The net gain of long-chain fatty acids between
the mouth and the proximal duodenum with
the control diet (17.3%) confirmed previous
results in dairy cows fed dry forage and concentrate
in similar proportions (44 to 89% (4), 17%
(25). Increased fatty acid flow in the stomachs
(+ 3.3 g/kg DM intake/d) mainly corresponded
to net microbial synthesis in the rumen, as 78%
of additional fatty acids were or might be synthesized
by rumen bacteria (branched-chain
acids: 53%; odd-chain acids: 13%; C16 acids:
10%) and only 18% was due to C18 acids, which
were not apparently synthesized by rumen bacteria
(23).