Bovine respiratory syncytial virus (BRSV) is a major cause of respiratory disease and welfare harm in young cattle, causing severe bronchiolitis that can result in long-term pulmonary damage even in survivors.
BRSV causes acute respiratory distress that is among the most visibly distressing conditions in young cattle — calves with severe bronchiolitis struggle to breathe, show open-mouth breathing, and may develop subcutaneous emphysema from rupture of over-inflated lung tissue. The acute suffering of severely affected calves is significant and immediate. Long-term welfare harm extends to survivors: permanent lung consolidation reduces respiratory capacity and exercise tolerance, affecting welfare throughout the animal's life. Prevention through vaccination and management — age-segregated housing, adequate ventilation, and minimising stress during the high-risk weaning and housing transition period — reduces both the incidence of acute suffering and the prevalence of permanent pulmonary damage in surviving cattle.