Bovine Respiratory Disease (BRD) is a widespread and economically significant health challenge affecting cattle globally. This complex condition involves multiple factors that compromise respiratory health. Addressing BRD requires understanding its causes, recognizing its signs, and implementing effective prevention and treatment strategies.
Understanding Bovine Respiratory Disease
Bovine Respiratory Disease, often called “shipping fever,” is a multifactorial illness influenced by environmental elements, host characteristics, and various pathogens. It is the most common and costly disease impacting the North American beef cattle industry, causing substantial economic losses. BRD develops when stress factors, sometimes combined with viral infections, suppress the animal’s immune defenses. This allows bacteria to proliferate in the upper respiratory tract and eventually colonize the lower respiratory tract, leading to bronchopneumonia.
Several infectious agents contribute to BRD. Common viral agents include Bovine Viral Diarrhea Virus (BVDV), Infectious Bovine Rhinotracheitis (IBR) virus, Parainfluenza-3 (PI3) virus, and Bovine Respiratory Syncytial Virus (BRSV). These viral infections compromise the host’s defenses, making cattle more susceptible to secondary bacterial infections. Bacterial agents frequently involved are Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, and Mycoplasma bovis. These bacteria are found in the respiratory tract of healthy animals but become problematic under stressful conditions.
Environmental and management stressors weaken an animal’s immune system, increasing susceptibility to BRD. Transportation over long distances can lead to exhaustion, dehydration, and chilling. Commingling cattle from different sources, weaning, and diet changes contribute to stress. Overcrowding, inadequate ventilation, and extreme weather conditions further enhance disease risk by stressing animals and facilitating pathogen transmission.
BRD largely affects young, naive cattle, particularly during stressful periods like weaning and transport to feedlots. The disease frequently manifests within 45 days of arrival at a feedlot, with morbidity rates potentially reaching 35–50% and case fatality rates ranging from 5–10%. The severity of BRD is linked to environmental and nutritional changes, transportation, and the social reorganization of weaned calves.
Recognizing BRD
Early identification of Bovine Respiratory Disease is important for effective intervention. Clinical signs of BRD vary but often include systemic illness and respiratory distress. A common indicator is fever, with affected animals typically having rectal temperatures above 104°F (40°C).
Other observable signs include depression, lethargy, and a reduced appetite. Respiratory changes include nasal and ocular discharge, which may progress from watery to thick. Coughing, rapid, shallow breathing (tachypnea), and difficulty breathing (dyspnea) are common. Affected cattle may also show an ear droop, an arched back, or an unwillingness to move.
Caretakers can monitor for these signs through daily observation, which aids early detection. Since clinical signs can be subtle or inconsistent, scoring systems like the DART (Depression, Appetite, Respiration, Temperature) method are used to objectively assess and identify animals needing further examination.
Veterinarians employ various diagnostic methods to confirm BRD. A physical examination, including auscultation of the lungs, can reveal abnormal sounds like crackles and wheezes. Laboratory tests, such as nasal swabs or blood tests, can be submitted to an animal disease diagnostic laboratory for pathogen identification. Thoracic ultrasonography can detect lung consolidations, which are lesions of bronchopneumonia and may appear before clinical signs.
Proactive Prevention Strategies
Preventing Bovine Respiratory Disease involves a multi-faceted approach, with vaccination programs reducing disease incidence and severity. Vaccines protect against common viral pathogens like IBR, BVDV, PI3, and BRSV, as well as bacterial pathogens such as Mannheimia haemolytica and Pasteurella multocida. The timing and frequency of vaccination, whether pre-weaning or post-weaning, are considered for effectiveness. Modified live vaccines (MLV) and killed vaccines are available; MLVs often require fewer doses, while killed vaccines typically need a two-dose series.
Management practices minimize stress and improve cattle immunity. Providing adequate ventilation, maintaining clean and dry living environments, and reducing overcrowding help mitigate environmental risks. Minimizing stress during handling and transportation is beneficial, as stress can compromise the immune system. Deworming cattle one to two weeks before vaccination can improve their immune response.
Proper nutrition, including mineral supplementation, supports immune function and reduces BRD risk. Deficiencies in nutrients like Vitamin E and selenium can impair immune responses. Ensuring calves receive adequate, high-quality colostrum shortly after birth is important for developing a robust immune system. Colostrum provides passive immunity, helping calves resist pneumonia-causing organisms.
Implementing biosecurity measures helps prevent disease introduction and spread within a herd. Weaning strategies that reduce stress, such as preconditioning calves at home for 45 days before transport, improve calf health and performance. Training calves to use feed bunks and water tanks before entering a feedlot helps them acclimate and reduces stress.
Treatment and Recovery
Once Bovine Respiratory Disease is diagnosed, prompt intervention and supportive care are important for recovery. Antibiotics are the primary treatment for bacterial infections associated with BRD. Their selection often depends on efficacy, spectrum of activity, and the farm’s historical antimicrobial susceptibility profile. Commonly used antibiotics include florfenicol, tulathromycin, tildipirosin, and ceftiofur, many of which offer long-lasting effects or single-dose convenience.
Anti-inflammatory drugs, such as non-steroidal anti-inflammatory drugs (NSAIDs), are often used with antibiotics. These medications help reduce fever and discomfort, which can encourage sick animals to eat and drink, thereby aiding recovery. Some commercial products combine an antibiotic with an NSAID in a single dose for convenience.
Supportive care measures are important for recovery. Providing a clean, dry, and comfortable environment with adequate bedding is beneficial. Ensuring continuous access to fresh water and palatable feed helps prevent dehydration and maintain nutritional intake. Isolating sick animals from the herd prevents further disease transmission and allows for focused care.
Monitoring treated animals for improvement and potential relapses is important. If an animal shows no improvement within 24-48 hours, a change in antibiotic or further veterinary consultation may be necessary. The recovery timeline can vary, but the goal is to return animals to their home pens as soon as they are stable. A veterinarian plays a significant role in diagnosis, establishing treatment protocols, and overall herd health management, often recommending specific vaccines and antibiotics based on the farm’s needs and local pathogen prevalence.