Effects of corticosterone treatment on growth, development, and the corticosterone response to handling in young Japanese quail (Coturnix coturnix japonica)

Effect of diet supplemented with functional amino acids and polyphenols on gut health in broilers subjected to a corticosterone-induced stress

To address the overuse of antimicrobials in poultry production, new functional feed ingredients, i.e. ingredients with benefits beyond meeting basic nutritional requirements, can play a crucial role thanks to their prophylactic effects. This study evaluated the effects of the supplementation of arginine, threonine and glutamine together with grape polyphenols on the gut integrity and functionality of broilers facing a stress condition. 108 straight-run newly hatched Ross PM3 chicks were kept until 35 days and were allocated to 3 treatments. Broilers in the control group were raised in standard conditions. In experimental groups, birds were administered with corticosterone in drinking water (CORT groups) to impair the global health of the animal and were fed a well-balanced diet supplemented or not with a mix of functional amino acids together with grape extracts (1 g/kg of diet-CORT + MIX group). Gut permeability was significantly increased by corticosterone in non-supplemented birds. This corticosterone-induced stress effect was alleviated in the CORT + MIX group. MIX supplementation attenuated the reduction of crypt depth induced by corticosterone. Mucin 2 and TNF-α gene expression was up-regulated in the CORT + MIX group compared to the CORT group. Caecal microbiota remained similar between the groups. These findings indicate that a balanced diet supplemented with functional AA and polyphenols can help to restore broiler intestinal barrier after a stress exposure.

Chronic Heat Stress Part 2: Increased Stress and Fear Responses in F1 Pekin Ducks Raised from Parents That Experienced Heat Stress

The effects of HS on the welfare of poultry have been reported to have a transgenerational effect on phenotype plasticity. The goal of our experiment was to determine whether parental exposure to HS would impair the performance, HPA axis response, or behavior of their offspring. We treated adult drakes and hens (n = 80 ducks/treatment) at peak lay with HS or the control temperature for 3 weeks and incubated eggs collected from the last 3 days of the experiment. We utilized 76 ducklings/parental treatment group: control (CON-F1) and HS (HS-F1). Weekly data for body weights, body condition scores (BCSs), and novel object test (NOT) were collected. At 3 weeks of age, the ducks (n = 6/treatment) were subjected to adrenocorticotropic hormone (ACTH/cosyntropin, 0.0625 mg/kg) challenge or vehicle as the control. Blood samples were collected at 0, 1, 2, 3, and 4 h relative to treatment for serum glucocorticoid and heterophil-to-lymphocyte ratio (HLR) analyses. All injected birds were euthanized with pentobarbital on the second day relative to ACTH administration, and the spleen and bursa were removed and weighed immediately. Duck level analyses were completed using one- or two-way ANOVA as appropriate. BCSs were analyzed using a chi-squared test. The HS-F1 ducks had a lower hatch weight (p < 0.05) compared with the CON-F1 ducks but no significant difference in growth rates during the 5-week period. NOT (n = 4) analyses showed that the HS-F1 ducks had a greater fear response (p < 0.001) compared with the CON-F1 ducks. Similarly, an ACTH stimulation test showed that the HS-F1 ducks had significantly (p < 0.05) heightened corticosterone and HLR responses compared with the CON-F1 ducks. The HS-F1 ducks showed altered baseline and ACTH-stimulated levels of cortisol compared with the controls. Our data suggest that parental exposure to HS impacts the HPA response and fearfulness of the F1 generation in Pekin ducks.

Effects of corticosterone administration on the body condition and blood parameters of the house sparrow, Passer domesticus

Glucocorticoids are steroid hormones produced by the adrenal glands and released into the bloodstream in response to stressful situations. In birds, corticosterone (CORT) is the main glucocorticoid released under stress. Throughout their lives, animals in nature are continually exposed to noxious stimuli known as stressful events. Any alteration of homeostatic stability is a stressful situation and this alteration triggers physiological changes to restore homeostasis. Glucocorticoids are one of the components of the complex set of physiological and behavioral responses to stress. In this work, we use CORT supplied in drinking water to evaluate its effect in blood parameters and physiology in house sparrows (Passer domesticus). To accomplish this, P. domesticus were administered three different doses of CORT in drinking water for 72 h. Body mass, organ mass, pectoral muscle mass, leg muscle mass, and blood parameters (CORT, triglycerides, glucose and uric acid, heterophils/lymphocytes ratio, hematocrit, and serum protein profile) were determined before and after CORT treatment. A 15% decrease in body mass with a significant decrease in pectoral mass were observed after the higher CORT treatment, as well as a decrease in the plasma concentration of uric acid. Lastly, we found a reversal of the heterophils/lymphocytes ratio and a decrease in hematocrit. It was possible to establish first data for baseline and CORT-alteration values in serum protein profile for P. domesticus. Baseline and altered values of blood parameters and serum protein profile could be an important tool in field ecology because they provide important data to assess the physiological condition in wild birds.

Prenatal yolk corticosterone exposure promotes skeletal growth and induces oxidative imbalance in yellow-legged gull embryos

Maternally derived hormones induce variation in offspring phenotype, with consequences that can carry over into post-natal life and even into adulthood. In birds, maternal egg corticosterone (CORT) is known to exert contrasting effects on offspring morphology, physiology and behaviour after hatching. However, information on the effects of CORT exposure on pre-hatching embryonic development is limited. We experimentally increased yolk CORT levels in yellow-legged gull (Larus michahellis) eggs, and assessed the effects on embryo pre-hatching development and oxidative status of brain and liver. CORT-supplemented embryos reached a larger skeletal size and liver mass compared with controls. Embryos from CORT-injected last-laid eggs showed decreased activity of the hepatic antioxidant enzymes superoxide dismutase and catalase, while intermediate-laid eggs showed increased levels of lipid peroxidation. However, elevated yolk CORT did not affect oxidative stress endpoints in the brain. Our results indicate that elevated yolk CORT levels affect prenatal embryo development by promoting skeletal growth, and induce laying sequence- and organ-specific oxidative imbalance, with potential adverse consequences during postnatal life, especially for late-hatched offspring.

Stress and steroid interaction modulates expression of estrogen receptor alpha in the brain, pituitary, and testes of immature Gallus gallus domesticus

In nature, food availability stimulates hypothalamo-pituitary-gonadal (HPG) axis while its scarcity induces stress, which further stimulates hypothalamo-pituitary-adrenal (HPA) axis producing a detrimental effect on the avian reproductive physiology. The present experiment was designed to examine the interaction of stress like food restriction and estradiol on male reproductive physiology with special emphasis on estrogen receptor alpha (ERα) as these play crucial role in reproduction. To achieve this, 60 day old White Leghorn immature cockrels were taken and divided into four groups (n  =  8 per group). One group was provided with food and water ad libitum. Second group was food restricted (FR) for 9 h/day after 5 days, third and fourth were administered with estradiol benzoate (EB 0.5 mg/100g/day) for 12 days. Fourth group was FR for 9 h/day after 5 days of EB treatment till last day of experiment (EB + FR). Immunofluorescent localization of ERα was principally in the pre-optic area and paraventricular nuclei of hypothalamus and in anterior pituitary gland. ERα expression was highly reduced (from 40 AU to 20 AU) after FR in testis but it increased (50 AU) after EB administration, EB + FR reflects a diminishing pattern in the increment after EB. FR decreased plasma estradiol while EB increased it. Increased plasma corticosterone, hydrogen peroxide, malondialdehyde, and decreased anti-oxidant enzymes in brain and testis of all groups indicate oxidative stress in the HPG axis. The increased ERα after EB and a decrease with FR and EB + FR support their reproductive function. Estrogen and its receptor alpha are responsible for maintaining epithelial morphology but FR along with EB administration modulates the testicular development by significantly decreasing its size (p<.0001) and seminiferous tubules (p<.0001) and no sperm formation via highly reduced expression of ir-ERα in HPG axis. Our findings led us to conclude that stress like FR and estradiol induces testicular regression immature male chickens by modulating ir-ERα expression in the HPG axis thereby resulting in reduction in reproductive physiology.

Effect of short-term fasting on the expression of ACTH (cMC2) receptor in the adrenal glands of chicken (Gallus domesticus)

<b>Domestic hen is a full model in terms of stress and adrenal function. The main hormone produced by the hens’ adrenals is corticosterone, synthesized and secreted by stimulating the HPA axis during stress. Direct activation of adrenal activity is conditioned by ACTH, which binds to the melanocortin receptor cMC2 in adrenals. It stimulates the synthesis and release of corticosterone. One of the factors that stimulate the HPA axis activity is the starvation, to which the hen is very sensitive. The purpose of this study was to determine the ACTH receptor cMC2 expression in the hens’ adrenals during the short-term fasting and after restoring the proper level of nutrition (refeeding). The results of the experiment show that 24-hour of food deprivation is stressful for the hen, as indicated by increased concentrations of corticosterone in the adrenals and in blood plasma. Changes in cMC2R expression and level of corticosterone in the adrenals during fasting and refeeding indicate a rapid increase of HPA axis activity in response to differentiated levels of nutrition. The results of this experiment confirm the direct effect of ACTH on the avian adrenals in corticosterone release.

Correlations between Per- and Polyfluoroalkyl Substances and Body Morphometrics in Fledgling Shearwaters Impacted by Plastic Consumption from a Remote Pacific Island

We investigated the concentrations of 45 per- and polyfluoroalkyl substances (PFASs) in fledgling flesh-footed shearwater (Ardenna carneipes; n = 33) and wedge-tailed shearwater (A. pacifica; n = 9) livers via liquid chromatography-tandem mass spectrometry and their relationship to body morphometrics and ingested plastic mass recorded in 2019 on Lord Howe Island (NSW, Australia). Sixteen PFASs were detected, of which perfluorooctanesulfonate (PFOS) was the dominant compound, detected in 100% of birds (1.34-13.4 ng/g wet wt). Long-chain perfluorocarboxylic acids, including perfluorodecanoic acid (PFDA; <0.04-0.79 ng/g wet wt) and perfluorotridecanoic acid (PFTrDA; <0.05-1.6 ng/g wet wt) were detected in >50% of birds. There was a positive correlation between PFDA and PFTrDA concentrations and wing chord length (R_s  = 0.36, p = 0.0204; R_s  = 0.44, p = 0.0037, respectively), and between PFDA concentrations and total body mass (R_s  = 0.33, p = 0.032), suggesting that these compounds may impact shearwater fledgling morphometrics. Plastic was present in the intestinal tract of 79% of individuals (<7.6 g), although there was no correlation between PFAS concentrations and plastic mass, indicating that ingested plastic is not the likely primary exposure source. The widespread occurrence of PFASs in fledgling marine birds from a relatively pristine location in the Southern Hemisphere suggests that further studies in adult shearwaters and other marine birds are warranted to investigate whether there are any long-term physiological effects on bird species. Environ Toxicol Chem 2021;40:799-810. © 2020 SETAC.

Omega-3 fatty acids reduce the negative effects of dexamethasone-induced physiological stress in laying hens by acting through the nutrient digestibility and gut morphometry

In this study, the effects of omega-3 fatty acids on egg production, nutrients digestibility, eggs yolk lipid peroxidation, and intestinal morphology in laying hens under physiological stress were investigated. Ninety-six 35-wk-old Lohmann LSL-Lite laying hens were used in 2 × 3 factorial arrangement with 2 levels of dexamethasone (DEX) (0 and 1.5 mg/kg of the diet) and 3 levels of omega-3 fatty acids (0, 0.24, or 0.48% of the diet) in a completely randomized design. At 41 wk of age, the stress groups were continuously fed with a DEX 1.5 mg/kg diet for 1 wk. Egg production, egg mass, feed intake, egg weight, and feed conversion ratio were recorded. In addition, the AME, digestibility of CP, crude fat (CF), and organic matter were measured during the stress induction period. At the end of 41 wk of age, malondialdehyde and cholesterol concentrations in the egg yolk and intestinal morphology were investigated. The results showed that egg production, egg mass (P < 0.0001), egg weight (P = 0.043), and BW (P = 0.0005) were lower in DEX layers. Feed intake was reduced by the interaction between DEX and omega-3 fatty acid (P = 0.042). Malondialdehyde value (P = 0.002) and cholesterol concentration (P = 0.001) in egg yolk increased by DEX administration. The combination of DEX administration and omega-3 fatty acids supplementation was found in the indices of intestinal morphology such as villus height and width and crypt depth (P < 0.05). Administration of DEX decreased the CP digestibility (P < 0.0001) and AME (P = 0.006). Digestibility of CF and AME in the group of 0.48% omega-3 fatty acids were higher (P < 0.05) than those of 0 and 0.24%. In conclusion, we found that dietary omega-3 fatty acids had beneficial effects on gut morphology and nutrient digestibility in laying hens under physiological stress. However, they could not alleviate the negative effects of physiological stress on performance.

Photoperiod dependent expression of estrogen receptor alpha in testes of Japanese quail: Involvement of Withania somnifera in apoptosis amelioration

Light plays important function in the regulation of reproduction in vertebrates including birds. The prolonged long day length exposure causes reproductively inactive state or photorefractoriness in many avian species including Japanese quail. Withania somnifera (WS) is a medicinal plant known to have beneficial effects on stress and infertility. The study investigates the physiological effect of WS on the light-induced stress in quail mediated by estrogen receptor alpha. Quails were exposed to long day length for three months and then transferred into intermediate day length to make them photorefractory (PR) while controls under natural day length. Administration of Withania somnifera root extract (WSRE) in PR quail induces estrogen and decreases corticosterone in male Japanese quail. Immunoreactivity of ERα decreased in testis of PR quail and increased after oral administration of WSRE compared to control. Expression of ir-Caspase-3 and ir-p53 in the testis increased in PR while decreased in PR + WS. Histologically, seminiferous tubules size decreased in PR whereas increased in PR + WS quails. Scanning electron microscopic study reveals sperms in clusters with proper head and tail in control. In PR quails sperms were few and distorted while WSRE improved the sperm morphology. From the study, it is concluded that during photorefractoriness gonadal regression occurs due to testicular apoptosis which causes stress. WSRE helps to overcome stress and improve reproductive performance via increase in expression of ir-ERα during PR condition. Further, the stress ameliorating effect of WSRE in reducing apoptosis mediated by ir-Caspase-3 and ir-p53 in the testes is clearly evident in Japanese quail.

Water and Food restriction decreases immunoreactivity of oestrogen receptor alpha and antioxidant activity in testes of sexually mature Coturnix coturnix japonica

Food and water are closely associated with reproductive willingness in vertebrates. These are important for animals and their non-availability act as stressors which decrease sex steroid secretion suppressing reproductive behaviour. Oestrogen plays a crucial role in reproduction via its receptors alpha (ERα) and beta (ERβ). This study tested the hypothesis that ERα in testes of male Japanese quail is regulated during water and food deprivations. The present study reveals that both water and food deprivations cause oxidative stress and subsequently decrease catalase and superoxide dismutase activity, while these increase malondialdehyde and hydrogen peroxide. Both deprivations reduce plasma oestradiol whereas elevate corticosterone level. The immunofluorescent localization of ERα in the testes occurs predominantly in the seminiferous tubules of control while reduces after both food and water deprivations. All types of spermatogenic cells were seen in control testis, while after water and food deprivations size of seminiferous tubules and spermatogenic cells population decreased. Scanning electron microscopic study exhibited fully mature sperms in clusters with head and elongated flagellum, whereas after water deprivation maximum sperms were distorted, scattered with highly reduced head. On food deprivation, only few sperms were seen with head and tail. Thus, taking into account the localization of ERα in testis, it is obvious that oestrogens produced locally are involved in regulation of spermatogenesis and spermiogenesis during stress.

Post-natal corticosterone exposure affects ornaments in adult male house sparrows (Passer domesticus)

In vertebrates, the ontogeny of several crucial organismal systems is known to occur early in life. Developmental conditions can ultimately have important consequences on adult fitness by affecting individual phenotype. These developmental effects are thought to be primarily mediated by endocrine systems, and especially by glucocorticoids. In this study, we tested how post-natal exposure to corticosterone (the primary avian glucocorticoid) may subsequently affect the expression of ornaments in adult male house sparrows (Passer domesticus). Specifically, we investigated the long-term consequences of this manipulation on the size and color of several visual signals: badge, wing bar, tarsus and beak. Post-natal corticosterone exposure had a strong negative impact on the size, but not the color, of some male ornaments (badge and wing bar surface area). Because wing bar and badge surface area are used as sexual and/or hierarchical signals in house sparrow, we showed that early life stress can affect some aspect of attractiveness and social status in this species with potentially important fitness consequences (e.g. sexual selection and reproductive performance). Future studies need now to explore the costs and benefits of this developmental plasticity for individuals (i.e. fitness).

Influence of persistent organic pollutants on the endocrine stress response in free-living and captive red kites (Milvus milvus)

Persistent organic pollutants (POPs) have the potential to impair the endocrine regulation of organisms and alter their ability to respond to environmental changes. We studied whether polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) affected the endocrine regulation of free-living and captive red kites (Milvus milvus) through studying the dynamics of corticosterone (CORT) and dehydroepiandrosterone (DHEA). We sampled migratory free-living kites coming from northern Europe and captive kites born in a rehabilitation center in Spain. We used body feathers from the interscapular region as a minimally-invasive and integrative matrix. The most abundant compound detected in free-living kites was 4,4'-dichlorodiphenyldichloroethylene (4,4'-DDE; 6.10 ± 1.56 ng g^-1 dw feather) followed by CB-153 (3.10 ± 0.63 ng g^-1 dw feather) and CB-180 (2.43 ± 1.08 ng g^-1 dw feather). In captive kites, the most abundant compounds were 4,4'-dichlorodyphenyltrichloroethane (4,4'-DDT; 2.38 ± 1.30 ng g^-1 dw feather), CB-153 (2.15 ± 0.47 ng g^-1 dw feather) and hexachlorobenzene (HCB; 2.03 ± 0.45 ng g^-1 dw feather) at similar concentrations. Free-living kites showed higher levels of 4,4'-DDE and CB-180 in comparison to captive kites. Age influenced HCB and CB-101 levels, whereas body mass was inversely related to CB-180 and 4,4'-DDT. Interestingly, captive kites showed a ratio DDT/DDE higher than 1 suggesting a relatively recent exposure of DDT, in contrast to free-living kites. Regarding hormonal levels, free-living kites showed higher levels of CORT (3.30 ± 0.22 pg mm^-1 feather) than captive (2.40 ± 0.16 pg mm^-1 feather), reflecting higher allostatic load. In addition, a positive association between PCBs and DDTs and adrenal hormones was found in free-living kites, suggesting an increase of CORT as a response of the endocrine system to cope with stressors and a subsequent elevation of DHEA to ameliorate the potential negative effects that high CORT levels could cause to the organism.

Effect of Chromium Nanoparticles on Physiological Stress Induced by Exogenous Dexamethasone in Japanese Quails

Chromium (Cr), as an essential trace element, plays a critical role in carbohydrate, protein, and lipid metabolism in animals. It has been suggested that the beneficial effects of Cr increase by environmental stresses, which lead to greater Cr effects on stressed animals. The objective of the present study was to evaluate the response of physiologically stressed Japanese quails (Coturnix japonica) to dietary chromium nanoparticle (Nano-Cr) supplementation. The stress was induced by adding dexamethasone (0.6 mg/kg BW) to Japanese quails' diet from 17 to 22 days of age. A total of 360 birds were randomly allocated to six dietary treatments with four replicates each having 15 birds: negative control diet (no-stress, no-additive; NC), positive control diet (stress, no-additive; PC), and stress additive diets including four diets containing 200, 400, 800, and 1200 μg/kg of Nano-Cr. Performance and haematological parameters were affected (P < 0.05) by physiological stress though they were not affected by adding Nano-Cr. Comparison of diets containing Nano-Cr levels and stress no-additive diets, at 23 days of age, was indicative of a positive linear relationship (P < 0.05) between dietary Nano-Cr levels and feed intake and average daily gain. Furthermore, white blood cell (WBC) count as well as haematocrit level increased (P < 0.05) as the level of supplied Nano-Cr increased. A negative relationship (P < 0.05) was observed between Nano-Cr levels and heterophil percentage and heterophil/lymphocyte ratio. On day 35, increased dietary Nano-Cr improved (P < 0.05) weight gain, live body weight, energy/protein utilization efficiency, and WBC count. In conclusion, supplementation of diet with optimum concentration of Nano-Cr revealed alleviation of negative effects of physiological stress in quails.

No evidence for sex-specific effects of the maternal social environment on offspring development in Japanese quail (Coturnix japonica)

The social environment of reproducing females can cause physiological changes, with consequences for reproductive investment and offspring development. These prenatal maternal effects are often found to be sex-specific and may have evolved as adaptations, maximizing fitness of male and female offspring for their future environment. Female hormone levels during reproduction are considered a potential mechanism regulating sex allocation in vertebrates: high maternal androgens have repeatedly been linked to increased investment in sons, whereas high glucocorticoid levels are usually related to increased investment in daughters. However, results are not consistent across studies and therefore still inconclusive. In Japanese quail (Coturnix japonica), we previously found that pair-housed females had higher plasma androgen levels and tended to have higher plasma corticosterone levels than group-housed females. In the current study we investigate whether these differences in maternal social environment and physiology affect offspring sex allocation and physiology. Counter to our expectations, we find no effects of the maternal social environment on offspring sex ratio, sex-specific mortality, growth, circulating androgen or corticosterone levels. Also, maternal corticosterone or androgen levels do not correlate with offspring sex ratio or mortality. The social environment during reproduction therefore does not necessarily modify sex allocation and offspring physiology, even if it causes differences in maternal physiology. We propose that maternal effects of the social environment strongly depend upon the type of social stimuli and the timing of changes in the social environment and hormones with respect to the reproductive cycle and meiosis.

House sparrows mitigate growth effects of post-natal glucocorticoid exposure at the expense of longevity

Acute, short-term effects of early-life stress and associated glucocorticoid upregulation on physiology and survival are widely documented across vertebrates. However, the persistence and severity of these effects are largely unknown, especially through the adult stage and for natural systems. Here, we investigate physiological, morphological, and survival effects of post-natal glucocorticoid upregulation across the nestling, juvenile, and adult life stages in house sparrows (Passer domesticus). We manipulate circulating corticosterone concentration in wild, free-living house sparrow nestlings and monitor body size, size-corrected mass, two measures of health (hematocrit and phytohemagglutinin-induced skin swelling), and survival in a captive environment until adulthood. We find that early-life corticosterone exposure depresses nestling size-corrected mass in both sexes, with no strong effect of the treatment on body size or our two measures of health. Birds are able to compensate for negative effects of high early-life corticosterone exposure in the long-term and this effect largely disappears by the juvenile and adult stages. However, treatment has a negative effect on survival through one year of age, suggesting that long-term compensation comes at a price.

Noradrenergic modulation of gonadotrophin-inhibitory hormone gene expression in the brain of Japanese quail

Gonadotrophin-inhibitory hormone (GnIH) is a hypothalamic neuropeptide that inhibits gonadotrophin synthesis and release in birds and mammals. In Japanese quail, GnIH neurones express the noradrenergic receptor and receive noradrenergic innervation. Treatment with noradrenaline (NA) stimulates GnIH release from diencephalic tissue blocks in vitro. However, the effects of NA on hypothalamic GnIH gene expression have not been determined. We investigated noradrenergic regulation of GnIH gene expression in the brain of male quail using the selective noradrenergic neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine hydrochloride (DSP-4). We first showed that DSP-4 reduced the number of noradrenergic (dopamine-β-hydroxylase immunoreactive) cells in the locus coeruleus (LoC) and specifically lowered the NA concentration in the hypothalamus of male quail. Other monoamines, such as dopamine and serotonin, were not affected by drug treatment. DSP-4 did not decrease the numbers of noradrenergic cells of the lateral tegmental cell group, nor the plasma NA concentration. Decreased hypothalamic NA levels after DSP-4 treatment did not change GnIH gene expression in the brains of quail during their interaction with conspecifics. On the other hand, GnIH gene expression increased in the brains of quail socially isolated for 1 hour after DSP-4 treatment. These results suggest that some noradrenergic neurones have inhibitory effects on GnIH gene expression of the hypothalamus in solitary quail.

Experimentally reducing corticosterone mitigates rapid captivity effects on behavior, but not body composition, in a wild bird

Wild animals and captives display physiological and behavioral differences, and it has been hypothesized, but rarely tested, that these differences are caused by sustained elevation of the hormone corticosterone. We used repeated computed tomography (CT) imaging to examine body composition changes in breeding male and female wild house sparrows (Passer domesticus; n=20) in response to two weeks of captivity, and assessed behavioral changes using video recordings. Half of the birds received the drug mitotane, which significantly decreased stress-induced corticosterone titers compared to controls. Based on the CT images, fat volumes increased, and pectoralis muscle density and heart and testes volumes decreased, over the two weeks of captivity in both groups of birds. However, beak-wiping, a behavior that can indicate anxiety and aggression, showed increased occurrence in controls compared to mitotane-treated birds. While our results do not support the hypothesis that these body composition changes were primarily driven by stress-induced corticosterone, our data suggest that experimentally reducing stress-induced corticosterone may mitigate some captivity-induced behavioral changes. Broadly, our results emphasize that researchers should take behavioral and physiological differences between free-living animals and captives into consideration when designing studies and interpreting results. Further, time in captivity should be minimized when birds will be reintroduced back to the wild.

Acute heat stress up-regulates neuropeptide Y precursor mRNA expression and alters brain and plasma concentrations of free amino acids in chicks

Heat stress causes an increase in body temperature and reduced food intake in chickens. Several neuropeptides and amino acids play a vital role in the regulation of food intake. However, the responses of neuropeptides and amino acids to heat-stress-induced food-intake regulation are poorly understood. In the current study, the hypothalamic mRNA expression of some neuropeptides related to food intake and the content of free amino acids in the brain and plasma was examined in 14-day-old chicks exposed to a high ambient temperature (HT; 40±1 °C for 2 or 5 h) or to a control thermoneutral temperature (CT; 30±1 °C). HT significantly increased rectal temperature and plasma corticosterone level and suppressed food intake. HT also increased the expression of neuropeptide Y (NPY) and agouti-signaling protein (ASIP) precursor mRNA, while no change was observed in pro-opiomelanocortin, cholecystokinin, ghrelin, or corticotropin-releasing hormone precursor mRNA. It was further found that the diencephalic content of free amino acids - namely, tryptophan, leucine, isoleucine, valine and serine - was significantly higher in HT chicks with some alterations in their plasma amino acids in comparison with CT chicks. The induction of NPY and ASIP expression and the alteration of some free amino acids during HT suggest that these changes can be the results or causes the suppression of food intake.

The antinociceptive effects of tualang honey in male sprague-dawley rats: a preliminary study

Tualang honey (蜂蜜 Fēng Mì) is known to have anti-inflammatory property, but its antinociceptive property has not been extensively investigated. In this study, we examined the preemptive effects on administering different doses of Tualang honey and prednisolone on the nociceptive response in male Sprague-Dawley rats. Thirty-five male Sprague-Dawley rats were randomized into five groups (n = 7) and each group received either distilled water, Tualang honey (0.2, 1.2 or 2.4 g/kg) or prednisolone (10 mg/kg) for 10 days. The response to noxious thermal stimulus was assessed using tail flick test on Day 10. The well-being of the rats was also assessed by monitoring their food intake and body weight. Data were analyzed using one-way Analysis of Variance (ANOVA) with post-hoc Scheffe's test and P value less than 0.05 was considered significant. In tail flick test, the tail flick latency time was significantly higher in the groups that received 1.2 g/kg and 2.4 g/kg of Tualang honey and 10 mg/kg of prednisolone, compared to the control group (P < 0.05). There was significant reduction in the total food pellet intake in the groups receiving prednisolone and Tualang honey (1.2 g/kg and 2.4 g/kg) compared to controls; however, the body weight gain was only significantly reduced in the prednisolone group. All the parameters were not significantly affected in the group receiving 0.2 g/kg of Tualang honey. In conclusion, preemptive administration of Tualang honey (1.2 g/kg and 2.4 g/kg) and prednisolone (10 mg/kg) had reduced the pain responses. The reduced weight gain in the prednisolone group is an unwanted effect due to its metabolic and central actions. Further studies are required to confirm the antinociceptive effects and elucidate the mechanism of antinociceptive action of Tualang honey in the rats.

Response of testosterone and corticosterone plasma levels to the challenge of sibling competition: a study in common terns

The hormonal response to social challenges has been widely studied, however, most work focused on adult behavior in a reproductive context although developing animals also encounter important social challenges early in life. We studied the relationship between acute sibling competition and plasma corticosterone (CORT) and testosterone (T) in common tern (Sterna hirundo) chicks, a species whose young compete for access to food by scramble interactions. Blood samples were taken in nests with two and only one single chick both immediately after a feeding bout and in non-challenged controls. We found that T levels were lower in siblings challenged by a feeding bout as compared to controls, which may be explained by the fact that T suppresses begging behavior and is only elevated in response to territorial intrusion but not sibling competition in a related species. Singletons had, corrected for body condition, generally lower CORT levels than siblings suggesting that growing up with siblings creates a competitive environment in which high CORT levels are sustained irrespective of a social challenge. CORT levels were also negatively correlated with body condition and were higher in males than in females. The latter may be related to sex-specific food requirements and susceptibility to stress. Our results suggest a possible suppressive effect of acute sibling competition on T secretion, and a positive effect on CORT levels by longer term sibling competition. The degree to which these dynamics are related to begging or aggression, or both, needs further experimental work.

Chronic stress alters concentrations of corticosterone receptors in a tissue-specific manner in wild house sparrows (Passer domesticus)

The physiological stress response results in release of glucocorticoid hormones such as corticosterone (CORT). Whereas short-term activation of this response helps animals cope with environmental stressors, chronic activation can result in negative effects including metabolic dysregulation and reproductive failure. However, there is no consensus hormonal profile of a chronically-stressed animal, suggesting researchers may need to look beyond hormone titers to interpret the impacts of chronic stress. In this study, we brought wild house sparrows (Passer domesticus) into captivity. We then compared glucocorticoid and mineralocorticoid receptor concentrations in sparrows exposed either to a standardized chronic stress protocol (n=26) or to standard husbandry conditions (controls; n=20). We used radioligand binding assays to quantify receptors in whole brain, liver, kidneys, spleen, gonads, gastrocnemius and pectoralis muscle, omental and subcutaneous fat, and bib and back skin. In most tissues, CORT receptors did not differ between controls and stressed animals, although we found marginal increases in receptor density in kidney and testis in stressed birds at some time points. Only in pectoralis muscle was there a robust effect of chronic stress, with both receptor types higher in stressed animals. Increased pectoralis sensitivity to CORT with chronic stress may be part of the underlying mechanism for muscle wasting in animals administered exogenous CORT. Furthermore, the change in pectoralis was not paralleled by gastrocnemius receptors. This difference may help explain previous reports of a greater effect of CORT on pectoralis than on other muscle types, and indicate that birds use this muscle as a protein reserve.

Individual variation in glucocorticoid stress responses in animals

When stimuli from the environment are perceived to be a threat or potential threat then animals initiate stress responses, with activation of the hypothalamo-pituitary-adrenal axis and secretion of glucocorticoid hormones (cortisol and corticosterone). Whilst standard deviation or standard error values are always reported, it is only when graphs of individual responses are shown that the extensive variation between animals is apparent. Some animals have little or no response to a stressor that evokes a relatively large response in others. Glucocorticoid responses of fish, amphibian, reptiles, birds, and mammals are considered in this review. Comparisons of responses between animals and groups of animals focused on responses to restraint or confinement as relatively standard stressors. Individual graphs could not be found in the literature for glucocorticoid responses to capture or restraint in fish or reptiles, with just one graph in mammals with the first sample was collected when animals were initially restrained. Coefficients of variation (CVs) calculated for parameters of glucocorticoid stress responses showed that the relative magnitudes of variation were similar in different vertebrate groups. The overall mean CV for glucocorticoid concentrations in initial (0 min) samples was 74.5%, and CVs for samples collected over various times up to 4 h were consistently between 50% and 60%. The factors that lead to the observed individual variation and the extent to which this variation is adaptive or non-adaptive are little known in most animals, and future studies of glucocorticoid responses in animals can focus on individual responses and their origins and significance.

Are baseline and short-term corticosterone stress responses in free-living amphibians repeatable?

Amphibians respond to environmental stressors by secreting corticosterone, a stress hormone which promotes physiological and behavioral responses. Capture handling can be used to stimulate physiological stress response in amphibians. The use of single blood sampling and presentation of mean data often limits the quantification of within and between individual variation in baseline and short-term corticosterone stress responses in amphibians. It is important for studies of amphibian physiological ecology to determine whether baseline and short-term corticosterone stress responses are consistent or not. We quantified repeatability (r), a statistical measure of consistency, in baseline and short-term corticosterone stress responses to a standard capture and handling stress protocol in free-living adult male cane toads (Rhinella marina). Corticosterone metabolite concentrations were measured entirely non-invasively in male toad urine samples via an enzyme-immunoassay. During the first sampling occasion, urine samples were collected manually from individual male toads (n=20) immediately upon field capture. Toads were handled for 5min then transferred to plastic bags (constituting a mild stressor), and urine samples were collected hourly over 8h in the field. The toads were resampled for baseline (0h) urine corticosterone with hourly urine sampling over 8h (for quantification of the stress induced corticosterone) at 14 day intervals on three consecutive occasions. Within and between sample variations in urinary corticosterone metabolite concentrations were also quantified. All toads expressed a corticosterone stress response over 8h to our standard capture and handling stress protocol. Variations both within and between toads was higher for corrected integrated corticosterone concentrations than corticosterone concentrations at baseline, 3 or 6h. Baseline urinary corticosterone metabolite concentration of the male toads was highly repeatable (r=0.877) together with high statistical repeatabilities for 3h (r=0.695), 6h (r=0.428) and 8h (r=0.775) corticosterone metabolite concentrations, and for the total and corrected integrated corticosterone responses (r=0.807; r=0.743 respectively). This study highlights that baseline and short-term corticosterone stress responses are repeatable in free-living amphibians. Future studies should utilize this non-invasive tool to explore repeatability among seasons and across years, and determine its functional significance in relation to behavioral ecology and reproduction in amphibians generally.

Fecal corticosterone metabolites and plasma corticosterone in Japanese quail selected for low or high plasma corticosterone responses to brief restraint

Fecal corticosterone metabolites and plasma corticosterone in Japanese quail selected for low- or high-plasma corticosterone responses to brief mechanical restraint (low- and high-stress lines), and in a line of unselected quail, were measured in this study. No line differences were observed in baseline plasma corticosterone concentrations, but fecal corticosterone metabolite concentrations and daily fecal corticosterone metabolite production were 20% higher in quail of the high-stress line than in unselected or low-stress quail for males and females living together in group cages (P < 0.05). No differences were observed between lines in corticosterone metabolite concentrations and production for male birds in individual cages. Baseline plasma corticosterone concentrations, fecal corticosterone metabolite concentrations, and production appeared to be higher for males and females in group cages compared with males in individual cages. This difference might have been because of greater corticosterone secretion by male quail living in mixed sex groups than living individually. Correlations between baseline plasma corticosterone concentrations and fecal corticosterone metabolite concentrations in low-stress and high-stress quail, and for all birds combined, were r = 0.521 (P = 0.038), r = 0.604 (P = 0.013), and r = 0.431 (P = 0.002), respectively. The low- and high-stress lines that have been selected for low- and high-corticosterone responses differ in other characteristics, including growth and reproductive performance, and the current results are consistent with the assumption that these other differences are a consequence of greater daily corticosterone secretion in quail of the high-stress line.

Phytosterol additive boosts adrenal response to ACTH in male Japanese quail (Coturnix coturnix japonica)

To investigate the adrenal effect of a phytosterol (PS) additive, 80 male Japanese quail were divided into four sub-groups and fed 0, 40, 400, and 4,000 ppm of PS, respectively, for 21 days. Subsequently, 50% of the birds from each dosage group were subjected to a 6-day adrenal function test, whereby they were injected with long-lasting adrenocorticotropin (ACTH). The remaining quail in each PS dosage group were raised under normal conditions. The groups receiving 400 and 4000 ppm PS exhibited decreased serum levels of LDL-cholesterol with and without ACTH stimulation (P < 0.01). No amount of dose of PS changed serum corticosterone (CORT) under normal conditions (P > 0.05). Enhancement of CORT was observed on the 2nd and the 6th days of the ACTH challenge in birds receiving 400 ppm (P < 0.05). Average ACTH-induced CORT levels in the 400 ppm group were higher than in the 0 ppm group (P < 0.01). Our results demonstrated that PS can boost ACTH-induced CORT levels in male Japanese quail.

Does immune suppression during stress occur to promote physical performance?

Two adaptationist hypotheses have been proposed to explain why stress, particularly elevation of stress hormones (i.e., glucocorticoids), tends to suppress immune functions. One is that immune suppression represents efforts to minimize autoimmune responses to self-antigens released as organisms cope with stressors (i.e., the autoimmune-avoidance hypothesis). The other is that immune suppression occurs to promote a shunting of resources to life processes more conducive to survival of the stressor (i.e., the re-allocation hypothesis). Here in wild-caught house sparrows (Passer domesticus), we tested the second hypothesis, asking whether sustained elevation of baseline glucocorticoids, due to captivity, caused a greater rate of decline in immune functions than flight performance. A greater decline in immune functions than flight performance would support the re-allocation hypothesis. As in previous studies, we found that captivity tended to alter baseline corticosterone, suggesting that house sparrows experience captivity as a stressor. Captivity also affected several constitutive and induced innate immune metrics: bacterial (Escherichia coli) killing activity (BKA) of blood and oxidative burst of leukocytes both changed in a manner consistent with immune disregulation. In contrast, breast muscle size and vertical flight (hovering) duration improved over captivity. Collectively, these changes provide indirect support for the re-allocation hypothesis, although within individuals, changes in immune and physical performance were unrelated.

Pre- and post-natal stress in context: effects on the stress physiology in a precocial bird

Developmental stress can significantly influence physiology and survival in many species. Mammalian studies suggest that pre- and post-natal stress can cause different effects (i.e. hyper- or hypo-responsiveness) on the Hypothalamic-Pituitary-Adrenal axis (HPA axis), the main mediator of the stress response. In mammals, the physiological intimacy between mother and offspring constrains the possibility to control, and therefore to manipulate, maternal pre- and post-natal influences. Here, by using the Japanese quail (Coturnix c. japonica) as our model, we elevated the glucocorticoid stress hormone corticosterone in ovo and/or in the endogenous circulation of hatchlings. We examined the effects of treatments on corticosterone and glucose stress responses at two different ages, in juvenile and adult quail. In juveniles, corticosterone data revealed a sex-specific effect of post-natal treatment regardless of the previous pre-natal protocol, with post-natally treated females showing shorter stress responses in comparison with the other groups, while no differences were observed among males. In adulthood, birds previously stressed as embryos showed higher corticosterone concentrations over the stress response compared with controls. This effect was not evident in birds subjected to either post- or the combined treatments. There were no effects on glucose in the juveniles. However, adult birds previously stressed in ovo showed opposite sex-specific basal glucose patterns compared with the other groups. Our results demonstrate that (1) early glucocorticoid exposure can have both transient and long-term effects on the HPA axis, depending upon the developmental stage and sex and (2) post-natal stress can modulate the effects of pre-natal stress on HPA activity.

Urinary corticosterone responses to capture and toe-clipping in the cane toad (Rhinella marina) indicate that toe-clipping is a stressor for amphibians

Toe-clipping, the removal of one or more toes, is a common method used to individually mark free-living animals. Whilst this method is widely used in studies of amphibians, the appropriateness of the method, and its potential detrimental effects have been the subject of debate. Here, we provide for the first time, evidence that toe-clipping is a stressor in a wild amphibian. We measured urinary corticosterone responses of male cane toads (Rhinella marina) to capture and handling only, and to toe-clipping under field conditions. Urinary testosterone concentrations and white blood cell proportions were also measured. Urinary corticosterone metabolite concentrations increased 6h after capture and handling only and remained high for 24h; corticosterone returned to baseline levels after 48 h and remained low at 72 h post capture and handling. Corticosterone concentrations in toads subjected to toe-clipping increased at 6h to significantly higher concentrations than after capture and handling only, then decreased more slowly than after capture and handling, and were still elevated (approximately double basal level) 72 h after toe-clipping. Testosterone did not change significantly after capture and handling only, whereas after toe-clipping testosterone decreased at 6h and remained low at 72 h. There were weak short-term effects of toe-clipping compared with capture and handling only on white blood cell proportions. We have clearly shown that toe-clipping is a distinctly stronger stressor than capture and handling alone. This indicates that there is an ethical cost of toe-clipping, and this should be considered when planning studies of amphibians.

The relationship between adrenocortical function and Hsp70 expression in socially isolated Japanese quail

Physiological responses to social isolation stress were compared in 56-day-old male Japanese quail. Birds were fed pretreated diets for 3 days as follows: (i) Basal diet (control); (ii) Basal diet+1500 mg/kg metyrapone (BM); (iii) Basal diet+30 mg/kg corticosterone (BCO); (iv) Basal diet+250 mg/kg ascorbic acid (BC); (v) Basal diet+250 mg/kg α-tocopherol (BE); (vi) Basal diet+250 mg/kg ascorbic acid and 250 mg/kg α-tocopherol (BCE). The birds were subsequently socially isolated in individual opaque brown paper box for 2 hours. Plasma corticosterone (CORT) concentration and heart and brain heat shock protein 70 (Hsp 70) expressions were determined before stress and immediately after stress. Two hours of isolation stress elevated CORT concentration significantly in the control and BE birds but not in the BC, BCE and BM birds. There was a significant reduction in CORT concentration after isolation stress in the BCO group. Isolation stress increased Hsp 70 expression in the brain and heart of control and BM birds. However, brain and heart Hsp 70 expressions were not significantly altered in the isolated BC, BCE and BE birds. Although, the CORT concentration of BM birds was not affected by isolation stress, Hsp70 expression in both brain and heart were significantly increased. Moreover, exogenous corticosterone supplementation did not result in elevation of Hsp 70 expression. It can be concluded that, although Hsp 70 induction had not been directly affected by CORT concentration, it may be modulated by the HPA axis function via activation of ACTH.

Past or present? Relative contributions of developmental and adult conditions to adult immune function and coloration in mallard ducks (Anas platyrhynchos)

Developmental conditions affect adult physiological processes and phenotypic traits, including those associated with both survival and reproduction. Carotenoids are molecules that generate sexually attractive coloration, and these pigments are acquired throughout life and can affect antioxidant capacity and immunocompetence of young and old animals. However, few studies have tracked carotenoid status and condition during development and into adulthood to understand how ontogeny affects later-life health and coloration of both males and females. We reared male and female mallard ducks (Anas platyrhynchos) from hatch to adulthood, measured circulating carotenoid titers and body condition (i.e., size-adjusted body mass) throughout development, and assessed adult immune function and integumentary carotenoid-based beak and foot coloration. We found that adult immune function (wing web swelling response to phytohemagglutinin; PHA) in males was positively correlated with body condition during the growth period of development, rather than adult condition, and similarly that both male and female beak coloration was associated with developmental, rather than adult, body condition. We also found associations between coloration and health during adulthood; males with more carotenoid-rich beaks (a sexually attractive feature) tended to have a more robust adult PHA response and a greater antibody response to a novel antigen, while females with less carotenoid-rich beaks had greater antibody responsiveness at adulthood. In addition, male beak color changed over the course of the 24-h PHA test in proportion to the degree of PHA swelling. However, intensity of foot coloration (a trait of unknown sexual significance) was not associated with any condition, carotenoid, or immune metric for males or females. Taken together, our findings implicate key developmental components to the expression of both survival- and reproduction-related traits at adulthood, but that for a dynamic trait like beak color, there are also important adult conditions that can alter signal expression.

Effects of corticosterone treatment in laying Japanese quail

1. The effects of exogenous corticosterone on plasma corticosterone concentrations, body weight, food intake, the percentage of birds that laid an egg each day and egg weight were measured in laying Japanese quail. Data were collected from birds in the week before corticosterone treatment began, during a 21-d treatment period, and in the 22 d after treatment ended. 2. Groups of quail were treated with corticosterone at three different concentrations in their drinking water. Corticosterone intakes were calculated for each bird and birds were then assigned to 4 intake groups. The groups were 0 (control group), 0.31-0.60, 0.61-0.90, 0.91-1.50 or >1.51 mg corticosterone/bird/d. 3. Plasma corticosterone concentrations in the 4 intake groups increased from around 1 ng/ml on the day before corticosterone treatment began to maximum mean concentrations of 13-18 ng/ml on day 14 of treatment. Mean corticosterone concentrations did not change between day 14 of treatment and the day after treatment ended, and had decreased in only one of 4 intake groups one week later. 4. Mean body weight in the highest intake group remained significantly lower than in controls 22 d after corticosterone treatment ended. Whilst there was no clear effect of corticosterone on food intake during treatment, mean food intake in the three highest corticosterone intake groups was significantly lower than in controls in the week after treatment ended. The percentage of birds that laid an egg each day and egg weight were both decreased by corticosterone, and the percentage of birds that laid an egg each day remained significantly lower in the highest corticosterone intake group compared with controls in the third week after treatment ended. 5. It is suggested that elevated plasma corticosterone concentrations in quail after treatment ended were maintained by a hyperactive hypothalamo-pituitary-adrenal axis for at least one week. Although none of the negative effects of corticosterone were evident in the group of quail with the lowest corticosterone intakes, the findings of the present study show that corticosterone treatment can affect birds for up to several weeks after corticosterone intake ends.

Short-term spatial memory responses in aged Japanese quail selected for divergent adrenocortical stress responsiveness

Stress-induced glucocorticoids can dampen learning and spatial memory via neuronal damage to the hippocampus. Cognition losses can be transient (associated with acute stress episodes) or permanent as in aged individuals who show chronic glucocorticoid-induced accelerated brain aging and neurodegeneration (dementia). Thus, chronic versus acute stress effects on spatial memory responses of quail selected for reduced (low stress, LS) or exaggerated (high stress, HS) plasma corticosterone (B) response to brief restraint were assessed. Aged food-motivated male LS and HS quail were tested for 10 min in a feed-baited 8-arm radial arm maze (RAM) 1) at 255 d of age (quail who had experienced lifelong management stressors but who were otherwise never intentionally stressed; that is, chronically stressed birds), 2) on the next day post-acute stressor treatment (5 min of restraint), and 3) on the next day without treatment (acute stress recovery). The RAM tests used the win-shift procedure in which visited arms were not rebaited. Radial arm maze performance was measured by determination of the total number of arm choices made, the number of correct entries made into baited arms out of the first 8 choices, the time required to make a choice, and the number of pellets eaten. Line effects (P < 0.001 in all cases) were detected for total number of arm choices made (HS < LS), number of correct entries made into baited arms out of the first 8 choices (HS < LS), time required to make a choice (HS > LS), and number of pellets eaten (HS < LS). However, neither the effects of day of RAM testing nor its interaction with line further influenced these variables. Thus, although selection for divergent plasma B responsiveness to an acute stressor was found to be associated with severe impairment of spatial memory in aged male HS compared with LS quail, the observed spatial memory impairments (HS > LS) could not be further altered by acute stressor treatment. Line differences in cognition may reflect lifelong management-induced stress episodes that periodically produce higher plasma B responses in HS than LS quail, which underlie HS quail memory deficits, or other etiologies, or both.

Adrenocortical function of Arctic-breeding glaucous gulls in relation to persistent organic pollutants

Unpredictable changes in the environment stimulate the avian hypothalamo-pituitary-adrenal axis to produce corticosterone, which induces behavioural and metabolic changes that enhance survival in the face of adverse environmental conditions. In addition to profound environmental perturbations, such as severe weather conditions and unpredictable food shortages, many Arctic-breeding birds are also confronted with chronic exposure to persistent organic pollutants (POPs), some of which are known to disrupt endocrine processes. This study investigated the adrenocortical function of a top predator in the Arctic marine environment, the glaucous gull (Larus hyperboreus). High concentrations of organochlorines, brominated flame retardants and metabolically-derived products in blood plasma of incubating glaucous gulls were associated with high baseline corticosterone concentrations in both sexes and a reduced stress response in males. Contaminant-related changes in corticosterone concentration occurred over and above differences in body condition and seasonal variation. Chronically high corticosterone concentrations and/or a compromised adrenocortical response to stress can have negative effects on the health of an individual. The results of the present study suggest that exposure to POPs may increase the vulnerability of glaucous gulls to environmental stressors and thus could potentially compromise their ability to adapt to the rapidly changing environmental conditions associated with climate change that are currently seen in the Arctic.

Stress response of brown pelican nestlings to ectoparasite infestation

Measurement of corticosterone has become a useful tool for assessing the response of individuals to ecological stressors of interest. Enhanced corticosterone levels can promote survival of stressful events; however, in situations where a stressor persists and corticosterone levels remain elevated, the adrenocortical response can be detrimental. A potential ecological stressor for wild birds is parasitism by ectoparasites. We studied the stress response of 11-23-day-old brown pelican (Pelecanus occidentalis) nestlings by measuring plasma corticosterone levels in relation to the presence of the soft tick Carios capensis at two colonies in South Carolina in 2005. We expected to see higher baseline and stress-induced levels of corticosterone for parasitized chicks compared to those nestlings with no ticks. Although nestlings mounted a response to capture stress, tick category was not associated with corticosterone levels at either colony. Our results appear to contrast those of previous studies and indicate that the adrenocortical response of the host is likely dependent on the type of ectoparasite and the degree of infestation.

Chronic psychological stress alters body weight and blood chemistry in European starlings (Sturnus vulgaris)

One hallmark of chronic stress is a decrease in body weight that rebounds once chronic stress is alleviated. We applied chronic psychological stress by exposing European starlings (Sturnus vulgaris) to a previously validated chronic stress protocol (CSP) consisting of 4 different randomly applied stressors per day. Experimental design consisted of a 21 day CSP (CSP1), a 60day recovery (R1), a second 14 day CSP (CSP2), and a second 30 day recovery (R2). Body weight decreased by approximately 5% during CSP1, but overshot to 5-10% above initial body weight during R1. To investigate underlying mechanisms, we periodically measured 12 biochemical analytes, including aspartate aminotransferase (AST), creatine kinase (CK), bile acids, total protein, albumin, globulin, glucose, uric acid, calcium (Ca(++)), phosphorus (PHOS), potassium (K(+)), and sodium (Na(+)). AST and CK increased at the beginning of CSP1, suggesting muscle breakdown. Additionally, decreases in albumin and total protein paired with stable uric acid, but no associated change in glucose, suggested protein breakdown as a secondary energy source. Changes in blood parameters that occurred during CSP1 did not reverse during R1. During CSP2 and R2, weight loss and gain occurred in different proportions. CSP2 produced an approximate 15% decrease in body weight, but R2 resulted in only re-gaining 5% of this weight, although this was equivalent to the pre-CSP1 weight. In summary, protein metabolism appeared to mediate weight loss during chronic stress, but over-gaining weight was not a good indicator of recovery.