Rory Lewandowski,
Extension Educator Wayne County
Corn silage has the reputation as a
reliable and economic feedstuff. Corn
silage is widely used in ruminant livestock rations, particularly with cattle,
but I have also seen it used with sheep as well. A good thought to keep in mind is that the
quality of the corn silage you produce this fall will affect your livestock for
many months in to the future. Producing
high quality silage depends upon good management practices at several different
steps.
Corn silage
is a fermented product. To be effective
that fermentation must take place in an anaerobic (no oxygen) environment. The goal in this fermentation process is to achieve
a pH of less than 4.0. This can be
accomplished when air is removed as quickly as possible after chopping so that
high concentrations of organic acids, predominantly lactic acid, are rapidly
produced. This may sound simple, but
implementation depends upon good decisions, harvest preparation, and some
cooperation from Mother Nature.
The first
and most critical step is that corn must be chopped at the right moisture or
dry matter (DM) content. If you don’t
get this right, nothing else will matter. A DM range of 30-38% is acceptable. Silage put into a bunker silo should be at
the lower end of this range while silage put into upright silos should be at
the upper end. Corn less than 27 to 30%
DM does not ferment properly. It
produces silage that often has high concentrations of butyric acid and can have
a very low pH. This silage will have an
unpleasant odor and animal DM intake will be reduced. Corn chopped at higher than 40% DM does not
pack well. As a result it usually does
not ferment adequately, resulting in low acid concentrations, heat damage and
moldy silage. Starch digestibility is
usually low, causing the silage to have less energy. Silage harvest needs to start on the wetter
end of the acceptable range because corn will gain DM content or lose moisture
at a rate of between 0.5 to 1.0 percentage points per day. Rapid harvest is important to ensure that
corn is chopped within the acceptable moisture range.
Chop length
is a consideration for silage packing, feeding and animal performance. A
three-eighths inch (3/8) theoretical length of cut (TLC) is recommended for
corn at 32 to 36% DM. When DM is under
32%, a three-quarters (3/4) inch TLC is recommended and when DM content is
above 36%, a TLC of less than 3/8 inch is recommended. There is a reason that this is termed
“theoretical”. The actual cut length in
the field can vary so operators should look at the actual chopped forage and
make adjustments to get the correct chop length. One practice that can change these
recommendations is kernel processing.
Kernel processing involves fracturing the corn kernels as the corn plant
is chopped. Research results have
consistently shown benefits in animal performance when kernels are processed
adequately. The goal is to crack 90 to
95% of the kernels and 70% of those should be fractured to smaller than
one-quarter of a kernel. When kernel
processing is a part of the chopping process then TLC is typically increased to
three-quarters of an inch.
One
question that often comes up in any silage production discussion is whether or
not to use a silage inoculant. There are
2 main types of inoculants; homofermenters and heterofermenters. Homofermenters contain Lactobacillus bacteria that produce lactic acid and
heterofermenters contain Lactobacillus
buchneri that produce lactic and acetic acid. The lactic acid promoting inoculants are used
to increase silage quality by driving the silage pH down quickly and reducing
DM loss during the fermentation process.
Dry matter loss during fermentation is higher with the buchneri type
inoculants but feed out losses can be reduced.
The buchneri inoculants are used to increase the aerobic stability of
silage during feed out. The acetic acid
produced prevents yeast growth. Bill
Weiss, OSU dairy nutritionist located at the OARDC in Wooster says that his
standard recommendation regarding inoculant choice is that if you have
historically had problems with moldy silage during feed out or if the TMR
ration gets hot in the bunk, then use the buchneri type. If neither of these is an issue, then use the
lactic acid promoting type of inoculant.
Regardless of which inoculant type is used, the key is to purchase high
quality inoculants and to apply them correctly.
After DM
content, the next critical step is the rapid removal of air by packing. As layers of forage are added to the silo or
pile, they need to be driven over multiple times by heavy machinery. The goal is to achieve a silage density of 15
lbs. of DM/ft3 or higher. The
density is directly correlated with oxygen exclusion within the silage pack and
generally high silage density results in lower DM losses. The guideline for packing is that 800 pounds
of packing weight is needed for each ton of silage delivered to the silo or
pack. For example, if the harvest rate
is 50 tons/hr. then the packing weight needed is 50 x 800 = 40,000 lbs. or 20
tons. In addition to the packing weight,
the thickness of the layer packed should be monitored. The optimum condition is to pack layers of 6
inches or less. Another piece of advice
from Bill Weiss regarding packing is: If you think you have packed enough; pack
some more.
The final
important step is covering the bunker or silage pile. This should be done as soon as the bunker is
filled and the final packing had been done.
Covering prevents oxygen, weather and animals from getting into the
silage pack. Covering reduces DM and
spoilage losses. The recommendation is
to cover with plastic of 6 to 8 mil thickness and weigh that plastic down,
sealing the edges as well. University
research trials have demonstrated that the oxygen barrier 2-step products have
reduced losses more than covering with the 6 to 8 mil plastic.
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