Bovine Respiratory Disease (BRD) is a complex disease process and early diagnosis can be difficult because of inconsistent or absent clinical signs. Many reports emphasize the negative implications of clinical BRD. Diagnosing subclinical respiratory disease through thoracic ultrasonography has the potential to improve animal welfare and productivity. The objective of this cohort study was to determine if lung consolidation in young dairy calves was associated with a decline in first lactation milk production. A total of 215 female calves from 3 dairy herds in Southwestern Ontario were enrolled and assessed weekly during their first 8 weeks of life for evidence of lung consolidation (CON) through the use of thoracic ultrasonography (US) (Ibex Pro, Loveland, CO). Consolidation was measured within the first 10 intercostal spaces on both sides of the thorax, using gridlines on the screen of the US. Calves were considered CON positive if 3cm or more of consolidated lung was present. A multivariable linear regression model was used to identify significant risk factors associated with first lactation 305 milk production. In the study population, the following calfhood conditions were detected: twins (4%; n = 8), diarrhea in the first 21 d of life (31%; n = 66), rib fractures (7%; n = 14), lung abscesses (3%; n = 6), and at least one diagnosis of CON (57%; n = 123). Overall, 7%(n = 15) of calves died, and 18%(n = 38) of animals were sold before the end of first lactation. For every one-month increase in age at first calving, milk production in first lactation increased by nearly 140 kg (P = 0.01). The presence of CON, at least once in the first 8 weeks of life, was associated with a 525kg decrease in first lactation 305 milk production (P = 0.027). These results indicate that lung consolidation during the first 56 d of life may have a possible long-term impact on dairy calves, manifested as reduced milk production during first lactation.