Home › Animalia › Animal health › Animal diseases › Calf bronchopneumonia
Calf bronchopneumonia
Bronchopneumonia is the main disease of calves after the diarrhea period. It mainly strikes from the first month until several months of age, often during seasonal changes. This is not the work of a single microbe: viruses first weaken the...
What is it?
Bronchopneumonia is the main disease of calves after the diarrhea period. It mainly strikes from the first month until several months of age, often during seasonal changes.
This is not the work of a single microbe: viruses first weaken the respiratory system, then bacteria take up residence in the lungs. The atmosphere of the building and the stress do the rest.
An affected calf breathes poorly, eats less, and pays for the damage to its lungs for a long time: growth suffers even after apparent recovery.
Key point
A calf does not cough “a little” for no reason. The subtle cough in the morning is the first call: that's when the treatment changes everything, not three days later.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Cough, initially dry and occasional, triggered by exercise or when calves are lifted.
Breathing faster at rest, then visible effort of the flanks.
Discharge from the nose, clear at first, thick and yellowish afterwards.
Watery eyes, dull eyes.
Fever, often the very first sign, even before the cough.
Decreased appetite, calf dragging to come to the bucket.
Dejection, dangling ears, calf which remains lying away from the crowd.
In severe forms: tense neck, open mouth, noisy breathing — it's an emergency.
In a batch, one or two calves start, then others follow within a few days.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Respiratory viruses lead the way by damaging the respiratory tract and local defenses.
Bacteria normally present in the calf's nose then travel down to the lungs and cause extensive inflammation there.
Mycoplasmas also participate, particularly in forms that persist and respond poorly to treatments.
The breeding conditions play a role at least as important as the microbes: humid environment, ammonia, cold air currents, mixture of animals of different origins.
Severe neonatal diarrhea or a lack of colostrum permanently weakens the calf and sets the stage.
Failure to transfer colostral immunity at birth.
Poorly ventilated building: humid air, smell of ammonia, condensation on the walls.
Drafts near lying calves, cold floors, damp bedding.
Overcrowding and mixing of calves of different ages or origins.
Significant temperature differences between day and night, frequent in autumn and spring.
Stress from weaning, transport, dehorning or a change in diet.
History of neonatal diarrhea.
Dietary deficiencies, particularly in trace elements and vitamins, which weaken the defenses.
Transmission
The agents are transmitted by respiratory route: droplets emitted by coughing, direct contact between calves, snout to snout.
Older animals in the herd often harbor these microbes without becoming ill and pass them on to younger animals.
The introduction of animals from another farm or from a market brings new agents into the mix.
Transportation, batch mixing and weaning are typical periods of contamination.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian takes the temperature, listens to the lungs on both sides and assesses the respiratory effort.
He examines the whole lot, because the disease is a collective problem: counting the calves which cough provides better information than an isolated examination.
Samples from the nose or by washing the respiratory tract make it possible to identify the agents involved and to test the sensitivity of bacteria to antibiotics.
Ultrasound of the lungs is increasingly used: it reveals lesions in calves that are not yet coughing.
The veterinarian also examines the building: ventilation, humidity, drafts, density. This environmental diagnosis is inseparable from the medical diagnosis.
Treatment
The treatment is based on an antibiotic chosen by the veterinarian, which is all the more effective if it is administered early: a calf treated as soon as fever recovers much better than a calf treated when it breathes with its mouth open.
An anti-inflammatory is often combined to reduce fever, calm inflammation in the lungs and restore appetite.
The treatment must be carried out to the end, even if the calf is better after two days: premature terminations explain a large part of the relapses.
Affected calves are isolated in a healthy, dry, well-ventilated room without drafts, with abundant bedding.
Water must remain accessible at all times; a feverish calf drinks more.
Correcting the atmosphere of the building is part of the treatment, not just prevention: without it, cases follow one another despite the injections.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Ensure early and sufficient colostrum intake: calves well equipped with antibodies have significantly fewer respiratory problems.
Take care of ventilation: renew the air without creating a draft near the lying calves. A smell of ammonia at eye level already indicates a defect.
Keep litter dry and abundant; humidity is the main enemy.
Respect batches of uniform age, without overcrowding, and practice all-full-all-empty with cleaning between two strips.
Avoid accumulating stress: do not wean, dehorn and change food in the same week.
Quarantine any introduced animals before mixing them with the batch.
Monitor daily: spotting cough and depression at mealtime is the best detection tool.
Ensure a balanced diet and permanent access to clean water.
Vaccination
Vaccines exist against the main calf respiratory viruses and against certain bacteria involved.
Some are administered nasally from the first weeks of life, which helps protect the young calf; others inject themselves, with an essential reminder.
Vaccination must be anticipated: it requires time to be effective and has no effect when applied in the midst of an epidemic on already affected calves.
The veterinarian chooses the vaccine according to the agents identified on the farm and sets the schedule for periods of risk, particularly before weaning, transport or entry into the building.
No vaccine compensates for a poorly ventilated building or insufficient colostrum.
Possible complications
Permanent lung damage: part of the lung may remain destroyed, leaving the calf short of breath and with reduced growth.
Repeated relapses, each episode worsening the condition.
Lung abscesses and pleurisy in severe forms.
Long-term growth retardation and, among future dairy cows, reduced subsequent production.
Death from respiratory failure in acute forms not treated in time.
When to see a veterinarian
Your calf coughs, even occasionally: don't wait for the cough to become wet.
He has a fever, eats less or hangs around meal times.
His breathing is rapid at rest or his sides are working.
He is breathing with his mouth open, his neck stretched: it's an emergency, call immediately.
Several calves in the group cough at the same time.
A treated calf relapses after a few days: the treatment or the environment must be reviewed.
Prognosis
A calf treated at the first signs most often recovers without after-effects.
Late treatment leaves damaged lungs: the calf survives but grows less well, coughs during exercise and relapses easily.
Mycoplasma forms hang around longer and respond less well.
At the batch scale, the results depend above all on the earliness of detection and the quality of the building's atmosphere.
Frequently asked questions
My calf is coughing a little but eating well: should I call?
Yes. Fever and lung damage often precede decreased appetite. A calf treated from the first cough recovers much better than a calf treated when it no longer eats.
Does the cold make calves sick?
The cold alone is better tolerated than one might think, provided that the calf is dry and sheltered from drafts. It is humidity, ammonia and drafts at ground level that cause bronchopneumonia, not the low temperature itself.
Can I stop the antibiotic as soon as the calf gets better?
No. Improvement precedes healing of the lungs. Stopping early exposes you to relapse and promotes resistance: follow the duration indicated by the veterinarian.
Should all calves be vaccinated?
It depends on the breeding, the agents identified and the risk periods. The vet decides. Remember that a vaccine applied in the middle of an epidemic arrives too late: vaccination must be anticipated.
Why do cases come back every winter despite treatment?
Because the main cause is often not medical. A damp, poorly ventilated or overcrowded building recreates the conditions for disease. Have the environment examined at the same time as the animals.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
ANSES — Agence nationale de sécurité sanitaire (France)
Content reviewed by the TunisieVet editorial team · Updated 09 August 2026
AT A GLANCE
Need a veterinarian?
Find a practitioner near you on TunisieVet, with their specialities, hours and contact details.
Find a veterinarianCategories
Affected species
This information is provided for educational purposes only and is not a substitute for a veterinary consultation. If you have any concerns about your animal's health, consult a veterinarian.
To discover
Related diseases and linked Animalia content.
Rabies
Viral · Vaccine available
Babesiosis
Parasitic
Leptospirosis
Bacterial · Vaccine available
Foot-and-mouth disease
Viral · Vaccine available