Some farmers question what fermentation can do in term of starch digestibility. One thing we do know is that the longer silage stays in the silo, the more starch is available for the cows.
“During curing in the silo, silage is able to break down those prolamin proteins which make starch more easily digested,” said Luiz Ferraretto, assistant professor at the Department of Animal Sciences, University of Florida. “Fermentation increases starch digestibility under various scenarios and conditions so it was also suggested as a tool to solve other issues, for example, late maturity at harvest or different hybrid types.”
Keeping silage in the silo longer may help a little bit, but maturity is really the key when harvesting good-quality corn silage.
“At the end of the day, kernel processing is more likely to help solve the issue of lower starch digestibility in late maturity corn silage than longer storage,” he said.
The benefit of kernel processing is that the more you break the kernel, the more exposed the starch is. Corn grain is a seed, so it's very hard. The outside casing is called the pericarp, and it is designed to protect the starch from being digested or from anything else that might try to break it open.
“The pericarp is really designed to inhibit digestion, so your goal should always be to break as many kernels as possible, and break it up as much as you can to expose as much of the starch as possible,” he said. “Because that makes it easier for ruminal bacteria to reach starch granules. Increasing surface area exposure of the corn kernel will increase the starch digestibility.”
Breaking Up Kernels
There are two ways to break down the kernels. First, to reduce the theoretical length of cut, place the knives very close to each other to increase the probability of hitting the kernels. However, decreasing too much of the theoretical length of cut can leave you without enough of the effective fiber, which is provided by coarse particles.
The second option, and what Ferraretto believes is the best option, is to use a kernel processor regardless of the type of processor you prefer and to make sure it’s set very tight.
“Normally with conventional processors, we would recommend 1 to 3 mm distance between the rolls. They usually work very well, but even though you regulate the harvester properly, you should also make sure you analyze samples over and over during harvest because even regulated rolls start getting further apart during the harvest due to all the material passing through,” he said.
It’s important to make sure the kernels are being broken up. To ensure adequate breakage is occurring, you’ll want to stop, pull a sample, run a quick test and then regulate the machine accordingly. For an instructional sheet showing how to test kernel processing, click here.
“If you don't test during harvest, you’ll have all year to think about it and fix it for next year,” he said. “Kernel processing is something to figure out real-time; otherwise you will pay the price for it the entire year. It’s absolutely critical to make sure you break the kernels.”