Page 30-Corn Talk, Lancaster Farming, Saturday, October 14, 2000
WISCONSIN DAIRY
FEEDING TRIALS FOCUS
ON CORN SILAGE ISSUES
Greg Roth
Penn State Agronomy
Associate Professor
A recent report from the
University of Wisconsin has
summarized a number of in
teresting feeding trials that
have focused on some timely
corn silage feeding issues.
Wisconsin researchers have
focused on corn silage be
cause they see an increasing
trend for feeding more corn
silage to dairy cattle in the
upper Midwest. Their trials
have focused on evaluating
the effects of stage of matu
rity, crop processing and
chop length, and hybrid qual
ity on lactation performance.
In a maturity trial they
conducted, corn was har
vested at early dent, 1/4 milk
line, 2/3 milkline and black
layer for silage. These silages
ranged from 69.9 to 58.0 per-
cent moisture. As maturity
was delayed, the NDF of the
silages decreased from 52 to
41.3 percent. In this trial,
milk production was maxim
ized at the 2/3 milk line stage
when the silage was 64.9 per
cent moisture. In a second
trial, they evaluated silages at
early dent (71 percent mois
ture), half milk line (64 per
cent moisture), and black
layer (48 percent moisture).
In this trial, milk production
was highest at the early dent
stage. The researchers found
in both trials that both rumi
nal starch digestibility and
fiber digestibility were de
creased at the BL stage.
Based on the results of this
trial and agronomic trials
that have shown no yield in
crease beyond the half milk
line stage, the authors con
cluded that a target of 65 per
cent moisture seemed best
but that producers should
begin harvesting at 70 per-
cent moisture to avoid silage
drying down excessively by
the end of harvest. In a sum
mary of forage analyses con
ducted at a Wisconsin forage
testing lab, they have found
that on average corn silage
moisture contents have in
creased 4-5 percentage units
during the last decade from
58 to 63 percent, so producers
are moving away from drier
silages.
Another study focused on
processing of corn silage. Pre
vious studies have shown
milk responses of 0 to 2
pounds of milk per cow per
day. In this study, the control
corn silage (half milk line and
67 percent moisture) was
chopped at 3/8 inch TLC
without rolling using a pull
type chopper. Treatment
corn silages were harvested at
3/8 inch, 9/16 inch, and 3/4
inch TLC and rolled using
the same pull-type chopper
fitted with a crop processor.
The processor was set at a
one-millimeter roll spacing.
Silages were evaluated using
a particle size separator. The
researchers noted whole and
half cobs in the coarse frac
tions of the separator for the
unrolled silage. These are
prone to separation in the
feedbunk. Cows fed the
rolled silages on average ate
1.5 pounds more diet DM
each day than cows fed un
rolled silage. Cows fed the
rolled silages on average pro
duced 2.5 pounds more milk
fid
w
m
rn
and 3.5 more FCM each day
than cows fed unrolled silage.
Milk fat test was .10 percent
units higher on average for
cows fed the rolled silages,
possibly due to less sorting of
the cobs in the bunk.
There were no differences
among the rolled silages in
dry matter intake, milk yield,
or milk composition. Based
on this research the authors
recommend a 3/4 inch TLC
with a 1 mm roller clearance,
except on wetter silages
where the roller clearance
may be expanded to 2 to 3
mm clearance. The authors
were hesitant to recommend
longer chop lengths due to
the potential for equipment
wear and less packing in the
silo.
The authors also have eval
uated the variation in mean
particle length (MPL) and
percent coarse particles of
processed silages produced
on commercial dairies in
Wisconsin. There were large
variations in both indicators,
suggesting that commercial
operators could improve on
their chopping and rolling
practices. Also, wide ranges
in bunker silo densities were
also reported.
In another study, the re
searchers evaluated the in
situ digestibility of processed
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and unprocessed corn silage
harvested at different stage.
They conducted this trial to
evaluate whether it would be
feasible to delay harvesting
by using a crop processor.
They found that processing
corn silage harvested at black
layer could improve the
starch degradability but
could not restore it to levels
in earlier harvested silage.
Also, processing did not im
prove the digestibility of the
fiber in the corn silage, which
was reduced at the black
layer stage compared to ear
lier harvests. Thus, it does
not appear that harvesting
should be delayed when using
a processor.
The researchers also con
ducted two trials evaluating
hybrid differences. In the
first trial they compared a
conventional hybrid (Pioneer
3563) to a leafy hybrid
(Mycogen TMF 106). Hybrids
were evaluated at two plant
populations-24,000 plants
per acre or 32,000 plants per
acre. These were chopped at
3/4 inch TLC without a pro
cessor and fed in a ration that
consisted of 2/3 of the forage
from corn silage and 1/3 from
alfalfa. They observed lower
ADF digestibility and higher
starch digestibility with the
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