Thesis (Ph. D.)--University of Wisconsin--Madison, 1960. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: leaves 107-111.

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Arena surfaces used for training and competition are influenced by factors such as weather and maintenance, which can lead to spatial variations in functional surface properties. The ability of the horse to adapt to such changes may have implications for injury prevention. The aim of the PhD was to quantify kinematic and neuromuscular responses of horses to a camouflaged abrupt change in functional surface properties. Horses (n=7) were trotted in hand at a consistent speed across an arena surface that had been prepared in four ways: continuous firm; continuous soft and when the surface presented a camouflaged, abrupt change from firm to soft and soft to firm. Kinematic data (232Hz) synchronised with surface electromyography (sEMG) (1926Hz) from selected forelimb muscles were recorded. The first trial (no awareness of change) was categorised separately to the subsequent trials (2-8; aware of change). A General Linear Model was used to assess the effect of horse, stride location and awareness on kinematics and sEMG. There were limited stride to stride changes on the continuous surfaces. When travelling from firm to soft, fore F (2, 125) = 11.55, P < 0.0001 and hind F (2, 116) = 12.47, P < 0.0001 limb retraction significantly reduced as the horses stepped onto the soft surface. Awareness of the abrupt change also significantly reduced fore F (1, 125) = 7.28, P =0.008 and hind F (1, 116) = 10.16, P =0.002 limb retraction. When travelling from soft to firm, hindlimb stance duration F (1, 99) = 7.3, P =0.008 and duty factor F (1, 61) = 7.82, P =0.007 significantly increased and peak metacarpophalangeal extension significantly F (1, 93) = 7.85, P =0.006 reduced as the horses stepped onto the firm surface. Awareness of the abrupt change significantly increased stance duration F (1, 99) = 14.92, P < 0.0001, duty factor F (1, 61) = 8.18, P =0.006 and peak metacarpophalangeal extension F (1, 93) = 3.98, P =0.049. There was some evidence of neuromuscular contributions that helped to stabilise the forelimb and control posture immediately before hoof impact and during stance. The gait modifications observed demonstrated horses can alter their balancing strategy to cope with a change in surface condition. Reduced limb retraction shifted the COM position relative to the hoof position at lift off more caudal and reduced a falling forward posture as the horses stepped down onto the soft surface and with awareness. When the horses travelled from soft to firm, vertical impulses increased in the hindlimb, which was thought to maintain pitch stability. Vertical impulses showed a more even distribution between the fore and hind limbs with awareness suggesting the fore limbs played a larger role raising the forehand.

The historical and evolutionary perspectives of equine laminitis were placed in a contemporary context of hippology. A survey revealed 3% of the equine population in the UK to be affected by laminitis. Physiological aspects affecting pedal blood flow, namely endocrine and haemodynamic relationships, were considered under controlled management. Pedal haemodynamics, investigated non-invasively using Near Infrared Spectroscopy, detected changes in concentrations of oxyhaemoglobin, deoxyhaemoglobin and cytochrome oxidase, indicating tissue utilisation of oxygen and hence perfusion. Responses of chronic larninitics suggested attenuated blood flow and local hypoxia. Haemostasis was shown to occur in acute larninitis The role of nitric oxide was investigated by assessment of the effects of concentrations of substrate, synthetic nitric oxide donors, and endogenous and exogenous, inhibitors of nitric oxide synthesis. Reperfusion of ischaernic laminal tissue during acute laminitis was initiated by iv administration of I-arginine, a substrate of nitric oxide (NO) synthesis; this also increased blood flow in laminal tissues of a normal horse, but had little effect on blood pressure. Grass induced acute laminitis was successfully treated with transdermal application of glyceryl trinitrate paste to the pasterns. A competitive inhibitor of I-arginine synthesis increased blood pressure of normal horses but did not induce acute laminitis. Plasma I-arginine increased when normal and chronically laminitic horses went to grass. Plasma asymmetric dimethyl-l-arginine (ADMA) was lower in chronic laminitics than normal ponies; ADMA decreased when at grass from 1.2 [tmol/L to 0.7 [tmol/L in normal horses and from 0.8 tLmol/L to 0.47 [tmol /L in chronically laminitic ponies. Radioimmunoassays for angiotensin II, atrial natriuretic peptide and endothelin were validated and basal values for the horse established as 24 ±2 pg/ml, 34 ±2 pg/ml and 1.78 ± 0.2 pg/ml respectively. Seasonal differences in AII and ANP were observed. Endocrine changes, observed during acute laminitis, were neither large nor sustained. Blood pressures and heart rate were significantly raised at the acute stage but otherwise unremarkable. Although transient hypertension occurs during acute laminitis, chronic laminitics are not hypertensive. Moderate hypertension accompanies refractory laminitis but this does not appear to be mediated by angiotensin II or endothelin. Electrolyte concentrations were largely unaffected but slight seasonal differences were seen alongside sodium retention in refractory and some chronic cases. Digestive disturbances of acute laminitis were reflected in decreased urinary contents of hippuric: acid. Seasonal changes in ingested electrolytes and water soluble carbohydrates are part of the complex pathogenesis of acute laminitis. An hypothesis outlines potential and actual relationships between dietary factors, endotoxaemia and the vasoactive hormones whose interplay may adversely influence pedal haemodynamics in developmental and acute equine laminitis.

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Giessen, University, Diss., 2004.

The thoroughbred horse has been selectively bred for speed and has a high capacity for carbohydrate metabolism. The following series of studies investigated the relative contribution of fat and carbohydrate to energy production during exercise of varying intensity. Furthermore the work assessed the capacity of the horse to increase the contribution of fat to energy production as the result of either an acute increase in the availability of plasma free fatty acids (FFA) or as the result of chronic fat supplementation. Finally an adaptational response to feeding a fat supplemented diet was described. The variation in plasma long chain FFA over a 24 hour period was described. The early hours of the morning represented the period of greatest variability in plasma FFA concentration. This period was characterised by a significant increase in total and individual FFA concentration, which was unrelated to feed intake. As a result of the reported circadian rhythm in plasma FFA all subsequent exercise studies were performed during the period of least variability in plasma FFA concentration. A model for the pre-exercise elevation of plasma FFA, using a combination of a triglyceride emulsion and the heparinoid type substance pentosan polysulphate, was used to investigate the effect of increased FFA availability on fat utilisation during prolonged low intensity exercise. Pentosan polysulphate was used in preference to heparin following an investigation of their relative lipolytic and anticoagulative properties. Pentosan polysulphate when administered at 3 times the dose of heparin resulted in a comparable increase in plasma total lipase activity. When co-administered with a triglyceride emulsion, pentosan polysulphate resulted in a similar increase in plasma FFA concentration relative to that produced with the same triglyceride emulsion and heparin. The anticoagulative effect of pentosan polysulphate, however, was approximately 9 times less than that of heparin, as measured by activated partial thromboplastin time. The contribution of fat and carbohydrate to energy production during exercise was influenced by both the intensity and duration of exercise, as indicated by measurements of respiratory exchange ratio (RER). The inter-horse variability in RER was greatest during low intensity exercise. An increase in the contribution of carbohydrate to energy production occurred at the onset and during the early stages of prolonged exercise and as the result of an increase in exercise intensity. A proportion of horses exhibited an increase in the utilisation of fat during low intensity prolonged exercise as a result of a pre-exercise elevation in plasma FFA concentration. RER was consistently lower during exercise in 5 out of the 7 horses studied following a pre-exercise elevation of plasma FFA. Furthermore, plasma glucose concentration was elevated above that observed during the control session in 4 of these 5 horses for at least the first 15 minutes of exercise. A prolonged period of fat supplementation resulted in an improved management of the fat load. Following 10 weeks of dietary treatment a significant increase in plasma cholesterol concentration and a significant decrease in plasma triglyceride concentration was reported. The decrease in plasma triglyceride concentration was associated with a mean 50% increase in post pentosan polysulphate plasma total lipase activity. It is suggested that the increase in the post pentosan polysulphate plasma total lipase activity may have reflected an increase in muscle lipoprotein lipase activity. A significant increase in the activity of muscle citrate synthase was observed during the period of fat supplementation. No significant change occurred in muscle ß-hydroxyacyl CoA dehydrogenase activity or in the concentration of resting muscle glycogen and triglyceride as a result of fat supplementation. RER was significantly lower in the latter stages of prolonged low intensity exercise, during the period of fat supplementation, relative to the same exercise performed before the introduction and following 5 weeks of withdrawal of the fat supplemented diet. The reduction in RER during the period of fat supplementation was associated with a greater exercise induced increase in plasma FFA concentration. The above differences were also apparent during moderate intensity exercise, although, examination of the individual horse data revealed that the effect was not as clear as that observed during low intensity exercise. No significant differences were reported in either RER or plasma FFA concentration in response to moderate/high intensity exercise during the period of fat supplementation. Neither were any significant differences observed in either RER or plasma FFA concentration in the control group at any exercise intensity. An increased availability of plasma FFA and an increase in the oxidative capacity of muscle, as well as an enhanced ability to utilise plasma triglycerides may have contributed to the increase in fat utilisation, observed during low and moderate intensity exercise, in response to fat supplementation. The effect of differences in the hormonal response to a fat supplemented diet as a precipitant of the observed adaptational responses in these studies requires further investigation.

Master of Science in Biomedical Sciences / Department of Clinical Sciences / Elizabeth Davis / Leptospirosis is a worldwide veterinary and public health concern, and emerging infectious disease of horses. The spirochete can be directly transmitted by contaminated urine, placental fluids, semen, infected tissues, reservoir hosts, or flood waters. Seroprevalence and infecting serovar vary with geography, yet diagnosis using the gold standard microscopic agglutination test (MAT) merely confirms a high exposure rate. Subclinical infection can complicate diagnosis. The aims of this study were to use semi-nested PCR on urine from apparently healthy horses to determine period prevalence of leptospiral shedding and to correlate these findings with MAT results to establish associations with client based survey data regarding horse management and environment. Serum and free-catch urine were collected from 204 healthy horses between May 2016- December 2017. Serum was used to determine GGT, creatinine concentrations, and six serovar MAT (Canicola, Hardjo, Icterhemorrhaegiae, Pomona, Grippotyphosa, Bratislava). Urine samples were submitted for PCR testing of leptospiral 23S rRNA. Client consent and survey data were collected for all subjects. Potential risk factors included drinking water source, exposure to livestock and dogs, geographical location, season, and precipitation. Two horses were positive on urine PCR for leptospirosis (shedding prevalence 1%), yet only one had a high reciprocal MAT titer of ≥800. Both horses were negative on urine PCR one month later without treatment. Approximately 77% of horses (157/204) were seroreactive (MAT reciprocal titer ≥100) for at least one serogroup, and Bratislava was detected more frequently than others (47.5%; (97/204)). Apparently healthy horses infrequently shed Leptospira spp. in urine, yet seroreactivity in clinically normal horses is high (77%), confirming high exposure rates to Leptospira spp. in the Central Midwest. Further studies should target serovar specific PCR tests and incorporate PCR testing in horses clinically affected with leptospirosis.