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Objective—To describe time-dependent changes in plasma concentrations of 3-methylindole (3MI) and blood concentrations of 3-methyleneindolenine (3MEIN)-adduct in feedlot cattle.
Animals—64 yearling steers.
Procedures—Steers were assigned to 2 groups (32 steers/group). During the first 8 weeks, blood samples were collected from group 1 before the morning ration was fed, whereas samples from group 2 were collected 2 to 3 hours after the ration was fed. Blood samples were collected from all steers approximately 4 times/wk for 3 weeks and 3 times/wk for the subsequent 5 weeks. Samples were collected at the same time for all steers for an additional 10 weeks. Plasma samples were analyzed for 3MI concentrations. Blood samples collected from cattle in group 2 during the first 8 weeks were analyzed for 3MEINadduct concentrations.
Results—Mean blood concentration of 3MEINadduct increased to a maximum value on day 33 (0.80 U/μg of protein) and then decreased to a minimum on day 54 0.40 U/μg of protein). Plasma 3MI concentrations initially decreased and remained low until after day 54. Group-1 cattle had lower plasma 3MI concentrations, compared with concentrations for group-2 cattle. Blood 3MEIN-adduct concentrations and plasma 3MI concentrations were not associated with deleterious effects on weight gains.
Conclusions and Clinical Relevance—Blood 3MEIN-adduct concentrations peaked during the period of greatest risk for development of bovine respiratory disease complex. Conversely, plasma 3MI concentrations decreased during the same period. Animal-to-animal variation in metabolic capacity to convert 3MI to 3MEIN may be of more importance than differences in plasma 3MI concentration. Am J Vet Res (2002;63:591–597).
Objective—To evaluate the effect of feeding aspirin and supplemental vitamin E on growth performance, lung lesions, plasma concentrations of 3-methylindole (3MI), and 3-methyleneindolenine (3MEIN)-adduct concentrations in blood and pulmonary tissues of feedlot cattle.
Animals—256 crossbred steers; 64 cattle were used in experiment 1 and 192 cattle were used in experiment 2.
Procedures—A 2 × 2 factorial design was used for each experiment. Treatment factors were aspirin (0 or 3 g daily) and vitamin E (200 or 1,500 IU daily). Steers were housed in pens (8 steers/pen). Steers were slaughtered on days 59 and 138 for experiments 1 and 2, respectively. Lungs were grossly evaluated. Plasma 3MI concentration was determined, and 3MEIN-adduct concentrations were measured in blood and pulmonary tissues.
Results—Treatment was not associated with improvement or adverse effects on weight gain, drymatter intake, or feed efficiency in experiment 2. In experiment 1, 36 of 63 (57.1%) steers had lung lesions. Lesions were not associated with treatment or concentrations of 3MI and 3MEIN-adduct. Plasma 3MI concentration and concentrations of 3MEINadduct in blood and pulmonary tissues were 3.11 µg/mL, 0.51 U/µg of protein, and 0.49 U/µg of protein, respectively. Aspirin was associated with increased blood concentrations of 3MEIN-adduct for diets that did not contain supplemental vitamin E.
Conclusions and Clinical Relevance—Differences in performance of feedlot steers were not associated with treatment diet. It is possible that concurrent exposure of feedlot cattle to other factors typically associated with development of respiratory tract disease would affect these findings. (Am J Vet Res 2002:63:1641–1647)
Objective—To assess the reliability and accuracy of a predictive rectal thermometer, an infrared auricular thermometer designed for veterinary use, and a subcutaneous temperature-sensing microchip for measurement of core body temperature over various temperature conditions in dogs.
Animals—8 purpose-bred dogs.
Procedures—A minimum of 7 days prior to study commencement, a subcutaneous temperature-sensing microchip was implanted in 1 of 3 locations (interscapular, lateral aspect of shoulder, or sacral region) in each dog. For comparison with temperatures measured via rectal thermometer, infrared auricular thermometer, and microchip, core body temperature was measured via a thermistor-tipped pulmonary artery (TTPA) catheter. Hypothermia was induced during anesthesia at the time of TTPA catheter placement; on 3 occasions after placement of the catheter, hyperthermia was induced via administration of a low dose of endotoxin. Near-simultaneous duplicate temperature measurements were recorded from the TTPA catheter, the rectal thermometer, auricular thermometer, and subcutaneous microchips during hypothermia, euthermia, and hyperthermia. Reliability (variability) of temperature measurement for each device and agreement between each device measurement and core body temperature were assessed.
Results—Variability between duplicate near-simultaneous temperature measurements was greatest for the auricular thermometer and least for the TTPA catheter. Measurements obtained by use of the rectal thermometer were in closest agreement with core body temperature; for all other devices, temperature readings typically underestimated core body temperature.
Conclusions and Clinical Relevance—Among the 3 methods of temperature measurement, rectal thermometry provided the most accurate estimation of core body temperature in dogs.
Objective—To evaluate sensitivities at the herd level of test strategies used in the Voluntary Johne's Disease Herd Status Program (VJDHSP) and alternative test strategies for detecting dairy cattle herds infected with Mycobacterium paratuberculosis.
Design—Nonrandom cross-sectional study.
Sample Population—64 dairy herds from Pennsylvania, Minnesota, Colorado, Ohio, and Wisconsin. Fifty-six herds had at least 1 cow shedding M paratuberculosis in feces; the other 8 herds were free from paratuberculosis.
Procedure—For all adult cows in each herd, serum samples were tested for antibodies to M paratuberculosis with an ELISA, and fecal samples were submitted for bacterial culture for M paratuberculosis. Sensitivities at the herd level (probability of detecting infected herd) of various testing strategies were then evaluated.
Results—Sensitivity at the herd level of the testing strategy used in level 1 of the VJDHSP (use of the ELISA to test samples from 30 cows followed by confirmatory bacterial culture of feces from cows with positive ELISA result) ranged from 33 to 84% for infected herds, depending on percentage of cows in the herd with positive bacterial culture results. If follow- up bacterial culture was not used to confirm positive ELISA results, sensitivity ranged from 70 to 93%, but probability of identifying uninfected herds as infected was 89%.
Conclusions and Clinical Relevance—Results suggest that the testing strategy used in the VJDHSP will fail to identify as infected most dairy herds with a low prevalence of paratuberculosis. A higher percentage of infected herds was detected if follow-up bacterial culture was not used, but this test strategy was associated with a high probability of misclassifying uninfected herds. (J Am Vet Med Assoc 2002;220: 1053–1057)