Experimental design. Timeline representing the experimental design from arrival of animals to the Research Centre facilities (d 0) until weaning (d 52 (SD; 10.4) post-arrival). Research veterinarian performed TUS and CRS on days 0, 7 and 14. Moreover, an extra TUS was performed in 33 out of 53 calves between day 14 and 30. Farm technician checked for visual clinical signs twice daily during all study period. Calves with CRS ≥ 5 and/or RT > 39.6 ºC were treated and classified as cBRD+. Animals not receiving treatment during all study period were classified as cBRD-. BRD, bovine respiratory disease; cBRD, clinical BRD; CRS, clinical respiratory score; RT, rectal temperature; TUS, thoracic ultrasonography; TUSS, thoracic ultrasonography score.