African horsesickness is caused by the AHSV, a member of the genus Orbivirus, family Reoviridae. Nine serotypes have been identified. The viral genome consists of ten double stranded (ds) RNA segments encoding at least 7 structural and 4 non¬structural proteins. The major core proteins VP3 and VP7 together with the minor core proteins VP1, VP4 and VP6 form the core particle surrounding the 10 dsRNA segments. An outer capsid, consisting of two major structural proteins VP2 and VP5 surrounds the core. VP2 is the most variable of the proteins within the AHSV serogroup and carries serotype specific epitopes which induce a protective immune response against virulent homologous AHSV challenge. The VP2 protein is therefore the antigen of choice for the development of a subunit vaccine against AHSV. It has been shown that protection against AHSV-4 can be achieved by vaccination with AHSV VP2 protein. The AHSV-3 VP2 protein has previously been cloned and expressed as baculovirus recombinant protein in our laboratory. The recombinant protein induced only a weak neutralising immune response. It has been determined in this investigation that the majority of recombinant AHSV-3 VP2 proteins expressed in Sf-9 insect cells are in an insoluble, aggregated form. This is likely to be the cause of the poor neutralising immune response induced by this protein. In order to investigate this problem two strategies were adopted. First an attempt was made to chemically solubilise the particulate VP2 protein and refold the protein into a form that may present the neutralising epitopes more appropriately. The solubilisation of the protein with 6M Guanidinium HCI was successful, but the largest percentage of the protein was again rendered insoluble during the refolding process which involves the removal of Guanidinium HCI by column chromatography. The chemical solubilisation therefore proved to be too inefficient to provide a solution to the problem. The second method for increasing the solubility and immunogenicity of the VP2 protein was by co-expression of VP2 and VP5, the two outer capsid proteins of AHSV¬3. For the dual expression of the two proteins it was necessary to characterise the AHSV-3 VP5 gene and express it as a baculovirus recombinant first. The VP5 gene was therefore sequenced. A nucleotide sequence of 1566 bp was determined encoding a peptide of 505 amino acids with a predicted size of 56K. The VP5 was expressed as baculovirus recombinant using the baculovirus Bac-to-Bac™ expression system. The yield of VP5 was low but was nevertheless better than the expression levels of AHSV-9 VP5 gene using an alternative baculovirus expression system. AHSV-3 VP2 and VP5, were cloned respectively under the polyhedrin and p10 promoters of the pFastbac dual transfer vector of the Bac-to-Bac™ baculovirus expression system. mRNA transcription of both AHSV-3 VP2 and VP5 genes in Sf-9 cells was shown. The expression of VP2 was also demonstrated but VP5 was very poorly expressed by the dual recombinant. Further research to determine the effect co-expression of AHSV-3 VP5 in the AHSV-3 VP2 antigenicity is needed. / Dissertation (MSc Agric (Genetics))--University of Pretoria, 2006. / Genetics / unrestricted

Purpose: Trigger points may occur when muscle is subject to direct trauma, sustained tension, fatigue, radiculopathy, joint dysfunction and emotional stress, which may cause aberrant nerve conduction and dysfunction of the motor neurons. Any of these factors may increase the possibility of overload stress to a muscle and may convert a latent trigger point to an active one. In humans, due to muscle attachments, spinal manipulation causes reflex relaxation of associated and distal musculature. The purpose of this study was to assess the effects of upper cervical spine manipulation, specifically C1, on pain tolerance of trigger points over the erector spinae muscles in show-jumping horses. Method: This study consisted of two groups, the experimental and the control group, each consisting of ten horses. Potential candidates were examined and accepted based on the inclusion and exclusion criteria. The only method of treatment that was administered to each horse was chiropractic manipulation to the most restricted side of the UPPER CERVICAL SPINE joint complex, from which the objective findings were based. Procedure: Both groups were examined for trigger points within the Erector Spinae muscles and these trigger points were assessed, via an algometer, for spot tenderness. All horses were then examined for a cervical restriction of the upper cervical spine. Only the experiment group had the restriction corrected by a chiropractic manipulation and thereafter both groups were reassessed two minutes later, and then again two weeks later, via an algometer, for spot tenderness within the same trigger points. Results: Statistically significant changes were found when comparing the algometer readings before the adjustment with the algometer readings after the adjustment on the right. Otherwise no statistically significant differences were found when comparing algometer readings before the adjustment with the algometer readings after the adjustment on the left, or when comparing the algometer readings before the adjustment with the algometer reading two weeks later bilaterally. Conclusion: The results were inconclusive with regards to immediate and prolonged effects of upper cervical spine manipulation, specifically C1, on pain tolerances over the erector spinae muscle. As this study was directed to a small group of subjects, accurate conclusions cannot be formulated due to the insignificant findings obtained from the study and further research needs to be performed on the effects of upper cervical spine manipulation on trigger points in horses. / Dr. Ashleigh Deall Dr. Alex Niven Dr. Chris Yelverton

The aim of this study was to investigate the effect of reverse shoes, partial dorsal hoof wall removal and polystyrene solar support on the biomechanics of the front hoof of the horse. Laminitis is a systemic syndrome that ultimately affects the sensitive lamellae and papilla of the hoof, causing severe pain, and often leading to disruption of the lamellae-hoof wall interface. Degeneration of the lamellar interdigitation occurs and the distal phalanx (P3) separates from the hoof wall. This can cause P3 to rotate towards the sole and, in more severe cases, P3 separates totally from the hoof wall and sinks downwards. Chronic laminitis usually results in the end of the animal’s athletic career and may lead to humane destruction During an in vitro study, three clinically healthy horses were euthanased and their dismembered forelimbs were used. A reverse shoe was applied and three polystyrene pads with a density of 32 kg/m3, thickness of 60mm and wedges of 66%, 50% and no wedging, respectively, were used in this study. Fuji Prescale Super and Ultra Super Low-Pressure film was used to indicate the pressure distribution of the polystyrene on the solar surface of the hoof. Two load cells were used to measure the load borne by the hoof wall and the solar area, respectively. A constantly increasing force with a maximum of 66% of the bodyweight of the horse was applied to the amputated limb by means of a tensile testing machine. A total of four experiments were done on each limb. The results of this investigation showed that for all three of the polystyrene paddings, approximately 75 - 80% of the total load applied was borne by the solar area. The colour changes on the pressure film showed that most of the load of the 50% and 66% wedged polystyrene was borne by the palmar half of the solar surface, and less pressure by the dorsal half. For no wedging, the pressure distribution over the solar surface was even. The reverse shoe with the 66% and the 50% wedged polystyrene pads was shown to be useful in distributing the pressure to the palmar area of the sole. During an in vivo study, the effect of different densities (32 kg/m3, 24 kg/m3 and 16 kg/m3) and different thicknesses (100mm and 60mm) of polystyrene padding, with a wedge of 50%, on the load distribution of the solar surface and the hoof wall was investigated. Compression of polystyrene over time and the effect thereof on the load distribution was determined. The front hooves of three clinically healthy horses with a mean bodyweight of 551 kg, were trimmed and shod with reverse shoes. Reference data was recorded with only the reverse shoes on the hooves. Further data recording was done for the different polystyrene pads. Data was recorded for 4 seconds with a frequency of 50Hz. Between the treatments, the horses walked for 5 minutes on a concrete surface. This procedure was repeated 5, 10 and 15 minutes after application of the pads. All the results of the solar pads used in the in vivo study showed a hyperbolic tendency in which the initial load was high and then diminished with time. Initially, treatments 5 (32 kg/m3 x 60 mm) and 3 (16 kg/m3 x 60mm) proved to be the better treatments, but after 15 minutes no significant different was found between the treatments. From the observations made during the experimental procedure, the 32 kg/m3 x 60mm (treatment 5) compressed to a more dense and rigid end-product than the 16 kg/m3 x 60mm (treatment 3). The compressed pad of treatment 3 was more elastic and may have contributed positively to reducing the compression of the pads on the blood vessels underneath P3. Observations made during the experimental procedures indicated that polystyrene with a thickness of 100mm, is not recommended. This polystyrene was very uncomfortable for the horse immediately after application. Some polystyrene compressed outside the solar surface and was therefore not adequate for the object of the study. It was concluded that polystyrene pads with densities of 32kg/m3, 24kg/m3 and 16kg/m3 and thicknesses of 100mm and 60mm would prove similar support for the remainder of the period that they were applied follow a variable compression phase of less than 15 minutes. Further research need to be done to investigate the effect of the polystyrene pad on the solar surface for a longer period. Copyright / Dissertation (MSc)--University of Pretoria, 2009. / Companion Animal Clinical Studies / unrestricted

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 purpose of the current study is to evaluate a procedure that can be used to introduce horses to clipping. Negative reinforcement was used in a shaping paradigm. Shaping steps were conducted by the handler, starting with touching the horse with the hand, then touching the horse with the clippers while they are off, culminating with touching the horse with the clippers while they are on. When a horse broke contact with either the hand or the clippers, the hand or the clippers were held at that point until the horse emitted an appropriate response. When the horse emitted an appropriate response, the clippers were removed, and the handler stepped away from the horse. For all eight horses, this shaping plan was effective in enabling the clipping of each horse with minimal inappropriate behavior and without additional restraint. The entire process took under an hour for each horse.

This study was undertaken to evaluate fertilization and early embryo development of in vitro matured (IVM) horse oocytes following transfer with homologous sperm to the oviduct of estrous ewes. A total of 1023 follicles (5.1 per ovary) were found after processing 202 slaughterhouse ovaries by aspiration and subsequent slicing. Most follicles (79%) were less than 20-mm in diameter. Six hundred sixty-seven oocytes were recovered (3.3 per ovary; recovery rate, 65%). About two-thirds of oocytes were recovered by slicing, which yielded twice the number of oocytes as aspiration. Sixty four percent cumulus oocyte complexes (COCs) recovered by each method were grade A and the overall distribution of oocytes by grade was not affected by the method of recovery. Oocytes underwent IVM for an average of 41-h and were subjected to either in vitro fertilization (IVF) or xenogenous gamete intrafallopian transfer (XGIFT). At the onset of IVM, 83% COCs had compact cumulus investment. At the end of IVM, 78% COCs showed cumulus expansion. The expansion score was not improved with increasing the IVM duration from 32.3 to 50.3 h. Five (15%) IVF oocytes showed changes indicative of fertilization and two cleaved to 3 and 4-cell stages. Oviducts of 16 ewes were use for XGIFT, which involved surgical transfer of an average of 13 oocytes with 40x103 capacitated spermatozoa per oocyte. Of 259 oocytes transferred, 36 (14%) were recovered between 2 to 7 d post XGIFT and 13 (36%) showed cleavage ranging from the 2-cell to hatching blastocyst stage. The ovarian status of ewes and ligation of the uterotubal junction (UTJ) at the time of XGIFT, or the duration gametes were allowed to reside in the uterine tube, did not affect the recovery and cleavage rate. However, the most advanced stage embryos were recovered from ewes ovulating shortly after XGIFT. Fertilization following XGIFT was further demonstrated by the detection of ZFY loci in one embryo. This study demonstrated, for the first time, that horse embryos could be produced in a non-equine species. However, further studies focusing on the establishment of pregnancy in the mare using such embryos and improvement of the recovery and fertilization rates following XGIFT are recommended for use of XGIFT in horse assisted reproduction. / Master of Science

Resveratrol, a naturally-occurring phytoestrogenic stilbene derivative, has been shown to elicit shifts in physiology of obese animals consuming a high calorie or ad libitum diet toward that of lean counterparts. This study was designed to evaluate effects of oral resveratrol supplementation on parameters of metabolic health and reproductive cyclicity in obese mares on pasture. Seventeen healthy, mares were matched by age and assigned to obese control (OBC; n=5, mean BCS=7.4±0.3), obese supplemented with 5g/d resveratrol (OBR; n=6, mean BCS=7.4±0.2) or non-obese control (NOC; n=6, mean BCS=5.4±0.1) treatments. Control horses received the resveratrol carrier paste. Across three consecutive estrous cycles, morphometric measurements were collected biweekly and follicular dynamics were evaluated via transrectal ultrasonography every other day. Frequently-sampled intravenous glucose tolerance tests were conducted pre- and post- treatment. Insulin and glucose kinetics were analyzed via minimal model. Resveratrol supplementation had no discernible effect on reproductive parameters (P>0.05), however obese mares had more (6 vs. 0) hemorrhagic anovulatory follicles. Neither resveratrol treatment nor time on study influenced morphometric measurements or minimal model parameters (raw data or data adjusted for animal size). As a whole, horses became more insulin resistant over time (Si value < 0.78 (1/[mU/L"min]). NOC horses had lower (P=0.01) acute insulin response to glucose relative to OBC or OBR. Although resveratrol supplementation did not elicit detectable responses in this study, promising results in other species warrant further investigation of the compound in horses, including exploration of bioavailability and possible effects at the tissue or cellular levels. / Master of Science

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

In this study, the selection and breeding of Friesian horses in Southern Africa were evaluated. Literature was reviewed for sUbjective and objective selection criteria in horse breeding with special reference to the Friesian. 852 Pedigree records from Friesian horses registered at the FPSSA and SAFBA, were included for pedigree analyses and 232 horses were measured for eight different linear body measurements. Only 25,7% of the population was found to be inbred. A regression of average inbreeding on year of the whole population, indicated a relatively slow increase in the rate of inbreeding. It is, however, suspected that this could be a conservative estimation, because of the limited pedigree information. The results indicated that the Friesian horse is normally of rectangular (height at withers: body length) shape. A large average difference between wither height and back height was observed. The cannon length measurements were proportional to overall size, no obvious deviations were observed. Pearson correlation estimates between the eight body measurements were mostly in accordance with other studies on horses reported in the literature. A sire model was fitted for the estimation of heritability for wither-, back- and croup height, body length, cannon circumference and cannon length. Estimates ranged from 0.30 for wither height to 0.57 for cannon circumference. The results indicate that South African breeders can apply body measurements in their selection programs for Friesians. From the results, guidelines were provided for establishing a database for Friesian horses in Southern Africa to ensure a scientific approach to selection and breeding. / Dissertation (MSc (Agric))--University of Pretoria, 2003. / Animal and Wildlife Sciences / unrestricted

No description available.