Abstract: The ability of horses to learn and remember new tasks is fundamentally important for their use by humans. Fearfulness may, however, interfere with learning, because stimuli in the environment can overshadow signals from the rider or handler. In addition, prolonged high levels of stress hormones can affect neurons within the hippocampus; a brain region central to learning and memory. In a series of experiments, we aimed to investigate the link between performance in two learning tests, the baseline level of stress hormones, measured as faecal cortisol metabolites (FCM), fearfulness, and social rank. Twenty-five geldings (2 or 3 years old) pastured in one group were included in the study. The learning tests were performed by professional trainers and included a number of predefined stages during which the horses were gradually trained to perform exercises, using either negative (NR) or positive reinforcement (PR). Each of the learning tests lasted 3 days; 7min/horse/day. The NR test was repeated in a novel environment. Performance, measured as final stage in the training programme, and heart rate (HR) were recorded. Faeces were collected on four separate days where the horses had been undisturbed at pasture for 48h. Social rank was determined through observations of social interactions during feeding. The fear test was a novel object test during which behaviour and HR were recorded. Performance in the NR and PR learning tests did not correlate. In the NR test, there was a significant, negative correlation between performance and HR in the novel environment (rS=-0.66, P<0.001, i.e. nervous horses had reduced performance), whereas there was no such correlation in the home environment (both NR and PR). Behavioural reactions in the fear test correlated significantly with performance in the NR test in the novel environment (e.g. object alertness and final stage: rS=-0.43, P=0.04), suggesting that performance under unfamiliar, stressful conditions may be predicted by behavioural responses in a fear test. There was a negative correlation between social rank and baseline stress hormones (rS=-0.43, P=0.04), i.e. high rank corresponded to low FCM concentrations, whereas neither rank nor FCM correlated with fearfulness or learning performance. We conclude that performance under stressful conditions is affected by activation of the sympathetic nervous system during training and related to behavioural responses in a standardised fear test. Learning performance in the home environment, however, appears unrelated to fearfulness, social rank and baseline FCM levels.

Abstract: In dieser Untersuchung sollte überprüft werden, ob die für die Stressmessung beim Menschen angewandte „Chronopsychobiologische Regulationsdiagnostik“ (CRD) mithilfe des smardwatch®-Messsystems auch beim Pferd psychische Belastungssituationen aussagekräftig widerspiegelt. Menschen können anhand variierender physiologischer und ethologischer Reaktionen auf Stressoren aus der Umwelt in Stresstypen eingeteilt werden. Auch Pferde reagieren in identischen Situationen ganz unterschiedlich. Es stellte sich daher die Frage, ob Pferde ebenfalls bestimmten Stresstypen zugeordnet werden können.
Mit 26 dreijährigen Hengsten des Landgestüts Celle wurde ein Verhaltenstest durchgeführt. Auf der Grundlage wissenschaftlich dokumentierter und modifizierter Testsituationen (Open-Field-Test, Novel-Object-Test, Startling-Test Objekt/Geräusch, Mensch-Pferd-Interaktion, Ressourcenkontrolle) wurde das Erkundungs- und Fluchtverhalten untersucht (Goslar 2011). Während dieser Belastungssituationen wurden mit dem smardwatch®-Messgerät die elektrophysiologischen Parameter Hautwiderstand, Hautpotential und Muskelaktivität erfasst. Durch eine Zeitreihenmessung dieser physiologischen Parameter konnten die Reaktionen des übergeordneten Reglers (vegetatives Nervensystem) dargestellt werden. Der Hautwiderstand spiegelt die vegetativ-emotionalen Reaktionen wider, das Hautpotential die vegetativ-nervalen und somit laut Balzer (2009) die kognitiven Verarbeitungsweisen, und durch das Elektromyogramm werden die typischen muskulär-motorischen Reaktionen aufgezeichnet. Die vorliegenden Datenzeitreihen wurden mit Hilfe einer biorhythmometrischen Zeitreihenanalyse nach Balzer und Hecht (Hecht 2001, Balzer 2009) ausgewertet. Als Ergebnis wurden chronobiologische Regulationszustände definiert, die dann gemäß dem „Periodischen System der Regulationszustände“ (PSR) (Balzer 2000) eine Beurteilung der psychischen Belastungssituation erlauben. Zur Bestimmung von Stresstypen wurde die Untersuchung nach dem Reiz-Reaktions-Prinzip in drei Phasen unterteilt: Ruhephase, Stressreizphase und Stressverarbeitungsphase. Der Verhaltenstest wurde nach einer Woche zur gleichen Tageszeit mit jedem Hengst einmal wiederholt. Als physiologische Vergleichsparameter wurden vor, während und nach der Belastung insgesamt zehn Speichelproben zur Cortisolbestimmung entnommen.
Die smardwatch®-Messtechnik ist prinzipiell geeignet die physiologischen Parameter Hautwiderstand, Hautpotential und Muskelaktivität auf der Haut des Pferdes aufzunehmen. Durch die biorhythmometrische Zeitreihenanalyse konnten chronobiologische Regulationszustände definiert werden.
Der Verhaltenstest führte bei allen Pferden zu einem signifikanten Anstieg der Cortisolwerte. Ein ebenfalls statistisch gesicherter Unterschied der aktivierten Cortisolwerte zwischen der ersten und zweiten Testwoche zeigt eine geringere Stressreaktion und weist auf einen Lerneffekt der Pferde hin:
Entsprechend der relativen Instabilitäten der Regulation der Körperfunktionen in Messphase 2 und 3 konnten die Pferde in vier Stressregulationstypen (nach Balzer u. Hecht 1996) eingeteilt werden: Stressbeherrscher, -bewältiger und kompensierer sowie Stressnichtbewältiger.
Anhand der Aktivierung von Sympathikus und Parasympathikus konnten zusätzlich vier verschiedene Vegetative Stresstypen unterschieden werden: Sympathikotoniker, Amphotoniker, Indifferenter Typ und Vagotoniker.
Die Cortisolreaktion der Hengste war individuell sehr unterschiedlich. Um die maximalen Anstiege vergleichen zu können, wurde der Trend der jeweiligen Cortisolverlaufskurve bestimmt. Anhand der Trend-korrigierten Cortisolkurven konnten einerseits die relativen Maxima der Cortisolreaktion besser verglichen werden, anderseits konnten die Pferde mittels des unterschiedlichen Trendes in drei Cortisolverlaufsgruppen eingeteilt werden: Tendenz fallend, gleichbleibend oder steigend.
Ein statistischer Nachweis für eine Abhängigkeit zwischen den verschiedenen Stresstypenklassifizierungen konnte anhand der geringen Stichprobenzahl nicht erbracht werden. Jedoch lassen sich Pferde, wie Menschen, unterschiedlichen Stresstypen zuordnen. Schwierig bleibt aber die objektive Beurteilung von Befindlichkeiten, da Empfindungen und Gefühle nur subjektiv wahrnehmbare Qualitäten sind, die von einer Reihe innerer und äußerer Faktoren abhängen. Die Verhaltenszuordnung emotionaler Zustände durch die „Chronopsychobiologische Regulationsdiagnostik“ (CRD) kann nicht ohne die Basis weiterer vergleichender Studien vom Mensch auf das Pferd übertragen werden.
Die CRD-Methode könnte allerdings einen interdisziplinären Ansatz ermöglichen und zukünftig neben den klassischen deskriptiven Verhaltensbeobachtungen bei der Beurteilung von Haltungs- und Umgangssituationen von Tieren wertvolle Aufschlüsse über die Fähigkeit zur Stressbewältigung und deren Konsequenzen für das Wohlbefinden der Tiere geben.
In this study we examined, whether the “Chronopsychobiological regulation diagnosis” (CRD) with the smardwatch®-system which is used to assess specific strain in humans, is also able to reflect convincingly specific strain in horses. Humans can be categorized into so-called stress types, because they react differently in physiology and behaviour to environmental stimuli. Concerning horses, it is also known that individuals react differently in identical situations. The question to be answered is, if it is possible to categorize horses into certain stress types as well.
We carried out a behavioural test with 26 three-year-old stallions of the State Stud of Celle, involving different test situations. On the basis of test situations, well known in scientific literature including slight modifications (open-field-test, novel-object-test, startling-test object/sound, human-horse-interaction, resource control) the explorative and flight behaviour of horses were examined (Goslar 2011). During these situations of strain the system smardwatch® measured the electro-physiological parameters skin resistance, skin potential and muscle activity. With time series analyses of these physiological parameters the reactions of the vegetative nervous system as superior control could be shown. The skin resistance reflects the vegetative-emotional, the skin potential the vegetative-nervous hence according to Balzer (2009) cognitive reactions and the electromyogram shows the motorized reactions. The time series of measured data was analyzed using the biorhythmometrical time series analysis of Balzer and Hecht (Hecht 2001, Balzer 2009). As a result of this, typical states of chronobiological regulation were defined. With the help of the “periodic system of regulatory states” (PSR) (Balzer 2000) these led to a classification of mental stress situations. To categorize horses into stress types the study was devided into three phases according to the stimulus-response principle: phase 1 (relaxing), phase 2 (situation of strain) and phase 3 (stimulus processing phase). The behavioural test was repeated once with each stallion exactly one week later. In addition ten samples of saliva were taken before, during and after the situations of strain from which we determined the cortisol concentration to be compared with the chronopsychobiological parameters.
The smardwatch®-measurement technology is fundamentally suitable to measure the physiological parameters skin resistance, skin potential and electrical muscle activity of horses. Using the biorhythmometrical time series analysis, chronobiological regulatory states could be defined for horses as well.
For each horse the cortisol value increased significantly during the behavioural test. A remarkable difference of the cortisol values assessed in the first and second test, indicates a learning effect: The behavioural test led to a significantly lower stress reaction in the second week.
Depending on the proportions of unstable regulation processes during and after the situations of strain, four types of regulation (Balzer u. Hecht 1996) can be defined: the Control-, Cope-, Compensate- and Non-cope-type.
Using the activation of the sympathetic and parasympathetic nervous system four vegetative stress types could be determined: Sympathicotonic, Amphotonic, Indifferent Type and Vagotonic.
The stress reaction of the stallions in terms of cortisol level was quite individual. To compare the maximum increase the trend of each cortisol trajectory was analyzed. On the one hand correcting for the trend allowed a comparison of relative maxima, on the other hand the horses could be categorized into groups, according to the evolution of their cortisol level (cortisol progression groups): Tendency falling, stable or rising.
The number of samples was not considered to be sufficient in order to statistically assess some dependence among the different classifications of stress types. But to our point of view horses can be assigned to different stress types like humans. But it’s still difficult to judge the emotions of animals, because emotions are subjectively perceptible qualities dependent on many internal and external factors. The assignment of emotional behaviour to the chronopsychobiological regulation diagnosis (CRD) can’t be transferred from human to horse without further studies.
However, the CRD method could enable an interdisciplinary approach. Besides classic descriptive observations of behavior, the CRD could give further information about the coping capacity and the consequences for animal welfare in the assessment of stressful situations.

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.

Abstract: Even though the term “stress” is widely used, a precise definition is notoriously difficult. Notwithstanding this difficulty, stress continues to be an important concept in biology because it attempts to describe how animals cope with environmental change under emergency conditions. Without a precise definition, however, it becomes nearly impossible to make testable a priori predictions about how physiological and hormonal systems will respond to emergency conditions and what the ultimate impact on the animal will be. The reactive scope model is a recent attempt to formulate testable predictions. This model provides a physiological basis to explain why corticosterone negative feedback, but not baseline corticosterone concentrations, corticosterone responses to acute stress, or the interrenal capacity to secrete corticosterone, is correlated with survival during famine conditions in Galápagos marine iguanas. Reactive scope thus provides a foundation for interpreting and predicting physiological stress responses.

Abstract: Glucocorticoids or their metabolites can be measured in several body fluids or excreta, including plasma, saliva, urine and faeces. In recent years the measurement of glucocorticoid metabolites (GCMs) in faeces has gained increasing attention, because of its suitability for wild populations. In horses, however, the group-specific enzyme immunoassay described so far has a limited racticability due to its complex extraction procedure. Therefore, we tested the applicability of
other enzyme immunoassays for glucocorticoid metabolites. The present study clearly proved that an enzyme immunoassay (EIA) for 11-oxoetiocholanolone using 11-oxoetiocholanolone-17-CMO: BSA (3&#945;,11-oxo-A EIA) as antigen showed high amounts of immunoreactive substances. Therefore it was possible to use just a small amount of the supernatant of a methanolic suspension of faeces. The results
correlated well with the already described method for measuring GCMs in horse faeces, i.e. analysing the samples with an EIA after a two step clean up procedure of the samples (Merl et al. 2000). In addition, the 3&#945;,11-oxo-A EIA has the advantage of providing a bigger difference between baseline values and peak values after ACTH stimulation. The new assay increased the accuracy of the test,
lowered the expenses per sample, and storing samples at room temperature after collection was less critical than with other assays investigated in our study. This is a big advantage both in the field of wildlife management of equids and in the field of equestrian sports and it shows the importance of choosing an assay which is in good accordance with the metabolites excreted in a given species.