Nasal discharge may be serous, catarrhal, purulent, or hemorrhagic, depending on the degree of mucosal or turbinate damage. It indicates increased production of normal secretions, sometimes supplemented by neutrophils (purulent) or blood (hemorrhage). It probably also indicates decreased “grooming” of the nostrils with the tongue when animals are ill. Epistaxis (bleeding from the nose) is often caused by vascular rupture, such as in mycotic infection of the guttural pouch or exercise-induced pulmonary hemorrhage in horses, or by intranasal fungal infection or neoplasia, systemic coagulopathy, vasculitis, thrombocytopenia (immune-mediated or a result of rickettsial infection), hyperviscosity syndrome, hypertension, or nasal trauma. Hemoptysis (the coughing up of blood) occurs after rupture of pulmonary aneurysms in the lungs of cattle with chronic lung abscesses. Bleeding may also result from polyps, neoplasms, granulomas, trauma, thrombocytopenia, and bracken fern or sweet clover toxicity.
Hyperpnea (an increase in rate and depth of breathing) becomes dyspnea when the breathing appears to be labored and causing distress. Hyperpnea, however, is not always a sign of disease (eg, labored breathing after vigorous exercise in an otherwise healthy animal). Infectious respiratory diseases that cause toxemia may further compromise the host, eg, bovine pneumonia due to M haemolytica. Dyspnea can be caused by disease of the respiratory tract itself (eg, airway obstruction, pneumonia, bronchitis, or alveolitis) or by other problems (eg, heart failure, acid-base imbalances, thoracic effusions, abnormal oxygen-carrying capacity of the blood, or disorders of neuromuscular function). Labored inhalation seen with obstructive diseases above the thoracic inlet (eg, laryngeal paralysis, cervical tracheal collapse) or with pleural effusions is termed inspiratory dyspnea; labored expiration seen with obstructive diseases below the thoracic inlet (eg, diffuse bronchitis, principal bronchial collapse, or pulmonary edema) is termed expiratory dyspnea. Fixed airway obstructions (eg, tracheal neoplasia, foreign body, or stenosis) or a combination of upper and lower obstructive airway diseases (eg, pleural effusion with congestive heart failure) result in both inspiratory and expiratory dyspnea. Other responses include coughing, clear exudates, and shallow breathing with grunting, often associated with the pain of pleuritis.