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Call number: LD2668 .T4 1938 L51

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Four Greyhound dogs and six horses were utilized to study the physiological mechanisms associated with the development of an exercise training-induced hypervolemia. The animals were used in two separate experiments and were trained for 14 days on a treadmill ergometer and the data were used to formulate conclusions regarding the physiological and practical implications related to the phenomenon. The data reported in this dissertation indicated that exercise training will cause an expansion of the plasma volume in the Greyhound dog (+27%, P < 0.05) and the horse (+29.1% P < 0.05). Physiologically the result is similar in man, the dog, and the horse, however, the mechanisms by which this adaptation is reached appears to differ in each of the species. In the dog, water intake (+33%, P < 0.05) appears to be the primary mechanism for the increase in fluid volume. In the horse, renal control mechanisms (24-hr urine output -24.5%, P < 0.05) appear to be the primary mechanism with those that control the retention of solutes other than sodium predominating over those that control the reabsorption of sodium and water. Based upon the literature, it appears that in man, renal mechanisms predominate the hypervolemic response and mechanisms which control the conservation of sodium appear to be most active in the defense of the tonicity and volume of the vascular compartment. These species differences are important to the understanding of the physiology behind the onset of the training-induced hypervolemia and they provide pertinent information upon which decisions regarding the choice of animal models for future research.

Lameness is the most common medical complaint amongst domestic horses. Consequently, lameness assessment skills are expected of veterinary graduates as a day one skill by the Royal College of Veterinary Surgeons. However, recognising lameness is inherently difficult, especially for mild cases: even experienced assessors regularly disagree on the affected limb. The impact of a resulting misdiagnosis can be profound for both horse and owner. Even today, the biomechanical changes associated with lameness and the mechanisms of subjective clinical decision making are far from understood. Not surprisingly, there is currently no standardised way to teach students the 'art' of lameness detection. Hence, this thesis investigated core elements of the lameness examination in the framework of task analysis, combining biomechanics, vision science and educational research. Mechanical principles of movement asymmetry adaptations associated with locomotion of sound and lame horses on the straight, circle and after flexion tests were investigated. Subjective perception and objective quantification of asymmetry were compared, ranging from detection thresholds of naIve observers to factors influencing experienced veterinarians. Student performance at different stages was evaluated to understand the foundations students bring to future training. Expert visual approaches to lameness detection were quantified by means of eyetracking, investigating whether general principles can be derived to guide teaching. This work showed that it is possible to model and consequently simplify movement adaptations during lameness for future computer based training tools, however a systematic asymmetry bias of sound horses during lunging and after limb flexion needs to be considered. Differences between visual perception and objective quantification of asymmetry highlight the need for further exploration of perception-based diagnostics. While experts used relatively similar approaches when examining horses on the straight, there were considerable differences during assessment on the circle; in future, it would be of benefit to. develop a reliable and uniform assessment strategy.

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Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

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Two experiments were conducted to investigate the effect of conditioning on the ability of the equine to digest and utilize nutrients and to determine the effect of dietary fat as an energy source on the physiological parameters associated with fitness using a standard exercise test. Conditioning horses increased apparent digestibilities of crude protein (CP) (P<.05), dry matter(DM), and acid detergent fiber (ADF) (P<.1). Conditioning also tended to increase the apparent digestibility of neutral detergent fiber (NDF), cellulose, cell contents, and energy. Heart rates and blood lactate levels indicated that the conditioned horses were fitter than their unconditioned controls. In the second experiment, horses were fed isocaloric diets, one containing added fat and the other a standard hay/corn diet. Adding fat while maintaining equal available energy concentration depressed apparent digestibility of dry matter (56.7 vs 67.3 % P<.05), cell contents (75.6 vs 82 %, P<.05), energy (61.2 vs 71.8 %, P<.05) and NDF (29.2 vs 51.3 %, P<.05), in unconditioned horses. There was a trend towards decreased apparent digestibility of CP and ADF. Addition of fat increased apparent digestibility of ether extract (89.2 vs 65.6 %, P<.05). Conditioning increased apparent digestibility of CP (64.8 vs 73.7 %, P<.05) and energy (61.2 vs 65.6 %, P<.05) and tended to increase apparent digestibility of DM (56.7 vs 60.8 % ) and ADF (26.8 vs 17.8 %) for horses fed a fat supplemented diet. Conditioning did not cause a change in apparent digestibility of ADF, CP, and DM in horses fed the control diet, or apparent digestibilities of NDF, ether extract, cell contents, or energy for either diet. There were no differences in physiological parameters used for assessing fitness (heart rate, blood lactate, and respiration rate), between horses fed a diet containing 14% added fat and no added fat. There was no difference in body temperature, blood glucose levels, blood urea-N (BUN), or creatine phosphokinase (CPK) between horses fed the two diets. / Ph. D.