Figure 1.

Definition of bovine respiratory disease (BRD) and control study groups used to examine the microbiological and histopathological findings in cases of fatal BRD of feedlot cattle in western Canada. The definition of the study groups are accompanied by a digital image of the open thoracic cavity and cross section of the lung of animals in the different groups.

UF — undifferentiated fever

Pneumonia was diagnosed when there was evidence for lung consolidation +/− atelectasis

Fibrinous peumonia was diagnosed when there was evidence for lung consolidation, edema, atelectasis, and fibrinous exudate, with or without associated fibrinous pleuritis

Lesions indicative of chronic pneumonia included pulmonary abscessation, adhesions, and/or shrinkage (presence of fibrous tissue)

Lesions indicative of acute pneumonia included pulmonary edema, swelling, or both

Bronchiolar pattern was diagnosed based on the presence of prominent and thickened bronchioles with or without exudate or debris in the lumen, which was detected on gross examination of the cross section of the lung