Immune Response Of Birds Research Articles

Fecal microbiota transplantation provides insights into the consequences of transcriptome profiles and cell energy in response to circadian misalignment of chickens

The circadian misalignment (CM) disordered circadian rhythms exert adverse effects on animals. Poultry as one of animals suffers health and welfare problems due to long-term lighting photoperiods caused by CM. However, the roles of CM on organ development, cell growth, metabolism and immune are still unclear in chickens. In this study, a Chinese dual-purpose native breed, was used to explore the effects of CM on transcriptomic pattern of brain and cell energy biogenesis, and further fecal microbiota transplantation (FMT) was applied to investigate its "therapy" effect from CM suffering. Our results showed that the CM led to stunting in brain and small intestine of chicken. CM decreased of cell proliferation, and energy production, mtDNA copies and expression of genes related to cell cycle or mitochondrial biogenetics, while it upregulated the reactive oxygen species (ROS) level and the sensitivity to inflammation. Interestingly, FMT rescued the organ developmental defects and cell dysfunctions induced by CM. Circadian misalignment brought about abnormal tissue and cell developments, energy biogenesis, and immune response in birds. This study provided a comprehensive perspective on understanding the regulation of CM and FMT on bird development and welfare.

Dietary 1,3-β-Glucans Affect Growth, Breast Muscle Composition, Antioxidant Activity, Inflammatory Response, and Economic Efficiency in Broiler Chickens.

Recently, researchers have been intensively looking for novel, safe antibiotic alternatives because of the prevalence of many clinical and subclinical diseases affecting bird flocks and the risks of using antibiotics in subtherapeutic doses as feed additives. The present study intended to evaluate the potential use of 1,3-β-glucans (GLC) as antibiotic alternative growth promotors and assessed the effect of their dietary inclusion on the growth performance, carcass traits, chemical composition of breast muscles, economic efficiency, blood biochemical parameters, liver histopathology, antioxidant activity, and the proinflammatory response of broiler chickens. This study used 200 three-day-old ROSS broiler chickens (50 chicks/group, 10 chicks/replicate, with an average body weight of 98.71 ± 0.17 g/chick). They were assigned to four experimental groups with four dietary levels of GLC, namely 0, 50, 100, and 150 mg kg-1, for a 35-day feeding period. Birds fed diets containing GLC showed an identical different growth rate to the control group. However, the total feed intake (TFI) increased quadratically in the GLC50 and GLC100 groups as compared to that in the control group. GLC addition had no significant effect on the weights of internal and immune organs, except for a decrease in bursal weight in the GLC150 group (p = 0.01). Dietary GLC addition increased the feed cost and total cost at 50 and 100 mg kg-1 doses. The percentages of n-3 and n-6 PUFA in the breast muscle of broiler chickens fed GLC-supplemented diets increased linearly in a dose-dependent manner (p < 0.01). The serum alanine aminotransferase (ALT) level and the uric acid level were quadratically increased in the GLC150 group. The serum levels of total antioxidant capacity, catalase, superoxide dismutase, interleukin-1β, and interferon-gamma linearly increased, while the MDA level decreased in the GLC-fed groups in a dose-dependent manner. Normal histological characterization of different liver structures in the different groups with moderate round cells was noted as a natural immune response around the hepatic portal area. The different experimental groups showed an average percentage of positive immunostaining to the proinflammatory marker transforming growth factor-beta with an increase in the dose of GLC addition. The results suggest that GLC up to 100 mg kg-1 concentration can be used as a feed additive in the diets of broiler chickens and shows no adverse effects on their growth, dressing percentage, and internal organs. GLC addition in diets improves the antioxidant activity and immune response in birds. GLC help enrich the breast muscle with n-3 and n-6 polyunsaturated fatty acids.

A comparative evaluation of transcriptome changes in lung and spleen tissues of chickens infected with velogenic and mesogenic Avian Orthoavulavirus 1

Newcastle disease is an acute, highly contagious disease responsible for severe economic losses to the poultry industry worldwide. Clinical assessment of different pathotypes of AOaV-1 strains is well-elucidated in chickens. However, a paucity of data exists for a comparative assessment of avian innate immune responses in birds after infection with two different pathotypes of AOaV-1. We compared early immune responses in chickens infected with a duck-originated velogenic strain (high virulent: genotype VII) and a pigeon-originated mesogenic stain (moderate virulent; genotype VI). Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) identified 4737 differentially expressed genes (DEGs) in the transcriptional profiles of lung and spleen tissues of chickens infected with both pathotypes. More DEGs were expressed in spleen tissue infected with velogenic strain compared to spleen or lung exposed to mesogenic strain. An enriched expression was observed for genes involved in metabolic processes and cellular components, including innate immune-associated signaling pathways. Most DEGs were involved in RIG-I, Toll-like, NF-Kappa B, and MAPK signaling pathways to activate interferon-stimulated genes (ISGs). This study provided a comparative insight into complicated molecular mechanisms and associated DEGs involved in early immune responses of birds to two different AOaV-1 strains.

Effects of Antimicrobial Peptide Supplementation on Immune Response and Immune Organ Index in Broiler Chicks

Background: Misuse of antibiotics has led to bacterial antibiotic resistance and antibiotic residues in meat and egg. The aim of this study was to assess the effect of dietary supplementation of chicken intestinal-derived antimicrobial peptide as an alternative to antibiotic growth promoters on the immune response of birds. Methods: Immune organs of randomly selected birds were collected for immune organ index. Blood samples were collected for serum to measure the antibody titre against infectious bursal disease and Newcastle disease virus using ELISA. Whole blood was collected to study the cytokine gene expression (IL-17A, IFN-α, IFN-γ, TGF-β, IL-10) using Real-time PCR. Result: Antimicrobial peptide supplementation had no significant effect (P greater than 0.05) on the immune organ index and serum antibody Titre against infectious bursal disease and Newcastle disease virus on the 21st and 35th days of the study. However, it significantly (P less than 0.01) downregulated the gene expression of pro-inflammatory cytokines viz., IL-17A, IFN-α, IFN-γ and upregulated IL-10 expression in peripheral blood mononuclear cells. The results suggest that supplementation of antimicrobial peptide at a level of 100 mg/kg diet improved the cell-mediated immune response in broiler chicks but would not have been sufficient to enhance the humoral immune response and immune organ index in chicks.

Vaccines against chicken coccidiosis with particular reference to previous decade: progress, challenges, and opportunities.

Chicken coccidiosis is an economically significant disease of commercial chicken industry accounting for losses of more than £10.4 billion (according to 2016 prices). Additionally, the costs incurred in prophylaxis and therapeutics against chicken coccidiosis in developing countries (for instance Pakistan according to 2018 prices) reached US $45,000.00 while production losses for various categories of chicken ranges 104.74 to US $2,750,779.00. The infection has been reported from all types of commercial chickens (broiler, layer, breeder) having a range of reported prevalence of 7–90%. The concern of resistance towards major anticoccidials has provided a way forward to vaccine research and development. For prophylaxis of chicken coccidiosis, live virulent, attenuated, ionophore tolerant strains and recombinant vaccines have been extensively trialed and commercialized. Eimeria antigens and novel vaccine adjuvants have elicited the protective efficacy against coccidial challenge. The cost of production and achieving robust immune responses in birds are major challenges for commercial vaccine production. In the future, research should be focused on the development of multivalent anticoccidial vaccines for commercial poultry. Efforts should also be made on the discovery of novel antigens for incorporation into vaccine designs which might be more effective against multiple Eimeria species. This review presents a recap to the overall progress against chicken Eimeria with particular reference to previous decade. The article presents critical analysis of potential areas for future research in chicken Eimeria vaccine development.

Аgglutination test and passive hemagglutination test as immunological methods of antigenisisty assessment of vaccines against poultry salmonellosis

Salmonellosis ranks first among acute intestinal infections with an established pathogen in Ukraine. Poultry products are the most frequent source of human salmonellosis is the highest in both the world and Ukraine. Therefore, Salmonella-specific prevention measures in most countries are an issue of great importance. The study's goal was to compare the levels of antibodies against Salmonella to the enteritidis, Typhimurium, and infantis monoantigens in the serum of poultry immunized with the experimental bivalent, the trivalent vaccine against salmonellosis using the Agglutination test (AT) and Passive Hemagglutination test (PHA). The research of two Salmonella inactivated emulsified vaccines – bivalent (S. enteritidis) and trivalent (S. enteritidis, S. typhimurium and S. infantis) was conducted on one of the poultry farms of the Lviv region. The birds were vaccinated two times in the 14th day's interval. The sera samples were taken on the 14, 21, and 28th days after the last shot. The antibody (agglutinin) levels were assessed in the AT and PHA. Both vaccines (bivalent and trivalent) inducted an intense immune response in birds' organisms. The average antibody titers were 1 : 512 –1 : 717 using the AT and 1 : 4096 – 1 : 5734 using the PHA. The highest antibody levels were detected for S. Enteritidis: 1 : 5734 for trivalent vaccine and 1 : 5120 for bivalent one using PHA. AT antibody levels were lower: 1 : 717 for the trivalent vaccine and 1 : 640 for the bivalent. The antibody levels to S. typhimurium were: 1 : 4915 for trivalent vaccine and 1 : 4710 for bivalent (PHA) and 1 : 640 for trivalent vaccine 1 : 589 for bivalent on (AT). The lowest antibody levels were detected in S. Infantis in both tests. An interesting fact of S. infantis agglutinins presence in serum samples from poultry vaccinated with the bivalent vaccine in both tests may be explained by cross-immunity formed by S. enteritidis – S. typhimurium vaccine.

Pathological effects of graded doses of aflatoxin B1 on the development of the testes in juvenile white leghorn males.

Current experiment was planned to investigate the deleterious effects of the graded doses of aflatoxin B1 (AFB1) on white leghorn male birds. For this purpose, one-hundred birds of 8weeks of age were divided into 4 equal groups and reared on feed contaminated with different doses of AFB1 for 10weeks. Group A was kept as a control group and was fed with normal toxin-free diet; groups B, C, and D were offered feed containing 100ppb, 200ppb, and 400ppb of AFB1, respectively. The birds were euthanized at the 4th and 10th week of the experiment. Clinical signs, behavioral changes, absolute and relative organ weight of the testes, and sperm motility were measured. Cellular immune response was observed through carbon clearance assay (CCA), P-HAP, and antibody response against sheep red blood cells (SRBC). Results showed a dose-dependent decline in the immune response of birds with the increase in the level of AFB1 in the feed. A significant decrease in the serum levels of testosterone, prolactin, and LH were observed at the end of the study. Grossly, testicular size and volume were reduced in ABF1 fed birds, while histological examination showed moderate to severe necrosis of testicular parenchyma, with partial to complete arrest of spermatogenesis. Very few spermatozoa were found in group C, while they were almost absent in group D which was offered a diet containing 400ppb AFB1. The motility of sperms was reduced in all treated groups except control. The abovementioned results showed that AFB1 had severe toxic effects on the reproductive and immunological parameters of WLH male birds in a dose-dependent manner.

The Evaluation of Cellular Immunity to Avian Viral Diseases: Methods, Applications, and Challenges.

Cellular immune responses play critical roles in the control of viral infection. However, the immune protection against avian viral diseases (AVDs), a major challenge to poultry industry, is yet mainly evaluated by measuring humoral immune response though antibody-independent immune protection was increasingly evident in the development of vaccines against some of these diseases. The evaluation of cellular immune response to avian viral infection has long been neglected due to limited reagents and methods. Recently, with the availability of more immunological reagents and validated approaches, the evaluation of cellular immunity has become feasible and necessary for AVD. Herein, we reviewed the methods used for evaluating T cell immunity in chickens following infection or vaccination, which are involved in the definition of different cellular subset, the analysis of T cell activation, proliferation and cytokine secretion, and in vitro culture of antigen-presenting cells (APC) and T cells. The pros and cons of each method were discussed, and potential future directions to enhance the studies of avian cellular immunity were suggested. The methodological improvement and standardization in analyzing cellular immune response in birds after viral infection or vaccination would facilitate the dissection of mechanism of immune protection and the development of novel vaccines and therapeutics against AVD.

Immune Response and Bone Marker Enzyme Activities of Broiler Birds Fed Graded Level Taurine-Supplemented-Diets

Abstract Taurine, a derived amino acid has been proven to play an important biological roles in enhancing bone strength and immune activities of broiler birds. This research investigated the effect of the different concentrations of graded level dietary taurine supplement on immune response of birds against Newcastle Disease Virus (NCDV) and Infectious Bursal Disease Virus (IBDV), as well as on enzymatic markers of bone metabolism and effect on mineral composition. A total of 300 unsexed day-old arbor acre broiler birds were used for this research. The birds were randomly distributed using a completely randomized design into five dietary treatment of six replicates with 10 birds per replicate. Treatment one (T1) served as the control group with 0% taurine supplement. Treatments 2, 3, 4, and 5 contained dietary taurine supplements at 0.002, 0.004, 0.006, and 0.008%. Antibody titre against NCDV and IBDV were determined according to standard procedures. The study lasted 42 days. Birds on 0.002% taurine had the highest antibody titre (128.38) against NCDV, while birds on the 0.006% taurine-supplemented-diet also portrayed a distinct (p&lt;0.05) titre value (1029) against IBDV. Serum alkaline phosphatase and bone specific alkaline phosphatase (132.74 and 150.66) at the 42nd day were highest (p&lt;0.05) for birds on 0.004 and 0.002% dietary taurine supplement respectively. The activity of serum tartrate resistant acid phosphatase (44.94) was notably highest (p&lt;0.05) for birds on 0.008% taurine. Bone mineral contents showed that birds fed with 0.002% taurinesupplemented- diet had the highest percentage (p&lt;0.05) of phosphorous (9.50), calcium (32.18) and phosphate (21.77) composition. Conclusively, inclusion of taurine as dietary supplement has proven useful not only in enhancing the birds’ immunity against NCDV an IBDV, but also in boosting bone mineral composition of meat type poultry birds.

Effect of GM maize on metabolism and performance of chicken

Effect of GM maize on metabolism and performance of chicken

Conducting a comprehensive mycological study to prevent the occurrence of aspergillosis in chickens

Diseases of poultry aspergillosis are recorded in many poultry farms, the causes of the disease are the violation of the sanitary and hygienic conditions of hatcheries and poultry houses (unfavorable microclimate, affected feed and litter by microscopic fungi). To prevent the development of infection, it is necessary to control air pollution and equipment in hatcheries; determine the safety indicators of feed and water (the level of their mycological contamination) in poultry houses; monitor the status of feed storage facilities and water supply systems. According to the results of our research, in 15.1% of dead chickens at the age of 3 to 5 days and 6.6% at the age of 7-10 days, according to the results of mycological examination of pathological material, the diagnosis of aspergillosis was established. Aspergillus flavus (47%) Aspergillus fumigatus (34.5%), Aspergillus niger (10%) were isolated from the lungs of dead chickens. Macroscopically revealed edema and hyperemia of the lungs in chickens of 3-5 days of age. The formation of granulomas in the lungs and serous membranes was not detected, which may indicate an acute form of the pathological process. Chickens 7-10 days old showed a strong thickening of the air sacs, lungs with multiple spherical granulomas up to 2 mm in diameter. Spores of fungi entering the lungs cause a local inflammatory reaction - acute pneumonia. Histologically, in chickens of 3-5 days of age, a thickening of the parabronchial wall due to hyperplasia of local lymphoid formations (providing local immunity), signs of the development of interstitial pneumonia were revealed. Pathognomonic signs were found in the parenchyma - the formation of giant multinucleated cells, which is a characteristic sign of mycotic infections in poultry. The fusion of local pulmonary macrophages, histiocytes, into multinucleated cells is a prerequisite for the formation of granulomas, being a specific immune response in birds to the penetration of a pathogen. According to the development of the infectious process, caseous granulomas and fungal hyphae can be detected microscopically in the lungs. According to the results of histological examination, the formation of mycotic granulomas was found in the lung parenchyma in 7-10 days old chickens, which was accompanied by the formation of a zone of coagulation necrosis, in which the fungal hyphae were found. On the periphery, giant multinucleated epithelioid cells are located, the detection of which by histological examination is the basis for suspecting bird infection with microscopic fungi. Microscopic fungi Aspergillus flavus and Aspergillus fumigatus have been found in washes from hatchery ventilation cabinets, and Aspergillus flavus was found in the air from the chick sorting room and in washes from the feed mixer. Key words: aspergillosis, Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, micromycete, mold fungi, histiocytes, granulomas, phylaids, conidia, hyphae.

Expression of nutrient transporter genes in response to dietary rice gluten meal and protease enzyme supplementation and the consequent effects on growth, nutrient digestibility, immunity and jejunum histomorphometry in chicken

The objective of this study was to investigate the effects of feeding rice gluten meal (RGM) as an alternative protein source along with protease enzyme supplementation on growth performance, expression of nutrient transporter genes, nutrient digestibility, immune response and gut histomorphometry of broiler chicken. Proximate analysis of RGM revealed 923 g dry matter (DM), 500 g crude protein (CP), 69.2 g ether extract, 94.7 g crude fiber, 215.4 g nitrogen-free extract, 43.7 g ash, 6.20 g calcium, 7.80 g total phosphorus, 18.99 MJ gross energy and 12.68 MJ metabolizable energy per kg diet. Significant upregulation of nutrient transporter genes (PepT1, EAAT3 and mucin) and better growth performance was observed in the birds fed control diet which was statistically similar to the birds fed 150 g RGM compared to birds fed higher RGM levels. Histomorphometry of jejunum, nutrient digestibility, and immune response of birds did not reveal any significant effect of RGM or protease enzyme supplementation. However, the inclusion of RGM up to 150 g/kg diet resulted in significant decline of feed cost/kg live weight gain, dressed meat yield and eviscerated meat yield by 13.13%, 12.99% and 13.36%, respectively compared to control. Thus, it was concluded that the inclusion of 150 g RGM/kg diet in broiler chicken ration has no adverse effects on the growth pattern of birds and can be used for least-cost feed formulation for chicken.

Transcriptional cytokine responses associated with pathological outcomes in chickens experimentally infected with pigeon variant of avian avulavirus type 1

Background: Newcastle disease (ND) caused by virulent avian avulavirus 1 (AAvV-1) within the family paramyxoviridae, affects variety of avian species around the globe as well as responsible for significant economic losses in the poultry industry.Methods: Transcriptional response of selected cytokines associated with pathological outcomes were studied on chickens after experimental infection with three virulent isolates of pigeon variant avian avulavirus type 1 (PAvV-1). The specific pathogen free (SPF) chickens were used in the study, after virus inoculation via the intranasal route virus, observed daily for clinical symptoms. On day 3 of post infection, the experiment was terminated and then anatomopathogical and histopathological changes, virus load and transcriptional cytokine response were determined in the spleen.Results: For the study, four cytokines were chosen: interferons (IFN-β, IFN-γ) and interleukins (IL-2, IL-6). The increased transcriptional levels of cytokine expression were associated with viral gene expression and marked lesions. The increase in the mRNA levels of IL-6 was most significant in chickens with clinical symptoms. The combined up-regulations of IFN-γ and IL-6 mRNA expression were detected simultaneously with infiltration of macrophages in the histopathology analysis. The RNA expression of IL-2 and slight up-regulation of IFN-β were only in chickens infected with isolate closely related to poultry isolates in the phylogenetic study.Conclusions: The difference in the mRNA expression levels of cytokines may help to elucidate mechanisms of immune responses in birds infected with different virulent strains of avian avulavirus type 1.

Growth Performance, Caeca Microbial Population and Immune Response of Starter Broiler Chicks Fed Aqueous Extract of Balanites Aegyptiaca and Alchornea Cordifolia Stem Bark Mixture

A total of Two hundred and fifty (250), 1-day old (Cobb) broiler chicks with mixed sex were used to evaluate the the growth performance, caeca microbial population and immune response of starter broiler chicks fed aqueous extract of Balanites aegyptiaca and Alchornea cordifolia stem bark mixture (BACM). Birds were reared on a deep litter system and randomly divided into five treatment with five replicates consisting of 10 birds each in a completely randomized design. Treatment 1 (T1) were given basal diet + 0 % BACM, T2, T3, T4 and T5 were fed 20, 40, 60 and 80 ml/liter BACM respectively. The experiment lasted for 28 during which clean feed and water were offered ad libitum. The results obtained revealed that the average weight gain (AWG), feed conversion ratio (FCR) and mortality were influenced by the dietary treatments (P&lt;0.05). Birds in T5 had the highest AWG and FCR (1159.3 g, 1.57) followed by T4 (1070.2 g, 1.70), T3 (1047.4 g, 1.74), T2 (981.1 g, 1.86) and T1 (850.7 g, 2.14) respectively. Activities of superoxide dismutase (SDA), glutathione peroxidase (GPx), catalase (CAT) ,malonyldialdehyde (MLA) and antibody titres against Newcastle and gumboro disease were significantly affected by BACM (P&lt;0.05). Caeca microbial population of Escherichia coli and Lactobacilli were significantly different among the treatments (P&lt;0.05). E. coli count in T1 were higher compared to other treatments (P&lt;0.05), Lactobacilli population increased in T2, T3, T4 and T5 compared to T1. It was concluded that BACM can be fed to broiler chicks at 80 ml/litre without any negetive effect on the performance and immune response of birds.

Impact of road distance and experimental challenge of the maternal immune system on the offspring immunocompetence

The increasing number of roads is an important threat to living organisms on a global scale, although research describing the influence of roads on the immune response of birds is lacking. The main purpose of this study was to examine the effect of distance from the road on the chicks’ immune function. The research was conducted in the Krzyszkowice Forest near Kraków (S Poland) in spring 2012. Two common bird species: Great Tit and Eurasian Blue Tit bred in new nest boxes installed on trees with various distances from the road. In half of the nests, adult females were challenged with the antigen sheep red blood cells (SRBC) to check whether this experiment and the neighbourhood of road – both potentially lowering the immune response of nestlings – together cause an interactive effect.

Recombinant Newcastle Disease Virus (NDV) Expressing Sigma C Protein of Avian Reovirus (ARV) Protects against Both ARV and NDV in Chickens.

Newcastle disease (ND) and avian reovirus (ARV) infections are a serious threat to the poultry industry, which causes heavy economic losses. The mesogenic NDV strain R2B is commonly used as a booster vaccine in many Asian countries to control the disease. In this seminal work, a recombinant NDV strain R2B expressing the sigma C (σC) gene of ARV (rNDV-R2B-σC) was generated by reverse genetics, characterized in vitro and tested as a bivalent vaccine candidate in chickens. The recombinant rNDV-R2B-σC virus was attenuated as compared to the parent rNDV-R2B virus as revealed by standard pathogenicity assays. The generated vaccine candidate, rNDV-R2B-σC, could induce both humoral and cell mediated immune responses in birds and gave complete protection against virulent NDV and ARV challenges. Post-challenge virus shedding analysis revealed a drastic reduction in NDV shed, as compared to unvaccinated birds.

Gene expression and antibody response in chicken against Salmonella Typhimurium challenge

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a primary avian pathogen responsible for severe intestinal pathology in younger chickens and economic losses to poultry industry. Furthermore, S. Typhimurium is also able to cause infection in humans, characterized by acute gastrointestinal disease. A study was conducted to investigate antibody response and expression kinetics of interferon gamma (IFNγ), interleukin (IL-12, and IL-18) genes in broiler chicken at 0, 1, 3, 5, 7, 9, 11, 13, and 15D post infection following experimental infection of S. Typhimurium. Immunological studies showed higher titres of IgG and IgM in the infected group as compared to the age-matched un-infected control group. The Real-Time PCR-based gene expression analysis revealed significant increase of IFNγ, IL-12, and IL-18 mRNA levels in the infected group as compared to their respective controls (P < 0.05). The present study shall help in understanding the immune responses in birds, thus allowing development of more effective vaccines and vaccination strategies.

Characterization of Immune and Enteric Systems of Broilers after Imunosupression with Dexamethasone

Background: Bursa of Fabricius (BF) and the thymus are primary lymphoid organs of poultry and play a major role in avian immunity. Enteric system is also involved in immunity. Several pathologic conditions directly impact BF and thymus size, and also affect intestinal parameters. Besides, there are several immune system depressor agents which affect birds. The selection of glucocorticoid as inducer of immunosuppression is applied in many experiments; however there are few studies that are applied to the reality in the field. In this context, the aim of this study was to evaluate the effects of dexamethasone as an inducer of immunosuppression on lymphoid organs and microscopic structures of the jejunum.Materials, Methods &amp; Results: One-day-old chicks were used as a control group (n = 8) and the treated group (n = 25) received intramuscular dexamethasone on 21, 23, 24 and 26 day-old. Control birds and treated birds were euthanized 8, 16, 24, 32 and 40 h after inoculation; four control birds and six treated birds were euthanized on the eighth day after the last inoculation. Thymus, BF and jejunum were collected during the necropsy. The selected organs were processed, stained with hematoxylin and eosin and photographed. The BF and thymus cuts were evaluated by three histopathologists to determine the depletion score. Ten villi of each jejunum were evaluated for width and length of villi, depth crypt, microvillus length, enterocyte length of each villus, and wall thickness. Treated birds presented a mean weight lower than control group during all the experiment. The mean weight and the relative weight of the BF and thymus of control birds were significantly higher than treated ones. The lymphocyte depletion in BF and thymus scores differed significantly between groups, being higher in the group challenged with dexamethasone. There were no significant differences between groups for depth of crypt, height of core and height of microvilli. The intestines of the control group had higher mean values for length of villi, width of villi, height of enterocyte and thickness of wall. Significant correlation between weight of thymus and weight of BF, between weight of thymus and weight of bird and between weight of BF and bird weight were found.Discussion: Easy administration, low cost and the absence of suffering during inoculation make the use of glucocorticoids more advantageous to mimic immunosupression in poultry. Treatment with dexamethasone interfered directly in the weight of the birds. Evaluation of immune response of birds can be performed by the ratio of the BF weight in relation to the weight of the bird, as observed in the present study. The relative weight of the BF of untreated animals varied at all ages between 0.21% and 0.29%. It was also observed that the relative weight of BF and thymus in immunosuppressed birds tended to increase according to the end of the treatment. Depletion scores were higher in thymus, suggesting that glucocorticoid promoted more harmful effects on this organ. Dexamethasone had negative influence on length of villus, once mean value was 13% lower than those of control group. Width of villus and height of enterocyte core of treatment group were lower than those observed in control animals. Coefficient of determination greater than 70% was observed for almost all established relationships, except for the length of villi and weight of the thymus. Administration of dexamethasone promotes significant and negative effects on the gain of weight, length of villi, width of villi and height of enterocytes. These finding are useful for future experiments with controlled immunosuppression induction, once it provides significant information of the secondary effects of glucocorticoids administration in poultry.

Effect of stocking density on productive performance, behaviour, and histopathology of the lymphoid organs in broiler chickens

Abstract Stocking density is one of the most important aspects of management in poultry production and considered a major concern in terms of the welfare of birds. It can also be a factor predisposing to stress and disease in birds. The aim of this study was to assess the effect of three different levels of stocking density on the productive performance and behaviour of broilers, as well as pathologic changes in the lymphoid organs that reflect immune status. Cobb 500 broilers were allocated to three groups with different stocking density: 10 birds/m 2 (Group 1), 15 birds/m 2 (Group 2), and 20 birds/m 2 (Group 3). Body weight was recorded weekly and weight gain was calculated from the data obtained. The behavioural patterns of the birds were recorded. On day 23 of the experiment, three birds from each stocking density group were injected with 10% sheep red blood cells and killed 10 days later. The thymus, bursa of Fabricius, and spleen were removed for histopathologic examination. Higher stocking density negatively affected final body weight as well as cumulative body weight gain. The higher density was also associated with decreased crouching, walking, preening, body care behaviour, and ingestive behaviour. Birds in the high stocking density group showed severe diffuse and extensive necrosis of the bursal follicles as well as atrophy and depletion of the splenic lymphoid nodules. These lymphoid organ disorders suggest that high stocking density compromises the immune response in birds. The negative effect of high stocking density on final body weight would decrease profitability.

The Impact of the Female Immune Challenge on Parental Feeding Rate, Mass and Body Condition Index of Offspring

Reproduction is a resource-demanding period, when trade-offs between investment in immunity versus other functions of an adult organism may exist. This research investigates the potential trade-off between a challenged immune system of a female parent and parental provisioning in free-living Great Tits Parus major and Eurasian Blue Tits Cyanistes caeruleus. In both species, half of females were challenged with sheep red blood cells (SRBC) as an antigen, while the others were injected with phosphate buffer saline (PBS) as a control. Six days later – at the day assumed to be the peak of an immune response in birds treated with SRBC, when nestlings were nine days old – parental feeding rates were recorded. Two days later (and eleven days after hatching), nestling mass and body condition index (BCI) were quantified. SRBC challenge of the female increased feeding rates of Great Tit males and females, but did not change parental provisioning in Eurasian Blue Tits. This may be explained by the different reproductive strategies in these two bird species. Parental provisioning influenced the mass and BCI of offspring. In both species, offspring mass was lower and BCI was higher in the SRBC group than those in the control group. This means that high providers, such as Great Tits with increased feeding rates, do not always raise chicks with high fledgling mass. Parental provisioning is one of the key factors linking reproduction and the immune system.