the microbiota of PLGA-encapsulated CpG ODN- and C. jejuni lysate-treated chickens exhibited higher microbial diversity associated with high abundance of members of Firmicutes and Bacteroidetes and lower numbers of Campylobacter than untreated-chickens. These findings suggest that oral administration of encapsulated CpG ODN and C. jejuni lysate can reduce colonization by C. jejuni by enhancing the proliferation of specific microbial groups. The mechanisms that mediate these changes remain, however, to be elucidated.

Induction of immune response in chickens primed in ovo with an inactivated H9N2 avian influenza virus vaccine

Objective

Infection of chickens with low pathogenic avian influenza virus, such as H9N2 virus, culminates in decreased egg production and increased mortality and morbidity if co-infection with other respiratory pathogens occurs. We have previously observed the induction of antibody- and cell-mediated immune responses after intramuscular administration of an H9N2 beta-propiolactone inactivated virus vaccine to chickens. Given the fact that in ovo vaccination represents a practical option for vaccination against H9N2 AIV in chickens, in the current study, we set out to characterize immune responses in chickens against a beta-propiolactone inactivated H9N2 virus vaccine after primary vaccination in ovo on embryonic day 18, and secondary intramuscular vaccination on day 14 post-hatch. We also included the Toll-like receptor 21 ligand, CpG ODN 2007, and an oil emulsion adjuvant, AddaVax™, as adjuvants for the vaccines.

Results

Antibody-mediated immune responses were observed after administering the secondary intramuscular vaccine. Cell-mediated immune responses were observed in chickens that received the beta-propiolactone inactivated H9N2 virus combined with AddaVax™. Our results demonstrate that adaptive immune responses can be induced in chickens after a primary in ovo vaccination and secondary intramuscular vaccination.

In ovo administration of Toll-like receptor ligands encapsulated in PLGA nanoparticles impede tumor development in chickens infected with Marek's disease virus

One of the economically important diseases in the poultry industry is Marek's disease (MD) which is caused by Marek's disease virus (MDV). The use of current vaccines provides protection against clinical signs of MD in chickens. However, these vaccines do not prevent the transmission of MDV to susceptible hosts, hence they may promote the development of new virulent strains of MDV. This issue persuaded us to explore alternative approaches to control MD in chickens. Induction of innate responses at the early stage of life in the chicken may help to prevent or reduce MDV infection. Further, prophylactic use of Toll-like receptor ligands (TLR-Ls) has been shown to generate host immunity against infectious diseases. In this regard, encapsulation of TLR-Ls in Poly(d, l-lactic-co-glycolic acid) (PLGA) may further enhance host responses by controlled release of TLR-Ls for an extended period. Hence, in the current study, protective effects of encapsulated TLR4 and TLR21 ligands, LPS and CpG, respectively, were investigated against MD. Results indicated that administration of encapsulated CpG and LPS first at embryonic day (ED) 18, followed by post-hatch at 14 days-post infection (dpi) intramuscularly, diminished tumor incidence by 60% and 42.8%, respectively at 21dpi compared to the MDV only group. In addition, analysis of cytokine gene profiles of interferon (IFN)-α, IFN-β, IFN-γ, inducible nitric oxide synthase (iNOS), interleukin (IL)-1β, IL-18 and IL-10 in spleen and bursa of Fabricius at different time points suggests that TLR-Ls possibly triggered host responses through the expression of IL-1β and IL-18 to reduce tumor formation. However, further studies are needed to explore the role of these pro-inflammatory cytokines and other influencing elements like lymphocytes in the hindrance of tumor development by TLR-Ls treatment in chickens.

Examination of the effects of virus inactivation methods on the induction of antibody- and cell-mediated immune responses against whole inactivated H9N2 avian influenza virus vaccines in chickens

Several types of avian influenza virus (AIV) vaccines exist, including live-attenuated, vectored, and whole inactivated virus (WIV) vaccines. Inactivated vaccines offer some advantages compared to other types of vaccines, including ease of production and lack of ability to revert to a virulent state. However, WIV are poorly immunogenic, especially when these vaccines are delivered to mucosal surfaces. There are several factors that contribute to the immunogenicity of vaccines, one of which is the method used to inactivate viruses. Several methods exist for producing influenza WIVs, including formaldehyde, a chemical that affects protein structures leading to virus inactivation. Other methods include treatment with beta-propiolactone (BPL) and the application of gamma radiation, both of which have less effects on protein structures compared to formaldehyde, and instead alter nucleic acids in the virion. Here, we sought to determine the effect of the above inactivation methods on immunogenicity of AIV vaccines. To this end, chickens were vaccinated with three different H9N2 WIVs using formaldehyde, BPL, and gamma radiation for inactivation. In addition to administering these three WIVs alone as vaccines, we also included CpG ODN 2007, a synthetic ligand recognized by Toll-like receptor (TLR)21 in chickens, as an adjuvant for each WIV. Subsequently, antibody- and cell-mediated immune responses were measured following vaccination. Antibody-mediated immune responses were increased in chickens that received the BPL and Gamma WIVs compared to the formaldehyde WIV. CpG ODN 2007 was found to significantly increase antibody responses for each WIV compared to WIV alone. Furthermore, we observed the presence of cell-mediated immune responses in chickens that received the BPL WIV combined with CpG ODN 2007. Based on these results, the BPL WIV + CpG ODN 2007 combination was the most effective vaccine at inducing adaptive immune responses against H9N2 AIV. Future studies should characterize mucosal adaptive immune responses to these vaccines.

Gut microbiota modulates type I interferon and antibody-mediated immune responses in chickens infected with influenza virus subtype H9N2

Commensal gut microbes play a critical role in shaping host defences against pathogens, including influenza viruses. The current study was conducted to assess the role and mechanisms of action of commensal gut microbiota on the innate and antibody-mediated responses of layer chickens against influenza virus subtype H9N2. A total of 104 one-day-old specific pathogen free chickens were assigned to either of the four treatments, which included two levels of antibiotics treatment (ABX- and ABX+) and two levels of H9N2 virus infection (H9N2- and H9N2+). At day 17 of age, chickens in the H9N2+ group were infected via the oral-nasal route with 400 μl of 107 TCID₅₀/ml (200 μl/each route). Oropharyngeal and cloacal swabs at days 1, 3, 5, 7 and 9 post-infection (p.i.) for virus shedding, tissue samples at 12 h, 24 h and 36 h p.i. for mRNA measurement, and serum samples at days 7 and 14 p.i. for hemagglutination inhibition (HI) assay and IgG antibodies were collected. Virus shedding analysis showed that antibiotic treated (depleted)-H9N2 virus infected chickens showed a significantly higher oropharyngeal virus shedding at all time points, and cloacal shedding at days 3 and 5 p.i. compared to control treated (undepleted)-H9N2 infected chickens. Analysis of mRNA expression showed that infection of depleted chickens with H9N2 virus resulted in significantly down-regulated type I interferon responses both in the respiratory and gastrointestinal tracts compared to undepleted-H9N2 infected chickens. However, antibody-mediated immune response analysis showed a significantly higher HI antibody titre and IgG levels in the serum of chickens depleted with antibiotics and infected with H9N2 virus compared to undepleted-H9N2 infected chickens. In conclusion, findings from the current study suggest that the gut microbiota of chickens plays an important role in the initiation of innate responses against influenza virus infection, while the antibody-mediated immune response remains unaffected.

Oral administration of PLGA-encapsulated CpG ODN and Campylobacter jejuni lysate reduces cecal colonization by Campylobacter jejuni in chickens

Campylobacter jejuni (C. jejuni) is a major cause of bacterial food-borne illness in humans. It is considered a commensal organism of the chicken gut and infected chickens serve as a reservoir and shed bacteria throughout their lifespan. Contaminated poultry products are considered the major source of infection in humans. Therefore, to reduce the risk of human campylobacteriosis, it is essential to reduce the bacterial load in poultry products. The present study aimed to evaluate the protective effects of soluble and PLGA-encapsulated oligodeoxynucleotides (ODN) containing unmethylated CpG motifs (E-CpG ODN) as well as C. jejuni lysate as a multi-antigen vaccine against colonization with C. jejuni. The results revealed that oral administration of a low (5 µg) or high (50 µg) dose of CpG resulted in a significant reduction in cecal C. jejuni colonization by 1.23 and 1.32 log₁₀ (P < .05) in layer chickens, respectively, whereas E-CpG significantly reduced cecal C. jejuni colonization by 1.89 and 1.46 log₁₀ in layer and broiler chickens at day 22 post-infection (slaughter age in broilers), respectively. Similar patterns were observed for C. jejuni lysate; oral administration of C. jejuni lysate reduced the intestinal burden of C. jejuni in layer and broiler chickens by 2.24 and 2.14 log₁₀ at day 22 post-infection, respectively. Moreover, the combination of E-CpG and C. jejuni lysate reduced bacterial counts in cecal contents by 2.42 log₁₀ at day 22 post-infection in broiler chickens. Anti-C. jejuni IgG antibody (Ab) titers were significantly higher for broiler chickens receiving a low or high dose of E-CpG or a low dose of C. jejuni lysate than for chickens receiving the placebo. Furthermore, a positive correlation was observed between serum IgG Ab titers and cecal counts of C. jejuni in these groups. These findings suggest that PLGA-encapsulated CpG or C. jejuni lysate could be a promising strategy for control of C. jejuni in chickens.

Dietary supplementation with a nucleotide-rich yeast extract modulates gut immune response and microflora in weaned pigs in response to a sanitary challenge

An experiment was carried out to evaluate the short-term effect of supplementing a nucleotide-rich yeast extract (NRYE) on growth performance, gut structure, immunity and microflora of piglets raised under sanitary and unsanitary conditions. A total of 84, 21-day old piglets were used in this study; 42 piglets were raised in a room designated as the clean room that was washed once per week, whereas the other 42 piglets were raised in a room designated as the unclean room in which 7 kg of manure from the sow herd was spread on each pen floor on day 1 and 7 and the room was not washed throughout the experiment. The pigs were fed a corn-soybean meal-based diet without or with 0.1% NRYE. Each treatment had 7 replicate pens in each room, and each pen housed 3 pigs. Feed disappearance and BW were recorded on day 1 and 14. On day 14, one pig per pen was euthanized to collect ileum, mesenteric lymph nodes and spleen tissues, and cecum and colon digesta. Overall, NRYE supplementation did not affect growth performance in both clean and unclean conditions, improved kidney weight in both clean (P=0.0002) and unclean room (P<0.0001) and tended to improve the villus height/crypt depth ratio in the clean room (P=0.073). Supplementing NRYE was associated with upregulation of Ileal programmed cell death gene-1 (P=0.0003), interleukin (IL)-1β (P<0.0001), IL-6 (P=0.0003), IL-10 (P<0.0001) and tumor necrosis factor-α (TNF-α) (P<0.0001) in pigs raised in the unclean room. Supplementing the NRYE in pigs raised in the clean room suppressed growth of cecal Enterobacteriacea (P<0.0001) members and colonic Enterococcus spp. (P<0.019), improved proliferation of cecal Lactobacillus spp. (P<0.002) and colonic Clostridium cluster IV (P<0.011) and XVIa members (P<0.0002). Supplementing the NRYE in the unclean room improved proliferation of cecal Clostridium cluster IV (P<0.026) and suppressed proliferation of colonic Enterococcus spp. (P<0.037). In conclusion, supplementing the NRYE to piglets under unsanitary conditions improved ileal immune response by upregulating inflammatory cytokines, and positively modulated proliferation of beneficial gut bacteria and suppression of harmful ones in both clean and unclean rooms.

Maternal antibody decay and antibody-mediated immune responses in chicken pullets fed prebiotics and synbiotics

Three experiments were conducted to evaluate the effect of yeast-derived carbohydrates (YDC), and a blend of probiotics and YDC (synbiotic, SNB) on serum IgG concentration, maternal-derived antibody (MDA) decay, and specific antibody-mediated immune response in chick pullets following immunization with T-cell dependent antigens. A total of 300 day-old pullet chicks were randomly assigned to 3 dietary treatments including: a basal diet (Control), and diets containing YDC, and SNB (Lactobacillus acidophilus, L. casei, Streptococcus faecium, and Bacillus subtilis, and YDC). In experiment one, on d 1 and wk 3, 4, 5, and 6, blood samples were collected and serum were analyzed by ELISA for total IgG (Y), and MDA against Newcastle disease virus (NDV) and infectious bursal disease virus (IBDV). The second experiment examined the specific antibody against infectious bronchitis virus (IBV) in pullet chicks following vaccination against IBV at d 1. Finally, in experiment 3, on d 21 and 28 posthatch, 10 birds per treatment were immunized intramuscularly with both sheep red blood cells (SRBC) and bovine serum albumin (BSA), and 11 after immunization serum samples were analyzed by hemagglutination assay for antibody response to SRBC, and by ELISA for serum IgM and IgG response to BSA. The results demonstrated that diet containing SNB increased serum IgG at wk 3 posthatch. However, the decay rate of MDA against NDV and IBDV were not affected by dietary treatments. Birds fed YDC showed higher specific antibody response against IBV in wk 4, while both diets containing YDC and SNB decreased antibody response to IBV in wk 6. In addition, specific antibody response against SRBC and BSA was not affected by diets. In conclusion, supplementation of diet with SNB improved humoral immunity by increasing IgG concentration in serum, and modulated the adaptive antibody-mediated immune response against IBV.

The immunomodulatory effect of vitamin D in chickens is dose-dependent and influenced by calcium and phosphorus levels

Vitamin D requirement is estimated to be higher than recommended values for the first two weeks of a broiler chicken's life, and is heavily dependent on the concentrations of Ca and P in the diet. There are data indicating the beneficial effect of higher vitamin D levels on performance and overall health of the chickens. However, data on the role of higher vitamin D levels on the innate immune response of chickens are limited. Therefore, in the current study, we examined the effect of higher doses of vitamin D supplementation on the innate immune response in broiler chickens receiving optimal or calcium (Ca) and phosphorus (P) deficient diets. Three hundred Ross-308 male broiler chicks were randomly allocated into 60 cages with 5 birds per cage in a 3 × 2 factorial design with three levels of vitamin D and two levels of Ca/P with each experimental diet fed to 10 cages (10 replicates). Quantitative reverse transcription PCR (n = 5) was used to assess Toll-like receptor (TLR2b and 4), cytokine/chemokine (IL-12, IFN-γ, IL-10, IL-4, IL-13, IL-18, CxCLi2) and cathelicidin (CATH1, CATHB1, CATH3) transcription levels in peripheral blood mononuclear cells (PBMCs), spleen, and bursa of Fabricius. Vitamin D supplementation of the Ca and P deficient diet considerably augmented transcription of TLR2b, TLR4, CATH1, and CATHB1 and predominantly Th2 cytokines in spleen. Supplementation of the control diet with vitamin D downregulated TLR4 transcription, and dose-dependently increased CATH1, CATHB1, Th1, and Th2 cytokine transcription (Th2>Th1). All diets downregulated CATH3 transcription. In conclusion, vitamin D or its derivative 25-OH-D₃ both have a robust immunomodulatory property with a more favorable Th2 response, while at the same time enhancing observed Th2 cytokine responses under both optimal and lower Ca and P inclusion levels in the diets of broiler chickens.

Effect of yeast-derived products on systemic innate immune response of broiler chickens following a lipopolysaccharide challenge

This study evaluated the effect of yeast-derived products on growth performance, serum antibody levels, and mRNA gene expression of pattern-recognition receptors, and cytokines in broiler chickens. Two hundred and sixteen one-day-old male broiler chickens (Ross-308) were randomly assigned to six dietary treatments with six replicates (cage) of 6 birds per cage. Dietary treatments consisted of a Control diet without antibiotics (C), and diets containing 11 mg/kg of "virginiamycin", 0.25% of yeast cell wall (YCW), 0.2% of a commercial product "Maxi-Gen Plus" containing processed yeast and nucleotides, 0.05% of nucleotides, or a diet containing 8% of distiller's dried grains with solubles (DDGS). On d 21 post-hatch blood samples were collected from 6 birds per treatment and serum sample were analyzed for antibody levels. After blood sampling, birds were injected intraperitoneally with 3 mg/kg of BW of lipopolysaccharide (LPS). The unchallenged group was fed the Control diet and injected with saline solution. Spleen samples were collected to measure the gene expression of toll-like receptors (TLR)2b, TLR4, and TLR21, macrophage mannose receptor (MMR), and cytokines including interleukin (IL)-12, IL-10, IL-4, IL-6, IL-18, and interferon (IFN)-γ. No significant difference in body weight gain, feed intake, and FCR were observed among treatments. Regarding humoral immunity, the diet supplemented with YCW increased serum immunoglobulin (Ig)A level compared with the antibiotic group; however, serum concentrations of IgG and IgM were not affected by dietary treatments. Relative gene expression of TLR2 and TLR4 was not affected by dietary treatments, whereas the expression of TLR21 and MRR was upregulated in diets containing YCW and DDGS. The diet supplemented with YCW increased the expression of all cytokines, and expression of IFN-γ was upregulated in the DDGS group. However, no significant difference was observed for cytokine gene expression in the antibiotic and nucleotide diets. In conclusion, supplementation of diet with YCW stimulated the systemic innate immune responses of broiler chickens following challenge with LPS.

Organic trace mineral supplementation enhances local and systemic innate immune responses and modulates oxidative stress in broiler chickens

The effect of organic trace mineral supplementation on performance, intestinal morphology, immune organ weights (bursa of Fabricius and spleen), expression of innate immune response related genes, blood heterophils/lymphocytes ratio, chemical metabolic panel, natural antibodies (IgG), and oxidative stress of broiler chickens was studied. A total of 1,080 day-old male broilers were assigned to 1 of 3 dietary treatments, which included basal diet with Monensin (control), control diet supplemented with bacitracin methylene disalicylate (BMD), and BMD diet supplemented with organic trace minerals (OTM). No difference in feed conversion ratio was observed among treatments; ileum histomorphological analysis showed a lower crypt depth, higher villi height/crypt depth ratio, and lower villi width in the OTM treatment compared to control. Furthermore, OTM treatment resulted in higher uric acid and lower plasma malondehaldehyde (MDA), indicating lower oxidative stress. Gene expression analysis showed that OTM treatment resulted in up-regulations of TLR2 bin the ileum, and TLR2b, TLR4, and IL-12p35 in the bursa of Fabricius, and down-regulation of TLR2b and TLR4 in the cecal tonsils. In the spleen, OTM treatment resulted in up-regulation of IL-10. In conclusion, OTM supplementation to broiler diets may have beneficial effects on intestinal development, immune system status, and survival by improving ileum histomorphological parameters, modulation of Toll-like receptors and anti-inflammatory cytokines, and decreasing level of MDA, which in conjunction could enhance health status.

Effect of supplementing direct-fed microbials on broiler performance, nutrient digestibilities, and immune responses

Direct-fed microbials (DFM) are used to improve livestock health and performance. The effects of 2 DFM products, a blend of 3 Bacillus strains (DFMB) and a Propionibacteriumspp. (DFMP), on broiler performance, nutrient utilization, and immune responses were investigated. Day-old (n = 120) male broilers were divided into 24 groups of 5 birds and fed 3 wheat-based diets in mash form (8 groups per diet) from d 1 to 22. The control diet was fed without or with 7.5 × 10(4) cfu/g of either DFMB or DFMP. From d 19 to 21 fecal samples were collected for determination of total tract apparent retention (TTAR) of nutrients and AMEn. On d 21, feed intake and BW were determined. On d 22, 5 birds per treatment were killed by cervical dislocation to collect jejunal and ileal contents for determination of digesta viscosity and apparent ileal digestibility (AID) of nutrients, respectively, and ileum, cecal tonsil, and spleen tissues for Toll-like receptors (TLR) and cytokine expressions. Compared with the control, DFM did not affect BW gain and feed intake but DFMP reduced G:F (P < 0.01). Compared with the control (2,875 kcal/kg), birds fed on DFMB and DFMP had higher AMEn (2,979 and 2,916 kcal/kg, respectively; P < 0.05), whereas both DFM reduced the AID of DM (P < 0.001) and CP (P < 0.01). Furthermore, DFMP reduced TTAR of NDF (29.0 vs. 18.4%; P < 0.001), whereas both DFM increased TTAR of DM and fat (P < 0.001). Supplementing DFMP downregulated ileal expression of TLR-2b, IL-2, IL-4, IL-6, IL-10, and IL-13, whereas DFMB downregulated TLR-2b, IL-2, IL-4, and IL-6 in all 3 tissues, IL-10 in the spleen, and upregulated IL-13 in the spleen. In conclusion, the DFM did not improve performance but increased the AMEn of diet by possibly increasing DM and fat retention. Overall, both DFM showed an antiinflammatory effect in the ileum, but DFMB had more effects on local and systemic immunity than DFMP.

Performance, histomorphology, and toll-like receptor, chemokine, and cytokine profile locally and systemically in broiler chickens fed diets supplemented with yeast-derived macromolecules

The turnover of intestinal epithelial cells is a dynamic process that includes adequate cell proliferation and maturation in the presence of microbiota and migration and seeding of immune cells in early gut development in chickens. We studied the effect of yeast-derived macromolecules (YDM) on performance, gut health, and immune system gene expression in the intestine of broiler chickens. One thousand eighty 1-d-old birds, with 60 birds per pen and 6 pens per treatment, were randomly assigned to 3 treatment diets; a diet containing monensin (control), control diet supplemented with bacitracin methylene disalycylate (BMD), and BMD diet supplemented with YDM. Feed intake, BW, mortality, ileum histomorphology, and gene expression of Toll-like receptors (TLR2b, TLR4, and TLR21), cytokines [interferon (IFN)-γ, IFN-β, IL-12p35, IL-1β, IL-6, IL-10, IL-8, IL-2, IL-4, and transforming growth factor (TGF)-β4], and cluster of differentiation (CD)40 in the ileum, cecal tonsil, bursa of Fabricius, and spleen were assessed. No significant overall difference in performance in terms of feed intake, BW gain, and G:F was observed among treatments (P > 0.05). The YDM diet resulted in significantly higher villi height and villi height:crypt depth ratio compared with BMD and control diets (P < 0.05). A significantly lower mortality was observed in the YDM treatment compared with both control and BMD treatments. Compared with the control, gene expression analysis in YDM treatment showed no major change in response in the ileum, whereas higher CD40, IFN-β, IL-β, IL-6, TGF-β4, IL-2, and IL-4 in the cecal tonsil; TLR2b, TLR4, TLR21, and TGF-β4 in the bursa of Fabricius; and TLR4, IL-12p35, IFN-γ, TGF-β4, and IL-4 in the spleen was observed (P < 0.05). In conclusion, supplementation of YDM supports pro- and anti-inflammatory cytokine production via T helper type 1 and 2 (Th1 and Th2) cell-associated pathways both locally and systemically with a stronger additive effect in the cecal tonsil in the presence of BMD in the diet of chickens.

Modeling the efficiency of phosphorus utilization in growing pigs

Microbial phytase has been used to reduce P excretion from swine to mitigate environmental pollution. The objective of the study was to quantify the effect of feeding a low-P phytase-supplemented diet on growth and P utilization in growing pigs using mathematical models. A total of 20 weaned piglets (BW = 6.5 kg) housed in metabolism cages were randomly assigned to a standard diet (STD) or P-amended diet containing reduced P content and supplemented with phytase (AMN) with 10 pigs/diet. Body weight and feed consumption were recorded weekly so complete growth and cumulative P intake (cPI) curves could be modeled. A function with fixed point of inflexion (Gompertz) and a variable point of inflexion (generalized Michaelis-Menten) were considered in determining bioequivalence by analyzing BW vs. age relationships, whereas the monomolecular function was used to describe BW vs. cPI. All functions were incorporated into a nonlinear mixed effects model, and a first-order autoregressive correlation structure was implemented to take into account repeated measures. There was no difference between the 2 groups in final BW when the Gompertz equation was fitted (176 vs. 178 kg with SE of 7 kg for the STD and AMN, respectively) or the rate parameter (0.0140 vs. 0.0139 with SE of 0.0004 for the STD and AMN, respectively). The generalized Michaelis-Menten equation also showed a similar trend. When BW was expressed as a function of cPI the derivative with respect to cPI represented P efficiency, so it was possible to analyze the expected difference of the 2 diets in using P for BW gain and express it as a continuous function of cPI. The analysis showed through the entire growth period the difference in P efficiency was different from zero. On average, 56 g of supplemented inorganic P was consumed by a pig fed the AMN to reach market weight. In contrast, 309 g of supplemented inorganic P was consumed by the group fed the STD to reach similar BW. It would depend on other factors, but feeding pigs the AMN can result in economic benefit. Pigs fed the AMN excreted 19% less P compared with those fed the STD. In conclusion, nonlinear mixed model analysis (with repeated measures) was suitable for growth and efficiency analysis and showed that pigs fed the AMN consumed less than 20% of the inorganic P and performed as well as those fed the traditional inorganic P supplemented diet. The implications for mitigating P pollution, especially in areas where P loading is already problematic, are substantial.