Basal and stress response cortisol levels and stress avoidance learning in sheep (Ovis ovis)

Effect of a targeted pain management protocol for the treatment of dermatitis interdigitalis contagiosa in Merino meat sheep in a tilt squeeze chute

Introduction

The effect of a targeted pain management protocol consisting of sedation and local anesthesia on the stress response to treatment of dermatitis interdigitalis contagiosa (DINCO) was assessed in sheep placed in dorsal recumbency.

Methods

Blood cortisol concentrations were measured once a day (Day -3 to 2) and additionally on day 0, six times during the claw treatment (stress model). Twelve healthy sheep (control group; HEALTHY) and 36 sheep with DINCO, randomly allocated to one of three treatment groups, underwent the stress model with or without pain control: the XYLA-IVRA sheep were sedated with 2% xylazine hydrochloride (XYLA) and received retrograde intravenous regional anesthesia (IVRA); the IVRA sheep underwent IVRA and received a placebo instead of sedation; the PLACEBO sheep received placebos for sedation and IVRA. The HEALTHY sheep underwent sham claw treatment and received placebos.

Results and discussion

The cortisol concentrations were higher in sheep restrained in dorsal recumbency compared with the cortisol concentrations measured four hours later in standing sheep (HEALTHY 37.2 ± 3.3 ng/ml vs. 18.5 ± 3.3 ng/ml; DISEASED 34.0 ± 1.9 ng/ml vs. 17.6 ± 1.9 ng/ml; p < 0.001). The stress response of XYLA-IVRA (area under the curve; AUC = 34.9 ± 2.6 ng/ml) was reduced compared with the stress response of PLACEBO (AUC = 48.0 ± 2.6 ng/ml, p < 0.01) and HEALTHY sheep (AUC = 46.6 ± 2.5 ng/ml; p = 0.01). While cortisol concentration of XYLA-IVRA and HEALTHY sheep did not increase one day after the stress model (Day 1) compared with the day of the stress model (Day 0), both PLACEBO (47.4 ± 3.3 vs. 35.6 ± 3.1 ng/ml, p = 0.02) and IVRA sheep (39.1 ± 2.8 vs. 28.6 ± 3.1 ng/ml, p = 0.01) had higher cortisol concentrations. The results confirm that fixation in dorsal recumbency in a tilt squeeze chute was a major stressor in sheep. The differences in the cortisol concentration of the PLACEBO sheep versus the XYLA-IVRA sheep during and after the stress model illustrate the effect and necessity of pain management protocols in practice.

Assessment of Meat-Type Sheep Welfare Using Animal-Based Measures

Simple Summary

There was every indication that animal welfare will continue to be a major issue affecting livestock farming in the future. The main welfare issues affecting sheep were feeding strategies, health, and diseases. The health problems of sheep are avoidable with good grazing, breeding, and stockmanship. However, sheep must be given adequate supervision to ensure that any welfare issues are quickly noticed and addressed. Assessing animal welfare can be used as management tools by farmers to identify welfare issues and recognize poor welfare.

Abstract

This study aimed to assess the welfare of Tunisian sheep in extensive sheep production systems using animal-based measures of ewe welfare. This study encompasses the first national survey of sheep welfare in which animal-based outcomes were tested. Animal-based welfare measures were derived from previous welfare protocols. Fifty-two Tunisian farms were studied and a number from 20 to 100 animals by flock were examinated. The whole flock was also observed to detect clinical diseases, lameness, and coughing. The human-animal relationship was selected as welfare indicators. It was evaluated through the avoidance distance test. The average avoidance distance was 10.47 ± 1.23 and 8.12 ± 0.97 m for a novel person and farmer, respectively. The global mean of body condition score (BCS) was 2.4 with 47% of ewes having a BCS of two, which may be associated with an increased risk of nutritional stress, disease, and low productivity. Ten farms had more than 7% of lambs with a low body condition score, which may be an indication of a welfare problem. The results obtained in the present study suggest that the used animal-based measures were the most reliable indicators that can be included in welfare protocols for extensive sheep production systems.

Technical note: comparison of salivary and serum cortisol concentrations after adrenocorticotropic hormone challenge in ewes

An ACTH challenge was conducted to determine if salivary cortisol concentration reflects serum cortisol concentration in ewes. Twelve yearling ewes (64.0 +/- 1.2 kg) were administered ACTH (100 IU, intravenously) or saline. Serum and salivary samples were collected at 30-min intervals for 2 h before ACTH administration, at 15-min intervals for 2 h after treatment, and at 30-min intervals for an additional 3 h, and cortisol concentration was determined by RIA. Although ewes responded to ACTH and saline, cortisol concentration was greater (P < 0.001) in ACTH-treated ewes from 15 to 120 min and tended to be greater (P = 0.054) at 150 min after challenge in serum. In saliva, cortisol concentration was greater (P < 0.001) in ACTH-treated ewes from 30 to 120 min and tended to be greater (P = 0.092) at 15 min after challenge. No difference was observed between ACTH-treated ewes and controls for time to peak serum cortisol concentration (P = 0.126) and time to peak salivary cortisol concentration (P = 0.109), or between saliva and serum for time to peak cortisol concentration (P = 0.220) and return to baseline cortisol concentration (P = 0.341). The serum (P = 0.009) and salivary (P = 0.050) cortisol areas under the curve between 0 and 150 min were greater for ACTH-treated ewes than controls, and serum (P = 0.002) and salivary (P < 0.001) cortisol return to baseline concentration was longer for ACTH-treated ewes. The correlation coefficient between serum and salivary cortisol concentrations was 0.88 (P < 0.001). These data indicate that salivary cortisol concentration is closely related to serum cortisol concentration and that the former may represent a suitable noninvasive alternative to blood collection for measurement of cortisol in sheep.

Evaluating capture stress and its effects on reproductive success in Svalbard reindeer

Although many ecological studies of wild animal populations rely on capturing individuals at least once, few have investigated either the immediate stress responses of capture, restraint, and handling, or the longer term consequences on reproductive success. In this paper, we assume that the degree of stress increase with the time taken to capture and process an animal prior to release. The influence of time since onset of capture on body temperature and blood chemistry indicators of stress was investigated in 137 adult female Svalbard reindeer ( Rangifer tarandus platyrhynchus Vrolik, 1829) and 63 calves of both sexes captured by net in late-winter 2004 and 2005. In addition, we looked for evidence of negative effects of capture stress on reproductive success in marked animals over the period from 1995 to 2006. Body temperature increased with both chase time and the time the animals were restrained. In the latter case, body temperature increased twice as fast in nonpregnant animals (0.13 °C/min) compared with pregnant animals. Cortisol, glutamate dehydrogenase, and γ-glutamyltransferase all increased with time from onset of capture. However, the relationship for glucose with time since onset of capture increased initially before declining again. We found no evidence of a lower calving success in animals captured the previous winter when compared with animals that had not been captured the previous winter. Likewise, there was no relationship between the strength of the acute stress response (measured as cortisol concentrations) and the probability of pregnant females having a calf at foot the subsequent summer.

Stress induces CRF release in the paraventricular nucleus, and both CRF and GABA release in the amygdala

In the hypothalamus, corticotropin-releasing factor (CRF) initiates the hypothalamic-pituitary-adrenal (HPA) axis response to stress, resulting in the release of glucocorticoids, including cortisol. Extrahypothalamic CRF, particularly in the limbic system, also appears to play a role in the stress response. To further define brain CRF response to stress, immunosensor-based microdialysis probes were used to measure the extracellular levels of CRF in the paraventricular nucleus of the hypothalamus (PVN) and in the amygdala of sheep during a predator (dog) exposure stress. In addition, gamma amino butyric acid (GABA) was measured in the amygdala and cortisol was measured in venous blood. Exposure to the predator stress increased CRF in the PVN and both CRF and GABA in the amygdala. These were followed in time by a rise in venous cortisol. Application of a CRF antagonist to the amygdala, immediately prior to stress, had a small effect on the subsequent observed stress responses. This treatment, however, significantly reduced the responses to a repeat stress administered 2 days later, compared to nontreated animals. Application of a GABA antagonist to the amygdala prior to stress had no effect on the subsequent observed stress response but increased the response to the stress repeated 2 days later. Perfusion with 4-aminopyridine, a neuronal depolarising agent, into the PVN induced a release of CRF accompanied shortly thereafter by a small increase in CRF in the amygdala, and 5-10 min later by an increase in venous cortisol. Perfusion into the amygdala increased the levels of both CRF and GABA but had no effect on either PVN CRF or venous cortisol. These data support roles for both the PVN and amygdala in stress responsiveness. It suggests further that actions at the amygdala can strongly influence subsequent responsiveness to a further stress, mediated in part by both CRF and GABA actions.

Chronic stress in sheep: assessment tools and their use in different management conditions

Chronic stress occurs when animals are unable to deal with a persistent stressor with species-typical responses, or when several stressors are present concurrently. Chronic stress is most frequently considered in intensive systems, but it may also be a welfare concern for extensively managed species, such as the sheep. Here we review behavioural and physiological responses of sheep to experimentally induced chronic stressors to determine relevant indicators of chronic stress. Neuroendocrine responses to chronic stress are difficult to interpret because initial responses are followed by an apparent normalisation. Thus, cortisol or catecholamines may be at or below pre-stress levels during chronic stress, but this varies with different stressors. Chronic stress can also affect reproductive function, impair body and wool growth and meat quality, reduce immune function, and is associated with greater parasite burdens in sheep. Chronic stress induces alterations in behaviour patterns, particularly activity and feeding, and circadian rhythms of behaviour. Stereotypic behaviours, however, are infrequent in sheep and may occur only in experimental conditions of social isolation. Behavioural and physiological data suggest that rough handling and sheepdogs may be sources of chronic stress for sheep. Social subordination and weaning also act as chronic stressors, leading to higher parasitism in these animals and a greater response to additional stressors. Lameness and parasitism are associated with physiological and behavioural responses indicating that these are severe forms of chronic stress in sheep. It is unclear whether environmental stressors, such as weather and food availability, induce chronic stress in sheep. Under-nutrition may, however, be a welfare concern through its impact on lamb survival. The existence of many sources of chronic stress in the management of sheep suggests that the welfare of this species requires more attention than it has currently received.

Quantitative analysis of human salivary glucose by gas chromatography–mass spectrometry

A reference analytic methodology was developed for the determination of human salivary glucose concentration. The technique involves the glucose derivatization with acetic anhydride and subsequent analysis of glucose penta-acetylated by gas chromatography combined with mass spectrometry. Glucose concentration in the biological fluid depends on the physiological status of the donor.

Glucocorticoid feedback increases the sensitivity of the limbic system to stress

In the hypothalamus, corticotropin-releasing hormone (CRH) has a well-described role initiating the hypothalamic-pituitary-adrenal (HPA) axis response to stress. Cortisol, released from the adrenal gland, exerts negative feedback on this axis. The role of extrahypothalamic CRH in stress responses is less well known. The purpose of this study was to measure the response of CRH in the amygdala to acute and repeated stress and to examine if cortisol had any effect on this response. Immunosensor-based microdialysis probes were used to measure CRH and cortisol in the amygdala and cortisol systemically in sheep exposed to a predator stress (a dog). Upon presentation of a dog, CRH increased in the amygdala of the sheep and then fell off. Cortisol levels rose both systemically and in the amygdala, and as they peaked, a second CRH response was observed. Repeated stress changed this response, with the magnitude of the first CRH peak decreasing while the second peak increased. Repeated stress also produced an exaggeration in both of the CRH peaks to presentation of a subsequent novel stress (a forelimb electric shock). Animals that had an escape route from the repeated dog stress did not show this exaggeration when faced subsequently with the novel stress. Administration of mifepristone, a glucocorticoid receptor antagonist, prior to the delivery of the repeat stress prevented subsequent changes in the CRH response. The data suggest that the amygdala shows a CRH response to presentation of a stressor acutely and repeatedly and that repeated stress can alter subsequent amygdala responsiveness to the same or a different stressor. This alteration appears dependent on circulatory glucocorticoids.

Rapid noninvasive measurement of hormones in transdermal exudate and saliva

Experiments were conducted in both sheep and humans to evaluate techniques for rapid sampling and measurement of testosterone, insulin, 17-beta estradiol, cortisol and glucose collected in saliva or transdermal exudate. Ultrasound and an electric current facilitated the latter collection. All but insulin were successfully measured in saliva, under resting conditions, and the measured hormones correlated best with blood levels 20-40 min prior to the saliva collection. With imposition of, and recovery from, an exercise stress, this correlation was weakened irrespective of considering the time lag between blood measures during this period and subsequent changes in saliva values. Provided an initial transdermal flux was established, all the hormones and glucose were successfully measured in the transdermal exudate at levels correlating with blood measures at the time of collection, and this held across stressor application and recovery. The transdermal exudate sampling and measurement apparatus is relatively portable, enabling noninvasive collection and analyte measurement, rapidly, at the site where the experiment is being conducted with minimal interference to subjects. This potentially offers a tool of considerable value to endocrine studies.

Effects of experimental infection withLeptospira interrogansserovarbalcanicaon the health of brushtail possums (Trichosurus vulpecula)

Data on changes in the condition and feeding behaviour of captive brushtail possums (Trichosurus vulpecula) following an experimental infection with Leptospira interrogans serovar balcanica are presented. The daily food intake of nine experimentally infected possums was recorded for 47 days before and 24 days after balcanica inoculation (0.5 ml intraperitoneally containing about 10(8) organisms). Body weight was recorded seven times between 42 days before and 96 days after inoculation. The mean daily food intake of infected possums decreased significantly throughout the 24-day recording period after infection with balcanica. The mean body weight of infected possums had decreased significantly by day 26 after inoculation but had fully recovered by day 96 after inoculation. Uninfected and control possums showed no significant changes in mean daily food intake or mean body weight over the experimental period. These data suggest that the health of possums is temporarily affected by infection with balcanica, but that overt disease caused by balcanica is unlikely. These findings support previous research suggesting that balcanica has only subclinical effects on possums.