Which of the following is NOT a common symptom of respiratory disease in dogs?

In the context of respiratory diseases in dogs, increased appetite is not a common symptom. Typically, respiratory issues lead to a variety of clinical signs that reflect the compromised state of the respiratory system. Dyspnea, or difficulty breathing, is a hallmark symptom seen in dogs with respiratory distress, as it directly relates to their ability to get adequate oxygen. Exercise intolerance is also common because affected dogs may become quickly fatigued or struggle with physical activity due to inadequate oxygenation. Fever can occur as a response to infections or inflammation in the respiratory tract, indicating the body is fighting an underlying issue.

In contrast, increased appetite is generally not associated with respiratory diseases; rather, it might be seen in conditions that are unrelated or in contrast to dogs experiencing discomfort or illness. Typically, dogs with respiratory problems may have decreased appetite due to discomfort, difficulty breathing, or underlying systemic illness. Thus, increased appetite distinctly stands out as a symptom that does not align with the typical manifestations of respiratory disease in dogs.