From heifers to lactating cows, corn silage is a major component of most dairy rations and also an excellent supplemental feed for beef cattle. The value of corn silage is related to its energy content. Corn silage provides energy from digestible fiber and also from the starch contained in the kernel.
However, the corn kernel has a protective layer called pericarp; this layer is very resistant and is not easily digested. In order to fully take advantage of the starch content within the grain, it is necessary to mechanically break down the pericarp to expose the inside of the kernel for digestion.
This is called kernel processing and it is done during harvest via two rollers in the silage chopper. These rollers should have a gap of 1 to 2 mm to fully crush the grain and tear the pericarp resulting in fragmentation of the corn kernel.
There are two ways to evaluate kernel processing: One is a field test during harvest that provides quick results within minutes; and the other is a laboratory test that can take a few days.
To do the field test during harvest, it is recommended to use a 32-oz. cup to take a sample of chopped material as it is being delivered to the bunker or pile. Spread this material on a clean surface and sift through it counting half and whole kernels. The ideal goal is to have less than two half or whole kernels. While having three to four whole or half kernels is still within acceptable range, it’s important to recognize that starch digestibility may not be as high as it could be. This test provides a quick reference to make adjustments in real time and tighten the rolls if more than two half or whole kernels are found.
The second test is called kernel processing score or corn silage processing score, and it is done in a laboratory by looking at the percentage of starch that passes through a 4.75-mm sieve. The test is a very good way to evaluate how well the kernels were processed and it allows for adjustments of the ration to balance it properly. Below are the interpretations of the test:
• Less than 50—inadequate;
• Between 50 and 70—normal;
• More than 70—optimum.
Increasing starch digestibility by processing corn kernels properly supports rumen bacteria and increases energy supply to the dairy cow. Harvest time is the moment to make sure that all the time and effort put into growing corn for silage is well worth it. The starch is already there, it is just a matter of making sure that it is available! — HUGO RAMIREZ
