Quantifying corticosterone in feathers: validations for an emerging technique

Age effects on measurements of hypothalamic-pituitary-adrenal axis activation in laying hens

Stress is a complex but poorly understood topic, especially in commercial poultry species. However, hypothalamic-pituitary-adrenal axis (HPA) activation through either exogenous glucocorticoid or adrenocorticotropic hormone (ACTH) administration in birds generally results in increased circulating glucocorticoid levels, often associated with stress. HPA activation responses are complicated by physiological changes while the birds mature and enter production. The objective of this study was to evaluate changes in HPA activation in relation to physiological age of the bird. Ten each of Lohmann LSL-Lite hens received either a saline-mannitol or synthetic ACTH (ACTH1-24) injection at 6, 17, and 26 weeks of age (WOA). Blood was collected prior to ACTH injections, and one-, and two-hours post-injection. From these blood samples, white blood cell (WBC) differential counts, heterophil:lymphocyte (H:L) ratios (N = 10/treatment), and corticosterone and cortisol levels were measured using a high-performance liquid chromatography (HPLC) system coupled to a mass spectrometer (MS/MS) (N = 5/treatment). At 26 weeks of age, egg albumen samples were collected and corticosterone and cortisol measured using an HPLC system coupled to a mass spectrometer (MS/MS) (N = 5/treatment). In this study, plasma cortisol was unaffected by treatment and egg albumen corticosterone and cortisol were below detectable limits at all time points for both treatments. Plasma corticosterone increased 1 h after injection in the ACTH group at all ages; this was significant at 17 WOA (P < 0.0001). The H:L ratio was not affected by treatment but heterophils increased and lymphocytes decreased in the ACTH group compared to the control group, this difference was observed at 26 WOA (P < 0.0004). The results of this study suggest that the H:L ratio is not an accurate measure of acute HPA activation during the pullet phase and that plasma cortisol and albumen corticosterone and cortisol are not an accurate measure of acute HPA activation during the pullet or adult phases. Corticosterone may have some utility in capturing a physiological stress response in pullets and adult hens but requires further investigation.

Dermal glucocorticoids are uncoupled from stress physiology and infection

Ongoing amphibian population declines are caused by factors such as climate change, habitat destruction, pollution and infectious diseases not limited to chytridiomycosis. Unfortunately, action is taken against these factors once population collapses are underway. To avoid these post hoc responses, wildlife endocrinology aims to analyse physiological mediators that predict future population declines to inform wildlife management. Mediators typically investigated are stress hormones known as glucocorticoids, which are produced by the Hypothalamus-Pituitary-Interrenal axis (HPI axis). The HPI axis is the part of the endocrine system that helps amphibians cope with stress. Chronic increases in glucocorticoids due to stress can lead to immune dysfunction, which makes amphibians more susceptible to infectious diseases. Despite this predictive potential of glucocorticoids, interpretation of glucocorticoid data is confounded by sampling design and type. Glucocorticoid monitoring classically involves blood sampling, which is not widely applicable in amphibians as some are too small or delicate to sample, and repeated samples are often valued. To address this, we tried to validate skin swabbing via corticosterone (CORT) and adrenocorticotropin hormone (ACTH) injections in adults of two amphibian species: Eastern red-spotted newts, Notophthalmus viridescens viridescens, with natural skin infections with Batrachochytrium dendrobatidis (Bd) upon collection in the field, and Northern leopard frogs, Rana (Lithobates) pipiens, raised in captivity and naïve to Bd exposure. Further, we determined the predictive potential of skin glucocorticoids on Bd load in the field via correlations in Eastern red-spotted newts. We found that hormones present in the skin are not related to the HPI axis and poorly predict infection load; however, skin hormone levels strongly predicted survival in captivity. Although skin swabbing is not a valid method to monitor HPI axis function in these species, the hormones present in the skin still play important roles in organismal physiology under stressful conditions relevant to wildlife managers.

Effects of Increased Housing Space Without Altering Stocking Density on Body Weight, Stress, and Gut Microbiome in Broiler Chickens

Effective poultry management practices that promote chicken health are crucial for producing higher-quality chicken meat at a lower cost. This study examined the hypothesis that increasing space while maintaining stocking density may positively impact poultry health. We evaluated body weight (BW) as an indicator of growth, stress markers, and the composition of the gut microbiome by comparing two housing sizes: smaller (control) and larger (treatment) spaces, with 10 birds per space and a stocking density of 12.3 birds/m2. Chickens in the larger space had 15% higher BW (p = 0.06) compared to those in the smaller space when significance was evaluated at p < 0.10. Stress indicators such as blood cortisol (acute) and brain FKBP51 did not differ significantly. Faith's phylogenetic diversity was marginally higher in the larger space (p = 0.05), and microbial communities differed significantly between the two groups. The relative abundance of several genera, including Clostridium_sensu_stricto_1 (p = 0.02), Lactobacillus (p = 0.03), and Paracoccus (p < 0.01), was greater in the larger space, whereas Turicibacter (p = 0.02), Escherichia-Shigella (p = 0.01), and Lysinibacillus (p = 0.01) were more abundant in the smaller space. The larger and smaller spaces were associated with a significant (p < 0.05) increase in the abundance of 39 and 25 MetaCyc pathways, respectively, involved in amino acid and nitrogen metabolisms. These findings suggest that increasing housing space without altering stocking density or additional treatments may improve both growth and gut microbiome health in broilers. Our results provide insights into the relationship between chicken housing environments and the gut microbiome.

Analysis of the Reliability of Feather Sections for Corticosterone Measurement in Pekin Ducks

The aim of this study was to identify the feather section, among the whole feather, rachis, and vane, with the highest reliability for corticosterone measurement in 10 Pekin ducks aged 42 days. In total, 60 samples (i.e., 20 per section) were collected and each section was analyzed in duplicate. Corticosterone levels were measured using ELISA and statistical analyses were performed using ANOVA in SAS 9.2, and the intra-class correlation coefficient (ICC) was tested using IBM SPSS. The level in the whole feather (12.55 ± 4.41 pg/mg) was significantly lower (p < 0.001) than that in the rachis (18.12 ± 5.70 pg/mg). No significant differences were observed between the rachis and the vane (20.40 ± 3.04 pg/mg). ANOVA results confirmed substantial hormonal variability depending on the feather part analyzed. The ICCs for the whole feather, rachis, and vane were 0.923, 0.876, and 0.004, respectively. The vane section exhibited the highest concentration and lowest variance, whereas the whole feather exhibited the highest ICC. Although the whole feather had the lowest concentration, it exhibited greater consistency. Further research is necessary to improve the feather corticosterone analysis method for more accurate analysis. In conclusion, the whole feather provides the most reliable measure of corticosterone concentration among the three parts.

Malva sylvestris leaf powder as a feed additive affects the performance, carcass traits, meat quality attributes, serum antioxidants, stress physiology, intestinal bacterial counts, and gut morphology of broiler chicken

This study investigated the effect of supplementation of Malva sylvestris leaf powder (MSLP) on the production performance of broiler chicken. Ven Cobb broiler chicks (240 day-old male chicks) were distributed randomly into four treatments, each replicated four times, with 15 birds per replicate. The diets formulated were T1 (control) given basal diet only, T2 (basal diet +1.0% MSLP), T3 (basal diet +1.5% MSLP), and T4 (basal diet +2.0% MSLP). The highest improvement of 3.83% in the average daily gain (ADG) was recorded in the T3 group fed 1.5% Malva powder in the diet compared to the control (P = 0.009). The average daily feed intake (ADFI) tended to decrease with an increase in the dose of MSLP in the diet, with the lowest feed intake in the T4 group fed 2% MSLP. During the overall period (7-42 days), the feed/gain (F/G) ratio reduced significantly (P = 0.048) in the T3 and T4 groups compared to the control. The dressed and breast meat yield was found to be significantly (P < 0.05) higher in the T3 group, with no significant change (P > 0.05) in the thigh yield. The changes in the pH and water-holding capacity (WHC) of breast meat were found to be non-significant (p > 0.05) between the control and various other treatments. Thiobarbituric acid-reactive substances (TBARS) were significantly (P < 0.05) decreased in the T3 and T4 groups. There was no negative effect of including MSLP in the diet on the color coordinates of breast meat among different treatments. Compared to the control, the serum immunoglobulin values increased significantly (P < 0.05) in the T3 and T4 groups. Superoxide dismutase (SOD) showed no difference between various treatments; however, malondialdehyde (MDA) decreased significantly (P < 0.05) according to dietary treatments. Serum cortisol increased significantly (P < 0.05) in the T4 group compared to other treatments. The inclusion of Malva powder in the diet at the 2% level significantly (P < 0.05) decreased the coliform count compared to the control birds. Supplementation with Malva powder resulted in a significant (P < 0.05) increase in the villus height-to-crypt depth (VH:CD) ratio of broiler birds in the T3 and T4 groups. In conclusion, MSLP supplementation at 1.5% and 2% resulted in improved production performance of broiler chicken.

Ultrasensitive upconverting nanoprobes for in situ imaging of drug-induced liver injury using miR-122 as the biomarker

Drug-induced liver injury (DILI) is a frequent adverse drug reaction. The current clinical diagnostic methods are inadequate for accurate and early detection of DILI due to the lack of effective diagnostic biomarkers. Hepatocyte-specific miR-122 is released from injured hepatocytes promptly and its efflux is significantly correlated with the progression of DILI. Therefore, achieving precise in situ detection of miR-122 with high sensitivity is vital for early visualization of DILI. Herein, a new nanoprobe, consisting of miR-122 aptamer, upconversion nanoparticles (UCNPs) and Prussian blue nanoparticles (PBNPs) was introduced for the early and sensitive detection of DILI in situ. As the nanoprobes reached in the liver, miR-122 aptamer-based entropy-driven strand displacement (ESDR) signal amplification reaction was triggered and luminescence resonance energy transfer (LRET) between UCNPs and PBNPs was responded to achieve the high-fidelity detection of DILI. A negative correlation was observed between the intensity of upconversion luminescence (UCL) and the concentration of miR-122. UCL imaging conducted both in vivo and ex vivo indicated that a reduction in miR-122 concentration led to an increase in UCL intensity, revealing a precise state of DILI. The detection technique demonstrated a positive correlation between signal intensity and severity, offering a more straightforward and intuitive method of visualizing DILI.

Effects of Heat Stress on the Laying Performance, Egg Quality, and Physiological Response of Laying Hens

As high temperature and relative humidity (RH) are the main environmental factors causing heat stress, the temperature-humidity index (THI) serves as an indicator of heat stress in livestock animals. This study aimed to determine the effects of heat stress on the laying performance, physiological responses, egg quality, and blood profile of laying hens by subjecting them to environmental conditions with varying THI levels (68-85) for 28 days. The indicators of laying performance, such as feed intake (-30%) and egg production rate (-11%), significantly decreased in the hens exposed to severe heat stress (33 °C, 66% RH) compared to those exposed to thermoneutral conditions (21 °C, 68% RH). Moreover, severe heat stress reduced the egg yolk color, eggshell thickness and strength, and Haugh units of the eggs produced by the laying hens. Furthermore, a significant increase in serum K+ and a decrease in Na+ levels were observed in the hens subjected to severe heat stress compared with those under thermoneutral conditions. Our results indicate that heat stress alters the physiological responses and metabolism of laying hens, resulting in a lower egg quality and production rate.

Clicker Training as an Applied Refinement Measure in Chickens

When using chickens in animal studies, the handling of these animals for sample collection or general examinations is considered stressful due to their prey nature. For the study presented here, plasma and salivary corticosterone as well as New Area Test behavior and fecal output were used to evaluate whether it is possible to influence this stress perception using a three-week clicker training program. The results indicate that clicker training seems to be a suitable refinement measure in the sense of cognitive enrichment for the husbandry of this species. However, since it was also shown that three-week training was not sufficient to sustainably reduce the stress perception with regard to prolonged stressor exposure, and since it was also evident that manipulations such as routine blood sampling are perceived as less stressful than assumed, further studies with prolonged training intervals and situations with higher stressor potential are warranted. Also, further parameters for training assessment must be considered. For the general use of training as a supportive measure in animal experiments, its proportionality must be considered, particularly considering the expected stress and adequate training time.

Evaluation of physiological stress in free-ranging bears: current knowledge and future directions

Stress responses, which are mediated by the neurogenic system (NS) and hypothalamic-pituitary-adrenal (HPA) axis help vertebrates maintain physiological homeostasis. Fight-or-flight responses are activated by the NS, which releases norepinephrine/noradrenaline and epinephrine/adrenaline in response to immediate stressors, whilst the HPA axis releases glucocorticoid hormones (e.g. cortisol and corticosterone) to help mitigate allostatic load. There have been many studies on stress responses of captive animals, but they are not truly reflective of typical ranges or the types of stressors encountered by free-ranging wildlife, such as responses and adaptation to environmental change, which are particularly important from a conservation perspective. As stress can influence the composition of age and sex classes of free-ranging populations both directly and indirectly, ecological research must be prioritised towards more vulnerable taxa. Generally, large predators tend to be particularly at risk of anthropogenically driven population declines because they exhibit reduced behavioural plasticity required to adapt to changing landscapes and exist in reduced geographic ranges, have small population sizes, low fecundity rates, large spatial requirements and occupy high trophic positions. As a keystone species with a long history of coexistence with humans in highly anthropogenic landscapes, there has been growing concern about how humans influence bear behaviour and physiology, via numerous short- and long-term stressors. In this review, we synthesise research on the stress response in free-ranging bear populations and evaluate the effectiveness and limitations of current methodology in measuring stress in bears to identify the most effective metrics for future research. Particularly, we integrate research that utilised haematological variables, cardiac monitors and Global Positioning System (GPS) collars, serum/plasma and faecal glucocorticoid concentrations, hair cortisol levels, and morphological metrics (primarily skulls) to investigate the stress response in ursids in both short- and long-term contexts. We found that in free-ranging bears, food availability and consumption have the greatest influence on individual stress, with mixed responses to anthropogenic influences. Effects of sex and age on stress are also mixed, likely attributable to inconsistent methods. We recommend that methodology across all stress indicators used in free-ranging bears should be standardised to improve interpretation of results and that a wider range of species should be incorporated in future studies.

Stress Concepts and Applications in Various Matrices with a Focus on Hair Cortisol and Analytical Methods

When studying stress in animals, it is important to understand the types of stress and their classification, and how to assess the stress levels in different animal species using different matrices accurately and precisely. The classification of stress types helps to distinguish between good stress (eustress) and bad stress (distress). Hence, first, it is crucial to assess the animal's level of stress in a non-intrusive manner and second to identify the type of stress that is best suited to its environment. Third, it is also important to analyze the obtained samples using a suitable method to increase the validity of stress hormone measurements. Therefore, in this review, we aim to: (1) explain the classification of stress, (2) discuss the wide range of body matrices (e.g., saliva, milk, hair, urine, feces, sweat, fins, etc.) that can be used as samples to evaluate stress levels, as well as their comparisons and limitations, and present the reliable matrices for measuring stress hormones with special emphasis on hair, (3) compare the analytical methods for measuring stress hormones after sample preparation. Despite some literature that does not include hair as a reliable matrix for evaluating stress levels, hair is one of the matrices for measuring long-term stress hormone accumulations. This review discusses some factors that influence the level of stress hormones in the hair. By understanding these issues, the scientific community will not only be able to improve the understanding of stress and biomarker evaluation but also suggest how to deal with the consequences of stress in future research.

Selection of appropriate biomatrices for studies of chronic stress in animals: a review

Cortisol and corticosterone, hormones traditionally considered biomarkers of stress, can be measured in fluid biomatrices (e.g., blood, saliva) from live animals to evaluate conditions at sampling time, or in solid biomatrices (e.g., hair, feather) from live or dead animals to obtain information regarding long-term changes. Using these biomarkers to evaluate physiological stress responses in domestic animals may be challenging due to the diverse characteristics of biomatrices for potential measurement. Ideally, a single measurement from the biomatrix should be sufficient for evaluating chronic stress. The availability of appropriate and cost-effective immunoassay methods for detecting the biomarkers should also be considered. This review discusses the strengths and limitations of different biomatrices with regard to ensuring the highest possible reliability for chronic stress evaluation. Overall, solid biomatrices require less frequent sampling than other biomatrices, resulting in greater time- and cost-effectiveness, greater ease of use, and fewer errors. The multiplex immunoassay can be used to analyze interactions and correlations between cortisol and other stress biomarkers in the same biomatrix. In light of the lack of information regarding appropriate biomatrices for measuring chronic stress, this review may help investigators set experimental conditions or design biological research.

Clutch Abandoning Parasitised Yellow Warblers Have Increased Circulating Corticosterone With No Effect of Past Corticosterone or Differences in Egg Maculation Characteristics

Parental care can be costly to parents’ fitness. As such, abandonment of the current reproductive attempt may benefit potential future opportunities, maximising lifetime reproductive success. Obligate brood parasitism, a reproductive strategy in which parasites lay their eggs in the nests of other species and rely solely on them to raise the parasitic young, is an ideal system to study brood abandonment. Some parasitised host species have evolved anti-parasitic defences, notably clutch abandonment (egg burial and nest desertion), that may mitigate negative consequences of parasitism. Abandonment of clutches due to parasitism is not unlike abandonment of reproduction in times of stress, suggesting that host responses to parasitism could be triggered at least partly by elevated stress hormones that mediate individual decisions. Yet, the mechanistic basis for clutch abandonment remains unclear. Here, we experimentally parasitised clutches of yellow warblers (Setophaga petechia), a common host of the brown-headed cowbird (Molothrus ater), with model cowbird eggs to examine whether host circulating corticosterone (CORT) differed among females that accepted parasitic eggs or rejected them through clutch abandonment. We also assessed whether feather CORT, a measure of past corticosterone exposure, differed between accepters and abandoners. Finally, we investigated whether egg visual signals, specifically differences in maculation characteristics between model cowbird and host eggs, predicted abandonment of experimentally parasitised clutches. Circulating CORT was higher in females who abandoned their parasitised clutches, but not in those who accepted, relative to controls with no egg addition. Past stress and differences in maculation characteristics did not predict whether individuals accepted or abandoned experimentally parasitised clutches. Moreover, differences in maculation characteristics between the host and model cowbird eggs did not predict CORT levels or nest abandonment. Thus, parasitism with subsequent clutch abandonment may be associated with elevated circulating CORT, but neither past stress nor differences in maculation characteristics influenced abandonment. The combination of these results contributes to our understanding of the roles of corticosterone and egg visual signals in the context of clutch abandonment in brood parasitism specifically, and of parental care more broadly.

Rank- and sex-specific differences in the neuroendocrine regulation of glucocorticoids in a wild group-living fish

Individuals that live in groups experience different challenges based on their social rank and sex. Glucocorticoids have a well-established role in coordinating responses to challenges and glucocorticoid levels often vary between ranks and sexes. However, the neuroendocrine mechanisms regulating glucocorticoid dynamics in wild groups are poorly understood, making it difficult to determine the functional consequences of differences in glucocorticoid levels. Therefore, we observed wild social groups of a cooperatively breeding fish (Neolamprologus pulcher) and evaluated how scale cortisol content (an emerging method to evaluate cortisol dynamics in fishes) and expression of glucocorticoid-related genes varied across group members. Scale cortisol was detectable in ~50% of dominant males (7/17) and females (7/15)-but not in any subordinates (0/16)-suggesting that glucocorticoid levels were higher in dominants. However, the apparent behavioural and neuroendocrine factors regulating cortisol levels varied between dominant sexes. In dominant females, higher cortisol was associated with greater rates of territory defense and increased expression of corticotropin-releasing factor in the preoptic and hypothalamic regions of the brain, but these patterns were not observed in dominant males. Additionally, transcriptional differences in the liver suggest that dominant sexes may use different mechanisms to cope with elevated cortisol levels. While dominant females appeared to reduce the relative sensitivity of their liver to cortisol (fewer corticosteroid receptor transcripts), dominant males appeared to increase hepatic cortisol breakdown (more catabolic enzyme transcripts). Overall, our results offer valuable insights on the mechanisms regulating rank- and sex-based glucocorticoid dynamics, as well as the potential functional outcomes of these differences.

Short-term elevations in glucocorticoids do not alter telomere lengths: A systematic review and meta-analysis of non-primate vertebrate studies

Background

The neuroendocrine stress response allows vertebrates to cope with stressors via the activation of the Hypothalamic-Pituitary-Adrenal (HPA) axis, which ultimately results in the secretion of glucocorticoids (GCs). Glucocorticoids have pleiotropic effects on behavior and physiology, and might influence telomere length dynamics. During a stress event, GCs mobilize energy towards survival mechanisms rather than to telomere maintenance. Additionally, reactive oxygen species produced in response to increased GC levels can damage telomeres, also leading to telomere shortening. In our systematic review and meta-analysis, we tested whether GC levels impact telomere length and if this relationship differs among time frame, life history stage, or stressor type. We hypothesized that elevated GC levels are linked to a decrease in telomere length.

Methods

We conducted a literature search for studies investigating the relationship between telomere length and GCs in non-human vertebrates using four search engines: Web of Science, Google Scholar, Pubmed and Scopus, last searched on September 27th, 2020. This review identified 31 studies examining the relationship between GCs and telomere length. We pooled the data using Fisher’s Z for 15 of these studies. All quantitative studies underwent a risk of bias assessment. This systematic review study was registered in the Open Science Framework Registry (https://osf.io/rqve6).

Results

The pooled effect size from fifteen studies and 1066 study organisms shows no relationship between GCs and telomere length (Fisher’s Z = 0.1042, 95% CI = 0.0235; 0.1836). Our meta-analysis synthesizes results from 15 different taxa from the mammalian, avian, amphibian groups. While these results support some previous findings, other studies have found a direct relationship between GCs and telomere dynamics, suggesting underlying mechanisms or concepts that were not taken into account in our analysis. The risk of bias assessment revealed an overall low risk of bias with occasional instances of bias from missing outcome data or bias in the reported result.

Conclusion

We highlight the need for more targeted experiments to understand how conditions, such as experimental timeframes, stressor(s), and stressor magnitudes can drive a relationship between the neuroendocrine stress response and telomere length.

Investigation of keratinase digestion to improve steroid hormone extraction from diverse keratinous tissues

Monitoring the physiology of wild populations presents many technical challenges. Blood samples, long the gold standard of wildlife endocrinology studies, cannot always be obtained. The validation and use of non-plasma samples to obtain hormone data have greatly improved access to more integrated information about an organism's physiological state. Keratinous tissues like skin, hair, nails, feathers, or baleen store steroid hormones in physiologically relevant concentrations, are stable across decades, and can be used to retrospectively infer physiological state at prior points in time. Most protocols for steroid extraction employ physical pulverization or cutting of the sample, followed by mixing with a solvent. Such methods do produce repeatable and useful data, but low hormone yield and detectability issues can complicate research on small or rare samples. We investigated the use of keratinase, an enzyme that breaks down keratin, to improve the extraction and yield of corticosterone from vertebrate keratin tissues. Corticosterone content of keratinase-digested extracts were compared to non-keratinase extracts for baleen from three species of whale (blue, Balaenoptera musculus; bowhead, Balaena mysticetus; southern right, SRW; Eubalaena australis), shed skin from two reptiles (tegu lizard, Salvator merianae; narrow-headed garter snake, Thamnophis rufipunctatus), hair from arctic ground squirrel (AGS; Urocitellus parryii), feathers from Purple Martins (PUMA; Progne subis), and spines from the short-beaked echidna (Tachyglossus aculeatus). We tested four starting masses (10, 25, 50, 100 mg) for each sample; digestion was most complete in the 10 and 25 mg samples. A corticosterone enzyme immunoassay (EIA) was validated for all keratinase-digested extracts. In all sample types except shed skin from reptiles, keratinase digestion improved hormone yield, with PUMA feathers and blue whale baleen having the greatest increase in apparent corticosterone content (100% and 66% more hormone, respectively). The reptilian shed skin samples did not benefit from keratinase digestion, actually yielding less hormone than controls. With further optimization and refinement, keratinase digestion could greatly improve yield of steroid hormones from various wildlife epidermal tissue types, allowing more efficient use of samples and ultimately improving understanding of the endocrine physiology of wild populations.

The Effect of Egg Laying on Feather and Plasma Corticosterone Concentrations in Turkey (Meleagris gallopavo) Hens

Simple Summary

It is not known if an energetically demanding process, such as egg laying, can affect corticosterone measured in turkey feathers and blood plasma, or if there are differences between feather types and genetic lines. The objective of this study was to compare hormone levels from feathers and plasma taken before and during egg laying. We found that the corticosterone in the feathers were higher during egg laying, but only for one genetic line. This genetic line produces more eggs and, so, the elevated corticosterone may reflect the higher metabolic investment in producing eggs. Increases in corticosterone levels were found in different feather types; however, the overall hormone level differed between feather types. Unlike the feathers, we found a decrease in plasma hormone measures between the two periods which might reflect the influence of gonadal development or suppression of acute hormone production during lay. From this study, we conclude that feathers can be used to detect increases in corticosterone during periods of high energy demand, but the genetic line needs to be considered, and the results may not correspond with plasma measures. This study also reinforces the requirement for consistent feather sampling when using corticosterone levels in feathers as non-invasive biomarkers.

Abstract

Phenological differences in energy demand (i.e., reproductive status) might influence the measurement of corticosterone. The objective of this study was to compare corticosterone concentrations in feathers (FCORT) and plasma (PCORT) for turkey hens before and during egg laying. Secondary feathers 1 and 3, and a plasma sample were collected from 50 hens at 30 weeks (before egg laying) from two purebred lines. The hens were reexamined during lay (45 weeks) to collect regrown feathers and plasma samples. Corticosterone concentrations were measured using an ELISA. Linear mixed models were used to assess the effect of genetic line (A vs. B) and period (pre-lay vs. lay) on FCORT and PCORT levels. An increase in FCORT during lay was detected for line B (p < 0.0001), but not line A (p = 0.3076). An increase in FCORT during lay was detectable in both feather types, but there was a difference between secondary 1 and 3 in FCORT concentration within each line studied. Conversely, PCORT decreased between the pre-lay and lay periods for both lines, although the decrease was more substantial for line A (p < 0.0001). Differences in metabolic investment in egg production between the two genetic lines may explain the different FCORT response during lay. The results from this study provide insight into how periods of high energy demand may influence corticosterone which should be considered when interpreting results.

Early-Life Corticosterone Body Condition Influence Social Status and Survival in a Food-Caching Passerine

Individuals undergo profound changes throughout their early life as they grow and transition between life-history stages. As a result, the conditions that individuals experience during development can have both immediate and lasting effects on their physiology, behavior, and, ultimately, fitness. In a population of Canada jays in Algonquin Provincial Park, Ontario, Canada, we characterized the diet composition and physiological profile of young jays at three key time points during development (nestling, pre-fledge, and pre-dispersal) by quantifying stable-carbon (δ13C) and -nitrogen (δ15N) isotopes and corticosterone concentrations in feathers. We then investigated the downstream effects of early-life diet composition, feather corticosterone, and environmental conditions on a juvenile's social status, body condition, and probability of being observed in the fall following hatch. Across the three time points, the diet of Canada jay young was composed primarily of vertebrate tissue and human food with the proportion of these food items increasing as the jays neared dispersal. Feather corticosterone concentrations also shifted across the three time points, decreasing from nestling to pre-dispersal. Dominant juveniles had elevated corticosterone concentrations in their feathers grown pre-dispersal compared with subordinates. High body condition as nestlings was associated with high body condition as juveniles and an increased probability of being observed in the fall. Together, our results demonstrate that nestling physiology and body condition influence the social status and body condition once individuals are independent, with potential long-term consequences on survival and fitness.

Conservation physiology and the COVID-19 pandemic

The COVID-19 pandemic and associated public health measures have had unanticipated effects on ecosystems and biodiversity. Conservation physiology and its mechanistic underpinnings are well positioned to generate robust data to inform the extent to which the Anthropause has benefited biodiversity through alterations in disturbance-, pollution- and climate change-related emissions. The conservation physiology toolbox includes sensitive biomarkers and tools that can be used both retroactively (e.g. to reconstruct stress in wildlife before, during and after lockdown measures) and proactively (e.g. future viral waves) to understand the physiological consequences of the pandemic. The pandemic has also created new risks to ecosystems and biodiversity through extensive use of various antimicrobial products (e.g. hand cleansers, sprays) and plastic medical waste. Conservation physiology can be used to identify regulatory thresholds for those products. Moreover, given that COVID-19 is zoonotic, there is also opportunity for conservation physiologists to work closely with experts in conservation medicine and human health on strategies that will reduce the likelihood of future pandemics (e.g. what conditions enable disease development and pathogen transfer) while embracing the One Health concept. The conservation physiology community has also been impacted directly by COVID-19 with interruptions in research, training and networking (e.g. conferences). Because this is a nascent discipline, it will be particularly important to support early career researchers and ensure that there are recruitment pathways for the next generation of conservation physiologists while creating a diverse and inclusive community. We remain hopeful for the future and in particular the ability of the conservation physiology community to deliver relevant, solutions-oriented science to guide decision makers particularly during the important post-COVID transition and economic recovery.

Corticosterone in feathers: Inter- and intraindividual variation in pullets and the importance of the feather type

Measuring corticosterone concentrations in feathers of poultry may be suitable to determine birds' exposure to stress. It is thinkable, that in laying hens such information could be helpful as an animal welfare indicator to evaluate adverse husbandry conditions and to predict the risk of developing behavioral disorders, such as feather pecking and cannibalism. Yet, there are some fundamental issues which remain unclear. Therefore, the objective of the current pilot study was to examine the inter- and intraindividual variation of pullets at the end of the rearing period, when most of the feathers are fully grown and animals are reaching sexual maturity. Flight feathers from both wings (n = 4), the tail (n = 2 – 3), and body feathers (n = 1 pool of 3 – 5 feathers) were taken from pullets (n = 10), genetics Lohmann Brown, at an age of 19 weeks who were reared in the same flock (N = 728). Corticosterone analysis was performed applying a validated protocol for laying hens. Results indicate not only high intraindividual, but also high interindividual variation. Mean over all samples was 75.2 pg/mg (± 38.58 pg/mg, n = 76), showing higher intraindividual variation (between feather types; SD: 23.75 pg/mg – 49.38 pg/mg; n = 10 pullets) than interindividual variation (within feather types; SD: 11.91 pg/mg – 49.55 pg/mg; n = 6 feather types). The variation between different feather types within one bird was higher than the variation within one feather type between different birds, indicating that birds a) may respond differently when exposed to stressors and b) corticosterone measurements should be done with the same feather type.

Effects of feather processing methods on quantity of extracted corticosterone in broiler chickens

Corticosterone is known as a biological stress index in many species including birds. Feather corticosterone concentration (FCC) has increasingly been used as a measure for chronic stress status in broiler chickens. As sample preparation is the first step of analytical process, different techniques of feather matrix disruption need to be validated for obtaining better result in analysing corticosterone extraction. The current study was a validation of pulverizing the feather by bead beater (BB) and surgical scissors (SS) processing prior to corticosterone extraction in feather of broiler chickens. The type of feather processing prior to the hormone extraction may alter the final output. Thereby, finding a standard method according to laboratory facilities is pivotal. This study carried out to determine the effects of feather pulverization methods on the extraction amount of corticosterone in broiler chickens. Feathers were sampled from four weeks old Ross 308 broiler chickens (n = 12 birds). All broiler chickens were kept under the same environmental condition and had access to feed and water. Feather samples were assigned to one of the following processing methods 1) using a BB for pulverizing and 2) using a SS for chopping into tiny pieces. Each sample was duplicated into two wells during enzyme immunoassay (EIA) analysis to improve the accuracy of the obtained data. The results showed lower standard errors and constant output of FCC by using the BB method compared with the SS method. Overall comparison of FCC showed a significantly higher (p < 0.001) amount of the FCC in the BB compared with the SS. Overall, using the BB method is recommended over the SS method for feather processing due to the ability to homogenize a large number of samples simultaneously, ease of use and greater extraction of feather corticosterone.

Evaluation of the hematological and clinical biochemical markers of stress in broiler chickens

Background and Aim:

Stress significantly affects health and productivity of animals. There is need for affordable and easy-to-assay markers of physiological stress in broilers. This study evaluated hematological and serum biochemical markers of physiologic stress in broiler chickens.

Materials and Methods:

Thirty day-old broiler chickens were assigned to three groups of ten broilers each during the 56-day study. Group 1 broilers served as the control and were not exposed to any stressors; Group 2 broilers were stocked at the stress density of 50 kg BW m^–2 from day 49 to 56 while Group 3 broilers had their feed withdrawn 36 h before blood collection on day 56. Blood samples were collected on day 49 (pre-stress sample) and day 56 (post-stress sample) from all the birds and subjected to hematological and serum biochemical analysis.

Results:

The parameters did not vary significantly (p>0.05) pre-stress. Post-stress, there were significant variations in the heterophil, lymphocyte, and eosinophil counts and in the heterophil to lymphocyte ratio across the three groups. The concentrations of the plasma fibrinogen and serum albumins, sodium, and sodium to potassium ratio of the broilers varied significantly across the groups.

Conclusion:

Heterophil, eosinophil, and lymphocyte counts, the heterophil to lymphocyte ratio, plasma fibrinogen, serum albumin, sodium, and sodium to potassium ratio are significant markers of physiological stress in broilers.

Corticosterone in feathers of laying hens: an assay validation for evidence-based assessment of animal welfare

Studies indicate that the evaluation of animal welfare in birds may be carried out with the measurement of the stress-related hormone corticosterone in feathers. However a standardized procedure for corticosterone measurements in feathers is lacking, a validation needs to be carried out for each new species before implementation. The aim of the present study was to establish a valid method to measure corticosterone concentrations in feathers of laying hens in a precise and repeatable manner using an established and commercially available ELISA. Validation was performed with feather pools of tail and interscapular feathers of commercial Lohmann Brown laying hens. Assessment groups, consisting of 5 replicates, were created. All replicates of an assessment group were processed at the same time. Each replicate was run in 4 repetitions by ELISA. Intra-assay and interassay CV was 7.5 and 6.4%, respectively. The serial dilution showed linearity and parallelism. Examining the hormone extraction efficiency by using different methanol volumes resulted in no statistical differences (P > 0.05). Pulverized feathers showed higher corticosterone values than minced feathers (P > 0.05). Differences were shown between 2 feather types (tail vs. interscapular feathers; P < 0.05), as well as between vane and rachis (P < 0.05). Performance of a freeze-thaw cycle led to a decrease of corticosterone concentrations in the samples. A possible effect of UV-A radiation on the stability of corticosterone in the feathers was not found (P > 0.05). With the present study, a valid protocol, feasible for analyzing feather pools of laying hens, was developed. It may provide fundamentals for further investigations on corticosterone in feathers as a noninvasive indicator to evaluate aspects of animal welfare.

Research Note: Quantifying corticosterone in turkey (Meleagris gallopavo) feathers using ELISA

The measurement of corticosterone in feathers is an appealing tool for assessing glucocorticoids in wild and domestic bird species. Feather corticosterone measurements can be performed noninvasively and can provide a means for comparing glucocorticoid secretion between individual birds; thus, such measurements can be used to assess the welfare of domestic poultry. The focus of this study was to assess the validity of detecting corticosterone in turkey (Meleagris gallopavo) feathers using an ELISA and investigate differences between genetic lines. Primary feather 9 was obtained at a processing plant from 123 individuals from 3 different purebred turkey lines (line A [N = 46], line B [N = 24], and line C [N = 53]). Assay validation tests were performed using a commercially available ELISA kit (Cayman Chemicals, Cedarlane Labs, Canada). Indicators of accuracy, recovery, precision, and sensitivity were sufficient. Significant differences in feather corticosterone concentration between the 3 lines were observed. Line C had significantly higher feather corticosterone than line A (P < 0.0001) and line B (P = 0.036). These results indicate that the quantification of feather corticosterone using an ELISA is a valid method for assessing glucocorticoid levels in turkeys. This is the first report of differences in feather corticosterone between different purebred turkey lines. Differences observed between purebred lines provide an intriguing basis for further investigation into the genetic parameters of glucocorticoid levels in turkeys.