Respiratory Disease in Young Calves: Recognition, Treatment, and Prevention

BRD Is the #1 Killer of Calves Over a Month Old, and Early Detection Is Everything

Respiratory disease is the second leading cause of death in young calves (after scours) and the leading cause of death in calves over one month of age. Often called "pneumonia" or "shipping fever," bovine respiratory disease (BRD) costs the U.S. cattle industry over $1 billion a year through death loss, treatment costs, and reduced performance.

This guide focuses on respiratory disease in pre-weaning calves: recognizing early signs, understanding causes, treating effectively, and preventing outbreaks through management.

Why Calves Are Vulnerable

Calves have small lung capacity relative to body size, with narrow airways that are easily obstructed, fewer alveoli (air sacs) than adults, and less respiratory reserve to fall back on. Their immune system is still developing, dependent on colostrum for initial immunity that wanes at 2-4 months while active immunity is still building. On top of that, environmental factors like poor ventilation in confined housing, dust, ammonia exposure, and a heavy pathogen load all work against them.

The Disease Process

Respiratory disease typically involves multiple factors hitting in sequence. First, some stressor suppresses immune function and impairs the normal respiratory defenses. Then a viral infection (IBR, BVD, PI3, BRSV) damages the respiratory lining and opens the door for bacteria. Secondary bacterial invaders like Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, and Mycoplasma bovis move in and cause the real damage, including tissue death in severe cases and permanent lung scarring.

Risk Factors in Young Calves

Colostrum and Passive Immunity

Environmental Risk Factors

Weather-Related Risk

Cold weather leaves calves with less immune reserve, and wet cold is the worst combination. Calves in enclosed shelters may face poor air quality. Hot weather brings increased respiratory rates, dust problems, and makes water availability critical. Rapid temperature swings increase stress and act as a classic BRD trigger.

Recognizing Respiratory Disease

Early Signs (Catch These)

The earliest signs are behavioral: head lowered, ears drooping, reduced nursing or appetite, and slower movement. Mild respiratory signs follow, including an occasional cough, slightly increased breathing rate, and eyes that appear dull.

Progressive Signs

As the disease advances, breathing becomes labored. The calf extends its neck trying to open the airway, nostrils flare, and you may hear audible breathing sounds. Nasal discharge appears on the nose or muzzle, sometimes as crusty material around the nostrils. Systemically, the calf shows depression, stops nursing, loses weight, and develops a rough coat.

Severe/Advanced Signs

In severe cases you will see elbows abducted (held out from the body), severe labored breathing, and potentially cyanosis (blue tongue and gums), which is life-threatening. The calf becomes profoundly weak, goes down, and may die rapidly.

The DART System for BRD Detection

A practical scoring system for identifying sick calves:

Temperature Assessment

How to Take Calf Temperature

• Use digital rectal thermometer
• Lubricate tip if needed
• Insert 2-3 inches into rectum
• Hold in place until reading complete
• Clean and disinfect between calves

Temperature Interpretation

Treatment Protocols

When to Treat

Treat immediately when the DART score is 3-4, the calf shows obvious respiratory distress, or the calf is not nursing and appears sick. Monitor closely and recheck when the DART score is 1-2 or the temperature is borderline.

Antibiotic Selection

Work with your veterinarian to establish treatment protocols. Common antibiotics for calf BRD:

Supportive Care

Keep the calf hydrated and make sure it is drinking; it may need supplemental fluids. Maintain nutrition by keeping the calf nursing or providing supplemental milk. Move the calf to a dry, draft-free area if possible, and check on it twice daily until recovered.

Treatment Response Assessment

What to Do When Treatment Fails

Treatment may fail because of resistant bacteria, Mycoplasma infection (which requires specific treatment), chronic lung damage already present, or other concurrent disease. Consult your veterinarian, who may switch to a different antibiotic. If a calf dies, a necropsy can identify the specific pathogen and guide changes to your protocol.

Preventing Respiratory Disease

Colostrum Management

Colostrum management is the foundation of respiratory disease prevention. Aim for quantity (10% of body weight within first 6 hours, which is about 4 quarts for an 80-lb calf), quality (high antibody content, check with a colostrometer), speed (within 2-4 hours of birth for best absorption), and cleanliness (use clean equipment, avoid contamination).

Vaccination Programs

Vaccinating cows pre-calving protects calves through passive immunity. Typical vaccines cover IBR, BVD, PI3, BRSV, and Leptospirosis. Intranasal vaccines can be given to calves earlier than injectable products. Work with your veterinarian on timing for your specific operation.

Environmental Management

Good housing management means dry bedding, avoiding overcrowding, and separating sick animals. For biosecurity, use all-in/all-out systems when possible, avoid mixing age groups, and maintain clean, well-drained areas.

Stress Reduction

Minimize handling stress by using proper facilities, avoiding running or excessive chasing, and combining procedures when possible. For weather management, provide shade in summer, bedding in cold weather, and ensure adequate water access year-round.

Special Situations

Outbreak Response

When multiple calves develop BRD, treat all sick calves promptly and separate them from healthy animals if possible. Review recent stress events and contact your veterinarian for guidance. Pursue diagnostics including necropsy of fatal cases to identify specific pathogens and determine antibiotic sensitivities. For long-term action, improve environmental conditions, review your vaccination protocol, and consider altering animal flow.

Chronic/Repeat Cases

Some calves develop chronic respiratory disease marked by failure to thrive, persistent cough, and an unthrifty appearance. In these cases, lung damage may be permanent. An honest economic evaluation is needed, and culling chronic cases may be the most practical decision.

Mycoplasma Infections

Mycoplasma bovis is increasingly recognized as a major cause of calf illness. It causes multiple problems (respiratory, joint, and ear infections) and can trigger outbreaks. It may not respond to typical BRD treatment. Watch for ear droop or head tilt (middle ear infection) and joint swelling alongside respiratory signs, especially when multiple calves are affected. Treatment typically involves extended courses, strong biosecurity to prevent spread, and close veterinary involvement.

Record Keeping and Analysis

What to Record

Analyzing Your Data

Look at the patterns in your records. At what age are most cases occurring? Are cases clustered by location or time? Which treatments are most effective? Are certain cow families producing more sick calves? Target benchmarks include BRD mortality under 2% and a case fatality rate under 10% of treated calves.

When to Call the Veterinarian

Urgent Situations

Call right away when a calf is not responding to treatment, shows severe respiratory distress, deaths are occurring, or symptoms are unusual.

Planned Consultation

Schedule time with your vet for treatment protocol review, persistent BRD problems, and pre-season planning.

What to Tell the Veterinarian

Prepare the age range affected, symptoms observed, treatments already tried, recent events (weather, handling), and vaccination history.

Prevention Checklist

Pre-Calving Season

• Cows vaccinated appropriately
• Calving areas clean and dry
• Colostrum management plan in place
• Treatment supplies stocked
• Veterinary relationship established
• Record system ready

Daily Management

• Observe all calves for early signs
• Temperature check any suspect animals
• Treat promptly when indicated
• Record all cases and treatments
• Isolate sick animals when possible
• Maintain clean, dry environment

Ongoing Evaluation

• Track morbidity and mortality rates
• Review treatment success
• Identify patterns
• Adjust protocols as needed
• Plan improvements for next season

The Bottom Line on Calf Respiratory Disease

Respiratory disease in young calves is largely a management problem with management solutions. You can't eliminate BRD entirely, but good colostrum management, the right vaccination program, clean environments, stress reduction, and early detection with prompt treatment can dramatically cut your losses. Pay attention to the early, subtle signs. Catching BRD early gives you the best chance of successful treatment and full recovery.

Related Resources

• Calf Scours Prevention and Treatment
• Navel Care and Infection Prevention
• Colostrum: The Critical First Hours
• Newborn Calf Assessment

References

• USDA APHIS. "Beef 2017: Health and Management Practices on U.S. Ranches." aphis.usda.gov
• Smith, R.A. "Impact of disease on feedlot performance: A review." Journal of Animal Science.
• Beef Cattle Research Council. "Bovine Respiratory Disease." beefresearch.ca
• University of Nebraska-Lincoln. "Respiratory Disease in Beef Calves." beef.unl.edu
• Step, D.L., et al. "Bovine Respiratory Disease in Stocker Cattle." Veterinary Clinics of North America: Food Animal Practice.
• Texas A&M AgriLife Extension. "Bovine Respiratory Disease Complex." agrilifeextension.tamu.edu