Bovine Respiratory Disease Complex

By Barry Whitworth

Bovine respiratory disease complex (BRDC) or syndrome (BRDS), commonly referred to as pneumonia or “shipping fever,” is a multifactorial disease primarily affecting young cattle. According to W. Mark Hilton, DVM with Elanco Animal Health, BRD is the number one disease of stocker, backgrounder, and feedlot cattle. The USDA National Animal Health Monitoring System indicates that it is the most common illness in cattle placed in feedlots, and the incidence has increased from 10.3 percent in 1994 to 16.2 percent in 2011. With more cow-calf producers being ask to wean and/or precondition their calves before selling them, a review of the disease might be helpful.

BRD develops as a result of interaction between environmental factors and pathogens. Environmental factors such as parasites, dust, weather, weaning, castration, dehorning, crowding, transportation, poor ventilation, and commingling stress the calves’ immune systems. Compromising the immune system allows viral and bacterial pathogens to invade the respiratory system. Viruses such as Infectious Bovine Rhinotracheitis (IBR), Bovine Viral Diarrhea (BVD), Parainfluenza Type-3 (PI3), and Bovine Respiratory Synctial Virus (BRSV) can decrease the bodies’ defense mechanisms by physically damaging the respiratory tract or, in the case of BVD, comprising the immune system. The combination of these factors allow for the seeding of bacteria into the lungs. Common bacteria involved in BRD are Mannheimia heamolytica, Pasteurella multocida, Histophilus somni, and Mycoplasma species.

At some point in this process, the body has an immune reaction to combat the disease. This is the time when clinical signs of disease begin to be seen. Typical clinical signs are fever, coughing, ocular discharge, nasal discharge, breathing difficulties, reluctance to eat, and reluctance to move. These signs maybe difficult to observe in the early stage of the illness but normally become more severe as the disease progresses.

If the disease is diagnosed early, then treatment with most antibiotics will be successful. However, a delay in diagnosis and treatment will result in more complications and failures. Dee Griffin, DVM, MS, West Texas A&M University, uses the acronym DART to teach producers how to detect the early signs of pneumonia. DART stands for depression, appetite, respiration, and temperature. Normal cattle are alert and stay with the group.

Mildly depressed cattle have droopy ears and head but are easily stimulated. Moderate depressed cattle have droopy ears and head, act listless, and are sore. Severely depressed cattle are weak and close to dying. Cattle should have aggressive eating behavior. Cattle that are reluctant to eat are ill. Respiration rate should be 10 to 30 breaths per minute. No noise should be heard on inspiration or expiration. Open mouth breathing is abnormal. Cattle temperature needs to be taken in the morning. A temperature above 103.5 degrees Fahrenheit is abnormal. The key to early detection is knowing normal cattle behavior and recognizing the first hint of abnormal signs.

Learn more in the latest issue of OKFR!