Mimosine is a non-protein amino acid found in leaves, pods and seeds of tropical legumes of the genus Leucaena. Mimosine is degraded in the rumen to 3-hydroxy-4(1H)-pyridone (3,4DHP), a goitrogen. Leucaena consumption in ruminants may cause poor growth, alopecia, swollen and raw coronets above the hooves, lameness, mouth and esophageal lesions, depressed serum thyrosine levels, and goiter. Susceptibility of ruminants to intoxication, however, greatly depends on specific microbial populations. Further transfer of ruminant fluids from a resistant animal to a susceotible one results in a complete elimination of the toxic effects of Mimosine. This appears to be a possible solution to the toxicity of leucaena in ruminant animals.