Ask the Vet

Grazing Cautions to Avoid Atypical Pneumonia

Avoid sudden nutritional changes and gradually introduce lush forages to help control issues with atypical pneumonias. (DTN/Progressive Farmer file photo by Troy Salzer)


We found one of our cows slobbering and struggling to breathe. We got her up and gave her Draxxin and Banamine, but the next day she died. We took her to our state diagnostic lab, which said she had atypical pneumonia, and antibiotics would not have helped. Can you explain what is going on and how we can control this in the rest of the herd?


This was probably a case of what I call atypical interstitial pneumonia. It has a lot of other names, way too many -- acute bovine pulmonary emphysema and edema, fog fever, pulmonary emphysema, acute bovine respiratory distress syndrome and bovine asthma. Adult cattle are typically affected.

In the Southeast, it's most commonly caused by the consumption of perilla mint. In the West and Canada, it occurs when cattle are turned onto lush pastures in late fall and winter. It's also common in feedlots during the finishing period. Consumption of moldy sweet potatoes can also cause it.

When the condition is linked to lush pastures, the cause is thought to be breakdown products from an amino acid (tryptophan) that leads to severe cellular injury in the lung. Perilla mint (also known as purple mint, wild coleus and beefsteak plant) is an invasive species that thrives in late summer and fall in the Southeast, when pastures are often dry, short and dormant. This is also when these plants are most toxic. Cattle typically avoid these if adequate forages are available. If they ingest them, however, a toxic ketone is absorbed from the rumen and carried to the lungs, where it damages the lung tissue.

Signs come on suddenly with severe respiratory distress and minimal coughing. Antibiotics are of no benefit and many animals die even with supportive care.

You ask about control, and that really depends on the cause of the disease. A good management practice is to avoid any sudden change in nutrition in the herd, and certainly to gradually introduce lush forages. There is evidence that ionophores, and especially monensin (Rumensin), are beneficial if the cattle are on it prior to going onto lush pastures. Moldy sweet potato control is easy -- don't feed moldy sweet potatoes. With perilla mint, making sure cattle have adequate forage, hay or feed helps to prevent problems, but perilla mint is easily killed with a variety of herbicides.


Editor's Note: Please contact your veterinarian with questions pertaining to the health of your herd or other animals. Every operation is unique, and the information in this column does not pertain to all situations. This is not intended as medical advice but is purely for informational purposes.

Write Dr. Ken McMillan at Ask the Vet, 2204 Lakeshore Dr., Suite 415, Birmingham, AL 35209, or email