Simplified Cultural Test for Ruminal Bacteria That Degrade Toxic Dihydroxypyridine Derivatives of Mimosine

Introduction. The toxic nonprotein amino acid mimosine present in Leucaena leucocephala is degraded by rumen bacteria to produce another toxic compound, 3-hydroxy-4(lH)-pyridone (3,4-dihydroxypyridine, or 3,4-DHP). In some, but not all, geographic areas ruminants are colonized by bacteria that degrade 3,4-DHP, and actions of these microbes protect their host animals from leucaena toxicosis (Jones 1985, Kudo et al. 1989, Dominguez-Bello and Stewart 1990). When 3,4 DHP-degrading bacteria were inoculated into previously uncolonized ruminants, they became established in the rumen, were transferred from animal to animal and provided protection from leucaena toxicosis (Jones and Megarrity 1986, Hammond et al. 1989). To help with assessment of the need for inoculation with 3,4DHP-degrading organisms, we described cultural methods that detect 3,4-DHP-degrading bacteria in rumen microbial populations (Allison et al. 1990). The present study describes a modification of those methods that should simplify and facilitate field tests for the presence of 3,4DHP-degrading bacteria in rumen microbial populations.