Synthesis of Measuring Steroid Metabolites in Goose Feces

Measuring urofecal glucocorticoid metabolites in broiler chicken: a noninvasive tool for assessing stress as a marker of welfare

The poultry industry is an important and still growing sector in many parts of the world. For ethical reasons and due to increased consumer awareness for animal welfare in production animals, it is of importance to establish a reliable and objective test system for monitoring and improving health and welfare. During the rearing process, broiler chickens are exposed to numerous potential stressors and management interventions (e.g. weighing of individual animals, preslaughter fasting and capture processes), but assessing the level of stress perceived by the animals entirely through behavioral observations can be challenging. Monitoring stress-related physiological markers, such as glucocorticoids, can be an accurate and presumably more objective addition. To avoid additional stressors induced by blood collection, a noninvasive approach using urofecal samples is advisable. However, a thorough validation is needed to establish a suitable test system for measuring stress hormone levels, including potential effects of the time of day of collection or the time that has elapsed since defecation. Therefore, the aim of this study was to test the stability of urofecal glucocorticoid metabolites (ufGCM) postdefecation, to determine time of day effects on ufGCM levels, and to investigate the effect of standard management procedures on ufGCM concentrations in broiler chickens. Our results revealed a time window of 4 h in which fecal samples from broilers can be collected without major alterations to the ufGCM concentrations. In this regard, a "fecal box" proved useful for collecting uncontaminated fresh samples. The time of day of sample collection did not influence ufGCM concentrations significantly. Moreover, the used assay proved to be sensitive enough to detect even small and short-lasting activations of the HPA axis induced by handling, confinement, and fasting. Thus, the system used can be a powerful and easy to apply tool in a chicken production setup for assessing stress as a marker of welfare in commercially housed broiler chickens, which in the long-term can also improve production, particularly with regard to process quality.

Common myths of glucocorticoid function in ecology and conservation

Glucocorticoids are popular hormones to measure in both biomedical and ecological studies of stress. Many assumptions used to interpret glucocorticoid results are derived from biomedical data on humans or laboratory rodents, but these assumptions often fail for wild animals under field conditions. We discuss five common assumptions often made about glucocorticoids in ecological and conservation research that are not generally supported by the literature. (1) High acute elevations of glucocorticoids indicate an animal in distress. In fact: because glucocorticoids are needed to survive stressors, elevated concentrations often reflect adequate coping. (2) Low glucocorticoid concentrations indicate a healthy animal. In fact: because glucocorticoids are important in responding to stressors, low glucocorticoid concentrations might indicate the lack of adequate coping. (3) Sustained elevated glucocorticoids indicate chronically stressed animals. In fact: glucocorticoid concentrations by themselves have no predictive value in diagnosing chronic stress. (4) Glucocorticoids mobilize energy to survive short-term stressors such as predator attacks. In fact: glucocorticoids' primary impact on energy regulation is to remove glucose transporters from cell surfaces. Not only is this process too slow to provide short-term energy, but glucocorticoid-induced increases in glucose reflect decreased, not increased, glucose utilization. (5) Glucocorticoid measurements in non-blood tissues (e.g., feces, hair, feathers, etc.) are equivalent to blood concentrations. In fact: these alternative tissues present imperfect reflections of blood concentrations, and it is blood concentrations that interact with receptors to evoke biological change. In summary, proper consideration of these common assumptions will greatly aid in interpreting glucocorticoid data from ecological and conservation studies.

Circadian Rhythm and Stress Response in Droppings of Serinus canaria

Serinus canaria is a widespread domestic ornamental songbird, whose limited knowledge of biology make compelling studies aimed to monitor stress. Here, a commercial enzyme immunoassay was adopted to measure immunoreactive corticosterone (CORT) in single Serinus canaria dropping sample, to monitor the daily fecal excretion of CORT in birds bred singly or in-group and to detect the effect promoted by aviary or small transport cage restraint. A robust daily rhythm of CORT was recorded in animals held on short-day light cycle, independent of bred conditions (single or group), which persisted when space availability was modified in single bred animal (transfer in aviary and transport cages). By contrast, a significant change in CORT excretion was recorded when group bred animals are restrained in a smaller cage. The daily rhythm in CORT excretion in response to manipulation showed the greatest response at the beginning of the light period, followed by the absence of the peak usually recorded at the end of the dark phase. These data indicated that EIA could be used as a reliable noninvasive approach to monitor the stress induced by restraint conditions in Serinus canaria.

Non-Invasive Measurement of Adrenocortical Activity in Blue-Fronted Parrots (Amazona aestiva, Linnaeus, 1758)

Parrots kept in zoos and private households often develop psychological and behavioural disorders. Despite knowing that such disorders have a multifactorial aetiology and that chronic stress is involved, little is known about their development mainly due to a poor understanding of the parrots' physiology and the lack of validated methods to measure stress in these species. In birds, blood corticosterone concentrations provide information about adrenocortical activity. However, blood sampling techniques are difficult, highly invasive and inappropriate to investigate stressful situations and welfare conditions. Thus, a non-invasive method to measure steroid hormones is critically needed. Aiming to perform a physiological validation of a cortisone enzyme immunoassay (EIA) to measure glucocorticoid metabolites (GCM) in droppings of 24 Blue-fronted parrots (Amazona aestiva), two experiments were designed. During the experiments all droppings were collected at 3-h intervals. Initially, birds were sampled for 24 h (experiment 1) and one week later assigned to four different treatments (experiment 2): Control (undisturbed), Saline (0.2 mL of 0.9% NaCl IM), Dexamethasone (1 mg/kg IM) and Adrenocorticotropic hormone (ACTH; 25 IU IM). Treatments (always one week apart) were applied to all animals in a cross-over study design. A daily rhythm pattern in GCM excretion was detected but there were no sex differences (first experiment). Saline and dexamethasone treatments had no effect on GCM (not different from control concentrations). Following ACTH injection, GCM concentration increased about 13.1-fold (median) at the peak (after 3-9 h), and then dropped to pre-treatment concentrations. By a successful physiological validation, we demonstrated the suitability of the cortisone EIA to non-invasively monitor increased adrenocortical activity, and thus, stress in the Blue-fronted parrot. This method opens up new perspectives for investigating the connection between behavioural disorders and stress in this bird species, and could also help in their captive management.

Measuring fecal testosterone in females and fecal estrogens in males: comparison of RIA and LC/MS/MS methods for wild baboons (Papio cynocephalus)

The development of non-invasive methods, particularly fecal determination, has made possible the assessment of hormone concentrations in wild animal populations. However, measuring fecal metabolites needs careful validation for each species and for each sex. We investigated whether radioimmunoassays (RIAs) previously used to measure fecal testosterone (fT) in male baboons and fecal estrogens (fE) in female baboons were well suited to measure these hormones in the opposite sex. We compared fE and fT concentrations determined by RIA to those measured by liquid chromatography combined with triple quadropole mass spectrometry (LC/MS/MS), a highly specific method. Additionally, we conducted a biological validation to assure that the measurements of fecal concentrations reflected physiological levels of the hormone of interest. Several tests produced expected results that led us to conclude that our RIAs can reliably measure fT and fE in both sexes, and that within-sex comparisons of these measures are valid: (i) fTRIA were significantly correlated to fTLC/MS/MS for both sexes; (ii) fTRIA were higher in adult than in immature males; (iii) fTRIA were higher in pregnant than non-pregnant females; (iv) fERIA were correlated with 17β-estradiol (fE2) and with estrone (fE1) determined by LC/MS/MS in pregnant females; (v) fERIA were significantly correlated with fE2 in non-pregnant females and nearly significantly correlated in males; (vi) fERIA were higher in adult males than in immature males. fERIA were higher in females than in males, as predicted, but unexpectedly, fTRIA were higher in females than in males, suggesting a difference in steroid metabolism in the two sexes; consequently, we conclude that while within-sex comparisons are valid, fTRIA should not be used for intersexual comparisons. Our results should open the field to important additional studies, as to date the roles of testosterone in females and estrogens in males have been little investigated.

Longitudinal monitoring of sex steroid hormones in excrement of spectacled eiders (Somateria fischeri)

From the 1970s to the 1990s, the breeding population of spectacled eiders (Somateria fischeri) in western Alaska declined by 96%, which led to the listing of this species as threatened under the Endangered Species Act in 1993. Since then, the population has stabilized, but has not recovered to pre-decline numbers. While little is known about reproductive endocrinology in spectacled eiders, in other avian species, estrogen and testosterone are known to initiate and modulate various reproductive processes including yolk protein synthesis, reproductive behaviors and secondary sex characteristics. Measurement of the metabolites of estrogen and testosterone (EM and TM, respectively) in excrement reflect circulating hormone concentrations and provide a non-invasive method to monitor reproductive physiology. We measured concentrations of excreted EM in captive females and TM in males to (1) determine the efficacy of commercially available radioimmunoassay kits to detect EM and TM, (2) describe annual profiles of EM and TM concentrations, and (3) define the reproductive season of captive spectacled eiders using endocrine status. Excrement samples were collected from captive female and male spectacled eiders three times per week throughout 1 year. Female EM and male TM levels were quantified using radioimmunoassay. Mean female EM profile exhibited values exceeding the threshold for "peak" values (EM>193.3 ng/g) from mid-February to early July, and again in September. Additionally, the highest average concentrations of EM were seen in March, May and September. Elevated TM concentrations occurred in mid March, mid May and late June. These data suggest that levels of excreted sex steroids reflect patterns predicted by breeding landmarks in the annual cycle and will assist in field monitoring and captive breeding programs for spectacled eiders.

Validation of a fecal glucocorticoid metabolite assay to assess stress in the budgerigar (Melopsittacus undulatus)

The budgerigar (Melopsittacus undulatus) is a small parrot native to Australia that is commonly held in zoos, laboratories, and private homes. Assessment of budgerigar stress levels would aid welfare monitoring and improve our understanding of their biology. Analyzing fecal glucocorticoid metabolites provides a noninvasive method to measure stress levels in birds. For this method to be reliable, the antibody to be used in an immunoassay must be carefully selected for each species, and validation must be performed. A common limitation in many existing assays is the inability to accurately detect variable fecal glucocorticoid metabolites in minute quantities of feces, requiring small samples to be combined. We have developed a double antibody radioimmunoassay protocol based on a commercially available (125) I-corticosterone radioimmunoassay kit for use in detecting fecal glucocorticoid metabolites in small quantities (<20 mg) of budgerigar droppings. The assay was validated pharmacologically with an adrenocorticotropic hormone challenge and with oral administration of corticosterone. Our validation has demonstrated our assay is both sensitive and a reliable approach to noninvasive monitoring of stress in budgerigars.

Do glucocorticoids in droppings reflect baseline level in birds captured in the wild? A case study in snow geese

Baseline glucocorticoid (CORT) levels in plasma are increasingly used as physiological indices of the relative condition or health of individuals and populations. The major limitation is that CORT production is stimulated by the stress associated with capture and handling. Measuring fecal CORT is one way to solve this problem because elevation of fecal CORT usually does not occur before 1-12h after a stressful event in captive animals. However, the effect of capture and handling on fecal CORT levels has seldom been investigated in the wild. In a first experiment, we validated that fecal CORT levels starts to increase in droppings (a mixture of fecal and urinary material) about 1-2h following injection of CORT-release hormone (ACTH) in captive greater snow geese (Chen caerulescens atlantica). In a second experiment, we investigated whether dropping and plasma CORT were related and if the capture affected fecal CORT levels in wild birds. Baseline CORT was obtained by bleeding individuals within 4 min after capture. No relationship was found between baseline and CORT in droppings shortly after capture (<4 min). In addition, CORT levels in droppings increased linearly with time after capture and was already elevated by a factor two 40 min after capture. The different turnover time of CORT between urine and feces could explain such results. We conclude that droppings cannot provide an index of basal CORT levels in snow geese captured in the wild. Such a result contrast with previous studies conducted on habituated, captive animals. We thus recommend that use of droppings as a non-invasive technique to measure baseline CORT be restricted to non-manipulated individuals in the wild.

Measuring stress in wildlife: techniques for quantifying glucocorticoids

Stress responses play a key role in allowing animals to cope with change and challenge in the face of both environmental certainty and uncertainty. Measurement of glucocorticoid levels, key elements in the neuroendocrine stress axis, can give insight into an animal's well-being and can aid understanding ecological and evolutionary processes as well as conservation and management issues. We give an overview of the four main biological samples that have been utilized [blood, saliva, excreta (feces and urine), and integumentary structures (hair and feathers)], their advantages and disadvantages for use with wildlife, and some of the background and pitfalls that users must consider in interpreting their results. The matrix of choice will depend on the nature of the study and of the species, on whether one is examining the impact of acute versus chronic stressors, and on the degree of invasiveness that is possible or desirable. In some cases, more than one matrix can be measured to achieve the same ends. All require a significant degree of expertise, sometimes in obtaining the sample and always in extracting and analyzing the glucocorticoid or its metabolites. Glucocorticoid measurement is proving to be a powerful integrator of environmental stressors and of an animal's condition.

Female androgen patterns and within-pair testosterone compatibility in domestic geese (Anser domesticus)

For successfully raising offspring, long-term monogamous pair partners need to be behaviorally and hormonally coordinated. In the monogamous, biparental greylag geese (Anser anser) a dyadic pairbond-specific measure, 'within-pair testosterone compatibility' (TC) indicated how closely synchronized are seasonal androgen levels, which co-varied with reproductive output. Males, in particular, were assumed to respond to their females' hormonal and fecundity phases. We now present experiments with biparental domestic geese (Anser domesticus) kept as pairs to ask whether TC occurs also in these generally polygynous animals. We further ask how different conditions of mate choice affect TC and whether established TC is maintained during a polygynous flock situation. We measured androgen metabolites (AM) non-invasively from individual droppings. In females, AM was related with gonadal activity as it increased after GnRH but not ACTH challenge. Females with preferred partners had higher maximum AM during egg laying and higher rates of initiating incubation than randomly paired females. Domestic ganders had seasonal AM patterns typical for polygynous males. Within-pair TC ranged from almost perfectly positive to non-correlated in domestic geese but mate choice did not explain TC variation. TC of previous pairs was generally reduced in the flock situation, probably confounded by factors of the social environment, i.e. mating opportunity and availability of multiple partners. On top of the underlying reproductive physiology our results suggest two episodic components of TC: a female androgen responsiveness to the preferred partner at least during egg formation, and the male's facultative potential to respond to her readiness to breed.

Dyadic relationships and operational performance of male and female owners and their male dogs

In the paper we investigate how owner personality, attitude and gender influence dog behavior, dyadic practical functionality and the level of dog salivary cortisol. In three meetings, 12 female and 10 male owners of male dogs answered questionnaires including the Neo-FFI human personality inventory. Their dyadic behavior was video-taped in a number of test situations, and saliva samples were collected. Owners who scored highly in neuroticism (Neo-FFI dimension one) viewed their dogs as social supporters and spent much time with them. Their dogs had low baseline cortisol levels, but such dyads were less successful in the operational task. Owners who scored highly in extroversion (Neo-FFI dimension two) appreciated shared activities with their dogs which had relatively high baseline cortisol values. Dogs that had female owners were less sociable-active (dog personality axis 1) than dogs that had male owners. Therefore, it appears that owner gender and personality influences dyadic interaction style, dog behavior and dyadic practical functionality.

Fecal glucocorticoid metabolites of experimentally stressed captive and free-living starlings: implications for conservation research

Fecal glucocorticoid metabolite (FGM) analysis has received considerable attention in conservation biology because it has potential to be used as a noninvasive measure of stress in animals. There has been a recent and extensive literature describing the importance of technical, physiological, and biological validations of this technique, yet surprisingly little is known about how FGM concentrations change during chronic stress. Therefore, we experimentally induced chronic stress in both captive and free-living European starlings (Sturnus vulgaris). Chronic stress was elicited using a rotation of four different 30 min acute stressors for 16 days in the laboratory and 8 days in the field. Exogenous ACTH, the primary glucocorticoid secretagog, significantly increased FGM concentrations in approximately 2 h, and our assay detected endogenous diel glucocorticoid rhythms similar to those of other birds. Thus, our assay was both physiologically and biologically validated. However, experimentally induced chronic stress did not alter daytime or nighttime FGM concentrations in captive starlings. In contrast, chronically stressed adult female starlings had higher FGM concentrations than unstressed female starlings in the field. Our field data support the general assumption that higher FGM concentrations indicate chronic stress, but our captive data do not. Overall, our results suggest that more research is need before FGM analysis can be used as a reliable measure of stress in animals, especially those kept in captivity.

Annual pattern of fecal corticoid excretion in captive Red-tailed parrots (Amazona brasiliensis)

Annual patterns of fecal corticoid excretion were analyzed in the threatened Red-tailed parrot (Amazona brasiliensis) in captivity. Corticoid concentration over the 15 months of the study (mean +/- standard error, 12.6 +/- 0.32 ng g(-1), n = 585) was lowest around May (the southern Fall), and greatest around September (late winter), just prior to their normal breeding period. Corticoid excretion follows a seasonal pattern best explained by reproductive cycles rather than climate, although climate may be involved in the timing of corticoid excretion. Fecal corticoids also show promise as a tool to measure stress levels. We demonstrate that fecal corticoid measurement is a simple, yet efficient method for monitoring adrenocortical activity in captive, and perhaps wild, parrots. Monitoring adrenocortical activity can inform researchers about imposed stress in captivity, whether pair-bonds are forming in captive birds, and of the timing of breeding both in captivity and in nature.

Corticosterone excretion patterns and affiliative behavior over development in ravens (Corvus corax)

Averse effects of social stress may be buffered by the presence of social allies, which mainly has been demonstrated in mammals and recently also in birds. However, effects of socio-positive behavior prior to fledging in relation to corticosterone excretion in altricial birds have not been investigated yet. We here monitored corticosterone excretion patterns in three groups of hand raised juvenile ravens (n=5, 6 and 11) in the nest, post-fledging (May-July) and when ravens would be independent from their parents (September-November). We related these corticosterone excretion patterns to socio-positive behavior. Behavioral data were collected via focal sampling in each developmental period considered. We analyzed amounts of excreted immunoreactive corticosterone metabolites (CM) using enzyme immuno assays. We collected fecal samples in each developmental period considered and evaluated the most appropriate assay via an isolation stress experiment. Basal CM was significantly higher during the nestling period than post-fledging or when birds were independent. The time nestlings spent allopreening correlated negatively with mean CM. Post-fledging, individuals with higher CM levels sat close to (distance <50 cm) conspecifics more frequently and tended to preen them longer. When birds were independent and a stable rank hierarchy was established, dominant individuals were preened significantly longer than subordinates. These patterns observed in ravens parallel those described for primates, which could indicate that animal species living in a complex social environment may deal with social problems in a similar way that is not restricted to mammals or primates.

Noninvasive monitoring of hormones in bird droppings: physiological validation, sampling, extraction, sex differences, and the influence of diet on hormone metabolite levels

During the past several years, the noninvasive measurement of steroid metabolites from mammalian feces and bird droppings has become more and more popular. With an increasing acceptance of the method, investigators may become less aware of the need to validate their assays. It is shown why such validations are essential for each new species investigated and various ways to physiologically validate such noninvasive methods are described. Using the European stonechat (Saxicola torquata rubicola) as a model, it is explained why a validated method to measure androgen metabolites in males does not necessarily work in females. In addition the difficulties that may be neglected owing to the superficial ease of sampling and processing of excreta are investigated. Various issues that may arise during sampling, storage, and extraction of excreta are addressed. Finally, results suggesting that experimental manipulations of the diet may affect hormone metabolite levels in European stonechats are presented. So far, only a few studies have investigated the impact of diet on hormone metabolite levels, and these are the first data to report such an impact in birds. More studies are urgently needed to learn more about differences between the sexes, individuals, and populations and the impact of diet and energy metabolism on hormone metabolites.