What is a common symptom of respiratory disease in livestock?

Coughing and nasal discharge are hallmark symptoms of respiratory disease in livestock. These signs indicate irritation or infection in the respiratory tract, which can result from various pathogens such as viruses, bacteria, or environmental stressors. When livestock experience respiratory issues, the body's immune response may lead to inflammation and excess mucus production. This not only causes nasal discharge but also triggers a cough as the animal attempts to clear the airway. Recognizing these symptoms is crucial for timely diagnosis and treatment, as respiratory diseases can significantly impact the overall health and productivity of livestock.

Increased weight gain typically does not occur in animals suffering from respiratory conditions, as these animals often experience reduced feed intake and overall health. Lower feed intake and reduced activity levels can be secondary effects of respiratory diseases, but the direct clinical signs include coughing and nasal discharge. This makes option B the most representative of the common symptoms associated with respiratory diseases in livestock.