Dissertations / Theses on the topic 'Thoroughbred horse'

Thesis (M. Sc. Vet. Sc.)--University of Sydney, 2008.
Includes graphs and tables. Title from title screen (viewed June 11, 2009) Submitted in fulfilment of the requirements for the degree of Master of Science in Veterinary Science to the Faculty of Veterinary Science. Degree awarded 2008; thesis submitted 2007. Includes bibliography. Also available in print form.

Developmental Orthopaedic Disease (DOD) describes problems affecting the limbs of young horses, including abnormal bone, joint and tendon development. DOD is responsible for major economic losses in the Thoroughbred industry. Investigation into the epidemiology of DOD in Australia and Ireland as described in this thesis has allowed valuable comparisons and recommendations to be made between the studs in these countries. The project described in this thesis commenced in 1999, with the aim to: a) Establish the incidence of DOD on a stud in Australia and to compare this with similar data for a stud in Ireland b) To determine relationships between factors affecting severity and incidence of DOD in foals with respect to the country in which they are bred and raised c) To further identify risk factor areas associated with the development of DOD Records of 1717 mares from a major stud in Ireland and another in Australia were made available. Foal weight, age of mare, condition of mare, foal sire and date of birth were monitored over two years. The occurrence of DOD was recorded against these data. The incidence of DOD was found to be higher on the stud in Australia (average 49.85%) than on the stud in Ireland (average 14%). Foal weight was found to be a significant factor affecting DOD, with heavier foals showing a proportionally higher severity of the problem. The Australian stud had a higher incidence of DOD in 2000 compared to 1999 (65.2% affected vs 32.1% in 1999), whereas the Irish stud had a lower incidence in 1999 compared to 2000 (11.8% affected vs 16.2% in 2000). The dramatic increase in the incidence of DOD in Australian foals over the 1999-2000 period is representative of the increase in a major problem in the industry, as well as greater awareness of the problem over recent years. It highlights the urgent need for further research into understanding the cause(s) of DOD. Overall recommendations arising from the study include that a large scale, long term study be undertaken in Australia. Further investigation into the nutrition of horses in Ireland and Australia would be of great usefulness in understanding DOD, as would possible genetic links. An issue requiring attention is that of developing a standard definition of the disorder. Considering the wide range of disorders which may fit under the umbrella term DOD, a clear definition is of great importance. The incidence of DOD on one large farm in Ireland was found to be currently low and stable relative to its another large stud farm in Australia. This is a significant finding as the genetic pool of the horses share similarities on both farms, particularly as stallions shuttling between hemispheres sire many foals on both farms. Thus, the data provided herein provide an excellent basis for further valuable comparative studies investigating DOD in foals with a similar genetic background but subjected to differing environmental conditions.

A radiographic examination forms part of the pre-purchase examination of Thoroughbred yearlings at national sales in many countries. This data enables the recording of the prevalence of radiographic changes in selected Thoroughbred populations around the world and assists veterinarians in advising clients on the purchase of yearlings. This has financial implications for the client as well as the racing industry as a whole. Radiographic examinations of the 269 Thoroughbred yearlings lodged at the 2008 National Yearling Sale in Germiston, South Africa were collected and individually evaluated. The prevalence of radiographic changes was recorded and percentages calculated. These changes were compared to studies of other yearling populations. Radiographic changes present in the studied Thoroughbred population are: pedal osteitis 1.26%, metatarsophalangeal joint dorsal osteochondral fragmentation 1.60%, sagittal ridge changes 5.7%, ulnar carpal bone lucencies 8.33%, carpal osteophytes 1.19%, distal intertarsal and tarsometatarsal joint radiographic changes 9.92%, tarsal osteochondrosis lesions 4.4% and stifle joint osteochondrosis lesions 0.4%. These changes were found to be of lower prevalence when compared to similar studies. The prevalence of dorsal osteochondral fragments in the metacarpophalangeal joint was 1.60% which was similar to other studies. A higher prevalence of vascular channels was visible in the proximal sesamoid bones as well as irregular borders and lucencies. Palmar metacarpophalangeal and plantar metatarsophalangeal osteochondral fragments had a recorded prevalence of 2% and 7.10%, respectively, this prevalence being generally higher when compared to similar studies. There was an absence of palmar metacarpal disease, supracondylar lysis, proximal sesamoid bone fractures and carpal osteochondral fragmentation in the current study. Additional findings recorded in the current study were: proximal interphalangeal joint hyperextension (left front 15.13%, right front 18.91%), the solar angle (right front 2.38°, left front 2.79°), the prevalence of carpal bone one (30.95%) and carpal bone five (1.59%). The study population was limited to the radiographs lodged at the sale repository. As radiographic changes may influence sale price of the yearling, radiographs of yearlings with severe radiographic changes may not have been lodged at the repository. For these reasons the prevalence of radiographic changes recorded in the current study may not be a true reflection of the entire 2006 Thoroughbred foal crop. Further work to correlate radiographic changes to differences in management, pre-sale exercise programmes and genetics needs to be done. The effect of radiographic changes on the future performance of the Thoroughbred yearling also warrants further investigation. Copyright
Dissertation (MSc)--University of Pretoria, 2009.
Companion Animal Clinical Studies
unrestricted

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.

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

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

The objective of this study is to determine if fat as an energy source, and fiber in a pasture supplement will be beneficial when compared to a concentrate high in sugar and starch. In the first experiment, 12 pregnant and lactating mares were used in three different glycemic response tests to determine the effect of feeds on pregnant mares. The mares were fed a pelleted concentrate (PC) three months before foaling; after foaling they were divided into two groups and fed a feed high in sugar and starch (SS), or a feed high in fat and fiber (FF). The second experiment, used the same 12 mares (R mares) and 10 barren mares (B mares) in three different tests to determine the effects of the feeds, season and reproductive stage. A series of blood samples was collected via a jugular catheter from 0 to 390 min after consuming a meal. Glucose and insulin baseline and peak values, increments and areas under curves (AUC) were compared by ANOVA. For the first experiment, responses to PC did not differ between the two groups. Peak plasma glucose and insulin concentrations were higher in SS group than in FF during both early and late lactation. Glucose and insulin AUCs were higher in SS than in FF during both early and late lactation. In the second experiment, peak glucose increments had differences for the main effects feed, pregnancy and season, and interactions feed by pregnancy and feed by season. The glucose AUC values showed similar differences for the main effects and the interaction feed by pregnancy. Peak insulin increments had a difference for feed and pregnancy, but not the interactions. Insulin AUCs also revealed a difference between feed and pregnancy, and also for season, and the interaction feed by pregnancy. These results indicate that metabolic fluctuations are moderated by the replacement of sugar and starch with fat and fiber. This replacement may reduce the risk of certain digestive and metabolic disorders.
Master of Science

Dissertation (PhD(Agric))--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: This study was carried out to investigate whether environmental and/or genetic factors had an effect on the incidence of epistaxis related to exercise-induced pulmonary haemorrhage among racehorses in Southern Africa. A further aim was to estimate the heritability of liability to epistaxis in the Southern African Thoroughbred population. For the purpose of the environmental study, the data covering the period 1986-2001 and involving a total of778 532-race runs, were analysed. This included the following race start information: date of race (day/month/year), age, sex, breeder, trainer, distance, jockey, state of going, weight carried, centre of racing and altitude. The genetic part of the data was two-fold in nature and included firstly the analysis of all horses that suffered epistaxis whilst racing in Southern Africa from 1986 to 2001 and involving 1118 individual bleeders. The second genetic analysis included the same Southern African population plus those Southern African horses exported to Mauritius and then being recorded as bleeders in that country (1252 bleeders in total). Pedigree data covering the period 1960-1986 was used as required to calculate the incidence of bleeding amongst ancestors of the post 1986 era. Only pedigrees of horses that raced were included in this study as it was not possible to predict whether non-runners would have bled had they raced. Consequently all non-runners and also those that raced overseas in countries where bleeding occurrence was not recorded were excluded. Veterinarians employed by the Jockey Club suspended officially recorded horses that showed epistaxis as demonstrated by frank bleeding from the nostrils after racing. Oncourse endoscopy is not employed as a routine on any of the Southern African racetracks. In the environmental study epistaxis was identified in 1 287 race starts (0.165%). Epistaxis related to exercise-induced pulmonary haemorrhage was significantly (p<0.001) associated with altitude, age, race year, month and the day of racing. More horses demonstrated epistaxis at sea level than at altitude, between the months of May - October than the rest of the year, in older horses than in horses less than three-years old, after 1995 than between the years 1986 and 1995, and on Fridays and Sundays than on any other week day. No association could be established between epistaxis and breeder, trainer, distance, jockey, state of going, sex and weight carried. The heritability of liability method as described by Falconer (1989) was used to estimate the relative importance of heredity and environment. For the period investigated, the population incidence for epistaxis in Southern African horses was 2.1%. The estimation of heritability ofliability showed that first-degree relatives had a figure of 55.4%. The heritability of second- and third degree relatives were 41.3% and 30.4% respectively. The data investigated depicts horses that bled almost exclusively on race days as only a small percentage (- 5%) was reported as having bled during exercise. Accordingly, the full extent of epistaxis amongst racing Thoroughbreds in Southern Africa is difficult to gauge. Pedigree and race run data from Thoroughbreds racing in Southern Africa, covering the period 1986-2002 (63 146) horses in pedigree data-set and 778 532 race runs, were further analysed in order to study genetic and environmental factors affecting the incidence of epistaxis as associated with EIPH (exercise-induced pulmonary haemorrhage). As fixed effects for the model, variables that were tested significantly in a preliminary data analyses, were included. Various combinations of such variables namely age, weight, altitude, sex, month and going were tested. Fixed effects that were included in the fmal model were gender, going and altitude. The heritability estimates from a logit transformed analysis for epistaxis fitting both the animal and sire generalized mixed models were 0.23 and 0.40 respectively, which indicated that epistaxis as associated with EIPH in the Southern African Thoroughbred sires has a strong genetic basis. Genetic trends indicating an increase in epistaxis were also found. It is concluded that the frequency of epistaxis related to pulmonary haemorrhage is associated with altitude, winter and spring months and the horse's age. It is suggested that racing at a lower altitude may increase the probability of exercise-induced pulmonary haemorrhage. It is clear that epistaxis in the racing Thoroughbred has a strong genetic basis. It is further suggested that horses showing frank bleeding from the nostrils after racing or exercise, be suspended and not used for breeding purposes. This would result in relatively fast progress being made towards eradicating this costly scourge of the modem Thoroughbred racehorse. Affected stallions and those racing whilst being treated with furosemide, should be barred from breeding and not be considered as future sires. Estimated breeding values for epistaxis should be used as a tool for selecting against it and be considered in breeding programmes to decrease the incidence thereof.
AFRIKAANSE OPSOMMING: 'n GENETIESE ANALISE VAN DIE VOORKOMS VAN LONGBLOEDING IN DIE SUID-AFRIKAANSE RENPERD: Die doel met hierdie studie was om vas te stelof omgewings- of genetiese faktore enige invloed op die voorkoms van longbloeding in die Suid-Afrikaanse renperd het. 'n Verdere doelstelling was om die oorerflikheid op die onderliggende verspreiding van longbloeding in die Suid-Afrikaanse Volbloedpopulasie te bepaal. Vir die omgewingstudie is data wat oor die periode 1986-2001 strek en wat 'n totaal van 778 532 wedren-deelnames ingesluit het, statisties ondersoek. Die data het die volgende inligting ingesluit: datum van deelname, ouderdom, geslag, teler, afrigter, afstand van wedren, jokkie, toestand van baanoppervlakte, gewig gedra, sentrum waar deelname plaasgevind het en die hoogte bo seespieël van die sentrum. Die studie van die genetiese aspekte het eerstens 'n analise van al die perde wat longbloeding tydens 'n wedren in Suider-Afrika gedurende die jare 1986-2002 ondervind het (I118 perde), en tweedens dieselfde populasie perde, plus die Suiderlike-Afrikaanse perde wat uitgevoer is na Mauritius en bloeding daar ondervind het, (1252 perde), ingesluit. Ter aanvulling is uitgebreide stamboomdata van voorouers gedurende 1960-1986 gebruik om die voorkoms van longbloeding tydens die post 1986 tydvak te bepaal. Slegs stambome van renperde wat aktief aan renne deelgeneem het, is in die data ingesluit aangesien dit nie moontlik was om te voorspel of 'n perd wat nooit aan wedrenne deelgeneem het nie, longbloeding sou ondervind indien dit wel deelgeneem het. Dus is alle renperde wat nooit aan wedrenne deelgeneem het, asook daardie perde wat in die buiteland deelgeneem en waar longbloeding nie aangeteken word nie, uitgesluit. Alle perde wat bloeding van die neus na wedrenne getoon het, is deur veeartse in diens van die Jokkie Klub van Suid-Afrika ondersoek, as 'n bloeier aangeteken en van verdere deelname aan wedrenne geskors. Endoskopie word op geen van die Suid- Afrikaanse renbane as 'n standaard praktyk na wedrenne uitgevoer nie. Longbloeding het in 1 287 perde of gedurende 0.165% van alle wedrenne plaasgevind. Longbloeding soos geassossieer met EIPH, (exercise-induced pulmonary haemorrhage), is betekenisvol (p<0.001) met hoogte bo seespieël, ouderdom, dag van deelname, maand, en jaar verbind. Meer perde het longbloeding by seevlak in vergelyking met hoër vlakke bo seespieël ondervind, tussen die maande Mei-Oktober as die res van die jaar, in perde ouer as drie-jaar, na 1995 as tussen die jare 1986-1995, op Vrydae en Sondae as enige ander dag van die week. en meer by reuns as by merries of hingste. Geen verwantskap kon tussen bloeding en teler, afrigter, afstand, jokkie, toestand van baan, geslag en gewig gedra, gevind word nie. Die oorerflikheid op die onderliggende verspreiding vir longbloeding soos omskryf deur Falconer (1989), is gebruik om die relatiewe belangrikheid van oorerflikheid en omgewing te bepaal. Vir die periode bestudeer, was die voorkoms van longbloeding in die Suid-Afrikaanse renperd 2.1%. Die oorerflikheid van longbloeding was 55.4% vir eerste-graadse verwantes. By tweede-graadse verwantes was die ooretlikheid 41.3% en by derde-graadse verwantes 30.4%. Die data wat ondersoek is, was bykans uitsluitlik die van perde wat tydens wedrenne gebloei het en slegs 'n baie klein persentasie (~ 5%) was aangeteken as perde wat tydens oefening gebloei het. Dus is die volle omvang van longbloeding in Suider-Afrikaanse Volbloedperde moeilik om akkuraat te bepaal. Die stamboom- en wedrendata van Suid-Afrikaanse Volbloedperde is verder ontleed in 'n poging om die genetiese en omgewingsfaktore se invloed op die voorkoms van longbloeding, soos geassosieer met EIPH te bepaal. As vaste effekte vir die model is veranderlikes wat betekenisvol gevind was, ingesluit. Verskeie kombinasies van hierdie veranderlikes soos ouderdom, gewig, hoogte bo seespieël, geslag, maand en toestand van die baan is ingesluit. Die vaste effekte wat in die finale model ingesluit is, was geslag, toestand van die baan en hoogte bo seespieël. Die beraamde oorerflikheid verkry vanaf 'n "logit" getransformeerde analise vir longbloeding wat beide die diere- en vader- gemengde model gepas het, was onderskeidelik 0.23 en 0.40, wat 'n aanduidending is dat longbloeding, soos geassosieer met ElPH, 'n sterk genetiese grondslag het. Genetiese tendense het ook gedui op 'n toename in die voorkoms van longbloeding, veraloor die laaste vyf jaar van die studie. Samevattend is die bevinding dat die frekwensie van longbloeding 'n betekenisvolle verwantskap toon met hoogte bo seespieël, winter en lente maande en die perd se ouderdom. Dit word voorgestel dat renperde wat deelneem aan wedrenne by laer vlakke van hoogte bo seespieël, meer onderhewig aan longbloeding sal wees. Uit die resultate verkry is dit duidelik dat longbloeding 'n genetiese grondslag het. Dit word voorgestel dat perde wat fisiese simptome van neusbloeding na of gedurende wedrenne toon, geskors word van verdere deelname en ook nie toegelaat word om mee te teel nie. Hierdie maatreëls behoort aanleiding te gee dat relatief vinnige vordering gemaak sal word in die strewe om hierdie ongewenste sindroom in die moderne Volbloed te verminder. Aangetaste hingste, asook die wat aan wedrenne deelgeneem het terwyl hul behandeling ontvang met furosemide, moet nie toegelaat word om te teel en nie as toekomstige teelhingste oorweeg word nie. Die waarde van voorspelde teelwaardes vir longbloeding moet nie onderskat word in seleksie daarteen nie en moet in teelprogamme om die voorkoms daarvan te verminder, oorweeg word.

The Thoroughbred racehorse is capable of maintaining speeds of approximately 17 m/s for distances of over a mile. This represents an average speed and the Thoroughbred can reach speeds in excess of 20 m/s over short distances. The present series of studies was undertaken to investigate further the metabolic response to high-intensity exercise in the Thoroughbred racehorse. Unlike man, high-intensity exercise in the horse results in an increase in packed cell volume. This in turn causes acute changes in the colligative properties of blood and plasma. The changes in these properties were investigated and the effect on calculation and distribution of metabolites in blood and muscle was determined. The horse has a high capacity for lactate production compared to man and existing methodology for the assessment of muscle buffering capacity in biopsy samples was further developed and investigated. The horse was found to have a significantly higher muscle buffering capacity compared with man and it was calculated that this could be explained wholly on the basis of the higher muscle carnosine content in the horse. The metabolic response to high-intensity exercise was investigated using several exercise models, including single and multiple field gallops and treadmill exercise. A consistent finding was that high-intensity exercise in the Thoroughbred racehorse was nearly always accompanied by a reduction in muscle ATP content. The nature of the ATP decrease was further investigated using a treadmill exercise model. Muscle ATP decrease was found to occur at a particular exercise intensity rather than show a gradual decrease with increasing intensity. The intensity at which muscle ATP content began to decline significantly varied between individual horses, but in each case appeared to coincide with muscle lactate contents of approximately 70 mmol/kg dry muscle. The significance of the decline in ATP is discussed.

This thesis examines the effects of selective breeding practices on the Thoroughbred horse population. The Thoroughbred horse breed was founded in the 18th century and the studbook has been closed since 1791, resulting in contemporary Thoroughbred horses being the result of many generations of inbreeding for the intensive selection of athletic performance. Selective breeding can result in genetic improvement through increasing the frequency of variants pertaining to desirable traits and may also potentially remove harmful alleles from a population. However, an increasing body of evidence has shown that many domestic animal populations harbour high levels of deleterious variants as a result of population bottlenecks and low effective population sizes from selective breeding practices. Until now, no studies have reported the effects of these breeding practices on the Thoroughbred horse population. The findings of this thesis provide important insights into the effects of selective breeding on genetic load and genetic gain in the Thoroughbred horse population. These insights can be used to assist breeding decisions in Thoroughbreds to increase genetic improvement in the population. The findings of this thesis not only have important economic implications for one of the largest domestic animal populations in the world, but also have the potential to improve welfare standards in an industry under increasing scrutiny. More broadly, this thesis provides insights into the effects of selection, inbreeding and population bottlenecks on the health and fitness of domestic breeds. The methods used in this thesis can be applied to other animal populations to improve breeding and population management decisions.

Radiographic examination of Thoroughbred racehorses at the time of the yearling sales is common practice in South Africa. Although it is generally accepted that yearlings will have some radiographic changes, there is only one study that estimated the prevalence of these changes in Thoroughbred racehorse yearlings in South Africa. Furniss et al reported on the occurrence of radiographic abnormalities over a one-year period (Furniss 2011). Furniss et al. study differs from other studies in that there was a higher prevalence of palmar metacarpophalangeal and plantar metatarsophalangeal osteochondral fragments and a lower prevalence of pedal osteitis, dorsal osteochondral fragmentation of the metatarsophalangeal joint, distal metacarpal saggital ridge changes, ulnar carpal bone lucencies, carpal osteophytes, distal intertarsal and tarsometatarsal joint changes, tarsal osteochondrosis lesions and stifle osteochondrosis lesions was found. This study will further assist practitioners to identify joints where the most prevalent changes are likely to occur. Our objective was to describe the prevalence and distribution of radiographic changes in the metacarpophalangeal joint, metatarsophalangeal joint, carpi, tarsi, stifle and fore digits of racing Thoroughbred yearlings in South Africa when examined as part of a pre-purchase examination during the Annual National Yearling Sales extending from 2008 through 2010. Thoroughbred racehorse yearlings were subjected to radiographic evaluation including the digit (n= 566 ), metacarpophalangeal joint (n=566 ), metatarsophalangeal joint (n= 566), carpi (n= 566), tarsi (n= 566) and stifle (n=566 ). The radiographic changes were categorised by location and type of change present for each series. The digit Where informal comparisons with previously published data can be made, similar changes of pedal osteitis were recorded in this study, with a total percentage of 6.7%. There was an 8.7% prevalence of inversion of the third pedal bone. Other studies describing radiographic changes in Thoroughbred racehorse yearlings did not investigate inversion of the third pedal bone, therefore results cannot be compared. The metacarpophalangeal and metatarsophalangeal joints with proximal The metacarpophalangeal and metatarsophalangeal joints with proximal sesamoid bones The prevalence of dorsoproximal phalanx one fragmentation (1.2%) of metacarpophalangeal joints were similar compared to other studies. Osteochondral fragmentation of proximal plantar phalanx one (6%) was 8.5 times more prevalent when compared to proximal palmar phalanx one (0.7%). The latter prevalence is in agreement with similar studies. There were low incidences of subchondral cyst-like lesions seen in distal third metacarpus (0.4%), distal third metatarsus (0.2%) and proximal first phalanx, similar to other studies. The most common change recorded on the dorsal aspect of distal third metacarpus and metatarsus was a well-defined semi-circular notch (dorsal aspect of distal third metacarpus 20.3%; dorsal aspect of distal third metatarsus 27%) similar to other studies. Our study showed a higher prevalence of lucencies present at dorsal aspect of distal third metacarpus (8.5%) and metatarsus (4.2%) compared to other studies. There was a marked lower prevalence in the current study of flat distal palmar third metacarpal condyles (6%). Prevalence of palmar and plantar third metacarpal and metatarsal supracondylar lysis were markedly higher in the present study. Slight palmar and plantar third metacarpus and metatarsus supracondylar lysis was seen in 19.3% of the horses. Moderate to extreme palmar and plantar third metacarpus and metatarsus supracondylar lysis were present in 10.2% of the horses. The carpi There was a higher prevalence of dorsomedial carpal disease in our study population (11.3%) and prevalence of carpal osseous cyst-like lesions such as a circular lucency in ulnar carpal bone was lower (14%). A markedly higher prevalence of 4.2% in carpal osteochondral fragmentation was found. The tarsi Osteochondrosis of the tarsocrural joint showed a similar prevalence (13.4 %). Degenerative joint disease of tarsometatarsal joint had a higher prevalence (36%) than the centrodistal (distal intertarsal) joint (20.3%). There was also a higher incidence of degenerative joint disease in tarsometatarsal joint (36%). The stifle In the current study, osteochondrosis of the stifle had a similar prevalence (3.6%) when compared to other studies. 6 Conclusion In South Africa Thoroughbred racehorse yearlings, radiographic changes most commonly involved the metacarpo- and metatarsophalangeal joints, carpi and tarsi. This study revealed markedly higher prevalence of palmar and plantar third metacarpal and metatarsal supracondylar lysis (slight 19.3% and moderate to extreme 10.2%), carpal osteochondral fragmentation (4.2%) and degenerative joint disease in tarsometatarsal joint (36%). Establishment of normal prevalence and distribution of radiographic changes in South Africa Thoroughbred yearlings will allow for comparison with populations of young horses worldwide. Knowledge of the normal prevalence will assist veterinarians to identify joints in which radiographic changes are most likely to occur.
Dissertation (MSc)--University of Pretoria, 2013.
gm2014
Companion Animal Clinical Studies
unrestricted

Gene doping, the misuse of gene therapy for performance enhancement, is predicted to be the next phase of doping faced by horseracing. Since 2003, the World Anti-Doping Agency has included gene doping on the list of banned practices in human sports and has several expert teams developing detection methods. The threat of gene doping to the integrity of horseracing and welfare of horses has been discussed by members of The International Federation of Horseracing Authorities and others in the anti-doping community for over ten years. In this thesis, a method is developed for direct detection of transfer DNA (T-DNA) in equine blood samples. The method uses real-time polymerase chain reaction (RT-qPCR) to target unique ‘foreign’ sequences in T-DNA. Ten RT-qPCR assays were developed targeting T-DNA for five equine genes predicted to be high priority equine gene doping targets. Based on standard practice in horseracing drug analysis, the gene doping test consists of two stages, screening and confirmation. To increase sample throughput in the screening stage, assays for four gene targets were optimised and validated as a multiplex suite. The assays were optimised and validated using two in vitro systems that mimic positive doping samples. This work develops the entire doping detection test from sample collection to confirmation of a positive sample. The developed method detected as few as 300 copies of T-DNA per millilitre of blood, comparable to tests developed for human gene doping detection. In a world-first for gene doping surveillance, the developed gene doping test was used to screen real samples for Racing NSW as part of out of competition surveillance prior to the Sydney Autumn Racing Carnival 2018. The results showed that gene doping detection is feasible using the method developed in this project. The test developed here will be directly applicable to all breeds of horses involved in both racing and other athletic competition.

The purpose of this research was to study vitamin A status in grazing horses throughout the year and to evaluate the effectiveness of vitamin A and β-carotene as supplements. Vitamin A status was assessed by serum retinol concentrations (SR) and the relative dose response (RDR) which was adapted for use in the horse. The horses (45 Thoroughbred mares) were divided into three diet groups: pasture and hay only (PH); pasture, hay and vitamin A-free concentrate (PHC); and hay and vitamin A-free concentrate (HC). The mares, as well as their foals, were assessed for vitamin A status during the summer, fall and winter. After eight months, each diet group was subdivided and supplemented with either: retinyl palmitate at two times the recommended level (A), the equivalent in water dispersible β-carotene (B), or a placebo (C). Supplementation continued for 20 months during which the vitamin A status was assessed every 60 days in the mares, and at birth in the neonates. During both the depletion and the repletion phase the mares were kept on a regular breeding schedule and the reproductive rates were determined as well as the general health of the mares and their offspring. The RDR proved more sensitive at detecting changes in vitamin A status than SR, and a combination of both was used. A measurable decline in vitamin A stores was seen in the HC group within 2 months, and in PH and PHC groups during the winter. The HC group remained lower in vitamin A status throughout the study. A seasonal fluctuation of vitamin A status was observed regardless of supplementation. Supplementation with retinyl palmitate improved vitamin A status in all three diet groups, however, supplementation with β-carotene did not. Both neonates and young growing horses were lower in vitamin A status than the adult. A respiratory infection observed in the weanlings affected vitamin A status as well. Supplementation of the dam had no effect on neonatal vitamin A status. Deleterious effects on reproductive rates and health were also observed with vitamin A depletion. Supplementation of β-carotene had a negative effect on reproductive rates in this study.
Ph. D.

Two times are critical for the horse ¾ the first few days of its life and the last few moments of a race. Vitamin E is critical in regard to immune competence in the first and antioxidant status in the latter. Studies conducted at the Middleburg Agricultural Research and Extension (MARE) Center include the development of horse feeds that replace sugar and starch with fat and fiber. The previous fat source of the pasture supplement under development was corn oil, which contains much vitamin E, was replaced with a cereal by product, which contains relatively little. Vitamin E has been studied in horses to a limited degree but not in grazing Thoroughbreds, thus the MARE Center gave me the opportunity to study vitamin E in Thoroughbred mares and foals. Middleburg is located in the Blue Ridge Mountains on Northern Virginia close to the site of one of the toughest endurance races in the world. This allowed me the opportunity to study vitamin E and antioxidant status in the horse during endurance racing. Initial studies of vitamin E supplementation to mares during the last trimester of gestation were disconcerting with no changes in serum concentrations of a-tocopherol (vitamin E). Studies conducted during the post-partum period revealed evidence of responses to vitamin E supplementation, as increased a-tocopherol concentrations were observed in mares' milk and in foal serum. Foals are born with virtually no circulatory antibodies and the supplementation of a synthetic form of vitamin E to mares demonstrated an increased passive transfer of immunoglobulins to foals. Natural vitamin E has shown a greater bioavailability than synthetic forms, in other species and was tested here at the MARE Center on mares. A greater passive transfer of immunoglobulins was observed with natural vitamin E supplementation compared with the synthetic forms, with immunoglobulin M concentrations in foal serum remaining higher for a longer period after birth compared to foals of non-supplemented mares. The transfer of a-tocopherol via the milk was also increased in concentration and duration in mares supplemented with natural vitamin E. Bioavailability of five oral forms of vitamin E (3 natural and 2 synthetic) were tested and one natural form was also administered intravenously so that clearance of vitamin E could be used to calculate the efficiency of absorption of the oral forms. Efficiency of absorption for oral treatments was not determined because of the slow turnover time of the intravenously administered vitamin E, which confounded all subsequent baseline serum a-tocopherol concentrations. Of the salvageable data, serum a-tocopherol concentrations were higher in grouped treatments at 9 and 12 h post dosing. Lipid fractions revealed possible insufficient absorption of the oral doses of vitamin E and possibly tissue saturation following intravenous doses of vitamin E. Serum concentrations of a-tocopherol were generally higher following natural forms of oral vitamin E administration. As vitamin E is the most important antioxidant in cells, it is often supplemented to endurance horses competing in 80 and 160 km races. Vitamin E protects lipid cell membranes from peroxidation by free radicals, which are increased during strenuous exercise resulting in oxidative stress. The antioxidant status of horses is severely tested during endurance racing and so a study was conducted to monitor changes in circulating antioxidants during three endurance races. Interesting novel findings in the horse were the maintenance of serum a-tocopherol and the depletion of erythrocyte glutathione and plasma ascorbate during two 80 km and one 160 km races. Associations were found between increased muscle cell enzyme leakage and decreased antioxidant status during endurance exercise and although associations do not prove a causation of oxidative stress, they do provide motivation to search for a cause and it is tempting to propose that oxidative stress damaged muscle cell membranes in endurance horses. Further, these findings propose a connection between muscle cell damage and a new form of exertional rhabdomyolysis (ER) that has been observed in endurance horses, where oxidative fibers are damaged compared to the typical glycolytic fiber damage associated with known forms or ER. An increased understanding of vitamin E utilization in the horse will improve the health and welfare of all horses, but especially newborn foals and the athletic endurance horses.
Ph. D.

This thesis is concerned with equine attachment as a form of interspecies fictive kinship, in relation to the practices, social relations, and motivations of participant groups within the Canterbury thoroughbred racing industry. Exploring the interconnections between intimacy and investment, as both financial and emotional commitments, the different sectors of the industry are analyzed as actor-network assemblages in which boundaries between professional, economic, and social relations are porous. The thesis argues that the parameters of a distinct equine community are delineated through regulated forms of haptic access. Distinctions regarding those who are and are not permitted to touch horses, articulates with a regime of risk regulation, which is more broadly explored in its physical, social, financial, and emotional dimensions. Also integral to the character of this networked community of practitioners is the symbolism of naming and branding thoroughbreds, as well as the secular rituals of the auction and the race-day. Conceived as a naturalcultural phenomenon, the race is analyzed in terms of the cross-species meanings and experiences of jockeys and apprentices, who are understood as representatives of an occupational sub-culture. Finally, this thesis also explores the preponderance of women in South Island racing; charting the path by which they have successfully adopted traditionally male-dominated roles.

Master of Agribusiness
Department of Agricultural Economics
Christine Wilson
Over the last decade, the United States horse industry has seen a decline in all segments of the industry. Both people and organizations within and outside the industry have debated the cause of this decline, with the 2007 horse slaughter ban being at the center of this debate. The purpose of the report is to analyze a specific segment of the industry to determine what has led to this decline over the last decade. To do this, we will look specifically at the total number of thoroughbreds sold over a thirty-year history, and using regression analysis, determine if a controversial bill that banned the slaughter of horses in the United States for the purpose of meat was the cause of this decline or if other key variables that played a key role. These additional variables will include hay prices, corn prices, oat price, gas prices, and a macro economic indicator variable. The regression results show that the horse slaughter ban did in fact have an impact on the decline of the total number of thoroughbreds sold within this specific segment of the industry. Also, both hay and the unemployment rate had an effect on the decline of the total number of thoroughbreds sold, while gas prices appear to have had an unexpected positive effect, which is contrary to common thought. This thesis shed a new light on the decline of the horse industry within the United States and the effect the ban has had on the thoroughbred industry.

Thesis (Ph. D.)--University of Oregon, 2007.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 194-203). Also available for download via the World Wide Web; free to University of Oregon users.

The horse's enormous respiratory reserve enables it to increase the respiratory load on the lungs many fold during exercise, hence low-grade respiratory disease is difficult to detect at rest, although of vital importance during heavy exercise. Diagnostic exercise testing is, therefore, of great interest and this thesis describes its application to the investigation of respiratory disease in the Thoroughbred horse. Horses were exercised on a treadmill whilst respiratory flow rates were recorded using ultrasound flow transducers, respired gas concentrations measured by mass spectrometry and blood gas analysis performed. The exercise test involved a warm up followed by two minute canters/gallops at increasing workloads separated by ten minute walks. Validation studies confirmed the suitability of the methods for these studies. A steady state for respiratory variables was reached by ninety seconds of canter/gallop. The effects of training on exercising respiratory function were investigated by exercise testing horses following a sedentary period and after a fifteen week training programme. State of training did not complicate clinical interpretation of some variables, e.g tidal volume, respiratory frequency and minute ventilation, whilst peak flow rates were stable at the highest workloads. Arterial oxygen tension and blood pH during exercise were affected by training but other blood gas variables and end-tidal gas tensions were not. The effect of influenza on respiratory function was studied by challenging partially immune horses with H3N8 influenza, inducing infection similar to that seen in vaccinated racehorses. Twenty one days after infection most horses showed no changes in respiratory function but 2/9 horses altered breathing strategy during canter and another showed altered acid-base and blood lactate responses. Horses with low-grade respiratory disorders showed differences in respiratory function to the experimental animals but the wide normal range of pulmonary function tests limited their one-off diagnostic value. Serial testing may prove to be a more sensitive method.

Doctor of Philosophy
The aim of this research was to describe the epidemiology of musculoskeletal (MS) injuries in two- and three-year-old Thoroughbred racehorses. A 27 month longitudinal study commencing in May 2000 was conducted. The study convenience sampled 14 trainers with facilities at metropolitan and provincial racetracks in New South Wales, Australia. In the 2000/01 and 2001/02 racing season, 323 and 128 two-year-olds, respectively, were enrolled in the study. The 451 Thoroughbred horses contributed, 1, 272 preparations and 78, 154 training days to the study. Of the 323 horses enrolled in the 2000/01 racing season, 219 contributed three-year-old data to the study. During the study period 8%, of training days had missing training data and 3% of the 1, 986 starts in the races or barrier trials were incorrectly recorded. The rate of incorrect entries varied with both study month and trainer. Similarly, the rate of training days with missing data varied between trainers and with study month. Four hundred and twenty-eight MS injuries were recorded in association with 395 preparations in 248 two- and three-year-old Thoroughbred racehorses. The IR for all categories of MS injuries, except for tendon and ligament injuries, were higher in twoyear- olds than three-year-olds, although the differences were only significant for shin soreness. Seventy-eight percent of horses enrolled in the study started, in a barrier trial or race, within one year on entering the study. After accounting for other confounders, horses that had sustained a MS injury were 0.50 times less likely to start, in a race or trial, race than those that did not sustain an injury. Seventy percent of horses returned to training after their first MS injury, and the cumulative percentage of these horses that had recovered within six months of the initial MS injury was 55%. After adjusting for clustering at the level of the trainer, the analysis showed that horses that exercised at a gallop pace ≥ 890 m/minute (but had not started in a race) prior to the onset of MS injury, were 2.14 times more likely to recover than horses whose maximum speed, prior to the onset of the first MS injury, was less than 890 m/minute. Similarly, horses that had started in a race or barrier trial were 4.01 times more likely to recover than horses whose maximum speed was less than 890 m/minute. 8 Training days were grouped into units referred to as preparations. A preparation began on the day that the horse was enrolled in the study, or when a horse returned to training after an absence of more than seven days from the stable. The preparation continued until the horse was lost to follow-up or left the stable for a period of more than seven consecutive days. Univariable and multivariable analytical methods were used to examine the association between a range of independent variables and four preparationlevel measures of performance: (i) the duration of preparations, (ii) length of time from the beginning of the preparation until the first start in a race or barrier trial, (iii) length of time from the first start until the end of the preparation and (iv) rate of starts in races or barrier trials. After adjusting for confounders, younger horses tended to have shorter preparations, took longer to start in a race or barrier trial, had a shorter interval from the first start to the end of the preparation and fewer starts per 100 training days. MS injury was not conditionally associated with any of the outcomes considered in this chapter. Multivariate statistical models were used to explore risk factors for MS injuries. The results suggest that MS injuries involving structures in the lower forelimb (carpus to fetlock inclusive) could be reduced by limiting exposure to high-speed exercise. This supports the proposition that training injuries are caused by the accumulation of micro damage. The results suggest there are a number of other factors that vary at the trainer level that may be risk factors for injuries, in particular joint injuries. These include unmeasured variables such as the rate of increase in distance galloped at high-speed, conformation of the horse, skill of the riders and farrier and veterinary involvement.

Microhistological analysis is a highly effective microscopic technique of determining botanical composition of animal diets by visual recognition of fecal plant fragments, and has been widely used in range studies. The objective of this study was to use microhistological techniques to predict the botanical composition of domesticated horse diets when grazing mixed cool-season pasture. Samples of tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire], Kentucky bluegrass (Poa pratensis L.) and orchardgrass (Dactylis glomerata L.) were evaluated for microscopically unique characteristics. Cool season pasture grazing studies were conducted in October 2006 and May 2007 in Lexington, KY. Eight thoroughbred mares were placed in individual paddocks of varying botanical compositions to graze for six days. For each percent increase of tall fescue or orchardgrass in the paddock, there was a corresponding increase of 0.44% and 0.42%, respectively, in the diet. In conclusion, microhistological analysis is a useful tool for determining botanical composition of horse diets when grazing cool season grass pastures.

The aim of this study was to evaluate temperature data collected from Thoroughbred foals between birth and shortly after weaning. It provides a valuable survey with epidemiological conclusions providing insight into the temperature trends and pyretic occurrences of Thoroughbred foals during this age period. Temperature data were collected using telemetry from temperature sensitive microchips implanted into newborn foals. The system of inputting and storing temperature data was completely electronic and this study evaluated this system. It was found that this system was stable and allowed the evaluation of large amounts of frequently acquired data with little human intervention. The data obtained resulted in the valuable evaluation of age associated body temperature trends within the foals as well as providing an indication of the extent and epidemiology of pyrexia within the study cohort. The system of evaluating temperatures based both on the individual day value as well as on each individual foals prior series of temperatures shows that the use of these two criteria can be utilised simultaneously. The study provides basic information which future researchers using similar systems can use to objectively set criteria for pyrexia. An outbreak of equine encephalosis also occurred during the study period and this provided much needed prospective epidemiological information for such an outbreak, something which has not previously been documented. Copyright
Dissertation (MSc (Veterinary Science))--University of Pretoria, 2009.
Production Animal Studies
unrestricted

Diets rich in hydrolyzable carbohydrates induce a hyperglycemic/insulinemic response and may increase the incidence of metabolic disorders associated with some types of laminitis, exertional rhabdomyolysis and osteochondrosis in horses. This study applied the minimal model of glucose and insulin dynamics to determine the effect of diet on metabolites and hormones that regulate glucose metabolism in young horses. Twelve Thoroughbred foals were raised on pasture and supplemented twice daily with a feed high in either sugar and starch (SS) or fat and fiber (FF). As weanlings (age 199 ± 19 d, weight 274 ± 18 kg), the subjects underwent a modified frequent sampling intravenous glucose tolerance test during which they remained in stalls and had access to grass hay and water ad libitum. Samples were colleted at -60, -45, 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 14, 16, 19, 22, 23, 24, 25, 27, 30, 35, 40, 50, 60 , 70 , 80, 90, 100, 120, 150, 180, 210, 240, 270, 300, 330 and 360 min with a glucose bolus of 300 mg/kg BW at 0 min and an insulin bolus of 1.5 mU/kg BW at 20 min. Plasma was analyzed for glucose, insulin, growth hormone (GH) and insulin-like growth factor-I (IGF-I) concentrations. Insulin sensitivity, glucose effectiveness, acute insulin response to glucose and disposition index were derived using Minmod Millennium and WinSAAM software. Diet groups were compared using the non-parametric Kruskal-Wallis test or the sign test. Time interactions were compared using a mixed model with repeated effects. Rank-ordered linear regression was used for correlations. Basal glucose did not differ between groups (P = 0.75). There was nearly a trend towards higher basal (P = 0.11), and median insulin was higher in the sugar and starch foals at all 36 sample points (P = 0.030). The basal glucose:basal insulin ratio for the sugar and starch supplemented foals was lower than for fat and fiber foals (P = 0.025). Insulin sensitivity (SI) was lower in foals fed sugar and starch than foals fed fat and fiber (P = 0.007). Acute insulin response to glucose was directly correlated to weight (r = 0.78; P = 0.003) and inversely correlated with SI (r = -0.55; P = 0.067). The glucose:insulin ratio was directly correlated to SI (r = 0.92; P < 0.001). Growth hormone concentrations were increased from basal from 19 to 180 min after the glucose dose (P < 0.05). Basal IGF-I was higher (P = 0.006) in the SS group compared to the FF group. Concentrations of total IGF-I increased with time (P = 0.002) in the SS group. The change in IGF-I concentration from baseline to the end of the study was positively correlated (r = 0.72; P = 0.008) to the area under the insulin curve from 0 to 80 min. Basal IGF-I was inversely correlated to SI (r = 0.71; P = 0.015). These results show that the metabolic response to a diet high in hydrolyzable carbohydrates differs from the response to a fat and fiber meal resembling forage. Weanlings adapted to meals high in glucose equivalents have higher insulin and IGF-I secretion as compared to foals adapted to a fat and fiber feed, possibly contributing to lower insulin sensitivity observed in these foals. Such deviations may contribute to metabolic dysfunction and osteochondrosis in horses fed grain diets.
Master of Science

A capacidade aeróbica dos equinos atletas pode ser explica, em partes, pelo seu desenvolvimento cardíaco associado ao treinamento físico. O exame ecocardiográfico de equinos atletas permite a visualização destas alterações e da função cardíaca destes animais. Buscou-se avaliar ecocardiograficamente equinos de diferentes modalidades esportivas, para verificar se o tipo de atividade física desempenhada por cada grupo de animais promove diferenças estruturais ou funcionais cardíacas. 196 equinos foram submetidos à avaliação ecocardiográfica em repouso, sendo divididos em três grupos: grupo Polo, 44 equinos participantes de provas de Polo; grupo QM, 49 equinos da raça Quarto de Milha, participantes de provas de baliza e tambor, e grupo PSI, 103 equinos da raça Puro Sangue Inglês participantes de provas de corridas. Foram avaliados os seguintes índices cardíacos: SIV, DIVE e PLVE em sístole e diástole, AE em sístole, Ao em diástole, relação AE:Ao, FEj, VEj, VSFVE, VDFVE, FS%, E-S, TEVE, DC e FC. Os animais do grupo PSI apresentaram os maiores volumes de ventrículo esquerdo, tendo apresentado proporcionalmente menor eficiência quando analisado o VEj. Os animais do grupo Polo e QM apresentaram melhores valores quando analisadas as variáveis de função cardíaca. A atividade física mais intensa desempenhada pelos animais do grupo QM e Polo permitiu melhor desenvolvimento funcional do coração destes animais, tendo o grupo PSI, apresentado valores que sugerem que sua capacidade aeróbica ainda pode ser melhor explorada através de melhor orientação de seu treinamento físico.
The aerobic capacity of equine athletes may be explained, in part, by its cardiac development associated with physical training. Echocardiographic examination of equine athletes allows the visualization of these changes and cardiac function of these animals. We aimed to evaluate echocardiographically horses of different sports to see if the type of physical activity performed by each group of animals promotes structural or functional cardiac differences. 196 horses underwent echocardiography at rest were divided into three groups: Polo group, 44 horses participating in tests of Polo; QM group, 49 horses of Quarter Horse, participants of barrel and pole bending events and PSI group, 103 horses of the breed Thoroughbred racehorses. We evaluated the following heart rates: IVS, LVD and LVFW in systole and diastole, LA in systole, Ao in diastole, mean LA: Ao, EF, EV, LVFSV, LVFDV, FS%, E-S, LVET, CO and HR. The PSI group animals showed higher left ventricular volumes and provided proportionately less efficiency when we analyzed EV. Animals in group Polo and QM showed higher values when variables such as cardiac function. The more intense physical activity performed by the animals of group QM and Polo provided better functional development of the heart of these animals, and the PSI group, presented figures suggesting that aerobic capacity can still be better exploited through better targeting of their physical training.

This dissertation describes the epidemiological investigation and management of the first outbreak of Contagious Equine Metritis (CEM) reported in South Africa. In addition, the subsequent implementation of a nationwide quantitative polymerase chain reaction (qPCR)- based stallion screening programme and traceback of exposed animals to define the spread of CEM in South Africa is described. The first South African outbreak of CEM caused by the bacterium, Taylorella equigenitalis was reported on the 9th May 2011 to the World Health Organisation for Animal Health (OIE). The outbreak was recognized subsequent to the importation of a young Warmblood stallion from Germany. The outbreak initially appeared confined to a single index property (focus property), an equine breeding facility in Midrand, Gauteng, South Africa with a single confirmed case of transmission involving the index stallion and a Thoroughbred mare. The initial response was rapidly instituted following the suspicion of T. equigenitalis on the index property. This included an inspection of the index property and its records. A riskclassification of in-contact animals allocated them to “high,” “moderate” or “low”-risk categories. The classification was dependent on the temporal relationship of their presence on the index property relative to the period of residence of the index cases. After T. equigenitalis infection was confirmed from both index cases, the breeding facility was placed under state– administered quarantine and all exposed mares and the index cases were transferred to a quarantine facility. The animals were re-tested by genital swabbing for bacterial culture following a standard protocol according to internationally-accepted practice (OIE Terrestrial Manual on Contagious Equine Metritis). Additional duplicate swabs were obtained for real time qPCR. None of the mares were shown to be positive on either bacterial culture or qPCR. All animals were however treated according to an accepted protocol for T. equigenitalis infection (Luddy and Kutzler, 2010, UK Horseracing Betting Levy Board (HBLB) Code of Practice, 2011). All stallions that had been present on the index property and undergone semen collection on the same day as the index stallion were classified as “moderate risk” and were similarlytested. This identified two additional T. equigenitalis-positive stallions, which were confirmed on bacterial culture (World Organization for Health (OIE) Manual of Diagnostic Tests and Vaccines for Terrestrial Animals (Chapter 2.5.1, Contagious Equine Metritis version adopted 20/10/2011) and which were subsequently quarantined and successfully treated. Following recognition of this outbreak, the Department of Agriculture, Forestry and Fisheries (DAFF) in consultation with the Equine Research Centre (ERC) of the Faculty of Veterinary Science at the University of Pretoria promulgated a nationwide qPCR-based screening programme that aimed to establish the prevalence and distribution of T. equigenitalis in South Africa. This required certification of all South African stallions used for breeding either by natural cover or assisted reproductive techniques. The compliance for certification was based on submission of two sets of genital swabs that both tested negative for T. equigenitalis on qPCR-testing. The process was coordinated by a web-based platform (http://wto the prescribed World Organisation for Health (OIE) method (Terrestrial Manual on Contagious Equine Metritis). All stallions apart from one could be linked to the index property. As of 31st October 2013, two additional T. equigenitalis-positive females have been identified, following a traceback of all identified potentially-exposed mares and their offspring that was instituted in September 2012. An “exposed mare” was defined as a mare that had been bred, either by natural breeding or assisted breeding techniques to the index stallion or any other T. equigenitalis-positive stallion. These mares were distributed across five provinces of South Africa at the time the traceback was initiated. During the nationwide traceback, a subpopulation focus was identified when 24 of the 33 resident stallions at the South African Lipizzaner Centre, Midrand, Gauteng tested positive for T. equigenitalis. Six of these stallions had visited the index property for semen collection over the course of several years prior to the arrival of the index stallion. This suggested the possible albeit undetected presence of T. equigenitalis on these premises prior to the arrival of the first reported index case. We strongly suspected that there may have been undetected CEM incursions into South Africa in the past. The index case in this outbreak may either have introduced a new infection or was infected by a pre-existing source of infection subsequent to his arrival. It is hoped that future strain-typing of the isolates from the positive cases identified during this intervention will further clarify this scenario. The use of qPCR-based screening proved to be a highly specific and sensitive method for detecting T. equigenitalis and helped to define the distribution and prevalence of T. equigenitalis in breeding stallions and exposed mares in South Africa. In addition, this method had significant practical advantages with respect to the associated costs, turn-around times and in-the-field application when compared with bacterial culture. The institution of a web-based platform from which the national screening programme was launched and coordinated proved to be indispensable in managing stakeholder access and information availability. To date, 31st October 2013, a total of 39 horses (36 males and 3 females) have been identified as T. equigenitalis-positive and have all subsequently been successfully treated. © Universityww.cemsa.co.za) As of 31st October 2013, an additional 33 carrier stallions have been identified by this screening programme. Of these stallions, 23 have been confirmed on bacteriology according to the prescribed World Organisation for Health (OIE) method (Terrestrial Manual on Contagious Equine Metritis). All stallions apart from one could be linked to the index property. As of 31st October 2013, two additional T. equigenitalis-positive females have been identified, following a traceback of all identified potentially-exposed mares and their offspring that was instituted in September 2012. An “exposed mare” was defined as a mare that had been bred, either by natural breeding or assisted breeding techniques to the index stallion or any other T. equigenitalis-positive stallion. These mares were distributed across five provinces of South Africa at the time the traceback was initiated. During the nationwide traceback, a subpopulation focus was identified when 24 of the 33 resident stallions at the South African Lipizzaner Centre, Midrand, Gauteng tested positive for T. equigenitalis. Six of these stallions had visited the index property for semen collection over the course of several years prior to the arrival of the index stallion. This suggested the possible albeit undetected presence of T. equigenitalis on these premises prior to the arrival of the first reported index case. We strongly suspected that there may have been undetected CEM incursions into South Africa in the past. The index case in this outbreak may either have introduced a new infection or was infected by a pre-existing source of infection subsequent to his arrival. It is hoped that future strain-typing of the isolates from the positive cases identified during this intervention will further clarify this scenario. The use of qPCR-based screening proved to be a highly specific and sensitive method for detecting T. equigenitalis and helped to define the distribution and prevalence of T. equigenitalis in breeding stallions and exposed mares in South Africa. In addition, this method had significant practical advantages with respect to the associated costs, turn-around times and in-the-field application when compared with bacterial culture. The institution of a web-based platform from which the national screening programme was launched and coordinated proved to be indispensable in managing stakeholder access and information availability. To date, 31st October 2013, a total of 39 horses (36 males and 3 females) have been identified as T. equigenitalis-positive and have all subsequently been successfully treated.
Dissertation (MMedVet)--University of Pretoria, 2013.
gm2014
Production Animal Studies
unrestricted

Strategy is generally considered as one of the most important factors of organizations´ success. However, it can be supposed that this theory is applicable for all sectors. The diploma thesis focused on the perception of strategy, strategic planning cycle and its impact on the particular sports industry. This industry is Thoroughbred horse racing. The field of research was application of management theory in the particular horse racing club, its use and the impact on the clubs´ performance, which could lead to potential implementation of necessary changes. The research was conducted using qualitative approaches. Research was based on two pillar, in-depth interviews and participant observation. This approach increased the validity of the statements thanks the triangulation of sources. The findings discuss that the strategy seems to be unimportant for clubs´ managers, although they significantly work on some parts of the strategic planning cycle. However, this fact do not negatively affect the clubs´ performance. It is therefore desirable but not necessary, to make changes and create the strategy.

Parasite control is important to horse health and horse owners should feel highly concerned about the proper treatment of parasites. In the past 30 years, veterinary science has made important advances in treating parasites and provided new products and strategies to optimize treatment and prevention. However, horse owners and managers have been slow to adopt these new recommendations. This study investigates why the transition has not occurred as expected. It examines issues related to the decision-making process of horse owners and managers as they relate to deworming strategies. In addition, it investigates current deworming approaches as well as attitudes towards alternative parasite control strategies, and tries to describe the financial considerations corresponding to each strategy. To this end, a questionnaire was distributed to Thoroughbred farms in Kentucky. The first part of the questionnaire examined the actual approaches of farm managers and characterized the Kentucky Thoroughbred farms. Most farm managers appear to be concerned about drug resistance in parasites and incorporated veterinarian advice in defining their deworming program; however, almost three-quarters of them were still following the traditional rotational deworming program. Based on a conjoint experiment, we were able to evaluate the willingness-to-pay of farm managers for different attributes of a deworming strategy – time and effort spent, decrease in health risks, drug resistance in parasites, and price. The study showed that farm managers were willing to pay a premium for a strategy that is guaranteed “non-resistant” and that decreased health risk by 5%, while they expected a discount for a strategy that requires much time and effort.

The aim of this study was to examine whether a real high speed-short term competition influences clinicopathological data focusing on muscle enzymes, iron profile and Acute Phase Proteins. 30 Thoroughbred racing horses (15 geldings and 15 females) aged between 4-12 years (mean 7 years), were used for the study. All the animals performed a high speed-short term competition for a total distance of 154 m in about 12 seconds, repeated 8 times, within approximately one hour (Niballo Horse Race). Blood samples were obtained 24 hours before and within 30 minutes after the end of the races. On all samples were performed a complete blood count (CBC), biochemical and haemostatic profiles. The post-race concentrations for the single parameter were corrected using an estimation of the plasma volume contraction according to the individual Alb concentration. Data were analysed with descriptive statistics and the percentage of variation from the baseline values were recorded. Pre- and post-race results were compared with non-parametric statistics (Mann Whitney U test). A difference was considered significant at p<0.05. A significant plasma volume contraction after the race was detected (Hct, Alb; p<0.01). Other relevant findings were increased concentrations of muscular enzymes (CK, LDH; p<0.01), Crt (p<0.01), significant increased uric acid (p<0.01), a significant decrease of haptoglobin (p<0.01) associated to an increase of ferritin concentrations (p<0.01), significant decrease of fibrinogen (p<0.05) accompanied by a non-significant increase of D-Dimers concentrations (p=0.08). This competition produced relevant abnormalities on clinical pathology in galloping horses. This study confirms a significant muscular damage, oxidative stress, intravascular haemolysis and subclinical hemostatic alterations. Further studies are needed to better understand the pathogenesis, the medical relevance and the impact on performance of these alterations in equine sport medicine.

The aim of this study was to examine whether a real high speed-short term competition influences clinicopathological data focusing on muscle enzymes, iron profile and Acute Phase Proteins. 30 Thoroughbred racing horses (15 geldings and 15 females) aged between 4-12 years (mean 7 years), were used for the study. All the animals performed a high speed-short term competition for a total distance of 154 m in about 12 seconds, repeated 8 times, within approximately one hour (Niballo Horse Race). Blood samples were obtained 24 hours before and within 30 minutes after the end of the races. On all samples were performed a complete blood count (CBC), biochemical and haemostatic profiles. The post-race concentrations for the single parameter were corrected using an estimation of the plasma volume contraction according to the individual Alb concentration. Data were analysed with descriptive statistics and the percentage of variation from the baseline values were recorded. Pre- and post-race results were compared with non-parametric statistics (Mann Whitney U test). A difference was considered significant at p<0.05. A significant plasma volume contraction after the race was detected (Hct, Alb; p<0.01). Other relevant findings were increased concentrations of muscular enzymes (CK, LDH; p<0.01), Crt (p<0.01), significant increased uric acid (p<0.01), a significant decrease of haptoglobin (p<0.01) associated to an increase of ferritin concentrations (p<0.01), significant decrease of fibrinogen (p<0.05) accompanied by a non-significant increase of D-Dimers concentrations (p=0.08). This competition produced relevant abnormalities on clinical pathology in galloping horses. This study confirms a significant muscular damage, oxidative stress, intravascular haemolysis and subclinical hemostatic alterations. Further studies are needed to better understand the pathogenesis, the medical relevance and the impact on performance of these alterations in equine sport medicine.

Osteochondrosis (OC) is a skeletal disorder that occurs in young, growing animals. It is defined as a focal disturbance of endochondral ossification, visible as small, discrete areas of abnormal bone and/or cartilage tissue occurring at typical sites on the articular surfaces of joints. In the Australian and New Zealand Thoroughbred horse populations, OC is one of the most common skeletal lesions reported to occur in young horses. The presence of OC lesions can negatively affect a horse's welfare, monetary value, and athletic performance. Approximately 1,300 diagnostic reports written to assist stud managers in their sales process were used as a data source to determine the prevalence of OC and other skeletal lesions in a population of Australasian Thoroughbred weanlings and yearlings. The prevalence and distribution of skeletal lesions and injuries described in these reports were consistent with those found in studies of related populations. Overall, 20.5% of yearlings were reported as having OC, and the most common sites for OC lesions were the lateral trochlear ridge of the distal femur, the medial femoral condyle, and the sagittal ridge of the third metacarpal bone. Based on these data, analyses were carried out to determine the extent to which non-genetic factors contribute to the prevalence of OC and other skeletal lesions in Australasian Thoroughbred yearlings; to estimate the heritability of OC and other skeletal lesions overall and at particular anatomical sites; and to estimate phenotypic and genetic correlations between pairs of skeletal lesion traits within and between joints. Correlations between Estimated Breeding Values (EBVs, the estimated sum of additive gene effects for each horse) were used as a proxy for conventional genetic correlation, which can not be determined on the underlying scale with currently available software for binary traits such as those in the current study. Non-genetic factors were found to contribute to the occurrence of some skeletal lesion traits in this population, but the effect of these factors was not consistent between traits. Breeding values were found to contribute significantly to the occurrence of OC, some OC component traits, and bone chip(s) or fragment(s) (FRAG) occurring proximal palmar/plantar to the first phalanx (PPP1) in the hind fetlocks. Heritability estimates for these traits ranged from 0.10 to 0.22. Not all OC traits had positive phenotypic or EBV correlations with one another. However, positive EBV correlations were found within a group of traits including stifle OC lesions and FRAG occurring PPP1 in the hind fetlocks. This group included multiple traits that were among the most prevalent in this population, that are known to have negative impacts on the financial value and/or race performance of affected horses. It appears to be a good potential target for genetic selection. Single Nucleotide Polymorphism (SNP)-based case-control genome-wide association studies (GWAS) were carried out for 11 OC traits, FRAG occurring PPP1 in the hind fetlocks, and for the chestnut coat colour as a positive control using the Illumina Equine SNP50 beadchip, in a group of 140 horses with skeletal lesion data from the current study. A check for population stratification identified one large cluster comprising the majority of the population and two small outlier clusters, each comprising the offspring of a single Australian-born Thoroughbred stallion. Despite only a small number of cases being available for these analyses, genome-wide significant quantitative trait loci were found on chromosome 30 for lysis at the sagittal ridge of the third metacarpal bones in the fore fetlocks (within the large cluster only), and on chromosome 3 for the positive control chestnut coat colour (within all three clusters of this population, and within the large cluster only). A pedigree analysis of the Australian Thoroughbred population was carried out using pedigree data provided by the Australian Stud Book. The impact of past changes in breeding practice, including changes in sire usage and the origins of imported breeding stock, was examined via trends in the rate of inbreeding and loss of genetic variability due to unequal use of founders, population bottlenecks and genetic drift over time. There has been a low rate of loss of genetic variability in the Australian Thoroughbred population since 1973. This rate of loss is now increasing and is likely to increase further in coming decades. The importation of breeding stock from traditional sources (New Zealand, Europe and North America) is no longer increasing genetic variability. The number of sires is decreasing and their co-ancestry is increasing. Selective breeding could be used to reduce the occurrence of many OC traits and FRAG occurring PPP1 in the hind fetlocks. The group of genetically associated traits that includes stifle OC and FRAG occurring PPP1 in the hind fetlocks appears to be a particularly good target for genetic selection, where minimisation of these lesions would result in financial benefit to breeders as well as improving the welfare of the horses. In recent decades, selective breeding techniques in first world agricultural animal species have generally implemented selection based on EBVs. More recently, techniques have been developed to include SNP data in the calculation of EBVs, resulting in Genomic Estimated Breeding Values (GEBVs) that have the potential to be substantially more accurate than EBVs. The data required in order to implement genetic selection in this population is easily available, but the creation and maintenance of such a program would require ongoing financial investment. This investment could come from either the industry as a whole, or individual breeders who are open to embracing genetic and/or genomic technologies that are new to the Thoroughbred horse industry. There is also the potential to extend any genetic selection program to include selection for particular athletic traits, or selection against other disorders with a genetic component.

This study investigated effects of diet and probiotic supplement on stress in Thoroughbred foals at weaning. Twenty foals, whose dams were paired by age and breeding date, then randomly assigned to one of two diets prior to parturition, were used. Two groups were maintained on mixed grass pastures and fed supplements, one high in sugar and starch (SS) and one high in fat and fiber (FF) that met or exceeded NRC requirements. Half the foals on each diet were fed a commercial probiotic (Probios) containing lactic acid bacteria, while the rest were given a placebo. Plasma, fecal samples and behavioral ethograms were collected for four days pre- and post-weaning, and an ACTH response test was administered 48 h post-weaning. Cortisol, lactate, IgG, IgA and a-tocopherol were analyzed in plasma, volatile fatty acids and pH in feces. Foals fed FF had higher concentrations of IgA (P = 0.006), IgG (P = 0.012) and a-tocopherol (P = 0.005). Butyric and valeric acid concentrations were higher in feces of SS but not FF foals (P = 0.052), which may reflect better adaptation to forage in FF foals. Foals supplemented with probiotic had higher fecal lactate (P = 0.002) and lower fecal acetate (P = 0.0003) concentrations, suggesting that the lactic acid bacteria survived to the hindgut. Probiotic supplementation did not appear to benefit foals at weaning. Supplementation with FF may improve immune status and encourage a more diverse intestinal microbial population, enabling foals to better cope with the physiological stresses of weaning.
Master of Science

Kyoto University (京都大学)
0048
新制・論文博士
博士(農学)
乙第12753号
論農博第2782号
新制||農||1015(附属図書館)
学位論文||H25||N4780(農学部図書室)
30566
昭和大学大学院薬学研究科医療薬学専攻
(主査)教授 祝前 博明, 教授 今井 裕, 教授 廣岡 博之
学位規則第4条第2項該当

Currently accepted optimum protein levels for growth in the horse may be reduced with amino acid supplementation. This study investigated the effects on growth and protein status of Thoroughbred foals offered a supplement with a typical CP level to a supplement that had a lower CP level fortified with limiting amino acids. The control supplement (CS) contained 14% CP, 3.0 Mcal/kg DM, 10% corn oil, 22% soybean meal, 1.4% calcium, and three sources of fiber. The experimental supplement (LTS) contained 9% CP, 3.0 Mcal/kg DM, 10% corn oil, 3% soybean meal, 1.4% calcium, three sources of fiber, and was fortified with .6% lysine and .4% threonine. Lysine and threonine are the first two limiting amino acids in common diets of the horse. Mares and foals were fed twice daily (0700 and 1400) and kept on 30-acre pastures (mixed grass/white clover) until weaning (7 months). Weanlings continued on specified supplements and pastures for seven additional months. Physical measurements and blood samples were taken monthly. Measurements included weight, average daily gain (ADG), body condition (BC), wither height, hip height, length, girth, forearm length, front and hind cannon length, physis and fetlock circumference. Blood analysis included total protein (TP), albumin (ALB), creatinine (CREA), and plasma urea nitrogen (PUN). Effect of diet and time were evaluated by analysis of variance with repeated measures. No differences were found in physical measurements between the CS and LTS groups (ADG 0.8(0.4 kg/day, BC 4.9(0.05) for the observational period. Blood data also showed no difference for the period (ALB 2.9 ( 0.03 g/dl, TP 5.7 ( 0.10 g/dl, CREA 1.1 ( 0.02 mg/dl). These results suggest that the foals offered the LTS faired as well or better than foals on the CS. Lower levels of crude protein (CP) in the diet will result in less nitrogen pollution of pasture lands due to better utilization in the horse. By fortifying a low protein diet with the first two limiting amino acids, the protein is used more efficiently for growth and development, thereby benefiting both the horse and the land.
Master of Science

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第18317号
農博第2042号
新制||農||1021(附属図書館)
学位論文||H26||N4824(農学部図書室)
31175
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 平井 伸博, 教授 今井 裕, 准教授 三宅 武
学位規則第4条第1項該当

Aims: To determine improvements in third metacarpal (Mc3) condylar microanatomy attributable to preconditioning exercise. To investigate developmental causes of Mc3 condylar fracture. Methods: Twelve Thoroughbred horses were raised at pasture; six received preconditioning exercise from 10 days. Calcein labels were administered 19 and 11 days prior to euthanasia at 18 months. Six horses also received 2 seasons of race-training and were euthanised at 3 years. Slices were taken from the distal Mc3 condyle in the frontal and dorsal- and palmar-oblique frontal planes, scanned with DXA and macerated (frontal slices) or embedded in PMMA (oblique slices). Articular calcified cartilage (ACC) and subchondral bone (SCB) in oblique slices were imaged using confocal scanning light microscopy and quantitative backscattered electron scanning electron microscopy. ACC and SCB in the palmar slice lateral parasagittal grooves were imaged using μCT and nanoindentation tested. Results: Characteristic spatial variations in ACC and SCB histomorphometric parameters were present, none of which was significantly related to preconditioning exercise. Thickened, aberrantly mineralised ACC was found in 13/24 parasagittal grooves in the palmar slices and on the sagittal ridge of 4/12 dorsal slices of 18-month-old horses. Deep to thickened ACC, SCB had an open marrow structure, having not adopted the buttress morphology of the normal SCB plate. SCB in 3-year-old horses had incorporated early ACC defects as notches in parasagittal grooves and a hyaline cartilage island in a sagittal ridge. ACC was less stiff and SCB more stiff in affected than unaffected parasagittal grooves. Chondroclastic resorption in the parasagittal groove may be retarded as early as 3-6 months, possibly due to localised inhibition of ACC mineralisation. Linear defects in the Mc3 parasagittal groove may develop prior to entry to race training and are not significantly affected by preconditioning exercise. Early identification of affected individuals should aid in reducing condylar fracture risk.

With a rise in concern for animal welfare, the equine world has started using positive reinforcement (R+); as such, horses often experience a combination of negative reinforcement (R-) and R+. I compared the effects of R- to a combination of positive and negative reinforcement (R-/R+) training. Horses were trained to walk across two visually discriminable liverpools (striped, Experiment 1; colored water, Experiment 2), each associated with either R- or R-/R+, and training type alternating across six days. I measured highest training criteria reached, prevalence of undesirable behaviors, salivary cortisol (pre- and post-training), time spent by the trainer in motionless human tests (pre- and post-training), and horses' preference for the two liverpools using concurrent choice. Across both experiments, I found no significant difference in the proportions of criteria reached between training types; horses engaged in mugging for longer periods of time in R-/R+ than R-; no significant difference between training types for the pre- to post-change of cortisol; a greater proportion of horses increased time spent with R-/R+ trainer than the R- trainer; and no difference between first choice in the preference test or time horses spent in proximity to the liverpool, based on the training type with which the liverpool was associated. Overall, I found few differences between R-/R+ and R-, which could be due to horses only having 30 min total training contact with either training, or my use of relatively low intensities of R- and R+.
Master of Science
The equine world has started using positive reinforcement (R+), such as providing treats. Often horses experience a combination of negative reinforcement (R-) and R+, such as having rein pressure released and being given a treat. I compared effects of R- to a combination of positive and negative reinforcement (R-/R+) training. Horses were trained to walk across two visually distinct liverpools, a 1 m X 2.7 m shallow pool, (striped, Experiment 1; colored water, Experiment 2) each associated with either R- or R-/R+, and training type alternating across six days. I measured highest training level reached, occurrence of undesirable behaviors, salivary cortisol (a measure of stress), time spent by the trainer in motionless human tests, and horses' preference for the two liverpools. Across both experiments, I found no significant difference in the proportions of criteria reached between training types; horses investigated the trainer for treats for longer durations in R-/R+ than R-; no significant difference between training types for the pre- to post-change; a greater proportion of horses increased time spent with R-/R+ trainer than R- trainer; and no difference between first choice in the preference test or time horses spent in proximity to the liverpool, based on the training type with which the liverpool was associated. Overall, I found few differences between R-/R+ and R-, which could be due to horses only having 30 min total training contact with either training, or my use of relatively low intensities of R- and R+.

The purpose of the studies presented in this thesis was to develop a greater understanding of the contribution of respiratory heat loss to the thermal balance of exercising horses. In the first experiment the effect of three different warm-up regimens on the thermal balance of Thoroughbred horses was investigated. The experiments showed that a low intensity warm-up was most beneficial aiding heat dissipation during subsequent exercise. The study also showed the heat loss by sweating is not restricted by the rate of sweat production, but by the evaporation rate of the sweat. In the second experiment, horses were exercised to fatigue in thermoneutral and hot-humid environments. The evaporative heat dissipation from sweating and from the respiratory tract was severely impaired during the hot humid exercise protocol. There was a significant increase in the heart rate and the metabolic rate during the hot humid protocol, thus indicating the additional work done by the horse in an effort to dissipate the rapidly accumulating heat. The significantly shorter time to fatigue may be a mechanism to protect the horse from circulatory collapse as the circulatory demands for cardiac output exceed its capacity. In the third experiment adaptations that the horse is able to make to alleviate the compromised evaporative heat loss were identified. These experiments showed that the horse is able to shorten its stride, increase minute ventilation and the velocity of the air in the conducting airways. The results presented also indicate that the horse is able to modify the evaporative area of the airways to enhance evaporative heat loss from the respiratory tract. The experiments also showed that during exercise in hot-humid environments, small changes in the evaporating surface vapour pressure have a significant effect on the vapour pressure gradient thus having a significant effect on the evaporating heat loss. Finally, the lessons gained during the experiments presented in this thesis were used to revise and refine a mathematical model of the thermal balance of exercising horses. The resulting model is more accurate and easier to apply to use in the field.
Thesis (DPhil)--University of Pretoria, 2000.
Equine Research Centre
unrestricted

Commingling of horses from various populations, together with physiological stress associated with transport and confinement at a sales complex, may be associated with detection and transmission of equine herpesvirus type-1 (EHV-1) and -4 (EHV-4). This prospective cohort study aimed to investigate the currently undefined prevalence of EHV-1 and -4 in young Thoroughbreds at an auction sale in South Africa, and associations between clinical signs, physiological stress and viral detection. Ninety, two-year old Thoroughbreds (51 colts, 39 fillies) were consigned from eight farms and sampled at a South African auction sale. The horses were monitored for pyrexia and nasal discharge. Nasal swabs were collected for quantitative polymerase chain reaction (qPCR) assay to detect EHV-1 and -4 and faecal samples were collected for enzyme immunoassay (EIA) to determine faecal glucocorticoid metabolite (FGM) concentrations. EHV-4 nucleic acid was detected in some and EHV-1 nucleic acid in none of the population. Pyrexia and nasal discharge were poor indicators of EHV-4 status. Variation in FGM concentrations was best explained by transportation and preparation for auction. Peaks in EHV-4 detection and increases in FGM concentrations were identified shortly post-arrival and on the first day of auction. Temporal changes in FGM concentrations of horses from individual farms showed two distinct patterns: Pattern A (biphasic peaks) and Pattern B (single peak). It was concluded that sales consignment was associated with some EHV-4 nucleic acid detection and distinctive physiological stress patterns in this population of young Thoroughbreds.
Dissertation (MSc)--University of Pretoria, 2014.
tm2015
Companion Animal Clinical Studies
MSc
Unrestricted

Lawsonia intracellularis and the disease it causes in horses, equine proliferative enteropathy (EPE), is an emerging pathogen of increasing importance to the horse industry from both an economic and welfare standpoint. Long recognized as an economically important disease of swine, the hallmark of EPE is a protein-losing enteropathy, where affected horses suffer weight loss and some ultimately succumb to the disease despite aggressive treatment. There are currently no known EPE preventative measures and the epidemiology of the disease remains poorly defined. While EPE is a sporadic disease affecting less than 25% of exposed horses, some farms experience clinical cases year after year. Further, weanlings are uniquely susceptible to this disease, although no conclusive reason for this predisposition has been identified. The overall hypothesis is that the host immune response plays a significant role in the susceptibility of weanlings to L. intracellularis infection and the occurrence of clinical equine proliferative enteropathy. To test this hypothesis, four individual hypotheses were proposed: (H1) previous farm history of EPE does not have an effect on weanling seroprevalence, (H2) passively-acquired antibodies do not have an effect on susceptibility to L. intracellularis and the occurrence of EPE, (H3) the serological status of mares can be used to determine the role they play in the epidemiology of EPE on endemic farms, and (H4) L. intracellularis-specific IFN-g expression is not associated with increased resistance to EPE.