OBJECTIVE To test the hypothesis that once-daily oral administration of atenolol would attenuate the heart rate response to isoproterenol for 24 hours. ANIMALS 20 healthy dogs. PROCEDURES A double-blind randomized placebo-controlled crossover study was conducted. Dogs were assigned to receive atenolol (1 mg/kg, PO, q 24 h) or a placebo for 5 to 7 days. After a washout period of 7 days, dogs then received the other treatment. Heart rate at rest (HRr) and heart rate induced by administration of isoproterenol (HRi) as a constant rate infusion (0.2 μg/kg/min for 5 to 7 minutes) were obtained by use of ECG 0, 0.25, 3, 6, 12, 18, and 24 hours after administration of the final dose of atenolol or the placebo. A mixed-model ANOVA was used to evaluate effects of treatment, time after drug or placebo administration, treatment-by-time interaction, period, and sequence on HRr and HRi. RESULTS Effects of sequence or period were not detected. There was a significant effect of treatment and the treatment-by-time interaction on HRi. Atenolol significantly attenuated HRi for 24 hours but did so maximally at 3 hours (least squares mean ± SE, 146 ± 5 beats/min and 208 ± 5 beats/min for atenolol and placebo, respectively). The effect at 24 hours was small (193 ± 5 beats/min and 206 ± 5 beats/min for atenolol and placebo, respectively). Atenolol had a small but significant effect on HRr. CONCLUSIONS AND CLINICAL RELEVANCE This study of healthy dogs receiving atenolol supported a recommendation for a dosing interval < 24 hours.

OBJECTIVE To assess the feasibility of esophageal insufflation CT (EICT) for evaluation of the esophagus in dogs. ANIMALS 7 clinically normal adult Beagles. PROCEDURES Each dog was anesthetized twice with 1 week between anesthesia sessions. Dogs were positioned in sternal recumbency during all CT scans. During the first anesthesia session, a CT scan was performed before the esophagus was insufflated (insufflation pressure, 0 mm Hg) and unenhanced and contrast-enhanced EICT scans were performed after CO(2) was insufflated into the esophageal lumen to achieve a pressure of 5 mm Hg. For the contrast-enhanced scan, each dog received iohexol (600 mg/kg, IV), and the scan was performed 30 seconds later. During the second anesthesia session, unenhanced and contrast-enhanced EICT scans were performed in the same manner except the insufflation pressure achieved was 10 mm Hg. The esophageal luminal cross-sectional area and wall thickness were measured at each of 5 segments, and mean values were compared among the 3 insufflation pressures and between unenhanced and contrast-enhanced images. RESULTS Mean esophageal luminal cross-sectional area increased and esophageal wall thickness decreased as insufflation pressure increased. Measurements did not differ significantly between unenhanced and contrast-enhanced images. The stomach became distended with CO(2) at an insufflation pressure of 10 mm Hg but not at 5 mm Hg. No adverse effects were observed. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested EICT was feasible for esophageal evaluation in dogs. Further research is necessary to determine the optimal insufflation pressure for the procedure and its diagnostic efficacy in diseased patients.

OBJECTIVE To radiographically compare patellar ligament length (PLL) in dogs undergoing tibial plateau leveling osteotomy (TPLO) for unilateral cranial cruciate ligament rupture at preoperative, postoperative, and follow-up evaluations. ANIMALS 105 dogs that underwent TPLO for unilateral cranial cruciate ligament rupture at a referral veterinary hospital from October 1, 2008, through November 30, 2017. PROCEDURES Medical records were reviewed to obtain information on dog signalment, surgical procedure, and radiographically measured PLL at preoperative, postoperative, and follow-up evaluations. RESULTS Dogs undergoing TPLO had a shorter PLL at the postoperative and follow-up evaluations, compared with the PLL at the preoperative evaluation. Mean ± SD overall unadjusted PLL decreased significantly by 2.3 ± 3.4% between the preoperative and postoperative evaluation and by 2.8 ± 3.9% between the preoperative and follow-up evaluation. The PLL did not differ significantly between the postoperative and follow-up evaluation; mean PLL decreased by 0.4 ± 3.8% between the postoperative and follow-up evaluation. CONCLUSIONS AND CLINICAL RELEVANCE The PLL was shorter after TPLO in dogs, which was similar to changes observed for humans after high tibial osteotomy procedures. Further evaluation of clinical assessments, joint mobility, ultrasonographic assessments, and kinematic results are needed to determine the relevance of the PLL and whether a decrease in ligament length results in decreased mobility and persistent lameness in dogs, as has been reported for humans.

OBJECTIVE To evaluate accuracy of articular surfaces determined by use of 2 perpendicular CT orientations, micro-CT, and laser scanning. SAMPLE 23 cat cadavers. PROCEDURES Images of antebrachia were obtained by use of CT (voxel size, 0.6 mm) in longitudinal orientation (CTLO images) and transverse orientation (CTTO images) and by use of micro-CT (voxel size, 0.024 mm) in a longitudinal orientation. Images were reconstructed. Craniocaudal and mediolateral length, radius of curvature, and deviation of the articular surface of the distal portion of the radius of 3-D renderings for CTLO, CTTO, and micro-CT images were compared with results of 3-D renderings acquired with a laser scanner (resolution, 0.025 mm). RESULTS Measurement of CTLO and CTTO images overestimated craniocaudal and mediolateral length of the articular surface by 4% to 10%. Measurement of micro-CT images underestimated craniocaudal and mediolateral length by 1%. Measurement of CTLO and CTTO images underestimated mediolateral radius of curvature by 15% and overestimated craniocaudal radius of curvature by > 100%; use of micro-CT images underestimated them by 3% and 5%, respectively. Mean ± SD surface deviation was 0.26 ± 0.09 mm for CTLO images, 0.30 ± 0.28 mm for CTTO images, and 0.04 ± 0.02 mm for micro-CT images. CONCLUSIONS AND CLINICAL RELEVANCE Articular surface models derived from CT images had dimensional errors that approximately matched the voxel size. Thus, CT cannot be used to plan conforming arthroplasties in small joints and could lack precision when used to plan the correction of a limb deformity or repair of a fracture.

The objectives of this study were to describe the frequency of antimicrobial resistance (AMR) in Escherichia coli and Campylobacter spp. isolates in fecal samples from beef cow-calf herds and to examine the associations between herd management practices, reported antimicrobial use, and AMR. Baseline prevalence data are needed to evaluate the effectiveness of antimicrobial stewardship programs. A pooled fecal sample, representing 20 cows, was collected from each of 107 herds during pregnancy testing. In the 305 recovered E. coli isolates (maximum 3 per herd), resistance to ≥ 1 antimicrobial was identified in 12 isolates [4%, 95% confidence interval (CI): 2% to 7%] from 105 herds (11%, 95% CI: 7% to 19%). The most common resistances identified in E. coli isolates were to tetracycline (3%) and to both streptomycin and sulfisoxazole (3%). Only 1 E. coli isolate was resistant to an antimicrobial of very high importance to human health - amoxicillin/clavulanic acid. However, 2 E. coli isolates had intermediate susceptibility to ciprofloxacin. Resistance to 1 antimicrobial was identified in 16 of 87 Campylobacter spp. isolates (18%, 95% CI: 11% to 28%) from 87 herds. Resistance to tetracycline was reported in 15% of Campylobacter spp. isolates and to nalidixic acid in 3.4%. Herds in which cows were treated with florfenicol were more likely to have E. coli resistance to ≥ 2 antimicrobials (OR 7.1, 95% CI: 1.1 to 57, P = 0.03). Herds with calf mortality of > 5% were more likely to have E. coli with resistance to streptomycin and sulfisoxazole [odds ratio (OR): 7.8, P = 0.03]. The results of this study are consistent with previous reports from western Canada and provide a starting point for designing an ongoing antimicrobial surveillance program.

OBJECTIVE To quantify the magnitude and duration of changes in urine chondroitin sulfate concentration (uCS) as a result of oral administration of a chondroitin sulfate–containing supplement in dogs. ANIMALS 8 healthy privately owned dogs. PROCEDURES A urine sample was collected from each dog via cystocentesis on day 1; free-catch midstream urine samples were collected once daily on days 2 through 5. Pretreatment uCS was established from those samples. Each dog then received a chondroitin sulfate–containing supplement (20 to 30 mg/kg, PO, q 12 h) for 8 days (on days 7 through 14). Urine samples were collected on days 8 through 12 and day 15. For each sample, uCS was quantified by liquid chromatography–tandem mass spectrometry. Variable urine concentration was accounted for by dividing the uCS by urine creatinine concentration (uCrea) to determine the uCS:uCrea ratio. Pretreatment uCS:uCrea ratios were compared with treatment uCS:uCrea ratios to calculate the fold change in uCS after supplement administration. RESULTS Among the study dogs, oral administration of the chondroitin sulfate–containing supplement resulted in a 1.9-fold increase in the median uCS:uCrea ratio. Data obtained on days 8 through 12 and day 15 indicated that the daily increase in uCS remained consistent and was not additive. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that oral administration of supplemental chondroitin sulfate to dogs modestly increased uCS within 24 hours; however, subsequent supplement administration did not have an additive effect. A potential therapeutic benefit of persistently increased uCS in preventing recurrent urinary tract infections in dogs warrants investigation.

The goal of this study was to explore and describe fecal microbiota of captive and wild bobcats (Lynx rufus) and compare the results to those of domestic cats (Felis catus). Fecal samples from 27 bobcats (8 wild, 19 zoo-kept) were used for novel bacterial deoxyribonucleic acid (DNA) identification using next-generation sequencing of the V4 region of the bacterial 16S ribosomal ribonucleic acid (rRNA) gene, analyzed by Illumina sequencing, and then compared to data obtained from a colony of 10 domestic cats. In this study, the microbiota of both species was dominated by Firmicutes, followed by Proteobacteria, Actinobacteria, Bacteroidetes, and Verrucomicrobia. When compared, fecal samples from bobcats harbored more Proteobacteria and Actinobacteria than fecal samples from domestic cats. There was a remarkable inter-bobcat variation in the relative abundances of the main bacterial genera. There were no significant differences, however, between the main phyla of the microbiota of the wild and domestic bobcats. Proteobacteria in wild bobcats (P = 0.079) and Firmicutes in zoo-kept bobcats (P = 0.079) approached significance. There were no differences in predominant genera between wild and captive bobcats. The results of this study showed that there are notable differences in fecal bacterial communities between domestic cats and both captive and wild bobcats. The lack of significant differences in bacterial communities between wild and zoo-kept bobcats suggests that the varied diet provided for these felids can result in a fecal microbiota resembling that generated by a wild diet.

OBJECTIVE To determine whether therapeutic concentrations (> 0.5 to 1.0 μg/mL) of polymyxin B (PB) were achieved in the tarsocrural joint of horses when the drug was administered by IV regional limb perfusion (IV-RLP) via a saphenous vein at doses of 25, 50, and 300 mg and to describe any adverse systemic or local effects associated with such administration. ANIMALS 9 healthy adult horses. PROCEDURES In the first of 2 experiments, 6 horses each received 25 and 50 mg of PB by IV-RLP via a saphenous vein with at least 2 weeks between treatments. For each treatment, a tourniquet was placed at the midmetatarsus and another was placed midway between the stifle joint and tarsus. Both tourniquets were removed 30 minutes after the assigned dose was administered. Blood and tarsocrural joint fluid samples were collected for determination of PB concentration before and at predetermined times after drug administration. In experiment 2, 4 horses were administered 300 mg of PB by IV-RLP in 1 randomly selected pelvic limb in a manner identical to that used in experiment 1. RESULTS For all 3 doses, the mean synovial fluid PB concentration was > 10 times the therapeutic concentration and below the level of quantification at 30 and 1,440 minutes after drug administration, respectively. No adverse systemic or local effects were observed following PB administration. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that IV-RLP of PB might be a viable alternative for treatment of horses with synovial infections caused by gram-negative bacteria.

OBJECTIVE To evaluate the pharmacokinetics and pharmacodynamics of naloxone hydrochloride in dogs following intranasal (IN) and IV administration. ANIMALS 6 healthy adult mixed-breed dogs. PROCEDURES In a blinded crossover design involving 2 experimental periods separated by a washout period (minimum of 7 days), dogs were randomly assigned to receive naloxone IN (4 mg via a commercially available fixed-dose naloxone atomizer; mean ± SD dose, 0.17 ± 0.02 mg/kg) or IV (0.04 mg/kg) in the first period and then the opposite treatment in the second period. Plasma naloxone concentrations, dog behavior, heart rate, and respiratory rate were evaluated for 24 hours/period. RESULTS Naloxone administered IN was well absorbed after a short lag time (mean ± SD, 2.3 ± 1.4 minutes). Mean maximum plasma concentration following IN and IV administration was 9.3 ± 2.5 ng/mL and 18.8 ± 3.9 ng/mL, respectively. Mean time to maximum concentration following IN administration was 22.5 ± 8.2 minutes. Mean terminal half-life after IN and IV administration was 47.4 ± 6.7 minutes and 37.0 ± 6.7 minutes, respectively. Mean bioavailability of naloxone administered IN was 32 ± 13%. There were no notable changes in dog behavior, heart rate, or respiratory rate following naloxone administration by either route. CONCLUSIONS AND CLINICAL RELEVANCE Use of a naloxone atomizer for IN naloxone administration in dogs may represent an effective alternative to IV administration in emergency situations involving opioid exposure. Future studies are needed to evaluate the efficacy of IN naloxone administration in dogs with opioid intoxication, including a determination of effective doses.

OBJECTIVE To evaluate the lipidomic profile of surfactant obtained from horses with asthma at various clinical stages and to compare results with findings for healthy horses exposed to the same conditions. SAMPLE Surfactant samples obtained from 6 horses with severe asthma and 7 healthy horses. PROCEDURES Clinical evaluation of horses and surfactant analysis were performed. Samples obtained from horses with severe asthma and healthy horses before (baseline), during, and after exposure to hay were analyzed. Crude surfactant pellets were dried prior to dissolution in a solution of isopropanol:methanol:chloroform (4:2:1) containing 7.5mM ammonium acetate. Shotgun lipidomics were performed by use of high-resolution data acquisition on an ion-trap mass spectrometer. Findings were analyzed by use of an ANOVA with a Tukey-Kramer post hoc test. RESULTS Results of lipidomic analysis were evaluated to detect significant differences between groups of horses and among exposure statuses within groups of horses. Significantly increased amounts of cyclic phosphatidic acid (cPA) and diacylglycerol (DAG) were detected in surfactant from severely asthmatic horses during exposure to hay, compared with baseline and postexposure concentrations. Concentrations of cPA and DAG did not change significantly in healthy horses regardless of exposure status. CONCLUSIONS AND CLINICAL RELEVANCE cPA 16:0 and DAG 36:2 were 2 novel lipid mediators identified in surfactant obtained from asthmatic horses with clinical disease. These molecules were likely biomarkers of sustained inflammation. Further studies are needed to evaluate a possible correlation with disease severity and potential alterations in the plasma lipidomic profile of horses with asthma.