It’s more important than ever to chop silage corn at the right maturity, the right particle length and to make sure kernels are crushed, say two Midwestern dairy scientists.

With less alfalfa available for a variety of reasons, producers need to make the most of what they have. For many, that means that the corn silage portion of their rations will increase, predicts Randy Shaver, University of Wisconsin (UW) Extension specialist.

“For those of you who know you are going to be feeding corn silage or high-moisture shelled corn within two weeks (of harvest), you don’t want to let it get too dry. Don’t let the kernels get too hard and don’t do a poor job of processing those kernels.”

Only about one-third of farms chop silage at the right particle length with the kernels sufficiently processed, estimates University of Illinois’ Mike Hutjens. “Some labs would say that number might even be a bit generous at a third. That it’s maybe closer to 15-20% who get it right.”

A theoretical length of cut of ½-¾” – or up to 19 mm – is the traditional recommendation for conventionally processed corn silage. But Shaver suggests up to an inch in length for those who may be feeding diets with 70-80% corn silage.

“If you can chop a little longer and still do a good job of kernel processing, it’s pretty important from the standpoint of effective fiber to go along with starch digestibility.”

To ensure good kernel processing, the roll gap spacing should be between 1 and 3 mm. Whole kernels passing undigested through cows could mean a loss in milk production of up to 4 lbs/cow/day, Shaver adds.



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Hutjens recommends using the Penn State Forage Particle Separator to check particle length and how well the corn is crushed. It should result in about 10-15% of forage particle dry matter in the top box with no or few whole kernels.

“To be well-processed,” Shaver adds, “you’d like to see at least 95% of those kernels broken apart. If you see whole kernels, more than 5%, and if you find pieces of cob greater than an eighth of the cob diameter, then you just don’t have those rolls set tight enough.”

He also advocates a UW in-field test of scooping a few handfuls of chopped corn and dumping them in water. After removing floating stover, one can observe the degree of broken kernels settling to the bottom. For details, download “Making Sure Your Kernel Processor Is Doing Its Job."

An in-field test from DuPont Pioneer makes use of a 32-oz beverage cup filled with chopped corn and emptied on a flat surface. If more than two or three half and whole kernels show up, the kernel processor should be adjusted. See “Monitor Processing During Silage Harvest."

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