Chopped corn should be processed aggressively, and dairy producers should monitor it throughout the harvest to make sure that’s happening, recommends Bill Mahanna, Pioneer Hi-Bred’s nutritional sciences manager. Speaking at Pioneer’s Forage Media Day in Johnston, IA, last week, Mahanna pointed out that adequate kernel processing improves starch availability, minimizing the number of kernels that pass through the rumen undigested.

“It doesn’t do our producers any good to buy high-end (corn) genetics if the cows can’t get access to all the starch,” said Mahanna.

Simply nicking the kernels may have been sufficient 10 years ago, but not anymore, he said. Today’s cows produce more milk and have higher dry matter intakes, so feeds pass through the rumen more quickly. The crop processor on the chopper should break kernels into small pieces, said Mahanna, citing the small grain particles in the concentrate portion of dairy rations as evidence of the need for more-thorough silage processing.

“Why process dry or high-moisture grain so aggressively while at the same time accepting lots of big kernel pieces in the silage?” he asked.

A lab test can measure how well silage has been processed after it’s in the bunker. Developed by Pioneer; the U.S. Dairy Forage Research Center, Madison, WI; and Dairyland Laboratories, Arcadia, WI, the test involves shaking dried silage over a series of sieves. When 70% or more of the starch passes through a 4.75-mm sieve, equal to about a quarter of a kernel, the silage is processed optimally. If 50-70% pass through, the processing is considered average, and a kernel processing score below 50% is inadequate.

The test is available from Dairyland Labs and Cumberland Valley Analytical Services, Hagerstown, MD. But Pioneer developed a simpler field test. It somewhat mimics the lab test and can be used during harvest, when adjustments can still be made. The company’s Kernel Processing Cup is available from Pioneer sales reps, or any 32-oz beverage cup from a convenience store will work. Fill the cup with chopped corn, empty it on a flat surface, and count the number of half and whole kernels.

“We don’t want to see more than two or three of those in this volume of silage. If you do see more than that, when you send it in for a lab test afterwards, you’re not going to be happy.”

He suggested having someone check two loads per hour as they arrive at the bunker. If necessary, examine your processor and make adjustments, or ask your custom harvester to do the same. Check for excessive roller mill wear, the gap between rollers and the roller differential. A 1- to 3-mm roller clearance and 20-30% differential are recommended starting points that can be modified based on periodic physical observation of the silage.

All choppers do a better job of processing at shorter chop lengths, so keep the theoretical length of chop at ¾” (19 mm) or less.

“If you aren’t in desperate need of effective fiber from the corn silage, dropping back from 19-mm to 17-mm length of cut will make a world of difference in how well that roller mill works,” said Mahanna.