Detection of ruminal bacteria that degrade toxic dihydroxypyridine compounds produced from mimosine

Leucaena leucocephala, a tropical leguminous shrub, contains a toxic amino acid, mimosine. Successful utilization of leucaena as a ruminant forage depends on colonization of the rumen by bacteria that degrade dihydroxypyridines (DHP), which are toxic intermediates in the metabolism of mimosine. Populations in the rumina of animals in some parts of the world, however, do not include bacteria that are able to carry out this degradation. We thus describe tests for the presence of DHP degraders in ruminal populations that are based on degradation (loss) of DHP compounds from culture media. Results obtained with the tests indicate that DHP degraders were not part of microbial populations in the rumina of cattle, sheep, and goats in Iowa, while most rumen samples examined from animals from the Virgin Islands and Haiti contained DHP degraders. These results confirm and extend the findings of others about geographic limits to the distribution of these important ruminal bacteria.