Dissertation (PhD)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Inaug.-diss.-Bern. / Lebenslauf. "Literatur": p. [53]-54.

Thesis (MS)--Montana State University--Bozeman, 2010. / Typescript. Chairperson, Graduate Committee: Shannon Moreaux. Includes bibliographical references (leaves 64-69).

Osteoarthritis of the metacarpo/metatarsophalangeal joint is a major cause of lameness in the horse. Magnetic resonance imaging and particularly delayed gadolinium enhanced imaging of cartilage (dGEMRIC) and T2 cartilage mapping in humans has been shown to visualize cartilage matrix changes in osteoarthritis early in the disease process. T2 mapping is a non-invasive technique characterizing hyaline articular cartilage and repair tissue. In dGEMRIC, the negatively charged administered Gd-DTPA2−, penetrates hyaline cartilage in an inverse relationship to the proteoglycan concentration thereof. In osteoarthritis, proteoglycan concentration is decreased with increased penetration of Gd-DTPA2− due to a relative decrease in negative charge of the proteoglycan-depleted cartilage. This study was performed on normal cadaver limbs of twelve euthanized racing Thoroughbreds. Six horses’ midcondylar distal third metacarpals/metatarsals (Mc3s/Mt3s) underwent six precontrast inversion recovery (IR) sequences for dGEMRIC T1 relaxation time calculation, as well as T2 mapping sequences using a 1.5T machine. Gd-DTPA2- was injected intra-articularly and the same six IR sequences repeated at 30, 60, 120, and 180 minutes post-injection at the same midcondylar sites. The distal Mc3/Mt3 cartilage thickness was measured histologically and compared to selected images of the T1 and T2 weighted sequences. T1 and T2 maps were created by fitting the respective data into mono-exponential relaxation equations for each pixel, and mean values of certain regions of interest were calculated. A second group of six horses’ fore and hind limbs were randomly assigned to two groups and the limbs either chilled or frozen, allowed to return to room temperature and scanned similarly to the first control group. Chilling and freezing effects on dGEMRIC and T2 mapping results were evaluated. The main conclusions from this study are that IR and proton density weighted (T2 mapping) sequences can measure distal Mc3/Mt3 cartilage thickness where the cartilage doesn’t overlap with that of the proximal phalanx. However, accurate measurement was hampered by the thin cartilage in this region. dGEMRIC mapping, using intra-articular Gd-DTPA2- is a feasible technique and T1 relaxation times decrease in a similar fashion to that of the human, with the optimal time of scanning after intra-articular Gd-DTPA2- injection being 60-120 minutes. There is little effect on T1 or T2 relaxation time and mapping images after chilling and freezing of the limbs except where the magic angle effect predominates in the T2 mapping sequences. Limitations of this study include relatively coarse spatial resolution of the thin cartilage, the overlap of the distal Mc3/Mt3 cartilage with the adjacent phalanx and the relatively low number of limbs used, resulting in low statistical power, particularly in the frozen limbs’ study. In spite of these limitations, this study provides technical information and reference values of dGEMRIC and T2 mapping in the cadaver distal Mc3/Mt3 of the normal Thoroughbred horse of value for forthcoming studies. Future studies need to evaluate intravenous administration of Gd-DTPA2- and cartilage mapping in live exercised vs. non-exercised horses. Ultimately, dGEMRIC and T2 mapping of horse metacarpo/metatarso-phalangeal joints with differing degrees of osteoarthritis should be used to attempt to diagnose early cartilage degeneration to endeavour to halt or delay its progression. / Thesis (PhD)--University of Pretoria, 2013. / gm2013 / Companion Animal Clinical Studies / unrestricted

For several decades, the origin of domestic horses has been the focus of research across multiple disciplines, yet many aspects of the horse domestication process remain poorly understood. One of the reasons for the difficulty in establishing a coherent scenario of horse domestication is that archaeological, mtDNA, and Y chromosome data have yielded ambiguous results, possibly because each class of markers reflects different aspects of the domestication process. In this thesis, I use large autosomal genetic datasets from horses sampled across Eurasia to investigate the origin and spread of horse domestication. I begin by characterising genetic diversity of horses from the Eurasian steppes and neighbouring regions, thus laying the groundwork for a more thorough analysis into the demographic history of horses. I then investigate the origin and mode of spread of horse domestication in the Eurasian steppe region using a spatially explicit genetic model. I show that horse domestication was initiated in the western part of the steppes, and that the spread of horse domestication involved both movement of domestic herds and extensive recruitment of wild horses from across this vast region, a scenario which integrates both archaeological and molecular evidence. Having established the route of spread of early domestic horses out of their domestication origin in the western steppe, I go on to investigate the routes and levels of gene flow among Eastern Eurasian horse populations post-domestication. I show that the ancient Silk Roads have played an important role in shaping the genetic structure of Eastern Eurasian horses, facilitating gene flow across deserts and high mountain chains. Finally, I provide further compelling evidence for the persistence of wild horses in the Iberian Peninsula throughout the Holocene period, and the substantial contribution of these local populations to the gene pool of Iberian domestic horses. Together, my results provide a coherent picture of the origin and spread of horse domestication, integrating for the first time previous evidence from archaeology, mtDNA and Y chromosome sequence data.

Respiratory conditions causing poor performance in horses are usually as result of upper respiratory tract diseases or are of pulmonary origin. The tracheal is rarely a cause of primary respiratory problems in the horse, but tracheal dimensions, particularly height, may be useful in evaluating upper repiratory tract conditions cranial to the trachea and lung pathology, due to resultant change in differential pressures between these areas. The normal radiological equine tracheal height along its length has as yet not been reported. Standing lateral radiographs of the cervical and thoracic trachea of 15 clinically normal sedated Thoroughbred horses, 3-6 years old, were made at peak inspiration and end expiration. Maximum height of the larynx, and trachea at the level of the third and fifth cervical vertebra, at the level of the first thoracic vertebra, carina and the left and right primary bronchi were measured. Ratios of laryngeal height relative to the third cervical vertebral body length and tracheal heights relative to the vertebral body lengths of adjacent third and fifth cervical vertebrae and first thoracic vertebra, and carina heights relative to a mid-thoracic vertebra, respectively were made, as well as tracheal height at the fist thoracic vertebra ratio with the thoracic inlet height. Known size metallic markers were used to determine magnification corrected tracheal heights in the sagittal plane and effect of body mass and height at the withers on tracheal height was determined. The magnification corrected radiological airway heights at end expiration and peak inspiration were measured and respectively the mean values were found to be: laryngeal height: 5.89 cm and 5.86 cm, tracheal height at the third cervical vertebra: 4.17 cm and 4.04 cm, tracheal height at the fifth cervical vertebra: 3.62 cm and 3.59 cm, tracheal height at the first thoracic vertebra: 3.4 cm and 3.23 cm and carina height: 3.85 cm and 4.12 cm. The ratios of these measurements to nearby vertebral body lengths were respectively: laryngeal height at the third cervical vertebra: 0.56 and 0.56, tracheal height at the third cervical vertebra: 0.4 and 0.39, tracheal height at the fifth cervical vertebra: 0.37 and 0.37, tracheal height at the first thoracic vertebra: 0.59 and 0.59, and carina height: 0.91 and 0.94. The ratio tracheal height at the first thoracic vertebra to the thoracic inlet respectively 0.15 and 0.15. Although there was no statistical difference in the data, there was a trend towards a higher tracheal height at expiration. No correlation was found between tracheal height and body mass or tracheal height and height at the withers, and measured tracheal height was generally lower than predicted tracheal height, possibly as result of sedation used. The small range of body mass and height in this study as well as the relatively small number of horses evaluated may account for the lack of correlation to predicted tracheal height. This study in normal horses may serve as a reference when radiologically evaluating cases of upper respiratory tract and lung pathology, where the tracheal dimensions may differ significantly due to differences in airway resistance and biomechanics. Radiographs to evaluate tracheal height can be made independent of respiratory phase in sedated horses, and it is recommended that ratios of tracheal height to an adjacent vertebral body length are more reliable values to compare within and between horses. It is recommended to take tracheal height measured at the fifth cervical vertebra since this measurement showed a slightly smaller standard deviation than at other sites measured as well as a medium amount of clinical effect. If only thoracic radiographs are made, measurements of tracheal height at the thoracic inlet is the alternative (the standard cranioventral view), but it is recommended to include the distal aspect of the first rib if the thoracic inlet is to be measured. / Dissertation (MMedVet)--University of Pretoria, 2008. / Companion Animal Clinical Studies / unrestricted

Previous studies have shown that four intramuscular doses of imidocarb dipropionate administered at 72-hour treatment intervals are effective in sterilising experimental Babesia equi infections in horses. It has also been documented that imidocarb dipropionate has dose dependent hepato- and nephrotoxic effects in a number of species. The purpose of this study was to examine the clinical and clinicopathological effects of this multiple treatment regime of imidocarb dipropionate in healthy ponies. Specific emphasis was placed on the potential adverse effects on hepatic and renal function in this species. Serum bile acids and serum gamma glutamyltransferase activity were measured to evaluate the effect of this treatment regime on hepatic function. The diffuse hepatocellular necrosis and pronounced periportal hepatocellular swelling and degeneration previously reported as the most consistent hepatic lesions noted in equines following imidocarb treatment were not evident at the dose and dosage interval used in this study. Urinary gamma glutamyltransferase: creatinine ratios (IU/g) and fractional clearance of sodium, potassium and phosphate (%) were calculated as a measure of renal function. Urinary GGT and urinary GGT: creatinine ratios were significantly elevated on Day 5 of the trial and were considered indicative of transient changes in renal function. The rapid return to previous baseline values supported reported observations that changes between 25 and 100 IU/g may be a function of drug excretion and are not necessarily indicative of significant nephrotoxicity. It was concluded that four intramuscular treatments of imidocarb dipropionate at a dose of 4 mg/kg every 72 hours may be a relatively safe method whereby persistent Babesia equi infections can be sterilised. / Dissertation (MMedVet)--University of Pretoria, 2000. / Equine Research Centre / unrestricted

An ideal dexmedetomidine protocol has yet to be determined for standing sedation in horses. It was hypothesized that an intravenous (IV) bolus followed by continuous rate infusion (CRI) dexmedetomidine would have a quicker increase in plasma concentrations compared to repeated intramuscular (IM) injections. In a cross-over design, eight adult, female horses were randomly placed in two groups: the CRI group (IV bolus dexmedetomidine at 0.005 mg/kg followed by a CRI at 0.01 mg/kg/hr for 15 minutes then 0.005 mg/kg/hr for 60 minutes) and the IM group (dexmedetomidine at 0.01 mg/kg, followed by 0.005 mg/kg in 30-minute intervals for 60 minutes). Analgesia was evaluated using a mechanical pressure threshold device. Intravenous dexmedetomidine produced faster onset of sedation and increased pressure threshold compared to IM administration. Individual horses had a large variability in dexmedetomidine plasma concentrations between CRI and IM administration.

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