Microbiologic findings in feedlot cattle with acute interstitial pneumonia.

OBJECTIVE: To test the hypothesis that feedlot cattle with acute interstitial pneumonia (AIP) have bacterial infection of the lung or liver and concurrent bovine respiratory syncytial virus (BRSV) infection significantly more often than pen mates without AIP ANIMALS: 39 feedlot cattle with signs consistent with AIP and no history of treatment with antimicrobials and 32 healthy control cattle from the same pens. PROCEDURES: Lung and liver specimens were obtained postmortem for bacterial or mycoplasmal culture and histologic examination; lung tissue was assessed for BRSV infection immunohistochemically. RESULTS: Among affected cattle, 26 had AIP confirmed histologically. Lung tissue from 11 cattle with AIP yielded microbial respiratory tract pathogens on culture; tissues from control animals yielded no microbial growth. In 4 cattle with AIP and 2 control animals, liver abscesses were detected; bacteria were isolated from abscessed tissue in 3 and 1 of those animals, respectively. Immunohistochemically, 9 cattle with AIP and no control animals were BRSV-positive. Histologically, 9 AIP-affected cattle had only acute alveolar damage with exudation, and the other 17 had acute exudation with type II pneumocyte hyperplasia. No lesions of AIP were detected in control animals. Only 4 AIP-affected cattle had bacterial infection of the lung with concurrent BRSV infection. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that microbial respiratory tract pathogens are more common in cattle with AIP than in healthy pen mates. Control of bacterial pneumonia late in the feeding period may reduce the incidence of AIP at feedlots where AIP is a problem.

Effects of florfenicol injection on the meat characteristics of the cervical muscles in cattle.

OBJECTIVE: To determine the effects of florfenicol injection on the meat characteristics of the cervical muscles in cattle. ANIMALS: 100 steers (mean weight, 380 kg). PROCEDURE: In 50 calves, florfenicol (25 ml, twice) was injected into the cervical muscles of 1 side of the neck, and saline (0.9% NaCI) solution (25 ml, twice) was injected into the cervical muscles of the other side of the neck. In the remaining 50 calves, florfenicol was injected into the cervical muscles of 1 side of the neck, and nothing was injected into the cervical muscles of the other side of the neck. Animals were slaughtered 132 days later, and samples of the cervical muscles were submitted for histologic evaluation and measurement of shear forces. RESULTS: 2 injection sites used in the present study had extensive lesions, and both of these were sites where florfenicol had been injected. However, histologic scores for the florfenicol injection sites were not significantly different from scores for the contralateral saline solution injection sites and uninjected control sites. In addition, shear force values were not significantly different between sites in which florfenicol had been injected and the contralateral sites. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that few reactions should be expected with injection of florfenicol into the cervical muscles in steers and that reactions that do occur will consist mainly of fibrosis and infiltration of adipose tissue. However, shear force values, a measure of tenderness of the meat, should not be affected.