How to prevent Fog fever in dairy cows

Fog Fever | Causes | Symptoms | Prevention | Cure 

Also known as Acute Bovine Pulmonary Edema and Emphysema (ABPEE).

Fog fever is an acute pneumonia of adult cattle which occurs within four to 10 days of moving from an over grazed pasture or dry feed, to a fresh, lush green pasture. The condition develops rapidly.

It typically occurs in Autumn, five to 10 days after the change to lush grass.

How to prevent Fog fever in dairy cows
How to prevent Fog fever in dairy cows


The affected cattle have been on dry feed for an extended period of time and the rumen fermentation pattern has adapted to this situation. With the change to lush green pasture the dietary protein concentration increases dramatically. One of the amino acids in this plant protein, tryptophan, is the culprit. The tryptophan in the feed is converted by rumen bacteria to a substance called 3-methylindole (3-MI) at a very high rate.

This 3-MI is absorbed through the rumen wall and circulated around the body. The 3-MI is toxic to the primary cells that line the interior surface of the lungs. Thus, as the high levels of 3-MI move from the rumen to the lungs more and more lung tissue is destroyed.


  • Difficulty breathing
  • Coughing
  • Frothing at mouth
  • Cattle do not normally run a fever
  • Anxiety (separation from group)
  • Collapse
  • Death


There is no specific treatment for fog fever. Mild cases may recover without treatment.

Most severely affected cattle will not respond to any treatment and will die within a day or two.

Removing cows from pasture has not been scientifically proven to reduce cases. Some believe it prevents further cases, whilst others believe that moving sick animals can make the disease worse.


Limiting time grazing in the first 10 days when cattle are moved to a new pasture will reduce the chances of cattle falling ill.

Allowing cattle to graze a couple of hours a day and building this up is advisable.

It is also thought that feeding monensin or chlortetracycline for the first 10 days can help control the situation.

Prevention is important as it is common for 50 per cent of a herd to become ill, and up to 30 per cent may die.

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