From a mob of in-calf heifers grazing regrowth rape, 3 heifers were noticed with an unusual grunting cough. Twenty four hours later, two of these heifers died. Post mortem of these affected heifers showed unusual inflammation in the lungs. This was confirmed by the lab to be "Acute Bovine Pulmonary Emphysema and Odema" or "Fog Fever" for short. The third heifer was treated symptomatically but died 36 hours later. Fog Fever is a James Herriot era name and the disease probably has nothing to do with fog and more to do with the fact the disease is more commonly seen in the autumn. A rapid change in feed (also a risk factor for Vitamin B1 Deficiency) causes a particular gut bacteria to convert L-Tryptophan, a naturally occurring amino acid, to a toxic compound. The toxin rapidly impairs lung function resulting in death. No treatment is available but identifying the condition and removing affected animals from the paddock will prevent any new cases.