Comparison of Thoracic Auscultation, Clinical Score, and Ultrasonography as Indicators of Bovine Respiratory Disease in Preweaned Dairy Calves

Background The diagnostic tools for bovine respiratory disease diagnosis include clinical inspection, thoracic auscultation, and ultrasonography. Hypothesis Thoracic auscultation and clinical examination have limitations in the detection of lung consolidation in dairy calves. Animals Prospective cohort of 106 preweaned calves from 13 different dairy herds (10 with a history of active bovine respiratory disease ( BRD ) in calves and 3 without suspected BRD problems). Methods Each preweaned calf was clinically inspected using the Wisconsin calf respiratory scoring chart ( CRSC ) and treatment history was noted. Systematic thoracic auscultation and ultrasonography then were performed, the latter focusing on lung consolidation. Mortality was recorded over a 30‐day period. Results A total of 56 of 106 calves had ultrasonographic evidence of lung consolidation. The sensitivity of thoracic auscultation to detect consolidation was 5.9% (range, 0–16.7%). Only 41.1% (23/33) of calves with consolidated lungs had been treated previously by the producers. When adding CRSC and previous BRD treatment by the producer, sensitivity of detection increased to 71.4% (40/56). The area under the receiver operating characteristics curve was 0.809 (95% CI , 0.721–0.879) for the number of areas within the lungs with consolidation and 0.743 (95% CI , 0.648–0.823) for the maximal depth of consolidation as predictors of death within 1 month after examination. These were not significantly different ( P  = .06). Conclusions and Clinical Importance This study shows that thoracic auscultation is of limited value in diagnosing lung consolidation in calves. Ultrasonographic assessment of the thorax could be a useful tool to assess BRD detection efficiency on dairy farms.