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in American Journal of Veterinary Research

Abstract

Objective—To determine whether a full-body spandex garment would alter rectal temperatures of healthy dogs at rest in cool and warm environments.

Design—Prospective study.

Animals—10 healthy dogs.

Procedures—Each dog was evaluated at a low (20° to 25°C [68° to 77°F]) or high (30° to 35°C [86° to 95°F]) ambient temperature while wearing or not wearing a commercially available whole-body spandex garment designed for dogs. Oxygen consumption was measured by placing dogs in a flow-through indirect calorimeter for 90 to 120 minutes. Rectal temperature was measured before dogs were placed in the calorimeter and after they were removed.

Results—Rectal temperature increased significantly more at the higher ambient temperature than at the lower temperature and when dogs were not wearing the garment than when they were wearing it. The specific rate of oxygen consumption was significantly higher at the lower ambient temperature than at the higher temperature.

Conclusions and Clinical Relevance—Results suggest that wearing a snug spandex body garment does not increase the possibility that dogs will overheat while in moderate ambient temperatures. Instead, wearing such a garment may enable dogs to better maintain body temperature during moderate heat loading. These results suggest that such garments might be used for purposes such as wound or suture protection without causing dogs to overheat. (J Am Vet Med Assoc 2004;224:71–74)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To develop a protocol to induce and maintain gastric ulceration in horses and to determine whether gastric ulceration affects physiologic indices of performance during high-speed treadmill exercise.

Animals—20 healthy Thoroughbreds.

Procedures—Each horse was acclimatized to treadmill exercise during a 2-week period. Subsequently, baseline data were collected (day 0) and each horse began an incrementally increasing exercise training program (days 1 through 56). Beginning on day 14, horses were administered omeprazole (4 mg/kg, PO, q 24 h until day 56) or no drug (10 horses/group) and underwent alternating 24-hour periods of feeding and feed withholding for 10 days to induce gastric ulceration. Extent of gastric ulceration was assessed weekly thereafter via gastroscopy. Physiologic indices of performance were measured at days 0 and 56. Gastric ulceration and exercise performance indices were compared within and between groups.

Results—In untreated horses, gastric ulcers were induced and maintained through day 56. Gastric ulcer formation was prevented in omeprazole-treated horses. There were significant interactions between time (pre- and post-training data) and treatment (nonulcer and ulcer groups) for mass-specific maximal O2 consumption ( O 2max/Mb) and mass-specific maximal CO2 production ( CO 2max/Mb). Post hoc analysis revealed a difference between groups for O 2max/Mb at day 56. Within-group differences for O 2max/Mb and CO 2max/Mb were detected for omeprazole-treated horses, but not for the horses with ulcers.

Conclusions and Clinical Relevance—In horses, gastric ulcers were induced and maintained by use of alternating periods of feeding and feed withholding in association with treadmill exercise (simulated racetrack training). Gastric ulcers adversely affected physiologic indices of performance in horses.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the influence of transportation by road and air on heart rate (HR) and HR variability (HRV) in horses.

Animals—6 healthy horses.

Procedures—ECG recordings were obtained from horses before (quarantine with stall rest [Q]; 24 hours) and during a journey that included transportation by road (RT; 4.5 hours), waiting on the ground in an air stall (W; 5.5 hours), and transportation by air (AT; 11 hours); HR was determined, and HRV indices of autonomic nervous activity (low-frequency [LF; 0.01 to 0.07 Hz] and high-frequency [HF; 0.07 to 0.6 Hz] power) were calculated.

Results—Mean ± SD HRs during Q, RT, W, and AT were 38.9 ± 1.5 beats/min, 41.7 ± 5.6 beats/min, 41.5 ± 4.3 beats/min, and 48.8 ± 5.6 beats/min, respectively; HR during AT was significantly higher than HR during Q. The LF power was significantly higher during Q (3,454 ± 1,087 milliseconds2) and AT (3,101 ± 567 milliseconds2) than it was during RT (1,824 ± 432 milliseconds2) and W (2,072 ± 616 milliseconds2). During Q, RT, W, and AT, neither HF powers (range, 509 to 927 milliseconds2) nor LF:HF ratios (range, 4.1 to 6.2) differed significantly. The HR during RT was highly correlated with LF power (R2 = 0.979), and HR during AT was moderately correlated with the LF:HF ratio (R2 = 0.477).

Conclusions and Clinical Relevance—In horses, HR and HRV indices during RT and AT differed, suggesting that exposure to different stressors results in different autonomic nervous influences on HR.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the frequency of epistaxis during or after racing among racehorses and identify factors associated with development of epistaxis.

Design—Retrospective study.

Sample Population—247,564 Thoroughbred and 4,045 Anglo-Arab race starts.

Procedure—Race start information (breed, age, sex, racing distance, and race type) was obtained for Thoroughbred and Anglo-Arab horses racing in Japan Racing Association-sanctioned races between 1992 and 1997. All horses that raced were examined by a veterinarian within 30 minutes of the conclusion of the race; any horse that had blood at the nostrils was examined with an endoscope. If blood was observed in the trachea, epistaxis related to exercise-induced pulmonary hemorrhage (EIPH) was diagnosed.

Results—Epistaxis related to EIPH was identified following 369 race starts (0.15%). Frequency of EIPHrelated epistaxis was significantly associated with race type, age, distance, and sex. Epistaxis was more common following steeplechase races than following flat races, in older horses than in horses that were 2 years old, following races ≤ 1,600 m long than following races between 1,601 and 2,000 m long, and in females than in sexually intact males. For horses that had an episode of epistaxis, the recurrence rate was 4.64%.

Conclusions and Clinical Relevance—Results suggested that frequency of EIPH-related epistaxis in racehorses is associated with the horse's age and sex, the type of race, and the distance raced. The higher frequency in shorter races suggests that higher intensity exercise of shorter duration may increase the probability of EIPH. (J Am Vet Med Assoc 2001;218:1462–1464)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the effects of body position on lung and air-sac volumes in anesthetized and spontaneously breathing red-tailed hawks (Buteo jamaicensis).

Animals—6 adult red-tailed hawks (sex unknown).

Procedures—A crossover study design was used for quantitative estimation of lung and air-sac volumes in anesthetized hawks in 3 body positions: dorsal, right lateral, and sternal recumbency. Lung volume, lung density, and air-sac volume were calculated from helical computed tomographic (CT) images by use of software designed for volumetric analysis of CT data. Effects of body position were compared by use of repeated-measures ANOVA and a paired Student t test.

Results—Results for all pairs of body positions were significantly different from each other. Mean ± SD lung density was lowest when hawks were in sternal recumbency (–677 ± 28 CT units), followed by right lateral (–647 ± 23 CT units) and dorsal (–630 ± 19 CT units) recumbency. Mean lung volume was largest in sternal recumbency (28.6 ± 1.5 mL), followed by right lateral (27.6 ± 1.7 mL) and dorsal (27.0 ± 1.5 mL) recumbency. Mean partial air-sac volume was largest in sternal recumbency (27.0 ± 19.3 mL), followed by right lateral (21.9 ± 16.1 mL) and dorsal (19.3 ± 16.9 mL) recumbency.

Conclusions and Clinical Relevance—In anesthetized red-tailed hawks, positioning in sternal recumbency resulted in the greatest lung and air-sac volumes and lowest lung density, compared with positioning in right lateral and dorsal recumbency. Additional studies are necessary to determine the physiologic effects of body position on the avian respiratory system.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To determine cardiorespiratory responses of Thoroughbreds to uphill and downhill locomotion on a treadmill at identical gradients.

ANIMALS 5 highly trained Thoroughbred geldings.

PROCEDURES Thoroughbreds were exercised for 2-minute intervals on a treadmill at 1.7, 3.5, 6.0, 8.0, and 10.0 m/s at a 4% incline, 0% incline (horizontal plane), and 4% decline in random order on different days. Stride frequency, stride length, and cardiopulmonary and O2-transport variables were measured and analyzed by means of repeated-measures ANOVA and Holm-Šidák pairwise comparisons.

RESULTS Horses completed all treadmill exercises with identical stride frequency and stride length. At identical uphill speeds, they had higher (vs horizontal) mass-specific O2 consumption (mean increase, 49%) and CO2 production (mean increase, 47%), cardiac output (mean increase, 21%), heart rate (mean increase, 11%), and Paco 2 (mean increase, 1.7 mm Hg), and lower Pao 2 (mean decrease, 5.8 mm Hg) and arterial O2 saturation (mean decrease, 1.0%); tidal volume was not higher. Downhill locomotion (vs horizontal) reduced mass-specific O2 consumption (mean decrease, 24%), CO2 production (mean decrease, 23%), and cardiac output (mean decrease, 9%). Absolute energy cost during uphill locomotion increased linearly with speed at approximately twice the rate at which it decreased during downhill locomotion.

CONCLUSIONS AND CLINICAL RELEVANCE Findings suggested that for Thoroughbreds, downhill locomotion resulted in a lower energy cost than did horizontal or uphill locomotion and that this cost changed with speed. Whether eccentric training induces skeletal muscle changes in horses similar to those in humans remains to be determined.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine prevalence of atrial fibrillation (AF) immediately after racing among racehorses that finished well behind the winners and examine potential risk factors for AF in these horses.

Design—Case-control study.

Animals—39,302 racehorses representing 404,090 race starts in races sanctioned by the Japan Racing Association between 1988 and 1997.

Procedure—Horses that finished ≥ 4 (turf races) or 5 (dirt races) seconds behind the winner or that did not complete the race were examined for AF within 5 minutes after the race. Logistic regression and χ 2 analyses were used to determine whether sex, age, race distance, race surface, year, or development of epistaxis was associated with development of AF.

Results—Estimated minimum frequency of AF was 0.03% (123 instances of AF following 404,090 race starts), and estimated minimum prevalence of AF among racehorses was 0.29% (115 horses with AF among 39,302 racehorses). Estimated frequency of AF among horses that finished slowly or did not finish was 1.39% (120 instances of AF among 8,639 examinations), and estimated prevalence of AF in horses that finished slowly was 1.23% (92 instances of AF among 7,500 horses) or 1.01% when only the first time a horse finished slowly was considered (76 instances of AF among 7,500 horses). Atrial fibrillation was paroxysmal in most horses. Among horses that finished slowly, 4-year-old and older horses and horses that raced on turf were more likely to develop AF.

Conclusions and Clinical Relevance—Results suggest that the likelihood of AF among racehorses that finish slowly is related to age and racing surface. (J Am Vet Med Assoc 2003;223:84–88)

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine whether warm-up exercise at different intensities alters kinetics and total contribution of aerobic power to total metabolic power in subsequent supramaximal exercise in horses.

Animals—11 horses.

Procedures—Horses ran at a sprint until fatigued at 115% of maximal oxygen consumption rate ( O 2max), beginning at 10 minutes following each of 3 warm-up protocols: no warmup (NoWU), 1 minute at 70% O 2max (moderate-intensity warm-up [MoWU]), or 1 minute at 115% O 2max (high-intensity warm-up [HiWU]). Cardiopulmonary and blood gas variables were measured during exercise.

Results—The O 2 was significantly higher in HiWU and MoWU than in NoWU throughout the sprint exercise period. Blood lactate accumulation rate in the first 60 seconds was significantly lower in MoWU and HiWU than in NoWU. Specific cardiac output after 60 seconds of sprint exercise was not significantly different among the 3 protocols; however, the arterial mixed-venous oxygen concentration difference was significantly higher in HiWU than in NoWU primarily because of decreased mixed-venous saturation and tension. Run time to fatigue following MoWU was significantly greater than that with NoWU, and there was no difference in time to fatigue between MoWU and HiWU.

Conclusions and Clinical Relevance—HiWU and MoWU increased peak values for O 2 and decreased blood lactate accumulation rate during the first minute of intense exercise, suggesting a greater use of aerobic than net anaerobic power during this period.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether withholding of food affects autonomic nervous system balance by analysis of heart rate (HR), HR variability (HRV), and frequency of second-degree atrioventricular block in horses.

Animals—5 healthy Thoroughbreds.

Procedures—For two 24-hour periods in a crossover study, food was withheld from horses or horses were maintained on their regular feeding schedule (control conditions) in their stalls and Holter monitor ECG recordings were obtained. The ECGs were analyzed by use of fast-Fourier transformation, and power spectrum densities were calculated for low-frequency (0.01 to 0.07 Hz) and high-frequency (0.07 to 0.6 Hz) variations in HR. Serum cortisol and plasma ACTH, norepinephrine, and glucose concentrations were measured at predetermined time points.

Results—Withholding of food resulted in significantly lower HR and more frequent second-degree atrioventricular block (the frequency of which was inversely related to the HR), compared with findings for control conditions. Circadian rhythms were similar during food-withholding and control conditions; peak HR was detected from 7:00 pm to 8:00 pm, and the lowest HR was detected in the early morning. During food-withholding conditions, the low-frequency and high-frequency components of HRV were significantly higher, and the low-frequency-to-high-frequency ratio was lower than during control conditions. Serum cortisol concentration was higher and plasma glucose concentration was lower at 6:00 pm in horses when food was withheld, compared with findings during control conditions.

Conclusions and Clinical Relevance—Indices of HRV seemed to be sensitive to changes in autonomic nervous activity and may be useful as clinical indices of the neuroendocrine response to stressors in horses.

Full access
in American Journal of Veterinary Research