A2B-Lancaster Fanning, Saturday, December 15,2001
Penn State Cooperative Extension
Capitol Region Dairy Team
CORN SILAGE
LESSONS LEARNED
Tim Beck
Capitol Region Extension
Dairy Program Coordinator
Feedout results have been
analyzed on most of the samples
included in this year’s Capitol
Region corn silage initiative, and
several important silage manage
ment concepts were well-demon
strated.
Perhaps the most fundamental
concept clearly shown was the
importance of ensiling at appro
priate dry matter to achieve high
quality silage with high-energy
value. A second concept also re
lated to dry matter is its effect on
the fermentation end-products
produced in a silage sample. A
third lesson is the differences in
NDF digestibility that exist be
tween corn silage hybrids and the
effect this has on the potential
energy value of the silage. Each
of these issues will be discussed in
more detail.
Producers must keep in mind
the optimum dry matter for ensil
ing based on the storage struc
ture, but ensiling com silage out
side the 30-39 percent optimum
range can have clearly negative
effects on silage quality. As ker
nel development advances, more
starch is deposited in the ear, so
sugar content declines while
starch content increases. Silages
ensiled below 30 percent dry mat
ter in the study had 18.7 percent
starch on average, while the opti
mum dry matter forages had 27
percent starch content.
But it’s easy to miss optimum
dry matter and risk undesirable
silage fermentation without gain
ing significant energy value. The
samples ensiled above 39 percent
dry matter had slightly higher
starch values at 30.5 percent, but
milk per ton and net energy of
lactation (NEL) were not signifi
cantly improved over the samples
ensiled at optimum 30-39 percent
dry matter. What was clear is
these overly diy samples did not
ferment as effectively as shown
by a higher terminal pH, less ti
tratable acidity in the sample,
and lower levels of total volatile
fatty acid (VFA).
It should be noted processing
might improve the energy value
of overly dry silages. The effect of
Corn Silage Initiative: Comparison of feed out sample results grouped by dry
matter
Dry Matter, %
Net Energy Lactation, mcal/lb
NDF, % DM
Starch, % DM
Sugar, % DM
48 Hr IVNDFD, %
Milk Per Ton, Ibs/Ton
pH
Titratable acidity, meq/gm
Lactic acid, % DM
Acetic acid, % DM
Total VFA, % DM
Ammonia % CP
DAIRY
Tim Beck
processing is already considered
in the Milk2ooo calculation since
different equations are used to
calculate the predicted starch di
gestibility for processed vs. un
processed com silages.
For silage to be well-preserved
and have good feed bunk stabili
ty, we need to achieve a good ter
minal pH between 3.5-4.0 that re
sults in a high concentration of
lactic acid compared to the other
volatile fatty adds in the sample.
Again, dry matter at ensiling is
critically important. When si
lages are ensiled too wet, fermen
tation may be prolonged with ex
cessive acetic acid and total
volatile fatty acid production.
While this improves the bunk
life of the silage because acetic
acid prevents the growth of
yeasts and molds in the bunk, it
can also deplete the energy and
protein content of the silage.
Samples ensiled below 30 percent
dry matter had higher acid pro
duction, more acetic acid, total
VFA production, and higher am
monia levels. Ammonia decreases
dry matter intake of silages sig
nificantly, as does acetic acid,
and its presence indicates protein
degradation has occurred during
the prolonged fermentation that
occurred.
Drier silages do not produce as
much total acid during fermenta
tion because packing is more dif
ficult and sugar levels are lower
in the crop. This was evident in
the study samples, although all
samples are within acceptable
levels of lactic and acetic acid
production.
Average 27.9 Average 34.7 Average 42.5
25.9—29.9 31.7—38.9 40.1—43.8
68
51.72
18.68
3.46
61.29
Milk 2000 Calculations
3163
Fermentation Characteristics
3.71 3.82
8.86 4.78
6.38 4.40
2.65 .68
9.11 5.11
8.41 6.41
Ensiling practices are like all
management practices we
must strive for a balanced ap
proach that optimizes as many
desirable outcomes as possible.
We need some acetic acid to have
stable feeding characteristics, but
prolonged fermentation depletes
silage energy value and reduces
dry matter intake.
Finally, the com silage project
clearly demonstrated the differ
ence NDF digestibility could
make on the energy value of com
silage. In the traditional ap
proach to calculate net energy of
lactation, neutral detergent fiber
and acid detergent fiber values
are used to calculate energy
value. This method does not ac
count for the differences that
plant variety, growing conditions,
and stage of maturity can create
in the final energy value of com
silage.
We calculated the Milk2ooo
value of silages in the study and
found that when looking at the
neutral detergent fiber values of
samples that were nearly identi
cal, final Milk2ooo values that
use NDF digestibility in the cal
culation could differ by as much
as 500-600 pounds of milk per
ton of silage. This was especially
true for silages that were ensiled
too dry.
Traditional energy calculations
alone did not adequately distin
guish the energy value differ
ences that existed between these
silages. In one case, NEL for the
silage was .73 by traditional
methods, but the recalculated
Schwab-Shaver NEL was .68 for
the same sample when digestibili
ty was considered. This differ
ence would greatly influence the
supplementation required to
achieve similar milk production
from this forage. It is important
to note the Milk2ooo calculation
reflects both increased energy
from improved digestibility and
higher milk production potential,
from improved intake because
the cow is able to consume more
dry matter because NDF is not
holding back intake.
To summarize, remember the
major influence dry matter at en
siling has on final silage quality.
This is a controllable variable
that can be monitored and will
result in consistently higher qual
ity forages when properly man
aged. Second, when the dairy ra
tion is not producing as much
milk as anticipated, consider re
questing some additional testing
and recalculate the energy value
of the com silage using the
Milk2ooo approach. You may
discover you’ve seriously overes
timated your corn silage energy
value and a new formulation of
the ration may be needed.
More information about his
topic may be found at the corn si
lage link at the Capitol Region
Dairy Team Website at http://
capitaldairy.cas.psu.edu or at the
Wisconsin Website http://
www.uwex.edu/ces/crops/
uwforage/Siiage.htm.
.72
46.08
27.09
3.48
60.00
3335
Drought Of ’99 Never Ended
In Parts of Pennsylvania
UNIVERSITY PARK (Centre
Co.) Groundwater supplies
under much of Pennsylvania that
dwindled to alarmingly low levels
during the drought of 1999 never His biggest concern over the
fully recovered and have fallen next few months is for people
again during this year’s extreme- who depend on wells and springs,
ly dry weather, according to a “We are not getting the fall rains,
water resources extension special- we need and file groundwater,
ist in Penn State's College of Ag- levels continue to drop,” he said,
ricultural Sciences. “Wells are starting to go dry.”
If central Pennsylvania does According to Swistock, there
not receive at , least normal of opportunity'
amounts of precipitation m Jate daring the year for recharging
fall and winter, said Bryan Swis- groundwater, spring and fall. The
tock, the region will face a cnhcal fal , wtadow now dosing . In the ,
situation with groundwater sup- when the p Qund is frozen s
plies come spring. and most precipitation falls as'
Fifty-five Pennsylvania coun- snoWj and i„ the
summer when
ties are under either a drought trees and other plants pre absotb .
watch or drought warning issued ing huge amounts of water,
by the Pennsylvania Department groundwater normally doesn’t re
ar Environmental Protection. Dry charge
condition are most severe in the » Wc * have tended in the last 10
southcentral part of the state. to 15 t 0 have short . term ,
if**" Z * y droughts -we had them
the Nahonal Weather Service are fa >gB >9l thfmid.-pOs and >99.”
calling for no more than normal Swistock . «T ha t’s differ e„t
amounts of precipitation this in the 1930 s and 1960 s
" , when we had much longer-term
“Bu we were suppose! o get dro ughts. We had six or seven
nomrt amounts of precipitation years hi a r ow of well-below-nor
this fall, too and we haven t.’ mal rainfail That>s abi
Swistock said If this keeps up fecauseifwe ever get into
late fall and winter, we a that now our
will be in trouble. Public surface A
water supplies have mostly held
up rather well so far, but there *V* Tr?. 8 ' .. ,
are already problems with Swistock believes development
groundwater in places. Because growing population, espe
we can’t see groundwater, the ** southeastern part of
public is mostly unaware.” Pennsylvania, are putting in-
Effects of the drought of 1999 ***** °P
were felt all over the itote. but it J mor * ““P*
was worst in the parched east this state for water every
“In the eastern part of the ** development.” he says,
state —by any measure you care P utt * n B mor( ; P ressure
to use - the summer drought of on ** *** resources.”
1999 was as bad as they get,” Groundwater mining taking
Swistock said. “But ironically, in groundwater than the sys
the fall of that year, the eastern tem can replenish —is happening
part of the state received so much like Arizona and Cali
rain that there were flooding fornia, threatening long-term
problems and the groundwater communities. In water-rich Penn
recovered. Here in central Penn- sylvania, it is uncommon,
sylvanla, however, where rains “But in the southeastern part
were not nearly so heavy or frc- of our state, groundwater mining
quent, the groundwater never is occurring and they have
completely recharged.” started to document continually
The worst-case scenario, warns declining groundwater levels,”
Swistock, would be if we had a says Swistock. “A groundwater
cold, dry winter, which would protection area has been estab
freeze the ground surface and not fished. Our grpundwater supplies
allow any recharging of the are not unlimited. In central
groundwater. “If that hap- Pennsylvania, we should hope for
.73
44.47
30.50
2.53
61.00
3299
3.98
3.11
3.97
.38
4.34
5.33
Groundwater Levels Still Suffer
ter levels would continue to de
cline as they ‘have all summer
and they would reach critical lev
els come spring.”