Jan explores your top five questions about corn silage and TMR feeding. Find out the best time to cut your corn for best milk production and optimal herd health.

1. The 5 Most Common
Questions About Corn Silage

2. The 5 Most Common Questions About Corn Silage

3. The 5 Most Common Questions About Corn Silage
1. At What Stage Should We Chop?
Kernel milkline has traditionally been used as
an indicator of when to harvest corn for
silage.
The best milk production results when corn is
chopped at around the one-half milk line
stage of maturity.

4. 1. At What Stage Should We Chop?
Harvest at 35% Dry Matter

5. 1. At What Stage Should We Chop?
It now appears that the best use of milkline is
as an indicator of when to start checking
whole-plant moisture.
When most of the kernels are dented and the
milkline is visible, it is time to chop some
corn to measure moisture content.
Actual whole-plant moisture should be your
trigger for when to start chopping.

6. 2. At What Moisture Should We Harvest?
Determining the moisture content of corn
silage is essential in making the decision to
when to harvest.
Both the microwave oven and Koster tester
methods are acceptable; however, I prefer
the Koster tester, as it is easier and safer.
Alternatively, the “grab test” to determine the
DM content of forages can be used.

7. 2. At What Moisture Should We Harvest?

8. “Grab Test” to Determine the DM
Content of Forages
Description of Forage Ball Approximate DM Content
Holds its shape but has Less than 25%
considerable free juice
Holds its shape, hand is moist but 25-30%
there is little free juice
Expands slowly, with no 30-40%
free juice
Springs out and falls apart rapidly More than 40%

9. 2. At What Moisture Should We Harvest?
Cows will milk best on corn silage at 65 to 70%
whole-plant moisture.
This range in moisture also works well for
achieving good preservation in horizontal
silos.

10. 2. At What Moisture Should We Harvest?
Harvesting whole-plant corn with more than
70% moisture increases seepage losses and
creates more acidity which can lower dry
matter intake, and reduces dry matter yield
per acre.
If corn silage that is chopped at less than 60%
moisture it will need to be either chopped
fine or processed to minimize losses in
starch digestion and milk production.

11. 2. At What Moisture Should We Harvest?

12. 3. At What Length Should We Chop?
The general recommendation for corn silage
harvested with a conventional harvester (i.e.
without a processor) is 3/8-inch (9.5 mm)
theoretical length cut (TCL).
This recommendation may vary between ¼-
inch (6.35 mm) and ½ inch (12.7 mm) TCL,
depending upon whole-plant and kernel
moisture, hybrid, and forage harvester.

13. 3. At What Length Should We Chop?
Evaluate % coarse particles and degree of
kernel and cob processing to determine the
proper TCL setting for your chopper.
Corn silage that is harvested past one-half
milkline stage of maturity or with less than
65% whole-plant moisture may need to be
chopped at ¼-inch TCL.

14. 3. At What Length Should We Chop?
It may be possible to chop corn silage that is harvested
at an immature or wet stage and hybrids that exhibit
soft kernel texture at ½ (12.7 mm) TCL.
The recommended chop length for corn silage
harvested with a harvester fitted with a processor is
3/4-inch (19.1 mm) TCL.
Processed corn silage that is harvested at black-layer
or with about 60% whole-plant moisture may need to
be chopped at ½-inch (12.7 mm) TCL.

15. 4. How Can We Tell if the Crop Processor is Set
Properly?
Mechanical processing of whole plant corn has been
an accepted method to improve the quality of corn
silage.
Whole plant processing crushes the entire plant
through rollers and can be accomplished in the field
during harvesting, at the silo but prior to storage, or
after ensiling and just prior to feeding.
Processing corn silage improves starch and fiber
digestion and allows for good packing in silos even
with a longer length of particle chop.

16. 4. How Can We Tell if the Crop Processor is Set
Properly?
The recommended roll clearance ranges from 1/16 to
1/8 inch (1 to 3 millimeters) (or follow manufacturer’s
guidelines for specific machines).
Care should be taken to monitor the effectiveness of
the processing.
When large amounts of acreage require harvesting,
there may be a tendency to open the rollers more
than what is recommended in order to speed up the
harvest and to reduce wear on equipment.

17. 4. How Can We Tell if the Crop Processor is Set
Properly?
You can determine clearance using feeler
gauges.
If you do not have feeler gauges, lay the blade
of your pocketknife flat between the rolls and
adjust the clearance until the rolls tighten
against the blade.

18. 4. How Can We Tell if the Crop Processor is Set
Properly?
Chop some corn, shake out the material using a shaker
box, and visually inspect each screen for degree of
kernel and cob processing.
We like to see all kernels broken (adequate processing is
occurring if more than 90-95% of the kernels are crushed or
cracked) . Pieces of cob, if discernible, should be no
larger than the end of your little finger.

19. 4. How Can We Tell if the Crop Processor is Set
Properly?
If kernel and cob breakage is not complete, tighten the
rolls until kernel damage is complete, or consider
reducing your TLC.
This may be necessary for processed corn silage that
is harvested at black-layer maturity or with less than
60% whole-plant moisture.
Improvements in milk production appear to be about 1
kg/h/day.

20. 4. How Can We Tell if the Crop Processor is Set
Properly?
A common observation by producers switching to
processed corn silage is the reduction in cobs in the
feed bunk and a reduction in kernels in the manure.
Caution should be taken when switching cows from
non-processed corn silage to processed corn silage.
With processed corn silage harvested at an immature
or wet stage that tends to mush, you can set roll
clearance to 1/8 inch (3 millimeters).

21. 5. At What Height Should We Chop?
Silage dry matter yield is reduced about 15%
as the chopper head is raised from 6 to 18
inches (15 cm to 46 cm).
But estimated milk produced per ton of silage
goes up because the more fibrous and less
digestible portion of the plant material is left
in the field.

22. 5. At What Height Should We Chop?
Switching to 18 inches (46 cm) of stubble from
6 results in estimated milk per acre being
reduced only about 3%.
Determine your needs for tonnage vs. quality
to determine the best cutting height.

23. Bottom Line
Harvesting corn at the right moisture and
particle size is crucial.
Plant moisture, rather than kernel milkline,
should determine when you start to chop.
Watch particle size and kernel and cob
breakage to make sure the processor is
doing its job.
Use additives properly, pack well and cover
securely to minimize storage losses.

24. Bottom Line