Induction of pulmonary edema and emphysema in cattle and goats with 3-methylindole.

Microorganisms from rumen converted L-tryptophan and indoleacetic acid to 3-methylindole in vitro. Oral doses of 3-methylindole caused interstitial pulmonary edema and emphysema in cattle and goats. Intravenous infusion of this metabolite also induced pulmonary disease in cattle. These results demonstrate than an end product of ruminal fermentation of tryptophan can induce acute pulmonary disease in cattle and goats.