OBJECTIVE To determine factors affecting race speed in Swedish Standardbred horses undergoing surgery of the carpal flexor sheath (CFS), to investigate whether preoperative racing speed was associated with specific intraoperative findings and whether horses returned to racing, and to compare the performance of horses undergoing surgery of the CFS with that of age- and sex-matched control horses. ANIMALS 149 Swedish Standardbred trotters undergoing surgery of the CFS and 274 age- and sex-matched control horses. PROCEDURES Medical records of CFS horses were examined. Racing data for CFS and control horses were retrieved from official online records. Generalizing estimating equations were used to examine overall and presurgery racing speeds and the association of preoperative clinical and intraoperative findings with preoperative and postoperative speeds. Multivariable regression analysis was used to examine career earnings and number of career races. Kaplan-Meier survival analysis was used to compare career longevity between CFS and control horses. RESULTS CFS horses were significantly faster than control horses. The CFS horses that raced before surgery were slower as they approached the surgery date, but race speed increased after surgery. There were 124 of 137 (90.5%) CFS horses that raced after surgery. No intrathecal pathological findings were significantly associated with preoperative racing speed. Career longevity did not differ between CFS and control horses. CONCLUSIONS AND CLINICAL RELEVANCE Horses undergoing surgery of the CFS had a good prognosis to return to racing after surgery. Racing careers of horses undergoing surgery of the CFS were not significantly different from racing careers of control horses.

OBJECTIVE To determine effects of anesthesia on plasma concentrations and pulsatility of ACTH in samples obtained from the cavernous sinus and jugular vein of horses. ANIMALS 6 clinically normal adult horses. PROCEDURES Catheters were placed in a jugular vein and into the cavernous sinus via a superficial facial vein. The following morning (day 1), cavernous sinus blood samples were collected every 5 minutes for 1 hour (collection of first sample = time 0) and jugular venous blood samples were collected at 0, 30, and 60 minutes. On day 2, horses were sedated with xylazine hydrochloride and anesthesia was induced with propofol mixed with ketamine hydrochloride. Horses were positioned in dorsal recumbency. Anesthesia was maintained with isoflurane in oxygen and a continuous rate infusion of butorphanol tartrate. One hour after anesthesia was induced, the blood sample protocol was repeated. Plasma ACTH concentrations were quantified by use of a commercially available sandwich assay. Generalized estimating equations that controlled for horse and an expressly automated deconvolution algorithm were used to determine effects of anesthesia on plasma ACTH concentrations and pulsatility, respectively. RESULTS Anesthesia significantly reduced the plasma ACTH concentration in blood samples collected from the cavernous sinus. CONCLUSIONS AND CLINICAL RELEVANCE Mean plasma ACTH concentrations in samples collected from the cavernous sinus of anesthetized horses were reduced. Determining the success of partial ablation of the pituitary gland in situ for treatment of pituitary pars intermedia dysfunction may require that effects of anesthesia be included in interpretation of plasma ACTH concentrations in cavernous sinus blood.

Objective-To compare quantitative magnetic resonance (QMR), dual-energy x-ray absorptiometry (DXA), and deuterium oxide (D2O) methods for measurement of total body water (TBW), lean body mass (LBM), and fat mass (FM) in healthy dogs and to assess QMR accuracy. Animals-58 Beagles (9 months to 11.5 years old). Procedures-QMR scans were performed on awake dogs. A D2O tracer was administered (100 mg/kg, PO) immediately before dogs were sedated, which was followed by a second QMR or DXA scan. Jugular blood samples were collected before and 120 minutes after D2O administration. Results-TBW, LBM, and FM determined via QMR were not significantly different between awake or sedated dogs, and means differed by only 2.0%, 2.2%, and 4.3%, respectively. Compared with results for D2O dilution, QMR significantly underestimated TBW (10.2%), LBM (13.4%), and FM (15.4%). Similarly, DXA underestimated LBM (7.3%) and FM (8.4%). A significant relationship was detected between FM measured via D2O dilution and QMR (r2 > 0.89) or DXA (r2 > 0.88). Even though means of TBW and LBM differed significantly between D2O dilution and QMR or DXA, values were highly related (r2 > 0.92). Conclusions and Clinical Relevance-QMR was useful for determining body composition in dogs and can be used to safely and rapidly acquire accurate data without the need for sedation or anesthesia. These benefits can facilitate frequent scans, particularly in geriatric, extremely young, or ill pets. Compared with the D2O dilution method, QMR correction equations provided accurate assessment over a range of body compositions.

Objective: To optimize the use of CT-guided modeling for the calculation of body surface area (BSA) in domestic rabbits (Oryctolagus cuniculus). Animals: 12 domestic rabbits. Procedures: Adult rabbits (body weight, 1 to > 4 kg) that were client-owned animals undergoing CT for disease diagnosis or deceased laboratory animals donated from other research projects were scanned with a CT scanner. Images were transferred to a radiation therapy planning software program. Image slices were captured as contiguous slices at 100 kVp and 100 mA and processed to 0.1-cm-thick sections. The length of each contoured slice was summed to calculate a final BSA measurement. Nonlinear regression analysis was then used to derive an equation for the calculation of BSA in rabbits. Results: The constant calculated by use of this method was 9.9 (range, 9.59 to 10). The R2 for the goodness of fit was 0.9332. The equation that best described BSA as a function of body weight for domestic rabbits with this method was as follows: BSA = (9.9 × [body weight {in grams}]2/3)/10,000. Conclusions and Clinical Relevance: The BSA calculated via the CT-guided method yielded results similar to those obtained with equations for other similarly sized mammals and verified the use of such equations for rabbits. Additionally, this technique can be used for species that lack equations for the accurate calculation of BSA.

Objective--To evaluate 5 commercially available ELISAs for determination of leptin concentrations in serum samples from dogs. Sample Population--Serum samples from overweight-obese and thin–ideal weight clientowned dogs. Procedures--Serum samples with high and low leptin concentrations (n = 7 samples each) were used for validation of the assays. Intra- and interassay precision, linearity under dilution, spiking recovery, and limit of quantification were determined. In addition, leptin concentrations in thin–ideal weight (n = 8) and overweight-obese (37) dogs were quantified. Results--Use of 2 of the 5 ELISAs (A and B) revealed reactivity with canine leptin. Intra-and interassay coefficients of variation were < 6.1% and 76%, respectively, for assay A and 14.0% and 13.7%, respectively, for assay B. In assays A and B, dilutions of canine serum pools were used to determine linear regression equations. Recoveries were 77% to 101% for assay A and 67% to 125% for assay B. Significant differences in leptin concentrations between thin–ideal weight and overweight-obese dogs were detected only when analyzed with assay A. Conclusions and Clinical Relevance--Among 5 leptin ELISAs evaluated, a canine-specific leptin ELISA had adequate precision, linearity, and ability to discriminate between high and low leptin concentrations corresponding to overweight-obese and thin–ideal weight dogs, respectively.

The aim of this study was to evaluate the performance characteristics of an automated immunoassay for canine insulin-like growth factor 1 (IGF-1) measurement and to investigate the possible effects of some sources of variation, such as diurnal variations, feeding/fasting cycles, and glucocorticoid administration, in dogs. The immunoassay evaluated had an adequate analytical performance with intra- and inter-assay coefficients of variation (CVs) lower than 10%, linear regression equations with correlation coefficients of 0.9993 and 0.9988 after serial dilutions, and a limit of quantification of 7.1 ng/mL that was even lower than that reported by the manufacturer. The assay was significantly affected by hemolysis and lipemia producing a significant decrease in IGF-1 concentrations, but not by bilirubinemia. Serum IGF-1 concentrations did not show significant diurnal changes in fed or fasted dogs and were not affected by glucocorticoid administration.

Pharmacokinetic variables of skeletal muscle creatine kinase (CK) activity after IV administration of a muscle extract; CK bioavailability after IM administration of the muscle extract; and effect of IM administration of saline solution, to appreciate the possible release of CK consecutive to muscle puncture, were determined in 6 cows. A general equation for the quantitative estimation of skeletal muscle damage also was derived. Administration of saline solution IM had no effect on plasma CK activity (ANOVA, P > 0.05) in any of the cows. After IV administration of the muscle extract (150 U/kg of body weight), mean volume of the central compartment, plasma half-life, and plasma clearance of CK were 0.027 +/- 0.007 L/kg, 520 +/- 109 minutes, and 6.43 +/- 2.29 ml/kg/h, respectively. After IM administration (150 U/kg), mean bioavailability of CK was 51 +/- 17% and maximal plasma CK activity (500 +/- 97 U/L) was observed at 454 +/- 131 minutes. The rate of CK activity entry into plasma was determined by use of deconvolution analysis. Two peaks were observed; the first appeared before the 30th minute after IM administration, and the second appeared at 3.3 +/- 1.1 hours. Amplitudes were 6.31 +/- 4.45 and 6.57 +/- 3.08 U/kg/h, for the first and the second peaks, respectively. The quantity of CK liberated from control muscle was 0.69 +/- 0.12 U/kg/h, corresponding to a normal daily catabolism of 5.8 +/- 1.0 mg of muscle/kg. From these results, the following equation can be proposed to determine the corresponding mean equivalent of destroyed muscle (Qmuscle, test article) after IM administration of a test article: Qmuscle, test article (g/kg) = 4.41 X 10(-6) AUC (U/h/L), with AUC being the CK plasma activity area under the curve.

OBJECTIVE To determine values of F-wave parameters for the tibial nerve in clinically normal Miniature Dachshunds and those with thoracolumbar intervertebral disk herniation (IVDH). ANIMALS 53 Miniature Dachshunds (10 clinically normal and 43 with various clinical grades of thoracolumbar IVDH). PROCEDURES F-waves were elicited in the interosseous muscles of 1 hind limb in each dog by stimulation of the tibial nerve. F-wave parameters were measured for 32 stimuli/dog, and mean values were calculated. Linear regression was performed to assess correlations between F-wave parameters and clinical severity of IVDH. RESULTS For clinically normal dogs, mean ± SD values of shortest F-wave latency, mean F-wave conduction velocity, mean F-wave duration, and ratio of the mean F-wave amplitude to M response amplitude were 8.6 ± 0.6 milliseconds, 83.7 ± 6.1 m/s, 6.6 ± 1.5 milliseconds, and 9.8 ± 8.5%, respectively. F-wave persistence was 100%. Mean F-wave duration was positively correlated with clinical grade of IVDH. Linear regression yielded the following regression equation: F-wave duration (milliseconds) = 6.0 + 2.7 × IVDH grade. One dog with grade 2 IVDH had a mean F-wave duration shorter than that of all 5 dogs with grade 1 IVDH; 1 dog with grade 3 IVDH had a longer duration than that of all 10 dogs with grade 4 IVDH. CONCLUSIONS AND CLINICAL RELEVANCE Mean F-wave duration was correlated with the severity of inhibitory motor tract dysfunction in the spinal cord of dogs. F-wave examination may be useful for objective functional evaluation of upper motor neurons in the spinal cord.

OBJECTIVE To assess differences in skin shrinkage between grossly visible tumor and grossly normal marginal skin of dogs for cutaneous mast cell tumors (MCTs) excised with curative intent and to determine an equation to estimate postexcisional gross tumor margins from preexcisional measurements and vice versa. SAMPLE 19 cytologically confirmed and surgically excised cutaneous MCTs obtained from dogs. PROCEDURES Tumors were measured in craniocaudal and dorsoventral directions before excision, immediately after excision, and after fixation in formalin. Both grossly visible tumor and surrounding grossly normal skin that comprised the surgical margin were measured at each time point. Percentage of shrinkage was compared among time points and between the tumor and surrounding grossly normal skin. Patient and histopathologic variables were correlated to skin shrinkage. RESULTS Overall shrinkage was 17.70%. The amount of shrinkage within the grossly visible tumor (4.45%) was less than that within the surrounding grossly normal skin (24.42%). Most of the shrinkage occurred immediately after excision. There was no effect of age, sex, completeness of excision, or degree of edema. Accuracy of an equation to estimate postexcisional margins from preexcisional measurements was only 18.4%. CONCLUSIONS AND CLINICAL RELEVANCE Grossly evident MCTs of dogs shrunk less than did the grossly normal surrounding skin. Although an equation to estimate postexcisional margins from preexcisional measurements could be derived, it likely would need to contain additional variables not included in the study reported here. Until such an equation exists, care must be used when extrapolating surgical margins from histologic margins and vice versa.

Few antimicrobials are licensed for use in sheep in Canada, and the range of indications is narrow. Treatment in an “extra-label” manner may be ineffective. In addition, potentially harmful drug residues in food-animal products and antimicrobial resistance in bacteria may be associated with extra-label drug use (ELDU). No data had been documented on drug use, specifically antimicrobial use (AMU), in Ontario sheep, although it was thought that much use was extra-label. This study investigated AMU and ELDU on 49 lamb-producing Ontario sheep farms. Data were prospectively collected over 12 months from the participating farms, and farm-level practices were ascertained with a questionnaire. Treatment-level and farm-level variables were investigated for associations with rates of AMU by means of Poisson rate regression models fit with a generalized estimating equation to control for clustering at the farm level. Antimicrobials with high mean exposure rates included chlortetracycline (in feed), penicillins, and oxytetracycline. The exposure rate in lambs was significantly lower (P < 0.01) with antimicrobial treatment of systemic signs, respiratory disease, or wound or injury than with treatment of other reported diseases or conditions; it was also significantly lower with 3 or more lambing periods per year (α = 0.05). The exposure rate in adult sheep was significantly lower with treatment of 5 of the 6 most prevalent diseases or conditions (α = 0.05) and significantly higher with producer decision to treat and producer experience of 20 y or greater. Rates of using antimicrobials not licensed for use in sheep were high, as was extra-label use of licensed antimicrobials. Diseases reportedly treated most often with antimicrobials (e.g., systemic signs, mastitis) were significantly associated with lower rates of ELDU (α = 0.05). Compared with the rates in adult sheep, the mean rate of use of nonlicensed antimicrobials was similar in the lambs, whereas the mean rate of extra-label use of licensed antimicrobials was lower among the lambs. The results are useful in determining if public health concerns about antimicrobial use in Ontario sheep are warranted and in creating drug use and licensure strategies for the Canadian sheep industry.