Custom harvesters should have Penn State Forage Particle Separators, or shaker boxes, available for particle-size analyses – even if their clients don’t, suggested Mike Hutjens, University of Illinois dairy nutritionist.

“I recommend, every custom harvester should have a Penn State box,” he told forage harvesters at the U.S. Custom Harvesters Inc. annual convention. “Do you have to run it? No. Do you have to tell them what it has to be? No. But you’ll have target numbers or guidelines.”

Those shaker box numbers estimate how much physically effective fiber a cow could ingest, he added.

For corn silage chopped at ¾” theoretical length of cut, 5-15% of particles should be in the top shaker box, 40-60% in the middle box and less than 30% in the bottom.

The shaker-box method shows when there may be a problem in particle length while chopping. But will custom harvesters be willing to deal with such a problem?

“Three years ago in Iowa, a dairy farmer (using a shaker box) calls and says, ‘We’re shorter on the top two boxes.’ I said, ‘You’re right; you’re short,’ ” Hutjens said.

The farmer told his custom harvester to start chopping longer. “The custom operator said, ‘What? Take it this way or I’m going to the next farm.’

“I think next year he probably didn’t hire him back. But he had to go with that short-chopped corn silage.”