Responses of the porcine pituitary-adrenal axis to chronic intermittent stressor

Methods of Assessment of the Welfare of Shelter Cats: A Review

At any moment, there are millions of cats housed in foster care facilities for abandoned and stray animals for various reasons worldwide. Care, management and regulation among these facilities differ. Moreover, shelters can never substitute the full comfort of a good home for the animal, and the welfare of cats in shelters is a subject of discussion in many respects. Cats are animals sensitive to changes; for most of them, placement in a shelter is a stressful experience because of changes in routine, environment and the presence of other animals. Stress is reflected in changes in behaviour, causes fluctuations in physiological values and disrupts the immune system, which is a predisposition to the development or reactivation of disease. Evaluation of the presence and intensity of negative impacts is possible through the use of evaluation tools based on indicators that help set the environment and management of keeping so as to disrupt the quality of life as little as possible. Although a comprehensive and valid welfare tool that would evaluate animal-based and at the same time resource-based (or management-based) indicators of cats in shelters is not currently available, it is possible to use partial evaluation of individual welfare indicators to assess welfare. This review aims to provide the readers with an insight into current options of assessment of the welfare of cats in shelters with an emphasis on behavioural, physiological and health indicators with an application in both practical and scientific contexts.

Responsiveness of swine divergently selected for feed efficiency to exogenous adrenocorticotropic hormone and glucose challenges

Increasing the feed efficiency of lean tissue gains is an important goal for improving sustainable pork production and profitability for swine producers. To study feed efficiency, genetic selection based on residual feed intake (RFI) was used to create two divergent lines. Low-RFI pigs consume less feed for equal weight gain compared with their less-efficient, high-RFI counterparts. As cortisol and insulin are important energy control and growth regulators, our objective was to evaluate the role of the adrenocorticotropic hormone (ACTH)-cortisol and the glucose-insulin axes in pigs divergently selected for RFI. Adrenocorticotropic hormone (0.2 IU/kg BW)-stimulated cortisol and non-esterified fatty acids (NEFA) concentrations and intravenous glucose tolerance test (IVGTT; 0.25 g/kg BW)-stimulated glucose, insulin, and NEFA concentrations were assessed in six low-RFI and six high-RFI gilts (68 ± 5.2 kg). Before the ACTH challenge, low-RFI gilts tended to have less baseline plasma cortisol (P = 0.08) but no difference in NEFA concentrations (P = 0.63) compared with high-RFI gilts. After the ACTH challenge, low-RFI gilts had less cortisol (P = 0.04) and NEFA concentrations (P = 0.05) compared with high-RFI gilts. Glucose, insulin, and NEFA concentrations did not differ between genetic lines before the IVGTT. After glucose infusion, low-RFI gilts had greater insulin concentrations (P = 0.003) but did not differ in glucose or NEFA concentrations compared with high-RFI gilts. These results indicate that genetic selection for reduced RFI (improved feed efficiency) resulted in less stress responsiveness and an increase in insulin after glucose infusion. These data have implications for identifying and selecting more feed efficient pigs and for understanding the physiological mechanisms underlying feed efficiency.

Effects of age and maternal reactivity on the stress response of the pituitary-adrenocortical axis and the sympathetic nervous system in neonatal pigs

The study was conducted to investigate the adreno cortical capacity after injection of ACTH and the sensitivity of the pituitary and the adrenal to immobilization in neonatal pigs at different ages. Furthermore, the endocrine reactivity of the offspring was compared with the stress reactivity of their mothers. Four piglets were selected from each of six different litters and subjected to an immobilization test and an adrenal function test using synthetic ACTH1-24 at the ages of 7, 21 and 35 days; the six sows were also subjected to restraint and an ACTH stimulation test. Plasma β-endorphin, norepinephrine and epinephrine concentrations were measured in blood samples taken 2 min after restraint and cortisol concentrations were measured 60 min after ACTH administration. A highly sensitive adrenal response was demonstrated in both sows and piglets and adrenal reactivity showed also a considerable consistency over time within sows. In neonatal pigs, the cortisol response to ACTH was greatest on day 7 and decreased up to day 35. Plasma epinephrine and norepinephrine levels after the 2-min immobilization were also higher at day 7 compared with the other ages (P < 0·01). Piglets from sows, classified as high reacting according to their cortisol or epinephrine response, also showed significantly higher cortisol levels after ACTH challenge at all ages and significantly higher epinephrine levels after restraint at day 7 than piglets from low reacting sows. The results show an age-related change of pituitary-adrenocortical and sympatho-adrenomedullary responses in neonatal pigs and an absence of a stress hyporesponsive period at all ages studied. The results also indicate different levels of excitability in the offspring depending on the maternal stress reactivity.

Effects of open field testing and associated handling v. handling alone on the adrenocortical reactivity of piglets around weaning

Effects of open field testing and associated handling (including blood sampling) v. handling (with blood sampling) alone on adrenocortical reactivity were investigated in piglets around weaning. After weaning at day 28, piglets were mixed to form eight replicates with three litter each and kept on slatted floors. Treatments were open field/novel object testing and associated handling (OFT + H) v. handling alone (H) (no. = 40). Testing took place on the following days (weaning day 0): -4, 0, 1, 4 and 8 (no. = 16). The open field/novel object test lasted 10 min and blood was sampled by venipuncture before and after the test and/or handling procedures. In the first blood sample, plasma concentration of cortisol did not differ between OFT + H and H piglets. In the second blood sample, however, OFT + H piglets had a higher concentration of cortisol and a larger increase in cortisol than H piglets (P < 0·01). In the first blood sample the concentration of cortisol was affected by day (P < 0·05), with concentration on day -4 being lower than those on day 0, 1, and 4 and the concentration on day 8 was lower than the concentration on day 0 as well. However, no differences were found between days for the second blood sample nor the adrenocortical reactivity. In conclusion, the increase in pre-treatment cortisol in the first 4 days after weaning as well as the lack of changes in the adrenocortical reactivity after weaning suggest that the temporal development of HPA activity and reactivity in piglets after weaning are comparable with other, more standardized long-term stressors. Exposure to an open field/novel object test and associated handling results in higher adrenocortical reactivity than handling alone but the latter (including blood sampling) in itself accounts for proportionately 0·74 of the cortisol response.

The association of Hsp90 expression induced by aspirin with anti-stress damage in chicken myocardial cells

The protective effect of aspirin during exposure to heat stress in broiler chickens was investigated. We assayed pathological damage, expression and distribution of Hsp90 protein and hsp90 mRNA expression in chicken heart tissues after oral administration of aspirin following exposure to high temperature for varying times. Heat stress induced increases in plasma aspartate aminotransferase, creatine kinase and lactate dehydrogenase activities while causing severe heart damage, which was characterized by granular and vacuolar degeneration, nuclear shrinkage and even myocardium fragmentation in cardiac muscle fibers. After aspirin administration, myocardial cells showed fewer pathological lesions than broilers treated with heat alone. A high positive Hsp90 signal was always detected in the nuclei of myocardial cells from broilers treated with aspirin, while in myocardial cells treated with heat alone, Hsp90 in the nuclei decreased, as did that in the cytoplasm. Aspirin induced rapid and significant synthesis of Hsp90 before and at the initial phase of heat stress, and significant expression of hsp90 mRNA was stimulated throughout the experiment when compared with cells exposed to heat stress alone. Thus, specific pre-induction of Hsp90 in cardiovascular tissue was useful for resisting heat stress damage because it produced stable damage-related enzymes and fewer pathologic changes.

Expression and distribution of heat shock proteins in the heart of transported pigs

The expression and localization of four heat shock proteins (Hsp70, Hsp86, Hsp90, and Hsp27) were shown in the heart tissue of pigs transported for 6 h. Immunostaining detected the consistent presence of all Hsps in the pig myocardial cells under both transported and normal housing conditions. Immunohistochemical analysis revealed predominance of Hsp70 (significantly highest levels) and Hsp27 in the cytoplasm of myocardial cells. Hsp90 and Hsp86 were expressed both in the cytoplasm and in the nucleus, preferentially in the cytoplasm, of the myocardial cells. In view of their abundant and uniform distributions in the myocardial cells, the expression and distribution patterns of all detected Hsps within the myocardial cells, mostly limited to the cytoplasm, could be related to their chaperone function for cells with important special activities in this study. The identification of all four Hsps in the blood vessel endothelial cells possibly implies that endothelial cells react to ischemia and hypoxia by expressing Hsps. Immunoblot findings suggest that the level of all Hsps decreased in response to stress due to a 6 h journey. The decrease in Hsp levels in the myocardial cells may indicate that the transport stress may have overcharged the repair mechanisms of the cells. Whether this distinct depletion of Hsps contributes to an increased susceptibility to acute heart failure and the sudden death syndrome in transported pigs should be elucidated in future experiments.

The effect of active immunization against adrenocorticotropic hormone on cortisol, beta-endorphin, vocalization, and growth in pigs

Because the poor growth performance of intensively housed pigs is associated with increased circulating glucocorticoid concentrations, we investigated the effects of glucocorticoid suppression by inducing a humoral immune response to ACTH on physiological and production variables in growing pigs. Grower pigs (28.6 +/- 0.9 kg) were immunized with amino acids 1 through 24 of ACTH conjugated to ovalbumin and suspended in diethylaminoethyl (DEAE) dextran-adjuvant or adjuvant alone (control) on d 1, 28, and 56. The ACTH-specific antibody titers generated suppressed increases in cortisol concentrations on d 63 in response to an acute stressor (P = 0.002; control = 71 +/- 8.2 ng/mL; ACTH-immune = 43 +/- 4.9 ng/mL) without altering basal concentrations. Plasma beta-endorphin concentrations were also increased (P < 0.001) on d 63 (control = 18 +/- 2.1 ng/mL; ACTH-immune = 63 +/- 7.3 ng/mL), presumably because of a release from negative feedback on the expression of proopiomelanocortin in pituitary corticotropes. Immunization against ACTH did not alter ADG (P = 0.120; control = 1,077 +/- 25; ACTH-immune = 1,143 +/- 25 g) or ADFI (P = 0.64; control = 2,719 +/- 42; ACTH-immune = 2,749 +/- 42 g) and did not modify behavior (P = 0.681) assessed by measuring vocalization in response to acute restraint. In summary, suppression of stress-induced cortisol responses through ACTH immunization increased beta-endorphin concentrations, but it did not modify ADG, ADFI, or restraint vocalization score in growing pigs.

Effect of 12-hour road transportation on physiological, immunological and haematological parameters in bulls housed at different space allowances

The effects of transporting Holstein Friesian bulls (n=72; bodyweight 403+/-3.5 kg) for 12h by road were examined. Adrenal, haematological and immune responses, body temperature and performance were recorded. The animals had been previously housed for 96 days at three space allowances (1.2, 2.7 or 4.2m(2) per bull). The bulls were allocated to one of two treatments: T (transport for 12h; n=16 per space allowance) and C (control; n=8 per space allowance). Basal cortisol plasma concentrations and interferon (IFN)-gamma production from cultured lymphocytes did not show any statistically significant difference (P>0.05) following the housing period. Removing bulls from their home pens and walking them to the pre-loading crush facility, loading onto the transporter, and unloading following the 12h road journey, significantly (P<0.001) increased plasma cortisol concentration. The bulls housed at 4.2m(2) had greater (P<0.05) plasma cortisol concentrations than bulls housed at 1.2m(2) at loading, unloading, or on return to the crush holding facility; those housed at 1.2m(2) had greater (P<0.05) plasma cortisol concentrations than bulls housed at 2.7 and 4.2m(2) in their home pens after transport. There was an increased (P<0.05) plasma cortisol response in the T than in the C bulls following adrenocorticotrophic hormone administration. Transport significantly reduced (P<0.05) IFN-gamma production, lymphocyte % and body weight and significantly increased (P<0.05) neutrophils, eosinophils, packed cell volume, red blood cell numbers and haemoglobin. In conclusion, housing bulls for 96 days in a range of space allowances did not affect basal cortisol response or immune function parameters. Whereas transport increased plasma cortisol and reduced the immune response in the short-term, the changes were transient and within normal physiological ranges, suggesting that 12h road transport had no adverse effect on welfare status over the longer term. Furthermore, transport of bulls housed at increased space allowance (4.2m(2)/bull) resulted in a greater plasma cortisol response, albeit still within normal physiological range.

Programming the offspring of the pig by prenatal social stress: neuroendocrine activity and behaviour

This study provides evidence in the pig that stress experienced during gestation has long-lasting effects on offspring daughters, including their maternal behaviour. Thirty-six primiparous sows were divided into control and two groups that were stressed (by social mixing) during either the second (Mix 2) or third (Mix 3) trimester of pregnancy. We found detrimental effects of mixing on the mothers' growth, body lesions, and cortisol secretion, but did not observe any significant effects on reproductive parameters including birth weight. At 60 days of age, 48 daughters were randomly selected from the three treatments: half were challenged using a restraint and isolation test. Then, all were culled and brain tissue was collected. In situ hybridisation measurements showed increased expression of CRH mRNA in the PVN in unrestrained Mix 2 and in the amygdala of Mix 2 and Mix 3 daughters. At 67 days, 24 further daughters were mixed to measure their responses to this social stress. All showed increased salivary cortisol secretion, but Mix 2 and Mix 3 daughters showed a greater and longer response than controls. Finally, all 24 were inseminated and at parturition maternal behaviour was measured. Mix 2 and Mix 3 daughters were more restless and more responsive to piglets that approached the head of the sow, traits which previously have been shown to be a component of abnormal maternal behaviour. Indeed, Mix 2 and Mix 3 daughters also tended to bite at their piglets more than control daughters.

Neuronal number, volume, and apoptosis of the left dentate gyrus of chronically stressed pigs correlate negatively with basal saliva cortisol levels

Although the consequences of stress and hypercortisolemia for the rodent hippocampal dentate gyrus (DG) are well known, little is known about other species. For pigs, tethered housing represents a well-established chronic stressor that shares many similarities with restraint paradigms, as evidenced by profound changes in behavior and autonomic and endocrine dysfunction, including flattened cortisol rhythms and hypercortisolemia--all conditions that may threaten hippocampal viability in rat. Here, we studied structural parameters of the porcine DG after 5 months of tethered housing in relation to basal saliva cortisol measured antemortem. We further investigated whether any neuropathology or alterations in apoptosis had occurred in the left hippocampal hemisphere. Stereological analysis revealed high correlations between DG volume and neuron number in individual animals in both hemispheres. Within individual animals, neuron numbers of the left and right lobes were not correlated. Notably, basal cortisol was negatively correlated with volume and neuron number of the left, but not the right DG. Although obvious neuropathology was absent, apoptosis was present in DG and alveus and less so in CA areas. Despite the short window of time during which apoptosis is detectable, their stereologically estimated numbers in the DG, but not in other regions, were negatively correlated with cortisol. In conclusion, our data indicate for the first time a profound lateralization in the relationship between DG structure, apoptosis, and basal cortisol after stress in pigs. Five months of chronic stress failed to induce lasting neuropathology. Although accumulating changes in apoptosis could have contributed to the structural DG alterations, further studies should reveal whether stress has been instrumental, or whether the differences between animals were present from birth onward. The present lateralization after stress is, however, consistent with lateralized hippocampal volume changes in stress-related human disorders and suggests that these effects are not limited to this species alone.

Behavioural Reactivity Affected by Chronic Stress: An Experimental Approach in Calves Submitted to Environmental Instability

Whereas physiological and behavioural responses to acute stressors are well documented, chronic stress remains difficult to assess in farm animals. The aim of the present paper is to investigate whether calves’ behavioural reactions to acute events are modified during chronic intermittent stress. Thirty-two calves housed in pairs were used. For half of the calves the partner and the pen were changed once a week for 14 weeks (regrouped calves) while the others remained unchanged (controls). Four behavioural tests were performed to assess calves’ reactivity to novel or sudden events, to predator cues and to restraint. In the water spray test, regrouped calves were startled more often. In the umbrella test, regrouped calves took a longer time to feed in front of the closed umbrella but no differences between the two treatments were observed on opening the umbrella. In the dog test, regrouped calves moved more and looked at the dog more often. In the restraint test, regrouped calves were more agitated. These differences disappeared when the tests were repeated. In conclusion, repeated changes in the social and physical environment of calves enhances their behavioural reactivity to novelty. This is likely to make them more adaptive to potential changes in their environment.

Western blotting for detection of glucocorticoid receptors in the brain and pituitary gland from adrenal intact pigs

The objectives of the experiments presented here were to develop a method for measuring total glucocorticoid receptors (GRs), in adrenal intact pigs, and to describe the distribution of this receptor in the pituitary gland and selected brain regions. Six male pigs, 14 days of age, were euthanized and the pituitary gland, hypothalamus, prefrontal cortex, and hippocampus were prepared for western blotting using a traditional soluble cytosolic preparation or a whole cell extract preparation. Samples were electrophoresed and immunoblotted using the anti-human GR antibodies #57 and #51. The #57 antibody labeled a doublet at 95 and 87 kDa whereas the #51 GR antibody labeled a single band at 87 kDa. Affinity labeling of GR with [(3)H] dexamethasone mesylate revealed a single band at 87 kDa. Using the soluble cytosolic preparation GR concentrations were highest in the pituitary gland followed by the hypothalamus (P<0. 0001). The amount of GR in the hippocampus and prefrontal cortex was equivalent but lesser (P<0.0001) than that found in the pituitary gland or hypothalamus. With the whole cell extract tissue preparation, GR concentrations were highest (P<0.05) in the prefrontal cortex and hippocampus with lower (P<0.05) levels detected in the hypothalamus. Taken together, these results indicated that the 87-kDa band was the functional GR and that regional distribution of GRs is specific to the type of tissue preparation used. In addition, we have described a procedure (from whole cell extracts) for measuring total GRs in neural and nonneural tissues from adrenal intact pigs.

Effect of glucocorticoid treatment on biochemical and hormonal blood parameters in early pregnant gilts

Twenty Polish Landrace gilts were grouped immediately after mating as follows: Experiment I-- Group 1 (5 gilts), control animals and Group 2 (5 gilts), injected i.m. with dexamethasone (30 mg/kg) at 12-h intervals from day 13 to day 22 of pregnancy; Experiment II--Group 3 (5 gilts), injected i.m. with corn oil from day 13 to day 22 of pregnancy and Group 4 (5 gilts), injected i.m. with hydrocortisone acetate (250 mg) at 12-h intervals from day 11 to day 20 of pregnancy. Gilts were placed in metabolic cages on day 7. On days 34-36 of pregnancy gilts were slaughtered and blood samples were collected. Serum was used for analysis of aspartate aminotransferase (S-ASAT), alanine aminotransferase (S-ALAT), alkaline phosphatase (S-ALP), S-cholesterol, S-triglycerides, S-fructosamine, S-urea, S-total protein, and for electrophoretic fractionation of serum proteins, corticosteroid-binding globulin (CBG), cortisol, progesterone, thyroxine (T4) and free T4. There were no significant differences between groups in embryonic survival or in number of viable fetuses after treatment with glucocorticoids. The activity of S-ALP was lower (p < 0.05) in Group 4 than in Group 3 (0.5 vs 1.2 mukat/l). Group 4 had higher (p < 0.05) levels of S-triglycerides (1.17 vs 0.73 mmol/l), S-cholesterol (5.4 vs 2.7 mmol/l), S-total protein (110.5 vs 93.3 g/l), S-albumin (56.3 vs 43.3 g/l) and alpha 2-globulin concentrations (18.0 vs 14.3 g/l) than Group 3. The hydrocortisone-treated gilts had lower (p < 0.05) CBG (6.8 vs 21.3 nmol/l) and beta 1-globulin (3.25 vs 5.0 g/l) concentrations than the oil-treated ones. Concentrations of T4 were lower (p < 0.05) in Groups 2 (61.3 nmo/l) and 4 (49.0 nmol/l) compared with control Groups 1 and 3 (88.2 and 97.0 nmol/l, respectively). Overall, the treatment of early pregnant gilts with hydrocortisone acetate resulted in decreased levels of S-ALP, CBG, beta 1-globulin and T4, and in increased levels of S-cholesterol, S-triglycerides, S-total protein, S-albumin and alpha 2-globulin. The only effect of dexamethasone was a lowering of T4. There were no differences in free T4, S-fructosamine or S-urea between controls and treatments. Furthermore a negative correlation between triglycerides concentrations and the number of embryos (r = -0.76, p < 0.05) was found in control untreated and oil-treated pregnant gilts.

Mifepristone modulation of ACTH and CRH regulation of bovine adrenocorticosteroidogenesis in vitro

Mifepristone (RU486), bovine corticotropin-releasing hormone (CRH), arginine vasopressin (VP), adrenocorticotropin (ACTH1-24), and protein kinase activators (forskolin, [FSK]; phorbol 12-myristate 13-acetate [PMA]) were used in vitro to investigate their direct effect on adrenocorticosteroidogenesis. Bovine adrenocortical fasciculata/reticularis cells (2 x 10(5) viable cells/well) were cultured for 3 d in medium supplemented with 10% fetal calf serum. After incubation for an additional 24 hr in serum-free medium, cells were treated with serum-free medium alone (Control) or various concentrations of ACTH, CRH, VP, FSK, PMA, RU486, and/or various concentrations for 1, 2, 4, or 24 hr. Medium content of cortisol and progesterone were determined by radioimmunoassays. ACTH, CRH, FSK, and PMA each stimulated (P < 0.05) secretion of cortisol in time- and dose-related manners. Although these agents stimulated (P < 0.05) secretion of progesterone in a dose-related manner, medium content of progesterone declined (P < 0.05) over time. The minimal effective doses of ACTH and CRH required to stimulate (P < 0.05) secretion of cortisol relative to the Control over a 4-hr culture period were 0.01 nM and 3 nM, respectively. Relative to observations at 1 hr posttreatment, 24-hr treatment with ACTH or CRH increased the medium content of cortisol by an additional 19.8- and 48-fold, respectively (whereas content of progesterone declined over that time period). VP-stimulated secretion of cortisol was time- (P < 0.05) but not dose-related. Specifically, by 24-hr posttreatment, the medium content of cortisol was increased (P < 0.05) 4.6-fold relative to the quantity of cortisol secreted by 1-hr postaddition of VP (0.01 to 1 microM). Co-treatment with RU486 (1 microM) decreased (p < 0.05) FSK-, ACTH- and CRH-stimulated secretion of cortisol by 77, 27, and 56%, respectively. Similarly, the stimulatory effects of ACTH and CRH on progesterone secretion were reduced (P < 0.05) by 40 and 22%, respectively, by co-addition of RU486. The inhibitory action of RU486 on production of cortisol was no longer apparent by 24 hr after treatment. These observations indicate that RU486 can act as a steroid agonist and as well as an antagonist. These data characterize time- and dose-related direct actions of ACTH, CRH, and RU486 on adrenocorticosteroidogenesis. This information will assist efforts to clarify complex intra-adrenal interactions of neurohormones, growth factors, and endogenous steroids.

Restraint, but not frustration, induces prostaglandin-mediated hyperthermia in pigs

Three experiments were carried out to investigate stress hyperthermia in prepubertal pigs. Experiment 1 examined the effect of frustrative nonreward (psychological stress) on deep body temperature in animals (n = 7) trained to make operant responses for food following a 17.5-h period of deprivation. There was no change in body temperature when the feeders were switched off whereas there was a small increase (NS) during normal operant feeding that might be attributable to physical exertion. In Experiment 2, the effects of 15-min physical restraint (snaring) were examined in the same group of animals. This procedure induced a significant (p < 0.01) rise in core temperature that was completely abolished by prior administration of a cyclooxygenase inhibitor (indomethacin, 2 mg/kg given intravenously). The final experiment investigated the effects of snaring on plasma cortisol concentrations. Blood samples were taken from indwelling catheters in pigs (n = 5) subjected to 15-min restraint with, or without, indomethacin pretreatment. Snaring produced a significant (p < 0.001) increase in cortisol release that was not affected by the administration of indomethacin. These results suggest that snaring, a physical stress that may also have energy expenditure components, induces a prostaglandin-mediated hyperthermic response in the growing pig.