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
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)
Objective—To evaluate stiffness and bone-pin interface
stress for a transcortical tapered-sleeve pin (TSP)
that incorporates bilateral tapered sleeves over a
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
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.
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
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)
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.
Objective—To identify factors associated with an increased likelihood that horses would have a serum Streptococcus equi SeM-specific antibody titer ≥ 1:1,600.
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.
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
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
Objective—To evaluate glucose and lipid metabolism
in healthy adult horses administered levothyroxine
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)
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.
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.
Objective—To determine the history, clinicopathologic
findings, and results of surgery for effusive-constrictive
pericarditis associated with Coccidioides
immitis infection in dogs.
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)
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.
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.
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.
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.
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.