The invention provides a composition that enhances the proliferation activity of propionic acid bacteria in the rumen of ruminants to allow the propionic acid bacteria to sufficiently exhibit their metabolic function in the rumen for the prevention and treatment of rumen acidosis in ruminants. The invention also provides use of the composition. Viable propionic acid bacteria and a lactic acid bacteria culture are orally administered to a ruminant to dramatically (rapidly) promote the proliferation of the propionic acid bacteria in the ruminant rumen, and to thereby increase the volatile fatty acid concentration in the rumen for the prevention and/or treatment of rumen acidosis in the ruminant.
