Yeast is particularly useful in high-producing ruminants whose digestive micro-
bial balance can be altered by high-dietary energy input.
Active dried yeast can survive and remain metabolically
active in the gut (Kung et al., 1997), and therefore it can
exert probiotic effects by interacting with the autochtho-
nous microbial species responsible for enhancing feed
digestion. Until now, the most consistent positive effects
of ADY have been reported for ruminal microbial ac-
tivity in young ruminants, stabilizing ruminal pH, and
preventing subacute ruminal acidosis (SARA) as well as
stimulating growth and activity of fiber-degrading bac-
teria (Chaucheyras-Durand et al., 2008).