What is Bovine Respiratory Disease? Part 1: Symptoms

Bovine Respiratory Disease (BRD)

Bovine respiratory disease (BRD) is one of the most common and costly causes of illness and death in Australian cattle. BRD is a general term for any respiratory disease in cattle that affects the lower or upper respiratory tract. BRD is commonly associated with infections of the lungs, pneumonia in recently weaned and feedlot cattle, nursing beef calves, housed dairy calves, and lactating dairy cows.

General signs of BRD are:

  1. Fever, usually over 40°C: BRD is one of the most common causes of fever and fever is always one of the earliest signs of BRD complex
  2. Depression: Affected animals hang their heads, look lethargic and often stand away from other cattle.
  3. Lack of appetite: Often with fever and/or depression the animal will be unwilling to eat. An early indication of this is when the animal has a "floppy" belly from lack of fibre in the digestive tract.
  4. Serous nasal and eye discharge: One of the earliest indicators of BRD, serous discharge is watery, sticky and clear and generally starts from the nose, then moves to the eyes as the disease progresses.
  5. Purulent nasal discharge: Usually a sign of more advanced BRD is thick, cloudy and pus-filled discharge. The cloudy appearance is caused by white blood cells gathering in the respiratory tract to fight the infection.
  6. Bloody nasal discharge. In advanced BRD cases, blood can appear in the nasal discharge when the respiratory tract is irritated. When the protective mucosal lining is broken down it enters the respiratory system and is blown out.
  7. Stiff gait: An increased systemic endotoxin load can cause muscle and joint soreness for the animal.
  8. Crusty muzzle: When an animal is not well it will not take very good care of itself and will stop licking its hair and muzzle. Mild dehydration which dries membranes around the mouth combine with this to create a crusty appearance.
  9. Respiratory signs:
    • Rapid, shallow and difficult breathing: More blood is directed to the infected lung area, blocking airflow and as a result the animal has to breathe harder to get adequate air.
    • Coughing: In early stages of BRD, the lungs and airways are generally painful, so the animal will attempt to clear the airway with tentative coughing. Louder coughing or "honking" suggests a more chronic, advanced BRD where treatment is difficult.
  10. Salivation: The animal's overall feeling of sickness may cause it to salivate more than usual.
  11. Mild diarrhoea: Endotoxins in the animal's system cause displacement of body fluids, which moves more fluid into the bowel and prevents normal absorption of food, which in turn causes loose stools.


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