One of my cows coughs, protrudes her tongue, and breathes with her mouth open. Is this an indication of health issues?

The cow most likely has a lung disease in which inflammation elicits an irritated cough and reduced air space which encourages open-mouth breathing. Since a number of infectious and noninfectious causes are possible, professional assistance is necessary to make a specific diagnosis by physical and laboratory examinations.

Infectious Lung Disease (Pneumonia)
Pneumonia is a common infectious disease that is a possibility. Fever, coughing, and labored breathing are present due to inflammation and swelling of the lungs and accumulation of mucus, blood, and pus in the air passages that interfere with airflow. In an attempt to get more air, the head and neck are outstretched, and the tongue protrudes. Pneumonia is a highly complex, contagious disease and may be caused by one of several viruses in concert with various bacteria. Bacteria generally cause serious pneumonia, either as primary or as secondary invaders. Since predisposing stress factors contribute to the appearance of the disease by lowering the animal’s resistance, management directed toward adverse conditions of cattle is needed to prevent more cases of pneumonia in a cowherd. The sick cow must be isolated for treatment. It is concluded the infectious agents are harbored in the cowherd; therefore, it is advisable to know by laboratory tests the specific viruses or bacteria involved to develop an effective vaccination plan. The plan should include vaccinating the cows, nursing calves, bulls, and replacements with the proper vaccines.

Fog Fever (Pulmonary Emphysema and Edema) is a common noninfectious condition that is another possibility. With fog fever, fever is not present, the coughing is minimal, the respiratory distress is extensive, and the onset of symptoms is sudden. Difficult breathing is obvious with mouth breathing, extended tongue, and drooling saliva. The lung damage is the result of a toxic reaction in the lungs following an intake of a large quantity of an amino acid in lush, green grass in spring or fall. Diagnosis is based on a history of moving the cows from a dry, brown pasture to a lush, green pasture within the last 10 days. The affected cow should be appropriately treated and handled with caution to prevent death by suffocation brought about by exercise. The cowherd should be moved from the lush pasture and gradually returned over three weeks by feeding hay and limiting grazing time.