Bovine respiratory disease is the most economically significant and welfare-relevant disease in beef cattle, particularly in feedlots where stress and disease transmission combine to cause mass illness.
Cattle with respiratory disease suffer from fever, labored breathing, coughing, and the systemic effects of severe infection. The stress of transport to feedlots suppresses their immune systems at the same moment they are exposed to pathogens from commingled cattle from many origins. By the time illness is detected in group settings, disease may already be advanced. Chronic pneumonia leaves lung damage that causes ongoing respiratory compromise throughout the feeding period.