Understanding stress-induced immunosuppression: exploration of cytokine and chemokine gene profiles in chicken peripheral leukocytes

Effects of heat stress on the gut health of poultry

Stress is a biological adaptive response to restore homeostasis, and occurs in every animal production system, due to the multitude of stressors present in every farm. Heat stress is one of the most common environmental challenges to poultry worldwide. It has been extensively demonstrated that heat stress negatively impacts the health, welfare, and productivity of broilers and laying hens. However, basic mechanisms associated with the reported effects of heat stress are still not fully understood. The adaptive response of poultry to a heat stress situation is complex and intricate in nature, and it includes effects on the intestinal tract. This review offers an objective overview of the scientific evidence available on the effects of the heat stress response on different facets of the intestinal tract of poultry, including its physiology, integrity, immunology, and microbiota. Although a lot of knowledge has been generated, many gaps persist. The development of standardized models is crucial to be able to better compare and extrapolate results. By better understanding how the intestinal tract is affected in birds subjected to heat stress conditions, more targeted interventions can be developed and applied.

Effect of dietary β-1,3-glucan supplementation and heat stress on growth performance, nutrient digestibility, meat quality, organ weight, ileum microbiota, and immunity in broilers

The objective of this study was to determine the effect of dietary β-1,3-glucan supplementation and heat stress (HS) on growth performance, nutrient digestibility, meat quality, organ weight, ileum microbiota, and immunity in broiler. A total of 1,440 1-day-old Ross 308 male chicks with an average initial BW of 43.06 ± 1.94 g were sorted into 6 (2 × 3) treatments, 14 replications per treatment. This trail included 2 factors: the dosage of β-1,3-glucan (0, 100 g/T, and 200 g/T) and feeding condition (HS and normal). During the whole trial, significant impacts were observed in BW gain, feed intake，feed conversion rate, and the digestibility of DM and energy between normal treatments and HS treatments (P < 0.05). From day 21 to 35, HS-challenged birds fed the diet with 200 g/T β-1,3-glucan had a lower feed conversion rate than those fed the diet with 0 or 100 g/T β-1,3-glucan (P < 0.05). Moreover, the HS-exposed birds that fed the diet with β-1,3-glucan indicated a greater energy digestibility than those fed the nontreatment diet (P < 0.05). Besides, β-1,3-glucan supplementation could elevate meat pH of all birds and decrease cooking loss significantly of HS-exposed birds (P < 0.05). The HS birds fed the β-1,3-glucan diet obtained a reduced amount of Escherichia coli in the ileum than those fed the nontreatment diet (P < 0.05). Besides, β-1,3-glucan supplementation lowered the level of tumor necrosis factor-α in HS-exposed birds significantly (P < 0.05). These results indicated 100 and 200 g/T β-1,3-glucan supplementation, under HS condition or not, can increase growth performance without a negative response on immunity. Under HS condition, the addition of β-1,3-glucan at dosage from 100 to 200 g/T in the diet can increase energy digestibility, decrease cooking loss, reduce E. coli mount in the ileum, and the tumor necrosis factor-α concentration.

Identification of genes related to effects of stress on immune function in the spleen in a chicken stress model using transcriptome analysis

Stress is a physiological manifestation of the body's defense against adverse effects of external environment, but the molecular regulatory mechanism of stress effects on immune function of poultry has not been fully clarified. In this study, 7-day-old Chinese local breed Gushi cocks were used as model animal, and the stress model was successfully constructed by adding corticosterone (CORT) 30 mg/kg basic diet for 7 days. The spleen transcriptomes of the control group (B_S group) and the stress model group (C_S group) was determined by high-throughput mRNA sequencing (RNA-Seq) technology, and a total of 269 significantly differentially expressed genes (SDEGs) were obtained (Padj < 0.05, |FC| ≥ 2 and FPKM > 1). Compared with B_S group, there were 140 significantly up-regulated genes and 129 significantly down-regulated genes in C_S group. The immune/stress-related Gene Ontology (GO) terms included positive regulation of T cell mediated immunity, chemokine-mediated signaling pathway, T cell mediated immunity and so on. The SDEGs such as IL8L1, HSPA8, HSPA2, RSAD2, CCR8L and DMB1 were involved in these GO terms. Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis showed that the SDEGs participated in many immune-related signaling pathways. The immune-related genes HSPA2, HSPA8, HSP90AA1, HSPH1 and HERPUD1 were enriched in Protein processing in endoplasmic reticulum pathway, IL8L1, CXCL13L2, CCR6, LEPR, CCR9 and CCR8L were enriched in Cytokine-cytokine receptor interaction pathway. The protein-protein interactions (PPI) analysis showed HSPA8, HSPA2 and IL8L1 as key core nodes had 7 interactions and may play important roles in the regulation of CORT-induced stress effects on immune function. The data onto this study enriched the genomic study of stress effects on immune function, and provided unique insights into the molecular mechanism of stress effects on immune function, and the genes identified in this study can be candidates for future research on stress response.

Transcriptomic Analysis of Spleen Revealed Mechanism of Dexamethasone-Induced Immune Suppression in Chicks

Stress-induced immunosuppression is a common problem in the poultry industry, but the specific mechanism of its effect on the immune function of chicken has not been clarified. In this study, 7-day-old Gushi cocks were selected as subjects, and a stress-induced immunosuppression model was successfully established via daily injection of 2.0 mg/kg (body weight) dexamethasone. We characterized the spleen transcriptome in the control (B_S) and model (D_S) groups, and 515 significant differentially expressed genes (SDEGs) (Fragments Per Kilobase of transcript sequence per Millions base pairs sequenced (FPKM) > 1, adjusted p-value (padj) < 0.05 and Fold change (|FC|) ≥ 2) were identified. The cytokine-cytokine receptor interaction signaling pathway was identified as being highly activated during stress-induced immunosuppression, including the following SDEGs-CXCL13L2, CSF3R, CSF2RB, CCR9, CCR10, IL1R1, IL8L1, IL8L2, GHR, KIT, OSMR, TNFRSF13B, TNFSF13B, and TGFBR2L. At the same time, immune-related SDEGs including CCR9, CCR10, DMB1, TNFRSF13B, TNFRSF13C and TNFSF13B were significantly enriched in the intestinal immune network for the IgA production signaling pathway. The SDEG protein-protein interaction module analysis showed that CXCR5, CCR8L, CCR9, CCR10, IL8L2, IL8L1, TNFSF13B, TNFRSF13B and TNFRSF13C may play an important role in stress-induced immunosuppression. These findings provide a background for further research on stress-induced immunosuppression. Thus, we can better understand the molecular genetic mechanism of chicken stress-induced immunosuppression.

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

Background

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

Results

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

Conclusion

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

Dietary curcumin supplementation effects on blood immunological profile and liver enzymatic activity of laying hens after exposure to high temperature conditions

Various environmental factors affect livestock production but heat stress is a major challenge in the poultry farming. Poultry exposes to high temperature alters blood immunological parameters and liver enzymatic function which in turn, suppress the immunity and disease resistance of chickens. Thus, the purpose of present study was to explore the effect of dietary curcumin supplementation on blood immunological biomarker and liver enzymatic activity of laying hens under heat stress conditions. Experimental groups contained two control groups (normal temperature control (NC) and heat stress control (HC) and 3 heat stress curcumin treatment groups (HT100, HT200 and HT300). Hens in HC group with basal diet and heat stress curcumin treatment groups were exposed 6 h/day heat stress (32 ± 1 °C) from 10:00 a.m. to 16:00 p.m. for 9 week. The results of present study showed that heat stressed curcumin treatment group had improved liver weight, WBC values and immunoglobulin level as compared to untreated HC and NC groups. The available results also indicated that laying hens supplemented with curcumin under high temperature conditions had reduced H/L ratio, serum corticosterone levels, inflammatory cytokines response and liver enzymatic activity (ALT) which enhanced the immunity of laying hens under hot climatic conditions. Therefore, it is concluded that curcumin has ability to combat harsh environmental conditions which can be used as anti-inflammatory and immune booster feed additive in the poultry nutrition.

Effects of induced stress from the live LaSota Newcastle disease vaccination on the growth performance and immune function in broiler chickens

This study was conducted to assess the growth performance and immunological effects of vaccination-induced stress on broilers. The chickens were administered 0, 2, 4, 8, and 16 doses of live LaSota Newcastle disease (ND) vaccine and slaughtered on the 1st, 7th, 14th, and 21st day post vaccination. The results showed that the serum antibody titers after Newcastle disease virus (NDV) vaccination were elevated at day 7 post vaccination, peaked at day 14, then declined by day 21. Interestingly, the antibody titers peaked at 2 doses, and no further dose-dependent titer increases were observed. This study demonstrated that vaccination-induced stress increased serum adrenocorticotropic hormone and cortisol, affected growth performance (average daily gain, average daily feed intake, and feed conversion ratio), and triggered apoptosis in spleen lymphocytes by downregulating the ratio of Bcl-2 to BAX and upregulating the gene expressions of caspase-3 and -9, which was concordant with the activation of the enzymatic activities of caspase-3 and -9. This study suggests that NDV vaccine doses in broilers must be controlled judiciously because increasing the number of doses resulted in increased lymphocyte apoptosis while the peak of the antibody titer and optimal growth performance were achieved at a low number of doses (2 doses).

Effect of Housing System and Rosemary and Cinnamon Essential Oils on Layers Performance, Egg Quality, Haematological Traits, Blood Chemistry, Immunity, and Antioxidant

Simple Summary

The current study aimed to investigate the effects of a housing system, and dietary supplementation of rosemary and cinnamon essential oils on layers performance and egg quality. A factorial arrangement (2 × 3) was performed including two housing systems (floor and cage) and three different types of essential oils (0, 300 mg/kg diet of rosemary and 300 mg/kg diet of cinnamon essential oils) to study their effects on the productive performance, egg quality, immunity, oxidative stress and haematology of laying hens during the production stages. The data suggested that the supplementation of rosemary and cinnamon essential oils in laying hen diet showed significant positive effects on hen performance and egg production. Additionally, the different housing systems did not result in any positive or negative impact on these traits.

Abstract

Housing system and nutrition are non-genetic factors that can improve the well-being of animals to obtain higher quality products. A better understanding of how different housing systems and essential oils can influence the performance of layers is very important at the research and commercial levels. The current study aimed to investigate the effects of a housing system and dietary supplementation of rosemary and cinnamon essential oils on layers’ performance and egg quality. A factorial arrangement (2 × 3) was performed include two housing systems (floor and cage) and three different types of essential oils (0, 300 mg/kg diet of rosemary and 300 mg/kg diet of cinnamon essential oils) to study their effects on the productive performance, egg quality, immunity, oxidative stress and haematology of ISA brown laying hens during the production stages (from 28 to 76 weeks of age). Birds were randomly divided into two groups each comprising of 1500 birds; the first group was moved from the litter to reared laying cages while the second group was floor reared. Each group was randomly divided into three groups, the first was considered as a control group, the second treated with rosemary essential oil, and the third with cinnamon essential oil. The differences in egg production and weight, egg quality, feed intake and conversion, blood picture and chemistry, immunity, and antioxidant parameters between the different housing systems (floor and cage) were not significant at (p < 0.05 or 0.01). On the other hand, the egg production and weight, Haugh unit, feed intake and conversion, blood cholesterol, Alanine Aminotransferase (ALT), Aspartate Aminotransferase (AST), urea, Ca, P, immunity, and antioxidant parameters were significantly (p < 0.05 or 0.01) better in rosemary and cinnamon groups than in the control group. Furthermore, the results of dietary supplementation with rosemary and cinnamon were very close. Regarding egg production and weight, there were no significant differences due to the interactions. The differences in egg mass among the interactions were also not significant except at 68–76 weeks, where the cage × cinnamon group was the highest. Under the floor rearing system, birds that were fed a diet supplemented with or without essential oils (EOs) consumed more feed than those raised under the cage system. Regarding feed conversion rate (FCR), the differences among the interactions were not significant except at 44–52, 52–60 and 68–76 weeks, where the cage × cinnamon group was the lowest. Excluding glutathione peroxidase (GPx) activity (p < 0.001), all immunity and antioxidant indices were not statistically different as a consequence of the interaction among EOs and housing systems. Additionally, the highest levels of phosphorus were observed for layers fed diets enriched with cinnamon oil with the cage or floor system. In conclusion, the data suggested that supplementation of rosemary and cinnamon essential oils in laying hen diet showed significantly positive effects on hen performance and egg production. Cholesterol, liver and kidney functions, immunity, and antioxidant parameters improved with rosemary and cinnamon supplementation when compared to the control. Additionally, the different housing systems did not result in any positive or negative impact on these traits.

Genomic Characterization of Antibiotic Resistant Escherichia coli Isolated From Domestic Chickens in Pakistan

Poultry husbandry is important for the economic health of Pakistan, but the Pakistani poultry industry is negatively impacted by infections from Escherichia coli. We performed Illumina whole genome sequencing on 92 E. coli isolates obtained from the livers of deceased chickens originating in five Pakistani geographical regions. Our analysis indicates that the isolates are predominantly from the B1 and A clade and harbor a diverse number of antibiotic resistance and virulence genes, with no linkage between phylogeny and antibiotic resistance gene presence but some association between phylogeny and virulence gene and SNP presence for the B1 and E phylogroups. The colistin resistance gene mcr-1 and the quinolone resistance gene qnrS1 were both found in 13/92 isolates. Alarmingly, 82/92 of the E. coli strains characterized in this study are multidrug resistant with 100% (92/92) resistance to lincomycin, 81.5% (75/92) to streptomycin, 79.3% (73/92) to ampicillin and 66.3% (61/92) to ciprofloxacin. These results provide a high-resolution analysis of poultry-associated E. coli isolates in an area with a high endemic burden of antibiotic resistance. Surveillance of antibiotic resistance in poultry associated E. coli isolates is an important pillar of the One Health concept to integrate analysis of potential pathogens in human, animal, and environmental niches.

Indústria do Ovo: qual é o significado e uso dessa expressão?

Resumo No início dos anos 2000, ovos foram reabilitados como saudáveis, sendo alimento nutritivo e economicamente acessível, de uma rica fonte de proteína animal e uma alternativa à carne vermelha. O presente trabalho objetivou identificar se a expressão “Indústria do Ovo” é utilizada em publicações acadêmicas e, se confirmada sua utilização, a que produção se refere frequentemente, bem como em que contexto é utilizada quanto à temática dos artigos científicos. Para tanto, realizou-se uma revisão sistemática da literatura, considerando investigações publicadas nas bases de dados Scopus e Web of Science. Os resultados obtidos demonstraram que a utilização da expressão “Indústria do Ovo” em artigos científicos ocorre desde 1947, sendo empregada para designar, principalmente, a produção comercial de ovos de galinha, cujo uso apresenta linha de tendência crescente. Os artigos com foco em administração, economia, mercados e certificações foram predominantes no emprego da expressão “Indústria do Ovo” no decorrer do período analisado.

Supplementation of a water-soluble zinc-AA complex to reduce stress in broilers, pullets, and layers1

This study consisted of three 5-wk experiments to test the effects of administering Zinpro-LQ (Zinpro-LQ, Zinpro Corporation, Eden Prairie, MN) for different time intervals in stressed broilers, pullets, and layers. Treatments included: nonstressed control (NC), stressed control (SC), stressed and supplemented Zinpro-LQ for 14 d prior to stressor (S1), 10 d prior (S2), 7 d prior to and 7 d during stressor (S3), and 5 d prior (S4). Birds included 1-d-old Cobb 500 male broilers (Experiment 1), 7-wk-old white Leghorn pullets (Experiment 2), and 50-wk-old white Leghorn layers (Experiment 3). All stressed birds were vaccinated against Newcastle Disease Virus (NDV) on day 28 and exposed to random feed and water withdrawal days 28 to 35 for 6 h/d. Pullets were beak trimmed on day 21, and layers were heat stressed days 28 to 35. Blood was sampled on day 35 to determine plasma chemistry, corticosterone (CORT), anti-NDV antibody titer, and heterophil/lymphocyte (H/L) ratio. Mortality, feed and water consumption, and BW were also recorded. In Experiment 1, CORT and H/L ratio were highest in SC (P < 0.05). In Experiment 2, CORT was higher in SC than S4 (P < 0.05) while all other treatments were statistically intermediate. NDV titer was lower in SC than S4 while all other treatments were statistically intermediate. Treatment differences were also observed for H/L ratio, and plasma uric acid and cholesterol in Experiment 2. In Experiment 3, treatment differences were observed for H/L ratio, plasma glucose, sodium, and chloride. H/L ratio was lower in NC, S1, and S4 compared with SC (P < 0.05); and NC and S1 were lower than S2 (P < 0.05). In conclusion, dietary inclusion of zinc AA complex for any length of time prior to a stressor helped reduce measures of stress in broilers. The S1 and S4 treatments helped reduce stress and improve humoral immune response in pullets and layers.

Virus-induced immunosuppression in turkeys (Meleagris gallopavo): A review

Immunosuppression is characterized by a dysfunction of humoral and/or cellular immune response leading to increase of susceptibility to secondary infections, increase of mortality and morbidity, poor productivity, and welfare and vaccination failures. Humoral immune response depression is due to perturbation of soluble factors, as complement and chemokines in innate immunity and antibodies or cytokines in adaptive immunity. At the cellular immune response, immunosuppression is the consequence of the dysfunction of T-cells, B-cells, heterophils, monocytes, macrophages, and natural Killer cells. Immunosuppression in turkeys can be caused by numerous, non-infectious, and infectious agents, having variable pathological and molecular mechanisms. Interactions between them are very complex. This paper reviews the common viruses inducing clinical and sub-clinical immunosuppression in turkeys, and enteric and neoplastic viruses in particular, as well as the interactions among them. The evaluation of immunosuppression is currently based on classical approach; however, new technique such as the microarray technology is being developed to investigate immunological mediator’s genes detection. Controlling of immunosuppression include, in general, biosecurity practices, maintaining appropriate breeding conditions and vaccination of breeders and their progeny. Nevertheless, few vaccines are available against immunosuppressive viruses in turkey’s industry. The development of new control strategies is reviewed.

Effect of heat stress on the quantitative expression patterns of different cytokine genes in Malabari goats

A study was conducted to determine the influence of exposure to hot environment on different cytokine gene expression patterns in Malabari goat. The study was conducted in 12 (10 months to 1 year old) goats of Malabari breed for 45-day duration. The control (n = 6; C) group goats were kept under comfortable condition in the shaded pens while heat stress (n = 6; HS) group goats were kept out in the open hot environment during summer season for the study duration between 10.00 h to 16.00 h. The representative mesenteric lymph node (MLN) samples were collected from the slaughtered goats at the end of study for assessing the different cytokine gene expression and histopathological changes. Compared with C group, the expression patterns of interleukin 18 (IL-18), tumor necrosis factor-α (TNF-α), interferon-β (IFN-β), and IFN-γ downregulated (P < 0.05) in the HS group. The histopathological changes of MLNs showed paucity of lymphocyte distribution in follicular areas as wells as decreased density of lymphocytes in the germinal centers of the HS group (P < 0.05). The findings from this study reflected the compromised immune functions during heat stress in Malabari goats. Further, the study established that IL-18, TNF-α, IFN-β, and IFN-γ genes could serve as reliable immunological markers for quantifying heat stress-mediated immune response alterations in Malabari goats.

Effect of curcumin supplementation on TLR4 mediated non-specific immune responses in liver of laying hens under high-temperature conditions

The liver performs a significant role in innate and adaptive immunity. Heat stress causes oxidative stress in liver tissues and reduces the immune responses of laying hens which can cause several diseases affecting poultry-production performance. Hepatic inflammation is a common trigger of liver disease, which is reflected by hepatic tissue damage leading to fibrogenesis and hepatocellular carcinoma. Dietary manipulation of curcumin has been proposed to ameliorate the immune status of chickens under heat stress. Thus, this study aimed to investigate the effect of curcumin supplementation on TLR4 mediated non-specific immune response in liver of laying hens under high-temperature conditions. Experimental groups contained two controls groups (high temperature and thermo-neutral control (HC and NC) fed basal diet) and three high-temperature curcumin treatments groups (HT100, HT200 and HT300). Laying hens in HC and HT groups exposed 6 h/day heat stress (32 ± 1 °C). The results of present study showed that heat stress curcumin treatment group had reduced inflammatory responses (IL-6, IL-1β, TNF-α) as compared to HC and NC group. Pathological lesions and DNA damage of immune tissues were decreased in heat stress curcumin supplementation as compared to HC and NC group. Furthermore, PCNA, TLR4 and its downstream gene expression as well as protein expression (TLR4, NF-κB and PCNA) were significantly down regulated in heat stress curcumin supplemented group as compared to HC and NC group. Therefore, it is concluded that heat stressed hens supplemented with dietary curcumin enhance the immunity of laying hens and combat stressful environmental conditions.

Effect of sulfated yeast beta-glucan on cyclophosphamide-induced immunosuppression in chickens

Immunosuppression is a condition that causes large economic losses in the poultry industry. To investigate the effect of sulfated yeast beta-glucan on immunosuppression, two hundred and fifty 11-day-old chickens were randomly assigned to five groups, and except for the normal control group, injected with cyclophosphamide once a day for 3 successive days. At 14 days of age, sulfated yeast beta-glucan from Saccharomyces cerevisiae(sGSC) was orally administered at three doses to the chickens in three experimental groups for 14 days. On days 7 and 14 after the first sGSC dose, serum cytokine concentrations and peripheral lymphocyte proliferation were measured. Gut microbiota, organ index, and histopathological changes in the bursa were investigated on day 14. The results demonstrated that at 4 mg/kg, sGSC could significantly enhance the bursa index and IFN-γ and IL-6 concentrations, decrease TGF-β1 concentration, and promote lymphocyte proliferation; it could effectively decrease histopathological changes in the bursa and improve gut Bifidobacterium and Lactobacillus populations in cecal digesta of chickens compared with the model control group. This indicated that sGSC could effectively alleviate immunosuppression and regulate the beneficial microbiota in the gut.

Propolis alleviates the negative effects of heat stress on egg production, egg quality, physiological and immunological aspects of laying Japanese quail

The present work was carried out to investigate the effects of dietary propolis supplementation to laying Japanese quail (Coturnix coturnix japonica) on egg production, egg quality, physiological and immunological aspects under heat stress conditions. A total of 200, 21-day-old, Japanese quail females were distributed equally into standard wired cages in two identical environmentally-controlled rooms (10 cages per room, 10 birds per cage). From 29–70 d of age, the quail birds in the first room remained at a normal temperature of 24°C (C group), whereas the quail birds in the second room were kept under heat stress at 35°C (HS group). Each group was further assigned to 2 propolis subgroups (5 cages per subgroup); one of them received a basal diet without propolis supplementation (-PR subgroup), while, the other received 1 g propolis/ kg basal diet (+PR subgroup). In the present study, performance and egg production of laying quail were significantly (P<0.001) impaired by HS treatment and improved by the PR treatment. Similarly, the negative and positive effects of HS and PR, respectively, were appeared on the egg shell thickness and yolk index. Stress indicators in laying quail were significantly (P<0.001) increased by HS, while, PR significantly (P<0.05) moderated these levels in the HS+PR group when compared to the HS-PR quail group. In addition to the positive impact of PR on the plasma levels of calcium, phosphorus, and albumin, it also normalized the plasma levels of alanine aminotransferase and cholesterol in the heat-stressed quail birds. Moreover, the quail birds in the HS groups expressed lower immunological aspects than those in the C group, while, the addition of propolis to the diets enhanced the immune status of laying quail birds under HS conditions. These results strongly suggest that dietary propolis supplementation could be a successful attempt to maintain the performance and egg production of laying Japanese quail at convenient levels under heat stress conditions.

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

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

Environmental complexity: A buffer against stress in the domestic chick

Birds kept in commercial production systems can be exposed to multiple stressors from early life and this alters the development of different morphological, immunological and behavioural indicators. We explore the hypothesis that provision of a complex environment during early life, better prepares birds to cope with stressful events as well as buffers them against future unpredictable stressful episodes. In this study, 96 one day old pullets were randomly distributed in eight pens (12 birds/pen). Half of the chicks (N = 48) were assigned to a Complex Environment (CENV: with perches, a dark brooder etc.) the others to a Simple Environment (SENV: without enrichment features). Half of the birds from each of these treatments were assigned to a No Stress (NSTR, 33°C) or to an acute Cold Stress (CSTR, 18–20°C) treatment during six hours on their second day of life. At four weeks of age, chicks with these four different backgrounds were exposed to an Intermittent Stressful Challenges Protocol (ISCP). In an immunological test indicative of pro-inflammatory status Phytohemagglutinin-P (PHA-P), the response of CSTR birds was ameliorated by rearing chicks in a CENV as they had a similar response to NSTR chicks and a significantly better pro-inflammatory response than those CSTR birds reared in a SENV (five days after the CSTR treatment was applied). A similar better response when coping with new challenges (the ISCP) was observed in birds reared in a CENV compared to those from a SENV. Birds reared in the CENV had a lower heterophil/lymphocyte ratio after the ISCP than birds reared in SENV, independently of whether or not they had been exposed to CSTR early in life. No effects of stress on general behaviour were detected, however, the provision of a CENV increased resting behaviour, which may have favoured stress recover. Additionally, we found that exposure to cold stress at an early age might have rendered birds more vulnerable to future stressful events. CSTR birds had lower humoral immune responses (sheep red blood cells induced antibodies) after the ISCP and started using elevated structures in the CENV later compared to their NSTR conspecifics. Our study reflects the importance of the early provision of a CENV in commercial conditions to reduce negative stress-related effects. Within the context of the theory of adaptive plasticity, our results suggest that the early experience of the birds had long lasting effects on the modulation of their phenotypes.

Effect of embryonic thermal manipulation on heat shock protein 70 expression and immune system development in Pekin duck embryos

Two experiments were conducted to study the effects of thermal manipulation on heat shock protein 70 (HSP70) transcription and immune cell characteristics' in Pekin duck embryos. In experiments I and II, fertile duck eggs were incubated at either a standard (S; 37°C) or high (H; 38.0°C) temperature from embryonic day (ED) 1 to 10. At ED11, half the eggs incubated at 37.5°C or 38.0°C were either kept at 37.5°C (SS) or 38.0°C (HH) respectively, or moved to the opposite incubator/temperature of either 38.0°C (SH) or 37.5°C (HS). Beginning on ED 21, all eggs (embryos) were incubated at 37.5°C. In experiments I and II, the mean egg shell temperature (EST) of eggs incubated at 38.0°C was higher than that from 37.5°C at ED10 (P < 0.01). In both experiments, the yolk free wet embryo body weight (YFWEBW) of embryos from the HS treatment was increased while that in the HH treatments was decreased compared with the SS treatment at ED25 (P < 0.01). In experiment II, embryos from the HH treatment had increased HSP70 mRNA compared with the SS treatment in the liver, thymus, and bursa (P < 0.05). The thymus and bursa from embryos in the SH treatment had increased MHCI mRNA when compared with the SS treatment (P < 0.05). The thymus from HH and SH treatments had increased MHCII mRNA while the bursa from the HH and SH treatments had decreased MHCII mRNA when compared with the SS treatment (P < 0.05). The spleen and bursa from the HH treatment had increased IL-6, IFNγ, and IL-10 mRNA when compared with the SS treatment (P < 0.05). The thymus and spleen from embryos in the HH treatment had increased CD8+/CD4+ ratios and CD4+CD25+ cell percentages compared with the SS treatment (P < 0.05). In conclusion, embryos incubated at 0.5°C higher than the standard incubation temperature from ED1 to 21 had increased HSP70 mRNA, MHCI, and inflammatory cytokines, and the immune response was skewed toward cell-mediated immunity.

A review of environmental enrichment for laying hens during rearing in relation to their behavioral and physiological development

Globally, laying hen production systems are a focus of concern for animal welfare. Recently, the impacts of rearing environments have attracted attention, particularly with the trend toward more complex production systems including aviaries, furnished cages, barn, and free-range. Enriching the rearing environments with physical, sensory, and stimulatory additions can optimize the bird's development but commercial-scale research is limited. In this review, "enrichment" is defined as anything additional added to the bird's environment including structurally complex rearing systems. The impacts of enrichments on visual development, neurobehavioral development, auditory stimulation, skeletal development, immune function, behavioral development of fear and pecking, and specifically pullets destined for free-range systems are summarized and areas for future research identified. Visual enrichment and auditory stimulation may enhance neural development but specific mechanisms of impact and suitable commercial enrichments still need elucidating. Enrichments that target left/right brain hemispheres/behavioral traits may prepare birds for specific types of adult housing environments (caged, indoor, outdoor). Similarly, structural enrichments are needed to optimize skeletal development depending on the adult layer system, but specific physiological processes resulting from different types of exercise are poorly understood. Stimulating appropriate pecking behavior from hatch is critical but producers will need to adapt to different flock preferences to provide enrichments that are utilized by each rearing group. Enrichments have potential to enhance immune function through the application of mild stressors that promote adaptability, and this same principle applies to free-range pullets destined for variable outdoor environments. Complex rearing systems may have multiple benefits, including reducing fear, that improve the transition to the layer facility. Overall, there is a need to commercially validate positive impacts of cost-effective enrichments on bird behavior and physiology.

Transcriptome profile in bursa of Fabricius reveals potential mode for stress-influenced immune function in chicken stress model

BACKGROUND

The molecular mechanisms underlying stress-influenced immune function of chicken (Gallus Gallus) are not clear. The stress models can be established effectively by feeding chickens corticosterone (CORT) hormone. The bursa of Fabricius is a unique central immune organ of birds. RNA-Seq technology was used to investigate differences in the expression profiles of immune-related genes and associated pathways in the bursa of Fabricius to clarify molecular mechanisms. The aim of this study was to broaden the understanding of the stress-influenced immune function in chickens.

RESULTS

Differentially expressed genes (DEGs) in the bursa of Fabricius between experimental group (basal diet with added CORT 30 mg/kg; C_B group) and control group (basal diet; B_B group) were identified by using RNA-seq technology. In total, we found 1434 significant DEGs (SDEGs), which included 199 upregulated and 1235 downregulated genes in the C_B group compared with the B_B group. The immune system process GO term was the top significantly GO term, including MYD88, TLR4, IL15, VEGFA gene and so on. The cytokine-cytokine receptor interaction pathway and the Toll-like receptor signaling pathway were the key pathways affected by stress. The protein-protein interaction (PPI) analysis of the SDEGs showed that VEGFA, MyD88 and IL15 were hub genes and module analysis showed that MYD88, TLR4 and VEGFA play important roles in response to stress.

CONCLUSION

This study showed that the VEGFA and ILs (such as IL15) via the cytokine-cytokine receptor interaction pathway, MYD88 and TLR4 via the Toll-like receptor signaling pathway may play important roles in the regulation of immune function under stress condition with CORT administration. The results of this study provide a reference for further studies of the molecular mechanisms of stress-influenced immune function.

Immunomodulatory effect of γ-irradiated Astragalus polysaccharides on immunosuppressed broilers

In this study, we irradiated Astragalus polysaccharides (APS) using 25 kGy ⁶⁰ Co γ ray to obtain γ-irradiated Astragalus polysaccharides (IAPS) and then investigated the effects of IAPS on growth performance and immune function of cyclophosphamide (CPM)-treated broilers. The physicochemical properties of APS and IAPS (molecular weight, water solubility, viscosity, morphological and structural properties) were evaluated. Then, 384 one-day-old Arbor Acres broiler chicks with similar initial weight were randomly assigned into 6 groups: the non-treated group (control), and CPM-treated groups were fed either a basal diet or the diets containing 900 mg/kg APS, or 900, 600, 300 mg/kg IAPS, respectively. On days 16, 18, and 20, all broilers except for the control group were intramuscularly injected with 0.5 ml CPM (40 mg/kg·BW). Broilers in the control group were intramuscularly injected with 0.5 ml sterilized saline (0.75%, wt/vol). This trial lasted for 21 days. The physicochemical treatment showed that γ irradiation could decrease the molecular weight and viscosity, and increase the water solubility of APS (p < 0.05), whereas the structural properties of APS was not affected. In the animal trial, 900 mg/kg APS or 900, 600 mg/kg IAPS relieved the decreased growth performance, thymus index, T lymphocytes proliferation, serum IgG concentration, NOS activity and the increased blood heterophil:lymphocyte ratio in CPM-treated broilers (p < 0.05). CPM-induced decreases in B lymphocytes proliferation and serum IgM concentration were only increased by IAPS at 900 mg/kg (p < 0.05). Overall, both APS and IAPS alleviated CPM-induced immunosuppression. Especially, IAPS possessed better immunomodulatory effect than APS, indicating that γ irradiation could be used as an effective method to enhance the immunomodulatory activity of APS.

Effects of Acute Cold Stress After Long-Term Cold Stimulation on Antioxidant Status, Heat Shock Proteins, Inflammation and Immune Cytokines in Broiler Heart

To investigate the effects of acute cold stress (ACS) on chicken heart after cold stimulation, female broilers were raised in either normal (C) or gradually decreasing temperatures (CS I and CS II) for 34 days followed by a 24 h ACS at 7°C. Cardiac tissues were collected from the pre-ACS and ACS time points to analyze the histopathological changes, antioxidant status and the expression of heat shock proteins, inflammatory factors and immune-related cytokines. The CS II heart tissues showed shrunken cell membranes and nuclei, disordered or ruptured myocardial fibers, higher MDA content and upregulation in HSP27, HSP40, HSP70, NF-κB, COX-2, PTGEs, iNOS, TNF-α and IL-4 mRNAs, and in protein levels of HSP40, NF-κB and iNOS and reduction in CAT, GSH-px and SOD activity, as well as HSP90 and IFN-γ levels compared to the control tissues before ACS. In contrast, the HSPs were significantly increased, and the inflammatory and immune related factors were unaltered prior to the ACS in the CS I compared to the C group. Following ACS, MDA content was significantly increased and antioxidant activity was significantly decreased in the CS I and CS II groups compared to the C group. The levels of HSP27, HSP70, HSP90, inflammatory factors and IL-4 were significantly reduced and that of IFN-γ was significantly increased in CS I broiler hearts; the reverse trends were seen in CS II relative to CS I. Compared to the pre-ACS levels, that of HSP27, HSP40, HSP60, inflammatory factors and IL-4 were increased and IFN-γ was decreased in the C and CS II groups after ACS. Therefore, cold stimulation at drastically lower temperatures induced cardiac damage, which was further aggravated by ACS. In contrast, cold stimulation at only 3°C lower than normal temperature improved the adaptability of the broilers to ACS.

Ameliorative effect of dietary supplementation of copper oxide nanoparticles on inflammatory and immune reponses in commercial broiler under normal and heat-stress housing conditions

Heat stress (HS) is one of the most serious adverse conditions that affect poultry causing immunosuppression and decreasing production. In a novel approach, we investigated effects of supplementing copper oxide nanoparticles (CuO-NPs) on the immune response in two commercial broiler strains (Ross 308 and Cobb 500). At one day old, birds were divided into 3 groups with 3 replicates for each. The first group received diet supplemented with 100% of their recommended copper requirements as CuO while, in the second and third groups, birds were given diets supplemented with 100% and 50% of the recommended Cu requirements in the form of CuO-NPs, respectively. At age of 21 day, each group was subdivided randomly into normal (24 ± 2 °C) and heat stressed (33 ± 2 °C for 5 h per day for two successive weeks) groups. Under normal housing temperature, CuO-NPs, significantly enhanced the immune response in these birds, compared to CuO shown by the increased levels of phagocytic activity (PA), lysozyme serum activity, and by upregulating immune-modulator genes including NF-κβ, PGES, IL-1β, TGF-1β, IFN-γ, BAX and CASP8. The responses were different between the two studied strains especially at the level of gene expression. In HS birds, supplementation of CuO-NPs reduced HS induced inflammatory conditions, as shown by lower gene expression levels, lower degenerative changes in the spleen, and altered heterophils/lymphocytes (H/L) ratio. We suggest CuO-NPs supplementation, especially in those chickens that received diet supplemented with 50% of their recommended Cu requirements, could be used under normal housing temperature to enhance the birds' immune response, and during HS to lower heat stress-induced degenerative changes depending on the magnitude of the HS.

The Controversy on Fish Pain: A Veterinarian's Perspective

Fish welfare is still a relatively new field. As such, regulations and protocols to ensure fish welfare are currently limited and vary considerably in different jurisdictions. This is in part because of the ongoing controversy as to whether or not fish feel pain. This controversy has persisted for several years, yet veterinarians have been mostly absent from the discussion so far. This essay aims to address this issue. Here, it is argued that while this controversy has its place, it is unlikely to be resolved in the near future. Fish welfare could instead be improved by pursuing more clinically applicable research to increase knowledge of fishes' behavior and physiology. Such research would assist in learning the optimal environment for their specific needs, as well as compiling some verified indicators of pain in fish. This would then lead to improved studies that could help to determine if and when analgesic drugs can be beneficial in fish, as they are in many other species.

Ginsenoside Rg1 enhanced immune responses to infectious bursal disease vaccine in chickens with oxidative stress induced by cyclophosphamide

This study was designed to evaluate the effect of oral administration of ginsenoside Rg1 on oxidative stress induced by cyclophosphamide in chickens. Ninety-six chickens were randomly divided into 4 groups, each consisting of 24 birds. Groups 2 and 3 received intramuscular injection of cyclophosphamide at 100 mg/kg body weight for 3 d to induce oxidative stress and immune suppression. Groups 1 and 4 were injected with saline in the same way as groups 2 and 3. Then chickens in group 3 were orally administrated Rg1 of 1 mg/kg body weight in drinking water for 7 d. After that, groups 1 to 3 were orally vaccinated with attenuated infectious bursal disease vaccine (Strain B87). Blood samples were collected for determination of infectious bursal disease virus-specific antibodies, cytokines, and oxidative parameters. Splenocytes were prepared for lymphocyte proliferation assay. The results showed that oral administration of ginsenoside Rg1 significantly enhanced specific antibody, IFN-γ, and IL-6 responses, and lymphocyte proliferation induced by concanavalin A and lipopolysaccharide in chickens injected with cyclophosphamide. Antioxidant activity of ginsenoside Rg1 was also observed in chickens by increased total antioxidant capacity, total superoxide dismutase, catalase, glutathione peroxidase, glutathione, ascorbic acid, and α-tocopherol, as well as decreased malondialdehyde and protein carbonyl. Therefore, oral administration of Rg1 was shown to improve the immune responses to infectious bursal disease vaccine in chickens suffering from oxidative stress.

Effect of Chromium Nanoparticles on Physiological Stress Induced by Exogenous Dexamethasone in Japanese Quails

Chromium (Cr), as an essential trace element, plays a critical role in carbohydrate, protein, and lipid metabolism in animals. It has been suggested that the beneficial effects of Cr increase by environmental stresses, which lead to greater Cr effects on stressed animals. The objective of the present study was to evaluate the response of physiologically stressed Japanese quails (Coturnix japonica) to dietary chromium nanoparticle (Nano-Cr) supplementation. The stress was induced by adding dexamethasone (0.6 mg/kg BW) to Japanese quails' diet from 17 to 22 days of age. A total of 360 birds were randomly allocated to six dietary treatments with four replicates each having 15 birds: negative control diet (no-stress, no-additive; NC), positive control diet (stress, no-additive; PC), and stress additive diets including four diets containing 200, 400, 800, and 1200 μg/kg of Nano-Cr. Performance and haematological parameters were affected (P < 0.05) by physiological stress though they were not affected by adding Nano-Cr. Comparison of diets containing Nano-Cr levels and stress no-additive diets, at 23 days of age, was indicative of a positive linear relationship (P < 0.05) between dietary Nano-Cr levels and feed intake and average daily gain. Furthermore, white blood cell (WBC) count as well as haematocrit level increased (P < 0.05) as the level of supplied Nano-Cr increased. A negative relationship (P < 0.05) was observed between Nano-Cr levels and heterophil percentage and heterophil/lymphocyte ratio. On day 35, increased dietary Nano-Cr improved (P < 0.05) weight gain, live body weight, energy/protein utilization efficiency, and WBC count. In conclusion, supplementation of diet with optimum concentration of Nano-Cr revealed alleviation of negative effects of physiological stress in quails.

Effects of dietary vitamin C, vitamin E, and alpha-lipoic acid supplementation on the antioxidant defense system and immune-related gene expression in broilers exposed to oxidative stress by dexamethasone

Vitamin C, vitamin E, and alpha-lipoic acid (ALA) are potent nutritional antioxidants, which are important for enhancing immunity. This study compared the effects of supplementation with vitamin C, vitamin E, or ALA on the antioxidant defense system and the expression of immune-related genes under oxidative stress induced by dexamethasone (DEX) in broilers. In total, 240 one-day-old female Recessive White Rock chickens were assigned randomly to either a basal diet (control group) or basal diet supplemented with vitamin C (200 mg/kg diet), vitamin E (100 mg/kg), or ALA (500 mg/kg) for 28 d starting from hatching. At 21 d of age, birds fed the ALA-supplemented diet had the highest plasma total antioxidant capacity (T-AOC) and superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-PX) enzyme activities, and the lowest plasma malondialdehyde (MDA) activity, as well as the lowest mRNA gene expression levels of interferon gamma (IFN-γ) and lipopolysaccharide-induced tumor necrosis factor-alpha factor (LITAF). At 23 d of age, the broilers in the 3 treatment groups were injected in the thigh muscle with DEX for 3 alternating days. In addition, the control group was divided into 2 equal groups, in which one was injected with saline and the other was injected with DEX. At 28 d of age, the DEX-ALA group (P < 0.05) had the highest activity levels for T-AOC, T-SOD, and GSH-PX in the plasma and liver (P < 0.05), and the greatest reduction in the MDA level. Dietary ALA significantly decreased the mRNA expression levels of the interleukin 1 β (IL-1β), IL-6, IFN-γ, and LITAF genes compared with the other groups during oxidative stress by DEX. In conclusion, this study suggests that in broilers, ALA is more effective for normalizing the oxidative stress induced by DEX than vitamin C or vitamin E.

Immunomodulatory effects of phytogenics in chickens and pigs - A review

Environmental stressors like pathogens and toxins may depress the animal immune system through invasion of the gastrointestinal tract (GIT) tract, where they may impair performance and production, as well as lead to increased mortality rates. Therefore, protection of the GIT tract and improving animal health are top priorities in animal production. Being natural-sourced materials, phytochemicals are potential feed additives possessing multiple functions, including: anti-inflammatory, anti-fungal, anti-viral and antioxidative properties. This paper focuses on immunity-related physiological parameters regulated by phytochemicals, such as carvacrol, cinnamaldehyde, curcumin, and thymol; many studies have proven that these phytochemicals can improve animal performance and production. On the molecular level, the impact of inflammatory gene expression on underlying mechanisms was also examined, as were the effects of environmental stimuli and phytochemicals in initiating nuclear factor kappa B and mitogen-activated protein kinases signaling pathways and improving health conditions.

Developmental corticosterone treatment does not program immune responses in zebra finches (Taeniopygia guttata)

Developmental conditions may impact the expression of immune traits throughout an individual's life. Early-life challenges may lead to immunological constraints that are mediated by endocrine-immune interactions. In particular, individual differences in the ability to mount immune responses may be programmed by exposure to stressors or glucocorticoid hormones during development. To test this hypothesis, we experimentally elevated levels of the glucocorticoid hormone corticosterone during the nestling and fledgling periods in captive zebra finches (Taeniopygia guttata). We subsequently challenged birds with the antigen lipopolysaccharide (LPS) on days 60 and 100 post-hatch to determine if developmental exposure to elevated corticosterone impacted the later response to LPS. As measures of immune function, we quantified bacteria killing ability, haptoglobin concentrations, and LPS-specific antibody responses at multiple time points. We also measured circulating corticosterone concentrations during the experimental period and on day 60 before and after endotoxin challenge. During the experimental period, corticosterone treatment elevated corticosterone levels. Corticosterone treatment did not induce programming effects on immune function or corticosterone production. Independent of treatment, individuals with higher corticosterone concentrations during the nestling period had lower bacteria killing ability on day 36 and higher baseline corticosterone concentrations on day 60 post-hatch. These results suggest a limited role for corticosterone exposure during early life to mediate immunological constraints later in life. Manipulation of cortisol may be necessary to conclusively determine if developmental glucocorticoid exposure can program immune function in birds. To determine if developmental stress can program the immune response, exposure to environmentally relevant stressors should also be manipulated.

Salmonella Enteritidis with double deletion in phoP fliC and a competitive exclusion culture elicit substantial additive protective effects against Salmonella exposure in newly hatched chicks

A live Salmonella Enteritidis vaccine (SE147N ΔphoP fliC), able to express both a homologous intestinal colonisation-inhibition effect and a systemic invasion-inhibition effect, was tested for its potential to generate a postulated additive protective effect in case of combined application with a competitive exclusion (CE) culture against Salmonella exposure in very young chicks. Both, SE147N ΔphoP fliC and the CE culture alone were highly protective against systemic and intestinal colonisation of the challenge strain in case of moderate Salmonella exposure, consequently, additive protective effects in combined use could not be detected. However, in case of high Salmonella Enteritidis challenge with 10⁶ cfu/bird at day 3 of life the combination of the ΔphoP fliC vaccine and the CE culture resulted in a protective effect much more pronounced than either of the single preparations and most substantial compared to untreated control birds. The term additive protective effects reflects the recognition that exclusion effects by gut flora cultures and inhibition effects by Salmonella vaccines are caused by different mechanisms.

The importance of propolis in alleviating the negative physiological effects of heat stress in quail chicks

Heat stress is one of the most detrimental confrontations in tropical and subtropical regions of the world, causing considerable economic losses in poultry production. Propolis, a resinous product of worker honeybees, possesses several biological activities that could be used to alleviate the deleterious effects of high environmental temperature on poultry production. The current study was aimed at evaluating the effects of propolis supplementation to Japanese quail (Coturnix coturnix japonica) diets on the production performance, intestinal histomorphology, relative physiological and immunological parameters, and selected gene expression under heat stress conditions. Three hundred one-day-old Japanese quail chicks were randomly distributed into 20 wired-cages. At 28 d of age, the birds were divided into 2 temperature treatment groups; a normal at 24°C (C group) and a heat stress at 35°C (HS group). The birds in each group were further assigned to 2 subgroups; one of them was fed on a basal diet without propolis supplementation (-Pr subgroup) while the other was supplemented with propolis (+Pr subgroup). Production performance including body weight gain, feed intake and feed conversion ratio were measured. The intestinal histomorphological measurements were also performed for all treatment groups. Relative physiological parameters including body temperature, corticosterone hormone level, malondialdehyde (MDA) and free triiodothyronine hormone (fT3), as well as the relative immunological parameters including the total white blood cells count (TWBC’s), heterophil/lymphocyte (H/L) ratio and lymphocyte proliferation index, were also measured. Furthermore, the mRNA expression for toll like receptor 5 (TLR5), cysteine-aspartic protease-6 (CASP6) and heat shock proteins 70 and 90 (Hsp70 and Hsp90) genes was quantified in this study. The quail production performance was significantly (P<0.05) impaired by HS treatment, while Pr treatment significantly improved the quail production performance. The villus width and area were significantly (P<0.05) lower in the HS compared to the C group, while Pr treatment significantly increased crypts depth of quail. A negative impact of HS treatment was observed on the physiological status of quail; however, propolis significantly alleviated this negative effect. Moreover, quail of the HS group expressed lower immunological parameters than C group, while propolis enhanced the immune status of the quail. The relative mRNA expression of TLR5 gene was down-regulated by HS treatment while it was up-regulated by the Pr treatment. Furthermore, the positive effects of propolis in HS-quail were evidenced by normalizing the high expressions of CASP6 and Hsp70 genes when compared to the C group. Based on these results, the addition of propolis to quail diets as a potential nutritional strategy in order to improve their performance, especially under heat stress conditions, is recommended.

Transcriptional profile of breast muscle in heat stressed layers is similar to that of broiler chickens at control temperature

BACKGROUND

In recent years, the commercial importance of changes in muscle function of broiler chickens and of the corresponding effects on meat quality has increased. Furthermore, broilers are more sensitive to heat stress during transport and at high ambient temperatures than smaller egg-laying chickens. We hypothesised that heat stress would amplify muscle damage and expression of genes that are involved in such changes and, thus, lead to the identification of pathways and networks associated with broiler muscle and meat quality traits. Broiler and layer chickens were exposed to control or high ambient temperatures to characterise differences in gene expression between the two genotypes and the two environments.

RESULTS

Whole-genome expression studies in breast muscles of broiler and layer chickens were conducted before and after heat stress; 2213 differentially-expressed genes were detected based on a significant (P < 0.05) genotype × treatment interaction. This gene set was analysed with the BioLayout Express^3D and Ingenuity Pathway Analysis software and relevant biological pathways and networks were identified. Genes involved in functions related to inflammatory reactions, cell death, oxidative stress and tissue damage were upregulated in control broilers compared with control and heat-stressed layers. Expression of these genes was further increased in heat-stressed broilers.

CONCLUSIONS

Differences in gene expression between broiler and layer chickens under control and heat stress conditions suggest that damage of breast muscles in broilers at normal ambient temperatures is similar to that in heat-stressed layers and is amplified when broilers are exposed to heat stress. The patterns of gene expression of the two genotypes under heat stress were almost the polar opposite of each other, which is consistent with the conclusion that broiler chickens were not able to cope with heat stress by dissipating their body heat. The differentially expressed gene networks and pathways were consistent with the pathological changes that are observed in the breast muscle of heat-stressed broilers.

Depression of leukocyte protein synthesis, immune function and growth performance induced by high environmental temperature in broiler chickens

In tropical and semitropical regions, raising broiler chickens out of their thermal comfort zone can cause an added economic loss in the poultry industry. The cause for the deleterious effects on immunity and growth performance of broilers under high environmental temperatures is still poorly understood. Therefore, the aim of the current investigation was to evaluate the effect of heat stress on leukocytes protein synthesis and immune function as a possible direct cause of low performance in broiler chickens under such condition. In this study, 300 one-day-old male broiler chicks (Cobb500™) were randomly assigned into 2 groups with 5 replicates of 30 chicks each. From 21 to 42 days of age, one group was exposed to non-stressed condition at 24 °C and 50% relative humidity (control group), while the other group was exposed to heat stress at 35 °C and 50% relative humidity (HS group). At 42 days of age, blood samples were collected from each group to evaluate stress indicators, immune function, and leukocytes protein synthesis. Production performance was also recorded. Noteworthy, protein synthesis in leukocytes was significantly (P < 0.05) inhibited in HS group by 38% compared to control group. In contrast, the phosphorylation level on threonine 56 site (Thr⁵⁶) of eukaryotic elongation factor (eEF2), which indicates the suppression of protein translation process through altering the protein elongation phase, was significantly threefold higher in HS group than in control (P < 0.05). In addition, an increase in stress indicators was markedly (P < 0.05) presented in the HS birds by twofold increase in heterophil/lymphocyte (H/L) ratio and threefold increase in plasma corticosterone level compared to control. Furthermore, the immune function was significantly (P < 0.05) suppressed in HS birds than control (0.99 vs. 1.88 mg/mL plasma IgG, 89.2 vs. 148.0 μg/mL plasma IgM, 4.80 vs. 7.20 antibody titer against SRBC, and 1.38 vs. 3.39 stimulation index of lymphocyte proliferation in HS vs. control group, respectively). Moreover, results on the broiler performance indicate that HS birds had a significant (P < 0.05) lower body weight gain by 58%, lower feed consumption by 39%, higher conversion ratio by 27%, and higher mortality by more than three times, compared to control birds. In conclusion, our results demonstrate that the inhibition of leukocyte protein synthesis through increasing the level of eEF2 Thr⁵⁶ phosphorylation may play a key role in the observed decrease in immune function and growth performance with the high mortality rate encountered in broiler chickens under heat stress environment.

Stress Induced Polarization of Immune-Neuroendocrine Phenotypes in Gallus gallus

Immune-neuroendocrine phenotypes (INPs) stand for population subgroups differing in immune-neuroendocrine interactions. While mammalian INPs have been characterized thoroughly in rats and humans, avian INPs were only recently described in Coturnix coturnix (quail). To assess the scope of this biological phenomenon, herein we characterized INPs in Gallus gallus (a domestic hen strain submitted to a very long history of strong selective breeding pressure) and evaluated whether a social chronic stress challenge modulates the individuals' interplay affecting the INP subsets and distribution. Evaluating plasmatic basal corticosterone, interferon-γ and interleukin-4 concentrations, innate/acquired leukocyte ratio, PHA-P skin-swelling and induced antibody responses, two opposite INP profiles were found: LEWIS-like (15% of the population) and FISCHER-like (16%) hens. After chronic stress, an increment of about 12% in each polarized INP frequency was found at expenses of a reduction in the number of birds with intermediate responses. Results show that polarized INPs are also a phenomenon occurring in hens. The observed inter-individual variation suggest that, even after a considerable selection process, the population is still well prepared to deal with a variety of immune-neuroendocrine challenges. Stress promoted disruptive effects, leading to a more balanced INPs distribution, which represents a new substrate for challenging situations.

Comprehensive growth performance, immune function, plasma biochemistry, gene expressions and cell death morphology responses to a daily corticosterone injection course in broiler chickens

The massive meat production of broiler chickens make them continuously exposed to potential stressors that stimulate releasing of stress-related hormones like corticosterone (CORT) which is responsible for specific pathways in biological mechanisms and physiological activities. Therefore, this research was conducted to evaluate a wide range of responses related to broiler performance, immune function, plasma biochemistry, related gene expressions and cell death morphology during and after a 7-day course of CORT injection. A total number of 200 one-day-old commercial Cobb broiler chicks were used in this study. From 21 to 28 d of age, broilers were randomly assigned to one of 2 groups with 5 replicates of 20 birds each; the first group received a daily intramuscular injection of 5 mg/kg BW corticosterone dissolved in 0.5 ml ethanol:saline solution (CORT group), while the second group received a daily intramuscular injection of 0.5 ml ethanol:saline only (CONT group). Growth performance, including body weight (BW), daily weight gain (DG), feed intake (FI) and feed conversion ratio (FC), were calculated at 0, 3 and 7 d after the start of the CORT injections. At the same times, blood samples were collected in each group for hematological (TWBC's and H/L ratio), T- and B-lymphocytes proliferation and plasma biochemical assays (total protein, TP; free triiodothyronine hormone, fT3; aspartate amino transaminase, AST; and alanine amino transaminase, ALT). The liver, thymus, bursa of Fabricius and spleen were dissected and weighed, and the mRNA expression of insulin-like growth factor 1 gene (IGF-1) in liver and cell-death-program gene (caspase-9) in bursa were analyzed for each group and time; while the apoptotic/necrotic cells were morphologically detected in the spleen. From 28 to 35 d of age, broilers were kept for recovery period without CORT injection and the same sampling and parameters were repeated at the end (at 14 d after initiation of the CORT injection). In general, all parameters of broiler performance were negatively affected by the CORT injection. In addition, CORT treatment decreased the plasma concentration of fT3 and the mRNA expression of hepatic IGF-1. A significant increase in liver weight accompanied by an increase in plasma TP, AST and ALT was observed with CORT treatment, indicating an incidence of liver malfunction by CORT. Moreover, the relative weights of thymus, bursa and spleen decreased by the CORT treatment with low counts of TWBC's and low stimulation of T & B cells while the H/L ratio increased; indicating immunosuppressive effect for CORT treatment. Furthermore, high expression of caspase-9 gene occurred in the bursa of CORT-treated chickens, however, it was associated with a high necrotic vs. low apoptotic cell death pathway in the spleen. Seven days after termination of the CORT treatment in broilers, most of these aspects remained negatively affected by CORT and did not recover to its normal status. The current study provides a comprehensive view of different physiological modulations in broiler chickens by CORT treatment and may set the potential means to mount a successful defense against stress in broilers and other animals as well.

Correlating bacterial shedding with fecal corticosterone levels and serological responses from layer hens experimentally infected with Salmonella Typhimurium

Salmonella Enteriditis and Salmonella Typhimurium are commonly isolated during egg-related outbreaks of salmonellosis and represent a significant international public health issue. In Australia, Salmonella Typhimurium is the most common serovar identified in egg product related foodborne outbreaks. While a number of studies have investigated Salmonella shedding and host responses to infection, they have been conducted over a short time period. The present study sought to characterise bacterial shedding and host responses to infection in hens infected with only Salmonella Typhimurium or co-infected with both Salmonella Typhimurium and Salmonella Mbandaka over a 16 week period. Salmonella shedding was quantified using the most probable number and qPCR methods and was highly variable over the course of the experiment. On day 1, fecal corticosterone metabolites in birds infected with Salmonella Typhimurium (674.2 ± 109.3 pg/mg) were significantly higher than control (238.0 ± 12.62 pg/mg) or co-infected (175.4 ± 8.58 pg/mg) birds. The onset of lay occurred between weeks 6–8 post-infection (pi) and Fecal corticosterone metabolite (FCM) concentrations increased in both control and co-infected birds. Antibody responses to infection were monitored in both serum and yolk samples. Salmonella Typhimurium specific antibody was lower in co-infected animals than monoinfected animals. Bacterial loads in internal organs were characterised to determine persistence. Spleen, liver and caecal tonsils were positive for bacteria in both groups, indicating that Salmonella was not cleared from the birds and internal organ colonization could serve as a reservoir for continued bacterial shedding.

Avian biological clock - Immune system relationship

Biological rhythms in birds are driven by the master clock, which includes the suprachiasmatic nucleus, the pineal gland and the retina. Light/dark cycles are the cues that synchronize the rhythmic changes in physiological processes, including immunity. This review summarizes our investigations on the bidirectional relationships between the chicken pineal gland and the immune system. We demonstrated that, in the chicken, the main pineal hormone, melatonin, regulates innate immunity, maintains the rhythmicity of immune reactions and is involved in the seasonal changes in immunity. Using thioglycollate-induced peritonitis as a model, we showed that the activated immune system regulates the pineal gland by inhibition of melatonin production at the level of the key enzyme in its biosynthetic pathway, arylalkylamine-N-acetyltransferase (AANAT). Interleukin 6 and interleukin 18 seem to be the immune mediators influencing the pineal gland, directly inhibiting Aanat gene transcription and modulating expression of the clock genes Bmal1 and Per3, which in turn regulate Aanat.