The tropical legume Leucaena leucocephala (leucaena) has many uses, including: a potential source of firewood and timber; for soil erosion control (Dijkman 1950); to provide shade; to enhance soil fertility; and as a nutritious forage for animal feed (Ruskin 1977). It is widely used as forage for cattle in tropical agriculture (Shelton 1998). In Myanmar, leucaena is used as a protein source in urea-molasses multi-nutrient blocks for ruminants (Ni Ni Maw et al. 2004). However, the use of leucaena as ruminant feed is not without problems, because it contains mimosine, a toxic anti-nutritional factor limiting its use as animal feed. Jones (1981) reported the absence of toxicity when leucaena was fed to goats and cattle in Hawaii and Indonesia. According to the low dihydroxypyridine (DHP) in urine of those animals, it was assumed that they could degrade mimosine and DHP. Hawaiian goats, but not Australian goats, could degrade 3,4-DHP ruminally (Jones and Megarrity1983). Inoculation of susceptible animals with rumen liquor containing mimosinedegrading bacteria protected against DHP toxicity in ruminants (Jones and Lowry 1984). For maintaining mimosine-degrading bacteria, the donor animals should be fed on leucaena continuously and it is expensive to maintain their veterinary care. Hence, we tried to develop mimosine-degrading ruminal bacteria using a fermenter, intending to produce a source of inoculum for the routine control of leucaena toxicosis in ruminants.