Hedberg, Y., Dalin, A. - M., Ohagen, P., Holm, K. R., & Kindahl, H. (2005). Effect of oestrous-cycle stage on the response of mares in a novel object test and isolation test. Reprod Domest Anim, 40(5), 480–488.
Abstract: In various species, sex, hormonal treatments and oestrous-cycle stage have been shown to affect the animal's response in behavioural tests. Few such studies have been performed in the horse. The main aim of the present study was to investigate whether oestrous-cycle stage affects mares' response to a novel object test and isolation test and, in part, to study whether mares, assumed to suffer from oestrous-related behavioural problems, respond differently in these tests when compared with controls. Twelve mares were tested twice, in oestrus and dioestrus, in a crossover design. Seven behavioural and two heart rate variables were measured for the novel object test and two heart rate variables for the isolation test. Oestrous-cycle stage and whether a mare was classified as a 'problem' mare did not affect the mare's response. However, test order, i.e. the cycle stage a mare was tested in first, affected its reaction. This effect could partly be explained by significant differences between test occasions 1 and 2 in three behavioural variables and one heart rate variable (p < 0.05) in the novel object test. The mares explored the novel object more and had a higher mean heart rate in the first test. Exploring the novel object more could largely be attributed to those mares tested in dioestrus first, perhaps indicating that the mares in oestrus were less receptive to the novel object. The reason for the differences between test occasions could be an effect of learning or habituation.
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Siegel, H. S. (1987). Effects of behavioural and physical stressors on immune responses. London: Martinus Nijhoff.
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Mertens, P. A., & Unshelm, J. (1996). Effects of Group and Individual Housing on the Behavior of Kennelled Dogs in Animal Shelters. Anthrozoos: A Multidisciplinary Journal of The Interactions of People & Animals, 9, 40–51.
Abstract: To emphasize the effects of group- and single housing of kennelled dogs, the behavior of 211 dogs in two German animal shelters was tested and observed. After being placed, 197 of the dogs' new owners were interviewed.
Although 51% of the German animal shelters already keep dogs in groups, there is strong prejudice against group housing because of the fear of fights. This study demonstrates that this apprehension is unfounded. Ninety-one percent of the social confrontations between dogs housed together were settled by the use of behavioral rituals. Keeping dogs in groups, furthermore, leads to a significant reduction in noise emission (p<.001). Group housing fulfills the dog's need for social interaction and the need to move. Dogs that were housed in groups displayed a closer human-animal relationship (80%) than those that had been kept individually (43%). A high percentage of individually housed dogs suffered from behavioral problems (31%) and 10% developed stereotypes. The percentage of behaviorally disturbed dogs observed in group housing was 11%, and stereotyped forms of behavior did not occur. Dogs who had been kept in groups were, on average, placed within 10 days, and were returned to the animal shelter less often (9%) compared to those housed individually (25%). Dogs that were housed separately needed an average of 17 days to be placed. Even after being placed, there is a correlation between the animal shelter's type of housing and the dog's behavior. Within four weeks after picking up their pet, 88% of the owners of dogs that had been housed individually complained of problems compared to the owners of the dogs that had been kept in groups, 53% of whom were completely satisfied with the adoption.
Despite the fact that these results might be influenced by the small number of shelters examined, the study leads to the conclusion that keeping dogs in groups is a suitable alternative for dog housing in animal shelters and, for the animals' welfare, is preferable to individual housing.
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Villani, M., Cairoli, F., Kindahl, H., Galeati, G., Faustini, M., Carluccio, A., et al. (2006). Effects of mating on plasma concentrations of testosterone, cortisol, oestrone sulphate and 15-ketodihydro-PGF2alpha in stallions. Reprod Domest Anim, 41(6), 544–548.
Abstract: Very little information is available regarding the physiological mechanisms involved in the normal sexual activity in the stallion and, in particular, the endocrine control of reproduction is still not clearly understood. This experiment was designed to determine the short-term effect of sexual stimulation on plasma concentrations of testosterone, cortisol, oestrone sulphate and 15-ketodihydro-PGF(2alpha) in stallions. Semen samples were collected from 10 lighthorse stallions of proven fertility using a Missouri model artificial vagina. At the same time, blood samples were collected from the jugular vein with heparinized tubes, 20 and 10 min before oestrous mare exposure, at exposure and 10, 20, 30 min after dismounting. Testosterone concentrations showed a sharp rise 10 min after mating (p < 0.001), reached a plateau, and then showed a further increase 30 min after mating (p < 0.001). Cortisol concentrations increased 10 min after mating (p < 0.001) and remained at high levels in the subsequent samples taken. A peak of oestrone sulphate was observed 10 min after mating (p < 0.001). 15-Ketodihydro-PGF(2alpha) concentrations decreased rapidly at the moment of the exposure of the stallions to an oestrous mare (p < 0.05), returned to pre-mating concentrations and then decreased again 30 min after mating (p < 0.05).
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Marr, I., Farmer, K., & Krueger, K. (2018). Evidence for Right-Sided Horses Being More Optimistic than Left-Sided Horses. Animals, 8(12), 219.
Abstract: An individual's positive or negative perspective when judging an ambiguous stimulus (cognitive bias) can be helpful when assessing animal welfare. Emotionality, as expressed in approach or withdrawal behaviour, is linked to brain asymmetry. The predisposition to process information in the left or right brain hemisphere is displayed in motor laterality. The quality of the information being processed is indicated by the sensory laterality. Consequently, it would be quicker and more repeatable to use motor or sensory laterality to evaluate cognitive bias than to perform the conventional judgment bias test. Therefore, the relationship between cognitive bias and motor or sensory laterality was tested. The horses (n = 17) were trained in a discrimination task involving a box that was placed in either a “positive” or “negative” location. To test for cognitive bias, the box was then placed in the middle, between the trained positive and negative location, in an ambiguous location, and the latency to approach the box was evaluated. Results indicated that horses that were more likely to use the right forelimb when moving off from a standing position were more likely to approach the ambiguous box with a shorter latency (generalized linear mixed model, p < 0.01), and therefore displayed a positive cognitive bias (optimistic).
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Holekamp, K. E., Boydston, E.E, & Smale, L. (2000). Group Travel in Social Carnivores (S. Boinski, & P. A. Garber, Eds.). Chicago: Chicago University Press.
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Wingfield, J. C.,, & Ramenofsky, M. (1999). Hormones and the behavioral ecology of stress. In P. H. M. Balm (Ed.), Stress physiology in animals. (pp. 1–51). Sheffield, United Kingdom: Sheffield Academic Press.
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Bökönyi, S. (1984). Horse. In Manson (Ed.), Evolution of domesticated animals (Vol. 18, pp. 162–173). Hoboken, NJ: John Wiley & Sons.
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Esch, L., Wöhr, C., Erhard, M., & Krueger, K. (2019). Horses� (Equus Caballus) Laterality, Stress Hormones, and Task Related Behavior in Innovative Problem-Solving. Animals, 9(5), 265.
Abstract: Domesticated horses are constantly confronted with novel tasks. A recent study on anecdotal data indicates that some are innovative in dealing with such tasks. However, innovative behavior in horses has not previously been investigated under experimental conditions. In this study, we investigated whether 16 horses found an innovative solution when confronted with a novel feeder. Moreover, we investigated whether innovative behavior in horses may be affected by individual aspects such as: age, sex, size, motor and sensory laterality, fecal stress hormone concentrations (GCMs), and task-related behavior. Our study revealed evidence for 25% of the horses being capable of innovative problem solving for operating a novel feeder. Innovative horses of the present study were active, tenacious, and may be considered to have a higher inhibitory control, which was revealed by their task related behavior. Furthermore, they appeared to be emotional, reflected by high baseline GCM concentrations and a left sensory and motor laterality. These findings may contribute to the understanding of horses� cognitive capacities to deal with their environment and calls for enriched environments in sports and leisure horse management.
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Byrne, R. W. (2000). How monkeys find their way: leadership, coordination, and cognitive maps of African baboons. In S. Boinski, & P. A. Garber (Eds.), On the Move: How and Why Animals Travel in Groups (pp. 491–518). Chicago: Chicago University Press.
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