Bovine respiratory disease (BRD) is the most common and costly disease affecting beef cattle in the world. It is a complex, bacterial infection that causes pneumonia in calves which can be fatal. The infection is usually a sum of three codependent factors: stress, an underlying viral infection, and a new bacterial infection. The diagnosis of the disease is complex since there are multiple possible causes. The disease manifests itself most often in calves within four weeks of weaning, when calves are sorted and often sold to different farms; a common nickname for BRD is "shipping fever. It is not known whether the stress itself, co-mingling, or travel conditions are at most to blame, and while studies have identified general stressing factors like transport and cold weather conditions, there is still no conclusive evidence on more specific factors (e.g. distance, transport mode, temperature, or temperature volatility).