What causes calves to have runny, snotty noses?

Runny, snotty nose can possibly be associated with pneumonia if the calves have fever, are coughing, and have labored breathing; otherwise, the calves may simply have an inflammation of the sinuses of the head, which is called sinusitis. Runny, snotty nose (sinusitis) nasal drainage in calves may be normal discharging of secretions of mucus from the sinuses of the head. Excess quantities of drainage from inflamed sinuses are evident during days of extreme hot or cold temperatures, or windy conditions, even in the absence of infections. Also, irritants and allergens in the environment, such as dust, pollen, and mold, cause inflammation of sinuses. Viral and bacterial infections inflame the sinuses, produce a head cold, and cause a nasal discharge that is a clear mucus or pus type. Quite often, the infection is limited to the head without involvement of the lungs. Use of antibiotics is contraindicated with low-grade fever and in the absence of fever, in which the condition is allowed to run its course. Respiratory vaccines may lack the specific antigens to prevent recurrence.