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Abstract

Objective—To determine the degree to which components of the training program of 2-year-old Thoroughbred racehorses influence their susceptibility to fatigue injury of the third metacarpal bone (bucked shins).

Animals—226 two-year-old Thoroughbred racehorses.

Procedure—Daily training information and health reports on 2-year-old Thoroughbreds were compiled from records provided from 5 commercial stables. For each horse, data (exercise variables) were collected that comprised distance jogged (approx speed of 5 m/s), galloped (approx 11 m/s), and breezed (approx 15 to 16 m/s) until a single instance of bucked shins was reported. Data were coded for analysis using cross-tabulation, graphic, and survival techniques.

Results—Of 226 horses, 56 had bucked shins, 9 completed the observation period without bucked shins, and 161 were lost to follow-up. Distinct training strategies were used at stables resulting in significantly different survival profiles among stables. Mean (± SD) allocation of exercise to breezing was 0.15 ± 0.13 miles/wk (maximum, 0.64 miles/wk), to galloping was 4.47 ± 1.52 miles/wk (maximum, 9.56 miles/wk), and to jogging was 2.34 ± 1.70 miles/wk (maximum, 8.53 miles/wk). Survival (ie, lack of bucked shins during 1 year of monitoring) was found to be significantly reduced by exercise allocation to breezing, significantly increased by exercise allocation to galloping, and uninfluenced by exercise allocation to jogging. The log of the hazard ratio was reduced by 4.2 ± 1.5/mile breezed and increased by 0.3 ± 0.1/mile galloped.

Conclusions and Clinical Relevance—Relationships between different gaits and speeds in the training regimen influence the incidence of bucked shins. To reduce the incidence of bucked shins, trainers should consider allocating more training effort to regular short-distance breezing and less to long-distance galloping. (Am J Vet Res 2000;61:602–608)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate stiffness and bone-pin interface stress for a transcortical tapered-sleeve pin (TSP) that incorporates bilateral tapered sleeves over a transcortical pin.

Sample Population—14 third metacarpal bones (MCIII) collected from adult horses of various breeds.

Procedure—Each MCIII was cut in half to provide 2 test specimens. Pins (conventional and TSP) of 3 diameters (6.35, 7.94, and 9.50 mm) were inserted in specimens (3 specimens for each diameter and each type of pin). The test fixture simulated a typical sidebar- span skeletal fixation device for horses. Single cycle load-deflection tests were performed. Cyclic fatigue tests of TSP were performed to evaluate fatigue characteristics and stress conditions at the bone-pin interface. Maximum stress and strain were calculated, and results were compared with existing data on fatigue characteristics of bone.

Results—Significant increases in stiffness (loaddeflection) and higher loads at yield point were detected for the TSP (stiffness for conventional 9.50- mm pins, 4,500 N/mm; stiffness for TSP, 19,988 N/mm). Results of cyclic tests revealed a close correlation with existing data on fatigue characteristics.

Conclusions and Clinical Relevance—The TSP described here is stiffer than conventional transcortical pins, and stress across the bone-pin interface is more evenly distributed. Use of this TSP should minimize major problems encountered during external fixation associated with the transcortical pin and bone-pin interface (ie, bone necrosis, infection of the pin track, pin loosening, and bone failure). ( Am J Vet Res 2001;62:955–960)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To detect subclinical disseminated intravascular coagulation (DIC) in horses with colitis and to determine any association between the diagnosis of subclinical DIC and outcome or occurrence of complications in horses with colitis.

Design—Prospective study.

Animals—37 horses admitted to a veterinary teaching hospital for treatment of acute colitis.

Procedure—Coagulation profiles were obtained on each horse 0, 24, and 48 hours after admission. Six tests were performed: platelet count, plasma fibrinogen concentration, prothrombin time, activated partial thromboplastin time, antithrombin activity, and serum fibrin degradation products concentration.

Results—A clinicopathologic diagnosis of subclinical DIC was made if 3 of the 6 tests had abnormal results at any 1 sample period. No horse had clinical signs of DIC at the time of sampling. Twelve of 37 (32%) horses met the criteria for diagnosis of subclinical DIC within a 1-year period. Outcome was defined as survival or nonsurvival. Five of 12 horses with subclinical DIC and 2 of 25 horses without subclinical DIC did not survive. Crude odds ratio analysis revealed a horse with acute colitis was 8 times as likely to die or be euthanatized if a diagnosis of subclinical DIC was made.

Conclusions and Clinical Relevance—Clinicopathologic evidence of DIC is common and is significantly associated with a poor outcome in horses with acute colitis. Treatment of subclinical DIC may influence outcome in horses with acute colitis. (J Am Vet Med Assoc 2002;220:1034–1038)

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To identify risk factors for development of acute laminitis in horses during hospitalization for illness or injury.

Design—Retrospective case-control study.

Animals—73 horses that developed laminitis (case horses) and 146 horses that did not develop laminitis (control horses) during hospitalization.

Procedures—Case and control horses were matched in a 2:1 ratio by the date on which each horse was evaluated. Potential risk factors investigated included age, breed, and sex; highest and lowest values recorded during hospitalization for fibrinogen concentration, WBC count, PCV, and total solids concentration; and comorbid disease states, including pneumonia, endotoxemia, diarrhea, medically treated colic, surgically treated colic, pituitary adenoma, retained placenta or metritis, forelimb lameness, hind limb lameness, acute renal failure, and vascular abnormalities. A univariate screening of all potential risk factors was performed to determine which variables should be selected for further analysis. All factors found to be associated with development of laminitis were included in a multivariate conditional logistic regression model.

Results—Development of laminitis was marginally associated with lowest and highest fibrinogen concentrations, highest PCV, and lowest total solids concentration and significantly associated with pneumonia, endotoxemia, diarrhea, abdominal surgery for colic, and vascular abnormalities. In the multivariate analysis, only endotoxemia was significantly associated with laminitis.

Conclusions and Clinical Relevance—Endotoxemia is an important risk factor for development of acute laminitis in horses during hospitalization for medical or surgical conditions. Early recognition of endotoxemia, or the potential for it to develop in certain disease states, and initiation of treatment directed at endotoxemia or its consequences may help prevent laminitis in horses during hospitalization.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To identify factors associated with an increased likelihood that horses would have a serum Streptococcus equi SeM-specific antibody titer ≥ 1:1,600.

Design—Cross-sectional study.

Animals—188 healthy client-owned horses.

Procedures—A single serum sample from each horse was tested for SeM-specific antibody titer with an ELISA. Multivariate logistic regression was used to identify factors associated with having a titer ≥ 1:1,600.

Results—Age, breed, and vaccination status were significantly associated with the likelihood of having a titer ≥ 1:1,600. The odds of having a titer ≥ 1:1,600 increased by a factor of 1.07 with each 1-year increase in age. Quarter Horses and horses of other breeds were 4.08 times as likely as were Thoroughbreds and warmbloods to have a titer this high. Horses that had previously received an intranasal S equi vaccine were 4.7 times as likely as were horses without any history of vaccination to have a titer this high.

Conclusions and Clinical Relevance—Results indicated that older horses, horses other than Thoroughbreds and warmbloods, and horses that had been vaccinated with an attenuated-live intranasal S equi vaccine between 1 and 3 years previously had an increased likelihood of having a serum SeM-specific antibody titer ≥ 1:1,600.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To develop proxies calculated from basal plasma glucose and insulin concentrations that predict insulin sensitivity (SI; L·min–1 ·mU–1) and beta-cell responsiveness (ie, acute insulin response to glucose [AIRg]; mU/L·min–1) and to determine reference quintiles for these and minimal model variables.

Animals—1 laminitic pony and 46 healthy horses.

Procedure—Basal plasma glucose (mg/dL) and insulin (mU/L) concentrations were determined from blood samples obtained between 8:00 AM and 9:00 AM. Minimal model results for 46 horses were compared by equivalence testing with proxies for screening SI and pancreatic beta-cell responsiveness in humans and with 2 new proxies for screening in horses (ie, reciprocal of the square root of insulin [RISQI] and modified insulin-to-glucose ratio [MIRG]).

Results—Best predictors of SI and AIRg were RISQI (r = 0.77) and MIRG (r = 0.75) as follows: SI = 7.93(RISQI) – 1.03 and AIRg = 70.1(MIRG) – 13.8, where RISQI equals plasma insulin concentration–0.5 and MIRG equals [800 – 0.30(plasma insulin concentration – 50)2]/(plasma glucose concentration – 30). Total predictive powers were 78% and 80% for RISQI and MIRG, respectively. Reference ranges and quintiles for a population of healthy horses were calculated nonparametrically.

Conclusions and Clinical Relevance—Proxies for screening SI and pancreatic beta-cell responsiveness in horses from this study compared favorably with proxies used effectively for humans. Combined use of RISQI and MIRG will enable differentiation between compensated and uncompensated insulin resistance. The sample size of our study allowed for determination of sound reference range values and quintiles for healthy horses. (Am J Vet Res 2005;66:2114–2121)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate glucose and lipid metabolism in healthy adult horses administered levothyroxine sodium (L-T4).

Animals—12 healthy adult mares.

Procedure—8 horses received an incrementally increasing dosage of L-T4 (24, 48, 72, or 96 mg of L-T4/d) for weeks 1 to 8. Each dose was provided between 7 AM and 8 AM in the morning grain meal for 2 weeks. Four additional horses remained untreated. Serum concentrations of nonesterified fatty acids, triglyceride (TG), total cholesterol (TC), and very-low-density lipoprotein (VLDL) were measured and composition of VLDL examined in samples obtained between 8 AM and 9 AM at weeks 0, 2, 4, 6, and 8. Glucose dynamics were assessed by use of a combined IV glucose-insulin tolerance test (IVGITT) conducted before and at the end of the 8-week treatment period. Data for each combined IVGITT were interpreted by use of the minimal model.

Results—Plasma TG, TC, and VLDL concentrations significantly decreased over time in treated horses. At the completion of the 8-week treatment period, mean plasma VLDL concentration was 46% of the mean value for week 0 in treated horses. Insulin sensitivity significantly increased (> 2-fold) in treated horses, but glucose effectiveness and net insulin response were not affected. Levothyroxine sodium significantly increased the rate of insulin disposal.

Conclusions and Clinical Relevance—Administration of L-T4 decreases blood lipid concentrations, improves insulin sensitivity, and increases insulin disposal in horses. Levothyroxine sodium may have potential as a treatment for horses with reduced insulin sensitivity. (Am J Vet Res 2005;66:1032–1038)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the pharmacokinetics of methylprednisolone (MP) and develop a pharmacokinetic-pharmacodynamic model of the related changes in plasma concentrations of endogenous hydrocortisone (HYD) and cortisone (COR) following intra-articular administration of methylprednisolone acetate (MPA) in horses.

Animals—6 Thoroughbreds.

Procedures—In each horse, 200 mg of MPA was injected intrasynovially into a carpal joint, and plasma MP, HYD, and COR concentrations were determined via liquid chromatography-mass spectrometry.

Results—A 5-compartment pharmacokinetic-pharmacodynamic model was used to describe the concatenated changes in the plasma concentrations of MP, HYD, and COR and to estimate the instantaneous rate of endogenous HYD production. The median transfer half-life (t1/2t) of methylprednisolone from the joint to plasma and elimination half-life (t1/2e) from plasma were 1.7 and 19.2 hours, respectively. Maximum plasma concentration of methylprednisolone was 7.26 ± 3.3 ng/mL at 8 hours, which decreased to 0.11 ± 0.08 ng/mL at 144 hours after injection. At 3 hours after MPA administration, plasma COR and HYD concentrations were significantly decreased from baseline values (from 2.9 ± 0.28 ng/mL to 2.10 ± 1.0 ng/mL and from 61.1 ± 18.9 ng/mL to 25.7 ± 12.1 ng/mL, respectively).

Conclusions and Clinical Relevance—The sensitivity of the analytic method used allowed complete description of the related kinetics of MP, HYD, and COR following intra-articular administration of MPA. A single intra-articular administration of MPA profoundly affected the secretion of HYD and COR in horses; secretion of endogenous corticosteroids remained suppressed for as long as 240 hours after injection.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the history, clinicopathologic findings, and results of surgery for effusive-constrictive pericarditis associated with Coccidioides immitis infection in dogs.

Design—Retrospective study.

Animals—17 client-owned dogs that underwent a subtotal pericardectomy and epicardial excision.

Procedure—Hospital records from May 1999 to June 2003 were reviewed. Data collected included history, clinicopathologic findings, treatments, and outcome. Follow-up information was obtained via recheck examination and by use of standardized telephone interviews with referring veterinarians and owners.

Results—All dogs were of large breeds, and most were male (mean age, 4.66 years). Ten dogs had no prior history of C immitis infection, and 7 dogs had chronic infection with C immitis. Having a chronic C immitis infection reduced the odds of survival, compared with no previous infection. All dogs had clinical signs of right-sided heart failure. All dogs had serum titers (range, 1:8 to 1:256) for antibodies against C immitis prior to surgery, and titers were not significantly associated with outcome. Predominant echocardiographic findings were thickened pericardium, reduced right ventricular filling, and pleural or pericardial effusion. All dogs underwent a subtotal pericardectomy and epicardial excision and had fibrosing pyogranulomatous pericarditis in biopsy specimens obtained during surgery. The perioperative mortality rate was 23.5%, and the 2-year postdischarge survival rate was 82%.

Conclusions and Clinical Relevance—Surgical treatment via subtotal pericardectomy and epicardial excision is successful at relieving right-sided heart failure in dogs with effusive-constrictive pericarditis secondary to C immitis infection, but long-term treatment with antifungal agents may still be required. (J Am Vet Med Assoc 2005;227:435–440)

Full access
in Journal of the American Veterinary Medical Association

Abstract

OBJECTIVE

A retrospective study was conducted to establish the prerace venous acid-base and blood gas values of Standardbred horses at rest using big data analytics.

SAMPLES

Venous blood samples (73,382) were collected during seven racing seasons from 3 regional tracks in the Commonwealth of Pennsylvania. Horses were detained 2 hours prior to race time.

PROCEDURES

A mixed-effects linear regression model was used for estimating the marginal model adjusted mean (marginal mean) for all major outcomes. The interaction between age and gender, track, and the interaction between month, treatment (furosemide), and year were the major confounders included in the model. Random effects were set on individual animal nested within trainer. Partial pressure of venous carbon dioxide (PVCO2), partial pressure of oxygen (PVO2), and pH were measured, and base excess (BE), total carbon dioxide (TCO2), and bicarbonate (HCO3 ) were calculated.

RESULTS

Significant (P < .001) geographical differences in track locations were seen. Seasonal reductions in acid-base values started in January with significant (P < .001) decreases from adjacent months seen in June, July, and August followed by a gradual return. There were significant increases (P < .001) in BE and TCO2 and decreases in PVO2 with age. Significant differences (P < .001) in acid-base values were seen when comparing genders. A population of trainers were significantly different (P < .001) from the marginal mean and considered outliers.

CLINICAL RELEVANCE

In a population of horses, big data analytics was used to confirm the effects of geography, season, prerace furosemide, gender, age, and trainer influence on blood gases and the acid-base profile.

Open access
in American Journal of Veterinary Research