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Teicher, M. H., Tomoda, A., & Andersen, S. L. (2006). Neurobiological Consequences of Early Stress and Childhood Maltreatment: Are Results from Human and Animal Studies Comparable? Annals of the New York Academy of Sciences, 1071(1), 313–323.
Abstract: Abstract: Recent studies have reported an association between exposure to childhood abuse or neglect and alterations in brain structure or function. One limitation of these studies is that they are correlational and do not provide evidence of a cause–effect relationship. Preclinical studies on the effects of exposure to early life stress can demonstrate causality, and can enrich our understanding of the clinical research if we hypothesize that the consequences of early abuse are predominantly mediated through the induction of stress responses. Exposure to early abuse and early stress has each been associated with the emergence of epileptiform electroencephalogram (EEG) abnormalities, alterations in corpous callosum area, and reduced volume or synaptic density of the hippocampus.Further, there is evidence that different brain regions have unique periods when they are maximally sensitive to the effects of early stress. To date, preclinical studies have guided clinical investigations and will continue to provide important insight into studies on molecular mechanisms and gene–environment interactions.
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Ayala, I., Martos, N. F., Silvan, G., Gutierrez-Panizo, C., Clavel, J. G., & Illera, J. C. (2012). Cortisol, adrenocorticotropic hormone, serotonin, adrenaline and noradrenaline serum concentrations in relation to disease and stress in the horse. Research in Veterinary Science, 93(1), 103–107.
Abstract: No detailed comparative data are available on the hormonal parameters of horses suffering from a number of diseases. The aim of our study was to measure concentrations of cortisol, adrenocorticotropic hormone (ACTH), serotonin, adrenaline and noradrenaline in horses with various diseases and following surgery, to assess the response of the HPA axis and adrenal medulla. Blood samples were obtained from six groups of horses comprising a total of 119 animals as follows: laminitis, acute abdominal syndrome (AAS), castration surgery, acute diseases, chronic diseases and healthy controls. Serum hormonal concentrations were determined for each group for comparison. Statistically significant differences between all groups and controls were found for cortisol, ACTH (except for castration), serotonin and adrenaline concentrations but only in horses with laminitis and AAS for noradrenaline. No statistically significant differences were found between males and females. The largest changes in the pituitary–adrenal axis activity occurred mainly in acute diseases, laminitis and in the AAS group.
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Reyna-Garfias, H., Miliar, A., Jarillo-Luna, A., Rivera-Aguilar, V., Pacheco-Yepez, J., Baeza, I., et al. (2010). Repeated restraint stress increases IgA concentration in rat small intestine. Brain, Behavior, and Immunity, 24(1), 110–118.
Abstract: The most abundant intestinal immunoglobulin and first line of specific immunological defense against environmental antigens is secretory immunoglobulin A. To better understand the effect of repeated stress on the secretion of intestinal IgA, the effects of restraint stress on IgA concentration and mRNA expression of the gene for the alpha-chain of IgA was assessed in both the duodenum and ileum of the rats. Restraint stress induced an increase in intestinal IgA, which was blocked by an adrenalectomy, suggesting a role of catecholamines and glucocorticoids. Whereas the blocking of glucocorticoid receptors by RU-486 did not affect the increased IgA concentration, it did reduce IgA alpha-chain mRNA expression in both segments, indicating a possible mediation on the part of glucocorticoids in IgA secretion by individual cells. Treatment with corticosterone significantly increased both the IgA concentration and IgA alpha-chain mRNA expression in ileum but not in duodenum, suggesting that glucocorticoids may act directly on IgA-antibody forming cells to increase IgA secretion in the former segment. A probable role by catecholamines was evidenced by the reduction in IgA concentration and IgA alpha-chain mRNA expression in both segments after a chemical sympathectomy with 6-hydroxydopamine (6-OHDA). Additionally, norepinephrine significantly reduced IgA alpha-chain mRNA levels but increased pIgR mRNA expression and IgA concentration in both intestinal segments. We propose that the increased intestinal IgA levels caused by repeated restraint stress is likely due to the effects of catecholamines on the transport of plgA across the epithelium.
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Rietmann, T. R., Stuart, A. E. A., Bernasconi, P., Stauffacher, M., Auer, J. A., & Weishaupt, M. A. (2004). Assessment of mental stress in warmblood horses: heart rate variability in comparison to heart rate and selected behavioural parameters. Appl. Anim. Behav. Sci., 88(1-2), 121–136.
Abstract: The aim of the study was to investigate whether heart rate variability (HRV) could assess alterations of the autonomic nervous system (ANS) at different levels of excitement. The behavioural and physiological responses of 20 warmblood horses to a challenging ground exercise task were studied. Prior to the experiment, the horses were evaluated at rest and during forward walking (FW). The horses were then forced to move backwards continuously during 3 min according to a standardised protocol (BW1). Subsequently, the horses were exposed to two training sessions, after which the backward walking (BW2) was re-evaluated. Heart rate (HR) and HRV-parameters such as the standard deviation of the beat-to-beat intervals (SDRR), the low (LF; sympathetic tone) and high frequency (HF) component of HRV (HF; parasympathetic tone) and their ratio (LF/HF; index representing the sympatho-vagal balance) were sampled at rest, and during FW, BW1 and BW2. Stress-related behaviour during BW1 and BW2 was determined from video recordings. The results of the different evaluations were compared to each other. Compared to rest and FW, the first backward experiment induced a significant rise in HR, LF and LF/HF and a significant decrease of HF. SDRR decreased from both FW and rest with only the latter reaching significance. In BW2 after the training sessions, HR and the parameters of the sympathetic branch of the ANS (LF, LF/HF) were decreased and the vagal tone (HF) increased compared to BW1; all changes were significant. The duration of stress indicating behavioural patterns revealed also a significant decrease of excitement after the training, when backward walking did not differ from forward walking in any parameter. Correlations between HRV-parameters and stress indicating behaviour as well as HR were found. We conclude that the HRV-parameters LF and HF are valuable measures to quantify sympatho-vagal balance, which allows a more precise assessment of the responses of HR and SDRR to mental stress during low intensity exercise.
Keywords: Horse; Hrv; Heart rate; Mental stress; Behaviour; Autonomic nervous system
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McGee, S., & Smith, H. V. (2004). Accompanying pre-weaned Thoroughbred (Equus caballus) foals while separated from the mare during covering reduces behavioural signs of distress exhibited. Appl. Anim. Behav. Sci., 88(1-2), 137–147.
Abstract: Some Thoroughbred stallion farms separate the mare from the foal during breeding, leaving the foal alone in its stall. Such separation often leads to distress in the foal, as evidenced by behavioural indicators such as vocalisations, pacing or moving about, pawing and striking the body against solid objects. This study examined whether the foal's distress is reduced if a handler accompanies it during the period of separation. A total of 57 foals on an Irish stud farm were observed: 27 foals were accompanied during separation and 30 were left in isolation but discretely observed from outside the stall. On average, unaccompanied foals vocalised at significantly (P<0.001) shorter intervals (14.8 s versus 26.8 s), and spent significantly (P<0.05) more time pawing (29.6 s versus 6.8 s) than accompanied ones. In addition, 17 of the unaccompanied foals hurled themselves against a solid object on at least one occasion, while not one of the accompanied foals did this (P<0.001). Age, gender and number of times the foal had been previously separated from the mare while she was being teased or covered were not significantly related to any of the behavioural indicators of distress. Overall, the data provide clear evidence that accompanying a foal reduces the distress that it exhibits when separated from the mare. This procedure has obvious welfare benefits in the short term, in that the foal both experiences less distress and has a reduced likelihood of injuring itself, and it may have longer-term benefits by reducing the chance of the animal later developing a locomotory stereotypical behaviour.
Keywords: Distress; Foals; Maternal separation; Stereotypies; Welfare
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Waran, N. K., Clarke, N., & Farnworth, M. (2008). The effects of weaning on the domestic horse (Equus caballus). Appl. Anim. Behav. Sci., 110(1-2), 42–57.
Abstract: For free-living or feral horses weaning takes place naturally at around 8-9 months [Gill, E.L., 1988. Factors affecting body condition of New Forest Ponies. Ph.D. Thesis. Department of Biology, University of Southampton]. Some mares will continue to suckle their foal until shortly before the arrival of their next foal, gestation being approximately 342 days depending upon the breed of the horse [Ropiha, R.T., Mathews, G., Butterfield, R.M., 1969. The duration of pregnancy in Thoroughbred mares. Vet. Rec. 84, 552-555]. Under domestic conditions, weaning tends to take place earlier, typically between 4 and 6 months of age. The weaning process has been identified as associated with potential psychological, physical and nutritional stressors that are of welfare concern. Following a review of the literature it is evident that there is a need for detailed research into what should constitute best practice with respect to foal and mare welfare. In addition, there is a need to understand the potential long-term impact of weaning on, for example, trainability and later maternal behaviour, and whether the stresses associated with early weaning have detrimental effects on the performance horse. There is also a lack of clear information concerning the most frequently observed weaning practices and the reasons why certain weaning methods are chosen. Some variables should be closely managed during weaning in order to minimise stress responses. These include: early creep feeding to familiarise the young animal with the food it will be exposed to during weaning, feeding a high fibre diet and keeping the animal in extensive conditions using a gradual approach to weaning. However, we conclude that there may not be one best method for weaning, since the chosen method must take into account a number of factors including: available resources, the housing environment, the individual foal's stage of development, the strength of the mare-foal attachment, the foal's ability to cope with changes in social conditions and the ability of the horse owner to implement the chosen method. We do however suggest that the fewest stress responses appear to occur where foals are weaned gradually and allowed to have social contact either with other foals or with older horses.
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Waiblinger, S., Menke, C., Korff, J., & Bucher, A. (2004). Previous handling and gentle interactions affect behaviour and heart rate of dairy cows during a veterinary procedure. Appl. Anim. Behav. Sci., 85(1-2), 31–42.
Abstract: Veterinary and management procedures often are aversive to the animals, resulting in physiological and behavioural stress reactions, which increase the risk of accidents and might lower performance. We investigated the effects of previous positive handling and of gentle interactions during the procedure on behaviour and heart rate in dairy cows during rectal palpation with sham insemination. Twenty cows were allocated randomly into two groups of 10 animals: handling, received additional positive handling over a period of four weeks by one person (handler); control, only routine handling by different caretakers. The week after the handling period, tests lasting 9 min, including 4 min rectal palpation, were carried out with each animal on four successive days in four situations in a balanced order: cow is alone during the test, with the handler, with an usual caretaker, or with an unknown person. Behaviour and heart rate were recorded. Previously handled animals had lower heart rate during tests (P<=0.05, n=19), kicked less when alone (P<=0.05, n=19) and tended to show less restless behaviour (P<=0.1, n=19). Cows were further calmed by gentle interactions during the test, but people differed remarkably. Cows showed less restless behaviour when gentled by the handler, both in the 4 min of rectal palpation and in the 9 min test period (each: P<=0.001, n=19). No significant stress reducing effect was found for the other two persons. In conclusion, stress reactions of cows during rectal palpation/insemination can be reduced by previous positive handling as well as by a person providing positive, gentle interactions during the procedure. The results underline the importance of positive, gentle interactions with the animals to enhance animal welfare and reduce the risk of accidents. They also show that people differ in the success to calm down the animals in aversive situations and indicate the need to investigate the characteristics responsible for the differences and identify the preconditions for a stress reducing effect in future research.
Keywords: Human-animal relationship; Cattle; Handling; Stress; Heart rate; Welfare
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Rogers, L. J. (2010). Relevance of brain and behavioural lateralization to animal welfare. Appl. Anim. Behav. Sci., 127(1-2), 1–11.
Abstract: The left and right sides of the brain are specialised to process information in different ways and to control different categories of behaviour. Research on a range of species has shown that the left hemisphere controls well-established patterns of behaviour performed in non-stressful situations, whereas the right hemisphere responds to unexpected stimuli and controls escape and other emergency responses. The known functions of each hemisphere are summarised in this paper. Then it is hypothesised that stressed animals rely on predominant use of the right hemisphere, and that a bias to use the right or left hemisphere, respectively, may explain the behavioural differences between animals with a negative cognitive bias and those with a positive cognitive bias. In some species of primates it has been shown that the preferred limb used to pick up food when the animal is in a relaxed state reflects the dominant hemisphere and may be an accessible measure indicating susceptibility to stress and tendency towards positive versus negative cognitive bias. Hence, limb preference might be a useful measure of such tendencies in domesticated species. Some difficulties in determining a relevant measure of limb preference in non-primate species are mentioned, followed by the suggestion that eye preferences for viewing certain stimuli may be a useful measure in species with laterally placed eyes. Finally, effects of experience on the development of hemispheric dominance are discussed, leading to a suggestion that the welfare of domestic animals may be enhanced by ensuring development of left hemisphere dominance (e.g. by exposing chick embryos to light) and by shifting right to left hemisphere dominance in animals with negative cognitive bias.
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Massen, J., Sterck, E., & de Vos, H. (2010). Close social associations in animals and humans: functions and mechanisms of friendship (Vol. 147).
Abstract: Both humans and group-living animals associate and behave affiliatively more with some individuals than others. Human friendship has long been acknowledged, and recently scientists studying animal behaviour have started using the term friendship for close social associates in animals. Yet, while biologists describe friends as social tools to enhance fitness, social scientists describe human friendship as unconditional. We investigate whether these different descriptions reflect true differences in human friendship and animal close social associations or are a by-product of different research approaches: namely social scientists focussing on proximate and biologists on ultimate explanations. We first stress the importance of similar measures to determine close social associations, thereafter examine their ultimate benefits and proximate motivations, and discuss the latest findings on the central-neural regulation of social bonds. We conclude that both human friendship and animal close social associations are ultimately beneficial. On the proximate level, motivations for friendship in humans and for close social associations in animals are not necessarily based on benefits and are often unconditional. Moreover, humans share with many animals a similar physiological basis of sociality. Therefore, biologists and social scientist describe the same phenomenon, and the use of the term friendship for animals seems justified.
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Marr, I., Stefanski, V., & Krueger, K. (2022). Lateralität – ein Indikator für das Tierwohl?[Laterality – an animal welfare indicator?]. Der Praktische Tierarzt, 103(12/2022), 1246–12757.
Abstract: Ein gutes Tierwohl definiert sich nicht nur durch die Abwesenheit von Stressindikatoren, sondern auch durch das Vorhandensein von Indikatoren, die auf ein gutes Wohlergehen hinweisen. So können stressbedingte Erkrankungen vermieden werden. Zur Bestimmung des Tierwohls bei Pferden wurde daher untersucht, inwieweit sich die sensorische Lateralität (einseitiger Gebrauch von Sinnesorganen) und die motorische Lateralität (einseitiger Gebrauch von Gliedmaßen) als einfach, schnell und kostengünstig zu erhebende Parameter eignen. Hierzu werden neben aktueller Literatur auch die eigenen Untersuchungsergebnisse zusammenfassend dargestellt. Die nach außen sichtbar werdende sensorische und motorische Lateralität sind das Resultat der cerebralen Lateralisierung. Dies beinhaltet nicht nur die Aufgabenteilung beider Gehirnhälften für ein effizienteres Aufnehmen und Speichern von Informationen, sondern sie steht auch in Verbindung mit der Entstehung und Verarbeitung von Emotionen, die maßgeblich am Wohlergehen eines Lebewesens beteiligt sind. Kurzzeitige Stressoren führen zu einer Erregung, die je nach Erfahrungen mit positiven oder negativen Emotionen in Verbindung steht. Emotionen helfen dem Organismus dabei, zu überleben. Andauernde negative Emotionen durch regelmäßige oder anhaltende negative Ereignisse führen zu Stress und reduzieren die Erwartung positiver Ereignisse (negativer cognitive Bias). Das Tier ist im Wohlergehen beeinträchtigt. Jüngst zeigte insbesondere die Messung der motorischen Lateralität Potenzial als Indikator für lang anhaltenden und chronischen Stress, denn gestresste Pferde, deren Stresshormonlevel stark ansteigt, zeigen einen zunehmenden Gebrauch der linken Gliedmaßen über einen längeren Zeitraum. Weiterhin zeigen erste Messungen einen Zusammenhang zwischen einer linksseitigen motorischen Lateralität und einer reduzierten Erwartung positiver Ereignisse (negativer cognitive Bias). Zusammen mit der sensorischen Lateralität, die in einer akuten Stressphase ebenso eine Linksverschiebung zeigt und somit als Indikator für Kurzzeitstress gilt, kann eine generelle, vermehrte Linksseitigkeit auch einen Hinweis auf erhöhte Emotionalität und Stressanfälligkeit sein. Eine sich steigernde Linksseitigkeit bedeutet eine präferierte Informationsverarbeitung durch die rechte Gehirnhälfte, die beispielsweise reaktives Verhalten, starke Emotionen und Stressantworten steuert. Es stellte sich jedoch heraus, dass wie bei allen Stressindikatoren auch in der Lateralitätsmessung ein Vergleichswert aus einer vorangegangenen Messung notwendig ist, denn nur Veränderungen zum häufiger werdenden Gebrauch der linken Seite können auf Stress bei Pferden hindeuten und die parallele Erhebung weiterer Parameter, wie zum Beispiel das Verhalten oder Stresshormone, können die Aussage der Lateralität bekräftigen.
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