The objective of this study was to investigate the
effects of feeding alfalfa baleage with different concentrations
of nonstructural carbohydrates (NSC)
supplemented with a common corn-based concentrate
on performance, ruminal fermentation profile, N utilization,
and omasal flow of nutrients in dairy cows
during early lactation. Ten multiparous (8 ruminally
cannulated) and 8 primiparous Holstein cows were randomly
assigned to treatments (high- or low-NSC diet)
in a crossover design. The difference in NSC concentration
between the 2 alfalfa baleages fed from d 14 to 21
averaged 14 g of NSC/kg of dry matter (DM). Forages
and concentrate were offered in separate meals with
forages fed once and concentrate offered 3 times daily.
Except for the molar proportion of valerate, which was
lowest in cows fed the high-NSC diet, no other changes
in ruminal fermentation were observed. Omasal flows
of most nitrogenous fractions, including bacterial
nonammonia N and AA, were not affected by treatments.
Apparent ruminal digestibilities of neutral and
acid detergent fiber and N were lowest, whereas that of
total ethanol-soluble carbohydrates was highest when
feeding the high-NSC diet. Postruminal digestibilities
of DM, organic matter, fiber, and N were highest in
cows fed the high-NSC diet, resulting in no difference
in total-tract digestibilities. Total-tract digestibility of
total ethanol-soluble carbohydrates was highest in cows
fed the high-NSC diet, but that of starch did not differ
across treatments. Although milk yield and total DM
intake did not differ between treatments, yields of milk
fat and 4% fat-corrected milk decreased significantly in
cows fed the high-NSC diet. Milk concentration of urea
N was lowest, and that of ruminal NH3-N highest,