Check the Kernel Processor Now for Improved Digestion Later

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Dairy cows can use the starch component in corn silage more effectively when the kernels are processed at harvest — and improved starch utilization results in improved animal production.

A processor simply helps break the kernels into pieces at the time of harvest. Yet, ensuring kernels are adequately processed can be difficult when they are mixed with the stover fraction of the plant. After analyzing more than 1,000 forage samples, Cornell University found only 7 percent were optimally processed.1

To determine if processing is adequate, producers can use a simple water separation test. This test requires minimal equipment and can be done on the farm.2

  1. Fill a five-gallon bucket, or other suitable container, about half full with water.
  2. Collect two or three representative handfuls of the freshly chopped and processed crop (corn) and place it in the water. This test is not appropriate for ensiled (fermented) corn.
  3. Gently agitate the material for about one minute to help it separate.
  4. Skim the floating stover from the water.
  5. Drain the water being, careful to capture the kernels.
  6. Inspect the kernels for degree of processing.

After separation, the assessment of the degree of kernel processing is subjective.2

  • The presence of whole kernels indicates processing is insufficient.
  • Mostly nicked, cracked or broken kernels indicate processing is barely adequate.
  • Properly processed materials should have almost no whole or cracked kernels.

Following the test, producers may need to make adjustments. Kernel-processed corn should be chopped at 0.75 inches (19 mm) theoretical length of cut (TLC). The roll clearance should usually be set at 2 to 3 mm. The specific clearance depends on both the equipment and the maturity and variety of the crop. Increasingly, some producers and custom operators are setting their roll clearance to 1 to 2 mm to improve kernel processing scores (KPS), especially with hard kernel varieties and/or plants at higher dry matter (DM) levels.

Processor maintenance is critical since worn rolls can result in many unbroken kernels. If the corn is properly processed, all the kernels should be broken, nicked or damaged, and there should be no cob fragments larger than 0.25 inches.


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1 Ishler VA. Corn Silage Kernel Processing, Fact or Fiction? Penn State Extension. March 15, 2017. Accessed June 22, 2017. Available at

2 Shinners KJ and Holmes BJ. Making Sure Your Kernel Processor Is Doing Its Job. Focus on Forage. 2013;15(4). Accessed June 7, 2019. Available at



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