The Bovine Respiratory Disease Complex (BRD) groups together different diseases affecting the respiratory system of cattle, such as bronchopneumonia. It is commonly referred to as shipping fever in feedlot cattle or enzootic calf pneumonia in young dairy calves.
BRD is the most common and costly disease complex in North American Beef and Dairy Cattle(1,2).
Several factors contribute to BRD, some of which are of particular importance:
- Animal: age, anatomy, source, and immune status
- Management: handling, housing conditions, vaccination status, biosecurity measures
- Microbes: multiple bacterial and viral agents are involved
BRD is commonly associated with immunosuppressive situations caused by stressful factors such as transporting, loading, and commingling of cattle.
Gram negative bacteria, an organism frequently found in the normal respiratory tract of ruminants with overgrowth causing severe lesions of the pulmonary parenchyma.
Gram negative bacteria and commensal organism found in the deep pharyngeal region, especially in young calves, inducing lung inflammation.
Gram negative bacteria and commensal organism of the nasopharyngeal region and lower respiratory tract, producing histamine which may explain early respiratory damage.
Anaerobic bacteria of the deep respiratory tract, causing the lipid peroxidation of the host cell wall, and responsible for the phenotypic variation allowing evasion of the immune responses of the host.
Bovine Herpesvirus Type 1 (BHV-1) or Infectious Bovine Rhinotracheitis (IBR) as it is commonly known, initially infects the epithelial cells of the upper respiratory tract, then spreads to the lower respiratory tract and induces immunosuppression. The IBR virus causes permanent infections.
Bovine Parainfluenza virus type 3 (PI3), together with other pathogens, forms the complex of enzootic pneumonia and causes primary infections in the epithelial cells of the trachea, bronchi and alveoli, causing necrosis of the ciliated epithelium and leading to mucociliary erosion. This predisposes the lung tissue to secondary bacterial infections.
Bovine respiratory syncytial virus (BRSV) can be considered a primary pathogen of BRD. The primary infection begins in the nasal cavity, pharynx, trachea, bronchi and bronchial epithelial cells. It induces cilia loss or necrosis of bronchial and bronchiolar epithelial cells, providing an ideal environment for bacterial colonization. Ultimately, severe BRSV infection can result in subcutaneous emphysema.
Bovine Viral Diarrheal (BVD) virus destroys alveolar macrophages inducing immunosuppression, and is associated with a wide spectrum of disease.
Bovine respiratory coronavirus contributes with other agents to enzootic calf pneumonia or shipping fever.
The simultaneous management of several risk factors is critical to properly deal with preventive and therapeutic approaches of BRD.
Sex, Age, Weight at arrival, Immune system status, Operating procedures, Quarantine & Acclimation process, Vaccination
Mineral and vitamin supplementation
Space at the feed bunk, Pen design, Cooling system
Balance ration, Mineral and vitamin supplementation
Symptoms usually develop within 4 weeks after weaning / shipment in beef calves and can range from mild to severe.3