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McDonnell, S. M. (1993). More on self-mutilative behavior in horses. J Am Vet Med Assoc, 202(10), 1545–1546.
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Ratzlaff, M. H., Wilson, P. D., Hyde, M. L., Balch, O. K., & Grant, B. D. (1993). Relationship between locomotor forces, hoof position and joint motion during the support phase of the stride of galloping horses. Acta Anat (Basel), 146(2-3), 200–204.
Abstract: Three methods were used simultaneously to determine the relationships between the vertical forces exerted on the hooves and the positions of the limbs and hooves at the times of peak vertical forces from 2 horses galloping on a track straightaway. Vertical forces were recorded from an instrumented shoe, fetlock joint motion was measured with an electrogoniometer and the angles of the carpus, fetlock and hoof were determined from slow-motion films. At hoof contact, the mean angles of the carpus and fetlock were 181-182 degrees and 199-206 degrees, respectively. Peak vertical forces on the heel occurred at or near maximum extension of the carpal and fetlock joints. Peak forces on the toe occurred during flexion of the fetlock joint and at mean hoof angles of 28-31 degrees from the horizontal. The mean angles of the hoof from the horizontal at the time of heel contact were 6-7 degrees. Hoof lift occurred at mean carpal angles of 173-174 degrees and mean fetlock angles of 199-200 degrees.
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Clayton, H. M. (1993). The extended canter: a comparison of some kinematic variables in horses trained for dressage and for racing. Acta Anat (Basel), 146(2-3), 183–187.
Abstract: This study was designed to test the hypothesis that there is no significant difference in selected temporal and linear stride variables of the extended canter in horses bred and trained for dressage or racing. Nine advanced-level dressage horses and 7 Thoroughbred racehorses were filmed at a frame rate of 200 Hz at an extended canter on a sand track. Two strides were recorded per trial, and each horse performed 6 or 7 trials. Temporal and linear data were determined from the films, and descriptive statistics (mean, SD) were calculated. Strides were selected for analysis on the basis of having a velocity in the range of 6.0-7.0 m/s, and multivariate analysis of variance was used to detect significant differences in the stride kinematics of horses trained for the two sports (p < or = 0.01). The average velocity of the dressage horses was 6.37 m/s, compared with 6.40 m/s for the racehorses. There were no significant differences between the two groups in velocity, stride duration, stride length or the distances between limb placements. The stance durations of all four limbs and the overlaps between them were longer, whereas the duration of the suspension phase was shorter in the dressage horses than in the racehorses (p < or = 0.01). The time between impacts of the diagonal limb pair was close to zero in both groups, with individual horses showing some variability in the order of placement of the diagonal limb pair. However, the sequence of footfalls was not significantly different between the two groups (p < or = 0.01).
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Argue, C. K., & Clayton, H. M. (1993). A preliminary study of transitions between the walk and trot in dressage horses. Acta Anat (Basel), 146(2-3), 179–182.
Abstract: The object of this study was to determine the limb support sequence during the transitions from walk to trot and from trot to walk in dressage horses under saddle and to test the null hypothesis that the limb support sequence during the transitions is not related to the level of training. Sixteen dressage horses training at novice to FEI Grand Prix level were videotaped performing an average of 9 transitions each from walk to trot and from trot to walk. The 30-Hz videotapes were viewed in slow motion, and based on the limb support sequence the transitions were categorized into two types. In type 1 transitions there were no intermediate steps between the walk and trot sequences. Type 2 transitions were characterized by intermediate steps, including a single support phase. The Kendall rank-order correlation coefficient showed that a higher level of training was positively associated with an increased percentage of type 1 transitions for both walk-to-trot transitions (p < or = 0.05) and trot-to-walk transitions (p < or = 0.01). No significant preference for initiating or completing the trot on the left or right diagonal was found using the binomial test for individual horses and the Wilcoxon signed-ranks test for the group.
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Colahan, P., Lindsey, E., & Nunier, C. (1993). Determination of the center of pressure of the hoofs of the forelimbs of horses standing on a flat level surface. Acta Anat (Basel), 146(2-3), 175–178.
Abstract: The pressure exerted on a flat level surface by recently trimmed, unshod hoofs of the front limbs of 23 sound, adult horses was measured using pressure-sensitive film and a specially built cassette. The horses were tranquilized and stood with one foot on the 2.9-cm-thick cassette and the other on a block of equal height. The hoofs were observed for motion during the measurement, and the developed film was examined for improper alignment of the film or slipping of the hoof. The center of pressure was located using the method of weighted proportions of Barrey. This static measurement system with a long measurement time and the number of measurements reduced the influence of variables inherent in the horses' behavior and the measuring system. The calculated point was recorded as falling medial to, lateral to or on a line bisecting the central sulcus of the frog. In the dorsal to palmar orientation the point was classified with reference to a line drawn halfway between the most dorsal and the most palmar mark on the film. Forty-six percent of the calculated centers of pressure were located in the medial heel area. Binomial analysis for large samples indicates that this was a significant variation from a random distribution. Seventy-six percent of the centers were located in or on the borders of the medial heel.
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Capela, R., Sousa, C., Pena, I., & Caeiro, V. (1993). Preliminary note on the distribution and ecology of Culicoides imicola in Portugal. Med Vet Entomol, 7(1), 23–26.
Abstract: Data on Culicoides imicola were obtained during studies carried out during the recent outbreak of African horse sickness in Portugal. The previous most northerly published record of C. imicola in Portugal was 38 degrees 40'N (Pegoes). In the present work the geographical distribution of this species is extended to the parallel of 41 degrees 17'N. We have also confirmed the continuous presence of adult C. imicola in Southern Portugal (Alentejo and Algarve) throughout the year. In the laboratory we obtained this species from a sample of cattle faeces and from another of soil contaminated with animal excreta. In relation to host association 57.37% of C. imicola were trapped in the vicinity of pigsties. Finally, we collected 11,463 Culicoides of which 12.47% were C. imicola.
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McClure, S. R., & Chaffin, M. K. (1993). Self-mutilative behavior in horses. J Am Vet Med Assoc, 202(2), 179–180.
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Shettleworth, S. J. (1993). Varieties of learning and memory in animals. J Exp Psychol Anim Behav Process, 19(1), 5–14.
Abstract: It is often assumed that there is more than one kind of learning--or more than one memory system--each of which is specialized for a different function. Yet, the criteria by which the varieties of learning and memory should be distinguished are seldom clear. Learning and memory phenomena can differ from one another across species or situations (and thus be specialized) in a number of different ways. What is needed is a consistent theoretical approach to the whole range of learning phenomena, and one is explored here. Parallels and contrasts in the study of sensory systems illustrate one way to integrate the study of general mechanisms with an appreciation of species-specific adaptations.
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Forbes, A. B. (1993). A review of regional and temporal use of avermectins in cattle and horses worldwide. Vet Parasitol, 48(1-4), 19–28.
Abstract: Ivermectin and abamectin are two members of the group of parasiticides known as the avermectins; ivermectin was first registered as an injectable treatment for cattle in 1981. Since then, abamectin has been registered for cattle and ivermectin for horses. The relative popularity of the avermectins amongst farmers and veterinarians can be attributed to their spectrum of activity, convenience, wide margin of safety and the improved health and performance of stock following their use. Patterns of use in grazing animals apply equally to the avermectins as to other antiparasitics, particularly anthelmintics; these are based on a knowledge of epidemiology integrated with practical management considerations. For cattle, programs are commonly aimed at control of abomasal nematodes of the genera Ostertagia and Haemonchus. Use of avermectins is largely strategic in cattle, treatments being favored at the end of the period of transmission of these parasites; this frequently coincides with housing, entry into a feedlot or movement to another pasture. Simultaneous control of important ectoparasites at this time is an added benefit. Prophylactic use of avermectins at pasture is primarily targeted at the young first season grazing animal. In horses, a bimonthly treatment schedule during the period of risk has proved effective in helping prevent adverse effects of the main target parasites, including large and small strongyles and stomach bots. These patterns of use can be applied to the evaluation of the potential for avermectin residues in feces to have impact on pasture ecology. The evidence presented suggests that any effects are temporally and spatially limited. After more than a decade of practical use, there is no indication that avermectins have had a significant impact on pasture ecology and the environment.
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Stadler, P., Rewel, A., & Deegen, E. (1993). [M-mode echocardiography in dressage horses, class S jumping horses and untrained horses]. Zentralbl Veterinarmed A, 40(4), 292–306.
Abstract: Heart structures of 45 warmblooded horses were measured by M-mode-echocardiography. The current training level of 15 dressage horses (group I) and 15 show-jumping horses (group II) was category “S”. In the third group were 15 untrained horses. Four standardized transducer positions were determined for the m-mode echobeam, calibrated according to the two-dimensional real time technique. End systolic and end diastolic diameters of left ventricle, right ventricle, aortic root, interventricular septum and left ventricular wall, as well as motion pattern of heart wall, mitral valve and aortic valve of all horses were measured. The dressage horses showed a significant thickening of interventricular septum and left-ventricular wall compared with the show-jumping horses and the untrained horses. The end diastolic left ventricle diameter of the show-jumping horses was significantly larger than in the other groups. Compared to the untrained horses the show-jumping horses showed a significantly larger end systolic left ventricular wall diameter measured at the level of papillary muscle. It can be concluded, that an increase in heart mass in category “S” sport horses is attributed to their level of training.
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