Fecal Corticosterone Levels Research Articles

Chronic corticosterone administration alters synaptic mitochondrial function within the hippocampus of C57Bl/6NTac mice

Chronic activation of the hypothalamic-pituitary-adrenal axis increases circulating corticosterone levels, causing a host of downstream behavioral, molecular, and metabolic changes. Here, we assess the effects of chronic exogenous CORT administration on changes in behavior and mitochondrial respiration in hippocampal synaptosomes of male and female mice. Adult male (n = 15) and female (n = 17) C57Bl/6NTac mice were given 35ug/mL CORT or vehicle dissolved in their drinking water for 21 consecutive days. Chronic CORT increased piloerection in males only. Although volume of CORT-containing water consumed was similar between males and females, circulating plasma and fecal corticosterone levels were only elevated in CORT-exposed males. Behavioral effects of CORT were evident in the Y-maze such that CORT caused a decrease in direct revisits in both sexes. There was no observed presentation of anxiety-like behavior following chronic CORT administration. Functional hippocampal synaptosomes were analyzed for mitochondrial respiration using Agilent's Cell Mito Stress test. Chronic CORT caused a decrease in synaptic mitochondria basal respiration, maximal respiration, proton leak, and ATP production in both sexes. Despite only observing an effect of chronic CORT on corticosterone concentrations in fecal and blood samples of males, chronic CORT induced marked changes in hippocampal synaptic mitochondrial function of both sexes. These data highlight the importance of considering effects of stress hormone exposure on neural function even in the absence of measurable peripheral elevations in females.

Use of Micropipette-Guided Drug Administration as an Alternative Method to Oral Gavage in Rodent Models.

Oral gavage (OG) with the use of a cannula attached to a syringe is one of the most common methods used to deliver precise dosing of compounds to the stomach of research animals. Unfortunately, this method comes with difficulties for both the operator and the research animal. Studies have shown that OG may lead to complications, including esophagitis, perforation of the esophagus, and inadvertent tracheal drug administration. In addition, OG is associated with increased plasma and fecal corticosterone levels (due to stress), altered blood pressure, and increased heart rate, which could negatively influence or bias study results. A previously developed alternative method termed micropipette-guided drug administration (MDA) incentivizes the animal to consume treatments readily in a minimally invasive manner. Herein, we present examples of the use of the MDA technique with treatments reconstituted in different vehicles and demonstrate effective delivery of the varied treatments to multiple different mouse strains. We further demonstrate that MDA is a technique that decreases the timing and invasiveness of drug administration and does not affect the gut microbiome composition as assessed by quantitative analysis of core gut microbial species. Overall, MDA may offer a less stressful and effective alternative to OG.

Differences in Fluid, Electrolyte, and Energy Balance in C57BL/6J Mice (Mus musculus) in Metabolic Caging at Thermoneutral or Standard Room Temperatures.

The Guide for the Care and Use of Laboratory Animals recommends mice be pair or group housed and provided with nesting materials. These provisions support social interactions and are also critical for thermoregulatory behaviors such as huddling and burrowing. However, studies of fluid and electrolyte balance and digestive function may involve use of metabolic caging (MC) systems in which mice are housed individually on wire-mesh floors that permit quantitative collection of urine and feces. MC housing prevents mice from performing their typical huddling and burrowing behaviors. Housing in MC can cause weight loss and behavioral changes in rodents. Here, we tested the hypothesis that MC housing of mice at standard room temperature (SRT, 22 to 23 °C) exposes them to cold stress, which causes metabolic changes in the mice as compared with standard housing. We hypothesized that performing MC studies at a thermoneutral temperature (TNT, 30 °C) would minimize these changes. Fluid, electrolyte, and energy balance and body composition were assessed in male and female C57BL/6J mice housed at SRT or TNT in MC, static microisolation cages, or a multiplexed metabolic phenotyping system designed to mimic static microisolation cages (Promethion, Sable Systems International). In brief, as compared with MC housing at SRT, MC housing at TNT was associated with lower food intake and energy expenditure, absence of weight loss, and lower urine and fecal corticosterone levels. These results indicate that housing in MC at SRT causes cold stress that can be mitigated if MC studies are performed at TNT.

Adulthood effects of developmental exercise in rats.

Exercise is known to promote efficient function of stress circuitry. The developing brain is malleable and thus exercise during adolescence could potentially exert lasting beneficial effects on the stress response that would be detectable in adulthood. The current study determined whether adolescent wheel running was associated with reduced stress response in adulthood, 6weeks after cessation of exercise. Male and female adolescent rats voluntarily ran for 6weeks and then were sedentary for 6weeks prior to 10days of chronic restraint stress in adulthood. Fecal corticosterone levels were measured during stress, and escape from the restraint tube was assessed on the final day as a proxy for depressive-like behavior. Anxiety-like behavior was measured 24h later with the elevated plus maze and locomotor behaviors with the open field. Brain and body measurements were taken immediately following behavioral testing. Developmental exercise and adulthood stress both exerted independent effects on physiological and behavioral outcomes in adulthood. Exercise history increased the odds ratio of escape from restraint stress in males, but did not influence other stress-induced behaviors. In summary, exercise early in life exerted lasting effects, but did not substantially alter the adulthood response to restraint stress.

Effects of limited bedding and nesting on postpartum mood state in rats.

This study examined the effect of limited bedding and nesting (LBN) stress on postpartum anhedonia, maternal behaviors, anxiety-like behaviors, and neuroendocrine and neuroimmune function as a potential model of postpartum depression. Dams underwent sucrose preference tests prior to breeding, during gestation and again postpartum, to examine the potential onset of anhedonia. On embryonic day 19, dams were placed into either a LBN or control housing condition. Contrary to our predictions, LBN stress had no effect on postpartum sucrose preference. We also found no effect of LBN condition on fecal estradiol or corticosterone levels, both of which increased at birth and decreased postpartum. Regardless of housing conditions, approximately 40% of new mothers exhibited a decrease in sucrose preference, while others show no change, suggesting an individual susceptibility to postpartum anhedonia. In a separate cohort of LBN and control dams, we measured pup retrieval, hoarding behavior, elevated plus maze (EPM), and marble burying. LBN dams exhibited increased anxiety, associated with decreased time spent in the open arms of the EPM. We also measured a significant increase in IL-6 expression in the dorsal hippocampus and medial prefrontal cortex of postpartum dams compared to nonpregnant dams. These findings suggest that while LBN stress has effects on anxiety and maternal care, it does not induce postpartum anhedonia. Rather, there are inherent differences in susceptibility to anhedonia in individual dams, and future studies should be conducted to better understand individual vulnerability and resilience to postpartum anhedonia.

Effects of Housing Density on Reproductive Performance, Intracage Ammonia, and Welfare of Mice Continuously Housed as Breeders in Standard Mouse and Rat Caging.

Maintaining compliance with cage density recommendations in The Guide for the Care and Use of Laboratory Animals precludes continuous trio breeding in standard-sized mouse cages. This study evaluated and compared several parameters of reproductive performance, intracage ammonia concentration, and fecal corticosterone levels in 2 strains of mice, C57BL/6J (B6) and B6.129S(Cg)-Stat1tm1Dlv/J (STAT1-/-), housed as continuous breeding pairs or trios in standard-sized mouse cages, and continuous breeding trios in standard-sized rat cages. Reproductive performance data indicated that STAT1-/- trios raised in rat cages weaned significantly more pups per litter than did STAT1-/- trios raised in mouse cages, and B6 mice had higher pup survival rates at weaning than did STAT1-/- mice in mouse cages housing continuous breeding trios. In addition, the Production Index was significantly higher for B6 breeding trios in rat cages than for B6 trios in mouse cages. Intracage ammonia concentration increased with cage density, with significantly higher ammonia concentrations in mouse cages housing trios compared with rat cages housing trios. However, fecal corticosterone levels did not differ significantly regardless of genotype, breeding configuration, or cage size, and daily health checks revealed no clinical abnormalities under any of the conditions evaluated. These results suggest that, although continuous trio breeding in standard-sized mouse cages does not seem to compromise mouse welfare, it offers no advantage in reproductive performance compared with pair breeding, and in some cases, it might be disadvantageous in this regard. Further, high intracage ammonia in mouse cages containing breeding trios might necessitate more frequent cage changes.

Physiological and behavioural assessments of stress levels in owls housed at owl cafes

AbstractOwl cafes, where customers view and interact with owls, have become popular in Japan. There are multiple aspects of the environment which may be stressful to nocturnal owls, including lighting, tethering and frequent interactions with humans but, to date, welfare has not been investigated. This preliminary study examines the effects of owl cafes and customers on the physiological stress (faecal corticosterone levels [FCL]) and behaviour of the owls. Seven eagle owls (Bubo bubo) and two African scops owls (Ptilopsis leucotis), in two cafes, were studied over an eight-day period. Cafe A (n = 5) was closed for one day per week, whilst cafe B (n = 4) was open every day. In cafe A there was higher FCL in owls during open days than closed days suggesting that the conditions on open days increase stress in owls. Eight of nine owls showed evidence of some aversion or avoidance of humans, whilst no affiliative behaviours were observed. The number of visitor interactions was not associated with the level of physiological stress; and when comparing owls, there was a tendency for individual owls with a higher percentage of aversive responses to customers to also have higher FCL. Close human interactions of a negative nature, that result in aversion, may be a significant stressor, but further research is required.

Male and Female C57BL/6 Mice Respond Differently to Awake Magnetic Resonance Imaging Habituation.

Traditionally, preclinical magnetic resonance imaging (MRI) has been performed in anesthetized animals. However, anesthesia has been shown to perturb normal brain function and physiology. Such effects limit our ability to detect subtle physiological alterations in disease models and treatment studies, thus hampering discovery and compromising generality of findings. Therefore, methods for awake animal MRI are needed to study the rodent brain in its natural physiological state, free of anesthetics. Current setups for awake animal MRI rely on restraining systems to avoid animal movement during scanning. To reduce restraint stress, animals are habituated to the scanner environment prior to MRI data collection. To date, however, most awake MRI studies employ male rodents only. This is a fundamental limitation as results obtained may be pertinent only to half of the population. We characterized training and habituation responses of male and female mice to provide improved, sex-dependent training procedures for awake mouse MRI. We recorded heart rate, monitored behavioral responses (body weight and fecal boli weight) and fecal corticosterone levels (FCM) as indicators of wellbeing and stress during a 14-day progressive habituation protocol. In addition, we also assessed discomfort levels and anxiety using the mouse grimace scale (MGS) and light/dark test (LDT), respectively. All scores were compared between both groups. We found that heart rate was significantly decreased after 10 and 11 days of training for both males and females, respectively. However, the specific time course for this decrease was significantly different between males and females, and females exhibited higher anxiety levels during habituation and 14 days after habituation than males. Lastly, we also found that mean FCM levels for both groups were decreased after 11 days of MRI habituation. The present work shows that mice can be successfully trained for extended MRI sessions which is necessary for many (particularly non-fMRI) studies. Importantly, we find that males and females differ in their response to awake MRI habituation, which should be considered in future awake MRI studies that aim to include male and female mice.

Time-Restricted Feeding in Mice Prevents the Disruption of the Peripheral Circadian Clocks and Its Metabolic Impact during Chronic Jetlag.

We used time-restricted feeding (TRF) to investigate whether microbial metabolites and the hunger hormone ghrelin can become the dominant entraining factor during chronic jetlag to prevent disruption of the master and peripheral clocks, in order to promote health. Therefore, hypothalamic clock gene and Agrp/Npy mRNA expression were measured in mice that were either chronically jetlagged and fed ad libitum, jetlagged and fed a TRF diet, or not jetlagged and fed a TRF diet. Fecal short-chain fatty acid (SCFA) concentrations, plasma ghrelin and corticosterone levels, and colonic clock gene mRNA expression were measured. Preventing the disruption of the food intake pattern during chronic jetlag using TRF restored the rhythmicity in hypothalamic clock gene mRNA expression of Reverbα but not of Arntl. TRF countered the changes in plasma ghrelin levels and in hypothalamic Npy mRNA expression induced by chronic jetlag, thereby reestablishing the food intake pattern. Increase in body mass induced by chronic jetlag was prevented. Alterations in diurnal fluctuations in fecal SCFAs during chronic jetlag were prevented thereby re-entraining the rhythmic expression of peripheral clock genes. In conclusion, TRF during chronodisruption re-entrains the rhythms in clock gene expression and signals from the gut that regulate food intake to normalize body homeostasis.

Fecal glucocorticoid metabolites reflect hypothalamic-pituitary-adrenal axis activity in muskoxen (Ovibos moschatus).

Muskoxen (Ovibos moschatus), a taxonomically unique Arctic species, are increasingly exposed to climate and other anthropogenic changes. It is critical to develop and validate reliable tools to monitor their physiological stress response in order to assess the impacts of these changes. Here, we measured fecal glucocorticoid metabolite (FGM) levels in response to the administration of adrenocorticotropic hormone (ACTH) in the winter (1 IU/kg) and summer (2 IU/kg) using two enzyme immunoassays, one targeting primarily cortisol and the other targeting primarily corticosterone. Fecal cortisol levels varied substantially within and among individuals, and none of the animals in either challenge showed an increase in fecal cortisol following the injection of ACTH. By contrast, two of six (winter) and two of five (summer) muskoxen showed a clear response in fecal corticosterone levels (i.e., maximal percentage increase as compared to time 0 levels > 100%). Increases in fecal corticosterone post-ACTH injection occurred earlier and were of shorter duration in the summer than in the winter and fecal corticosterone levels were, in general, lower during the summer. These seasonal differences in FGM responses may be related to the use of different individuals (i.e., influence of sex, age, social status, etc.) and to seasonal variations in the metabolism and excretion of glucocorticoids, intestinal transit time, voluntary food intake, and fecal output and moisture content. Results from this study support using FGMs as a biomarker of hypothalamic–pituitary–adrenal axis activity in muskoxen, advance our understanding of the physiological adaptations of mammals living in highly seasonal and extreme environments such as the Arctic, and emphasize the importance of considering seasonality in other species when interpreting FGM levels.

Increasing γ-Aminobutyric Acid Content in Vegetable Soybeans via High-Pressure Processing and Efficacy of Their Antidepressant-Like Activity in Mice.

This study applied high-pressure processing (HPP) technology to enrich the gamma aminobutyric acid (GABA) content in vegetable soybeans and evaluated its antidepressant efficacy on mice, with depression induced by the unpredictable chronic mild stress (UCMS) model. The optimal conditions for HPP, storage time, and storage temperature, as well as antidepressant-like effects of vegetable soybeans, were evaluated and discussed. HPP could effectively and significantly increase GABA content in soybean, with optimum conditions at 200 MPa. The GABA content in the whole vegetable soybean was 436.05 mg/100 g. In mice animal tests, the tail suspension test (TST) showed that the immobility time of the GABA group was significantly shorter than that of the control group. The total travel distance in the open field test (OFT) showed that depressed mice fed with the GABA feed exhibited exploratory behavior. The GABA group showed a significantly higher degree of sucrose preference than the control group. Both results indicate that the GABA feed could effectively alleviate depressive symptomatology. Regarding biochemical parameters, the fecal and serum corticosterone (CORT) levels in the control group increased to 104.86 pg/mg after the onset of depression. In contrast, the fecal CORT level in the GABA group was significantly reduced to 23.98 pg/mg and was comparable to that in the control group (33.38 pg/mg). Reduced serum CORT level in the GABA group suggests an improvement in depressive symptomatology. The serotonin concentration was maintained in the GABA group after the induction of depression, suggesting its preventive activity. The HPP GABA-enriched soybeans exerted modulatory effects on the behaviors of depressed mice and displayed a potential for commercialization.

A Nonsurgical Embryo Transfer Technique for Fresh and Cultured Blastocysts in Rats.

The use of a nonsurgical embryo transfer technique in rodents eliminates the potential pain, distress, and health complications that may result from a surgical procedure and as such, represents a refinement in rodent assisted reproductive techniques. A nonsurgical technique has not been previously developed for use with rat embryos. Here we describe an efficient method to deliver either fresh or cultured blastocyst stage embryos to the uterine horn of pseudopregnant female rats using a rat nonsurgical embryo transfer (rNSET) device. The rNSET device is composed of a Teflon catheter and a hub that attaches to a 2 μL pipette. Oxytocin is used to dilate the cervix before the delivery of blastocysts, allowing passage of the rNSET catheter directly into the uterine horn for embryo delivery. The efficiency of recovery of pups after nonsurgical embryo transfer is similar to the efficiency after surgical embryo transfer. Furthermore, the technique is not stressful to the subjects, as demonstrated by the absence of a decrease in weight or increase in fecal corticosterone level in recipients of embryos delivered nonsurgically, without the use of anesthesia or analgesia.

Gonadal steroid hormone secretion during the juvenile period depends on host-specific microbiota and contributes to the development of odor preference.

The host microbial community is thought to have an important role in the host endocrine system and behavioral phenotype. We investigated chronological changes of levels of gonadal hormones and corticosterone in the feces of 4- to 8-week-old female germ-free (GF) mice, and conducted odor preference test at 8weeks of age. We further evaluated the developmental impact of the microbial community by analyzing 4-week-old GF mice orally administered the fecal microbiota of specific pathogen-free (SPF) mice or guinea pigs (GF-SPF mice or GF-Guinea pig mice). The fecal estradiol, progesterone, and corticosterone levels of GF mice were lower than those of SPF mice. Furthermore, the increased levels in GF mice were suggested to be caused by colonization of microbiota of SPF mice or guinea pigs. However, the degree of recovery of progesterone and corticosterone by microbiota of guinea pigs was lower than that by SPF mice. In odor preference tests, interestingly, female GF mice preferred female odors to male odors, although this preference was not seen in other mice. These findings suggested that the microbial community plays an important role in the development of the host endocrine system for gonadal hormones and corticosterone, and odor preference in mice.

Effect of cage and pen housing on the live performance, carcase, and meat quality traits of growing rabbits

The aim of the experiment was to study the effect of housing growing rabbits in enriched cages with small groups (eight rabbits/cage, C; n = 96; stocking density: 15 rabbits/m2) or in enriched pens with large groups (65 rabbits/pen, P; n = 130; stocking density: 15 rabbits/m2) on their growth performance and on slaughter and meat quality traits. The C rabbits showed higher final body weight (2540 vs. 2443 g, p < .01), better feed conversion ratio (5–11 weeks: 3.39 vs. 3.61, p < .05), lower mortality rate (5.2 vs. 31.5%, p < .001), and lower fecal corticosterone level (26.3 vs. 29.4 nmol/g, p < .05) compared to P rabbits. The increased possibility of physical activity of P compared to C rabbits resulted in more developed hind part of the reference carcase, thicker hind leg bones (34.8 vs. 33.4 g, p < .05), lower perirenal fat (15.1 vs. 20.8 g, p < .001) and hind leg meat lipid content (2.00 vs. 2.42%, p < .05), as well as higher haem iron content of the hind leg meat (5.29 vs. 4.22 mg/kg, p < .01). However, pen housing was detrimental for the dressing out percentage and for the hind leg meat to bones ratio. Physical meat quality traits were not affected by the housing system.HighlightsHousing of growing rabbits in large cages and large pens was compared.Caged rabbits had better productive performance, lower mortality and stress.Penned rabbits resulted in lower dressing out percentage, carcase adiposity and meat lipids content.Most of the meat quality traits were independent of the housing system.

The effects of mining machinery noise of different amplitudes on the behaviour, faecal corticosterone and tissue morphology of wild mice (Mus musculus)

Mining noise has been identified as a source of stress for wildlife but the effects on the behaviour and physiology of individuals are largely unknown. We evaluated the effects of exposing wild mice to mining machinery noise for 3 weeks at two amplitude ranges: high (HA; 70–75 dB (A)) and low (LA; 60–65 dB (A)) on their behaviour, organ properties and faecal corticosterone levels, when compared with a control treatment (no extra auditory stimuli, below 55 dB (A)). Both noise treatments increased circling to the left, compared to the control (P = 0.001) which corresponds to right hemispheric processing of the stress response; however only the high amplitude noise increased circling to the right (left hemisphere activation; P < 0.0001), which may inhibit stress arousal by right hemisphere. Total circling behaviour (to the left and right) was just increased in mice exposed to high amplitude noise, compared with those in the control and low amplitude noise (P < 0.0001), but in the low amplitude noise faecal corticosterone was increased (P = 0.003). We hypothesize that dopamine-related stereotypies during high amplitude mining noise were a coping mechanism that prevented a physiological response. Noise-exposed males tended to have smaller spleens (P = 0.003) and females in the HA treatment tended to have a smaller adrenal cortex/medulla ratio (P = 0.007). Mining machinery noise produced amplitude – dependent stress responses in wild mice that probably required the generation of coping mechanism.

A happier rat pack: The impacts of tickling pet store rats on human-animal interactions and rat welfare

Rats find initial interactions with humans frightening, which can lead to negative affect, and poor welfare. A handling technique called “tickling”, which mimics rat rough-and-tumble play, can be used to reduce these negative effects. When tickled, rats produce 50 kilohertz (kHz) ultrasonic vocalizations (USV) indicative of positive affect. During tickling, some rats consistently vocalize more (high-callers) and react more positively to novelty and stress than rats that utter fewer vocalizations (low-callers). Rats in pet stores can experience high levels of environmental novelty, as well as infrequent and inconsistent human interaction, which may reinforce a fearful human-rat relationship. We hypothesized that tickling pet store rats improves human-rat interactions and animal welfare, particularly for tickled high-callers, as compared to non-tickled controls or tickled low-callers.Across 2 replicates, 36 female rats were sampled with 6 minimally handled controls and 12 tickled rats per replicate. Tickled rats were split into two groups, high-callers (most USVs) and low-callers (least USVs), based on tickling for 3 days (5 min/rat/day). Handling treatments were applied by store employees for 4 additional days. During these 4 days, feces were collected to assess fecal corticosterone levels and continuous video recordings were made to quantify play behavior, activity level, and location. Finally, rats were assessed with an unfamiliar human approach (60 s), manual restraint (30 s) and second human approach test (60 s).Results showed in an unfamiliar human approach and restraint test, tickled rats required fewer restraint attempts and shorter time to restrain than controls (p < 0.05). Tickled low-callers displayed more signs of fear and anxiety, such as fewer rears and lower activity level than tickled high-callers during both approach tests (p < 0.05). Tickled rats had higher fecal corticosterone levels than control rats (p = 0.003). Analysis of in-cage behaviors and location showed that tickled rats spent more time outside their hut than control rats (p = 0.004).In conclusion, short-term tickling of pet store rats improves ease of restraint with an unfamiliar handler. In comparison to low-calling rats, high-calling rats show less fear toward unfamiliar humans. Tickled rats had higher arousal levels based on fecal corticosterone, which may relate to their anticipation of interaction with humans. Overall, our results suggest that tickling pet store rats may improve some human-rat interactions, especially for tickled high-calling rats.

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

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

The effects of mining machinery noise of different frequencies on the behaviour, faecal corticosterone and tissue morphology of wild mice (Mus musculus)

Mining noise has a wide variety of frequency spectra and is a potential source of stress for wildlife. We evaluated the effects of mining machinery noise on behaviour and associated physiological parameters at two isoenergetic frequency ranges: high (>2kHz) and low (≤2kHz), the latter being less audible to mice, our model species. Effects of these two frequency spectra on behaviour, organ morphology and faecal corticosterone of wild mice were compared with a control treatment with no extra auditory stimuli. The mice exposed to high frequency noise spent less time in their nest than those exposed to low frequency noise or those in the control treatment, and they spent more time circling, especially anticlockwise, which in conjunction with elevated faecal corticosterone levels may reflect a greater right brain hemisphere stress-related response, particularly in females. Low frequency mining noise reduced grooming and circling, suggesting decreased physiological arousal due to mild stress. Low frequencies were also associated with increased faecal corticosterone in males compared to controls, which may be related to gender-based differences of the ear canal that affect frequency sensitivity. In conclusion, high frequency and low frequency mining machinery noise produced stress-related responses that may be important for the animals’ welfare and survival.

Correlating bacterial shedding with fecal corticosterone levels and serological responses from layer hens experimentally infected with Salmonella Typhimurium

Salmonella Enteriditis and Salmonella Typhimurium are commonly isolated during egg-related outbreaks of salmonellosis and represent a significant international public health issue. In Australia, Salmonella Typhimurium is the most common serovar identified in egg product related foodborne outbreaks. While a number of studies have investigated Salmonella shedding and host responses to infection, they have been conducted over a short time period. The present study sought to characterise bacterial shedding and host responses to infection in hens infected with only Salmonella Typhimurium or co-infected with both Salmonella Typhimurium and Salmonella Mbandaka over a 16 week period. Salmonella shedding was quantified using the most probable number and qPCR methods and was highly variable over the course of the experiment. On day 1, fecal corticosterone metabolites in birds infected with Salmonella Typhimurium (674.2 ± 109.3 pg/mg) were significantly higher than control (238.0 ± 12.62 pg/mg) or co-infected (175.4 ± 8.58 pg/mg) birds. The onset of lay occurred between weeks 6–8 post-infection (pi) and Fecal corticosterone metabolite (FCM) concentrations increased in both control and co-infected birds. Antibody responses to infection were monitored in both serum and yolk samples. Salmonella Typhimurium specific antibody was lower in co-infected animals than monoinfected animals. Bacterial loads in internal organs were characterised to determine persistence. Spleen, liver and caecal tonsils were positive for bacteria in both groups, indicating that Salmonella was not cleared from the birds and internal organ colonization could serve as a reservoir for continued bacterial shedding.

Effects of Sheltering on Behavior and Fecal Corticosterone Level of Elderly Dogs.

In Japan, the human population is aging rapidly, and the abandonment of dogs by the elderly people who have died or been hospitalized becomes a problem. It is hypothesized that elderly dogs have difficulty adapting to the novel circumstances when brought to an animal shelter. Therefore, the objective of this study was to assess stress levels and demonstrate stress responses of elderly dogs just after admission to an animal shelter. As stress indicators, fecal corticosterone levels and changes in the ethogram of the dogs were investigated during the first week of admittance. Fecal corticosterone levels (mean ± SE) stayed high during the first week of residence, although they fell gently from the day after admittance (16650.1 ± 3769.7 ng/g) to the seventh day (12178.4 ± 2524.4 ng/g) (P < 0.001). The proportions of behavioral expressions changed as the days passed (P < 0.001). In particular, stereotypies decreased from 35.7% on the first day to 2.6% on the sixth day, and time spent sleeping increased from 0.0 to 42.7%. These results indicate that elderly dogs admitted to an animal shelter seem to behaviorally adapt themselves to their novel circumstances but might be stressed even on the seventh day of residence.