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Beery, A. K., & Kaufer, D. (2015). Stress, social behavior, and resilience: Insights from rodents. Neurobiol. Stress, 1(Stress Resilience), 116–127.
Abstract: The neurobiology of stress and the neurobiology of social behavior are deeply intertwined. The social environment interacts with stress on almost every front: social interactions can be potent stressors; they can buffer the response to an external stressor; and social behavior often changes in response to stressful life experience. This review explores mechanistic and behavioral links between stress, anxiety, resilience, and social behavior in rodents, with particular attention to different social contexts. We consider variation between several different rodent species and make connections to research on humans and non-human primates.
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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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McLean, A. N., & Christensen, J. W. (2017). The application of learning theory in horse training. Appl. Anim. Behav. Sci., 190, 18–27.
Abstract: The millennia-old practices of horse training markedly predate and thus were isolated from the mid-twentieth century revelation of animal learning processes. From this standpoint, the progress made in the application and understanding of learning theory in horse training is reviewed including a discussion of how learning processes are employed or otherwise under-utilised in training. This review describes the process of habituation and the most commonly applied desensitisation techniques (systematic desensitisation, counter-conditioning, overshadowing, response prevention) and propose two additional techniques (approach conditioning and stimulus blending). The salience of different types of cues, the interaction of operant and classical conditioning and the impact of stress are also discussed. This paper also exposes the inflexibility and occasional inadequacy of the terminology of learning theory when translated from the research laboratory situation to the practical setting in horse training. While learning theory provides a rich toolbox for riders and trainers, the training process is subject to the simultaneous use of multiple learning processes. In addition, learning/behavioural outcomes and trained responses are not just the result of simple stimulus-response based interactions but are further shaped by arousal, affective and attachment states. More research is needed in these areas. For the field of equitation science to progress and to improve clarity and use of learning processes, changes in nomenclature are required. In particular, the use of the terms 'positive' and 'negative' as descriptive labels in both reinforcement and punishment modalities are unacceptably misleading for everyday use. These labels inhibit the understanding and recognition of the learning processes that these terms supposedly represent, yet the learning processes they describe are vital for horse riders, handlers and trainers to understand. We therefore propose that these labels should be re-labelled more appropriately as 'addition' or 'subtraction' reinforcement/punishment. This would enlighten trainers on the correct application of learning theory, and safety and welfare benefits for people and horses would follow. Finally it is also proposed that the term 'conflict theory' be taken up in equitation science to facilitate diagnosis of training-related behaviour disorders and thus enable the emergence of improved training practices. The optimal use of learning theory should be established as a fundamental principle in equestrian education.
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König v. Borstel, U., Visser, E. K., & Hall, C. (2017). Indicators of stress in equitation. Appl. Anim. Behav. Sci., 190, 43–56.
Abstract: Abstract Stress is a generic concept describing the body's reaction to external stimuli, including both physiological and psychological factors. Therefore, by definition, the assessment of psychological stress in the exercising horse encompasses the problem of teasing apart the psychological and physiological factors both of which result in stress responses. The present study reviews the existing literature on various measures of stress taken specifically in the context of equitation science. Particular attention has been paid to short-term effects, and commonly used measurements of short-term stress include heart rate, a number of heart rate variability parameters, blood or saliva cortisol levels, eye temperature, and various behaviour parameters including in particular behaviour patterns presumably indicative of conflict with the rider's/trainer's aids. Inspection of the individual studies' results revealed that disagreement between these different measures of stress is commonplace. For physiological parameters, the largest proportion of agreement (i.e. both parameters simultaneously indicated either higher, insignificant or lower stress compared to a control treatment) was found for heart rate and heart rate variability parameters, while generally limited agreement was found for cortisol. It appears that cortisol levels may not be particularly useful for assessing/assessment of the valence of a situation in the exercising horse as cortisol levels are predominantly linked to activation and exercise levels. Although heart rate variability parameters reflect in theory more closely sympathovagal balance compared to cortisol levels, great care has to be taken regarding the use of appropriate time-frames, appropriate raw data correction methods as well as the use of appropriate equipment. In spite of its wide-spread and apparently successful use, popular equipment may in fact not be accurate enough under field conditions. Eye temperature is another promising parameter for assessment of psychological stress, but the technique is likewise susceptible to application errors. Given the high susceptibility of physiological parameters to errors at various experimental stages, behavioural rather than physiological parameters may in fact provide more accurate measures of valence when conducting experiments in the exercising horse. Behavioural parameters that appear to be particularly practical in assessing stress in ridden horses' behaviour are associated with frequencies of behaviour indicative of conflict. However, while increased frequencies of are a good indicator of stress, the absence of conflict behaviour does not provide proof of the absence of stress due to the possible occurrence of conditions such as Learned Helplessness. In future studies, the above issues should be taken into consideration when designing experiments to assess psychological stress in ridden horses.
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Innes, L., & McBride, S. (2008). Negative versus positive reinforcement: An evaluation of training strategies for rehabilitated horses. Appl. Anim. Behav. Sci., 112(3–4), 357–368.
Abstract: Rescued equids are often exposed to rehabilitation and training (or retraining) programmes to improve their physical and psychological well-being as well as to facilitate the re-homing process. Training uses either positive or negative reinforcement learning procedures and it is considered here that, there may be welfare implications associated with using the latter technique as it has the potential to overlay acute stress on animals with a chronic stress life history. The aim of this study, therefore, was to compare these training strategies (negative versus positive reinforcement) on equine behaviour and physiology as the first step in establishing an optimal rehabilitation approach (from a welfare perspective) for equids that have been subjected to chronic stress in the form of long-term neglect/cruelty. Over a 7-week period, 16 ponies (aged 6–18 months) were trained using either positive (‘positive’) (n = 8) or negative reinforcement (‘negative’) (n = 8) techniques to lead in hand, stand to be groomed, traverse an obstacle course and load into a trailer. Heart rate was measured (5 s intervals) on days 1 and 4 of each training week, ‘Pre’- (1 h), ‘During’ (0.5 h) and ‘Post’- (1 h) training session. Ethograms (10.00–20.00 h) outside of the training period were also compiled twice weekly. In addition, weekly arena tests (as a measure of reactivity) were also performed 1 week before and during the 7 weeks of training. Results showed significant differences between the two training schedules for some measures during the latter stages of the trial and suggested that animals trained under a positive reinforcement schedule were more motivated to participate in the training sessions and exhibited more exploratory or ‘trial and error’ type behaviours in novel situations/environments. In this context, the incorporation of positive reinforcement schedules within a rehabilitation programme may be of benefit to the animal from a welfare perspective.
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Casella, S., Fazio, F., Giannetto, C., Giudice, E., & Piccione, G. (2012). Influence of transportation on serum concentrations of acute phase proteins in horse. Research in Veterinary Science, 93(2), 914–917.
Abstract: The modifications of Haptoglobin (Hp), Serum Amyloid A (SAA), Fibrinogen (Fbg) and White Blood Cells (WBCs) were evaluated in 15 Saddle Italian horses. Ten horses were transported covering a distance of about 320 km within 4 h with an average speed of 80 km/h (experimental group) and five horses were not subject to transportation (control group). Blood was collected via jugular venipuncture before the transportation (T0), immediately after the transportation (T1), 12 (T12), 24 (T24) and 48 (T48) hours after the transportation in experimental group and at the same time point in control group. For each parameter statistical analysis of different groups and sampling time was performed using a two-way analysis of covariance, with the data before the transportation (T0) as the covariate, by the GLM procedure of SAS. For all parameters the interaction (Group × Time) was tested and it was resulted no significant. The application of statistical analysis showed significant differences between the control group and horses subjected to transportation (P < 0.01), and the influence of sampling time (P < 0.05) on Hp, SAA and WBCs. These modifications appeared to be innovative showing that equine Hp, generally considered as moderate acute phase protein, increases more rapidly than the SAA after transportation-induced stress.
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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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Carlsson, H. - E., Lyberg, K., Royo, F., & Hau, J. (2007). Quantification of stress sensitive markers in single fecal samples do not accurately predict excretion of these in the pig. Research in Veterinary Science, 82(3), 423–428.
Abstract: All feces produced during 24 h were collected from five pigs and cortisol and immunoreactive cortisol metabolites (CICM), and IgA were quantified. Within pigs, the concentrations of CICM and IgA varied extensively between random samples obtained from a single fecal dropping, and deviated in most cases significantly from the true concentration measured in total fecal output (CV 6.7–130%). The CICM and IgA contents varied considerably (CV 8.1–114%) within and between individual fecal droppings from the same pig compared to the total fecal excretion. In conclusion, single random samples could not be used to reliably quantify the total fecal concentration or excretion of CICM or IgA in pigs. Analyses of all feces collected during shorter periods than 24 h did not provide an accurate estimate of the daily excretion of CICM. Thus, the concentration of stress sensitive molecules in random single fecal samples as an indicator of animal welfare should be interpreted with prudence.
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Christensen, J. W., Beekmans, M., van Dalum, M., & VanDierendonck, M. (2014). Effects of hyperflexion on acute stress responses in ridden dressage horses. Physiol. Behav., 128, 39–45.
Abstract: The effects of hyperflexion on the welfare of dressage horses have been debated. This study aimed to investigate acute stress responses of dressage horses ridden in three different Head-and-Neck-positions (HNPs). Fifteen dressage horses were ridden by their usual rider in a standardised 10-min dressage programme in either the competition frame (CF), hyperflexion (“Low-Deep-and-Round”; LDR) or a looser frame (LF) in a balanced order on three separate test days. Heart rate (HR), heart rate variability parameters (HRV), behaviour and rein tension were recorded during the test. Salivary cortisol concentrations were measured 60min before and 0, 5, 15 and 30min after the test. Rein tension was significantly lower in LF and did not differ between CF and LDR; however approx. 15% of recordings in CF and LDR were above the sensor detection limit of 5kg. The horses had significantly higher cortisol concentrations directly after LDR compared to LF. In addition, the horses showed more distinctive head movements, including head waving, during LDR. There were no significant treatment effects on HR and HRV. In conclusion, the results indicate that LDR may be more stressful to these horses during riding.
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Romero, L. M., Dickens, M. J., & Cyr, N. E. (2009). The reactive scope model — A new model integrating homeostasis, allostasis, and stress. Horm. Behav., 55(3), 375–389.
Abstract: Allostasis, the concept of maintaining stability through change, has been proposed as a term and a model to replace the ambiguous term of stress, the concept of adequately or inadequately coping with threatening or unpredictable environmental stimuli. However, both the term allostasis and its underlying model have generated criticism. Here we propose the Reactive Scope Model, an alternate graphical model that builds on the strengths of allostasis and traditional concepts of stress yet addresses many of the criticisms. The basic model proposes divergent effects in four ranges for the concentrations or levels of various physiological mediators involved in responding to stress. (1) Predictive Homeostasis is the range encompassing circadian and seasonal variation — the concentrations/levels needed to respond to predictable environmental changes. (2) Reactive Homeostasis is the range of the mediator needed to respond to unpredictable or threatening environmental changes. Together, Predictive and Reactive Homeostasis comprise the normal reactive scope of the mediator for that individual. Concentrations/levels above the Reactive Homeostasis range is (3) Homeostatic Overload, and concentrations/levels below the Predictive Homeostasis range is (4) Homeostatic Failure. These two ranges represent concentrations/levels with pathological effects and are not compatible with long-term (Homeostatic Overload) or short-term (Homeostatic Failure) health. Wear and tear is the concept that there is a cost to maintaining physiological systems in the Reactive Homeostasis range, so that over time these systems gradually lose their ability to counteract threatening and unpredictable stimuli. Wear and tear can be modeled by a decrease in the threshold between Reactive Homeostasis and Homeostatic Overload, i.e. a decrease in reactive scope. This basic model can then be modified by altering the threshold between Reactive Homeostasis and Homeostatic Overload to help understand how an individual's response to environmental stressors can differ depending upon factors such as prior stressors, dominance status, and early life experience. We illustrate the benefits of the Reactive Scope Model and contrast it with the traditional model and with allostasis in the context of chronic malnutrition, changes in social status, and changes in stress responses due to early life experiences. The Reactive Scope Model, as an extension of allostasis, should be useful to both biomedical researchers studying laboratory animals and humans, as well as ecologists studying stress in free-living animals.
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