There is growing evidence that positive social interactions can attenuate the effects of stressful life experiences. However, little is known about the benefits of social partners on stress responses in farm animals. Therefore, in this study we examined the effects of social support on the endocrine and immune stress responses to a single 4h social deprivation in domestic piglets at 7, 21 or 35days of age. The piglets were socially deprived of their mother and littermates. They were left alone (DA) or in the presence of a familiar (DF) or unfamiliar (DU) age-matched piglet. Non-socially deprived piglets served as a control. DA piglets displayed elevated plasma cortisol levels, higher lipopolysaccharide (LPS)-stimulated proliferation of splenocytes and increased TNF-? and IL-6 production in splenocyte cultures than the control piglets. There were no significant buffering effects of social partners on stress-induced plasma cortisol levels and splenocyte proliferation in response to LPS. However, the presence of an age-matched conspecific diminished the IL-6 production by splenocytes in younger, socially deprived piglets, and it reduced the TNF-? release in the older piglets. Compared to the controls, LPS-stimulated splenocytes from DA piglets were more resistant to the inhibitory effects of cortisol, which was demonstrated by a higher proliferative response and increased production of pro-inflammatory cytokines. The dose-dependent cortisol resistance was attenuated by the presence of a familiar or an unfamiliar conspecific at each of the three age categories. Indeed, in the present study, the familiarity level of the social partners did not seem to play a role in the alleviation of social stress-induced inflammatory activity and splenocyte cortisol resistance. In addition, the buffering effect of social support provided by an age-matched conspecific was more pronounced in older piglets. Conclusively, these findings suggest that social support is an important factor for enhancing piglets' abilities to cope with stressful challenges, and it may be a key approach needed to improve the health and welfare of farm animals.
Social deprivation is a severe stressor affecting a number of behavioral and physiological functions of gregarious species. It is assumed that, dependent upon the level of familiarity, social support given by a conspecific may attenuate the adverse consequences of stress. We investigated the effects of a 4h maternal and littermate deprivation on behavioral reactions, stress hormone responses and brain corticosteroid receptor expression in 7-, 21- and 35-day-old domestic piglets (Sus scrofa) that were left alone or in the presence either of a familiar or unfamiliar age-matched piglet. Compared to control animals, all of the socially deprived piglets showed significant stress responses, such as impaired habituation in repeated open-field/novel-object tests, enhanced ACTH and cortisol release, and altered corticosteroid receptor expression in the hypothalamus. In addition, our results demonstrated that younger piglets had more difficulty coping with stress. The presence of an age-matched conspecific had a direct calming effect on the deprived piglet during the deprivation procedure, which was revealed by diminished stress-induced HPA activity and altered reactions in the behavioral test situations (e.g., activity, escape, and vocalization). Furthermore, because the presence of a familiar piglet causes a more pronounced buffering effect, we have shown for the first time that the degree of familiarity between the piglets may influence the effectiveness of social support. Our study emphasizes the benefits of social partners on positive welfare and the ability for pigs to cope with stress; therefore, our results should be taken into account during handling practices such as weaning and mixing.
Indoleamine 2,3-dioxygenase (IDO) is a rate-limiting enzyme for the degradation of tryptophan (Trp) along the kynurenine (Kyn) pathway, and its increased activation is associated with immunologic disorders. Because the specific role of IDO activation is not yet completely clear, the aim of the present study was to establish a pig model of IDO activation for further research. The activation of IDO in pigs was induced experimentally by LPS stimulation in vivo and ex vivo. IDO activation was characterized by measuring Trp, Trp metabolites and IDO protein expression in blood, liver, lung, muscle and different brain areas. The results show that the in vivo LPS administration induced increased plasma concentrations of TNF-? and IL-10, a depletion of Trp and an increase of Kyn, indicating an elevated enzymatic activity of IDO. This was supported by an LPS-induced IDO protein expression in blood, liver and lung. The ex vivo LPS stimulation also resulted in increased TNF-? concentrations and an IDO activation, characterized by an increase of Trp metabolites and IDO protein expression. In conclusion, our data emphasize that the LPS stimulation is a suitable model for IDO activation in the domestic pig, which provides a basis for further research on immunoregulatory IDO functions.
Uncoupling protein 2 (UCP2) is a mitochondrial protein that reduces oxidative stress and has a protective function in chronic inflammatory diseases such as multiple sclerosis, rheumatoid arthritis and systemic lupus erythematosus. UCP2 is strongly expressed in areas implicated in the central regulation of stress and anxiety. Therefore, we compared the neuroendocrine regulation of stress responses, immunity and behavior in UCP2-deficient and wildtype C57BL/6J mice under psychological stress.
Negative early life experience may be associated with altered functioning of stress-related systems and may increase vulnerability to diseases later in life. Corticosteroids are important mediators of homeostasis and stress and exert their effects via two receptors, the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR), and through the glucocorticoid-metabolizing enzymes 11?-hydroxysteroid dehydrogenase (11?-HSD) types 1 and 2 in a brain-region-specific manner. However, relatively little is known about the postnatal ontogeny of these receptors and enzymes in the central nervous system. Here we describe, for the first time, the postnatal ontogeny of central GR, MR, 11?-HSD1, and 11?-HSD2 gene expression and monoamine levels in stress-related brain regions of domestic pigs at 7, 21, and 35 days of age. During the postnatal period, there was an increase in GR, MR, and 11?-HSD1 mRNA expression in the pituitary and prefrontal cortex and an increase in MR mRNA expression in the hippocampus. We also demonstrated age-dependent changes in levels of noradrenaline and dopamine and their metabolites in the locus coeruleus, with the highest concentrations on day 7 compared with days 21 and 35. In conclusion, the dynamic changes in corticosteroid receptors and monoamines during neural development of postnatal pigs may represent periods of sensitivity to environmental stress that are comparable to some extent with those that are observed in primates and humans. Thus, these findings support the use of the domestic pig as an alternative animal model for humans in stress research.
Glucose supply markedly changes during the transition to extrauterine life. In this study, we investigated diet effects on glucose metabolism in neonatal calves. Calves were fed colostrum (C; n = 7) or milk-based formula (F; n = 7) with similar nutrient content up to d 4 of life. Blood plasma samples were taken daily before feeding and 2 h after feeding on d 4 to measure glucose, lactate, nonesterified fatty acids, protein, urea, insulin, glucagon, and cortisol concentrations. On d 2, additional blood samples were taken to measure glucose first-pass uptake (FPU) and turnover by oral [U-(13)C]-glucose and i.v. [6,6-(2)H(2)]-glucose infusion. On d 3, endogenous glucose production and gluconeogenesis were determined by i.v. [U-(13)C]-glucose and oral deuterated water administration after overnight feed deprivation. Liver tissue was obtained 2 h after feeding on d 4 and glycogen concentration and activities and mRNA abundance of gluconeogenic enzymes were measured. Plasma glucose and protein concentrations and hepatic glycogen concentration were higher (P < 0.05), whereas plasma urea, glucagon, and cortisol (d 2) concentrations as well as hepatic pyruvate carboxylase mRNA level and activity were lower (P < 0.05) in group C than in group F. Orally administered [U-(13)C]-glucose in blood was higher (P < 0.05) but FPU tended to be lower (P < 0.1) in group C than in group F. The improved glucose status in group C resulted from enhanced oral glucose absorption. Metabolic and endocrine changes pointed to elevated amino acid degradation in group F, presumably to provide substrates to meet energy requirements and to compensate for impaired oral glucose uptake.
Stressful early life experiences can have short- and long-term effects on neuroendocrine and immune mechanisms of adaptation, which are primarily modulated by glucocorticoids. This study aimed to examine how the stress and immune systems interact to cope with psychosocial stress induced by a single social isolation (4 h) in neonatal pigs at 7, 21, or 35 d of age. This social isolation provoked increased plasma ACTH and cortisol concentrations and reduced TNF-? levels but had no significant effect on IL-6 levels. Socially isolated piglets had a higher lipopolysaccharide (LPS)-stimulated proliferative response of peripheral blood mononuclear cells (PBMCs) than controls, whereas concanavalin A (ConA)-induced proliferation was not affected by isolation. A single social isolation also induced a dose-dependent cortisol resistance in ConA- and LPS-stimulated PBMCs compared with controls, which may be an adaptive response in the short term. Moreover, LPS-stimulated cultures from control piglets showed a reduction in cortisol sensitivity with increasing age. Conclusively, these findings provide stress-related measures for the psychophysiological assessment of livestock handling practices but might also have implications for stress and health studies in young animals and humans.
Weaning of farm animals is of biological and economical relevance. Due to economical considerations, the weaning age of piglets (Sus scrofa) has drastically been reduced during the last few years, whereas biological consequences remain ambiguous. This review gives a survey of current international research on weaning and its psychobiological consequences in conventional pig farming. The influence of weaning age on behaviour, neuroendocrine and immune systems of piglets is the main focus of this paper. The abrupt weaning in pig farming comprises multiple stressful events such as change in diet, new physical environment, as well as the often underestimated psychosocial consequences of maternal deprivation and regrouping with unfamiliar conspecifics. Results presented in this review suggest that early weaned piglets (< or = 21 days of age) show enhanced behavioural problems and neuroendocrine stress reactions as well as reduced immune responses. These adaptation problems may have short- and long-term effects on animals welfare and health, consequently resulting in increased financial requirements and higher management demands. Weaning before the third week of age is not recommended. Additionally, alternative housing systems (e.g. group housing) with adequate weaning methods (e.g. weaning without regrouping, social contacts prior to weaning) to diminish psychosocial stress are discussed.
The aim of the study was to determine the effects of a single social isolation (4h) of piglets on immediate changes in stress hormones and immune responses at 7, 21 or 35 days of age. This social stressor caused an increase in plasma ACTH and cortisol concentrations and a decrease in plasma TNF-alpha. The percentage of CD8+ cells increased and the CD4+ cell percentage decreased, resulting in decreasing CD4+/CD8+ ratio. The observed changes were consistent for all days studied. Further, the isolation treatment resulted in diminished LPS-stimulated IL-1beta and IL-10 production in whole-blood cultures. In isolated piglets, positive correlations were estimated between changes in percentage of CD8+ cells and cortisol, and negative ones between changes in plasma TNF-alpha and culture supernatant IL-1beta with ACTH and cortisol. The data suggest that psychosocial stress in neonatal pigs induced immune alterations to maintain adaptive stability, but reflecting also negative emotions experienced by this treatment.
Some housing conditions and practices in livestock husbandry may be stressful for the animals and may impair their welfare.This is of particular relevance for pregnant dams, because it is known from rodents and primates that prenatal stress (i. e. stress experienced by the mother with impact on the fetal ontogeny) may have long-lasting effects on growth, health and behaviour of the offspring. This review gives a survey of current research on prenatal stress and its consequences in farm animals. In comparison to the well-studied rodent model there are differences in placental structure and prenatal ontogeny. However, the research reveals that also in farm animals prenatal stress can lead to an impairment of growth, immune function, behaviour and stress reactivity in the offspring. Maternal glucocorticoids are discussed as potential mediators and it has been demonstrated that the effects on the offspring depend on the nature of the stressor as well as on its time and duration during gestation. Because prenatal stress in farm animals may be a source of economic and welfare problems by reason of reduced vitality and well-being of the offspring, suggestions for future work in this field of research are made.
Previous reports have demonstrated that the mtDNA of mouse common inbred strains (CIS) originated from a single female ancestor and that mtDNA mutations occurred during CIS establishment. This situation provides a unique opportunity to investigate the impact of individual mtDNA variations on complex traits in mammals. In this study, we compiled the complete mtDNA sequences of 52 mouse CIS. Phylogenetic analysis demonstrated that 50 of the 52 CIS descended from a single female Mus musculus domesticus mouse, and mtDNA mutations have accumulated in 26 of the CIS. We then generated conplastic strains on the C57BL/6J background for 12 mtDNA variants with one to three functional mtDNA mutations. We also generated conplastic strains for mtDNA variants of the four M. musculus subspecies, each of which contains hundreds of mtDNA variations. In total, a panel of conplastic strains was generated for 16 mtDNA variants. Phenotypic analysis of the conplastic strains demonstrated that mtDNA variations affect susceptibility to experimental autoimmune encephalomyelitis and anxiety-related behavior, which confirms that mtDNA variations affect complex traits. Thus, we have developed a unique genetic resource that will facilitate exploration of the biochemical and physiological roles of mitochondria in complex traits.
We studied the behavior and neuroendocrine regulation under social disruption stress of C57BL/6J mice in which mitochondria were substituted by mitochondria from AKR/J or FVB/N strains. C57BL/6J-mt(FVB/N) mice were significantly more anxious in the elevated plus-maze test than C57BL/6J-mt(AKR/J) and C57BL/6J mice at base line. In addition, they showed a reduced corticosterone response and an activation of serotonergic and dopaminergic neurotransmitter systems after repeated challenge, i.e., social defeat and elevated plus-maze test. Our findings suggest that mitochondrial variations could affect anxiety-like behavior as well as corticosterone and neurotransmitter response to psychological stress.
Imbalanced maternal nutrition during gestation can cause alterations of the hypothalamic-pituitary-adrenal (HPA) system in offspring. The present study investigated the effects of maternal low- and high-protein diets during gestation in pigs on the maternal-fetal HPA regulation and expression of the glucocorticoid receptor (GR), mineralocorticoid receptor (MR), 11?-hydroxysteroid dehydrogenase 1 and 2 (11?-HSD1 and 11?-HSD2) and c-fos mRNAs in the placenta and fetal brain. Twenty-seven German Landrace sows were fed diets with high (HP, 30%), low (LP, 6.5%) or adequate (AP, 12.1%) protein levels made isoenergetic by varying the carbohydrate levels. On gestational day 94, fetuses were recovered under general anesthesia for the collection of blood, brain and placenta samples. The LP diet in sows increased salivary cortisol levels during gestation compared to the HP and AP sows and caused an increase of placental GR and c-fos mRNA expression. However, the diurnal rhythm of plasma cortisol was disturbed in both LP and HP sows. Total plasma cortisol concentrations in the umbilical cord vessels were elevated in fetuses from HP sows, whereas corticosteroid-binding globulin levels were decreased in LP fetuses. In the hypothalamus, LP fetuses displayed an enhanced mRNA expression of 11?-HSD1 and a reduced expression of c-fos. Additionally, the 11?-HSD2 mRNA expression was decreased in both LP and HP fetuses. The present results suggest that both low and high protein?carbohydrate dietary ratios during gestation may alter the expression of genes encoding key determinants of glucocorticoid hormone action in the fetus with potential long-lasting consequences for stress adaptation and health.
Inadequate nutrition in utero may retard foetal growth and alter physiological development of offspring. This study investigated the effects of low and high protein diets fed to primiparous German Landrace sows throughout pregnancy on the immune function of their offspring at different ages. Sows were fed diets with adequate (AP, 12.1%; n?=?13), low (LP, 6.5%; n?=?15), or high (HP, 30%; n?=?14) protein content, made isoenergetic by varying carbohydrate levels. Cortisol, total protein and immunoglobulin (IgG, IgM, IgA) concentrations were measured in the blood of sows over the course of pregnancy. Cortisol, total protein, immunoglobulins, lymphocyte proliferation, immune cell counts, and cytokines were assessed in the blood of offspring at baseline and under challenging conditions (weaning; lipopolysaccharide (LPS) administration).
Tumour necrosis factor (TNF)-alpha is known to be involved in anxiety and the regulation of the hypothalamic-pituitary-adrenal axis. To examine the role of its receptors in neuroendocrine immunomodulation, we studied behaviour, corticosterone production and T-cell activation in mice with a C57BL/6J background and deficient for one or both TNF receptors (TNFR1-/-, TNFR2-/-, and TNFR1+2-/-) compared to wildtype C57BL/6J mice with and without psychological stress. Stress was induced by social disruption (SDR), and anxiety-like behaviour was examined using the elevated plus maze (EPM). Anxiety of unstressed TNFR1+2-/- mice was increased compared to C57BL/6J mice as shown by reduced ratios of entries into open arms relatively to total entries. SDR-stressed TNFR1+2-/- mice showed reduced ratios of entries into open arms relatively to total entries, reduced ratios of distances walked in open relatively to distances walked in both arms and reduced time in open arms compared to C57BL/6J mice. Locomotor activity of unstressed and SDR-stressed TNFR1-/- and TNFR2-/- mice was reduced. Serum corticosterone concentrations of control mice do not differ between mouse strains. However, TNFR1+2-/- mice had significantly higher corticosterone concentrations than C57BL/6J mice after SDR. EPM testing significantly increased corticosterone concentrations in all strains. Mitogen-induced activation-marker expression was reduced in TNFR1-/- T-helper cells under control and stress conditions, while activation marker expression of TNFR2-/- and TNFR1+2-/- cells was only slightly affected by stress compared to C57BL/6J T cells. Our study suggests that both TNF receptors contribute to anxiety-like behaviour and corticosterone responses, whereas TNFR1 has a larger impact on T-cell activation.
High and low protein diets fed to pregnant adolescent sows led to intrauterine growth retardation (IUGR). To explore underlying mechanisms, sow plasma metabolite and hormone concentrations were analyzed during different pregnancy stages and correlated with litter weight (LW) at birth, sow body weight and back fat thickness. Sows were fed diets with low (6.5%, LP), adequate (12.1%, AP), and high (30%, HP) protein levels, made isoenergetic by adjusted carbohydrate content. At -5, 24, 66, and 108 days post coitum (dpc) fasted blood was collected. At 92 dpc, diurnal metabolic profiles were determined. Fasted serum urea and plasma glucagon were higher due to the HP diet. High density lipoprotein cholesterol (HDLC), %HDLC and cortisol were reduced in HP compared with AP sows. Lowest concentrations were observed for serum urea and protein, plasma insulin-like growth factor-I, low density lipoprotein cholesterol, and progesterone in LP compared with AP and HP sows. Fasted plasma glucose, insulin and leptin concentrations were unchanged. Diurnal metabolic profiles showed lower glucose in HP sows whereas non-esterified fatty acids (NEFA) concentrations were higher in HP compared with AP and LP sows. In HP and LP sows, urea concentrations were 300% and 60% of AP sows, respectively. Plasma total cholesterol was higher in LP than in AP and HP sows. In AP sows, LW correlated positively with insulin and insulin/glucose and negatively with glucagon/insulin at 66 dpc, whereas in HP sows LW associated positively with NEFA. In conclusion, IUGR in sows fed high protein:low carbohydrate diet was probably due to glucose and energy deficit whereas in sows with low protein:high carbohydrate diet it was possibly a response to a deficit of indispensable amino acids which impaired lipoprotein metabolism and favored maternal lipid disposal.
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