The effects of pre-hatch elevated corticosterone and post-hatch restrictive food availability on the HPA axis development of mallard ducks (Anas platyrhynchos).

Environmental changes can be stressors (altered habitat and food supply, climate change, etc.) to wild animals. Stressors trigger the hypothalamic pituitary adrenal (HPA) axis to release corticosterone (CORT) which modifies energy homeostasis. During nesting, stressed females can deposit increased concentrations of CORT into eggs, altering egg viability and offspring characteristics, constituting a significant mechanism regulating population productivity in subsequent generations. In this study, increased maternal disposition of CORT was mimicked through a 15 ng/g in ovo injection of CORT into mallard duck eggs. Growth and HPA axis function were measured during post-hatch development. For growth, changes in mass were compared at hatch, 7 weeks and 11 weeks. The HPA axis was assessed at seven weeks by measuring CORT at baseline, followed by restraint stress, dexamethasone (negative feedback) and ACTH (maximal adrenal capacity) challenges. At eleven weeks of age, ducks were subjected to a 6-day 25% feed reduction to simulate a poor quality environment to evaluate response to a chronic stressor by comparing CORT at baseline and after restraint stress. Growth and CORT concentration did not differ between treatments at seven weeks or after feed restriction (11 weeks). The CORT dosage administered did not appear to affect HPA axis development in ducklings. Mallards are a highly adaptable species and may have overcome any early alterations to their phenotype. Further research is needed to determine the effects of increased maternal CORT on growth and the development of the HPA axis in ducks. SUMMARY STATEMENT: This study examines how maternal stress (simulated through elevated corticosterone in ovo) and post-hatch chronic stressors (food restriction) affect the development of the HPA axis in a precocial bird.

Utilizing NMR fecal metabolomics as a novel technique for detecting the physiological effects of food shortages in waterfowl.

Metabolomics is the study of small, endogenous metabolites that participate in metabolic reactions, including responses to stressors. Anthropogenic and environmental changes that alter habitat and food supply can act as stressors in wild waterfowl. These alterations invoke a series of physiological processes to provide energy to restore homeostasis and increase survival. In this study, we utilized fecal metabolomics to measure metabolites and identify pathways related to a 6-day feed restriction in captive mallard ducks (Anas platyrhynchos, n = 9). Fecal samples were collected before (baseline) and during feed restriction (treatment). H1 Nuclear Magnetic Resonance (NMR) spectroscopy was performed to identify metabolites. We found that fecal metabolite profiles could be used to distinguish between the feed-restricted and baseline samples. We identified metabolites related to pathways for energy production and metabolism endpoints, and metabolites indicative of gut microbiota changes. We also demonstrated that mallard ducks could utilize endogenous reserves in times of limited caloric intake. Fecal metabolomics shows promise as a non-invasive novel tool in identifying and characterizing physiological responses associated with stressors in a captive wild bird species.

Evaluation of intravenous T-61 as a euthanasia method for birds.

The use of T-61 as a sole euthanasia agent for birds was investigated. Nine broiler chickens (Gallus gallus domesticus) were euthanized by intravenous T-61 and assessed for insensibility [brainstem reflexes: nictitating membrane reflex (NIC), palpebral blink reflex (PAL)], brain death [isoelectric electroencephalogram activity (EEG)], cessation of audible heartbeat, and abnormal electrocardiogram. Birds were considered dead when the heart rate was less than 180 beats/minute with an isoelectric EEG. No vocalization or wing flapping occurred. Both NIC and PAL were lost 10.5 s from start of injection and audible heartbeat ceased at 24.5 s. Latency to isoelectric activity was 16.6 s. All but 1 bird died within 60 s. Rapid induction of insensibility meant birds did not experience pain and distress within 10.5 s from start of injection and birds were not conscious during cardiac and circulatory arrest. Intravenous injection of T-61 is an effective and efficient euthanasia method for birds.

Évaluation du T-61 intraveineux comme méthode d'euthanasie pour les espèces aviaires. La présente étude visait à évaluer l'utilisation du T-61 comme seul agent d'euthanasie pour les oiseaux. Neuf poulets de chair (Gallus gallus domesticus) ont été euthanasiés par injection intraveineuse de T-61 et évalués pour leur insensibilité [réflexes du tronc cérébral : réflexe de la membrane nictitante (NIC) et réflexe palpébral (PAL)], mort cérébrale [activité isoélectrique de l'électroencéphalogramme (EEG)], arrêt du rythme cardiaque audible et électrocardiogramme (ECG) anormal. Les oiseaux étaient considérés comme morts lorsque la fréquence cardiaque (ECG) était inférieure à 180 battements par minute avec un EEG isoélectrique. Aucune vocalisation ou battement d'aile ne s'est produit. Les réflexes NIC et PAL ont été perdus 10,5 s après l'injection et le rythme cardiaque audible a cessé à 24,5 s. La latence jusqu'à l'activité isoélectrique était de 16,6 s. Tous les oiseaux sauf un sont morts dans les 60 s. L'induction rapide de l'insensibilité signifiait que les oiseaux étaient incapables de ressentir de la douleur et de la détresse dans les 10,5 secondes suivant l'injection et que les oiseaux n'étaient pas conscients pendant un arrêt cardiaque et circulatoire. L'injection intraveineuse de T-61 est une méthode d'euthanasie efficace et efficiente pour les oiseaux.(Traduit par Dr Serge Messier).

Experimental relationships between levels of corticosterone in plasma and feathers in a free-living bird.

Integrated measures of corticosterone (CORT), such as from feathers (CORTf), have intuitive appeal because they incorporate both the duration and amplitude of glucocorticoid secretion. An association between CORTf and plasma CORT has never been shown in wild birds, and it is unclear as to when and whether these measures should be correlated, given that they are fundamentally different yet related measures of physiology. We hypothesized that CORTf should correlate with instantaneous measurements of plasma CORT when the latter reflect sustained changes in the activity of the hypothalamic-pituitary-adrenal (HPA) axis. To test this, we experimentally manipulated levels of plasma CORT in wild nestling tree swallows (Tachycineta bicolor) using 5 day time-release CORT pellets, and measured plasma CORT and growth parameters before, during and at the end of hormone manipulation (days 7, 9 and 11 post-hatch, respectively). CORTf and plasma CORT were significantly positively related only when the latter was at its highest and most variable among individuals (day 9). A similar relationship was expected at day 11, but plasma CORT had returned to near-original levels. Nestlings with higher CORTf were smaller, lighter and less likely to fledge, but we did not detect seasonal effects on CORTf. Our results clearly demonstrate that CORTf from free-living birds can reflect plasma CORT, but correlations may not always be expected, especially if elevations in plasma CORT are relatively modest and of short duration. Our work suggests that CORTf is best used to study the activity of the HPA axis over relatively long time frames and can be used effectively to advance avian ecology.

Corticosterone in relation to tissue cadmium, mercury and selenium concentrations and social status of male lesser scaup (Aythya affinis).

Combined lesser scaup (Aythya affinis) and greater scaup (A. marila) populations have declined steadily from the 1970s. Accompanying the population decline have been two shifts in lesser scaup demographics: a decrease in the proportion of young birds and an increase in male to female ratio. In addition, there are concerns about potential effects of contaminants and trace elements. These metals may influence the stress response and corticosterone secretion. We examined impacts of cadmium, selenium and mercury on the stress response in relation to social status in male lesser scaup near Yellowknife, NWT May to June 2004 and 2005. Kidney cadmium and liver selenium and mercury ranged 0.78-93.6, 2.12-9.64, and 0.56-3.71 microg/g, dry weight, respectively. Results suggest that corticosterone release may be influenced by complex contaminant interactions in relation to body condition and body size. When cadmium was high and birds were in good body condition, there was a negative relationship between liver selenium and corticosterone (R(2) = 0.60, n = 10, P = 0.008) but not in birds with poor body condition (R(2) = 0.07, n = 9, P = 0.50). Unfortunately we were unable to draw any conclusions about metals and social status in relation to corticosterone or glucose and T(4). This study emphasizes the complex nature of biological systems and the importance of considering interactions to characterize effects of metals.

Assessment of the analgesic effects of ketoprofen in ducks anesthetized with isoflurane.

OBJECTIVE: To determine whether administration of ketoprofen would have analgesic effects in spontaneously breathing ducks anesthetized with isoflurane. ANIMALS: 13 healthy adult wild-strain Mallard ducks. PROCEDURE: Each duck was anesthetized twice in a crossover study design with 6 days between randomized treatments. Ducks were given ketoprofen (5 mg/kg, IM) or saline (0.9% NaCl) solution after a constant plane of anesthesia was established. Analgesia was assessed by measuring heart and respiratory rates and duration of application of a noxious stimulus. The noxious stimulus was applied 30, 50, and 70 minutes after drug administration and was maintained until gross purposeful movements were seen or for a maximum of 5 seconds. RESULTS: At all 3 evaluation times, heart rate increases in response to the noxious stimulus were greater when ducks were given saline solution than when they were given ketoprofen. The increase in respiratory rate in response to the noxious stimulus was greater when ducks were given saline solution than when they were given ketoprofen only 70 minutes after drug administration. When ducks were given ketoprofen, duration of the noxious stimulus was significantly longer 50 and 70 minutes, but not 30 minutes, after drug administration. CONCLUSIONS AND CLINICAL RELEVANCE: Ketoprofen reduced the increases in heart and respiratory rates associated with application of a noxious stimulus in spontaneously breathing adult Mallard ducks anesthetized with isoflurane delivered at approximately 2.9%, suggesting that ketoprofen had analgesic effects in these ducks. The onset of analgesic effects may be longer than 30 minutes in some ducks.