High-speed cinematography was used to record the movements of 12 cutting horses performing a standard test with a mechanical flag. Based on their previous competitive performances, horses were classified into 2 groups: group 1, composed of 5 moderately successful or average performers that had won less than $35,000 in purse money; and group 2, composed of 7 highly successful or elite performers that had amassed greater than $35,000 in competition earnings. Analysis of the results indicated that, compared with horses of the average group, the elite horses had faster reaction times in response to the start and cessation of flag movement (P less than 0.01), and were positioned closer to the flag during all stages of the trial (P less than 0.05). Discriminant analysis was used to construct a mathematical formula that could be used to classify an individual horse into 1 of the 2 alternative groups, based on the set of measurements. Two predictor variables were selected that described the maximal distance between the horse and the flag during the run and the part of the body that was moved first in response to the initial flag movement. The accuracy of the predicted group membership, compared with the actual group membership, was 100%.

A D-xylose absorption test was conducted on 4 healthy mares deprived of food for 12, 36, 72, and 96 hours before the test, with a 13- to 15-day adjustment period between each test. Maximal plasma concentrations after 72 and 96 hours of food deprivation were approximately 36% lower than those obtained after the 12- and 36-hour periods (P = 0.0001). Absorption curves were flatter and the decrease in plasma concentration was slower after the 72- and 96-hour periods of food deprivation. The rate of D-xylose absorption (P = 0.0108) and the initial rate of urinary excretion (P = 0.0117) were slower at 72 and 96 hours. Gastric emptying appeared to be progressively delayed with food deprivation, as evident by the delay in peak D-xylose excretion in urine (P = 0.0268). Areas under the plasma concentration-time curves and quantitites of D-xylose excreted in urine were similar for all periods of food deprivation, evidence that the same amounts of D-xylose were absorbed, despite changes in the plasma curve. A 15-hour collection period was sufficient to recover all D-xylose excreted in the urine, and during all periods 9.8 +/- 0.6% (mean +/- SEM) of the oral dose was eliminated in the urine.

The effects of single IV administered doses of dexamethasone on response to the adrenocorticotropic hormone (ACTH) stimulation test (baseline plasma ACTH, pre-ACTH cortisol, and post-ACTH cortisol concentrations) performed 1, 2, and 3 days (experiment 1) or 3, 7, 10, and 14 days (experiment 2) after dexamethasone treatment were evaluated in healthy Beagels. In experiment 1, ACTH stimulation tests were carried out after administration of 0, 0.01, 0.1, 1, and 5 mg of dexamethasone/kg of body weight. Dosage greater than or equal to 0.1 mg of dexamethasone/kg decreased pre-ACTH plasma cortisol concentration on subsequent days whereas dosages greater than or equal to 1 mg/kg also decreased plasma ACTH concentration. Treatment with 1 or 5 mg of dexamethasone/kg suppressed (P less than 0.05) post-ACTH plasma cortisol concentration (on day 3 after 1 mg of dexamethasone/kg; on days 1, 2, and 3 after 5 mg of dexamethasone/kg). In experiment 2, IV administration of 1 mg of dexamethasone/kg was associated only with low (P less than 0.05) post-ACTH plasma cortisol concentration in dogs on day 3. In experiment 2, pre-ACTH plasma cortisol and ACTH concentrations in dogs on days 3, 7, 10, and 14 and post-ACTH plasma cortisol concentration on days 7, 10, and 14 were not affected by dexamethasone administration. The results suggest that, in dogs a single IV administration. The results suggest that, in dogs, a single IV administered dosage of greater than or equal to 0.1 mg of dexamethasone/kg can alter the results of the ACTH stimulation test for at least 3 days. The suppressive effect of dexamethasone is dose dependent and is not apparent 7 days after treatment with 1 mg of dexamethasone/kg. The magnitude of the decrease in post-ACTH plasma cortisol concentration did not exceed 35% (compared with control values), regardless of the dose of dexamethasone used.