Impact of Housing Environment on the Immune System in Chickens: A Review

Prolonged exposure to a music-enriched environment mitigates acute noise-induced inflammation and apoptosis in the chicken spleen by modulating the Keap-1/Nrf2 and NF-κB pathways

The rise of operational noise as an environmental pollutant for farm animals is an emerging concern. The mechanisms through which music can alleviate oxidative stress, inflammation, and apoptosis induced by noise exposure remain underexplored. This study aims to investigate the alleviating effects and underlying mechanisms of long-term music exposure on noise-induced damage to the chicken spleen. Male Arbor Acres (AA) broilers were divided into four groups: control (C), acute noise stimulation (NS), noise stimulation with music mitigation (NSM), and music only (M). NS and NSM groups were exposed to noise (simulating sudden intensity noise, 115 to 120dB) for 10 minutes daily for a week, starting at 14-days-old. NSM and M groups then received 28 days of 6-hour daily music (Mozart K.448, 60-65 dB). The results showed that noise stimulation significantly activated the Keap-1/Nrf2 and NF-κB signaling pathways. Long-term music intervention has also been demonstrated to successfully mitigate oxidative stress and abnormal apoptosis induced by acute noise stimulation. Microscopic examination of the spleen revealed that acute noise stimulation resulted in an increase in splenic cells, a decrease in lymphocytes, and blurred boundaries between the red and white pulps in the NS group. However, these pathological changes were alleviated in the NSM group following music intervention. Compared with the control group, the NS group exhibited significantly elevated oxidative stress parameters. In contrast, music intervention in the NSM group notably improved antioxidant capacity and partially alleviated morphological abnormalities in the spleen. Additionally, noise stimulation activated the NF-κB pathway, upregulating the downstream genes of the inflammatory factors IL-1β, IL-6, and TNF-α. Noise-induced mitochondrial damage led to apoptosis, as observed by TUNEL staining, along with increased gene and protein expression of Bcl-2, Bax, Cyt-C, Casp-3, Casp-8, and Casp-9. These findings indicate that acute noise exposure can induce splenic damage via oxidative stress, inflammation, and apoptosis by modulating the Keap-1/Nrf2 and NF-κB pathways. Prolonged music stimulation effectively mitigates noise-induced damage, offering a vital experimental foundation for further research on noise pollution's impact on organisms and music's alleviating role.

Effects of different housing systems on the oxidative defence system, heterophil functions, cellular immune response and cytokines in laying hens

1. This study investigated the effects of different housing systems on oxidative defence mechanisms, heterophil functions, cellular immune response and cytokine production in laying hens. One hundred and twenty laying hens were allocated into one of four groups: conventional cages, furnished cages, deep litter, and free range.2. Housing system did not affect malondialdehyde concentrations and enzymatic antioxidant status. Ascorbic acid values were higher in deep-litter hens than in those in conventional cages and free range.3. Phagocytic and chemotactic activities tended to rise in the deep-litter system, and oxidative burst was higher than in furnished cages. Cytotoxic T cells were decreased in furnished cages, both cytotoxic and helper T cells decreased in deep litter compared to free range.4. The IL-2 and IL-13 expression was higher in deep litter than in conventional cages, and IL-6 expression was higher in furnished cages than in free range.5. Housing system had no significant effects on the oxidative defence system; however, they affected heterophil functions, cellular defence mechanisms and cytokine production. The results suggested that breeders need to consider the housing system's potential effects on immune defence responses while applying a breeding strategy appropriate for animal welfare and consumer demand.

Cytokine and immunoglobulin profiles of Arbor Acres broiler chickens at different stages of physiological development

Background and Aim

Modern scientific research focuses on a detailed study of the immune system, the mechanisms of immunosuppression, and the search for an effective means to restore disturbed immune homeostasis in farm animals. The present study examined the cytokine and immunoglobulin (Ig) profiles of healthy broiler chickens during physiological development.

Materials and Methods

Arbor Acres broilers (n = 28) were used in the study to achieve this objective. The immune status of broiler chickens was assessed on 7, 14, 28, and 42 days of age, including serum levels of cytokines, Igs, and lysozyme by enzyme immunoassay.

Results

We observed a decrease in the efficiency of immune system functioning of birds with increasing age. The most pronounced immunological deficiency in the body of broiler chickens is noted at the age of 7-14 days, which is associated with immaturity of the immune system and is characterized by the fact that non-specific humoral and specific cellular defense factors are at a rather low level. The levels of lysozyme, interleukin (IL)-2, IL-10, and IgA in blood serum at this age were minimal; starting from 28 days of age, there is a specific humoral immune deficiency, which is compensated by strengthening of cellular defense factors. The serum level of IgY intensively decreases against the background of an increase of lysozyme, IL-2, IL-4, and IL-10.

Conclusion

During postnatal ontogenesis, the immune system of broiler chickens undergoes dynamic changes that have an age direction and phase character. Changes in the immune system may affect immunocompetence, disease susceptibility, and, consequently, productivity.

Impacts of longitudinal water curtain cooling system on transcriptome-related immunity in ducks

BACKGROUND

The closed poultry houses integrated with a longitudinal water curtain cooling system (LWCCS) are widely used in modern poultry production. This study showed the variations in environmental conditions in closed houses integrated with a longitudinal water curtain cooling system. We evaluated the influence of different environmental conditions on duck growth performance and the transcriptome changes of immune organs, including the bursa of Fabricius and the spleen.

RESULT

This study investigated the slaughter indicators and immune organ transcriptomes of 52-day-old Cherry Valley ducks by analyzing the LWCC at different locations (water curtain end, middle position, and fan cooling end). The results showed that the cooling effect of the LWCCS was more evident from 10:00 a.m. -14:00. And from the water curtain end to the fan cooling end, the hourly average temperature differently decreased by 0.310℃, 0.450℃, 0.480℃, 0.520℃, and 0.410℃, respectively (P < 0.05). The daily and hourly average relative humidity decreased from the water curtain end to the fan cooling end, dropping by 7.500% and 8.200%, respectively (P < 0.01). We also observed differences in production performance, such as dressing weight, half-eviscerated weight, skin fat rate, and percentage of abdominal fat (P < 0.01), which may have been caused by environmental conditions. RNA-sequencing (RNA-seq) revealed 211 and 279 differentially expressed genes (DEGs) in the ducks' bursa of Fabricius and spleen compared between the water curtain end and fan cooling end, respectively. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of the two organs showed the DEGs were mainly enriched in cytokine-cytokine receptor interaction, integral component of membrane, Retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) signaling pathway, etc. Our results implied that full-closed poultry houses integrated with LWCCS could potentially alter micro-environments (water curtain vs. fan cooling), resulting in ducks experiencing various stressful situations that eventually affect their immunity and production performance.

CONCLUSION

In this study, our results indicated that uneven distributions of longitudinal environmental factors caused by LWCCS would affect the dressed weight, breast muscle weight, skin fat rate, and other product performance. Moreover, the expression of immune-related genes in the spleen and bursa of ducks could be affected by the LWCCS. This provides a new reference to optimize the use of LWCCS in conjunction with close duck houses in practical production.

Adoption of veterinary vaccines, determining factors, and barriers in Southwest Ethiopia: Implications for livestock health and disease management strategies

In Ethiopia, the use of veterinary vaccines to control animal diseases is an effective strategy. A study conducted in Southwest Ethiopia from October 2020 to October 2021 aimed to determine the adoption level of veterinary vaccines and factors affecting their use. The study used multistage random sampling to select districts and interviewed 476 farmers who had either adopted or not adopted the vaccines. The study found that certain diseases should be prioritized for vaccination to safeguard the health of cattle, sheep, goats, and poultry. These include anthrax (19.12 %), blackleg (17.65 %), foot and mouth disease (10.50 %), and lumpy skin disease (8.82 %) in cattle, and pasteurellosis (18.07 %), contagious caprine pleuropneumonia (15.97 %), peste des petits ruminants (14.15 %), and Orf (13.45 %) in sheep and goats. Newcastle disease (21.85 %), infectious bursal disease (19.33 %), and coccidiosis (17.02 %) were identified as high-priority diseases for flock health. Overall, 30.7 % of farmers were adopters of veterinary vaccines, while 69.3 % were non-adopters. The study identified several factors that influence the likelihood of adopting veterinary vaccines, including breed type (OR = 9.1, p < 0.0001), production size (OR = 9.7, p < 0.0001), production type (OR = 2.7, p < 0.0001), and farm location (OR = 9.8, p = 0.001). Common barriers to vaccination included a lack of disease knowledge, high vaccine costs, limited vaccine availability, and administration difficulties. Insights from the study can guide strategies for promoting veterinary vaccine adoption in Ethiopia. Stakeholders should pay attention to these findings since vaccine use is crucial for controlling animal diseases, enhancing animal health, and preventing economic losses. Further research is needed to investigate factors affecting enhanced veterinary vaccine adoption.

Review: The role of heat shock proteins in chicken: Insights into stress adaptation and health

This review article aimed to provide readers with a comprehensive understanding of the function of heat shock proteins (HSPs) in chicken physiology, stress response, and overall poultry health. With the increasing challenges faced by the livestock industry, particularly the poultry sector, due to climate change-induced high ambient temperatures, heat stress (HS) has become a critical concern. HS disrupts the thermal balance in poultry, leading to detrimental effects on growth, immune function, and overall health. HSPs play a pivotal role in mitigating the impacts of HS in chickens. These molecular chaperones are involved in protein folding, unfolding, and assembly, and they are classified into several families based on their size, including small molecule HSPs, HSP40, HSP60, HSP70, HSP90, and HSP110. By maintaining cellular homeostasis and promoting stress tolerance, HSPs act as vital guardians in helping chickens cope with HS and its associated consequences. The review synthesized relevant literature to shed light on the importance of HSPs in stress adaptation, cellular homeostasis, and the maintenance of normal cell metabolism in chickens. The adverse effects of HS on chickens include oxidative stress and compromised immune systems, making them more susceptible to infections. So also, HS negatively affects production performance and meat quality in poultry. Understanding the functions of HSPs in chickens offers valuable insights into stress adaptation and health, and could potentially lead to the identification of HSP biomarkers, genetic selection for heat tolerance, investigations into the interplay between HSPs and immune function, and the development of nutritional interventions to enhance HSP activity. By exploring these potential research directions, the review aimed to contribute to the development of novel approaches to mitigate the negative effects of HS on poultry, ultimately improving productivity and animal welfare in a changing climate.

Comparison of Infectious Bronchitis Virus (IBV) Pathogenesis and Host Responses in Young Male and Female Chickens

Infectious bronchitis virus (IBV) is an avian coronavirus that causes a disease in chickens known as infectious bronchitis (IB). The pathogenesis of IBV and the host immune responses against it depend on multiple factors such as the IBV variant, breed and age of the chicken, and the environment provided by the management. Since there is limited knowledge about the influence of the sex of chickens in the pathogenesis of IBV, in this study we aim to compare IBV pathogenesis and host immune responses in young male and female chickens. One-week-old specific pathogen-free (SPF) White Leghorn male and female chickens were infected with Canadian Delmarva (DMV)/1639 IBV variant at a dose of 1 × 106 embryo infectious dose (EID)50 by the oculo-nasal route while maintaining uninfected controls, and these chickens were euthanized and sampled 4- and 11-days post-infection (dpi). No significant difference was observed between the infected male and female chickens in IBV shedding, IBV genome load in the trachea, lung, kidney, bursa of Fabricius (BF), thymus, spleen, and cecal tonsils (CT), and IBV-induced lesion in all the examined tissues at both 4 and 11 dpi. In addition, there was no significant difference in the percentage of IBV immune-positive area observed between the infected male and female chickens in all tissues except for the kidney, which expressed an increased level of IBV antigen in infected males compared with females at both 4 and 11 dpi. The percentage of B lymphocytes was not significantly different between infected male and female chickens in all the examined tissues. The percentage of CD8+ T cells was not significantly different between infected male and female chickens in all the examined tissues except in the trachea at 11 dpi, where female chickens had higher recruitment when compared with male chickens. Overall, although most of the findings of this study suggest that the sex of chickens does not play a significant role in the pathogenesis of IBV and the host immune response in young chickens, marginal differences in viral replication and host responses could be observed to indicate that IBV-induced infection in male chickens is more severe.

Haematological parameters of laying hens under different group size

The relevance of this study lies in its potential implications for poultry farming practices and animal welfare. Understanding the impact of group size on the blood parameters of hens can provide valuable insights for optimising their health and well-being in farming environments. The aim of the study was an analysis of haematological parameters of laying hens under the influence group size with the same stoking density in analogous cages by design. Hens were kept for 34 weeks in cages of multilevel batteries at different group sizes: I group-93 birds, II group-52 birds, III group-17 birds and IV group-9 birds. The study analysed blood samples from laying hens at 18 and 52 weeks of age. Results showed that reducing the group size from 93 to 52 birds led to a haematological status within the physiological norm, characterized by increased heterophils and decreased monocyte levels. Whereas, the decrease in group size to 17 birds was accompanied by a decrease in the hens' blood content of thrombocytes, an increase of heterophile, a decrease of monocytes and lymphocytes within the physiological norm, as well as an increase in the heterophiles to lymphocytes ratio.

A Preliminary Investigation of Salmonella Populations in Indigenous Portuguese Layer Hen Breeds

The sustainability of agroecological systems, biodiversity protection, animal welfare, and consumer demand for higher quality products from alternative and extensive farming methods have reinforced interest in local breeds that are well adapted to low-input environments. However, food safety needs to be safeguarded to reinforce consumer confidence. The aim of this study was to conduct a preliminary investigation on the occurrence of Salmonella spp. in eggshells, hen's cloaca, and litter materials from autochthonous Portuguese laying hens raised in a semi-extensive system for small-scale production. A total of 279 samples from 31 flocks belonging to 12 farms were obtained, with 63 samples from the "Preta Lusitânica" breed, and 72 samples each from the remaining autochthonous breeds, namely, "Branca", "Amarela", and "Pedrês Portuguesa". None (0%) of the samples analyzed were positive for Salmonella spp. To the best of our knowledge, these are the first results of Salmonella evaluation from hen's cloaca, eggshells, and litter materials in autochthonous Portuguese chickens, suggesting that a semi-extensive production system can contribute to better food security and a lower risk to public health and the environment.

Morphological and molecular characteristics of Plasmodium juxtanucleare in layer chicken from three districts of Yogyakarta, Indonesia

Background and Aim

Blood parasite infections in poultry, such as Plasmodium, are a serious threat to the poultry industry due to their potential to cause economic losses. To date, there has been inadequate research on the morphological and molecular detection of the different Plasmodium species that infect poultry in Indonesia. Therefore, this study aimed to analyze the morphological and molecular characteristics of Plasmodium spp. and the several predisposing factors for Plasmodium infection in layer chickens from three districts of Yogyakarta, Indonesia.

Materials and Methods

One hundred and five blood samples from layer chickens were collected from 13 farms located in three districts of Yogyakarta (Sleman, Bantul, and Kulon Progo) between September and November 2022. Blood samples were subjected to microscopic and polymerase chain reaction (PCR) analyses. Sequencing was performed using basic local alignment search tools to identify the nucleotide structure of cytochrome b. Phylogenetic analysis of Plasmodium was performed using the MEGA-X software.

Results

Microscopic examination revealed that 17/105 positives (16.19%) were positive for blood parasite infection. Trophozoites, erythrocytic meronts, and microgametocytes of Plasmodium were found in blood samples. Based on the morphological examination, the species found in the samples was close to Plasmodium juxtanucleare. Polymerase chain reaction examination revealed that 21/60 samples were positive for Plasmodium (35%). The Plasmodium species identified from the sequenced samples were proven to be P. juxtanucleare. The P. juxtanucleare from Thailand was closely related to samples (99.64%-100%) with a genetic distance of 0%-1%. In addition, age, population, and cage type were not significantly associated with Plasmodium infection.

Conclusion

Based on microscopic and PCR examinations, the Plasmodium species found in the three districts of Yogyakarta was P. juxtanucleare. The genetic distance between samples from the three districts of Yogyakarta was closely related (0%-1%) to P. juxtanucleare from Thailand and Japan. There was no correlation between Plasmodium infection and age, cage type, or population.

Resistant Bacteria in Broiler Litter Used as Ruminant Feed: Effect of Biotic Treatment

The use of antimicrobial drugs and coccidiostats in poultry farming is widespread, with a significant proportion of these drugs being excreted and released into the environment. The residues of such drugs in poultry litter (PL) can result in the development of antibiotic-resistant bacteria. The impact of different biotic treatments (aerobic, anaerobic, and stacking) on broiler litter (BL) before its use as animal feed has not been studied extensively, nor have the differences between antimicrobial-dependent and independent broiler farms been investigated. This study aimed to determine the resistant bacteria in BL used as ruminant feed before and after litter treatment. The results show that the most resistant bacteria before BL treatment were the Enterococcus species. This study also found that the quantity of amoxicillin-resistant Enterococcus detected in samples from antimicrobial-dependent farms was significantly higher than in those from antimicrobial-independent farms. Additionally, 14% of bacteria were multi-resistant to tetracycline, sulfafurazole, and erythromycin in antimicrobial-independent farm litters, significantly lower than those measured in antimicrobial-dependent broiler farm litter. This study highlights the importance of better understanding, regulating, managing, and using animal waste appropriately to reduce the number of antibiotic-resistant bacteria and minimize the use of antimicrobials that carry high risks for animals, humans, and the environment.

Effect of Melatonin on the Content of CD3low and CD3hi T Cells in the Thymus of Mice with Functional Pinealectomy

Continuous lighting for 14 days (functional pinealectomy model) leads to a decrease in the relative number of CD3^low and CD3^hi T lymphocytes and the CD3^low/CD3^hi ratio in the thymus of C57BL/6 mice. Intragastric administration of melatonin in physiological doses (1 mg/kg body weight, 14 days) against the background of functional pinealectomy restores the percentage of CD3^low and CD3^hi thymocytes and CD3^low/CD3^hi ratio to the control values. Hence, prolonged continuous illumination inhibits the differentiation and maturation of young thymocytes into mature forms, while melatonin treatment helps to compensate the effects of functional pinealectomy triggering cell proliferation in the thymus from the earliest stages of proliferation and differentiation of T cells. Thus, melatonin has immunotropic properties and can be used for correction of the consequences of functional pinealectomy.

Influence of water quality and pollution on broiler's performance, vaccine and antibiotic efficiencies

Good water quality for livestock is critical for preserving animal health, ensuring the quality of animal products, supplying safe food, and increasing food production economics. Higher water levels of toxic compounds than permitted can impair meat, fat, eggs, and milk production, lower fertility, and represent public health hazards. Water picks up pollutants from its surroundings and those caused by animal and human activities. Many physicochemical parameters were used to ensure water quality, including pH, salt, taste, color, alkalinity, odor, and hardness. Water quality, directly and indirectly, impacts livestock performance and, thus, the poultry industry. Employing drinking water as a carrier of drugs still faces substantial barriers. The effectiveness of vaccinations and drugs is affected by inadequate water quality. Furthermore, contaminated water and poor nutrition negatively affect broiler chicken immunity, survival, and production. Antibiotics are widely utilized in poultry production to preserve animal health and growth. They can eliminate harmful bacteria in the gut, reduce the load on the immune system, optimize the digestive system, and boost growth performance. However, the abuse of antibiotics in animal agriculture has resulted in antibiotic-resistant infections threatening people and animals. As a result of its positive impact on the metabolome and gut microbiome, the natural antimicrobial combination could be used as an alternative; improving broiler chicken growth performance without negatively affecting the environment is currently paramount.

Levels of Circulating IgM and IgY Natural Antibodies in Broiler Chicks: Association with Genotype and Farming Systems

Naturally occurring antibodies (NAbs), which are major components of innate immunity, exist in circulation under healthy conditions without prior antigenic stimulation and are able to recognize both self- and non-self-constituents. The present study aimed at identifying potential immunological differences between commercial fast- and slow-growth broilers (n = 555) raised in conventional and free-range systems, respectively, through the use of the specificity, isotypes and levels of circulating NAbs. The possible beneficial effect of oregano-based dietary supplementation was also evaluated. To this end, serum IgM and IgY NAbs against self- (actin and DNA) and non-self- antigens (trinitrophenol and lipopolysaccharide) were measured by ELISA and further correlated with genotype, season and performance. Significantly higher levels of IgM NAbs against all antigens were found in slow-growth compared to fast-growth broilers. IgM NAb levels were also significantly increased in dietarily supplemented slow-growth broilers versus those consuming standard feed. Moreover, significantly elevated levels of anti-DNA IgY NAbs were found in fast-growth compared to slow-growth broilers, whereas the opposite was observed for anti-LPS IgY NAbs. Multivariate linear regression analysis confirmed multiple interactions between NAb levels, genotype, season and performance. Overall, serum NAbs have proven to be valuable innovative immunotools in the poultry industry, efficiently differentiating fast-growing versus slow-growing broilers, and dietary supplementation of plant extracts can enhance natural immunity.

Research progress on the mechanisms underlying poultry immune regulation by plant polysaccharides

With the rapid development of poultry industry and the highly intensive production management, there are an increasing number of stress factors in poultry production. Excessive stress will affect their growth and development, immune function, and induce immunosuppression, susceptibility to a variety of diseases, and even death. In recent years, increasing interest has focused on natural components extracted from plants, among which plant polysaccharides have been highlighted because of their various biological activities. Plant polysaccharides are natural immunomodulators that can promote the growth of immune organs, activate immune cells and the complement system, and release cytokines. As a green feed additive, plant polysaccharides can not only relieve stress and enhance the immunity and disease resistance of poultry, but also regulate the balance of intestinal microorganisms and effectively alleviate all kinds of stress faced by poultry. This paper reviews the immunomodulatory effects and molecular mechanisms of different plant polysaccharides (Atractylodes macrocephala Koidz polysaccharide, Astragalus polysaccharides, Taishan Pinus massoniana pollen polysaccharide, and alfalfa polysaccharide) in poultry. Current research results reveal that plant polysaccharides have potential uses as therapeutic agents for poultry immune abnormalities and related diseases.

Bacterial Community Characteristics Shaped by Artificial Environmental PM2.5 Control in Intensive Broiler Houses

Multilayer cage-houses for broiler rearing have been widely used in intensive Chinese farming in the last decade. This study investigated the characteristics and influencing factors of bacterial communities in the PM2.5 of broiler cage-houses. The PM2.5 samples and environmental variables were collected inside and outside of three parallel broiler houses at the early, middle, and late rearing stages; broiler manure was also gathered simultaneously. The bacterial 16S rRNA sequencing results indicated that indoor bacterial communities were different from the outdoor atmosphere and manure. Furthermore, the variations in airborne bacterial composition and structure were highly influenced by the environmental control variables at different growth stages. The db-RDA results showed that temperature and wind speed, which were artificially modified according to managing the needs for broiler growth, were the main factors affecting the diversity of dominant taxa. Indoor airborne and manurial samples shared numerous common genera, which contained high abundances of manure-origin bacteria. Additionally, the airborne bacterial community tended to stabilize in the middle and late stages, but the population of potentially pathogenic bacteria grew gradually. Overall, this study enhances the understanding of airborne bacteria variations and highlighted the potential role of environmental control measures in intensive farming.

m6A-Mediated PPARA Translational Suppression Contributes to Corticosterone-Induced Visceral Fat Deposition in Chickens

Excess fat deposition in broilers leads to great economic losses and is harmful to consumers' health. Chronic stress in the life cycle of chickens could be an important trigger. However, the underlying mechanisms are still unclear. In this study, 30-day-old chickens were subcutaneously injected with 2 mg/kg corticosterone (CORT) twice a day for 14 days to simulate long-term stress. It was shown that chronic CORT exposure significantly increased plasma triglyceride concentrations and enlarged the adipocyte sizes in chickens. Meanwhile, chronic CORT administration significantly enlarged the adipocyte sizes, increased the protein contents of FASN and decreased HSL, ATGL, Beclin1 and PPARA protein levels. Moreover, global m⁶A methylations were significantly reduced and accompanied by downregulated METTL3 and YTHDF2 protein expression by CORT treatment. Interestingly, the significant differences of site-specific m⁶A demethylation were observed in exon7 of PPARA mRNA. Additionally, a mutation of the m⁶A site in the PPARA gene fused GFP and revealed that demethylated RRACH in PPARA CDS impaired protein translation in vitro. In conclusion, these results indicated that m⁶A-mediated PPARA translational suppression contributes to CORT-induced visceral fat deposition in chickens, which may provide a new target for the treatment of Cushing's syndrome.

Highly different effects of phage therapy and antibiotic therapy on immunological responses of chickens infected with Salmonella enterica serovar Typhimurium

The appearance of bacteria resistant to most or even all known antibiotics has become a serious medical problem. One such promising and effective alternative form of therapy may be the use of phages, the administration of which is considered to be safe and highly effective, especially in animals with drug-resistant infections. Although there have been no reports to date suggesting that bacteriophages can cause any severe complications or adverse effects, we still know little about their interactions with animal organisms, especially in the context of the functioning of the immune system. Therefore, the aim of the present study was to compare the impact of the application of selected bacteriophages and antibiotics (enrofloxacin and colistin), commonly used in veterinary medicine, on immune functions in Salmonella enterica serovar Typhimurium-infected chickens. The birds were infected with S. Typhimurium and then treated with a phage cocktail (14 days), enrofloxacin (5 days), or colistin (5 days). The concentrations of a panel of pro-inflammatory cytokines (IL-1β, IL-6, IFN-γ, IL-8, and IL-12) and cytokines that reveal anti-inflammatory effects (IL-10 and IL-4), the percentage of lymphocytes, and the level of stress hormones (corticosterone and cortisol), which significantly modulate the immune responses, were determined in different variants of the experiment. The phage cocktail revealed anti-inflammatory effects when administered either 1 day after infection or 2 days after S. Typhimurium detection in feces, as measured by inhibition of the increase in levels of inflammatory response markers (IL-1β, IL-6, IFN-γ, IL-8, and IL-12). This was also confirmed by increased levels of cytokines that exert an anti-inflammatory action (IL-10 and IL-4) following phage therapy. Moreover, phages did not cause a negative effect on the number and activity of lymphocytes’ subpopulations crucial for normal immune system function. These results indicate for the first time that phage therapy not only is effective but also can be used in veterinary medicine without disturbing immune homeostasis, expressed as cytokine imbalance, disturbed percentage of key immune cell subpopulations, and stress axis hyperactivity, which were observed in our experiments as adverse effects accompanying the antibiotic therapy.

Increasing Environmental Complexity by Providing Different Types of Litter and Perches during Early Rearing Boosts Coping Abilities in Domestic Fowl Chicks

Simple Summary

The benefits of rearing chicks in complex environments rather than barren environments are well established. However, the typical rearing environments for modern laying hens are still considerably more barren than the complex forest habitat of their ancestors. This small-scale experimental study investigated whether giving chicks of white Bovans Robust the possibility to express choices between different variants of the same resource could result in them being better able to cope with challenges, as well as being better able to make the most of new opportunities. We found that chicks with access to different types of litter and perches were less fearful, less chronically stressed, and were better prepared to cope with pathogenic challenges. Furthermore, they were more successful in a repeated opportunity test, implying an improved learning ability. Overall, the results suggest that rearing laying hen chicks in an environment with access to variation in relevant resources could be a simple and feasible way to increase complexity under commercial conditions. This input could result in them being more resistant to infection and better able to adapt to novel situations later in life.

Abstract

Early experience of a complex environment can improve biologically relevant traits related to coping abilities. However, the mechanisms underlying these positive effects have not been well explored. We hypothesized that giving chicks possibilities to express choices within relevant resources could be an important part of the mechanism, as well as a novel way to increase environmental complexity. In a balanced design, laying hen hatchlings of the white hybrid Bovans Robust were reared in a “single-choice” environment (single litter and perch type) or a “multi-choice” environment (four different litter and perch types). Immunological and behavioral indicators of chicks’ coping abilities were explored in this experimental study at three weeks of age. Chicks from “multi-choice” environments had shorter durations of tonic immobility, lower heterophil/lymphocyte ratios, higher natural antibody concentrations, and were more successful in gaining novel food rewards in a repeated opportunity test. These results imply that chicks having access to variation within resource types were less fearful, experienced less chronic stress, would be more able to cope with pathogenic challenges, and potentially had an improved learning ability. To conclude, the more complex environment, achieved by increasing chicks’ possibilities to choose, seemed to make chicks better prepared for potential challenges, boosting their adaptive capacities and their ability to make the most of opportunities.

Effects of Housing System on Anxiety, Chronic Stress, Fear, and Immune Function in Bovan Brown Laying Hens

The scientific community needs objective measures to appropriately assess animal welfare. The study objective was to assess the impact of housing system on novel physiological and behavioral measurements of animal welfare for laying hens, including secretory and plasma Immunoglobulin (IgA; immune function), feather corticosterone (chronic stress), and attention bias testing (ABT; anxiety), in addition to the well-validated tonic immobility test (TI; fearfulness). To test this, 184 Bovan brown hens were housed in 28 conventional cages (3 birds/cage) and 4 enriched pens (25 birds/pen). Feces, blood, and feathers were collected 4 times between week 22 and 43 to quantify secretory and plasma IgA and feather corticosterone concentrations. TI tests and ABT were performed once. Hens that were from cages tended to show longer TI, had increased feather corticosterone, and decreased secretory IgA at 22 weeks of age. The caged hens fed quicker, and more hens fed during the ABT compared to the penned hens. Hens that were in conventional cages showed somewhat poorer welfare outcomes than the hens in enriched pens, as indicated by increased chronic stress, decreased immune function at 22 weeks of age but no other ages, somewhat increased fear, but reduced anxiety. Overall, these novel markers show some appropriate contrast between housing treatments and may be useful in an animal welfare assessment context for laying hens. More research is needed to confirm these findings.

Effect of Immune Stress on Growth Performance and Immune Functions of Livestock: Mechanisms and Prevention

Simple Summary

Immune stress is an important stressor in domestic animals that leads to decreased feed intake, slow growth, and reduced disease resistance of pigs and poultry. Especially in high-density animal feeding conditions, the risk factor of immune stress is extremely high, as they are easily harmed by pathogens, and frequent vaccinations are required to enhance the immunity function of the animals. This review mainly describes the causes, mechanisms of immune stress and its prevention and treatment measures. This provides a theoretical basis for further research and development of safe and efficient prevention and control measures for immune stress in animals.

Abstract

Immune stress markedly affects the immune function and growth performance of livestock, including poultry, resulting in financial loss to farmers. It can lead to decreased feed intake, reduced growth, and intestinal disorders. Studies have shown that pathogen-induced immune stress is mostly related to TLR4-related inflammatory signal pathway activation, excessive inflammatory cytokine release, oxidative stress, hormonal disorders, cell apoptosis, and intestinal microbial disorders. This paper reviews the occurrence of immune stress in livestock, its impact on immune function and growth performance, and strategies for immune stress prevention.

Effects of Key Farm Management Practices on Pullets Welfare—A Review

Simple Summary

Studies on animal behavior and welfare have reported that improving the management practices of pullets can enhance their growth, as well as their physical and mental condition, thus benefiting the productivity of laying hens. Therefore, in this review, we elaborated on the key effective farm management measures, including housing type and matching, flock status, and environmental management and enrichment, to provide the necessary information to incorporate welfare into chicken rearing and its importance in production, with the aim of improving the quantity and quality of chicken products.

Abstract

Studies on animal behavior and welfare have reported that improving the management practices of pullets can enhance their growth, as well as their physical and mental condition, thus benefiting the productivity of laying hens. There is growing confidence in the international community to abandon the conventional practices of “cage-rearing and beak-trimming” to improve the welfare of chickens. Therefore, in this review, we summarized some of the effective poultry management practices that have provided welfare benefits for pullets. The results are as follows: 1. Maintaining similar housing conditions at different periods alleviates fear and discomfort among pullets; 2. Pullets reared under cage-free systems have better physical conditions and temperaments than those reared in cage systems, and they are more suitable to be transferred to similar housing to lay eggs; 3. Improving flock uniformity in appearance and body size has reduced the risk of pecking and injury; 4. Maintaining an appropriate population (40–500 birds) has reduced flock aggressiveness; 5. A combination of 8–10 h of darkness and 5–30 lux of light-intensity exposure via natural or warm white LED light has achieved a welfare–performance balance in pullets. (This varies by age, strain, and activities.); 6. Dark brooders (mimicking mother hens) have alleviated fear and pecking behaviors in pullets; 7. The air quality of the chicken house has been effectively improved by optimizing feed formulation and ventilation, and by reducing fecal accumulation and fermentation; 8. Complex environments (with litter, perches, straw bales, slopes, platforms, outdoor access, etc.) have stimulated the activities of chickens and have produced good welfare effects. In conclusion, the application of comprehensive management strategies has improved the physical and mental health of pullets, which has, in turn, improved the quantity and quality of poultry products.

The Interplay between Salmonella and Intestinal Innate Immune Cells in Chickens

Salmonellosis is a common infection in poultry, which results in huge economic losses in the poultry industry. At the same time, Salmonella infections are a threat to public health, since contaminated poultry products can lead to zoonotic infections. Antibiotics as feed additives have proven to be an effective prophylactic option to control Salmonella infections, but due to resistance issues in humans and animals, the use of antimicrobials in food animals has been banned in Europe. Hence, there is an urgent need to look for alternative strategies that can protect poultry against Salmonella infections. One such alternative could be to strengthen the innate immune system in young chickens in order to prevent early life infections. This can be achieved by administration of immune modulating molecules that target innate immune cells, for example via feed, or by in-ovo applications. We aimed to review the innate immune system in the chicken intestine; the main site of Salmonella entrance, and its responsiveness to Salmonella infection. Identifying the most important players in the innate immune response in the intestine is a first step in designing targeted approaches for immune modulation.

Immune parameters in two different laying hen strains during five production periods

During life, the number and function of immune cells change with potential consequences for immunocompetence of an organism. In laying hens, studies have primarily focused on early development of immune competence and only few have investigated systemic and lymphatic distribution of leukocyte subsets during adolescence and the egg-laying period. The present study determined the number of various leukocyte types in blood, spleen, and cecal tonsils of 10 Lohmann Brown-Classic and 10 Lohmann LSL-Classic hens per wk of life 9/10, 15/16, 23/24, 29/30, and 59/60, encompassing important production as well as developmental stages, by flow cytometry. Although immune traits differed between the 2 hen strains, identical patterns of age-related immunological changes were found. The numbers of all investigated lymphocyte types in the spleen as well as the numbers of blood γδ T cells increased from wk 9/10 to 15/16. This suggests an ongoing release of lymphocytes from primary lymphoid tissues and an influx of blood lymphocytes into the spleen due to novel pathogen encounters during adolescence. A strong decrease in the number of CTL and γδ T cells and an increase in innate immune cells within blood and spleen were found between wk of life 15/16 and 23/24, covering the transition phase to egg-laying activity. Numbers of peripheral and splenic lymphocytes remained low during the egg-laying period or even further decreased, for example blood CD4⁺ T cells and splenic γδ T cells. Functional assessments showed that in vitro IFN-γ production of mitogen-stimulated splenocytes was lower in wk 60. Taken together, egg-laying activity seems to alter the immune system toward a more pronounced humoral and innate immune response, with probable consequences for the immunocompetence and thus for productivity, health and welfare of the hens.

Effect of a Mineral-Microbial Deodorizing Preparation on the Functions of Internal Organs and the Immune System in Commercial Poultry

Animal production is identified as one of the main sources of high concentrations of odours, which are related to air pollution, health problems of living organisms and indirect negative impact on production results. One common method for reducing emissions of ammonia is using preparations containing probiotics and hygroscopic or disinfecting compounds. This study was undertaken in order to determine the impact of innovative mineral-microbial deodorizing preparation, which reduces odorous gases, applying to the litter once a week in poultry houses on the physiological status of breeder chickens, broiler chickens and turkeys. Samples were collected after slaughter and analyzed using ELISA tests, flow cytometry and biochemical methods. Biochemical markers of the liver and kidney profile (ALT, AST, LDH, ALP, CK, TP, CALC, PHOS) and the titers of specific antibodies against AEV, aMPV, AAvV-1, IBDV, HEV, BA were analyzed in serum samples. The percentage contribution of T and B lymphocyte subpopulations was determined in the samples of tracheal mucosa, blood, and spleen. No significant differences were found between the control and experimental group with regard to all the analyzed parameters, with some exceptions for biochemistry. The results of our study indicated that mineral-microbial deodorizing preparation did not affect the physiological status of birds.

How the kinetic behavior of organic chickens affects productive performance and blood and meat oxidative status: a study of six poultry genotypes

The aim of this study was to analyze the relationship between the kinetic behavior, carcass characteristics, oxidative status (blood and meat), and meat fatty acid profiles of 6 organically reared slower growing chicken genotypes (SrG). One hundred male chickens of 6 SrG were used: Ranger Classic (RC), Ranger Gold (RG), Rowan Ranger (RR), RedJA (RJ), CY Gen 5 JA87 (CY), and M22 × JA87 (M). Twenty chickens/genotype were selected to analyze behavior, while, 15 individuals were slaughtered and different traits were analyzed in the blood and drumstick meat. The variables were grouped into different principal components: kinetic activity (PC1, with explorative attitude as the highest score), productive performance (PC2, carcass and head/feet yields), blood (PC3, carbonyls, and TBARS) and meat (PC6, thiols, and TBARS) markers, technological traits (PC4, pH, and color), proximate meat composition (PCA5, moisture, lipids, protein, and ash), fatty acid profile, and nutritional indexes (PC7, IP, and PUFAn-3). Uni- and bivariate analyses showed a strong positive association between kinetic behaviors and blood and meat oxidation and a medium positive association with fatty acid profile and nutritional indexes, whereas a negative association was found between productive performance loads and the technological traits of meat. Generalized linear models showed that all PCs were influenced by genotype. In particular, CY and M resulted as less active genotypes; conversely, RR showed more kinetic activity, whereas RJ, RG, and RC exhibited intermediate levels of activity. Cluster analysis of kinetic behavior and blood or meat oxidative status highlighted 2 groups: nonwalking (NW: CY and M) and walking (W: RC, RG, RR, and RJ) animals. However, in the W group, another was visualized, constituted by genotypes with high kinetic activity resulting in the worst oxidative balance (Walking not trained-genotypes, Wnt: RR and RJ). The present results confirmed that the kinetic behavior of SrG genotypes is negatively correlated with productive performance. Furthermore, a significant association between kinetic behavior and blood (positively correlated) or meat (negatively correlated) oxidative status was noted. Such differences are mainly due to the intrinsic response of the genotypes used (i.e., training-walking capacity).

Short- and long-term consequences of stocking density during rearing on the immune system and welfare of laying hens

Already during early life, chickens need to cope with chronic stressors that can impair their health and welfare, with stocking density being one of the most influential factors. Nevertheless, there is a gap in research on the influence of stocking density on laying hens during rearing and in the subsequent laying period. This study therefore investigated how stocking density during rearing affects the immune system and welfare of pullets, and whether effects are persistent later in life. Pullets were reared at either low (13 birds/m²) or high (23 birds/m²) stocking densities but in identical group sizes from wk 7 to 17. Afterward, hens were kept at the same stocking density (2.4 birds/m²) until wk 28. Blood and tissue samples (spleen and cecal tonsils) were collected at the end of the rearing period and in the laying period. The parameters evaluated encompassed number and distribution of leukocytes and lymphocyte subsets in blood and lymphatic tissue, lymphocyte functionality, plasma corticosterone concentrations as well as behavior and physical appearance of hens. At the end of rearing, pullets kept under high stocking density had lower numbers of T lymphocytes, especially γδ T cells in blood, spleen, and cecal tonsils and displayed a higher heterophil to lymphocyte ratio. These effects are mostly persistent during the laying period, although stocking density was identical at this time. Furthermore, birds from the high stocking density group showed less active behavior, more pecking behavior and worse physical appearance throughout both examination periods. In conclusion, stocking density during rearing affects pullets' immune system and behavior not only in the rearing, but also subsequently in the laying period, indicating a strong correlation between health and welfare during rearing and the laying period.

Stress and immunity in poultry: light management and nanotechnology as effective immune enhancers to fight stress

The poultry industry plays a significant role in boosting the economy of several countries, particularly developing countries, and acts as a good, cheap, and affordable source of animal protein. A stress-free environment is the main target in poultry production. There are several stressors, such as cold stress, heat stress, high stocking density, and diseases that can affect birds and cause several deleterious changes. Stress reduces feed intake and growth, as well as impairs immune response and function, resulting in high disease susceptibility. These effects are correlated with higher corticosteroid levels that modulate several immune pathways such as cytokine-cytokine receptor interaction and Toll-like receptor signaling along with induction of excessive production of reactive oxygen species (ROS) and thus oxidative stress. Several approaches have been considered to boost bird immunity to overcome stress-associated effects. Of these, dietary supplementation of certain nutrients and management modifications, such as light management, are commonly considered. Dietary supplementations improve bird immunity by improving the development of lymphoid tissues and triggering beneficial immune modulators and responses. Since nano-minerals have higher bioavailability compared to inorganic or organic forms, they are highly recommended to be included in the bird's diet during stress. Additionally, light management is considered a cheap and safe approach to control stress. Changing light from continuous to intermittent and using monochromatic light instead of the normal light improve bird performance and health. Such changes in light management are associated with a reduction of ROS production and increased antioxidant production. In this review, we discuss the impact of stress on the immune system of birds and the transcriptome of oxidative stress and immune-related genes, in addition, how nano-minerals supplementations and light system modulate or mitigate stress-associated effects.

Age and Staphylococcus aureus Inoculation Route Differentially Alter Metabolic Potential and Immune Cell Populations in Laying Hens

In 2018 and 2019, Staphylococcus aureus was isolated from multiple post-molt commercial laying hens with unusually high mortality. A challenge study was conducted to elucidate the role of S. aureus in this disease outbreak and the work herein represents the assessment of immunological responses in laying hens experimentally infected with S. aureus isolates from these cases. A total of 200 laying hens at 22 or 96 weeks of age (100/ age group) were assigned to 1 of 4 experimental inoculation groups (negative control, oral gavage, subcutaneous injection, or intravenous injection) after a 72 h acclimation period. Blood samples were taken prior to inoculation (baseline), 6 h post-inoculation (pi), 24 hpi, 3 dpi, and 7 dpi. Additional spleen samples to further assess systemic immunity were taken at baseline, 3 and 8 dpi. Metabolic phenotypes of peripheral blood mononuclear cells (PBMC) were isolated and assessed by Seahorse metabolic assay. Immune cell profiles in the spleen and PBMC were assessed by multicolor flow cytometry. At baseline, 96-week-old laying hens had 26.7% fewer PBMC-derived T cells compared to 22-week-old birds. Older hens had 28.9% increased helper T cell (TH) populations and 60.5% reduced γδ T cells (P = 0.03 and < 0.0001) which may contribute to variable clinical responses between age groups; however, no age-related differences in metabolic potential were observed. Metabolic outcomes showed that birds remained stressed from transport and re-housing past a 72 h acclimation period and through 24 h- 3 days post-inoculation. Inoculation with S. aureus generally reduced oxidative and glycolytic potentials compared to the control, with the greatest reductions observed in birds inoculated by intravenous injection (P < 0.05). Overall CD3+ T cell populations showed significant reductions in the intravenous group compared to other inoculation routes from 24 hpi to 7 dpi (23.6-39.0%; P ≤ 0.0001). These results suggest that age-related baseline differences in T cell populations and changes to T cell subpopulations and other immune cells due to inoculation route may have an additive effect on S. aureus- induced reductions in metabolic potential; however, further research linking metabolic potential and immune cell profiles is needed.

Factor Influences for Diagnosis and Vaccination of Avian Infectious Bronchitis Virus (Gammacoronavirus) in Chickens

Infectious bronchitis virus (IBV) is a major economic problem in commercial chicken farms with acute multiple-system infection, especially in respiratory and urogenital systems. A live-attenuated and killed vaccine is currently immunized to control IBV infection; however, repeated outbreaks occur in both unvaccinated and vaccinated birds due to the choice of inadequate vaccine candidates and continuous emergence of novel infectious bronchitis (IB) variants and failure of vaccination. However, similar clinical signs were shown in different respiratory diseases that are essential to improving the diagnostic assay to detect IBV infections. Various risk factors involved in the failure of IB vaccination, such as various routes of application of vaccination, the interval between vaccinations, and challenge with various possible immunosuppression of birds are reviewed. The review article also highlights and updates factors affecting the diagnosis of IBV disease in the poultry industry with differential diagnosis to find the nature of infections compared with non-IBV diseases. Therefore, it is essential to monitor the common reasons for failed IBV vaccinations with preventive action, and proper diagnostic facilities for identifying the infective stage, leading to earlier control and reduced economic losses from IBV disease.

Redox Homeostasis in Poultry: Regulatory Roles of NF-κB

Redox biology is a very quickly developing area of modern biological sciences, and roles of redox homeostasis in health and disease have recently received tremendous attention. There are a range of redox pairs in the cells/tissues responsible for redox homeostasis maintenance/regulation. In general, all redox elements are interconnected and regulated by various means, including antioxidant and vitagene networks. The redox status is responsible for maintenance of cell signaling and cell stress adaptation. Physiological roles of redox homeostasis maintenance in avian species, including poultry, have received limited attention and are poorly characterized. However, for the last 5 years, this topic attracted much attention, and a range of publications covered some related aspects. In fact, transcription factor Nrf2 was shown to be a master regulator of antioxidant defenses via activation of various vitagenes and other protective molecules to maintain redox homeostasis in cells/tissues. It was shown that Nrf2 is closely related to another transcription factor, namely, NF-κB, responsible for control of inflammation; however, its roles in poultry have not yet been characterized. Therefore, the aim of this review is to describe a current view on NF-κB functioning in poultry with a specific emphasis to its nutritional modulation under various stress conditions. In particular, on the one hand, it has been shown that, in many stress conditions in poultry, NF-κB activation can lead to increased synthesis of proinflammatory cytokines leading to systemic inflammation. On the other hand, there are a range of nutrients/supplements that can downregulate NF-κB and decrease the negative consequences of stress-related disturbances in redox homeostasis. In general, vitagene-NF-κB interactions in relation to redox balance homeostasis, immunity, and gut health in poultry production await further research.

Effects of Different Laying Hen Species on Odour Emissions

Odour is one of the main environmental concerns in the laying hen industry and may also influence animal health and production performance. Previous studies showed that odours from the laying hen body are primarily produced from the microbial fermentation (breakdown) of organic materials in the caecum, and different laying hen species may have different odour production potentials. This study was conducted to evaluate the emissions of two primary odorous gases, ammonia (NH₃) and hydrogen sulphide (H₂S), from six different laying hen species (Hyline, Lohmann, Nongda, Jingfen, Xinghua and Zhusi). An in vitro fermentation technique was adopted in this study, which has been reported to be an appropriate method for simulating gas production from the microbial fermentation of organic materials in the caecum. The results of this study show that Jingfen produced the greatest volume of gas after 12 h of fermentation (p < 0.05). Hyline had the highest, while Lohmann had the lowest, total NH₃ emissions (p < 0.05). The total H₂S emissions of Zhusi and Hyline were higher than those of Lohmann, Jingfen and Xinghua (p < 0.05), while Xinghua exhibited the lowest total H₂S emissions (p < 0.05). Of the six laying hen species, Xinghua was identified as the best species because it produced the lowest total amount of NH₃ + H₂S (39.94 µg). The results for the biochemical indicators showed that the concentration of volatile fatty acids (VFAs) from Zhusi was higher than that for the other five species, while the pH in Zhusi was lower (p < 0.01), and the concentrations of ammonium nitrogen (NH⁴⁺), uric acid and urea in Xinghua were lower than those in the other species (p < 0.01). Hyline had the highest change in SO₄^2- concentration during the fermentation processes (p < 0.05). In addition, the results of the correlation analysis suggested that NH₃ emission is positively related to urease activities but is not significantly related to the ureC gene number. Furthermore, H₂S emission was observed to be significantly related to the reduction of SO₄^2- but showed no connection with the aprA gene number. Overall, our findings provide a reference for future feeding programmes attempting to reduce odour pollution in the laying hen industry.

Muscle Antioxidant Activity and Meat Quality Are Altered by Supplementation of Astaxanthin in Broilers Exposed to High Temperature

This study investigated the effect of dietary astaxanthin (AST) on the meat quality, antioxidant status, and immune response of chickens exposed to heat stress. Four hundred and eighty male broilers were assigned to four treatments including AST0, AST20, AST40, and AST80 with 0, 20, 40, and 80 ppm astaxanthin supplementation levels, respectively. There was a linear decrease of malondialdehyde (MDA) in leg muscle. Catalase and superoxide dismutase levels in the plasma were linearly increased. There was a linear increase in the level of total antioxidant capacity in the leg muscle. The 3-ethylbenzothiazoline-6-sulfonate reducing activity of leg muscle was significantly increased in the AST80 treatment. The AST40 treatment showed an increase in 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity of leg muscles. Breast meat redness and yellowness were linearly increased. The astaxanthin-supplemented treatments exhibited lower drip loss and MDA concentration of leg muscle compared with the AST0 treatment at days 3 and 9 of storage. Supplementation of 40 or 80 mg/kg astaxanthin significantly decreased heat shock protein (HSP)27, HSP70, tumor necrosis factor alpha, and interleukin-6 expression in the livers. The feather corticosterone was significantly lower in the astaxanthin-supplemented treatments than in the AST0 treatment. In conclusion, astaxanthin decreased the hyperthermic stress level and improved meat quality, and antioxidant status of chickens exposed to heat stress.