Faecal Cortisol Metabolites Research Articles

Exploring hair cortisone concentration as a novel tool to assess chronic stress in sheep with tick-borne fever

Tick-borne fever (TBF), caused by the bacterium Anaplasma phagocytophilum and transmitted by the tick Ixodes ricinus, has considerable consequences for animal welfare and economy in the sheep industry. Non-invasive, objective methods to quantify chronic stress are needed in order to evaluate the welfare impact of disease. The aim of this study was 1) to evaluate hair cortisol (HC) and hair cortisone (HCn) as biomarkers of chronic stress in sheep with TBF and 2) to test whether there was an association between the development of TBF and concentrations of HC, HCn and faecal cortisol metabolites (FCM) and body weight. The experiment took place in an area with a high prevalence of TBF, and thirty lambs were used in the study. Wool samples were collected in Week 0, in Week 3 (before turn out on homeland spring pasture), in Week 6 (before turn out on summer rangeland pasture) and at the end of the summer (Week 15). Faecal samples were collected every week (ie. Week 0–6 and Week 15). Symptoms of TBF developed in 15 lambs, of which all recovered from the disease after treatment with antibiotics. HC levels decreased progressively, and significantly, between Week 0, 3, 6 and 15 (p < 0.001), while HCn only decreased from Week 0 to Week 3 (p < 0.001) and then remained stable between Week 3–15. FCM increased between Week 0 and 5 (p = 0.027), and a significant association was found between increased FCM levels in Week 5 and lambs developing clinical signs of TBF (p = 0.022). We also found an association between lambs developing clinical signs of TBF and elevated HCn levels in Week 6 (p = 0.013). A slightly lower weight gain at later time points (Week 6 and 15) were found in the affected lambs compared to clinically healthy lambs. Our results indicate local production and/or metabolism of glucocorticoids in the hair follicles. This study strengthens our previous finding of a potential merit of hair cortisone as a biomarker of chronic stress in sheep.

Herd-level associations between human–animal relationship, management, fecal cortisol metabolites, and udder health of organic dairy cows

Impact patterns of human-animal relationship (HAR) and herd stress level on udder health were investigated in a cross-sectional study on 30 German and Danish organic dairy herds also taking into account influencing factors regarding housing and management. Cow behavior (avoidance distance, tolerance to tactile interaction, release behavior) was assessed in tests, milkers' behavior recorded during milking, and information about contacts with animals during routine work gathered by interview. Additionally, stockpersons' attitudes were recorded via questionnaires. Fecal cortisol metabolites were measured in approximately 30 focal cows on each farm and used as a proxy to determine the level of distress within the herd. Management and housing were assessed on-farm. The following herd udder health indicators were calculated: the prevalence of mastitis quarters (≥100,000 cells/mL), and, from milk recording data over 1 yr retrospectively, the average somatic cell score and the self-cure rates during lactation per herd. Multivariable regression models with stepwise selection were calculated at herd level. The following HAR-related factors were associated with better udder health (in at least 1 of the final models): stockpersons' higher agreement on patience being important when moving the cows and on necessary contact to cows being pleasant, higher amount of positive interactions with cows during milking, more docile cows in the release behavior test, no routine change of milkers, more contact time during routine work, no active heifer habituation to milking, and performance of barn controls beyond routine work. Lower fecal cortisol metabolite levels were related to higher self-cure rates during lactation. Concerning housing, management, and herd characteristics, the following known factors were related to impaired udder health for at least 1 of the indicators: straw yards, automatic milking system, higher average lactation number, and less antibiotic udder treatments. The results confirm earlier findings that HAR is associated with udder health and should therefore be considered in future research and mastitis control programs. First indications of negative associations between herd stress level and mastitis curing capacity should be followed up in future studies.

A new large-scale index (AcED) for assessing traffic noise disturbance on wildlife: stress response in a roe deer (Capreolus capreolus) population.

Anthropogenic noise is a growing ubiquitous and pervasive pollutant as well as a recognised stressor that spreads throughout natural ecosystems. However, there is still an urgent need for the assessment of noise impact on natural ecosystems. This article presents a multidisciplinary study which made it possible to isolate noise due to road traffic to evaluate it as a major driver of detrimental effects on wildlife populations. A new indicator has been defined: AcED (the acoustic escape distance) and faecal cortisol metabolites (FCM) were extracted from roe deer faecal samples as a validated indicator of physiological stress in animals moving around in two low-traffic roads that cross a National Park in Spain. Two key findings turned out to be relevant in this study: (i) road identity (i.e. road type defined by traffic volume and average speed) and AcED were the variables that best explained the FCM values observed in roe deer, and (ii) FCM concentration was positively related to increasing traffic volume (road type) and AcED values. Our results suggest that FCM analysis and noise mapping have shown themselves to be useful tools in multidisciplinary approaches and environmental monitoring. Furthermore, our findings aroused the suspicion that low-traffic roads (< 1000 vehicles per day) could be capable of causing higher habitat degradation than has been deemed until now.

Effects of dietary energy level and intake of corn by-product-based diets on newly received growing cattle: antibody production, acute phase protein response, stress, and immunocompetency of healthy and morbid animals.

Effects of dietary energy level and intake of corn by-product-based diets on antibody production, acute phase protein response, stress, and immunocompetency of healthy and morbid newly received growing cattle were evaluated. Four dietary treatments were formulated to supply 0.99, 1.10, 1.21, and 1.32 Mcal NEg/ kg DM and were offered at 100%, 95%, 90%, and 85% of ad libitum based on 0.99/100 treatment intake, respectively. Thirty-two pens were utilized with approximately 12 animals/pen. Four animals from each pen (32/dietary treatment) were randomly selected and used to serve as a subset to monitor immune function and acute phase proteins following a split-plot design. In addition, two animals were randomly and independently selected from each pen (16/dietary treatment) and used to measure fecal cortisol metabolite. Additionally, animals removed from the pen one (M1), two (M2), or three (M3) times and classified as morbid were bled in conjunction with a healthy control (H) removed at the same time and the serum analyzed for the same parameters. A quadratic response to time (P < 0.01) was detected for haptoglobin concentrations and for antibody titers for bovine viral diarrhea type 1 (BVD-I) and infectious bovine rhinotracheitis (IBR; P < 0.01). Haptoglobin was lowest on arrival, highest on day 14, and similar to baseline levels by day 27. Titer levels for BVD-I and IBR were lowest on arrival, higher on day 14, and significantly higher on day 27. Titers for bovine viral diarrhea type 2 (BVD-II) responded linearly (P < 0.05) with lower levels on arrival and highest levels on day 27. Haptoglobin was elevated in morbid animals compared to healthy pen mates (P < 0.05). Titer levels for BVD-I and IBR were also higher in healthy animals compared to animals pulled for morbidity (P < 0.01). Fecal cortisol was higher on arrival than on day 14 (P < 0.05). Dietary treatment had no effect on any of the parameters investigated. In summary, high-energy receiving diets based on fermentable fiber from by-products can be fed to newly received growing cattle without negative effects on antibody production toward vaccines, inflammation, or overall stress. In addition, haptoglobin concentrations and titer levels for BVD-I and IBR viruses are higher in healthy animals compared to sick animals.

Dorsal shaving affects concentrations of faecal cortisol metabolites in lactating golden hamsters

Breeding of golden hamsters is classically performed at thermal conditions ranging from 20 to 24 °C. However, growing evidence suggests that lactating females suffer from heat stress. We hypothesised that shaving females dorsally to maximise heat dissipation may reduce stress during reproduction. We thus compared faecal cortisol metabolites (FCM) from shaved golden hamster mothers with those from unshaved controls. We observed significantly lower FCM levels in the shaved mothers (F1,22 = 8.69, p = 0.0075) pointing to lower stress due to ameliorated heat dissipation over the body surface. In addition, we observed 0.4 °C lower mean subcutaneous body temperatures in the shaved females, although this effect did not reach significance (F1,22 = 1.86, p = 0.18). Our results suggest that golden hamsters having body masses being more than four times that of laboratory mice provide a very interesting model to study aspects of lactation and heat production at the same time.

Seasonal changes of faecal cortisol metabolite levels in Gracilinanus agilis (Didelphimorphia: Didelphidae) and its association to life histories variables and parasite loads.

The aim of this study was to evaluate the role of environmental (dry versus wet season) and individual (sex, body mass and reproductive status) factors in the levels of faecal cortisol metabolites (FGCs) in Gracilinanus agilis faecal samples as an index of stress levels in this species; as well as its association with abundance of Eimeria spp, as an indicator of immunocompetence against parasites. Our study found that FGCFGCs are a reliable indicator of adrenal activity in G. agilis. We found that FGCFGCs increase considerably by environmental stressors like the dry season. Moreover, the observed positive association between FGCs and body mass is the result of the effect of season and reproduction in both variables. We also demonstrated that an increase in FGC levels among G. agilis during the dry season is associated with a rise in the probability of being infected by Eimeria spp. Hence, our finding supports the corticosteroid-fitness hypothesis, which predicts that increased glucocorticoids as a response to stressors usually results in decreased fitness of individuals, translated into low future survival and reproductive success, and higher parasite infection. To our knowledge, this is the first study that integrates environmental changes, hormone responses and parasite loads in a US marsupial in both empirical and experimental approaches.

Heat stress in cows at pasture and benefit of shade in a temperate climate region.

Under temperate climates, cattle are often at pasture in summer and are not necessarily provided with shade. We aimed at evaluating in a temperate region (Belgium) to what extent cattle may suffer from heat stress (measured through body temperature, respiration rate and panting score, cortisol or its metabolites in milk, and feces on hot days) and at assessing the potential benefits of shade. During the summer of 2012, 20 cows were kept on pasture without access to shade. During the summer of 2011, ten cows had access to shade (young trees with shade cloth hung between them), whereas ten cows had no access. Climatic conditions were quantified by the Heat Load Index (HLI). In animals without access to shade respiration rates, panting scores, rectal temperatures, and milk cortisol concentrations increased as HLI increased in both 2011 and 2012. Fecal cortisol metabolites varied with HLI in 2011 only. When cattle had access to shade, their use of shade increased as the HLI increased. This effect was more pronounced during the last part of the summer, possibly due to better acquaintance with the shade construction. In this case, shade use increased to 65% at the highest HLI (79). Shade tempered the effects on respiration, rectal temperature, and fecal cortisol metabolites. Milk cortisol was not influenced by HLI for cows using shade for > 10% of the day. Therefore, even in temperate areas, cattle may suffer from heat when they are at pasture in summer and providing shade can reduce such stress.

Levels of plasma and fecal glucocorticoid metabolites following an ACTH challenge in male and female coyotes (Canis latrans).

Knowledge of endocrine stress responses can be advantageous for understanding how animals respond to their environment. One tool in wildlife endocrinology is to measure the adrenocortical activity as a parameter of disturbance of animals. Fecal glucocorticoid metabolites (GCMs) provide a noninvasive assessment of adrenocortical activity. Using an adrenocorticotropic hormone (ACTH) challenge administered to 28 captive coyotes (Canis latrans), we measured the levels of plasma cortisol, and fecal cortisol and corticosterone metabolites (i.e., GCMs). Our goal was to determine the dose-response in the plasma and fecal samples following the injection and determine if there were effects of sex, age, and time of day. Specifically, animals were anesthetized for ~ 90min with treatment animals intravenously injected with exogenous ACTH and control animals receiving saline. We collected blood samples prior to injection and at 4 different time points post-injection. We also collected fecal samples 2days pre- and 2days post-injection to measure fecal GCMs and determine if an endocrine stress response could be detected in fecal samples. We found a definite response in cortisol levels in the plasma for coyotes to the ACTH challenge. There was a response in fecal corticosterone 1day post-injection, but the control males showed a similar response indicating a handling effect. Fecal cortisol levels did not indicate a response to the ACTH challenge, and were significantly lower than corticosterone concentrations. We also found significant sex, but not age or diurnal, differences in fecal GCMs. Radioimmunoassays for fecal corticosterone levels appeared to be a reliable indicator of physiological stress in coyotes.

Validation of an Enzyme Immunoassay for Measuring Fecal Cortisol Metabolites of Bearded (Sapajus libidinosus) and Black (Sapajus nigritus) Capuchins

Fecal steroid analysis is a powerful noninvasive tool for behavioral endocrinology, but enzyme immunoassays (EIAs) require experimental validation before they are applied. We conducted a physiological validation of an in-house EIA measuring fecal cortisol metabolites (FCMs) by performing an adrenocorticotrophic hormone (ACTH) challenge, dexamethasone suppression, and control saline solution injection experiment with six male and five female bearded capuchins (Sapajus libidinosus). We also took advantage of a presumably stressful incident to perform a biological validation for females. In addition, we conducted high-performance liquid chromatography (HPLC) immunograms to characterize the FCMs measured in both sexes of bearded capuchin, and in a closely related species (S. nigritus, black capuchin monkeys). Male and female S. libidinosus showed FCM peaks after ACTH injections, and females also showed FCM peaks in the biological validation. Three of four individuals (two males and one female) had an FCM peak shortly after injection of dexamethasone and both sexes then showed prolonged low FCM levels after dexamethasone injection. We observed no effects of saline solution injections. The time to peak FCM excretion after ACTH injection or a stressful incident varied 1.5–8.5 h. HPLC results revealed no differences in FCM profiles between sexes or species and suggest that the EIA can also be used in male and female S. nigritus. Our results validate an in-house EIA for both sexes of S. libidinosus but show large individual variation in FCM excretion, which highlights the need for carefully planned feces collection in endocrinologial research.

Variations in aggression and activity levels amongst squirrels inhabiting low and high density areas

AbstractVariation in an individual animal's behavioural traits has been observed in a wide range of species and is believed to have important fitness consequences. As part of a larger study, it was observed that squirrels occurred at different densities on a 315 ha island, and this subsequently led to variations in faecal cortisol metabolite levels. This study aimed to examine whether living at different densities would also lead to variations in activity and aggression levels and in their survival probability, breeding and body condition. In order to examine variations in activity and aggression, behavioural tests (open field test, mirror image stimulation, breath rates and struggle rate tests) were conducted on 32 individuals (15♀, 17♂), a total of 69 times. Activity in the wild was investigated through radio tracking. There was a significant correlation between the time a squirrel was active and in their aggressive behaviour during the behavioural tests, with more aggressive individuals also being more active. Squirrels in the low density area spent a greater proportion of time active and engaged in aggressive behaviour in the open field test but also moved further in the wild and had a lower breath rate and higher struggle rates. Squirrels in the high density area were the least aggressive, had a smaller home range and higher breath and lower struggle rates. However, this was found to have no effect on survival probability, breeding or body condition. These variations may be the result of sampling dispersing squirrels.

Low plasma cortisol and fecal cortisol metabolite measures as indicators of compromised welfare in domestic horses (Equus caballus).

The hypothalamic-pituitary-adrenal (HPA) axis response to chronic stress is far from straight forward, particularly with regards to animal welfare. There are reports of no effect as well as both decreases and increases in cortisol after chronic stressors. Therefore, the first aim of the present study was to determine how measures of compromised welfare, such as chronic pain and haematological anomalies, related to cortisol levels in domestic horses (Equus caballus). Domestic horses are an informative model to investigate the impact of chronic stress (due to environment, pain, work, housing conditions…) on the HPA axis. The second aim was to determine whether levels of fecal cortisol metabolites (FCM) may be used as an indicator of welfare measures. The present study used fifty-nine horses (44 geldings and 15 mares), from three riding centres in Brittany, France. The primary findings show that horses whose welfare was clearly compromised (as indicated by an unusual ears backward position, presence of vertebral problems or haematological anomalies, e.g. anaemia) also had lower levels of both FCM and plasma cortisol. This work extends our previous findings showing that withdrawn postures, indicators of depressive-like behavior in horses, are associated with lower plasma cortisol levels. We also found that evening plasma cortisol levels positively correlated with FCM levels in horses. Future research aims to determine the extent to which factors of influence on welfare, such as living conditions (e.g. single stalls versus group housing in pasture or paddocks), early life factors, and human interaction, act as mediators of cortisol levels in horses.

Faecal cortisol metabolites as an indicator of adrenocortical activity in farmed silver foxes (Vulpes vulpes)

Measuring glucocorticoid metabolites in faeces has proven a useful, non-invasive method to monitor adrenocortical activity in several farm and wild species. Unlike plasma cortisol, whose sampling requires restraint and blood draws, faecal cortisol metabolites (FCM) may be particularly suitable for farmed silver foxes as these animals are sensitive to handling by humans. Prior to using FCM as a potential indicator of stress in silver foxes, however, a proper physiological and/or biological validation is required. Here, we determined FCM concentrations in 30 silver foxes (10 adult vixens, 10 juvenile females and 10 juvenile males) every alternate hour for 24h after 1) an increase in cortisol induced by injection with synthetic ACTH (hereafter ACTH), and 2) a 2min period of handling and restraint. Baseline FCM values, recorded every fourth hour for 24h before the ACTH and handling treatments, served as controls. FCM values increased significantly following ACTH injection (P=0.0001) and handling (P<0.0001). The time to reach peak FCM concentrations after ACTH injection tended to differ between groups (P=0.055) averaging (±SE) 11.0±1.04, 10.6±1.30 and 7.8±0.20h for vixens, juvenile females and juvenile males, respectively. After handling, peak FCM values were reached after 10.1±0.55h with no significant differences between groups. Peak concentrations averaged 2143±264ng/g after the ACTH and 1008±128ng/g after handling, compared to 475±48ng/g for baseline levels. Peak FCM values tended to vary between individuals more in females than in males. Baseline FCM concentrations prior to handling were, unexpectedly, higher in more confident foxes (P=0.004), a finding perhaps indicating a potential preparative role of cortisol in silver foxes. There was also a negative trend between foxes’ confidence and their times to reach peak FCM concentrations after handling (P=0.062), suggestive of a prolonged adrenocortical activation in more fearful individuals. Based on the rates that foxes produce faecal samples and the times to reach maximum FCM concentrations, we suggest a four hour delay to first faeces collection, before collecting samples every third hour the next 12 following hours to monitor elevations after an acute stressor. Our study confirms faecal cortisol metabolites as a valid indicator of adrenocortical activity in farmed silver foxes.

Comparison of pens without and with multilevel platforms for growing rabbits

This experiment compared the productive performance and location of growing rabbits in pens without and with two-level platforms (wire-mesh or plastic-mesh). A total of 174 rabbits of both sexes weaned at 5 weeks of age were randomly divided into three groups (n = 58 rabbits/group, 2 pens/treatment, 29 rabbits/pen). The floor area of pens was 1.0 × 1.83 m, and the floor was made of wire-mesh. Two pens were equipped with wire-mesh (WP) and two pens with plastic-mesh elevated platforms (PP) on two levels, and two pens were without platforms (NoP). Treatment had no effect on the productive performance of growing rabbits. Based on video recordings, animal density (rabbits/m2 in each location) was higher (p < .001) on the floor than on the platforms (in WP: 12.0 vs. 5.2, in PP: 10.2 vs. 7.4 rabbits/m2, respectively). Animal density on the floor was higher (p < .001) in front of the platforms than under the platforms (in WP 15.7 vs. 9.8 rabbits/m2 and in PP 13.3 vs. 8.3 rabbits/m2, respectively). The animal density on platforms was 1.4 times higher in group of PP than in WP (p < .001). The animal density was 1.6 and 2.9 times higher on the second floor than on the first one (p < .001), in group of PP and WP, respectively. The concentration of cortisol metabolites in faeces and the ratio of injured rabbits were similar in the three groups. The rabbits showed higher preference staying on the floor compared to the platform. Pens with platforms were not influencing productive performance.

Managed parks as a refuge for the threatened red squirrel (Sciurus vulgaris) in light of human disturbance

As the invasive grey squirrel continues to spread, red squirrels are dying out. The result may be isolated populations in managed parks, where access can be controlled. However, recreation can often have a negative effect on wildlife, reducing the conservation potential of parks. Fota Wildlife Park receives over 300,000 visitors each year and is located on an island that is currently free of grey squirrels. We examined the effect of visitors on the existing red squirrel population. Sampling was conducted in the presence and absence of the public. Ten trapping sessions took place from March 2013 to 2014 and faeces were collected to examine stress levels. Squirrels were observed to concentrate their activity in non-public areas and move into public areas when the park was closed. Radio tracked squirrels, from the adjacent gardens (intermediate disturbance), also used habitats in the wildlife park (high disturbance) when it was closed but returned when the park had opened. When squirrels were observed in public areas, visitors were only visible on 15% of occasions. Levels of faecal cortisol metabolites (FCM) were highest in areas where human disturbance was greatest. However, there was no correlation between visitor numbers and the stress levels of squirrels. FCM levels were however, positively correlated with density of squirrels. The fact that high numbers of squirrels continued to utilise the wildlife park demonstrates that managed parks could provide an important reserve for the maintenance of the species, as long as non-public areas are accessible.

Clinical parameters and adrenocortical activity to assess stress responses of alpacas using different methods of restraint either alone or with shearing

Shearing of alpacas is stressful and is undertaken by restraint in the standing position, cast on the floor or on a tilt table. The objectives of the study were to...

Evaluating Stress Physiology and Parasite Infection Parameters in the Translocation of Critically Endangered Woylies (Bettongia penicillata).

Translocation can be stressful for wildlife. Stress may be important in fauna translocation because it has been suggested that it can exacerbate the impact of infectious disease on translocated wildlife. However, few studies explore this hypothesis by measuring stress physiology and infection indices in parallel during wildlife translocations. We analysed faecal cortisol metabolite (FCM) concentration and endoparasite parameters (nematodes, coccidians and haemoparasites) in a critically endangered marsupial, the woylie (Bettongia penicillata), 1-3months prior to translocation, at translocation, and 6months later. FCM for both translocated and resident woylies was significantly higher after translocation compared to before or at translocation. In addition, body condition decreased with increasing FCM after translocation. These patterns in host condition and physiology may be indicative of translocation stress or stress associated with factors independent of the translocation. Parasite factors also influenced FCM in translocated woylies. When haemoparasites were detected, there was a significant negative relationship between strongyle egg count and FCM. This may reflect the influence of glucocorticoids on the immune response to micro- and macro-parasites. Our results indicate that host physiology and infection patterns can change significantly during translocation, but further investigation is required to determine how these patterns influence translocation success.

Validation of an enzyme immunoassay and comparison of fecal cortisol metabolite levels in black and gold howler monkeys (Alouatta caraya) inhabiting fragmented and continuous areas of the humid Chaco region, Argentina.

Validation of an enzyme immunoassay and comparison of fecal cortisol metabolite levels in black and gold howler monkeys (Alouatta caraya) inhabiting fragmented and continuous areas of the humid Chaco region, Argentina. Contrary to our initial prediction, no significant differences in Alouatta caraya fecal cortisol metabolite levels were detected; cortisol metabolites were significantly higher in females. Probably, animals adjusted their diet to cope with feeding in degraded habitats, but with new leaves and buds.

Identifying factors that influence stress physiology of the woylie, a critically endangered marsupial

AbstractFaecal glucocorticoid metabolites are minimally invasive stress physiology indices that can be used to understand how animals respond to physical and/or psychological challenges (stressors) and inform how to optimize conservation management in view of these stressors. We investigated contextual biological, environmental and parasitological factors influencing variation in baseline faecal cortisol metabolite (FCM) concentration in a critically endangered marsupial, the woylie (syn. brush‐tailed bettong, Bettongia penicillata). Woylies have undergone a rapid and significant population decline, with environmental stressors exacerbating disease suggested to contribute to these ongoing declines. We conducted a longitudinal field study of 15 adult woylies (9 females, 6 males) in a captive, naturalistic facility. FCM concentration in faecal samples (n = 269) collected monthly over 20 months was quantified by enzyme immunoassay in parallel with measures of body condition, sex, season, female reproductive status and the presence of endoparasites and ectoparasites. Linear mixed effect modelling revealed a significant effect of season, sex, body condition index and nematode parasite status on FCM. Overall, mean FCM was lowest in summer and highest in autumn and winter, and females had higher mean FCM than males. There was a significant but weak negative association between body condition and FCM. When woylies were shedding oxyurid nematode eggs they had higher mean FCM compared to when they were not shedding. In future, knowledge of factors that influence FCM fluctuations in woylies may be considered when carrying out potentially stressful conservation interventions that may influence the future survival of this unique and threatened species.

Relocation stress induces short-term fecal cortisol increase in Tonkean macaques (Macaca tonkeana).

The level of glucocorticoids, especially if obtained from noninvasive sampling, can be used as an index of animal well-being, allowing evaluation of the animal's response to environmental modifications. Despite evidence that these hormones play a relevant role in energy metabolism regulation in perceived or real stress events, little is known regarding the factors that could modify the capability of animals to cope with relocation events. The aim of this research was to assess fecal cortisol metabolite concentrations before, during and after acute stress (transfer and relocation event) in two well-established social groups of Tonkean macaques (Macaca tonkeana). The results showed that the fecal levels of cortisol increased in individuals of both groups in response to the stress event, with a similar trend in males and females. Hormone levels were back to baseline values in both groups a few days after transfer and relocation. The presence of known social partners could be one of the factors that possibly facilitated the adaptation process.

Applicability of Commercially Available ELISA Kits for the Quantification of Faecal Immunoreactive Corticosterone Metabolites in Mice.

Commercially available ELISA kits are popular among investigators that quantify faecal corticosterone or cortisol metabolites (FCM) for stress assessment in animals. However, in faeces, these assays mainly detect immunoreactive glucocorticoid metabolites. Since different assays contain antibodies of different origin, the detection level and cross-reactivity towards different metabolites and other steroids differ considerably between assays. Thus, the validity of one assay for FCM quantification in stress assessment is not necessarily the same for another assay. The present study was designed to investigate corticosterone (CORT) in serum and FCM levels in faeces of laboratory mice, as quantified in four different ELISA kits (DRG EIA-4164, Demeditec DEV9922, Enzo ADI-900-097 and Cayman EIA kit 500655). Assay kits were chosen based on the origin of the antibody, detection level and variation in cross-reactivity. As expected, all four assay kits could detect higher serum CORT levels in mice treated with adrenocorticotropic hormone (ACTH), compared to untreated mice. Unexpectedly though, the measured concentration of serum CORT differed significantly between assays, in both groups of mice. In faecal samples, there was no consistent positive correlation between the levels detected in the four assays and the measured concentration of FCM also differed between assays. Whereas commercially available CORT ELISAs are frequently successfully used for FCM quantification, validation of the assays is necessary as all assays do not work well under all circumstances. In this study, the ELISAs could determine relative differences in serum CORT levels and FCM levels between samples; however, the fidelity of the measurements to the true concentrations was low.