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- Author or Editor: Garold S. Yost x
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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 evaluate viral and bacterial respiratory pathogens and Mycoplasma spp isolated from lung tissues of cattle with acute interstitial pneumonia (AIP) and cattle that had died as a result of other causes.
Sample Population—186 samples of lung tissues collected from cattle housed in 14 feedlots in the western United States.
Procedure—Lung tissues were collected during routine postmortem examination and submitted for histologic, microbiologic, and toxicologic examinations. Histologic diagnoses were categorized for AIP, bronchopneumonia (BP), control samples (no evidence of disease), and other disorders.
Results—Cattle affected with AIP had been in feedlots for a mean of 127.2 days before death, which was longer than cattle with BP and control cattle. Detection of a viral respiratory pathogen (eg, bovine respiratory syncytial virus [BRSV], bovine viral diarrhea virus, bovine herpesvirus 1, or parainfluenza virus 3) was not associated with histologic category of lung tissues. Bovine respiratory syncytial virus was detected in 8.3% of AIP samples and 24.0% of control samples. Histologic category was associated with isolation of an aerobic bacterial agent and Mycoplasma spp. Cattle with BP were at greatest risk for isolation of an aerobic bacterial agent and Mycoplasma spp.
Conclusion and Clinical Relevance—Analysis of these results suggests that AIP in feedlot cattle is not a consequence of infection with BRSV. The increased risk of isolation of an aerobic bacterial agent from cattle with AIP, compared with control cattle, may indicate a causal role or an opportunistic infection that follows development of AIP. (Am J Vet Res 2001; 62:1519–1524)
Objective—To compare concentrations of 3-methyleneindolenine (3MEIN) in lung tissues obtained from feedlot cattle that died as a result of acute interstitial pneumonia (AIP) and cattle that died as a result of other causes and to compare blood concentrations of 3MEIN in healthy feedlot cattle and feedlot cattle with AIP.
Study Population—Blood samples and lung tissues collected from 186 cattle housed in 14 feedlots in the western United States.
Procedure—Samples of lung tissues were collected during routine postmortem examination and submitted for histologic, microbiologic, and toxicologic examination. Blood samples were collected from cattle with clinical manifestations of AIP and healthy penmates. Histologic diagnoses were categorized as AIP, bronchopneumonia (BP), control samples, and other disorders. Concentrations of 3MEIN were determined in lung tissues and blood samples, using an ELISA.
Results—Concentrations of 3MEIN in lung tissues were significantly greater in AIP and BP samples, compared with control samples. Absorbance per microgram of protein did not differ between BP and AIP samples. Blood concentrations of 3MEIN were significantly greater in cattle with AIP, compared with healthy cattle or cattle with BP. Odds of an animal with AIP being a heifer was 3.1 times greater than the odds of that animal being a steer.
Conclusion and Clinical Relevance—Increased pulmonary production of 3MEIN may be an important etiologic factor in feedlot-associated AIP. (Am J Vet Res 2001;62:1525–1530)