Environmental complexity: A buffer against stress in the domestic chick

Review: Environmental enrichment builds functional capacity and improves resilience as an aspect of positive welfare in production animals

The success of the animal in coping with challenges, and in harnessing opportunities to thrive, is central to its welfare. Functional capacity describes the capacity of molecules, cells, organs, body systems, the whole animal, and its community to buffer against the impacts of environmental perturbations. This buffering capacity determines the ability of the animal to maintain or regain functions in the face of environmental perturbations, which is recognised as resilience. The accuracy of physiological regulation and the maintenance of homeostatic balance underwrite the dynamic stability of outcomes such as biorhythms, feed intake, growth, milk yield, and egg production justifying their assessment as indicators of resilience. This narrative review examines the influence of environmental enrichments, especially during developmental stages in young animals, in building functional capacity and in its subsequent expression as resilience. Experience of enriched environments can build skills and competencies across multiple functional domains including but not limited to behaviour, immunity, and metabolism thereby increasing functional capacity and facilitating resilience within the context of challenges such as husbandry practices, social change, and infection. A quantitative method for measuring the distributed property of functional capacity may improve its assessment. Methods for analysing embedded energy (emergy) in ecosystems may have utility for this goal. We suggest functional capacity provides the common thread that links environmental enrichments with an ability to express resilience and may provide a novel and useful framework for measuring and reporting resilience. We conclude that the development of functional capacity and its subsequent expression as resilience is an aspect of positive animal welfare. The emergence of resilience from system dynamics highlights a need to shift from the study of physical and mental states to the study of physical and mental dynamics to describe the positive dimension of animal welfare.

Resource choice during ontogeny enhances both the short- and longer-term welfare of laying hen pullets

We hypothesised that resource choice during early life contributes to both current and longer-term beneficial effects on animal welfare. We investigated this hypothesis in a longitudinal cross-over experiment with laying hen pullets (Gallus gallus domesticus) reared in pens with one or four litter and perch types, respectively (n = 8 pens/treatment, all providing ample and identical litter and perch space). After 4 weeks (chick period), half the pens were modified to provide the opposite treatment (juvenile period). After 11 more weeks, all groups were moved to novel, identical laying pens (adult period; Week 16-27). In support of our hypothesis, the opportunity to choose between multiple litter and perch variants was associated with higher levels of positively-valenced behaviours, including play as chicks and dustbathing as juveniles and adults, and lower levels of negatively-valenced behaviours, including feather pecking as chicks and juveniles and aggressive pecking as adults. Resource choice in the juvenile period also led to better juvenile and adult plumage condition, and greater growth as adults. We conclude that the opportunity to choose among different litter and perch types, instead of having only one type of each, had both short- and longer-term positive effects on the birds' affective states and physical condition.

Responsive Alternative Splicing Events of Opisthopappus Species against Salt Stress

Salt stress profoundly affects plant growth, prompting intricate molecular responses, such as alternative splicing (AS), for environmental adaptation. However, the response of AS events to salt stress in Opisthopappus (Opisthopappus taihangensis and Opisthopappus longilobus) remains unclear, which is a Taihang Mountain cliff-dwelling species. Using RNA-seq data, differentially expressed genes (DEGs) were identified under time and concentration gradients of salt stress. Two types of AS, skipped exon (SE) and mutually exclusive exons (MXE), were found. Differentially alternative splicing (DAS) genes in both species were significantly enriched in "protein phosphorylation", "starch and sucrose metabolism", and "plant hormone signal transduction" pathways. Meanwhile, distinct GO terms and KEGG pathways of DAS occurred between two species. Only a small subset of DAS genes overlapped with DEGs under salt stress. Although both species likely adopted protein phosphorylation to enhance salt stress tolerance, they exhibited distinct responses. The results indicated that the salt stress mechanisms of both Opisthopappus species exhibited similarities and differences in response to salt stress, which suggested that adaptive divergence might have occurred between them. This study initially provides a comprehensive description of salt responsive AS events in Opisthopappus and conveys some insights into the molecular mechanisms behind species tolerance on the Taihang Mountains.

Measuring Chronic Stress in Broiler Chickens: Effects of Environmental Complexity and Stocking Density on Immunoglobulin-A Levels

Commercial housing conditions may contribute to chronic negative stress in broiler chickens, reducing their animal welfare. The objective of this study was to determine how secretory (fecal) and plasma immunoglobulin-A (IgA) levels in fast-growing broilers respond to positive and negative housing conditions. In three replicated experiments, male Ross 708 broilers (n = 1650/experiment) were housed in a 2 × 2 factorial study of high or low environmental complexity and high or low stocking density. In experiments 1 and 3 but not in experiment 2, high complexity tended to positively impact day 48 plasma IgA concentrations. When three experiments were combined, high complexity positively impacted day 48 plasma IgA concentrations. Stocking density and the complexity × density interaction did not impact day 48 plasma IgA concentrations. Environmental complexity and the complexity × density interaction did not impact day 48 secretory IgA concentrations. A high stocking density negatively impacted day 48 secretory IgA concentrations overall but not in individual experiments. These results suggest that environmental complexity decreased chronic stress, while a high stocking density increased chronic stress. Thus, plasma IgA levels increased under high-complexity housing conditions (at day 48), and secretory IgA levels (at day 48) decreased under high-density conditions, suggesting that chronic stress differed among treatments. Therefore, these measures may be useful for quantifying chronic stress but only if the statistical power is high. Future research should replicate these findings under similar and different housing conditions to confirm the suitability of IgA as a measure of chronic stress in broiler chickens.

Environmental change or choice during early rearing improves behavioural adaptability in laying hen chicks

Laying hens are typically moved to a novel environment after rearing, requiring adaptability to cope with change. We hypothesized that the standard rearing of laying hen chicks, in non-changing environments with limited choices (a single variant of each resource), impairs their ability to learn new routines, use new equipment and exploit new resources. On the contrary, rearing in a changing environment that also offers a choice of resource variants could better prepare chicks for the unexpected. To explore this hypothesis, environmental change and choice were manipulated in a 2 × 2 factorial experiment. Compared to standard rearing, greater change during early rearing, through repeatedly swapping litter and perch types, reduced initial freezing when exposed to a novel environment suggesting a lower fear response. Greater choice during rearing, through simultaneous access to multiple litter and perch types, resulted in shorter latencies to solve a detour task, more movement in novel environments and less spatial clustering, suggesting improved spatial skills and higher exploration. However, combining both change and choice did not generally result in greater improvement relative to providing one or the other alone. We conclude that environmental change and choice during rearing have different positive but non-synergistic effects on later adaptability potential.

Adverse effects of heat stress during summer on broiler chickens production and antioxidant mitigating effects

Broiler chicken meat is a good source of protein consumed universally, and is one of the most commonly farmed species in world. In addition to providing food, poultry non-edible byproducts also have value. A major advantage of broiler chicken production is their short production cycle, which results in a greater rate of production in comparison to other species. However, as with any production system, there are constraints in broiler production with one of the most pressing being energy requirements to keep the birds warm as chicks and cool later in the growth cycle, as a result of the cost needing mechanical heating and cooling. While this is feasible in more advanced economies, this is not readily affordable in developing economies. As a result, farmers rely on natural ventilation to cool the rearing houses, which generally becoming excessively warm with the resultant heat stress on the birds. Since little can be done without resorting to mechanical ventilation and cooling, exploring the use of other means to reduce heat stress is needed. For this review, we cover the various factors that induce heat stress, the physiological and behavioral responses of broiler chickens to heat stress. We also look at mitigating the adverse effect of heat stress through the use of antioxidants which possess either an anti-stress and/or antioxidant effects.

Enhancing their quality of life: environmental enrichment for poultry

Providing environmental enrichments that increase environmental complexity can benefit poultry welfare. This Poultry Science Association symposium paper is structured around four themes on 1) poultry preferences and affective states 2) species-specific behavior, including play behavior and the relationship between behavior, activity level and walking ability, 3) environmental enrichment and its relationship with indicators of welfare, and 4) a case study focusing on the application of enrichments in commercial broiler chicken production. For effective enrichment strategies, the birds' perspective matters most, and we need to consider individual variation, social dynamics, and previous experience when assessing these strategies. Play behavior can be a valuable indicator of positive affect, and while we do not yet know how much play would be optimal, absence of play suggests a welfare deficit. Activity levels and behavior can be improved by environmental modifications and prior research has shown that the activity level of broilers can be increased, at least temporarily, by increasing the environmental complexity. However, more research on impacts of enrichments on birds' resilience, on birds in commercial conditions, and on slow(er)-growing strains is needed. Finally, incorporating farmers' expertise can greatly benefit enrichment design and implementation on commercial farms.

Early life environment affects behavior, welfare, gut microbiome composition, and diversity in broiler chickens

This study aimed to identify whether early-life conditions in broiler chickens could affect their behavior and welfare, and whether or not this was associated with an altered gut microbiome composition or diversity. Broilers were tested in a 2 x 2 factorial design with hatching conditions [home pen (OH) or at the hatchery (HH)] and enrichment (dark brooder (EE) or no brooder (NE) until 14 days of age) as factors (N = 6 per treatment combination). Microbiota composition was measured in the jejunum on days (d) 7, 14, and 35 and in pooled fecal samples on day 14. A novel environment test (NET) was performed on days 1 and 11, and the behavior was observed on days 6, 13, and 33. On day 35, composite asymmetry was determined and footpad dermatitis and hock burn were scored. In their home pen, HH showed more locomotion than OH (P = 0.05), and NE were sitting more and showed more comfort behavior than EE at all ages (P <0.001 and P = 0.001, respectively). On days 6 and 13 NE showed more eating and litter pecking while sitting, but on day 33 the opposite was found (age^*enrichment: P = 0.05 and P <0.01, respectively). On days 1 and 11, HH showed more social reinstatement in the NET than OH, and EE showed more social reinstatement than NE (P <0.05). Composite asymmetry scores were lower for EE than NE (P <0.05). EE also had less footpad dermatitis and hock burn than NE (P <0.001). Within OH, NE had a more diverse fecal and jejunal microbiome compared to EE on day 14 (feces: observed richness: P = 0.052; jejunum: observed richness and Shannon: P <0.05); the principal component analysis (PCA) showed differences between NE and EE within both HH and OH in fecal samples on day 14, as well as significant differences in bacterial genera such as Lactobacillus and Lachnospiraceae (P <0.05). On day 35, PCA in jejunal samples only showed a trend (P = 0.068) for differences between NE vs. EE within the OH. In conclusion, these results suggest that especially the dark brooder affected the behavior and had a positive effect on welfare as well as affected the composition and diversity of the microbiome. Whether or not the behavior was modulated by the microbiome or vice versa remains to be investigated.

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.

Why-Oh-Why? Dark Brooders Reduce Injurious Pecking, Though Are Still Not Widely Used in Commercial Rearing of Layer Pullets

Simple Summary

Dark brooders mimic some aspects of maternal care, such as the provision of heat and a dark resting area. Dark brooders have a long-lasting reducing effect on injurious pecking, which improves feather cover and reduces mortality due to cannibalism into adulthood. The economic benefits include a reduction of costs for heating in the first weeks of life, and in adult layers, they improve the total egg production and may reduce floor egg laying. Despite the well-accepted knowledge of the positive effects of dark brooders on the prevention of injurious pecking, few farmers actually use them in their rearing facilities. In this paper, we review the effects of dark brooders on the welfare of pullets and layers and discuss the factors that likely contribute to their low usage in commercial systems, including the lack of commercially available brooder options and the size of the brooders, as well as the lack of information on the direct economic aspects.

Abstract

Dark brooders, i.e., horizontal heating elements for chicks equipped with curtains, mimic some aspects of maternal care, such as the provision of heat and a dark area for chicks to rest. Thus, they can be considered as artificial passive replacements of a mother hen. Despite their advantages in animal welfare and the likely positive outcomes in production and economy, dark brooders are rarely used in commercial layer pullet facilities. The main positive effect on welfare is a reduction of injurious pecking during the rearing and laying periods, which results in improved feather cover and reduced skin injuries and mortality due to cannibalism. Other welfare benefits include improved rest in dark-brooded chicks and reduced fearfulness at all ages tested (i.e., from 4 to 26 weeks). The impact on production and economy is seen in a reduction of the energy costs in the first weeks of life due to radiant heating, as well as improved total egg production and reduced floor egg laying. The aim of this paper is to review the existing literature on the effects of dark brooders on injurious pecking and other welfare issues in layers, including speculations on the possible explanations for improved welfare. We also discuss the possible reasons for why dark brooders are not applied more commonly in commercial practice, including insufficient information on the economic aspects of using brooders and the lack of commercially available brooder options.

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.

Salt responsive alternative splicing of a RING finger E3 ligase modulates the salt stress tolerance by fine-tuning the balance of COP9 signalosome subunit 5A

Increasing evidence points to the tight relationship between alternative splicing (AS) and the salt stress response in plants. However, the mechanisms linking these two phenomena remain unclear. In this study, we have found that Salt-Responsive Alternatively Spliced gene 1 (SRAS1), encoding a RING-Type E3 ligase, generates two splicing variants: SRAS1.1 and SRAS1.2, which exhibit opposing responses to salt stress. The salt stress-responsive AS event resulted in greater accumulation of SRAS1.1 and a lower level of SRAS1.2. Comprehensive phenotype analysis showed that overexpression of SRAS1.1 made the plants more tolerant to salt stress, whereas overexpression of SRAS1.2 made them more sensitive. In addition, we successfully identified the COP9 signalosome 5A (CSN5A) as the target of SRAS1. CSN5A is an essential player in the regulation of plant development and stress. The full-length SRAS1.1 promoted degradation of CSN5A by the 26S proteasome. By contrast, SRAS1.2 protected CSN5A by competing with SRAS1.1 on the same binding site. Thus, the salt stress-triggered AS controls the ratio of SRAS1.1/SRAS1.2 and switches on and off the degradation of CSN5A to balance the plant development and salt tolerance. Together, these results provide insights that salt-responsive AS acts as post-transcriptional regulation in mediating the function of E3 ligase.

High salinity severely affects plant growth and development, impairing crop production worldwide. E3 ligase is a stress-responsive regulator through ubiquitin-proteasome system for selective protein degradation. The E3s are regulated by transcriptional regulation and post-translational modifications. Here, we have discovered that stress-responsive AS acts as a post-transcriptional regulation modulating the function of E3 ligases. Intriguingly, the truncated proteins generated by salt-responsive AS play opposite roles compared with the full-length E3 ligase. The truncated isoform losing key domain could not degrade the target protein, instead, it interacts and competes with the E3 ligase through binding the same domain of the targets. This finding contributes significantly to a deeper mechanistic understanding of how AS regulates the function of E3 ligase in response to salt stress.

A Perspective on Strategic Enrichment for Brain Development: Is This the Key to Animal Happiness?

Livestock animals are sentient beings with cognitive and emotional capacities and their brain development, similar to humans and other animal species, is affected by their surrounding environmental conditions. Current intensive production systems, through the restrictions of safely managing large numbers of animals, may not facilitate optimal neurological development which can contribute to negative affective states, abnormal behaviors, and reduce experiences of positive welfare states. Enrichment provision is likely necessary to enable animals to reach toward their neurological potential, optimizing their cognitive capacity and emotional intelligence, improving their ability to cope with stressors as well as experience positive affect. However, greater understanding of the neurological impacts of specific types of enrichment strategies is needed to ensure enrichment programs are effectively improving the individual's welfare. Enrichment programs during animal development that target key neurological pathways that may be most utilized by the individual within specific types of housing or management situations is proposed to result in the greatest positive impacts on animal welfare. Research within livestock animals is needed in this regard to ensure future deployment of enrichment for livestock animals is widespread and effective in enhancing their neurological capacities.

Study of the effect of light on follicular development in laying hens

Objective

The oxidative stress status and changes of chicken ovary tissue after shading were studied, to determine the mechanism of the effect of shading on follicular development.

Methods

Twenty healthy laying hens (40 weeks old) with uniform body weight and the same laying rate were randomly divided into two groups (the shading group and normal light group). In the shading group, the cage was covered to reduce the light intensity inside the cage to 0 without affecting ventilation or food intake. The normal lighting group received no additional treatment. After 7 days of shading, oxidative stress related indicators and gene expression were detected.

Results

Analysis of paraffin and ultrathin sections showed that apoptosis of ovarian granulosa cells (GCs) increased significantly after light shading. Enzyme linked immunosorbent assay results revealed that the levels of total antioxidant capacity, malondialdehyde, superoxide dismutase (SOD), glutathione, catalase (CAT), and other substances in the sera, livers, ovaries, and follicular GCs of laying hens increased significantly after shading for 7 days; and reactive oxygen species (ROS) levels in the livers of laying hens also increased significantly. ROS in the serum, ovarian and GCs also increased. After shading for 7 days, the levels of 8-hydroxy-2 deoxyguanosine in the sera and ovarian tissues of laying hens increased significantly. Cell counting kit-8 detection showed that the proliferation activity of GCs in layer follicles decreased after shading for 7 days; the expression level of the anti-apoptotic gene B-cell lymphoma-2 in ovarian tissue and follicular GCs was significantly reduced, and the expression levels of pro-apoptotic caspase 3 (casp3), and SOD, glutathione peroxidase 2 (GPX2), and CAT were all significantly increased.

Conclusion

Oxidative stress induced by shading light has a serious inhibitory effect on follicular development during reproduction in laying hens.

Relationship between Range Use and Fearfulness in Free-Range Hens from Different Rearing Enrichments

Inconsistency between the environments of indoor pullet rearing and adult outdoor housing may increase the fearfulness in free-range hens. Rearing enrichments and/or range use may reduce adult fearfulness. Hy-Line Brown^® chicks (n = 1700) were reared inside across 16 weeks with three enrichment treatments: weekly changing novel objects, custom-designed perching/navigation structures, or no additional enrichments. Pullets were transferred to a free-range system at 16 weeks of age, with range access provided from 25 weeks. At 62 weeks, 135 hens were selected from the three rearing treatments and two ranging groups (indoor: no ranging and outdoor: daily ranging) based on individual radio-frequency identification tracking. Individual behavioural tests of tonic immobility, emergence, open field, and novel object (pen level) were carried out on hens. Spectrograms of vocalisations were analysed for the open field test, as well as computer vision tracking of hen locomotion. The results showed few effects of rearing treatments, with outdoor rangers less fearful than indoor hens. The latency to step in the open field test negatively correlated with hen feather coverage. These results show that individual variation in ranging behaviours is present even following rearing enrichment treatments, and subsequent range use might be an indicator of bird fearfulness.

Hens with benefits: Can environmental enrichment make chickens more resilient to stress?

Resilience, the degree to which individuals are physiologically and behaviourally impacted by stressors, can be enhanced by positive experiences (e.g. positive moods in human, environmental enrichment in rodents). Such effects are important for human health, but could also have important animal welfare implications in terms of farm, laboratory and zoo animals' abilities to cope with stressors. Here we investigated whether enrichments can increase resilience in chickens, the world's most abundant agricultural animal. The stress reactivity of laying hens housed for 5-6 weeks in enriched environments was compared to that of controls housed in smaller, emptier, less preferred pens, via: 1) startle reflex amplitudes to an abrupt, intense sensory stimulus (a light flash); and 2) autonomic responses to restraint and the sudden appearance of a novel object, assessed from decreases in comb temperature. Startle amplitudes were consistently reduced in the enriched hens, exerted with around one sixth the force seen in control hens. Maximum comb temperature decreases, and latencies for comb temperatures to return to prestress levels, also both fell by around a third. Enrichment thus reduced hens' intrinsic behavioural and physiological responses to standardized stressors (doing so even outside the home pen), just as occurs in laboratory rodents. Enrichment also reduced baseline comb temperature, suggesting that this could be a non-invasive indicator of welfare. Altered judgment biases did not seem to be the mechanism. Further work should now investigate the processes underlying the apparently enhanced stress resilience of animals housed in preferred conditions, and also investigate baseline comb temperature as a chronic stress indicator in poultry.

Environmental Display Can Buffer the Effect of Pesticides on Solitary Bees

Environmental quality (e.g., diversity of resource availability, nesting sites, environmental display) plays an important role in an animal’s life. While homogeneous environments can restrict organisms from developing activities such as food seeking (behavioral impairment), more complex environments allow animals to perform activities with learning and behavioral perfecting outcomes. Pesticides are known to affect the learning and foraging behaviors of bees; however, little is known about the counterbalance displayed by the environment. Herein, we conducted two experiments that simulated distinct environmental displays, in which the effects of a fungicide (Indar^TM 5EW-febunconazole) on solitary bee foraging activities were tested. We found that the fungicide only impaired the activities of bees in one of the studied environments. The difference in visitation rates and flower exploitation of bees between the two different environmental displays led to changes in metrics of bee–flower networks across environments. Linkage density, a metric associated with pollination efficiency that is known to be impacted by different environments, differed across environments. Our results showed that ecological interaction network metrics can differ regarding the different environmental displays. This study indicates that environmental complexity helps balance the negative effects of pesticides on solitary bees and highlights the potential use of solitary bees as model organisms for experimental simulations of environmental change.

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

During their lifespan, chickens are confronted with a wide range of acute and chronic stressors in their housing environment that may threaten their welfare and health by modulating the immune system. Especially chronic stressful conditions can exceed the individual's allostatic load, with negative consequences for immunity. A fully functional immune system is mandatory for health and welfare and, consequently, also for high productivity and safe animal products. This review provides a comprehensive overview of the impact of housing form, light regime as well as aerial ammonia and hydrogen sulfide concentrations on the immune system in chickens. Certain housing conditions are clearly associated with immunological alterations which potentially impair the success of vaccinations or affect disease susceptibility. Such poor conditions counteract sustainable poultry production. This review also outlines current knowledge gaps and provides recommendations for future research.