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Krueger, K. (2017). Perissodactyla Cognition. In J. Vonk, & T. Shackelford (Eds.), Encyclopedia of Animal Cognition and Behavior (pp. 1–10). Cham: Springer International Publishing.
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Wolfrum, V., & Krueger, K. (2017). Pferdegestützte Therapie für Flüchtlingskinder. mup, 2, 65–68.
Abstract: Das Projekt    Viele Flüchtlinge kommen aus Kriegsgebieten zu uns nach Deutschland in der Hoffnung, hier ein neues Leben in Frieden beginnen zu können. Ein Großteil von ihnen hat Schreckliches erlebt und mit diesen Erinnerungen zu kämpfen. Auch ist es nicht einfach, in einem fremden Land mit einer fremden Kultur Fuß zu fassen, sich zu integrieren und neue Freundschaften zu schließen.
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Krueger, K., Marr, I., Dobler, A., & Palme, R. (2019). Preservation of fecal glucocorticoid metabolites and immunoglobulin A through silica gel drying for field studies in horses. conphys, 7(1).
Abstract: Non-invasive methods enable stress evaluation through measuring fecal glucocorticoid metabolites (FGMs), and immunoglobulin A (IgA) in the feces avoiding stressful blood drawing or stressful restraining of animals in the field. However, FGMs and IgA are mostly analysed in freshly frozen samples, which is difficult when fresh samples cannot be frozen immediately or frozen samples cannot be stored or transported. Good results were also derived from air-dried fecal samples, which are hampered by unstable air humidity in the field. These difficulties may be overcome, when drying of samples could be induced with colorless silica gel (SiO2) granules in a secure set-up, such as an air tight tube. We determined the speed of drying 1.5 g of a fresh fecal sample from six horses on air and on silica gel. Furthermore, FGMs and IgA were analysed in differently stored subsamples from 12 horses: in frozen fecal samples, in air- or silica gel-dried samples stored for 1 day and for 7 days, and in wet fecal samples kept in a tube at room temperature for 7 days. FGM levels remained stable in feces dried on air or on silica gel for 7 days, whereas IgA quantities showed a significant loss. Under field conditions, when freezing or transporting the frozen samples is not possible and humidity hampers air drying, drying samples on silica gel in air tight tubes appears to be very helpful and reliable for analysing FGMs.
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Krueger, K. (Ed.). (2012). Proceedings of the 2. International Equine Science Meeting. Wald: Xenophon Publishing.
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Krueger, K. (Ed.). (2015). Proceedings of the 3. International Equine Science Meeting. Proc. 3. Int. Equine. Sci. Mtg. Wald: Xenophon Publishing.
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Krueger, K. (Ed.). (2008). Proceedings of the International Equine Science Meeting 2008. Wald: Xenophon Verlag.
Abstract: Target group: Biologists, Psychologists, Veterinarians and Professionals
Meeting target: Because the last international meeting on Equine Science took place a couple years ago, there is an urgent need for equine scientists to exchange scientific knowledge, coordinate research provide knowledge for practical application, and discus research results among themselves and with professionals who work with horses. Additionally, dialog concerning the coordination of the study “Equitation Science” in Europe is urgently needed. Coordination and cooperation shall arise from the meeting, enrich the research, and advance the application of scientific knowledge for the horses` welfare.
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Voigtlaender-Schnabel, S., Vogel, L., Greiner, B., Wiezorek, S., Schuette, P., Solmsen, E. - H., et al. (2022). Reactions of horses to wildlife and livestock guarding dogs. CDPNews, 24, 49–58.
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Schanz, L., Krueger, K., & Hintze, S. (2019). Sex and Age Don't Matter, but Breed Type Does--Factors Influencing Eye Wrinkle Expression in Horses. Front. Vet. Sci., 6, 154.
Abstract: Identifying valid indicators to assess animals' emotional states is a critical objective of animal welfare science. In horses, eye wrinkles above the eyeball have been shown to be affected by pain and other emotional states. From other species we know that individual characteristics, e.g. age in humans, affect facial wrinkles, but it has not yet been investigated whether eye wrinkle expression in horses is systematically affected by such characteristics. Therefore, the aim of this study was to assess how age, sex, breed type, body condition and coat colour affect the expression and/or the assessment of eye wrinkles in horses. To this end, we adapted the eye wrinkle assessment scale from Hintze et al. (2016) and assessed eye wrinkle expression in pictures taken from the left and the right eye of 181 horses in a presumably neutral situation, using five outcome measures: a qualitative first impression reflecting how worried the horse is perceived by humans, the extent to which the brow is raised, the number of wrinkles, their markedness and the angle between a line through both corners of the eye and the topmost wrinkle. All measures could be assessed highly reliable with respect to intra- and inter-observer agreement. Breed type affected the width of the angle (F2, 114 = 8.20, p < 0.001), with thoroughbreds having the narrowest angle (M = 23.80, SD = 1.60), followed by warmbloods (M = 28.00, SD = 0.60), and coldbloods (M = 31.00, SD = 0.90). None of the other characteristics affected any of the outcome measures, and eye wrinkle expression did not differ between the left and the right eye area (all p-values > 0.05). In conclusion, horses' eye wrinkle expression and its assessment in neutral situations was not systematically affected by the investigated characteristics, except for 'breed type', which accounted for some variation in 'angle'; how much eye wrinkle expression is affected by emotion or perhaps mood needs further investigation and validation.
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Flauger, B., Krueger, K., Gerhards, H., & Möstl, E. (2010). Simplified method to measure glucocorticoid metabolites in faeces of horses. Vet Res Comm, 34(2), 185–195.
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 (3α,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 3α,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.
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Krueger, K. (2008). Social cognition and social learning in horses. In IESM 2008.
Abstract: In comparison to other social animals it appears to be far more difficult to show social learning in horses, although the social background of the animals prompts the prediction that social learning should be verifiable. This demands for a thorough analysis of conditions, context and effects of social learning which might not be as obvious in horses than in other social animals. Moreover, the horse“s social cognition in general, i.e. the processing, encoding, storage, retrieval, and application of social information, needs to be examined. In previous studies we addressed the horse”s perception of it“s social environment. Our results indicate that domestic horses are not only capable of distinguishing between familiar and unfamiliar horses but also of recognizing the social status of familiar horses relative to their own. Furthermore, they extract information from observing interactions between a familiar horse and a human experimenter, and adjust their behaviour according to the observed horse”s reaction and relative dominance status when they are themselves later confronted with the experimenter in a similar situation. Additionally, we showed in pilot experiments that horses paid more attention to the gaze of dominant horses from their own social group than to that of unknown or subordinate horses. In another study we suggested that horses of both sexes are capable of determining the social affiliation, the sex and, for their own group members, the identity of individuals, by sniffing their faeces. Hence, social affiliation and dominance relationships seemed to have a major influence on the horses` motivation to pay attention to their conspecifics. In the future we will take another step towards linking the horse“s social cognitive capacities with its social ecology, social structure, and individuality. In the context of comparative cognition research on the socially complex primates, or on a range of carnivores such as corvids, canids or dolphins, horses are particularly interesting, because they are highly social, but do not rely on social hunting or cooperative raising of offspring. Also foraging is simple for horses, predator avoidance is demanding and this may be the main reason for the horse”s complex social lives and their choice of learning tactics. Hence, we will investigate the horse"s investigative behaviour towards neutral, fear-eliciting and food related novel objects. We propose that, as in other species, sociality and distinct personalities are key features for the understanding of cognitive capacities and the choice of learning strategies.
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