Habituation of the corticosterone response of ducks (Anas platyrhynchos) to daily treadmill exercise

Feather Corticosterone Measurements of Greater Flamingos Living under Different Forms of Flight Restraint

Deflighting zoo birds is a practice that receives increasing criticism due to its presumed incompatibility with animal welfare. To our knowledge, this is the first approach to address this problem in a scientific way. To do this, we compared feather corticosterone (CORTf) from Greater Flamingos (Phoenicopterus roseus, n = 151) of different flight status (i.e., pinioned, feather clipped, airworthy) from twelve different zoological institutions. To complement the hormone measurements, behavioral observations (scan samplings) were conducted prior to feather sampling within the presumed time frame of feather growth. We hypothesized that CORTf of the deflighted flamingos would differ from CORTf of their airworthy conspecifics. No significant difference in CORTf was found between the three groups, and our hypothesis was rejected. However, the impact of the institution itself (i.e., the housing conditions) proved to be the most dominant variable (variance between the institutions = 53.82%). Due to high variability, the behavioral observations were evaluated descriptively but did not give rise to doubt the findings in CORTf. Therefore, we assume that the method of flight restraint of Greater Flamingos does not have a measurable effect on CORTf. We consider this model for evaluating animal welfare of zoo birds a useful tool and provide ideas for further adjustments for consecutive studies.

Age-related differences in baseline and stress-induced corticosterone in Florida scrub-jays

In physiological studies of free-living species, it is essential to consider the context of the life history stage at which an individual was observed in order to link measures of physiology with ecological parameters. One such measure that is important to consider is the age of an individual. We tested whether baseline or stress-induced corticosterone levels vary with age in free-living Florida scrub-jays (Aphelocoma coerulescens) during the pre-breeding period. Corticosterone (CORT), the primary avian stress hormone, is released in response to stressful stimuli, and stimulates gluconeogenesis; however, it also serves as a chemical messenger that can influence other physiological processes, reproduction, and behavior. We monitored both baseline CORT levels longitudinally throughout a five-year period and stress-induced CORT responses over a shorter two-year period. We predicted that older jays would have lower baseline CORT levels and a dampened stress response compared to younger birds, as has been shown in other avian species. We found no significant differences in baseline CORT levels with age. We found a decrease in total corticosterone responses to a stressor with age, however, the oldest birds in the population showed greater total corticosterone responses to a stressor. These results may be a product of age-related changes in physiological processes related to the stress response or a result of selection acting on the population, resulting in only the most responsive individuals surviving to old age.

Intensity and duration of corticosterone response to stressful situations in Japanese quail divergently selected for tonic immobility

Two genotypes of Japanese quail have been divergently selected since the 1980s for long (LTI) or short (STI) duration of tonic immobility [Mills, A.D., Faure, J.M., 1991. Divergent selection for duration of tonic immobility and social reinstatement behavior in Japanese quail (Coturnix coturnix japonica) chicks. J. Comp. Psychol. 105(1), 25-38.], an unlearnt catatonic state characteristic of a behavioral fear response ([Jones, R.B., 1986. The tonic immobility reaction of the domestic fowl: a review. World's Poult. Sci. J. 42(1), 82-97.]; [Mills, A.D., Faure, J.M., 1991. Divergent selection for duration of tonic immobility and social reinstatement behavior in Japanese quail (Coturnix coturnix japonica) chicks. J. Comp. Psychol. 105(1), 25-38.]). The results of several behavioral tests conducted in LTI and STI quail have led to the conclusion that LTI quail are more fearful than STI quail [Faure, J.M., Mills, A.D., 1998. Improving the adaptability of animals by selection. In: Grandin, T. (Eds.), Genetics and the behavior of domestic animals. Academic Press, San Diego, pp. 235-264.]). However, few studies to date have focused on the Hypothalamic-Pituitary-Adrenal (HPA) axis response to stressful situations in LTI and STI quail, although the HPA axis is involved in fear responses [Siegel, H.S., 1971. Adrenals, Stress and the Environment. World's Poult. Sci. J. 27, 327-349.]. The corticosterone (CORT) response to various putatively stressful situations was therefore assessed in LTI and STI genotypes of quail in order to investigate their HPA axis reactivity to stress. Repeated induction of TI or 1 min manual restraint induced significant and comparable increases in CORT levels in both genotypes as a TI response. On the other hand, higher CORT responses were found in STI than in LTI quail when the manual restraint period lasted for 2 min or after restraint in a crush cage. Maximum CORT responses and genotype differences were maintained throughout the latter test even when it lasted for 120 min. Investigation of the CORT response to a single TI episode showed that CORT levels at the end of TI were negatively correlated with TI duration. Other experimental contexts consisting of isolation in a familiar or novel environment or the presentation of a novel object induced slight but significant and comparable increases in CORT response in both genotypes, whereas change of cagemates did not. In conclusion, the present findings indicate that differences in HPA axis response are observed between LTI and STI genotypes when quail are submitted to intense stressors, resulting in a high and prolonged CORT response. By contrast, plasma corticosterone concentrations do not differ between STI and LTI quail in response to stressful situations of lower intensity, which evoke responses limited in amplitude and duration. Genetic selection for divergent duration of TI has thus affected the HPA axis response to stress, and LTI and STI quail constitute an interesting model to investigate genetic variability of HPA axis activity in birds. More specifically, these genotypes of quail could be used to investigate the occurrence of functional differences at different levels of the HPA axis in order to explain the present findings.

Ontogeny of the hypothalamo-pituitary-adrenocortical axis in the chicken embryo: a review

The embryo of the domestic fowl (Gallus domesticus) tenders one distinctive advantage over general mammalian models for investigating the development of the hypothalamo-pituitary-adrenocortical (HPA) axis. This is the relative simplicity with which the embryonic endocrine environment can be influenced without confounding maternal influences. The ease of direct manipulation of the embryonic endocrine system has facilitated analysis of the development and function of the HPA axis in the chick embryo. As the chick embryo develops, functional activation of the adrenal gland is regulated at three different levels: the adrenal gland itself, the anterior pituitary, and the hypothalamus. The adrenal gland appears capable of independent secretion of glucocorticoids from day 8 until shortly after day 14 of embryonic development, at which point the pituitary influences adrenocortical activity. Around the same age, the hypothalamic level of control also begins. The information covered in this review will describe the major steps in the development of the HPA axis in the chicken embryo and show that the chicken has an emblematic HPA neuroendocrine axis.

Force-feeding procedure and physiological indicators of stress in male mule ducks

1. The effects of the force-feeding procedure and its different components on various physiological indicators of acute and chronic stress were investigated in male mule ducks before and during a 12-d cramming period. 2. The highest concentration of corticosterone were measured after injection of ACTH agonist, during the pre-experimental period when the ducks were still housed in collective floor pens and at the time of transfer. 3. During the cramming period, corticosterone measured before and after force-feeding did not differ significantly though there was a non-significant trend towards an increase in certain cases. 4. The different components of force-feeding, including manipulation, intubation, force-feeding with a standard or a large amount of food had no significant effect upon corticosterone concentrations. 5. There was no indication from ACTH agonist challenge either of a change in adrenal sensitivity or a change in its responsiveness. 6. The heterocyte-lymphocyte ratio measured before and at the end of the cramming period did not differ significantly. 7. In conclusion, we observed no significant indication that force-feeding is perceived as an acute or chronic stress by male mule ducks, in our experimental conditions. Nevertheless, it remains to be shown that their adrenocorticotropic axis is responsive to acute stressors.

Voluntary running in male S5B/P1Ras rats fed high fat or high carbohydrate diets

Nineteen week-old male S5B/P1Ras (S5B) rats were randomly assigned to one of 4 groups as follows: (a) activity wheel access (running)/high fat diet (RF); (b) no activity wheel access (non-running)/high fat diet (NRF); (c) activity wheel access (running)/high carbohydrate diet (RC); and (d) no activity wheel access (non-running)/high carbohydrate diet (NRC) for the seven weeks duration of the experiment. Throughout the 7 wk of the experiment, rats ran more during subsequent weeks than they did the previous week. RC rats ran more than RF rats as measured by the running slopes. All groups of rats lost weight at the initiation of the experiment but significantly more weight was lost by running rats than their nonrunning counterparts. The inguinal, epididymal and perirenal/retroperitoneal (P/R) fat depots weighed significantly less in the running than in the nonrunning groups. From among the 3 fat depots, the difference was greatest in the P/R depot. There were no diet or voluntary activity effects on plasma corticosterone concentrations except at week 2 when running rats had higher concentrations than nonrunning rats.

Stimulation of corticosterone release in the fowl by recombinant DNA-derived chicken growth hormone

The effects of recombinant DNA-derived chicken growth hormone (rcGH) on plasma corticosterone in young broiler cockerels were investigated. A single injection of 200 micrograms/kg rcGH significantly increased plasma corticosterone concentrations 2 hr (but not 20 or 40 min) after treatment. Administration of 10 or 100 micrograms/kg rcGH also significantly increased plasma corticosterone levels after 2 hr, with the higher dose eliciting greater responses. Chronic treatment with seven daily injections of the same doses of rcGH gave similar increases in plasma concentrations of corticosterone. No obvious difference in magnitude of plasma corticosterone was observed between acute and chronic exposure to rcGH. In a further experiment in which serial blood sampling was performed after a single injection or five daily injections of vehicle or 200 micrograms/kg rcGH, there were significant increases in plasma corticosterone concentrations 40 min after acute rcGH treatment and 40 and 80 min after chronic treatment when compared with plasma corticosterone concentrations of vehicle-injected controls. However, the increases could have incorporated a stress response due to repeated sampling because the control birds also showed elevated plasma corticosterone concentrations. The corticosterone response did not diminish with repeated GH challenge. These results suggest that GH may play a role in the acute regulation of corticosterone secretion in intact chickens.

Physiological and glucocorticoid response to treadmill exercise of Holstein heifers

Effect of exercise for 8 wk prepartum on heart rate, respiration rate, rectal temperature, and serum glucocorticoid concentration was determined for nine Holstein heifers. Exercise was on a treadmill 30 min daily, 5 d/wk, for approximately 8 wk. Physiological measures were taken at rest and immediately postexercise; blood samples were taken via jugular vein cannulas at 2-h intervals 26 h preexercise, at 10-min intervals during exercise and 21.5 h postexercise, all at initiation of the experiment and again near the end of pregnancy. The three physiological measures increased during exercise at both the initiation and termination of the 8-wk exercise period. Mean serum glucocorticoids of heifers increased from 5.4 to 21.3 ng/ml during initial exercise but increased from 4.4 to 5.2 ng/ml following approximately 8 wk exercise. These glucocorticoid data mimic trends found in other species, i.e., physically fit subjects or animals trained to chronic exercise have lower glucocorticoids than sedentary or untrained subjects during intense or exhaustive exercise.

Plasma corticosterone in chicks reared under several lighting schedules

Plasma corticosterone was determined by radioimmunoassay in 6-7-week-old male broiler type chicks, reared under several carefully controlled lighting regimes. When subjects were grouped by photoperiod of rearing, chicks reared in darkness had significantly lower hormone levels than diurnal controls, or than subjects reared in continuous light. Around-the-clock sampling revealed a diurnal corticosterone rhythm, with high daytime levels and lower night-time levels. This rhythm appeared to be retained in constant light, although phase shifted or free running. Neither analysis by light intensity level nor by lights on/lights off status at the time of blood sampling revealed differences in plasma corticosterone between the experimental groups which could be attributed to these factors.

Adrenocortical responses of pigeons (Columba livia) to treadwheel exercise

Voluntary flight has previously been observed to stimulate adrenocortical activity in pigeons and in the present study increased circulating corticosterone levels were observed in adult feral pigeons forced to exercise in a treadwheel. The magnitude of the corticosterone response to treadwheel exercise was related to the speed of the moving drum, and hence to the work rate involved. Rapidly increasing the ambient temperature also stimulated corticosterone secretion in pigeons and masked the stimulatory effect of exercise. Treadwheel locomotion may serve as a laboratory model for the endocrine physiology of exercise and complements studies on flight.

Flight stimulates adrenocortical activity in pigeons (Columba livia)

The influence of long-distance flight on corticosterone secretion has been examined in trained racing pigeons. Flights of 315-561 min from release sites 115-557 km from the home loft greatly increased the circulating corticosterone concentration in comparison with the levels in nonexercised controls sampled before release or bled in the loft at the times of release or arrival. The increase in corticosterone concentration was unrelated to the distance flown or duration of flight. Flights of less than 1 min duration (from release sites 100 m from the loft) increased the corticosterone concentration, in comparison with that in the loft controls, but to levels much lower (P less than 0.001) than those following long-distance flights and to concentrations similar to those in birds that were returned to the loft by hand.

Transitory corticosterone responses of ducks (Anas platyrhynchos) to exercise

Horizontal treadmill exercise induced a marked (P less than 0.001) but transitory increase in the level of circulating corticosterone in the plasma of adult male ducks. The decline in corticosterone concentration during exercise is unlikely to be due to a depletion of adrenocortical stores since a marked (P less than 0.001) corticosterone response to adrenocorticotrophin (ACTH) administration was observed immediately after exercise, and was of similar magnitude to that induced in nonexercised controls. The corticosterone response to repeated exercise is also transitory, habituating completely within 28 days of the start of daily training. The corticosterone response (P less than 0.001) to ACTH challenge is not, however, diminished by training. These results indicate that the habituation of the corticosterone response to either acute or repeated exercise is due to a reduction in endogenous ACTH secretion. A similar mechanism appears to be responsible for the habituation of the corticosterone response to handling and confinement in nonexercised control birds. A marked (P less than 0.001) increase in the level of circulating corticosterone was, however, elicited when these birds were exercised, indicating that despite adaptation to handling and confinement the birds remained responsive to the novel stressor of exercise. The corticosterone response of these birds was, however, less than that in untrained birds indicating that the corticosterone response in untrained birds is due to both workload and the stress of handling and confinement.

Adrenocortical responses to novel stressors in acutely or repeatedly starved chickens

The effect of starvation on the corticosterone responses of immature cockerels to acute, novel stress has been determined. The marked corticosterone responses of fed birds to either horizontal treadmill exercise (0.04 km/hr) or intravenous adrenocorticotrophic hormone (ACTH) administration (P less than 0.001 in both cases) were reduced by starvation (P less than 0.01 and P less than 0.001, respectively). This reduction did not appear to be due to either feedback inhibition of corticosterone on the hypothalamus or pituitary, or to reduced adrenal responsiveness to endogenous ACTH. Starvation significantly elevated the basal level of circulating corticosterone (P less than 0.001), but the magnitude of this elevation and the level of corticosterone attained were less (P less than 0.05) in birds that were accustomed to starvation. This habituation of adrenocortical activity may be due to reduced pituitary ACTH secretion, and was specific in that the corticosterone responses to novel stressors were unaffected.

Stress and adrenal function

The natural environment is composed of various potentially hostile stressors. It is a basic requirement of life that the cells of an organism must be maintained within closely defined physiological limits. The maintenance of a constant interior mileu results from physiological and behavioural homeostatic adaptations. The physiological regulation of homeostatis is achieved by complex endocrine interactions, principally by the hormones secreted from the adrenal glands. In this brief review the responses of the avian adrenal glands to stressful stimuli, the mechanism of adrenal activation, and the function of the adrenal responses will be considered.

Adrenocortical and adrenomedullary responses of fowl to treadmill exercise

Adrenomedullary and adrenocortical responses of 40-day-old cockerels to treadmill exercise (0.4 km/hr, 0 degrees incline) were determined. Plasma concentrations of adrenaline were increased above both resting and control levels (P less than 0.001) after 30 min exercise and continued to increase (P less than 0.01) until the cessation of exercise. Plasma noradrenaline and dopamine levels were increased after 60 min of exercise (P less than 0.01 and 0.05, respectively). The adrenaline component of the plasma catecholamine response increased significantly above that of noradrenaline (P less than 0.001). Plasma corticosterone levels were also increased (P less than 0.001) during exercise and were closely correlated with plasma adrenaline concentrations. Exercise depleted (P less than 0.01) adrenal stores of adrenaline, which were inversely proportional to plasma adrenaline concentrations (P less than 0.001). Neither adrenal noradrenaline nor dopamine were significantly correlated with their plasma levels. These results suggest that adrenocortical (corticosterone) and adrenomedullary (adrenaline) responses during exercise may occur in response to similar stimuli or may be interrelated.

Adrenocortical adaptation to chronic intermittent stress in hemispherectomized pigeon

Hemispherectomized pigeons were exposed daily to electrical footshocks delivered for 15 sec, at the same hour, for 8 weeks. Serial blood samples were obtained through a chronic vascular catheter. The adrenocortical response to chronic intermittent stress was measured kinetically at one week intervals. The initial response including several successive peaks of plasma corticosterone progressively adapted: Late peaks disappeared and only the first one subsisted 12-14 min after stressor application; this first peak diminished in magnitude; furthermore, an anticipatory peak occurred, starting 14 min before stress. In pigeons lesioned in the anterior dorsomedial thalamus, the only response to the stressor was of the single peak (12-14 min) type without any development of anticipatory conditioned response. This phenomenon was consistant all over the experimental period. Thalamic-hypothalamic interrelationships may be suggested to provide neuronal loops that underlie the long lasting, pulsatile repetitive components of the adrenocortical response to acute stress and also the adaptative process of such a response to chronic intermittent stress, including a conditioned, anticipatory endocrine activation.

Plasma constituents and body weights of Japanese quail (Coturnix coturnix japonica) selected for twelve generations for plasma cholesterol responses to adrenocorticotropin

Japanese quail were selected bidirectionally over 12 generations for plasma cholesterol (PC) responses to adrenocorticotropin (ACTH). In addition to the selected trait, plasma corticosteroids (PCS), triglycerides (PT), and glucose (PG) were measured before and after 3 daily injections of ACTH. The quail were also weighed at 31 days of age. By the 12th generation of selection, when measurements were expressed as deviations from the randombred control (C) line from which the selected lines had been derived, there was a difference in PC of approximately 55% between the high response (HR) and the low-response (LR) lines. Pre-ACTH PCS levels increased in all three lines over generations; however, relative to the C line, there was no difference between selected lines. The 3 days of ACTH injection depressed PCS levels. Relative to the C line, pre- and post-ACTH levels of PT were higher in the HR line than in the LR line, and the LR line declined linearly over generations. Levels of PG did not change over generation in the selected lines; however, pre-ACTH levels of PG tended to be higher in the LR line than in the HR line in all generations. Body weights of the HR line at 31 days remained almost exactly the same as the C line, but those of the LR line declined linearly over the 12 generations of selection. These studies demonstrated that the PC response to ACTH was moderately heritable (h2 approximately equal to .20).