Academic literature on the topic 'Thoroughbread horse'

Objective: The study aimed to evaluate the diversity of donkey populations by comparing with the diversity of Thoroughbred and Jeju Halla horses; identified breeding backgrounds can contribute to management and conservation of donkeys in South Korea.Methods: A total of 100 horse (50 Thoroughbreds and 50 Jeju Halla horses) and 79 donkeys samples were genotyped with 15 microsatellite markers (AHT4, AHT5, ASB2, ASB17, ASB23, CA425, HMS1, HMS2, HMS3, HMS6, HMS7, HTG4, HTG10, LEX3, and VHL20), to identify genetic diversity and relationships among horses and donkeys.Results: The observed number of alleles per locus ranged from 1 (ASB17, HMS1) to 14 (AHT5), with a mean value of 4.87, 8.00, and 5.87 in Thoroughbreds, Jeju Halla horses, and donkeys, respectively. Of the 15 markers, AHT4, AHT5, ASB23, CA425, HMS2, HMS3, HTG4, HTG10, and LEX3 loci had relatively high polymorphism information content (PIC) values (PIC>0.5) in these three populations. Mean levels of genetic variation were HE = 0.6721 and HO = 0.6600 in Thoroughbreds, HE = 0.7898 and HO = 0.7100 in Jeju Halla horses, and HE = 0.5635 and HO = 0.4861 in donkeys. Of the 15 loci in donkeys, three loci had negative inbreeding coefficients (FIS), with a moderate mean FIS (0.138). The FIS estimate for the HTG4 marker was highest (0.531) and HMS6 marker was lowest (–0.001). The total probability of exclusion value of 15 microsatellite loci was 0.9996 in donkeys.Conclusion: Genetic cluster analysis showed that the genetic relationship among 79 donkeys was generally consistent with pedigree records. Among the three breeds, donkeys and Thoroughbred horses formed clearly different groups, but the group of Jeju Halla horses overlapped with that of Thoroughbred horses, suggesting that the loci would be suitable for donkey parentage testing. Therefore, the results of this study are a valid tool for genetic study and conservation of donkeys.

In the first four decades of the twentieth century, horse racing was one of America’s most popular spectator sports. Members of America’s elite took to breeding and racing horses as one of their preferred pastimes. Coinciding with an increase in immigration and the rediscovery of Mendelian genetics, the idea that careful breeding of thoroughbreds would result in improved horses resonated with Americans worried about racial degeneration. Scientists committed to racial ideologies looked to thoroughbreds—whose owners and breeders maintained extensive pedigree records—to understand the science of genetic inheritance. Harry H. Laughlin, superintendent of research at the Eugenics Record Office at Cold Spring Harbor, Long Island, pored over breeding charts and race results to develop a mathematical model of inheritance that he called the “inheritance coefficient.” He believed his careful study of horses would yield findings that he and his fellow eugenicists could apply to humans. Thoroughbred breeders followed trends in genetics while contributing to the production of scientific knowledge. Pedigree charts available to bettors at race tracks helped normalize concepts of biological inheritance for race track attendees of all classes. Horse racing’s popularity in the United States contributed to the diffusion of the concept of biological race that originated as an ideological project of the ruling class. This paper analyzes the role of thoroughbred breeding and racing in the formation and popularization of racial ideology by situating breeding farms as sites of knowledge production and racecourses as places that exhibited performances of racial science for large audiences.

During the past eight years a comprehensive genetic linkage map for the horse has been generated in Newmarket, through a fruitful collaboration between the Genetics section at the AHT and Professor Twink Allen at the TBA Equine Fertility Unit (Swinburne et al., 2000). In order to assess whether the map was adequate to start mapping disease traits in which we are interested, it was decided to attempt to map a clear, easily scoreable trait such as grey coat colour in the Thoroughbred horse. Grey coat colour is inherited as an autosomal dominant trait. Thoroughbred horses are fairly inbred, and as such they represent one of the more difficult horse breeds for genetic mapping. The majority of grey Thoroughbreds trace their ancestry back to Allcock's Arabian who was born in 1700, and horsemen have long noted an association between grey coat colour and the incidence of melanomas. It is hoped that characterizing the mechanism of grey coat colour formation might also lead to an improved understanding of the molecular basis of melanoma formation.

The effectiveness of commonly used parasiticides decreases due to the drug resistance developed by many organisms. Therefore, the application of feed additives possessing antiparasitic properties may be helpful in limiting the burden of parasites. The aim of this research was to evaluate parasitological coefficients for endoparasites of regularly dewormed Arabian horses and Thoroughbreds, fed on a basal diet of oat and muesli with vegetable oils and/or without vitamin E. The observations revealed parasitic invasion in 25 of 27 examined horses. The most frequent in both breeds were Strongylidae—accounting for 86% of Thoroughbreds and 100% of Arabian horses. Strongyloididae were observed in 33% of individuals representing both breeds while botflies were found in one Arabian horse and one Thoroughbred. Mean EPG coefficients for strongylids and strongyloidids were higher in Thoroughbreds (530 vs. 529 and 43 vs. 29, respectively), although the differences were not statistically significant. The addition of pure linseed oil significantly reduced the number of Strongylidae in fecal samples. The results indicate that properly selected plant additives obtained from arable crops may be helpful in limiting the numbers of drug-resistant strongylids.

Research into the growth and development of Thoroughbreds managed on commercial breeding farms is reviewed in this paper. As horses are not meat producing animals, less research has been performed quantifying growth, muscle and bone development than with other production animals. However, variations in growth and development are linked with both value and wastage in young Thoroughbred horses, and can have a long-term impact on racing performance. In Thoroughbred horses, the breeder aims for optimum, or consistent, growth rather than maximum growth. Factors affecting equine growth including environment, nutrition, season and management are discussed in sections covering conception to weaning, weanling to yearling and yearling to 2 years old when horses are nearly fully grown and racing begins. The importance of reference curves for different ages, sex and locations is highlighted. While average daily gain (ADG) declines as the foal gets older, there are seasonal and management influences to consider. Month of birth has an influence on both birthweight and the expected ADG at different ages, which are believed to be related to ambient temperatures and pasture availability for the mare and growing horse. Weaning leads to a growth setback and ADG declines through winter, but increases in spring for the yearling as temperatures and pasture quality and quantity increase. Management factors such as yearling sale preparation are associated with an increase in growth rate, with gains of over 1 kg/day common during the yearling sales preparation process of 6–12 weeks. ‘Home-bred’ horses that do not go to a yearling sale grow at a slower rate but will reach the same endpoint in mature size. Growth of Thoroughbreds is influenced by country, and regions within a country, related to genetics, climate, management practices, market preferences and sale timing. More research is needed into factors affecting growth and development of Thoroughbred horses on commercial farms and the influence differing rates of growth and development have on wastage (such as developmental orthopaedic disease) and commercial outcomes such as yearling sale results and, ultimately, racing performance.

An equine parvovirus-hepatitis (EqPV-H) has been recently identified in association with equine serum hepatitis, also known as Theiler’s disease. The disease was first described by Arnold Theiler in 1918 and is often observed with parenteral use of blood products in equines. However, natural ways of viral circulation and potential risk factors for transmission still remain unknown. In this study, we investigated the occurrence of EqPV-H infections in Thoroughbred horses in northern and western Germany and aimed to identify potential risk factors associated with viral infections. A total of 392 Thoroughbreds broodmares and stallions were evaluated cross-sectionally for the presence of anti-EqPV-H antibodies and EqPV-H DNA using a luciferase immunoprecipitation assay (LIPS) and a quantitative PCR, respectively. In addition, data regarding age, stud farm, breeding history, and international transportation history of each horse were collected and analysed. An occurrence of 7% EqPV-H DNA positive and 35% seropositive horses was observed in this study cohort. The systematic analysis of risk factors revealed that age, especially in the group of 11–15-year-old horses, and breeding history were potential risk factors that can influence the rate of EqPV-H infections. Subsequent phylogenetic analysis showed a high similarity on nucleotide level within the sequenced Thoroughbred samples. In conclusion, this study demonstrates circulating EqPV-H infections in Thoroughbred horses from central Europe and revealed age and breeding history as risk factors for EqPV-H infections.

The Waler horse breed is an integral part of Australian history. The purposes of this study were to analyse the genetic variability in Waler horses from Australia and to investigate genetic relationships with other horse breeds. We examined the genetic diversity of 70 Waler horses sampled from seven breeding stations in Australia. Also we analysed the relationships of these horses with 11 other horse breeds. Analysis of the genetic structure was carried out using 15 microsatellite loci, genetic distances, AMOVA, factorial correspondence analysis and a Bayesian method. We found that the genetic diversity in the Waler was greater than the domestic horse mean and exceeded that of all endangered horse breeds. Our findings also revealed moderate population subdivision rather than inbreeding. All genetic similarity measures indicated that the Thoroughbred might be a key ancestor to the Waler. This study indicates that there is no immediate concern for loss of variation in Waler horses. Also, there clearly has been a strong input from the Thoroughbred into the Waler horse breed. However, the genetic evidence suggests that this input was not just direct but also came through other types of horses with a Thoroughbred cross background.

The purpose of this study was to find out whether abilities to win races of different distances are different traits. Data included information on 14 665 starts of 1 646 Thoroughbreds, aged 2 to 9 years and on 10 862 starts of 1 145 Arab horses, aged 3 to 10 years. The data comprised seven racing distances for Thoroughbred horses, i.e. 1 000, 1 200, 1 300, 1 400, 1 600, 1 800, >1 800 m, and five for Arab horses, i.e. 1 400, 1 600, 1 800, 2 000 + 2 200, >2 200 m. Placings at the finish (square root) of different racing distances were treated as different traits and analysed by a two-trait animal model. The highest heritability (0.16) was obtained for the shortest distance in Thoroughbreds. Heritability for longer distances was much lower (0.04–0.09). The heritability estimates for Arab horses are very low for all distances (0.02–0.08). Genetic correlations between racing distances ranged from 0.54 to 0.98 in Thoroughbreds and from 0.95 to 0.99 in Arab horses. Genetic correlations in Thoroughbreds decreased as the differences of each racing distance increased whereas they remained high and constant in Arab horses. It means that we discuss very much the same trait measured only at different race distances for Arab horses but a little bit different in the case of Thoroughbreds.  

Abstract Thoroughbred horse sales prices rely heavily on animal conformation and ancestral race performance, as well as the current economic landscape. However, little information exists on the relationship between physiological parameters and sales price. We aimed to test the hypothesis that weanling sales price would positively correlate with skeletal muscle mitochondrial parameters in racing-bred Thoroughbreds. Gluteus medius muscle samples were collected from racing-bred Thoroughbred weanlings (n = 19; mean ± SD; 5.7 ± 0.3 mo) and evaluated for mitochondrial volume density (citrate synthase activity; CS) and function (cytochrome c oxidase activity; COX) by colorimetry, and oxidative and electron transport system capacities by high resolution respirometry. Horses were sold at the 2018 and 2019 Keeneland November Breeding Stock Sales at 8.5 ± 0.7 mo of age. Data were analyzed using Pearson Correlation Statistics in SAS (v9.4). Weanling sales price was positively correlated with intrinsic mitochondrial function (COX activity per unit CS; r = 0.6269, P = 0.004) and coupling efficiency with substrates for complex I+II (r = 0.4424, P = 0.05). A trend for a negative correlation was observed between weanling sales price and CS activity (r = -0.4179, P = 0.07), while a trend for a positive correlation between sales price and intrinsic oxidative phosphorylation capacity with complex I substrates (r = 0.3974, P = 0.09) was observed. In this cohort of weanling Thoroughbreds, mitochondrial parameters measured at 6 mo of age correlated with sales price at 8 mo of age. Implications of these relationships as they relate to race performance should be further investigated.

In thoroughbred horses, red blood cell amino acid transport activity is Na+-independent and controlled by three codominant genetic alleles (h, l, s), coding for high-affinity system asc1 (L-alanine apparent Km for influx at 37 °C [Formula: see text] 0.35 mM), low-affinity system asc2 (L-alanine Km[Formula: see text] 14 mM), and transport deficiency, respectively. The present study investigated amino acid transport mechanisms in red cells from four wild species: Przewalski's horse (Equus przewalskii), Hartmann's zebra (Zebra hartmannae), Grevy's zebra (Zebra grevyi), and onager (Equus hemonius). Red blood cell samples from different Przewalski's horses exhibited uniformly high rates of L-alanine uptake, mediated by a high-affinity asc1-type transport system. Mean apparent Km and Vmax values (± SE) for L-alanine influx at 37 °C in red cells from 10 individual animals were 0.373 ± 0.068 mM and 2.27 ± 0.11 mmol (L cells∙h), respectively. As in thoroughbreds, the Przewalski's horse transporter interacted with dibasic as well as neutral amino acids. However, the Przewalski asc1 isoform transported L-lysine with a substantially (6.4-fold) higher apparent affinity than its thoroughbred counterpart (Km for influx 1.4 mM at 37 °C) and was also less prone to trans-stimulation effects. The novel high apparent affinity of the Przewalski's horse transporter for L-lysine provides additional key evidence of functional and possible structural similarities between asc and the classical Na+-dependent system ASC and between these systems and the Na+-independent dibasic amino acid transport system y+. Unlike Przewalski's horse, zebra red cells were polymorphic with respect to L-alanine transport activity, showing high-affinity or low-affinity saturable mechanisms of L-alanine uptake. Onager red cells transported this amino acid with intermediate affinity (apparent Km for influx 3.0 mM at 37 °C). Radiation inactivation analysis was used to estimate the target size of system asc in red cells from Przewalski's horse. The transporter's in situ apparent molecular weight was 158 000 ± 2500 (SE).Key words: amino acid transport, erythrocyte, Przewalski's 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.

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

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

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 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.

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

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

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