- Bovine respiratory disease complex (BRD) is an infection of both the upper and lower respiratory tract and includes components of rhinitis, otitis, tracheitis, and pneumonia. Bovine respiratory disease (BRD) is one of the most common causes of morbidity and mortality of calves in the United States and world-wide. Besides the financial and animal losses, BRD has negative implications for animal welfare. Clinical diagnosis of pulmonary disease in calves with BRD is challenging as clinical respiratory scoring systems, thoracic auscultation, and bronchoalveolar lavage are only moderately sensitive and specific for pulmonary disease detection. Thus, alternative diagnostic testing methods (i.e., thoracic radiography, ultrasonography, and computed tomography) are needed for early detection and treatment of BRD.Thoracic radiography is the most commonly utilized technique to evaluate the thorax for the presence of pulmonary disease. However, in large animal patients including calves, pulmonary ultrasound is currently more frequently performed due to its ease of use, real time imaging, ability to monitor disease, and availability in field conditions. In human patients, computed tomography (CT) is considered either the gold standard or method of choice to evaluate for pulmonary disease. This is likely similar in veterinary patients but has not been established yet.In the first study, the objective was to evaluate if thoracic radiography provides accurate information about the severity and extent of lung disease compared to CT in calves with naturally occurring respiratory disease. The goal of the study was to assess if thoracic radiography could be used as a potential on-farm diagnostic tool for pulmonary disease detection in calves with naturally occurring respiratory disease. As CT is considered the method of choice to for detecting pulmonary disease, it was used as a reference standard. Additionally, we were interested if current clinical respiratory scoring techniques allow for detection of pulmonary disease in acute and chronic pulmonary diseased calves to a similar degree as thoracic computed radiography (CR) and CT.First, a CT protocol was established utilizing an intravenously injected sedation protocol using xylazine, butorphanol, and ketamine. The feasibility and safety of performing contrast-enhanced thoracic multidetector computed tomography (CT) examinations in sedated calves was evaluated. Finally, radiographic pulmonary disease detection rates were compared with those of thoracic CR and the Wisconsin respiratory scoring system.Lateral thoracic CR was performed on fifteen awake, standing Jersey calves with acute or chronic respiratory disease as diagnosed on-farm with the Wisconsin respiratory scoring system. Once calves were sedate, thoracic CT was performed pre- and post- intravenous iodinated contrast medium administration using a 64-multidetector CT.We observed that thoracic CT was superior to CR for pneumonia detection in acute and chronic respiratory diseased calves due to the lack of summation in all areas of the lungs. However, a diagnosis of pneumonia was made with equal rate on both thoracic CR and CT. The intravenous sedation protocol enabled acquisition of CT images of diagnostic quality, without the need for re-scanning. Although mild differences in classification of lung pattern and extent of lung disease were seen when comparing an experienced and a less experienced evaluator, the overall differences were not statistically significant. The best intra- and inter-observer agreement was noted when evaluating the cranioventral aspects of the lungs in either modality. Wisconsin Calf Respiratory Scoring was not able to diagnose chronic pneumonia in calves.Lung ultrasonography (US) has been used to diagnose and monitor pulmonary disease in large animal veterinary species as well as in humans. In the second study, the objective was to evaluate US as a potential on-farm diagnostic tool for pulmonary disease detection in calves. To accomplish our objective, US lung lesion detection rates of 16 Jersey calves with and 6 Jersey calves without clinical sigs of respiratory disease were compared to those with digital radiography (DR), CT, histopathology, and Wisconsin Calf Respiratory Scoring. In the second study, we observed that lung US was successfully performed in all calves without sedation and in standing position. Clinically healthy calves with low respiratory scores (<2) were diagnosed with pulmonary parenchymal changes on all imaging modalities and histopathologically, but the observed changes were smaller and less severe than in calves with clinical respiratory disease. Accurate assessments of severity and distribution of pneumonia, and differentiation of lung pattern types could bemade with US and correlated well with DR, CT and histopathology. Pulmonary US is an easy to perform, feasible and accurate technique diagnosing pulmonary disease in calves and allows differentiation between clinically healthy and respiratory diseased calves. However, US does not allow identification of intraparenchymal bullae or abscesses.In this study, thoracic DR, pulmonary US, and thoracic CT performed similarly well for pneumonia detection by each evaluator, and a more experienced evaluator had a better overall sensitivity for pneumonia detection with all imaging modalities. This supports the use of US as a potential diagnostic tool for pneumonia detection in calves.