Bovine respiratory disease (BRD) remains one of the most common and costly health challenges in preweaned dairy calves. While traditional diagnosis relies on visual symptoms, such as coughing, nasal discharge, or elevated temperature, these signs often appear late in the disease process, after damage has already occurred. Even when calves appear healthy, subclinical lung infections — or non-visible forms of pneumonia — can compromise growth, feed efficiency, and future milk production. Learn more about this topic here.