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Abstract

Objective—To determine the effects of long-term oral administration of levothyroxine sodium (L-T4) on glucose dynamics in adult euthyroid horses.

Animals—6 healthy adult mares.

Procedures—Horses received L-T4 (48 mg/d) orally for 48 weeks. Frequently sampled IV glucose tolerance test procedures were performed on 3 occasions (24-hour intervals) before and at 16, 32, and 48 weeks during the treatment period. Data were assessed via minimal model analysis. The repeatability of measurements was evaluated.

Results—During treatment, body weight decreased significantly from the pretreatment value; mean ± SD weight was 49 ± 14 kg, 43 ± 7 kg, and 25 ± 18 kg less than the pretreatment value at weeks 16, 32, and 48, respectively. Compared with pretreatment findings, 1.8-, 2.4-, and 1.9-fold increases in mean insulin sensitivity (SI) were detected at weeks 16, 32, and 48, respectively; SI was negatively correlated with body weight (r = −0.42; P < 0.001). During treatment, glucose effectiveness increased and the acute insulin response to glucose decreased. Overall mean within-horse coefficients of variation were 5% and 29% for plasma glucose and serum insulin concentrations, respectively, and 33%, 26%, and 23% for SI, glucose effectiveness, and the acute insulin response to glucose, respectively.

Conclusions and Clinical Relevance—Long-term administration of L-T4 was associated with weight loss and increased SI in adult euthyroid horses, although other factors may have confounded results. Levothyroxine sodium may be useful for the treatment of obesity and insulin resistance in horses, but further studies are required.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate equids with enostosis-like lesions (ELLs) and document the clinical and epidemiological features of this disease.

Design—Retrospective case series.

Animals—79 equids with a scintigraphic diagnosis of at least 1 ELL on ≥ 1 occasion.

Procedures—Medical records of 4,992 equids that underwent bone scintigraphy between March 1997 and March 2009 were reviewed; 78 horses and 1 pony had a scintigraphic diagnosis of an ELL. For those equids, signalment; physical, scintigraphic, radiographic, and lameness examination results; and outcome were reviewed.

Results—Of the 79 equids, 4 (5.1%) had anatomically distinct ELLs on 2 (n = 3) or 4 (1) separate occasions that caused lameness in different limbs. Thus, there were 85 ELL-related admissions to the hospital. Overall, 157 ELLs were detected. Among all equids undergoing scintigraphic examination, Thoroughbreds were more commonly and Standardbreds were less commonly affected. Older animals were more likely to have ELLs. Lameness was directly attributed to scintigraphically evident ELLs in 42 of the 85 (49.4%) admissions. The tibia (62/157 [39.5%]) and the radius (46/157 [29.3%]) were most commonly affected. The ELLs located in the humerus caused more severe lameness than did ELLs in other anatomic locations. Lameness severity was associated with radiopharmaceutical uptake intensity. Among racehorses, those with 1 ELL were more likely to return to racing than were those with multiple ELLs detected in 1 scintigraphic examination; mean interval from diagnosis to first start was 184 days.

Conclusions and Clinical Relevance—Results of this retrospective evaluation of a large group of equids with ELLs have provided a better understanding of this disease process.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine racing performance after surgery for colic in Thoroughbreds.

Design—Retrospective cohort study.

Animals—85 racing Thoroughbreds that survived to discharge following colic surgery and 170 race-matched reference horses.

Procedures—Earnings, starts, and earnings per start were compared between horses that underwent surgery and reference horses, the proportions of horses that returned to racing were analyzed, and career longevity was determined.

Results—Among 85 racing Thoroughbreds that underwent colic surgery, 31 (36%) had primarily small intestinal lesions, of which 11 underwent resection; 54 (64%) had large intestinal lesions, of which 2 underwent resection. Fifty-nine of 85 (69%) horses that underwent colic surgery returned to racing after a 6-month recovery period versus 125 of 170 (73%) reference horses (OR, 0.81). In the 36-month postoperative period, reference horses earned a mean of $7,866 more, had a mean of 0.26 more starts, and had mean earnings per start of $29 more than horses that underwent surgery. Horses that underwent surgery did not have different career lengths than reference horses.

Conclusions and Clinical Relevance—Horses that underwent colic surgery did not have a significant reduction in measures of performance or career length, compared with a reference cohort.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To investigate the effects of dexamethasone or levothyroxine sodium on endotoxin-induced alterations in glucose and insulin dynamics.

Animals—24 horses.

Procedures—Horses were randomly allocated to 3 treatment groups and received 48 mg of levothyroxine mixed with 200 g of oats, 20 mg of dexamethasone plus oats, or oats alone (control) for 15 days, followed by IV infusion of lipopolysaccharide (20 ng/kg) while individually housed in stalls. Frequently sampled IV glucose tolerance tests were performed prior to pretreatment, after pretreatment, and 20 hours after lipopolysaccharide administration. Area under the curve for plasma glucose and serum insulin concentrations was calculated, and minimal model analyses were performed.

Results—Significant treatment-by-time effects were detected for insulin sensitivity (SI) and area under the curve for glucose and insulin in the 15-day pretreatment period. Insulin sensitivity significantly decreased over time in all treatment groups, with the largest decrease detected in the dexamethasone group. Administration of lipopolysaccharide further decreased mean SI by 71% and 63% in the dexamethasone and control groups, respectively, but did not affect horses in the levothyroxine group. Mean SI was the lowest in the dexamethasone group, but percentage reduction was the same for dexamethasone and control groups.

Conclusions and Clinical Relevance—Insulin sensitivity decreased during the pretreatment period in all 3 groups, indicating that hospitalization affected glucose and insulin dynamics. Dexamethasone significantly lowered SI, and endotoxemia further exacerbated insulin resistance. In contrast, there was no additional effect of endotoxemia on SI in horses pretreated with levothyroxine, suggesting that this treatment prevented endotoxemia-induced insulin resistance.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To develop and psychometrically test an owner self-administered questionnaire designed to assess severity and impact of chronic pain in dogs with osteoarthritis.

Sample Population—70 owners of dogs with osteoarthritis and 50 owners of clinically normal dogs.

Procedures—Standard methods for the stepwise development and testing of instruments designed to assess subjective states were used. Items were generated through focus groups and an expert panel. Items were tested for readability and ambiguity, and poorly performing items were removed. The reduced set of items was subjected to factor analysis, reliability testing, and validity testing.

Results—Severity of pain and interference with function were 2 factors identified and named on the basis of the items contained in them. Cronbach's α was 0.93 and 0.89, respectively, suggesting that the items in each factor could be assessed as a group to compute factor scores (ie, severity score and interference score). The test-retest analysis revealed κ values of 0.75 for the severity score and 0.81 for the interference score. Scores correlated moderately well (r = 0.51 and 0.50, respectively) with the overall quality-of-life (QOL) question, such that as severity and interference scores increased, QOL decreased. Clinically normal dogs had significantly lower severity and interference scores than dogs with osteoarthritis.

Conclusions and Clinical Relevance—A psychometrically sound instrument was developed. Responsiveness testing must be conducted to determine whether the questionnaire will be useful in reliably obtaining quantifiable assessments from owners regarding the severity and impact of chronic pain and its treatment on dogs with osteoarthritis.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To define the learning curve and evaluate the outcome for a board-certified veterinary surgeon performing laparoendoscopic single-site (LESS) ovariectomy in dogs.

Design—Retrospective case review and learning curve evaluation with a skill acquisition model.

Animals—27 client-owned dogs.

Procedures—Between April 2011 and December 2012, 27 dogs underwent elective LESS ovariectomy performed by a single experienced board-certified laparoscopic surgeon by means of the same technique. Medical records for these patients were reviewed to determine whether a learning curve could be detected. A commercially available multitrocar port was inserted through a 15- to 20-mm incision at the umbilicus, and LESS ovariectomy was performed with articulating graspers, a bipolar vessel-sealing device, and a 30° telescope. Surgical performance of the surgeon was quantified with an exponential skill acquisition model, and how skill was gained with repetition of the same novel surgical procedure was examined.

Results—Median patient body weight was 20 kg (44 lb; range, 3.5 to 41 kg [7.7 to 90.2 lb]). Median surgical time was 35 minutes (range, 20 to 80 minutes). Median patient age was 314 days (range, 176 to 2,913 days). The skill acquisition model revealed that a comparable surgeon could reach 90% of optimal surgery performance after approximately 8 procedures (8.6, 95% confidence interval, 0.5 to 16.6 procedures). According to the model, with each surgery, surgical time would be expected to decrease by 27% (95% confidence interval, 2% to 52%). Complications were limited to minor hemorrhage due to a splenic laceration and a postoperative incisional infection. Follow-up information was available for all 27 cases. All owners were satisfied and indicated that they would pursue LESS ovariectomy again.

Conclusions and Clinical Relevance—The learning curve for LESS ovariectomy was short and definable. Short-term outcome was excellent. Results of this study suggested that an experienced laparoscopic surgeon may anticipate achieving proficiency with this technique after performing approximately 8 procedures.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine whether the Canine Brief Pain Inventory (CBPI) can detect changes in dogs with osteoarthritis treated with an NSAID or a placebo.

Design—Double-blind, randomized, placebo-controlled clinical trial.

Animals—70 dogs with osteoarthritis.

Procedures—Owners completed the CBPI on day 0. Dogs received carprofen or a placebo on days 1 through 14. Owners completed the CBPI again on day 14. Pain severity and pain interference scores from the CBPI were calculated, and the change from day 0 to day 14 was assessed within each group and between groups.

Results—No significant differences were detected in median scores for pain severity (3.50 and 3.25 on days 0 and 14, respectively) and pain interference (3.92 and 3.25 on days 0 and 14, respectively) in dogs receiving the placebo. Dogs receiving carprofen had significant changes in median scores for pain severity (4.25 to 2.25 on days 0 and 14, respectively) and pain interference (4.33 to 2.67 on days 0 and 14, respectively). There was a significantly greater improvement in pain severity and pain interference scores in dogs treated with carprofen, compared with improvement in scores for dogs receiving the placebo.

Conclusions and Clinical Relevance—The CBPI was able to detect improvements in pain scores in dogs with osteoarthritis treated with an NSAID or a placebo. These results, in combination with previous reliability and validity testing, support the use of the CBPI to obtain quantifiable assessments from owners regarding the severity and impact of chronic pain and treatment for dogs with osteoarthritis.

Full access
in Journal of the American Veterinary Medical Association

Abstract

OBJECTIVE To assess insulin, glucagon, and somatostatin expression within pancreatic islets of horses with and without insulin resistance.

ANIMALS 10 insulin-resistant horses and 13 insulin-sensitive horses.

PROCEDURES For each horse, food was withheld for at least 10 hours before a blood sample was collected for determination of serum insulin concentration. Horses with a serum insulin concentration < 20 μU/mL were assigned to the insulin-sensitive group, whereas horses with a serum insulin concentration > 20 μU/mL underwent a frequently sampled IV glucose tolerance test to determine sensitivity to insulin by minimal model analysis. Horses with a sensitivity to insulin < 1.0 × 10−4 L•min−1•mU−1 were assigned to the insulin-resistant group. All horses were euthanized with a barbiturate overdose, and pancreatic specimens were harvested and immunohistochemically stained for determination of insulin, glucagon, and somatostatin expression in pancreatic islets. Islet hormone expression was compared between insulin-resistant and insulin-sensitive horses.

RESULTS Cells expressing insulin, glucagon, and somatostatin made up approximately 62%, 12%, and 7%, respectively, of pancreatic islet cells in insulin-resistant horses and 64%, 18%, and 9%, respectively, of pancreatic islet cells in insulin-sensitive horses. Expression of insulin and somatostatin did not differ between insulin-resistant and insulin-sensitive horses, but the median percentage of glucagon-expressing cells in the islets of insulin-resistant horses was significantly less than that in insulin-sensitive horses.

CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that, in insulin-resistant horses, insulin secretion was not increased but glucagon production might be downregulated as a compensatory response to hyperinsulinemia.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare cardiac output measured in the pulmonary artery and a carotid artery by use of thermal and electrical impedance dilution.

Animals—7 fit, clinically normal Standardbreds between 2 and 5 years of age.

Procedure—Transient changes in electrical impedance and temperature of blood were induced by bolus injections of ice-cold saline hypertonic (6% and 9% NaCl) solutions. Cardiac output was calculated by applying Stewart-Hamilton principles to the indicator dilution transients. Measurements were made during sequential exercise episodes on a level treadmill over approximately an 8-fold range of cardiac output values.

Results—We detected agreement between cardiac output determined by use of electrical impedance dilution at the pulmonary artery and carotid artery. Cardiac output from thermal dilution measured at the carotid artery exceeded that measured at the pulmonary artery. Cardiac output from the thermal dilution technique exceeded cardiac output from the electrical impedance dilution technique at both locations.

Conclusions and Clinical Relevance—The electrical impedance indicator is conserved on first transit; therefore cardiac output measured by electrical impedance dilution at the carotid artery is reliable over a large range of values. Thermal dilution provides a larger estimate of cardiac output, compared with the electrical impedance dilution technique, probably because of a loss of indicator. The transpulmonary electrical impedance dilution technique may have potential for clinical application, particularly in animals in which catheterization of the pulmonary artery is not appropriate or blood loss must be minimized. (Am J Vet Res 2005;66:878–884)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To investigate the effects of enrofloxacin and magnesium deficiency on explants of equine articular cartilage.

Sample Population—Articular cartilage explants and cultured chondrocytes obtained from adult and neonatal horses.

Procedure—Full-thickness explants and cultured chondrocytes were incubated in complete or magnesium- deficient media containing enrofloxacin at concentrations of 0, 1, 5, 25, 100, and 500 µg/ml. Incorporation and release of sulfate 35S over 24 hours were used to assess glycosaminoglycan (GAG) synthesis and degradation. An assay that measured binding of dimethylmethylene blue dye was used to compare total GAG content between groups. Northern blots of RNA from cultured chondrocytes were probed with equine cDNA of aggrecan, type-II collagen, biglycan, decorin, link protein, matrix metalloproteinases 1, 3, and 13, and tissue inhibitor of metalloproteinase 1.

Results—A dose-dependent suppression of 35S incorporation was observed. In cartilage of neonates, 35S incorporation was substantially decreased at enrofloxacin concentrations of 25 mg/ml. In cartilage of adult horses, 35S incorporation was decreased only at enrofloxacin concentrations of ≥ 100 µg/ml. Magnesium deficiency caused suppression of 35S incorporation. Enrofloxacin or magnesium deficiency did not affect GAG degradation or endogenous GAG content. Specific effects of enrofloxacin on steadystate mRNA for the various genes were not observed.

Conclusion and Clinical Relevance—Enrofloxacin may have a detrimental effect on cartilage metabolism in horses, especially in neonates. (Am J Vet Res 2001;62:160–166)

Full access
in American Journal of Veterinary Research