OBJECTIVE To compare the effects of 3 walkway cover types on temporospatial and ground reaction force measurements of dogs during gait analysis with a pressure-sensitive walkway (PSW). ANIMALS 35 client- and staff-owned dogs (25 nonlame and 10 lame). PROCEDURES In a crossover study design, all dogs were evaluated at a comfortable walk on a PSW to which 3 cover types (a 0.32-cm-thick corrugated vinyl mat or a 0.32- or 0.64-cm-thick polyvinyl chloride yoga mat) were applied in random order. Temporospatial and ground reaction force measurements were obtained and compared among cover types within the nonlame and lame dog groups. RESULTS Several variables, including maximum peak pressure, maximum force (absolute and normalized as a percentage of body weight), and vertical impulse (absolute and normalized) differed significantly in most comparisons among cover types for both nonlame and lame dogs. There was no significant difference in maximum force values between the 0.32-cm-thick corrugated vinyl and 0.64-cm-thick polyvinyl chloride cover types for both nonlame and lame dogs. CONCLUSIONS AND CLINICAL RELEVANCE To the authors’ knowledge, the cover type used during data collection with a PSW is rarely provided in published reports on this topic. The findings in this study suggested that to ensure that PSW data for dogs are collected in a standardized manner, the same cover type should be used during follow-up visits to evaluate clinical outcomes, for the duration of research studies, and at all locations for multi-institutional studies. The cover type should be specified in future PSW studies to allow direct comparisons of findings between studies.

OBJECTIVE To identify whether age, sex, or breed is associated with crown height of the left and right maxillary first molar tooth (M1) measured on CT images, to develop a mathematical model to determine age of horses by use of M1 crown height, and to determine the correlation between M1 crown height measured on radiographic and CT images. SAMPLE CT (n = 735) and radiographic images (35) of the heads of horses. PROCEDURES Crown height of left and right M1 was digitally measured on axial CT views. Height was measured on a lateral radiographic image when available. Linear regression analysis was used to identify factors associated with crown height. Half the data set was subsequently used to generate a regression model to predict age on the basis of M1 crown height, and the other half was used to validate accuracy of the predictions. RESULTS M1 crown height decreased with increasing age, but the rate of decrease slowed with increasing age. Height also differed by sex and breed. The model most accurately reflected age of horses < 10 years old, although age was overestimated by a mean of 0.1 years. The correlation between radiographic and CT crown height of M1 was 0.91; the mean for radiographic measurements was 2.5 mm greater than for CT measurements. CONCLUSIONS AND CLINICAL RELEVANCE M1 crown height can be used to predict age of horses. Results for CT images correlated well with those for radiographic images. Studies are needed to develop a comparable model with results for radiographic images.

OBJECTIVE To determine from MRI measurements whether soft palate length (SPL) and thickness are correlated in dogs, evaluate the association between the olfactory bulb angle (OBA) and degree of brachycephalia, and determine the correlation between soft palate–epiglottis overlap and OBA in dogs. ANIMALS 50 brachycephalic and 50 nonbrachycephalic client-owned dogs without abnormalities of the head. PROCEDURES Medical records and archived midsagittal T2-weighted MRI images of brachycephalic and nonbrachycephalic dogs' heads were reviewed. Group assignment was based on breed. Data collected included weight, SPL and thickness, OBA, and the distance between the caudal extremity of the soft palate and the basihyoid. Soft palate length and thickness were adjusted on the basis of body weight. RESULTS Brachycephalic dogs had significantly thicker soft palates and lower OBAs, compared with findings for nonbrachycephalic dogs. There was a significant negative correlation (r2 = 0.45) between OBA and soft palate thickness. The correlation between SPL and OBA was less profound (r2 = 0.09). The distance between the caudal extremity of the soft palate and the basihyoid was shorter in brachycephalic dogs than in nonbrachycephalic dogs. The percentage of epiglottis–soft palate overlap significantly decreased with increasing OBA (r2 = 0.31). CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that MRI images can be consistently used to assess anatomic landmarks for measurement of SPL and thickness, OBA, and soft palate-to-epiglottis distance in brachycephalic and nonbrachycephalic dogs. The percentage of epiglottis–soft palate overlap was significantly greater in brachycephalic dogs and was correlated to the degree of brachycephalia.

OBJECTIVE To determine the effects of acepromazine maleate premedication on cardiovascular function before and after infusion of dobutamine hydrochloride for 30 minutes in isoflurane-anesthetized horses. ANIMALS 6 healthy adult horses. PROCEDURES Each horse was anesthetized once following premedication with acepromazine (0.02 mg/kg, IV) administered 30 minutes prior to anesthetic induction (ACP+ treatment) and once without premedication (ACP– treatment). Anesthesia was induced with IV administration of xylazine hydrochloride (0.8 mg/kg), ketamine hydrochloride (2.2 mg/kg), and diazepam (0.08 mg/kg). Horses were positioned in right lateral recumbency, and anesthesia was maintained via inhalation of isoflurane delivered in oxygen. End-tidal isoflurane concentration was adjusted to achieve a target mean arterial blood pressure of 60 mm Hg (interquartile range [25th to 75th percentile], 57 to 63 mm Hg) for at least 15 minutes. Cardiac index, oxygen delivery index, and femoral arterial blood flow indices were determined 60 minutes after anesthetic induction (baseline). Dobutamine was then infused to achieve a target mean arterial blood pressure of 80 mm Hg (interquartile range, 76 to 80 mm Hg). Data collection was repeated 30 minutes after the start of dobutamine infusion for comparison with baseline values. RESULTS Complete data sets were available from 5 of the 6 horses. Dobutamine administration resulted in significant increases in oxygen delivery and femoral arterial blood flow indices but no significant change in cardiac index for each treatment. However, at baseline or 30 minutes after the start of dobutamine infusion, findings for the ACP+ and ACP– treatments did not differ. CONCLUSIONS AND CLINICAL RELEVANCE In isoflurane-anesthetized horses, dobutamine administration increased oxygen delivery and femoral arterial blood flow indices, but these changes were unaffected by premedication with acepromazine.

Objective-To compare the efficacy of gamithromycin with that of tulathromycin for control of undifferentiated bovine respiratory disease complex (BRDC) in feedlot calves. Animals-2,529 weaned crossbred beef calves. Procedures-At each of 2 feedlots, calves at risk of developing BRDC were administered a single dose of gamithromycin (6.0 mg/kg, SC; n = 1,263) or tulathromycin (2.5 mg/kg, SC; 1,266) metaphylactically. Health (BRDC morbidity, mortality, case-fatality, and retreatment rates) and performance (average daily gain, dry matter intake, and feed-to-gain ratio) outcomes were compared between treatments via classical hypothesis testing. Bioequivalence limits for gamithromycin and tulathromycin were established for outcomes for which no significant difference between treatments was detected. Results-Mean BRDC morbidity rate (31.0%) for calves administered gamithromycin was greater than that (22.9%) for calves administered tulathromycin; otherwise, health and performance did not differ between treatments. Limits for mean differences within which gamithromycin was considered bioequivalent to tulathromycin were +/- 10% for BRDC retreatment rate, +/- 3.5% for BRDC mortality rate, ± 16% for case-fatality rate, +/- 37 kg for final body weight, +/- 0.1 kg/d for average daily gain, +/- 0.3 kg/d for dry matter intake, and +/- 0.7 for feed-to-gain ratio. Conclusions and Clinical Relevance-The efficacy of gamithromycin did not differ from that of tulathromycin for all outcomes except morbidity rate; calves administered gamithromycin had a higher BRDC morbidity rate than did calves administered tulathromycin. On the basis of the bioequivalence limits established for this dataset, gamithromycin was considered equivalent to tulathromycin for the control of BRDC.

Objective-To evaluate the use of high-resolution manometry (HRM) in awake and sedated dogs and to assess potential effects of a standard sedation protocol. Animals-22 Beagles. Procedures-An HRM catheter with 36 pressure sensors was inserted intranasally in each dog. After an adaption period of 5 minutes, each set of measurements included 5 swallows of a liquid and 5 swallows of a solid bolus. Measurements were repeated 30 minutes after IM administration of buprenorphine and acepromazine. Results-HRM was successfully performed in 14 dogs. Data sets of 8 dogs were adequate for analysis. For the upper esophageal sphincter, median values of baseline pressure, residual pressure, relaxation time to nadir, and relaxation duration were determined for awake and sedated dogs for liquid and solid swallows. For the tubular portion of the esophagus, median values of peristaltic contractile integral, bolus transit time, and contractile front velocity were determined for awake and sedated dogs for liquid and solid swallows. For the lower esophageal sphincter, median values of baseline pressure and residual pressure were determined for awake and sedated dogs for liquid and solid swallows. Significant differences (awake vs sedated) were found for the upper esophageal sphincter residual pressure (liquid swallows), relaxation time to nadir (liquid swallows), bolus transit time (solid swallows), and contractile front velocity (solid swallows). Conclusions and Clinical Relevance-HRM was feasible for evaluation of esophageal function in most awake dogs. Although sedation in uncooperative patients may minimally influence results of some variables, an overall assessment of swallowing should be possible.

Loline and ergot alkaloids found in endophyte-infected (Acremonium coenophialum) tall fescue (EITF) cause vasoconstriction of equine vessels in vitro. An aggregate risk study was used to evaluate the association between horses exposed to EITF and development of laminitis. Veterinary teaching hospitals participating in the Veterinary Medical Data Base were grouped by whether equine accessions were likely to have been at high, moderate, or low risk for exposure to EITF. From 1980-1990, there were 185,781 accessions, of which 5,536 had diagnosis of laminitis. Proportion of equine accessions with laminitis reported by veterinary teaching hospitals for high, moderate, and low risks, were 3.41, 3.04, and 2.00 cases/100 accessions, respectively (P < 0.0001). Comparison of the proportion of accessions with laminitis in the high- and moderate-risk groups with that in the low-risk group revealed significant differences between risk groups over all months (P = 0.063) and differences from month to month within risk groups (P = 0.0001). If the difference among risk groups is attributed entirely to exposure to EITF, the population-attributable risk is 7 cases/1,000 admissions, or 15% of all admissions for laminitis at veterinary teaching hospitals in our data base. Preliminary data support an association between hoses exposed to EITF and increased risk of laminitis; however, studies at the individual animal level are indicated to confirm this hypothesis.