Regardless of the components of grape marc responsible
for inhibition of enteric methanogenesis, the
causative mechanisms must involve an alteration or an
effect on ruminal fermentation, or at least an effect
on ruminal microbiota. Ruminal bacterial and archaeal
communities were shown to be altered by dietary supplementation
with grape marc, although changes observed
in the archaeal communities were related more
to the form of grape marc used. The DGM diet caused
a decrease in the pH of ruminal fluid, whereas the EGM
diet was associated with a tendency for ruminal fluid
pH to be decreased