Pasture levels of tryptophan in relation to outbreaks of fog fever.

Oral administration of tryptophan induces in cattle clinical signs and lung lesions similar to those of fog fever. Tryptophan assays were performed by a microbiological method on various herbage samples. There was no significant difference in tryptophan content between herbage from two normal pastures and from three pastures in which outbreaks of fog fever occurred.