Does immune response cause oxidative stress in birds? A meta-analysis

Physiology and fertility of two gull species in relation to plastic additives' exposure

Understanding the impact of plastic and its additives on wild species is crucial as their presence in the environment increases. Polybrominated diphenyl ethers (PBDEs), once used as flame retardants, were restricted due to known toxic effects, but are still detected in the environment. Naturally occurring methoxylated PBDEs (MeO-BDEs) can result from PBDE transformation and may cause similar hazardous effects. Yellow-legged gulls (Larus michahellis, YLG) and Audouin's gulls (Ichthyaetus audouinii, AG) are highly susceptible to plastic additives, due to their distribution, trophic position, and behaviour. In this study, we assessed PBDEs and MeO-BDEs uptake in different tissues and their effects on physiological and reproductive parameters. Findings indicate that, apart from annual differences, adult AG accumulated more MeO-BDEs than YLG in a natural breeding habitat (Deserta), while the latter had lower PBDE levels than YLG breeding in the city of Porto. In relation to chicks, only YLG from Deserta showed higher PBDE concentrations than AG chicks. Individual analysis of each physiological parameter revealed impacts only for adult YLG from Deserta, with neurofunction and immune system inhibition at higher MeO-BDE concentrations. For chicks, AG showed impaired neurofunction, while YLG chicks from Porto exhibited potential genotoxicity effects triggered by higher MeO-BDE levels. Overall health analysis showed activation of antioxidant defences and compromised immune system in YLG adults from Porto due to high values of PBDEs, while chicks from Deserta exhibited inflammation and oxidative stress with high concentrations of MeO-BDEs in the same species. Fertility parameters showed significant differences for sperm counts though suggesting individuals may be able to compensate any exposure effects. This study confirms the widespread presence of plastic-associated compounds and their harmful effects on gulls, particularly on neurofunction, immune system, oxidative balance and fertility, especially due to the presence of MeO-BDEs.

Sex-specific effects of low-dose of acetamiprid on corticosterone levels but not on oxidative stress in House sparrows

Neonicotinoid insecticides are widely used in agriculture and have been linked to various detrimental physiological effects on wild birds. Despite this, the impact of acetamiprid - a less studied member of the neonicotinoid family - on the hypothalamic-pituitary-adrenal axis responsible for the hormonal regulation of the response to stress has rarely been examined in birds. In our study, we explored the effects of acetamiprid on feather levels of corticosterone, the major end product of the HPA, and blood oxidative status of House sparrows (Passer domesticus), following the ingestion of a low, field-realistic dose during two consecutive experiments in 2015 and 2016. We involved 112 birds in each experiment - 56 males and 56 females - that were administered a placebo or a dose of acetamiprid equivalent to 0.5% of the LD50 of the Zebra finch over the entire duration of the experiments, which lasted approximately three weeks. We measured corticosterone concentrations in feathers grown during an acclimation phase before ingestion and in newly grown feather after the experiment and assessed three oxidative stress markers in the blood. We found no impact of acetamiprid on oxidative stress markers. However, in 2015, male sparrows that ingested acetamiprid exhibited higher corticosterone levels in their feathers compared to those that received a placebo. No such difference was found in females. Interestingly, this effect was not observed in year 2016, which was characterised by less stressful conditions for the birds. These findings offer the first evidence of a potential effect of acetamiprid on corticosterone levels in a songbird, suggesting that ingesting this compound at very low dose may alter the endocrine physiology of the response to stress.

Correlated evolution of oxidative physiology and MHC-based immunosurveillance in birds

Maintenance and activation of the immune system incur costs, not only in terms of substrates and energy but also via collateral oxidative damage to host cells or tissues during immune response. So far, associations between immune function and oxidative damage have been primarily investigated at intra-specific scales. Here, we hypothesized that pathogen-driven selection should favour the evolution of effective immunosurveillance mechanisms (e.g. major histocompatibility complex, MHC) and antioxidant defences to mitigate oxidative damage resulting from immune function. Using phylogenetically informed comparative approaches, we provided evidence for the correlated evolution of host oxidative physiology and MHC-based immunosurveillance in birds. Species selected for more robust MHC-based immunosurveillance (higher gene copy numbers and allele diversity) showed stronger antioxidant defences, although selection for MHC diversity still showed a positive evolutionary association with oxidative damage to lipids. Our results indicate that historical pathogen-driven selection for highly duplicated and diverse MHC could have promoted the evolution of efficient antioxidant mechanisms, but these evolutionary solutions may be insufficient to keep oxidative stress at bounds. Although the precise nature of mechanistic links between the MHC and oxidative stress remains unclear, our study suggests that a general evolutionary investment in immune function may require co-adaptations at the level of host oxidative metabolism.

Dietary fatty acids modulate oxidative stress response to air pollution but not to infection

Anthropogenic changes to the environment expose wildlife to many pollutants. Among these, tropospheric ozone is of global concern and a highly potent pro-oxidant. In addition, human activities include several other implications for wildlife, e.g., changed food availability and changed distribution of pathogens in cities. These co-occurring habitat changes may interact, thereby modulating the physiological responses and costs related to anthropogenic change. For instance, many food items associated with humans (e.g., food waste and feeders for wild birds) contain relatively more ω6-than ω3-polyunsaturated fatty acids (PUFAs). Metabolites derived from ω6-PUFAs can enhance inflammation and oxidative stress towards a stimulus, whereas the opposite response is linked to ω3-derived metabolites. Hence, we hypothesized that differential intake of ω6-and ω3-PUFAs modulates the oxidative stress state of birds and thereby affects the responses towards pro-oxidants. To test this, we manipulated dietary ω6:ω3 ratios and ozone levels in a full-factorial experiment using captive zebra finches (Taeniopygia guttata). Additionally, we simulated an infection, thereby also triggering the immune system's adaptive pro-oxidant release (i.e., oxidative burst), by injecting lipopolysaccharide. Under normal air conditions, the ω3-diet birds had a lower antioxidant ratio (GSH/GSSG ratio) compared to the ω6-diet birds. When exposed to ozone, however, the diet effect disappeared. Instead, ozone exposure overall reduced the total concentration of the key antioxidant glutathione (tGSH). Moreover, the birds on the ω6-rich diet had an overall higher antioxidant capacity (OXY) compared to birds fed a ω3-rich diet. Interestingly, only the immune challenge increased oxidative damage, suggesting the oxidative burst of the immune system overrides the other pro-oxidative processes, including diet. Taken together, our results show that ozone, dietary PUFAs, and infection all affect the redox-system, but in different ways, suggesting that the underlying responses are decoupled despite that they all increase pro-oxidant exposure or generation. Despite lack of apparent cumulative effect in the independent biomarkers, the combined single effects could together reduce overall cellular functioning and efficiency over time in wild birds exposed to pathogens, ozone, and anthropogenic food sources.

Potential Effects of Garlic (Allium sativum L.) on the Performance, Immunity, Gut Health, Anti-Oxidant Status, Blood Parameters, and Intestinal Microbiota of Poultry: An Updated Comprehensive Review

The use of antibiotics as growth promoters or for the prevention of some poultry diseases has faced global concern and serious criticism. Their addition to poultry feed has shown hazardous effects, including the development of antimicrobial resistance and a potentially harmful effect on human health. To eliminate these threats, there is increasing interest in natural alternatives. Plant derivatives such as garlic (Allium sativum L.) and its derivatives are presently extensively used in the poultry production system. The dietary supplementation of broilers and layers with garlic induced improvement in the production parameters, carcass quality, and intestinal integrity. The modulation of the immune response against some important viral diseases has resulted from the supplementation of poultry with garlic. Moreover, garlic has been shown to modulate gut health through antibacterial and antiparasitic activities. Treatment with garlic can also mitigate oxidative stress and reduce free-radical production. The reduction of cholesterol levels and improvement of some liver and blood parameters were also reported following the dietary inoculation of garlic. This review was designed to investigate the influence of garlic as a dietary additive on the performance, immunity, gut health, anti-oxidant status, blood parameters, and intestinal microbiota of poultry.

Protective effects of puerarin on liver tissue in Salmonella-infected chicks: a proteomic analysis

Salmonella enterica is a zoonotic bacterium that not only causes serious economic losses to the livestock and poultry industries but also seriously endangers human health. Long-term indiscriminate use of antibiotics has led to drug resistance in Salmonella, and thus the identification of alternatives to antibiotics is crucial. In this study, the effects of puerarin on the S. enterica-infected chickens were investigated. A total of 360 chicks were randomly assigned as the control group (CON), the S. enterica group (S), and puerarin-treatment group (P). Chicks in the P group were fed the basal diet supplemented with 50 (P50), 100 (P100), 200 (P200), and 400 (P400) mg/kg puerarin, respectively. It was found that puerarin treatment markedly altered the serum activities of aspartate aminotransferase (AST), alanine transaminase (ALT), and superoxide dismutase (SOD), together with the malondialdehyde (MDA) and total antioxidant capacity (T-AOC) contents in the serum. The mRNA expression of IL-6, IL-1β, TNF-α, Bcl-2, and caspase-8 in the livers of S. enterica-infected chicks was increased after infection but significantly reduced after treatment with puerarin. Histologic analysis showed that puerarin effectively mitigated morphological damage in the liver caused by S. enterica. Proteomic analysis revealed that S. enterica infection led to metabolic disorders in the liver, resulting in oxidative stress, increased inflammation, and significantly elevated levels of hepatocellular carcinoma biomarkers. The findings of the filtered sequencing were verified by using quantitative PCR (qPCR). Treatment with 100 mg/mL puerarin thus effectively alleviated disordered liver metabolism, reduced inflammation and oxidative damage and significantly reduced the levels of hepatocellular carcinoma biomarkers in the liver. The results suggest that puerarin has the potential to replace antibiotics to control Salmonella infection in poultry and thus improve food safety.

IGF-1 Levels Increase during an Immune but Not an Oxidative Challenge in an Avian Model, the Japanese Quail

AbstractInsulin-like growth factor 1 (IGF-1) is positively linked with growth and reproduction but negatively linked with survival, so a potential role of IGF-1 in modulating life history trade-offs has been proposed. However, the underlying mechanisms of the negative link between IGF-1 and survival are not yet clear, and oxidative stress has been proposed as a candidate. Immune activation is one important source of oxidative stress, and both immune activation and oxidative stress are known to reduce survival. We experimentally administrated an immune or oxidative insult to Japanese quails to evaluate whether oxidative stress is a proximate cost of holding elevated IGF-1 levels during a life challenge (e.g., infection, intoxication). IGF-1 levels increased in the presence of the immune insult, but they were not affected by the oxidative insult. Hence, IGF-1 may be linked to the survival costs of activating an immune response, but oxidative stress might not be directly involved as an underlying mechanism.

The Evolution and Ecology of Oxidative and Antioxidant Status: A Comparative Approach in African Mole-Rats

The naked mole-rat of the family Bathyergidae has been the showpiece for ageing research as they contradict the traditional understanding of the oxidative stress theory of ageing. Some other bathyergids also possess increased lifespans, but there has been a remarkable lack of comparison between species within the family Bathyergidae. This study set out to investigate how plasma oxidative markers (total oxidant status (TOS), total antioxidant capacity (TAC), and the oxidative stress index (OSI)) differ between five species and three subspecies of bathyergids, differing in their maximum lifespan potential (MLSP), resting metabolic rate, aridity index (AI), and sociality. We also investigated how oxidative markers may differ between captive and wild-caught mole-rats. Our results reveal that increased TOS, TAC, and OSI are associated with increased MLSP. This pattern is more prevalent in the social-living species than the solitary-living species. We also found that oxidative variables decreased with an increasing AI and that wild-caught individuals typically have higher antioxidants. We speculate that the correlation between higher oxidative markers and MLSP is due to the hypoxia-tolerance of the mole-rats investigated. Hormesis (the biphasic response to oxidative stress promoting protection) is a likely mechanism behind the increased oxidative markers observed and promotes longevity in some members of the Bathyergidae family.

Increased male-induced harm in response to female-limited selection: interactive effects between intra- and interlocus sexual conflict?

Interlocus sexual conflict (IRSC) occurs because of shared interactions that have opposite effects on male and female fitness. Typically, it is assumed that loci involved in IRSC have sex-limited expression and are thus not directly affected by selective pressures acting on the other sex. However, if loci involved in IRSC have pleiotropic effects in the other sex, intersexual selection can shape the evolutionary dynamics of conflict escalation and resolution, as well as the evolution of reproductive traits linked to IRSC loci, and vice versa. Here we used an artificial selection approach in Japanese quail (Coturnix japonica) to test if female-limited selection on reproductive investment affects the amount of harm caused by males during mating. We found that males originating from lines selected for high female reproductive investment caused more oxidative damage in the female reproductive tract than males originating from lines selected for low female reproductive investment. This male-induced damage was specific to the oviduct and not found in other female tissues, suggesting that it was ejaculate-mediated. Our results suggest that intersexual selection shapes the evolution of IRSC and that male-induced harm may contribute to the maintenance of variation in female reproductive investment.

Biosynthesis and characterization of zinc oxide nanoparticles using Nigella sativa against coccidiosis in commercial poultry

Coccidiosis causes huge economic losses worldwide. Current study evaluated the effect of biosynthesized Zinc oxide nanoparticles (ZnONPs) using Nigella sativa, on Eimeria tenella infected broilers. Scanning electron microscopy showed spherical ZnONPs with 50-100 nm diameter, Fourier transforms infrared spectroscopy revealed the functional groups involved in the reduction of zinc acetate dihydrate to ZnONPs, UV-vis spectroscopy showed a peak at 354 nm, and Zeta potential exhibited stability at - 30 mV. A total of 150, a day-old broiler chicks were divided into 5 equal groups. Control negative: uninfected and untreated; Control positive: Infected and untreated; 3rd, 4th and 5th group were infected orally with 5 × 10⁴ sporulated oocysts of Eimeria tenella and treated with 60 mg/kg ZnONPs, 1% Nigella sativa seeds and amprolium 125 ppm, respectively. ZnONPs significantly (p < 0.05) improved the growth performance in the infected birds and decreased the oocyst shedding and anti-coccidial index. A significant (p < 0.05) decrease in the level of aspartate transferase and alanine transferase, whereas, a significantly higher amount of antioxidants like catalase and superoxide dismutase in ZnONPs treated group was observed. Pro-inflammatory cytokines like IL-2 and TNF-α were significantly decreased by ZnONPs (p < 0.05). In conclusion, biogenic ZnONPs with Nigella sativa might have enhanced anticoccidial, antioxidant, and anti-inflammatory effects with improved growth performance.

Niche theory for within-host parasite dynamics: Analogies to food web modules via feedback loops

Why do parasites exhibit a wide dynamical range within their hosts? For instance, why does infecting dose either lead to infection or immune clearance? Why do some parasites exhibit boom-bust, oscillatory dynamics? What maintains parasite diversity, that is coinfection v single infection due to exclusion or priority effects? For insights on parasite dose, dynamics and diversity governing within-host infection, we turn to niche models. An omnivory food web model (IGP) blueprints one parasite competing with immune cells for host energy (PIE). Similarly, a competition model (keystone predation, KP) mirrors a new coinfection model (2PIE). We then drew analogies between models using feedback loops. The following three points arise: first, like in IGP, parasites oscillate when longer loops through parasites, immune cells and resource regulate parasite growth. Shorter, self-limitation loops (involving resources and enemies) stabilise those oscillations. Second, IGP can produce priority effects that resemble immune clearance. But, despite comparable loop structure, PIE cannot due to constraints imposed by production of immune cells. Third, despite somewhat different loop structure, KP and 2PIE share apparent and resource competition mechanisms that produce coexistence (coinfection) or priority effects of prey or parasites. Together, this mechanistic niche framework for within-host dynamics offers new perspective to improve individual health.

Oxidative status in relation to blood parasite infections in house sparrows living along an urbanization gradient

Living organisms are exposed to a wide range of substances - internal and external - which act like reactive oxygen species (ROS). Oxidative damage accurs when the balance between ROS and antioxidant defenses is altered. Urbanization and parasite infection are both important sources of ROS with different harmful effects on wildlife health, but the potential synergies between both factors are poorly known. Here, we analyse the oxidative stress of wild juvenile male house sparrows (Passer domesticus) along an urbanization gradient in relation to the infection status by three common blood parasites (Plasmodium, Haemoproteus and Leucocytozoon) and bird body condition. We analysed samples from 688 birds captured at 45 localities from southern Spain grouped into triplets including an urban, a rural and a natural habitat, with 15 localities per habitat type. We measured i) thiobarbituric acid reactive substances (TBARS) levels as indicator of the oxidative damage to lipids, and the activity of three antioxidant enzymes ii) glutathione peroxidase (GPx), iii) superoxide dismutase (SOD) and iv) glutathione reductase (GR) as indicators of bird's antioxidant capacity. Birds infected with Haemoproteus and urban birds showed significantly and marginally higher levels of TBARS than uninfected and rural birds, respectively. The relationship between TBARS and body condition is different regarding the infection status (significative) and habitat (marginally significant) being negative for Haemoproteus infected and urban birds but positive for uninfected and non-urban birds. The antioxidant activity was significantly lower in Plasmodium infected birds but marginally higher in Leucocytozoon infected birds than in uninfected ones. Individuals with higher body condition had higher GPx and SOD activity in relation to a lower GR activity. Overall, these results suggest that blood parasites infections and urbanization affect the oxidative status of wild birds and highlight the role of bird's body condition on the regulation of the oxidative stress status.

Innate immune function and antioxidant capacity of nestlings of an African raptor covary with the level of urbanisation around breeding territories

Urban areas provide breeding habitats for many species. However, animals raised in urban environments face challenges such as altered food availability and quality, pollution and pathogen assemblages. These challenges can affect physiological processes such as immune function and antioxidant defences which are important for fitness. Here, we explore how levels of urbanisation influence innate immune function, immune response to a mimicked bacterial infection and antioxidant capacity of nestling Black Sparrowhawks Accipiter melanoleucus in South Africa. We also explore the effect of timing of breeding and rainfall on physiology since both can influence the environmental condition under which nestlings are raised. Finally, because urbanisation can influence immune function indirectly, we use path analyses to explore direct and indirect associations between urbanisation, immune function and oxidative stress. We obtained measures of innate immunity (haptoglobin, lysis, agglutination, bactericidal capacity), indices of antioxidant capacity (total non-enzymatic antioxidant capacity (tAOX) and total glutathione from nestlings from 2015 to 2019. In addition, in 2018 and 2019, we mimicked a bacterial infection by injecting nestlings with lipopolysaccharide and quantified their immune response. Increased urban cover was associated with an increase in lysis and a decrease in tAOX, but not with any of the other physiological parameters. Furthermore, except for agglutination, no physiological parameters were associated with the timing of breeding. Lysis and bactericidal capacity, however, varied consistently with the annual rainfall pattern. Immune response to a mimicked a bacterial infection decreased with urban cover but not with the timing of breeding nor rainfall. Our path analyses suggested indirect associations between urban cover and some immune indices via tAOX but not via the timing of breeding. Our results show that early-life development in an urban environment is associated with variation in immune and antioxidant functions. The direct association between urbanisation and antioxidant capacity and their impact on immune function is likely an important factor mediating the impact of urbanisation on urban-dwelling animals. Future studies should explore how these results are linked to fitness and whether the responses are adaptive for urban-dwelling species.

Maternal Responses in the Face of Infection Risk

When animals are sick, their physiology and behavior change in ways that can impact their offspring. Research is emerging showing that infection risk alone can also modify the physiology and behavior of healthy animals. If physiological responses to environments with high infection risk take place during reproduction, it is possible that they lead to maternal effects. Understanding whether and how high infection risk triggers maternal effects is important to elucidate how the impacts of infectious agents extend beyond infected individuals and how, in this way, they are even stronger evolutionary forces than already considered. Here, to evaluate the effects of infection risk on maternal responses, we exposed healthy female Japanese quail to either an immune-challenged (lipopolysaccharide [LPS] treated) mate or to a healthy (control) mate. We first assessed how females responded behaviorally to these treatments. Exposure to an immune-challenged or control male was immediately followed by exposure to a healthy male, to determine whether treatment affected paternity allocation. We predicted that females paired with immune-challenged males would avoid and show aggression towards those males, and that paternity would be skewed towards the healthy male. After mating, we collected eggs over a 5-day period. As an additional control, we collected eggs from immune-challenged females mated to healthy males. We tested eggs for fertilization status, embryo sex ratio, as well as albumen corticosterone, lysozyme activity, and ovotransferrin, and yolk antioxidant capacity. We predicted that immune-challenged females would show the strongest changes in the egg and embryo metrics, and that females exposed to immune-challenged males would show intermediate responses. Contrary to our predictions, we found no avoidance of immune-challenged males and no differences in terms of paternity allocation. Immune-challenged females laid fewer eggs, with an almost bimodal distribution of sex ratio for embryos. In this group, albumen ovotransferrin was the lowest, and yolk antioxidant capacity decreased over time, while it increased in the other treatments. No differences in albumen lysozyme were found. Both females that were immune-challenged and those exposed to immune-challenged males deposited progressively more corticosterone in their eggs over time, a pattern opposed to that shown by females exposed to control males. Our results suggest that egg-laying Japanese quail may be able to respond to infection risk, but that additional or prolonged sickness symptoms may be needed for more extensive maternal responses.

Research Note: Oxidative stress and immune response following the administration of live attenuated Mycoplasma gallisepticum vaccination in backyard chicken

In the present study, we investigated a possible relationship between the immune response and the oxidative stress (OS) state trend in a group of 12 chickens after intraocular administration of an attenuated Mycoplasma gallisepticum (MG) vaccine. Blood samples were collected at the vaccination time (T0), after 14 (T1) and 21 d (T2). White blood cell count (WBC), differential leucocyte count, and anti-MG antibodies titer (S/P) were studied as immune response indexes. As plasmatic OS biomarkers levels, we considered malondialdehyde (MDA), nitric oxide (NO), superoxide dismutase (SOD), reactive oxygen metabolites derived compounds (d-ROMs), the ferric reducing ability of plasma (FRAP), and superoxide anion (O₂^-). After antigenic stimulation, it was observed a significant decrease in monocythemia and a significant increase in thrombocythemia, S/P, MDA, and SOD. Furthermore, subjects with high d-ROMs levels at T0 tended to develop higher cellular mobilization with increases in WBC and lymphocytes accompanied by lower antibody release. It was also observed that the antioxidant components FRAP and SOD were moderately positively correlated to the entity of antibody response.

Measurements of body temperature and oxidative stress reveal differential costs associated with humoral immune function in a passerine bird

Eco-immunology considers resistance to antigens a costly trait for an organism, but actual quantification of such costs is not straightforward. Costs of the immune response are visible in impaired coloration and reduced growth or reproductive success. Activation of the humoral immune response is a slow, complex and long-lasting process, which makes the quantification of its energetic cost a potential losing game. We implemented near-continuous measurements of body temperature in zebra finches (Taeniopygia guttata) as a proxy for the energetic cost, with a particular focus during activation of the humoral immune response until the peak of antibody release several days later. At the peak of the antibody release we additionally measured oxygen consumption (open-flow respirometry) and markers of oxidative stress (dROMs, OXY). Birds with an activated immune response maintained a higher night-time body temperature during the first 4 nights after an immune challenge in comparison to controls, implying increased night-time energy use. At peak antibody production, we did not find differences in night-time body temperature and oxygen consumption but observed differentiated results for oxygen consumption during the day. Immune-challenged females had significantly higher oxygen consumption compared with other groups. Moreover, we found that activation of the humoral immune response increases oxidative damage, a potential cost of maintaining the higher night-time body temperature that is crucial at the early stage of the immune response. The costs generated by the immune system appear to consist of two components - energetic and non-energetic - and these appear to be separated in time.

Novel strategies to improve chicken performance and welfare by unveiling host-microbiota interactions through hologenomics

Fast optimisation of farming practices is essential to meet environmental sustainability challenges. Hologenomics, the joint study of the genomic features of animals and the microbial communities associated with them, opens new avenues to obtain in-depth knowledge on how host-microbiota interactions affect animal performance and welfare, and in doing so, improve the quality and sustainability of animal production. Here, we introduce the animal trials conducted with broiler chickens in the H2020 project HoloFood, and our strategy to implement hologenomic analyses in light of the initial results, which despite yielding negligible effects of tested feed additives, provide relevant information to understand how host genomic features, microbiota development dynamics and host-microbiota interactions shape animal welfare and performance. We report the most relevant results, propose hypotheses to explain the observed patterns, and outline how these questions will be addressed through the generation and analysis of animal-microbiota multi-omic data during the HoloFood project.

Long Bone Mineral Loss, Bone Microstructural Changes and Oxidative Stress After Eimeria Challenge in Broilers

The objective of this study was to evaluate the impact of coccidiosis on bone quality and antioxidant status in the liver and bone marrow of broiler chickens. A total of 360 13-day old male broilers (Cobb 500) were randomly assigned to different groups (negative control, low, medium-low, medium-high, and highest dose groups) and orally gavaged with different concentrations of Eimeria oocysts solution. Broiler tibia and tibia bone marrow were collected at 6 days post-infection (6 dpi) for bone 3-D structural analyses and the gene expression related to osteogenesis, oxidative stress, and adipogenesis using micro-computed tomography (micro-CT) and real-time qPCR analysis, respectively. Metaphyseal bone mineral density and content were reduced in response to the increase of Eimeria challenge dose, and poor trabecular bone traits were observed in the high inoculation group. However, there were no significant structural changes in metaphyseal cortical bone. Medium-high Eimeria challenge dose significantly increased level of peroxisome proliferator-activated receptor gamma (PPARG, p < 0.05) and decreased levels of bone gamma-carboxyglutamate protein coding gene (BGLAP, p < 0.05) and fatty acid synthase coding gene (FASN, p < 0.05) in bone marrow. An increased mRNA level of superoxide dismutase type 1 (SOD1, p < 0.05) and heme oxygenase 1 (HMOX1, p < 0.05), and increased enzyme activity of superoxide dismutase (SOD, p < 0.05) were found in bone marrow of Eimeria challenged groups compared with that of non-infected control. Similarly, enzyme activity of SOD and the mRNA level of SOD1, HMOX1 and aflatoxin aldehyde reductase (AKE7A2) were increased in the liver of infected broilers (p < 0.05), whereas glutathione (GSH) content was lower in the medium-high challenge group (p < 0.05) compared with non-challenged control. Moreover, the mRNA expression of catalase (CAT) and nuclear factor kappa B1 (NFKB1) showed dose-depend response in the liver, where expression of CAT and NFKB1 was upregulated in the low challenge group but decreased with the higher Eimeria challenge dosage (p < 0.05). In conclusion, high challenge dose of Eimeria infection negatively affected the long bone development. The structural changes of tibia and decreased mineral content were mainly located at the trabecular bone of metaphyseal area. The change of redox and impaired antioxidant status following the Eimeria infection were observed in the liver and bone marrow of broilers.

A meta-analysis of impacts of immune response and infection on oxidative status in vertebrates

Inferring from patterns observed in biomedical research, ecoimmunological theory predicts that oxidative stress is a ubiquitous physiological cost that contributes to generating variation in immune function between individuals or species. This prediction is, however, often challenged by empirical studies testing the relationship between immune response or infection and oxidative status markers. This points out the importance of combining ecological immunology and oxidative stress ecology to further our understanding of the proximate causes and fitness consequences of individual variation in health, and adaptability to natural and anthropogenic environmental changes. I reviewed evidence and performed phylogenetic meta-analyses of changes in oxidative status markers owing to either injection of an antigen or infection in captive and free-living vertebrates (141 studies, 1262 effect sizes, 97 species). The dataset was dominated by studies on fish, birds and mammals, which provided 95.8% of effect sizes. Both antigen injection and parasite exposure were associated with changes of oxidative status. There were significant effects of taxonomic class and experimental environment (captivity vs. wild). In contrast with my predictions, age category (young vs. adult), study design (correlational vs. experimental) and proxies of pace of life (clutch size, litter size, and body mass; for birds and mammals only) were negligible in this dataset. Several methodological aspects (type of immunostimulant, laboratory assay, tissue analysed) showed significant effects on both strength and direction of effect. My results suggest that alterations of oxidative status are a widespread consequence of immune function across vertebrates. However, this work also identified heterogeneity in strength and direction of effect sizes, which suggests that immune function does not necessarily result in oxidative stress. Finally, this work identifies methodological caveats that might be relevant for the interpretation and comparability of results and for the application in conservation programs.

Metabolomic profiles in relation to benchmark polycyclic aromatic compounds (PACs) and trace elements in two seabird species from Arctic Canada

While exposure of birds to oil-related contaminants has been documented, the related adverse effects this exposure has on Arctic marine birds remain unexplored. Metabolomics can play an important role to explore biologically relevant metabolite biomarkers in relation to different stressors, even at benchmark levels of contamination. The aim of this study was to characterize the metabolomics profiles in relation to polycyclic aromatic compounds (PACs) and trace elements in the liver of two seabird species in the Canadian Arctic. In July 2018, black guillemots (Cepphus grylle) and thick-billed murres (Uria lomvia) were collected by hunters from a region where natural oil seeps occur in the seabed near Qikiqtarjuaq, Nunavut, Canada. A total of 121 metabolites were identified in liver tissue samples using reversed phase and hydrophilic interaction liquid chromatography coupled to high resolution mass spectrometry platforms to detect non-polar and polar metabolites, respectively. Sixty-nine metabolites showed excellent repeatability and linearity and were used to examine possible effects of oil-related contaminants exposure (PACs and trace elements). Metabolites including 3-hydroxy anthranilic acid, adenine, adenosine, adenosine mono-phosphate, ascorbic acid, butyrylcarnitine, cholic acid, guanosine, guanosine mono-phosphate, inosine, norepinephrine and threonine showed significant differences (more than two fold) between the two species. Elevated adenine and adenosine, along with decreased reduced/oxidized glutathione ratio, highlighted the potential for oxidative stress in murres. Lipid peroxidation and superoxide dismutase activity assays also confirmed these metabolomic findings. These results will help to characterize the baseline metabolomic profiles of Arctic seabird species with different foraging behaviour and trace element burden.

Avian Malaria in Penguins: Diagnostics and Future Direction in the Context of Climate Change

Simple Summary

Avian malaria is caused by infection with protozoa of the genus Plasmodium. This vector-borne parasite is spread by mosquitoes and has a variable significance depending on environmental, host, mosquito and parasite factors. Captive penguins in non-native environments are exposed to the protozoa without having coevolved with them and are especially sensitive to infection. The most common presentation of the disease in affected penguins is acute death. Infection of wild penguins is reported and a greater understanding of the significance of such infections is required. Global warming and related surges in vector availability present an increasing threat to conservation in captive environments and targeted research into the early diagnosis of disease is required. Current diagnostic methods predominantly rely upon direct microscopy and/or molecular testing on tissues obtained from penguin postmortem examinations, and frequently fail to identify the causative agent at a species level. There are several barriers to the development of a rapid method to detect infection and the causative species; however, this information would further our understanding of this disease, and development of such a method is a valuable undertaking. This paper provides a summary of current diagnostic methods, identifies the likely future impacts of avian malaria in penguins, and highlights the need to improve both the speed and scope of available diagnostics.

Abstract

Avian malaria is caused by infection with haemoprotozoa of the genus Plasmodium. Infection is endemic in large parts of the world and is typically subclinical in birds that are native to these regions. Several penguin species have evolved in non-endemic regions without the selective pressure that these parasites exert and are highly susceptible to infection when transplanted to endemic regions, for example, in the context of zoological collections or rehabilitation centers. Avian malaria in penguins typically causes acute mortality without premonitory signs, or less commonly, nonspecific signs of morbidity, followed by mortality. Additionally, infection is reported in wild penguins, though the significance of these infections remains equivocal. As global temperatures continue to increase, avian malaria is likely to pose a continued and further threat to conservation efforts in captive environments. Intra vitam diagnosis currently relies on the evaluation of blood smears and molecular methods. The former is unreliable in penguins, as the acute clinical course typically does not allow the development of parasitemia. This absence of parasitemia also makes speciation challenging. Current molecular methods typically target the Cytochrome B or 18s subunit and have proven variably sensitive and specific. Reliable intra vitam diagnosis of avian malaria and further information about the causative agents at a species level would be very valuable in understanding the epidemiology and likely future course of avian malaria infection in penguins, and in particular, the implications avian malaria may have for conservation efforts. This paper provides an overview of malaria in penguins, discusses its changing impact on management and conservation, offers a summary of current diagnostics, and suggests future direction for the development of diagnostic tests. The latter will be key in understanding and managing this disease.

Use of Zinc Oxide Nanoparticles as Anticoccidial Agents in Broiler Chickens along with Its Impact on Growth Performance, Antioxidant Status and Hematobiochemical Profile

The impact of zinc oxide nanoparticles (ZnO-NPs) on the pathogenesis of coccidiosis in broiler chickens was tested. A total of 160 1-day-old broiler chicks (Ross 308) were randomly allocated into 4 groups (n = 40). Group 1: unchallenged, unmedicated; Group 2: challenged, unmedicated; Group 3: challenged, supplemented with diclazuril (1 ppm); Group 4: challenged, supplemented with ZnO-NPs (20 ppm). Mixed Eimeria species (E. maxima, E. acervulina, E. mivati, and E. tenella) of a commercial coccidial vaccine (FORTEGRA®) were used to perform the coccidial challenge by 15× of its vaccinal dose on the 14th day of age. Diclazuril and ZnO-NPs supplementation in Group 3 and 4, respectively, reduced the mortality rate due to coccidial challenge to 5.8% compared to 11.9% in Group 2. The growth performance was improved by ZnO-NPs in coccidiosis-infected group (p ≤ 0.05) compared to Group 2 and was comparable to that of Group 3 (p ≥ 0.05). The average oocyst count was lower in Groups 3 and 4 (7.8 × 103 and 14.3 × 103, respectively) than in Group 2 (67 × 103 oocysts). Group 3 had a decreased gross lesion score in duodenum and caecum (p ≤ 0.05) as well as jujenum and ileum (p ≥ 0.05) compared to Group 2; while the average lesion scores of all intestinal parts in Group 4 were significantly decreased (p ≤ 0.05). However, diclazuril was superior to ZnO-NPs in reducing caecal lesion score (p ≤ 0.05). Plasma carotenoids levels were increased by diclazuril (p ≥ 0.05) and ZnO-NPs (p ≤ 0.05) supplementation compared to Group 2. Oxidative stress appeared on the fourth week post-challenge (pc) in Group 2 (p ≤ 0.05) compared to Group 1, while the dietary supplementation with either diclazuril or ZnO-NPs numerically decreased Malondialdhyde (p ≥ 0.05) and statistically increased antioxidant activity (p ≤ 0.05). Both medications significantly improved the PCV%, Hb% and RBCs count on the 6th-day and 4th-week pc (p ≤ 0.05) compared to Group 2, though this improvement was higher significantly in Group 4 than Group 3 on the 6th day pc (p ≤ 0.05). Neither coccidial challenge nor medications had an impact on the total WBCs count as well as organ index, except Bursa of fabricious index that significantly improved by ZnO-NPs on the 4th-week pc compared to Group 2. Coccidial challenge reduced total protein and globulin levels and increased the serum alanine aminotransferase, serum cholesterol, and low-density lipoprotein levels (p ≤ 0.05) compared to Group 1, while those of both medicated groups (Group 3 and 4) were comparable to Group 1 (p ≥ 0.05). In conclusion, ZnO-NPs were found to be as effective as diclazuril against coccidiosis. However, further research is needed to fully comprehend its anticoccidial mechanisms.

Androgen Elevation Accelerates Reproductive Senescence in Three-Spined Stickleback

Costs of reproduction shape the life-history evolution of investment in current and future reproduction and thereby aging. Androgens have been proposed to regulate the physiology governing these investments. Furthermore, androgens are hypothesized to play a central role in carotenoid-dependent sexual signaling, regulating how much carotenoids are diverted to ornamentation and away from somatic maintenance, increasing oxidative stress, and accelerating aging. We investigated these relationships in male three-spined stickleback in which we elevated 11-ketotestosterone and supplied vitamin E, an antioxidant, in a 2 × 2 design. Androgen elevation shortened the time stickleback maintained reproductive activities. We suspect that this effect is caused by 11-ketotestosterone stimulating investment in current reproduction, but we detected no evidence for this in our measurements of reproductive effort: nest building, body composition, and breeding coloration. Carotenoid-dependent coloration was even slightly decreased by 11-ketotestosterone elevation and was left unaffected by vitamin E. Red coloration correlated with life expectancy and reproductive capacity in a quadratic manner, suggesting overinvestment of the individuals exhibiting the reddest bellies. In contrast, blue iris color showed a negative relationship with survival, suggesting physiological costs of producing this aspect of nuptial coloration. In conclusion, our results support the hypothesis that androgens regulate investment in current versus future reproduction, yet the precise mechanisms remain elusive. The quadratic relationships between sexual signal expression and aspects of quality have wider consequences for how we view sexual selection on ornamentation and its relationship with aging.

Induced bacterial sickness causes inflammation but not blood oxidative stress in Egyptian fruit bats (Rousettus aegyptiacus)

Bats are particularly interesting vertebrates in their response to pathogens owing to extremes in terms of tolerance and resistance. Oxidation is often a by-product of processes involved in the acute phase response, which may result in antimicrobial or self-damaging effects. We measured the immunological and oxidative status responses of Egyptian fruit bats (Rousettus aegyptiacus) to a simulated bacterial infection using lipopolysaccharide injection. As expected, experimental bats exhibited increases in two humoral immunological markers. However, they surprisingly did not show any effects across two markers of oxidative damage and four antioxidant markers. We propose that this lack of effects on oxidative status may be due to a reduction in cell metabolism through sickness behaviours or given life history traits, such as a long lifespan and a frugivorous diet. Finally, the consistency in the pattern of elevation in haptoglobin and lysozyme between current and previous findings highlights their utility as diagnostic markers for extracellular infections in bats.

An Overview on How Exercise with Green Tea Consumption Can Prevent the Production of Reactive Oxygen Species and Improve Sports Performance

Free radicals are reactive products that have multiple effects on the human body. Endogenous and exogenous antioxidants manage the overproduction of free radicals. However, an imbalance between free radicals and antioxidant factors causes oxidative stress. Exercise and physical activity are factors that increase oxidative stress and disrupts the body’s homeostasis. Intensity and duration of training, training characteristics, and fitness level can have positive or negative effects on oxidative stress. Green tea consumption is recommended for the prevention of a variety of diseases, health maintenance, and weight loss. The effectiveness of green tea is primarily due to the presence of catechins and polyphenols, specifically (–)-epigallocatechin-3-gallate, which has antioxidant and anti-inflammatory properties based on clinical and animal studies. This review investigates the effect of green tea exercise and their interactive effects on free radicals and sports improvement.

Longitudinal evidence for immunosenescence and inflammaging in free-living great tits

The first-line effector mechanisms of immune defence, including inflammation and oxidative burst, contribute significantly to host-pathogen resistance. Whether these immune responses undergo age-related changes in birds remains unknown. Here, we tracked selected inflammatory parameters in 54 free-living great tits (Parus major) of known age, captured repeatedly over three consecutive years, with the aims to investigate long-term repeatability and age-dependent changes in cellular oxidative burst responsiveness upon in vitro stimulation with bacterial lipopolysaccharide (LPS), and to identify its relationships with leukotriene B4 (LTB4) levels and haematological traits. In addition, we linked these immunological traits to selected physiological markers (antioxidants and oxidative stress markers). LTB4 levels increased with age and we have shown a similar non-significant tendency also for absolute granulocyte counts, indicating propagating chronic inflammation over the bird's lifetime, consistent with the inflammaging hypothesis. In contrast, cellular oxidative burst followed a quadratic trend of dependency on age with a peak in midlife individuals, in line with the immunosenescence hypothesis. Interestingly, LTB4 levels were positively associated with general oxidative damage, but negatively with antioxidant glutathione peroxidase activity, indicating links to redox balance. This longitudinal study demonstrates the contrasting patterns of age-related changes in background and acute markers of pro-inflammatory immunity contributing to immunosenescence in birds and thus provides basis for interpretation of the tested inflammatory markers in cross-cohort datasets.

Reduced ectoparasite load, body mass and blood haemolysis in Eurasian kestrels (Falco tinnunculus) along an urban-rural gradient

Urbanisation is proceeding at an alarming rate which forces wildlife to either retreat from urban areas or cope with novel stressors linked to human presence and activities. For example, urban stressors like anthropogenic noise, artificial light at night and chemical pollution can have severe impacts on the physiology of wildlife (and humans), in particular the immune system and antioxidant defences. These physiological systems are important to combat and reduce the severity of parasitic infections, which are common among wild animals. One question that then arises is whether urban-dwelling animals, whose immune and antioxidant system are already challenged by the urban stressors, are more susceptible to parasitic infections. To assess this, we studied nestlings of Eurasian kestrels (Falco tinnunculus) in Vienna, Austria, during 2015 and 2017. We measured biomarkers of innate immune function, oxidative stress and body mass index and ectoparasite infection intensity in 143 nestlings (from 56 nests) along an urban gradient. Nestlings in more urbanised areas had overall fewer ectoparasites, lower haemolysis (complement activity) and lower body mass index compared to nestlings in less urbanised areas. None of the other immune or oxidative stress markers were associated with the urban gradient. Despite some non-significant results, our data still suggest that kestrel nestlings experience some level of reduced physiological health, perhaps as a consequence of exposure to more urban stressors or altered prey availability in inner-city districts even though they had an overall lower ectoparasite burden in these heavily urbanised areas.

Energy expenditure across immune challenge severities in a lizard: consequences for innate immunity, locomotor performance and oxidative status

Reptiles, like other vertebrates, rely on immunity to defend themselves from infection. The energetic cost of an immune response is liable to scale with infection severity, prompting constraints on other self-maintenance traits if immune prioritization exceeds energy budget. In this study, adult male side-blotched lizards (Uta stansburiana) were injected with saline (control) or high (20 µg g-1 body mass) or low (10 µg g-1 body mass) concentrations of lipopolysaccharide (LPS) to simulate bacterial infections of discrete severities. The costs and consequences of the immune response were assessed through comparisons of change in resting metabolic rate (RMR), energy metabolites (glucose, glycerol, triglycerides), innate immunity (bactericidal ability), sprint speed and oxidative status (antioxidant capacity, reactive oxygen metabolites). High-LPS lizards had the lowest glucose levels and greatest sprint reductions, while their RMR and bactericidal ability were similar to those of control lizards. Low-LPS lizards had elevated RMR and bactericidal ability, but glucose levels and sprint speed changes between those of high-LPS and control lizards. Levels of glycerol, triglycerides, reactive oxygen metabolites and antioxidant capacity did not differ by treatment. Taken together, energy expenditure for the immune response varies in a non-linear fashion with challenge severity, posing consequences for performance and self-maintenance processes in a reptile.

Ectoparasite Load Is Reduced in Side-Blotched Lizards (Uta stansburiana) at Wind Farms: Implications for Oxidative Stress

AbstractWind-generated power is one of the fastest growing alternative energy strategies worldwide and will likely account for 20% of US energy production by 2030. The installation and maintenance of wind farms are associated with increased human activity and can generate noise pollution, disturb and fragment habitat, and even alter community composition and structure. These environmental and ecological changes can increase physiological stress for vertebrates and affect important life-history attributes, such as immune function. However, little is known about how wind farms influence physiology and disease or parasite resistance in nonvolant wildlife. Here, we test the notion that renewable wind farms increase physiological stress and correlated aspects of disease resistance (parasite load) in a common desert vertebrate, the side-blotched lizard (Uta stansburiana). We captured lizards from three wind farms and three undisturbed reference sites in the San Gorgonio Pass wind resource area in the Mojave Desert, California. We quantified individual external parasite loads and measured plasma antioxidant capacity and concentrations of reactive oxygen metabolites as a combined metric of oxidative stress. Contrary to our expectations, individuals at wind farm sites had significantly fewer external parasites than at undeveloped sites. Additionally, we found a slight positive correlation between parasite load and oxidative stress for individuals at wind farm sites but not at reference sites. Our results demonstrate a complex, potentially context-dependent relationship between stress physiology and disease resistance for lizards in anthropogenically disturbed environments. Understanding how wind farms affect the physiology and ecoimmunology of terrestrial fauna is necessary to mitigate the ecological costs of alternative energy development.

Determinants of defence strategies of a hibernating European bat species towards the fungal pathogen Pseudogymnoascus destructans

Pseudogymnoascus destructans (Pd), the causative agent of white-nose syndrome in North America, has decimated bat populations within a decade. The fungus impacts bats during hibernation when physiological functions, including immune responses, are down-regulated. Studies have shown that Pd is native to Europe, where it is not associated with mass mortalities. Moreover, genomic and proteomic studies indicated that European bats may have evolved an effective immune defence, which is lacking in North American bats. However, it is still unclear which defence strategy enables European bats to cope with the pathogen. Here, we analyzed selected physiological and immunological parameters in torpid, Pd infected European greater mouse-eared bats (Myotis myotis) showing three different levels of infection (asymptomatic, mild and severe symptoms). From a subset of the studied bats we tracked skin temperatures during one month of hibernation. Contrasting North American bats, arousal patterns remained unaffected by Pd infections in M. myotis. In general, heavier M. myotis aroused more often from hibernation and showed less severe disease symptoms than lean individuals; most likely because heavy bats were capable of reducing the Pd load more effectively than lean individuals. In the blood of severely infected bats, we found higher gene expression levels of an inflammatory cytokine (IL-1β), but lower levels of an acute phase protein (haptoglobin), reactive oxygen metabolites (ROMs) and plasma non-enzymatic antioxidant capacity (OXY) compared to conspecifics with lower levels of infection. We conclude that M. myotis, and possibly also other European bat species, tolerate Pd infections during torpor by using selected acute phase response parameters at baseline levels, yet without arousing from torpor and without synthesizing additional immune molecules.

Parental morph combination does not influence innate immune function in nestlings of a colour-polymorphic African raptor

Conditions experienced during early life can have long-term individual consequences by influencing dispersal, survival, recruitment and productivity. Resource allocation during development can have strong carry-over effects onto these key parameters and is directly determined by the quality of parental care. In the black sparrowhawk (Accipiter melanoleucus), a colour-polymorphic raptor, parental morphs influence nestling somatic growth and survival, with pairs consisting of different colour morphs ('mixed-morph pairs') producing offspring with lower body mass indices, but higher local apparent survival rates. Resource allocation theory could explain this relationship, with nestlings of mixed-morph pairs trading off a more effective innate immune system against somatic growth. We quantified several innate immune parameters of nestlings (hemagglutination, hemolysis, bacteria-killing capacity and haptoglobin concentration) and triggered an immune response by injecting lipopolysaccharides. Although we found that nestlings with lower body mass index had higher local survival rates, we found no support for the proposed hypothesis: neither baseline immune function nor the induced immune response of nestlings was associated with parental morph combination. Our results suggest that these immune parameters are unlikely to be involved in providing a selective advantage for the different colour morphs' offspring, and thus innate immunity does not appear to be traded off against a greater allocation of resources to somatic growth. Alternative hypotheses explaining the mechanism of a low nestling body mass index leading to subsequent higher local survival could be related to the post-fledgling dependency period or differences in dispersal patterns for the offspring from different morph combinations.

Oxidative status of blue tit nestlings varies with habitat and nestling size

Oxidative status has been proposed as an important ecological and evolutionary force given that pro-oxidant metabolites damage molecules, cells and tissues, with fitness consequences for organisms. Consequently, organisms usually face a trade-off between regulating their oxidative status and other physiological traits. However, environmental stressors and the availability of dietary-derived antioxidants vary according to local conditions and, thus, organisms inhabiting different habitats face different oxidative pressures. Still, there is little information on how different environmental conditions influence the oxidative status of animals inhabiting terrestrial environments. In this work, we examined the variation in oxidative status in the blue tit (Cyanistes caeruleus), a bird species with hatching asynchrony. Specifically, we examined the oxidative status of the largest and the smallest nestlings in the brood, inhabiting four forests differing in food availability and ectoparasite prevalence. We measured lipid peroxidation (malondialdehyde; MDA) as a marker of oxidative damage, total antioxidant capacity (Trolox-equivalent antioxidant capacity; TEAC) and antioxidant enzymatic activity (catalase, glutathione S-transferase, glutathione peroxidase) in blood samples. The glutathione peroxidase (GPX) activity differed among the forests, being the highest in the pine forest and the lowest in a mixed oak (Quercus) forest in the most humid area. Lipid peroxidation was higher in larger nestlings, suggesting higher oxidative damage with an increasing growth rate. Neither brood size, laying date, nor ectoparasites were related to the oxidative status of nestlings. These results suggest that nest rearing conditions might shape the oxidative status of birds, having consequences for habitat-dependent variation in regulation of oxidative status.

Exposure to artificial light at night alters innate immune response in wild great tit nestlings

The large-scale impact of urbanization on wildlife is rather well documented; however, the mechanisms underlying the effects of urban environments on animal physiology and behaviour are still poorly understood. Here, we focused on one major urban pollutant - artificial light at night (ALAN) - and its effects on the capacity to mount an innate immune response in wild great tit (Parus major) nestlings. Exposure to ALAN alters circadian rhythms of physiological processes, by disrupting the nocturnal production of the hormone melatonin. Nestlings were exposed to a light source emitting 3 lx for seven consecutive nights. Subsequently, nestlings were immune challenged with a lipopolysaccharide injection, and we measured haptoglobin and nitric oxide levels pre- and post-injection. Both haptoglobin and nitric oxide are important markers for innate immune function. We found that ALAN exposure altered the innate immune response, with nestlings exposed to ALAN having lower haptoglobin and higher nitric oxide levels after the immune challenge compared with dark-night nestlings. Unexpectedly, nitric oxide levels were overall lower after the immune challenge than before. These effects were probably mediated by melatonin, as ALAN-treated birds had on average 49% lower melatonin levels than the dark-night birds. ALAN exposure did not have any clear effects on nestling growth. This study provides a potential physiological mechanism underlying the documented differences in immune function between urban and rural birds observed in other studies. Moreover, it gives evidence that ALAN exposure affects nestling physiology, potentially causing long-term effects on physiology and behaviour, which ultimately can affect their fitness.

Recovery from discrete wound severities in side-blotched lizards (Uta stansburiana): implications for energy budget, locomotor performance, and oxidative stress

Wounding events (predation attempts, competitive combat) result in injuries and/or infections that induce integrated immune responses for the recovery process. Despite the survival benefits of immunity in this context, the costs incurred may require investment to be diverted from traits contributing to immediate and/or future survival, such as locomotor performance and oxidative status. Yet, whether trait constraints manifest likely depends on wound severity and the implications for energy budget. For this study, food intake, body mass, sprint speed, and oxidative indices (reactive oxygen metabolites, antioxidant capacity) were monitored in male side-blotched lizards (Uta stansburiana) healing from cutaneous wounds of discrete sizes (control, small, large). Results indicate that larger wounds induced faster healing, reduced food consumption, and led to greater oxidative stress over time. Granted wounding did not differentially affect body mass or sprint speed overall, small-wounded lizards with greater wound area healed had faster sprint speeds while large-wounded lizards with greater wound area healed had slower sprint speeds. During recovery from either wound severity, however, healing and sprint performance did not correspond with food consumption, body mass loss, nor oxidative status. These findings provide support that energy budget, locomotor performance, and oxidative status of a reptile are linked to wound recovery to an extent, albeit dependent on wound severity.

Intraspecific variability of responses to combined metal contamination and immune challenge among wild fish populations

Wild organisms are increasingly exposed to multiple anthropogenic and natural stressors that can interact in complex ways and lead to unexpected effects. In aquatic ecosystems, contamination by trace metals has deleterious effects on fish health and commonly co-occurs with pathogens, which affect similar physiological and behavioral traits. However, the combined effects of metal contamination and parasitism are still poorly known. In addition, the sensitivity to multiple stressors could be highly variable among different fish populations depending on their evolutionary history, but this intraspecific variability is rarely taken into account in existing ecotoxicological studies. Here, we investigated i) the interactive effects of metal contamination (i.e., realistic mixture of Cd, Cu and Zn) and immune challenge mimicking a parasite attack on fish health across biological levels. In addition, we compared ii) the physiological and behavioral responses among five populations of gudgeon fish (Gobio occitaniae) having evolved along a gradient of metal contamination. Results show that single stressors exposure resulted in an increase of immune defenses and oxidative stress at the expense of body mass (contamination) or fish swimming activity (immune challenge). Multiple stressors had fewer interactive effects than expected, especially on physiological traits, but mainly resulted in antagonistic effects on fish swimming activity. Indeed, the immune challenge modified or inhibited the effects of contamination on fish behavior in most populations, suggesting that multiple stressors could reduce behavioral plasticity. Interestingly, the effects of stressors were highly variable among populations, with lower deleterious effects of metal contamination in populations from highly contaminated environments, although the underlying evolutionary mechanisms remain to be investigated. This study highlights the importance of considering multiple stressors effects and intraspecific variability of sensitivity to refine our ability to predict the effects of environmental contaminants on aquatic wildlife.

Effects of a Bacterial Infection on Mitochondrial Function and Oxidative Stress in a Songbird

AbstractAs a major physiological mechanism involved in cellular renewal and repair, immune function is vital to the body's capacity to support tissue maintenance and organismal survival. Because immune defenses can be energetically expensive, the activities of metabolically active organs, such as the liver, are predicted to increase during infection by most pathogens. However, some pathogens are immunosuppressive, which might reduce the metabolic capacities of select organs to suppress immune response. Mycoplasma gallisepticum (MG) is a well-known immunosuppressive bacterium that infects domestic chickens and turkeys as well as songbirds. In the house finch (Haemorhous mexicanus), which is the primary host for MG among songbird species, MG infects both the respiratory system and the conjunctiva of the eye, causing conspicuous swelling. To study the effect of a systemic bacterial infection on cellular respiration and oxidative damage in the house finch, we measured mitochondrial respiration, mitochondrial membrane potential, reactive oxygen species production, and oxidative damage in the livers of house finches that were wild caught and either infected with MG, as indicated by genetic screening for the pathogen, or free of MG infection. We observed that MG-infected house finches showed significantly lower oxidative lipid and protein damage in liver tissue compared with their uninfected counterparts. Moreover, using complex II substrates, we documented a nonsignificant trend for lower state 3 respiration of liver mitochondria in MG-infected house finches compared with uninfected house finches (P=0.07). These results are consistent with the hypothesis that MG suppresses organ function in susceptible hosts.

Dietary taurine supplementation attenuates lipopolysaccharide-induced inflammatory responses and oxidative stress of broiler chickens at an early age

This study was conducted to investigate the effect of taurine as a prophylactic treatment on antioxidant function and inflammatory responses of broilers challenged with lipopolysaccharide (LPS). A total of 256 one-day-old male Arbor Acres broiler chicks were randomly assigned to four treatments with eight replicates of eight birds (eight birds per cage). Four treatment groups were designated as follows: 1) in the CON group, broilers fed a basal diet; 2) in the LPS group, LPS-challenged broilers fed a basal diet; 3) in the LPS + T1 group, LPS-challenged broilers fed a basal diet supplemented with 5.0 g/kg taurine; and 4) in the LPS + T2 group, LPS-challenged broilers fed a basal diet supplemented with 7.5 g/kg taurine. The LPS-challenged broilers were intraperitoneally injected with 1 mg/kg body weight (BW) of LPS at 16, 18, and 20 d of age, whereas the CON group received an injection of sterile saline. The results showed that broilers injected with LPS exhibited decreased (P < 0.05) the average daily gain (ADG) and the 21-d BW (P < 0.05), while taurine supplementation alleviated the negative effects of LPS. Additionally, the LPS-induced increases (P < 0.05) in serum alanine transaminase and aspartate transaminase activities were reversed by taurine supplementation. The taurines could alleviate the hepatic oxidative stress, with the presence of lower content of malondialdehyde (P < 0.05), higher content of glutathione (P < 0.05), and an increased glutathione peroxidase (GSH-Px) activity (P < 0.05). The concentrations of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in the liver were measured by ELISA kits, and the result showed that dietary taurine supplementation prevented these cytokines increases in the liver of LPS-induced broilers. Taurine reduced the genes expression of IL-1β, TNF-α, IL-6, cyclooxygenase-2, and inducible nitric oxide synthase, whereas it boosted the expression levels of antioxidant-related genes (nuclear factor erythroid 2-related factor 2, heme oxygenase-1, glutamate-cysteine ligase catalytic subunit, and GSH-Px) in the liver of LPS-induced broilers. In conclusion, dietary taurine supplementation in broilers mitigated LPS-induced defects in ADG, oxidative stress, and inflammatory responses.

Synergetic effects of immune challenge and stress depress cortisol, inflammatory response and antioxidant activity in fish-eating Myotis

One of the most common tools in conservation physiology is the assessment of environmental stress via glucocorticoid measurement. However, little is known of its relationship with other stress-related biomarkers, and how the incidence of an immune challenge during long-term stress could affect an individual's overall stress response. We investigated here the relationship between basal and post-acute stress fecal cortisol metabolite (FC) with different antioxidant enzymes, oxidative damage and immune parameters in the fish-eating bat, Myotis vivesi We found that in both basal and post-stress conditions, FC was highly related with a number of antioxidant enzymes and immune parameters, but not to oxidative damage. We also assessed changes of FC through the seasons. Basal FC samples and stress reactivity after short-duration stress displayed similar levels during summer, autumn and early winter, but lower concentrations in late winter. Stress reactivity after long-duration stress was greater in summer and early winter. Finally, we tested the effect of a simultaneous exposure to a long, strong stress stimulus with an immune response stimulation by administrating adrenocorticotropic hormone (ACTH) and phytohemagglutinin (PHA) after 42 h. Results showed that when both stimuli were administrated, FC concentrations, inflammation and some antioxidant activity were lowered in comparison with the control and individual administration of the challenges. Our findings support the idea that animals maintain constant basal glucocorticoid levels when living in challenging environments, but response to acute stress differs seasonally and immune defense mechanisms and stress responses might be compromised when confronted with multiple challenges.

Sex-specific effects of experimental ectoparasite infestation on telomere length in great tit nestlings

Telomere length is a biomarker of biological ageing and lifespan in various vertebrate taxa. Evidence is accumulating that telomeres shorten more rapidly when an individual is exposed to environmental stressors. Parasites are potent selective agents that can cause physiological stress directly or indirectly through the activation of the host's immune system. Yet to date, empirical evidence for a role of parasites in telomere dynamics in natural populations is limited. Here, we show experimentally that exposure to ectoparasitic hen fleas (Ceratophyllus gallinae) during growth results in shorter telomeres in female, but not male, great tit (Parus major) nestlings. Females had longer telomeres than males when growing up in experimentally deparasitized nests but, likely because of the sex-specific effects of ectoparasitism on telomere length, this sexual dimorphism was absent in birds growing up in experimentally infested nests. Our results provide the first experimental evidence for a role of ectoparasitism in telomere dynamics in a natural vertebrate population, and suggest that the costs of infection manifest in sex-specific ways.

Dose- and time-dependent effects of an immune challenge on fish across biological levels

Due to global changes, fish are increasingly exposed to immune challenges associated with disease outbreaks in aquatic ecosystems. Adjustments in physiology and behavior are generally critical to maintaining homeostasis after an immune challenge, but there is limited knowledge on the specific thresholds and dynamics of responses across levels of biological organization in fish. In this study, we tested how different concentrations of an antigens mixture (phytohemagglutinin and lipopolysaccharide) affected innate immunity with potential consequences on oxidative stress, energy reserves, body condition, and behavior across time, using the common gudgeon (Gobio sp.) as model species. The immune challenge induced a transitory increase in lytic enzyme activity (i.e., lysozyme) and local immune response (i.e., skin swelling) 2 days after the antigen injection. The available energy stored in muscle was also reduced 4 days after injection, without inducing oxidative stress at the cellular level. Overall, the immune challenge induced limited costs at the molecular and cellular levels but had strong effects at the whole organism level, especially on behavior. Indeed, fish swimming activity and sociability were affected in a dose- and time-dependent manner. These results suggest that immune challenges have dose-dependent effects across levels of biological organization and that behavior is a key response trait to cope with pathogen-induced immune costs in the wild, although fitness consequences remain to be tested.

Nutritional ecology and ecological immunology in degus: Does early nutrition affect the postnatal development of the immune function?

Environmental conditions experienced by developing animals have an impact on the development and maturity of the immune system. Specifically, the diet experienced during early development influences the maintenance and function of the immune system in young and adult animals. It is well known that exposure to low-protein diets during early development are related to an attenuation of immunocompetence in adulthood. While this functional linkage has been widely studied in altricial models' mammals, it has been little explored how the nutritional history modulates the immune function in precocial animals. We evaluated the effect of dietary protein consumed during early development on the immune function and the oxidative costs in the precocial Caviomorph rodent Octodon degus, or degu. We evaluated components of the acute phase response (APR) and oxidative parameters before and after immune challenge. We found that after the immune challenge, the juveniles on the low-protein dietary treatment exhibited an attenuation of body temperature but showed higher levels of lipid peroxidation than juvenile degus on the high-protein diet. We did not find a significant effect of the interaction between diet and immune challenge on body mass, levels of inflammatory proteins, nor in the total antioxidant capacity. Our results suggest that some components of the immune function and the oxidative status in the degu can be modulated by diet during development. However, the modulation would depend on the immune variables analyzed, and the characteristics of the immune system of precocial rodents.

The immune response of bats differs between pre-migration and migration seasons

Maintaining a competent immune system is energetically costly and thus immunity may be traded against other costly traits such as seasonal migration. Here, we tested in long-distance migratory Nathusius’ pipistrelles (Pipistrellus nathusii), if selected branches of immunity are expressed differently in response to the energy demands and oxidative stress of aerial migration. During the migration period, we observed higher baseline lymphocyte and lower neutrophil levels than during the pre-migration period, but no stronger response of cellular effectors to an antigen challenge. Baseline plasma haptoglobin, as a component of the humoral innate immunity, remained similar during both seasons, yet baseline plasma haptoglobin levels increased by a factor of 7.8 in migratory bats during an immune challenge, whereas they did not change during the pre-migration period. Oxidative stress was higher during migration than during pre-migration, yet there was no association between blood oxidative status and immune parameters, and immune challenge did not trigger any changes in oxidative stress, irrespective of season. Our findings suggest that humoral effectors of the acute phase response may play a stronger role in the first-line defense against infections for migrating bats compared to non-migrating bats. We conclude that Nathusius’ pipistrelles allocate resources differently into the branches of their immune system, most likely following current demands resulting from tight energy budgets during migration.

A novel use of the leukocyte coping capacity assay to assess the immunomodulatory effects of organohalogenated contaminants in avian wildlife

Apex predators are characterized by high levels of biomagnifying organohalogenated contaminants (OHCs) which have been found to induce detrimental health effects in wildlife, such as immune system impairment. The leukocyte coping capacity (LCC) assay is a functional real-time measure of an innate immune response essential in pathogen resistance, known as the respiratory burst. The current study suggests the novel use of this tool to test whether OHCs impair the innate immune system of a sentinel top predator, the white-tailed eagle (Haliaeetus albicilla; WTE). The LCC analysis was performed in the field on WTE nestlings (n = 84) from northern Norway over two breeding seasons. Poly- and perfluoroalkyl substances (PFAS) dominated the total OHC load, surpassing the levels of legacy organochlorines. In addition, we detected significant negative correlations between concentrations of all polychlorinated biphenyls, p,p'-dichlorodiphenyldichloroethylene, perfluorohexane sulfonic acid and long-chain perfluorocarboxylic acids and the LCC of WTE nestlings. Based on our current findings reflecting a potential negative effect of both emerging and legacy OHCs on innate immune capacity, we suggest LCC to be a relevant and accessible test expanding the ecotoxicological toolbox to assess sub-lethal effects of OHCs in apex avian wildlife.

Involvement of steroid and antioxidant pathways in spleen-mediated immunity in migratory birds

The molecular underpinnings of the spleen-mediated immune functions during the period of heightened energetic needs in the year are not known in avian migrants. We investigated this, in Palearctic-Indian migratory male redheaded buntings, which exhibited vernal (spring) premigratory / early testicular maturation states under artificial long days. This was evidenced by increased dio2 and decreased dio3 mRNA expression in the hypothalamus, elevated levels of circulating corticosterone and testosterone, and enlarged testes in long-day-photostimulated birds, as compared to unstimulated controls under short days. The concomitant decrease in both mass and volume of the spleen, and increase in the heterophil/ lymphocyte ratio suggested the parallel innate immunity effects in photostimulated buntings. Importantly, we found increased mRNA expression of genes coding for the cytokines (il15 and il34), steroid receptors (nr3c2) and oxidative stress marker enzymes (gpx1 and sod1) in the spleen, suggesting the activation of both immune and antioxidant molecular pathways during the early photostimulated state. However, the splenic expressions of il1β, il6, tgfβ, ar and nos2 genes were not significantly different between long-day stimulated and short-day unstimulated birds. The negative correlation of plasma corticosterone levels with spleen mass further indicated a role of corticosterone in the modulation of the spleen function, probably via nr3c2 gene encoded mineralocorticoid receptors. These results suggest the activation of the spleen-mediated innate immunity in anticipation of the heightened energetic stress state of the photostimulated spring migratory/breeding period in migratory songbirds.

Curcumin addition in diet of laying hens under cold stress has antioxidant and antimicrobial effects and improves bird health and egg quality

Curcumin is an herbal component with several biological properties, and we highlight here the thermal stability, antioxidant and anti-inflammatory activity. We determined whether curcumin supplementation in the diets of laying hens under cold stress and naturally infected with Escherichia coli would control infection, and would have positive effects on overall health, as well as egg production and quality. We allocated 36 chickens that had been naturally infected with E. coli into two groups, with six replicates and three chickens per repetition: control group and curcumin group (200 mg curcumin/kg). The experimental period lasted 42 days, and fecal, blood and egg samples were collected at 1, 21 and 42 days We found that feces and eggs had lower total bacterial counts, E. coli counts and total coliform counts in the curcumin group at 21 and 42 days. In fresh eggs, the brightness and yellow intensity (b+) were significantly higher in the curcumin group. In stored eggs, higher specific gravity, albumen height and lower yolk pH were observed in the curcumin group. Fresh eggs collected and stored on day 42 showed lower levels of lipid peroxidation in the curcumin group, while the total antioxidant capacity in the stored eggs was significantly higher in the curcumin group. The curcumin group showed lower total leukocyte counts as a result of lower numbers of neutrophils and lymphocytes, as well as lower levels of total protein, alkaline phosphatase and alanine aminotransferase. Lower serum lipoperoxidation at 42 days was observed in the curcumin group, probably because of the higher activity of glutathione peroxidase and glutathione transferase in other words, because of antioxidant stimulation. Taken together, our findings suggest that curcumin supplementation in laying hens under cold stress and with colibacillosis has positive effects on infection control because of antioxidant stimulation.

Life-long testosterone and antiandrogen treatments affect the survival and reproduction of captive male red-legged partridges (Alectoris rufa)

Abstract

Sexual steroids can play an important role as life-history organizers. In males, high circulating testosterone levels induce physiological/behavioral costs and benefits, leading to trade-offs. However, studies simultaneously testing the impact of these levels in both fitness components (survival and fecundity) during lifetime are scarce and limited to wild birds. To determine the mortality causes or hormonal manipulation impacts on male fertility is, nonetheless, a difficult task in free-ranging animals that could be easier in captivity. We longitudinally monitored captive red-legged partridges (Alectoris rufa) and exposed males to high exogenous testosterone levels, anti-androgens, or a control treatment during each breeding period throughout their lives. Theory predicts that individuals maintaining high androgen levels should obtain higher fitness returns via reproduction, but suffer reduced longevity. Testosterone-treated male partridges, accordingly, lived shorter compared to controls, since they were more prone to die from a natural bacterial infection. However, the same birds seemed to have a lower capacity to fertilize eggs, probably due to endocrine feedback reducing testicular mass. These results show that exogenous testosterone can exert unpredicted effects on fitness parameters. Therefore, caution must be taken when drawing conclusions from non-fully controlled experiments in the wild. Males treated with the androgen-receptor blocker flutamide did not outlive controls as predicted by the life-history trade-off theory, but their mates laid eggs with higher hatching success. The latter could be due to mechanisms improving sperm quality/quantity or influencing maternal investment in egg quality. Testosterone receptor activity/amount could thus be as relevant to fitness as testosterone levels.

Significance statement

It has repeatedly been hypothesized that high testosterone levels induce a cost in terms of reduced lifetime reproductive success. This can be due to reduced fecundity or via shorter lifespan. This is, however, only supported by a handful of studies, mostly in wild birds. We tested this in captive male red-legged partridges, which allowed us to determine reproductive success and mortality causes. We increased testosterone levels or blocked its action with antiandrogens throughout life. High testosterone levels reduced the survival by making birds more prone to die by infection. The eggs produced by their mates also showed lower hatching success, a probable manipulation artifact that should be considered in avian studies in the wild. Interestingly, the androgen-receptor blocker flutamide increased lifetime hatching success compared to controls, suggesting that androgen receptor amounts/activity are even more relevant to fitness than testosterone levels.

Phagocyte activity reflects mammalian homeo- and hetero-thermic physiological states

BACKGROUND

Emergence of both viral zoonoses from bats and diseases that threaten bat populations has highlighted the necessity for greater insights into the functioning of the bat immune system. Particularly when considering hibernating temperate bat species, it is important to understand the seasonal dynamics associated with immune response. Body temperature is one of the factors that modulates immune functions and defence mechanisms against pathogenic agents in vertebrates. To better understand innate immunity mediated by phagocytes in bats, we measured respiratory burst and haematology and blood chemistry parameters in heterothermic greater mouse-eared bats (Myotis myotis) and noctules (Nyctalus noctula) and homeothermic laboratory mice (Mus musculus).

RESULTS

Bats displayed similar electrolyte levels and time-related parameters of phagocyte activity, but differed in blood profile parameters related to metabolism and red blood cell count. Greater mouse-eared bats differed from mice in all phagocyte activity parameters and had the lowest phagocytic activity overall, while noctules had the same quantitative phagocytic values as mice. Homeothermic mice were clustered separately in a high phagocyte activity group, while both heterothermic bat species were mixed in two lower phagocyte activity clusters. Stepwise regression identified glucose, white blood cell count, haemoglobin, total dissolved carbon dioxide and chloride variables as the best predictors of phagocyte activity. White blood cell counts, representing phagocyte numbers available for respiratory burst, were the best predictors of both time-related and quantitative parameters of phagocyte activity. Haemoglobin, as a proxy variable for oxygen available for uptake by phagocytes, was important for the onset of phagocytosis.

CONCLUSIONS

Our comparative data indicate that phagocyte activity reflects the physiological state and blood metabolic and cellular characteristics of homeothermic and heterothermic mammals. However, further studies elucidating trade-offs between immune defence, seasonal lifestyle physiology, hibernation behaviour, roosting ecology and geographic patterns of immunity of heterothermic bat species will be necessary. An improved understanding of bat immune responses will have positive ramifications for wildlife and conservation medicine.

Improving the Quality Characteristics and Shelf Life of Meat and Growth Performance in Goose Fed Diets Supplemented with Vitamin E

The present study was carried out to investigate the effect of dietary vitamin E on growth performance, cellular immunity, carcass characteristics, and meat quality in geese. Sixty-four one-day-old male geese were selected from 1200 goose chicks with the same average body weight (92.5 ± 2.5 g) and subjected to two treatments (basal diet or control and basal diet plus 120 mg/kg vitamin E supplement) with 4 replicates (8 geese per replicate) for 8 weeks. After slaughter, goose meat was aerobically packed in polyethylene packages and stored at 4 °C for 9 days. The results showed that vitamin E supplementation improved the growth performance, carcass yield percentage, and immune response of goose (p < 0.05). The addition of vitamin E in the diet significantly increased the protein and fat content of goose meat but decreased the moisture and ash content with respect to those obtained from the control diet. During storage, meat from the vitamin E treatment showed higher phenolic content and lower thiobarbituric acid reactive substances (TBARSs) and total volatile nitrogen (TVB-N) values than those from the control treatment. Vitamin E supplementation increased the saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs) in goose meat. However, goose meat supplemented with vitamin E displayed a significantly (p < 0.05) higher PUFA/SFA ratio than those of the control group. Based on the results, it was concluded that vitamin E could be used to improve the growth performance of goose, the meat composition in terms of the protein and fat content, the nutritional value in terms of the fatty acid composition, and the shelf life.