The objective of the study was to evaluate effects of
partial substitution of dietary grain with wheat dried
distillers grains with solubles (DDGS) on dry matter
intake (DMI), sorting behavior, rumen fermentation,
apparent total-tract nutrient digestibility, plasma metabolites,
and milk production of dairy cows in early
lactation. Sixty-one Holstein cows, including 13 ruminally
cannulated cows, were blocked by parity and
calving date and assigned to 1 of 2 experimental diets
immediately after calving until 12 wk in lactation. The
control (CON) diet contained 43% barley silage, 17.3%
dry-rolled barley grain, and 39.7% concentrate mix on
a dry matter basis, and wheat DDGS replaced dryrolled
barley grain in the DDGS diet. Dietary starch
content was 29.2 and 19.1% for CON and DDGS diets,
respectively. Despite the 10-percentage-unit difference
in dietary starch content, cows fed the DDGS diet did
not increase ruminal pH. A significant treatment by
parity interaction was observed for DMI; feeding the
DDGS diet decreased DMI of multiparous cows compared
with CON (20.1 vs. 21.3 kg/d) but increased that
of primiparous cows (16.2 vs. 14.7 kg/d). Although
milk yield was not affected by treatment, cows fed the
DDGS diet had lower apparent total-tract digestibility
of starch compared with CON (81.9 vs. 91.2%) and
tended to have higher plasma concentrations of nonesterified
fatty acids (173 vs. 143 mEq/L). High-fiber
byproduct feedstuffs such as wheat DDGS can be used
as a partial substitute for grains in diets of dairy cows
in early lactation but the substitution may not mitigate
rumen acidosis problems and may decrease energy intake
of multiparous cows in early lactation.