Bovine Respiratory Disease (BRD) is a significant and costly health challenge in global livestock production. This complex syndrome affects the respiratory system of cattle and is the leading cause of sickness and death in young animals in the beef and dairy industries. Understanding the causes, recognizing the symptoms, and implementing proactive management strategies are fundamental to mitigating its widespread impact.
What is Bovine Respiratory Disease
Bovine Respiratory Disease is a multi-factorial syndrome, not a single infection, that causes illness in the upper and lower respiratory tracts of cattle. It is often called “shipping fever” because outbreaks frequently follow the stress of transportation and commingling of animals. BRD is the most economically damaging disease in the North American beef industry, with annual losses estimated between $800 and $900 million due to death loss, reduced feed efficiency, and treatment costs.
The disease primarily affects calves and recently weaned cattle, especially those introduced into feedlot systems. These young animals are highly susceptible because their immune systems are often compromised by stress and exposure to new pathogens. In feedlots, BRD can account for 65% to 80% of all sickness and a large portion of mortality.
Viral, Bacterial, and Environmental Contributors
BRD develops when three factors align: a susceptible animal, the presence of pathogens, and environmental stressors. Viral agents typically initiate the disease process by damaging the lining of the respiratory tract. Primary viral culprits include:
- Infectious Bovine Rhinotracheitis (IBR)
- Bovine Viral Diarrhea (BVD)
- Parainfluenza 3 (PI3)
- Bovine Respiratory Syncytial Virus (BRSV)
This viral damage compromises the animal’s natural defenses, allowing opportunistic bacteria, often already present in the upper respiratory tract, to invade the lungs. The most common bacteria causing severe pneumonia are Mannheimia haemolytica and Pasteurella multocida. The resulting bacterial infection causes inflammation and fluid buildup in the lungs.
Non-infectious factors act as potent triggers by weakening the immune system. Stressors like weaning, long-distance transport, and mixing cattle from different herds are major contributors. Environmental factors such as poor ventilation, high humidity, excessive dust, and sudden weather changes also compound the immune challenge.
Identifying the Clinical Signs
Early detection of BRD is important because the disease can progress rapidly from a mild respiratory infection to life-threatening pneumonia. The earliest signs are often behavioral, including lethargy, a hunched posture, and a loss of appetite. Affected cattle may separate themselves from the group and show general depression.
Physical symptoms commonly begin with a fever, often exceeding 104°F (40°C). Nasal discharge is typical, ranging from clear and watery in the early stages to thick, cloudy, or pus-like as the bacterial infection worsens. Other observable signs include a wet or dry cough, rapid or labored breathing, and neck extension as the animal struggles to take in air.
If the condition is left untreated, lung damage caused by bacterial pneumonia leads to permanent scarring and reduced lung function. This can result in chronic illness, stunted weight gain, and a higher likelihood of death. Recognizing initial signs allows for successful intervention.
Intervention and Control Measures
Effective BRD management relies on a comprehensive strategy combining preventive control measures with timely therapeutic intervention. Prevention focuses on minimizing stress during high-risk periods like weaning and transport. Implementing low-stress handling techniques and providing adequate nutrition, especially mineral supplementation, helps maintain a robust immune system.
Vaccination programs are a primary method of control, targeting the viral and bacterial components of the disease complex. Producers utilize a combination of injectable and intranasal vaccines against agents like IBR, BVD, and M. haemolytica. Vaccination timing is important, requiring the series to be completed well before a planned stress event like shipping to allow the immune system time to build protection.
Intervention for sick animals centers on using antibiotics to target the bacterial pneumonia component. Macrolides, phenicols, and fluoroquinolones are common classes of antibiotics used for BRD treatment. A Non-Steroidal Anti-Inflammatory Drug (NSAID) is often administered alongside the antibiotic to reduce fever and inflammation, improving comfort and recovery.
In high-risk groups, a strategy called metaphylaxis may be employed, involving the mass administration of antibiotics upon arrival to prevent expected disease outbreaks. Treatment protocols should be guided by veterinarians, often reserving certain classes of antibiotics for treatment failures to mitigate antimicrobial resistance. Prompt, appropriate treatment is the best defense against severe disease and death loss.