A retrospective study was performed to determine the prevalence of foot pathologies of horses subjected to magnetic resonance imaging for foot lameness and to determine the long-term outcome of horses after medical treatment. The MR studies of 95 horses were interpreted retrospectively by a boarded certified radiologist. Follow-up information was obtained from medical records, owners and referring veterinarians via telephone questionnaires. Long term response to treatment (minimum of 12 months) was recorded. Horses were divided in two different groups based on the diagnosis and on the treatment using intrasynovial antiinflammatory drugs or not. Logistic regression analysis was performed to compare the outcome between the two groups. The null hypothesis was that the proportion of horses treated successfully between treatment protocols was similar. A diagnosis based on magnetic resonance imaging was made in all horses. Approximately 30% of horses had ≥ 4 lesions, which were determined to be responsible for the lameness and 70% of horses had navicular bone abnormalities. Treatment was determined by individual clinician judgment. No significant difference was found in the long-term outcome between treatment groups. This result suggests that intrasynovial antiinflammatory drugs may not provide additional benefit over corrective shoeing, rest followed by controlled exercise in horses with lesions of structures associated with the navicular apparatus or the distal interphalangeal joint. / Master of Science

The objective of this study was to determine if topical antimicrobials silver sulfadiazine and povidone-iodine ointment increase rates of healing of equine distal limb wounds that heal by second intention. Second, to determine the effect of bandaging with these topical antimicrobials. Six healthy adult horses were used to create thirty-six, 2.5 cm2 standardized full-thickness metacarpal/tarsal skin wounds. Each wound was exposed to a single treatment: 1.0 % silver sulfadiazine cream bandaged (SSD-B), 1.0 % silver sulfadiazine slow release matrix bandaged (SDX-B), 1.0% silver sulfadiazine slow release matrix not bandaged (SDX-NB), povidone-iodine ointment bandaged (PI-B), untreated control bandaged (C-B) and untreated control not bandaged (C-NB) until healing. Wound area, granulation tissue area and perimeter were measured with planimetry software from digital images obtained at each observation. Exuberant granulation tissue was excised when present. The days until healing, rate of healing parameter, rates of contraction and epithelialization were compared among groups using pair-wise analysis of least square means. The healing parameters and mean days to healing did not statistically differ between groups. Analysis of percent wound contraction and rate of epithelialization between groups was similar. Mean number of days to healing ranged from 83 (PI-B and C-B) to101 (SSD-B). All bandaged wounds produced exuberant granulation tissue requiring excision compared to none of the unbandaged. The identified rates of epithelialization and wound contraction found insignificant differences between antimicrobial treated versus untreated wounds. Similarly, rates of epithelialization and wound contraction found insignificant differences between bandaged versus unbandaged wounds. Topical povidone-iodine and silver sulfadiazine did not increase rates of healing under bandage. The 1.0% silver sulfadiazine slow release matrix not bandaged (SDX-NB) adhered well to dry wounds. Silver sulfadiazine slow-release matrix provides does not impede wound healing and provides good adherence to dry wounds not amenable to bandaging. / Master of Science

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+.

Tendon injuries are a significant cause of morbidity in performance horses with superficial digital flexor tendon injury reported to represent up to 43% of overall Thoroughbred racehorse injuries. Natural repair is slow and results in inferior structural organization and biomechanical properties and, therefore, reinjury is common. The inability of tendon to regenerate after injury, or to heal with mechanical properties comparable to the original tissue, is likely attributable to low vascularity and cellularity of the tissue, low number of resident progenitor cells, and healing under weight-bearing conditions. Strategies to improve tendon healing have focused on enhancing the metabolic response of tenocytes, modulating the organization of the newly synthesized extracellular matrix, or administering progenitor cells to enhance repair. Significant research effort has been directed at the use of adult mesenchymal stem cells as a source of progenitor cells for equine tendon repair and recent clinical applications have utilized adult autologous stem cells derived either from adipose tissue or bone marrow aspirates. Isolation of a homogenous population of stem cells from bone marrow is time-consuming, and there is much variation in cell numbers, cell viability and growth rates among samples. Recently, a population of progenitor cells has been isolated from equine flexor tendons, thus providing an alternative source of progenitor cells from the target tissue for therapeutic intervention. The interaction between cells and the extracellular matrix (ECM) is an important factor in regulation of cell function. Proliferation, migration, differentiation and gene expression of many cell types are altered by adhesion to and interaction with matrix proteins and the extracellular environment. Tendon progenitor cells reside within a niche that comprises primarily parallel collagen fibers, and this niche plays an important role in regulating their function and differentiation. Culture conditions replicating this environment could be beneficial for both cell growth and matrix gene expression. The objectives of the study were to compare cell growth kinetics and biosynthetic capabilities of bone marrow mesenchymal stem cells (BMMSCs) and tendon derived progenitor cells (TPCs) cultured on commercially available bovine, highly purified bovine, porcine, and rattus collagen sources and standard tissue culture surfaces. We hypothesized that collagen type I matrix would preferentially support TPC proliferation and up regulate gene expression for collagens and organizational components of tendon and therefore provide a culture system and progenitor cell type with advantages over the current practice of BMMSC expansion on standard cell culture plastic surfaces. Cells were isolated from 6 young adult horses, expanded, and cultured on collagen-coated tissue culture plates, and no collagen control for 7 days. Samples were analyzed for cell number on days 4 and 7, and for mRNA expression of collagen type I, collagen type III, cartilage oligomeric matrix protein (COMP), and decorin on day 7. Glycosaminoglycan (GAG) synthesis was analyzed on day 7. Differences of cell number between collagen groups and cell type, and in gene expression and GAG synthesis between collagen groups and cell types, were evaluated by use of mixed-model repeated measures ANOVA. Pair-wise comparisons were made on significant differences identified with ANOVA using Tukey's post hoc test. Statistical significance was set at P<0.05. A statistical significant (P=0.05) increase in cell number for TPCs grown on rattus collagen versus control on day 4 was observed. No difference in GAG synthesis or expression of collagen type I, collagen type III, COMP or decorin mRNA was observed between collagen groups and non-collagen controls for either cell type on day 7. TPCs cultured on all collagen types yielded more cells than similarly cultured BMMSCs on day 4, but only porcine collagen was superior on day 7. TPCs synthesized more GAG than BMMSCs when cultured on control surfaces only. BMMSCs expressed more collagen type I mRNA when cultured on control, porcine and highly-purified collagen, and more collagen type III when cultured on control, porcine, highly-purified collagen, and rattus collagen, than TPCs. Tendon-progenitor cells expressed significantly more COMP when cultured on control and all collagen types, and decorin when cultured on porcine, highly purified bovine and bovine collagen when compared to BMMSCs. The results of this study revealed an advantage to culturing TPCs on randomly organized rattus collagen during the early growth phase. The beneficial effects of collagen-coated surfaces on cell proliferation is likely related to increased surface area for attachment and expansion provided by the random collagen matrix, and/or collagen-cell interactions. Tendon progenitor cells showed superior growth kinetics and expression of the matrix organizational components, COMP and decorin, than similarly cultured BMMSCs that expressed more collagen types III and I. TPCs synthesize more GAG compared to BMMSCs when cultured on plastic surfaces and there was no induction by collagen. Tendon progenitor cells should be considered as an alternative source of progenitor cells for injured equine tendons. Further in vitro studies characterizing factors that influence gene expression of both cell types is warranted. / Master of Science

The objective of this study was to evaluate effects of extracorporeal shockwave therapy (ESWT) on spinal mechanical nociceptive threshold (MNT) and multifidus muscle cross-sectional area (CSA) in horses with thoracolumbar pain. We hypothesized that ESWT would increase MNT and multifidus CSA. Twelve horses with thoracolumbar pain were included. Prior to treatment, each thoracolumbar spine was radiographed to document existing pathology. Horses received 3 ESWT treatments, 2 weeks apart (days 0, 14, 28). Palpation scores were documented (days 0, 45, 65) and ultrasonographic CSA of left and right multifidus was recorded at T12, T14, T16, T18, L3 and L5 (days 0, 45, 65). MNT was measured at T12, T14, T16, T18, L3 and L5 every 7 days (day 0-56). Change in MNT in 10/12 horses was significant at each timepoint compared to day 0 (P<0.05). MNT increased at all timepoints at 6 sites in 2/12, at 5 sites in 3/12, at 4 sites in 4/12 and at 1 site in 1/12 (P<0.05). MNT average percent increase from day 0-56 was 64% for T12-T18 and 29% for L3-L5. There was no statistical difference in MNT from day 35-56 (P=0.25). A bimodal analgesic trend was observed following ESWT. Degree of radiographic change was not associated with response to treatment and no significant change in multifidus CSA was observed. In conclusion, 3 treatments of ESWT 2 weeks apart raised MNT over a 56-day period in horses with back pain, but did not influence change in CSA of the multifidus. / Master of Science / Back pain in the horse is a frequently diagnosed and treated cause of back stiffness, lameness, poor performance and/or avoidance behavior under saddle. Treatment is focused on reducing pain and inflammation and on strengthening and promoting proper muscle development to maintain long term results. Recently, rehabilitation of the deep spinal stabilizer multifidus muscle, particularly with regard to increased cross-sectional area (CSA), has become a focus of targeted physiotherapy. Assessment of the degree of pain is subjective due to individual interpretation and palpation technique. In an attempt to standardize quantification of pain, pressure algometry has become a validated, objective and repeatable measure of axial skeleton mechanical nociceptive threshold (MNT), which is defined as the minimum pressure required to induce a pain response. Although many treatment options for back pain exist, there is limited research documenting the efficacy of these treatments in horses. Extracorporeal shockwave therapy (ESWT), which consists of focused, high velocity acoustic waves, is one type of non-invasive, well-tolerated treatment for back pain. Despite its popularity, there is no research documenting the effects of ESWT on equine spinal MNT or multifidus muscle CSA. This is the first study to document the effects of ESWT on spinal MNT and multifidus muscle CSA in horses with back pain. We hope that the results of this study will help guide treatment decisions for horses with back pain.

The respiratory epithelial response of the adult horse was evaluated after being housed on pasture and in an enclosed stable for four week periods. six thoroughbred cross horses, ranging from 3 to 6 years old, were housed on a pasture for 2 months, and evaluated at the end of this period. After an additional month on pasture, horses were then moved to a barn and housed in stalls for four weeks. Samples were obtained at the end of this time and horses were returned to pasture for two months. Final samples were then collected. Each evaluation included a physical examination; cytological evaluation of transtracheal aspirate, and histological evaluation of tracheal epithelial biopsies obtained at the level of the main stem bifurcation. Endoscopic evaluation also permitted scoring of pharyngeal lymphoid hyperplasia, and tracheal mucous secretions. No significant changes were noted in any of the parameters evaluated in this study. These results suggest housing normal horses in a stable environment does not an elicit an immediate change in the volume or composition of epithelial secretions. Evaluation of the tracheal epithelium biopsies also did not reveal histologic changes or inflammatory infiltration in response to short-term housing in the stable environment. / Master of Science

In Part 1, amphotericin B-induced synovitis of the left tarsocrural joint was used to create hindlimb lameness in 11 horses. Caudal epidural catheters were placed and advanced to the lumbosacral region. Baseline heart and respiratory rates were recorded and horses were videotaped at a walk and trot. Treated horses received 0.2 mg/kg morphine sulfate and 30 ug/kg detomidine hydrochloride through the epidural catheter; control horses received an equivalent volume of physiologic saline solution through the catheter. At hourly intervals after epidural injection for a total of 6 hours, heart and respiratory rates were recorded and horses were videotaped walking and trotting. At the end of the observation period, video recordings were scrambled onto a master videotape. Lamenesses were scored by 3 investigators. Lameness grades, heart rates and respiratory rates were compared. There was a significant decrease in lameness grades after treatment with epidural morphine and detomidine. Initially, heart rates significantly increased in control horses and decreased in treated horses. A similar trend occurred for respiratory rates. In Part 2, caudal epidural catheters were used to administer injections to 10 horses every 12 hours for 14 days. Treated horses received 0.2 nlg/kg morphine sulfate and 30 ug/kg detomidine hydrochloride, and control horses received an equivalent volume of physiologic saline solution. Body weights were recorded on days 1 and 14. Rectal temperature, heart rate, respiratory rate and gastrointestinal motility were recorded twice daily, and daily hay and water consumption was measured. Horses were euthanatized day 15. Atlanto-occipital cerebrospinal fluid samples were submitted for bacteriologic culture and determination of white and red blood cell counts and protein and glucose concentrations. Post mortem examinations were performed and representative samples of the spinal cord and surrounding tissues were taken from cervicothoracic, thoracolumbar, lumbosacral, sacral and catheter entry point regions. Spinal tissue segments from these regions were graded for histologic degree of inflammation and fibrosis. Cerebrospinal fluid values and spinal tissue segment inflammation and fibrosis grades were compared between control and treated horses, and between all 10 catheterized study horses and 6 uncatheterized horses. No problems were encountered with epidural catheter maintenance or injection. No significant difference was identified in body weight change, daily variables or hay and water consumption between control and treated horses. All cerebrospinal fluid cultures were negative for growth. No significant difference in cerebrospinal fluid values or spinal tissue inflammation or fibrosis grades for any segment was demonstrated between control and treated horses. However, when compared to uncatheterized horses, cerebrospinal fluid red blood cell counts were marginally higher and protein concentrations were significantly higher in catheterized horses. As well, lumbosacral and sacral spinal tissue segment inflammation grades and sacral segment fibrosis grades were significantly higher in catheterized compared to uncatheterized horses. Results of these studies indicate that an epidural combination of morphine and detomidine provides profound hindlimb analgesia in horses and is not associated with apparent adverse systemic effects. Localized epidural inflammation and fibrosis appear to be catheter-related. / Master of Science

A controlled study was performed to determine the potential toxic effects of the new nonsteroidal anti-inflammatory drug, eltenac (4-[(2,6-dichlorophenyl) amino]-3-thiopheneacetic acid), in horses. Four treatment groups were formed, each composed of 6 horses. The drug was injected intravenously, once daily, at a dose rate of 0.5 mg/kg, 1.5mg/kg or 2.5 mg/kg for 15 days. A control group was injected with sterile saline solution. Parameters assessed were hay and water consumption, daily clinical observations (evaluation of attitude, mentation, pulse and respiratory rate, fecal consistency, skin condition, and color and hydration of mucous membranes), physical examinations, complete hemogram, coagulation profiles, serum biochemical profiles, urinalysis, gastroscopic examinations and gross post-mortem and histopathological examinations on all organ systems. All examiners were blinded to group assignment and dosage levels until the completion of the study. A few glandular gastric ulcers, mild in severity, developed in seven animals during the treatment period. This occurred more often in horses treated with high doses of eltenac (P=.02). A dose dependent change of WBC count and neutrophil count were noted. Total protein, albumin and globulin levels had dose dependent decreases. One horse in the high dose group (2.5mg/kg) developed ventral edema as well as hypoproteinemia. N one of the horses in any of the dosage groups exhibited depression or anorexia. Gross post-mortem and histologic examination did not reveal any signs of drug related gastrointestinal, renal or hepatic abnormalities. Minimal toxic effects of eltenac given intravenously were greatest in horses treated with 2.5 mg/kg of the compound for 15 days. / Master of Science

Two groups of horses were each fed either a control diet of ground hay and concentrates (4 horses), or a Similar diet with 10% added fat after undergoing a baseline Standard Exercise Test (SET). The SET was a stepwise, incremental test to exhaustion on an equine treadmill set at a 6% slope. Resting and working heartrates and rectal temperatures were monitored, and venous blood was collected at rest, and every 3 minutes during exercise, just prior to each speed change. Blood was analyzed for pH, hemoglobin, and pCO₂, and base excess and plasma bicarbonate levels were calculated using nomogram equations. Plasma samples were analyzed for albumin at each step, and for sodium, potassium, chloride, and lactate at rest and exhaustion only. The plasma SID was calculated at rest and exhaustion by the following equation: ([Na⁺] + [K⁺]) - ([Cl⁻] + [Lactate]) The SET was performed after 16 days of interval training, and once more after another 16 days of interval training. Differences over time during exercise were found: heartrate, lactate, and potassium increased (p<.001), and hemoglobin increased (P<.01). Decreases were found in PH, pCO₂, bicarbonate concentration, base excess, and chloride (p<.001). Training effects were found in resting and working heartrates, pCO₂, bicarbonate concentration, and base excess, which all decreased during exercise with training. Hemoglobin increased during exercise with training. There were treatment * SET interactions for Strong Ion Difference, base excess, lactate concentration, pCO₂, and pH. There were no differences found between groups for any of the variables measured. Both groups showed improvements in fitness with training, and the fat group had a higher level of plasma lactate by SET 3. These results suggest that a high fat diet combined with interval training may have some effects on plasma lactate, and that training alone can affect many variables. The results also give evidence to support the evaluation of SID during exercise in horses. / Master of Science

The objective of this study was to purify IgG from commercially available hyperimmune Rhodococcus equi plasma and to assess the delivery of IgG as an aerosol to the equine lung. IgG was purified from plasma, and the IgG concentration of both the plasma and the purified IgG was determined by ELISA. The purified IgG was aerosolized using a vibrating mesh nebulizer and aerosol characterization was performed using cascade impaction. The purified IgG was nebulized to six healthy adult horses in order to assess the efficacy of pulmonary delivery and safety of administration. Bronchoalveolar fluid was retrieved endoscopically using a low volume technique prior to aerosolization (time 0) and at 0.5, 4 and 24 hours post aerosolization. The BAL fluid IgG concentration was determined and cytologic analysis was performed. The IgG concentrations of the plasma and purified IgG were 2,175 mg/dL and 1,145 mg/dL, respectively. The MMAD of the purified IgG aerosol was 4.7 microns. The mean BAL fluid IgG concentration increased 61% from 19.33 µg/dL at time 0 to 31.5 µg/dL at 0.5 hours, but this increase was not significant (P=0.603). No significant change was observed in inflammatory cell numbers over time or at any time point during the study. This study demonstrated that IgG antibodies were purified at a concentration acceptable for nebulization, and that the nebulization unit generated aerosol particles from the IgG solution of appropriate size for pulmonary delivery. Nebulization of purified IgG to adult horses was well tolerated and caused no local or systemic adverse effects. / Master of Science