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Westerduin, F. E., Lankveld, D. P. K., van der Velden, M. A., Back, W., & Sloet van Oldruitenborgh-Oosterbaan, M. M. (2003). [Splenectomy in a dressage pony: end of sports career?]. Tijdschr Diergeneeskd, 128(13), 406–411.
Abstract: A 14-year-old Arabian cross-bred gelding was referred to the University Clinic because of mild, recurrent signs of colic for 5 days. The pony showed icteric mucous membranes, haemolytic blood, and dark coloured urine. Internal examination did not give a clear diagnosis. Unidentified intra-abdominal strands were found and haemorrhagic abdominocentesis led to the decision to perform an exploratory laparatomy. An extremely enlarged spleen was the sole finding. A splenal biopsy sample was taken and surgery was completed. The pony remained colicky, so the spleen was examined by ultrasonography. After this examination, the tentative diagnosis 'tumour of the spleen' was made and splenectomy was performed. Pathological examination of the spleen revealed splenomegaly caused by infarctions of unknown origin. Eight weeks after surgery, the pony started again in dressage competition. Six months after splenectomy, the pony won the provincial dressage competition.
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Vollmerhaus, B., Roos, H., Gerhards, H., & Knospe, C. (2003). [Phylogeny, form and function of canine teeth in the horse]. Anat Histol Embryol, 32(4), 212–217.
Abstract: The canine teeth of the horse developed phylogenically from the simple, pointed, short-rooted tooth form of the leaf eating, in pairs living, Eocene horse Hyracotherium and served up to the Oligocene as a means of defense (self preservation). In the Miocene the living conditions of the Merychippus changed and they took to eating grass and adopted as a new behavior the life in a herd. The canine teeth possibly played an important role in fights for social ranking; they changed from a crown form to knife-like shape. In the Pliohippus the canine tooth usually remained in male horses and since the Pliocene, it contributed to the fights between stallions, to ensure that the offspring only came from the strongest animals (preservation of the species). Form and construction of the canine tooth are described and discussed in detail under the above mentioned phylogenic and ethologic aspects.
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Sondergaard, E., & Halekoh, U. (2003). Young horses' reactions to humans in relation to handling and social environment. Appl. Anim. Behav. Sci., 84(4), 265–280.
Abstract: Forty Danish warmblood colts in two replicates were used to investigate the effect of housing and handling in the rearing period on the reactions to humans. The horses entered the experiment after weaning and were housed either individually (n=16) or in groups of three (n=24). Half of the horses from each housing group were handled three times per week for a period of 10 min. Approach tests were performed in the home environment when the horses were 6, 9, 12, 18, 21, and 24 months old, and an Arena and Human Encounter test was performed in a novel environment when the horses were 12 and 24 months old, respectively. In the home environment, single-housed horses approached sooner and were more easily approached by a human than group-housed horses where no effect of handling was observed. Horses approached sooner and were more easily approached with increasing age. In the Arena and Human Encounter test, single-housed horses expressed less restless behaviour, more explorative behaviour, and less vocalisation than group-housed horses. Handled horses showed lower increase in heart rate during the test than non-handled horses. There was no difference between the number of times single or group-housed horses touched an unfamiliar person in the Arena and Human Encounter test but handled horses approached sooner than non-handled horses. It is concluded that the social environment affected the way horses reacted to humans when tested in the home environment but not in a novel environment. In contrast, handling affected the reactions to humans when tested in the novel environment but not in the home environment. However, handled horses also reacted less to the novel environment in general, thus indicating that handling is a mean of avoiding potential dangerous situations.
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Komar, N. (2003). West Nile virus: epidemiology and ecology in North America. Adv Virus Res, 61, 185–234.
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Valero, N. (2003). West Nile virus: a new challenge? Invest Clin, 44(3), 175–177.
Abstract: West Nile Virus (WNV), a member of the family Flaviviridae, was first isolated in 1937. Since the original isolation of the WNV outbreaks have occurred with increase in frequency of cases in humans and horses, apparent increase in severe human disease and high avian death rates. In 1999, 2000 and 2002 outbreaks of the WNV encephalitis were reported in horses, birds and humans from New York and Canada. Ornithophilic mosquitoes are the principal vectors of the WNV and birds of several species chiefly migrants appear to be the major introductory or amplifying host. The pattern of outbreaks in the old and new world suggests that viremic migratory birds may also contribute to movement of the virus. If so, Central America, Caribbean Islands and countries of South America including Venezuela, are in potential risk for suffering a severe outbreak for WNV, since several species of birds have populations that pass trough New York and cross the western north Atlantic or Caribbean Sea. It is important the knowledge of the ecology of WNV as well of the efficacy of control efforts in order to minimize the public health impact in these countries, where all population is susceptible to this infection.
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Plotnik, J., Nelson, P. A., & de Waal, F. B. M. (2003). Visual field information in the face perception of chimpanzees (Pan troglodytes). Ann N Y Acad Sci, 1000, 94–98.
Abstract: Evidence for a visual field advantage (VFA) in the face perception of chimpanzees was investigated using a modification of a free-vision task. Four of six chimpanzee subjects previously trained on a computer joystick match-to-sample paradigm were able to distinguish between images of neutral face chimeras consisting of two left sides (LL) or right sides (RR) of the face. While an individual's ability to make this distinction would be unlikely to determine their suitability for the VFA tests, it was important to establish that distinctive information was available in test images. Data were then recorded on their choice of the LL vs. RR chimera as a match to the true, neutral image; a bias for one of these options would indicate an hemispatial visual field advantage. Results suggest that chimpanzees, unlike humans, do not exhibit a left visual field advantage. These results have important implications for studies on laterality and asymmetry in facial signals and their perception in primates.
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Herholz, C. P., Gerber, V., Tschudi, P., Straub, R., Imhof, A., & Busato, A. (2003). Use of volumetric capnography to identify pulmonary dysfunction in horses with and without clinically apparent recurrent airway obstruction. Am J Vet Res, 64(3), 338–345.
Abstract: OBJECTIVE: To investigate whether volumetric capnography indices could be used to differentiate between horses without recurrent airway obstruction (RAO) and horses with RAO that were in clinical remission or that had clinically apparent RAO. ANIMALS: 70 adult Swiss Warmblood horses (20 used for pleasure riding and 50 used for dressage or show jumping). PROCEDURE: Horses were allocated to 4 groups on the basis of history, clinical signs, results of endoscopy, and cytologic findings (group 1, 21 healthy horses; group 2, 22 horses with RAO that were in remission; group 3, 16 horses with mild RAO; group 4, 11 horses with exacerbated RAO). Expiratory volume and CO2 curves were recorded by use of a computerized ultrasonic spirometer. Volumetric capnograms were plotted, and derived indices were calculated. RESULTS: Dead-space volume (VD) was calculated by use of the Bohr equation (VD(Bohr)) and for physiologic VD (VD(phys)). Ratios for VD(Bohr) to expiratory tidal volume (VT) and VD(phys) to V(T) as well as an index of effective CO2 elimination were significantly different among groups of horses. Age and use of the horses also significantly affected volumetric capnography indices. CONCLUSIONS AND CLINICAL RELEVANCE: Ratios of VD(Bohr) to VT and VD(phys) to VT as well as an index of effective CO2 elimination were sufficiently sensitive measures to distinguish between healthy horses and horses with RAO in remission. To optimize the ability of volumetric capnography indices to differentiate among horses in heterogeneous populations, it is important to account for effects of age and specific use of the horses.
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Aberle, K. S. (2003). Untersuchung der Verwandtschaftsverhältnisse, Inzucht und genetischen Distanzen bei den deutschen Kaltblutpferderassen. Ph.D. thesis, , Hannover.
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Sole, L. M., Shettleworth, S. J., & Bennett, P. J. (2003). Uncertainty in pigeons. Psychon Bull Rev, 10(3), 738–745.
Abstract: Pigeons classified a display of illuminated pixels on a touchscreen as sparse or dense. Correct responses were reinforced with six food pellets; incorrect responses were unreinforced. On some trials an uncertain response option was available. Pecking it was always reinforced with an intermediate number of pellets. Like monkeys and people in related experiments, the birds chose the uncertain response most often when the stimulus presented was difficult to classify correctly, but in other respects their behavior was not functionally similar to human behavior based on conscious uncertainty or to the behavior of monkeys in comparable experiments. Our data were well described by a signal detection model that assumed that the birds were maximizing perceived reward in a consistent way across all the experimental conditions.
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Chase, I. D., Tovey, C., & Murch, P. (2003). Two's Company, Three's a Crowd: Differences in Dominance Relationships in Isolated Versus Socially Embedded Pairs of Fish. Behaviour, 140(10), 1193–1217.
Abstract: We performed experiments with cichlid fish to test whether several basic aspects of dominance were the same in isolated pairs as in pairs within a social group of three or four. We found that the social context, whether a pair was isolated or within a group, strongly affected the basic properties of dominance relationships. In particular, the stability of relationships over time, the replication of relationships in successive meetings, and the extent of the loser effect were all significantly less in socially embedded pairs than in isolated pairs. We found no significant winner effect in either isolated or socially embedded pairs. These findings call into question many current approaches to dominance that do not consider social context as an important factor in dominance behavior. These findings also cast serious doubt on the validity of empirical and theoretical approaches based on dyadic interactions. Among these approaches are game theoretic models for the evolution of aggressive behavior, experimental designs evaluating how asymmetries in attributes influence the outcome of dominance
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