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Cornell study looks at corn silage chopping efficiency

Slideshow: The two-year study examined factors that affect chopping efficiency.

Kara Lynn Dunn

October 26, 2020

6 Slides

Cornell Pro-Dairy researchers have issued the results of a two-year project looking at factors that affect chopping efficiency.

Chopping breaks corn kernels to release the starch that cows need for energy. Chopper efficiency is determined by shaking a dried silage sample through a 4.75-millimeter sieve (shaker box) and analyzing the portion that falls through for its starch content. The percentage that falls through is the corn silage processing score, also known as the kernel processing score (KPS).

David Mertens developed this CSPS sieving process at the USDA’s Dairy Forage Research Center in Madison, Wisc. A score of greater than 70 is an indicator of optimal feed quality; a score below 50 requires attention to the chopper.

Joe Lawrence, a Cornell Pro-Dairy forage systems specialist, led the New York Farm Viability-funded project to see how hybrid characteristics — such as ear-to-stover ratio, whole plant dry matter and ear dry matter (DM) — affect a chopper’s ability to properly process kernels.

“This project did not show that any one type of hybrid was better or worse. What it did highlight is the need to pay close attention to the hybrid type and stage of maturity at harvest to assure processing success,” Lawrence says.

“Whole-plant DM did not have a significant impact on CSPS. However, the impact of ear DM was significant,” he says. “Hybrid types can have a significant impact on ear-to-stover ratio, but the data showed that growing environment and location impact the magnitude of this difference between hybrids and could explain a 10-15 percentage unit change in CSPS.

“While whole-plant DM is the metric used to target harvest timing, higher ear DM is important as an indication of kernel maturity. Total starch content increases as the kernel matures and is relevant in how well kernels process.”

Farmers and custom harvesters should adjust or upgrade chopper components based on their hybrid of choice and localized conditions, and then adjust later in the season when the corn is drier.

CSPS and starch digestibility

The project also evaluated how corn silage processing score is affected by starch digestibility. Samples were fermented for 135 days for analysis.

“We know fermentation increases starch digestibility. That is why we recommend allowing corn silage to ferment for three to four months before feed-out,” Lawrence says. “Over the last few years, some data have suggested that CSPS also improves during fermentation. This project provided a much larger dataset to evaluate if how broken the kernels are when ensiled affects how the processing score changes during fermentation.

“The results showed that CSPS occasionally change during fermentation; however, the change was not consistent or significant. The lack of a relationship between fermentation time and changes in CSPS suggests that CSPS needs to be within target range at harvest.”

Start with a good hybrid

“Participating in this processing research played a role in our decision to plant a shorter day-length corn,” says Shawn Bossard, manager of the SUNY (State University of New York) Morrisville Dairy Complex.

The college farm grows corn on about 170 of its 500 acres to feed its 130-cow milking herd.

“Even though we won a Forage Super Bowl award with our BMR corn silage, we were frustrated with not finishing harvest until late September-early October and the weather was not allowing us to then spread manure or plant cover crops. We needed a hybrid that accommodates our high elevation and less-than-ideal growing season,” he says. “We want the best forage we can feed to our cows. The processing project provided us with a comfort level that the shorter-day corn we selected would process well and feed out well.”

The farm crew and students do the planting, but hire custom harvesting through Dairy Support Services Co. (DSSC) of Truxton, N.Y.

“Knowing how important chopping efficiency is, we wanted a service that would share our interest in harvesting quality forage,” he says. “DSSC has shredlage choppers and was willing to stop to check the processing quality and to adjust the equipment if needed.”  

This fall, the college’s seed rep used the shaker box method to check the silage before DCCS finished chopping the first field. The forage scored well, and in subsequent checking.

Scott Potter operates Dairy Support Services Co. with his brother, Dan, and his nephews, Doug and Matt. They offer custom planting, haylage, silage and high-moisture corn harvesting, and manure application in central New York state. Scott is a certified crop adviser.

The company operates two choppers, both equipped with shredlage processors. They made harvesting runs on three farms participating in the project. Doug and Matt regularly did visual checks of the chop quality and worked with farmers, nutritionists and crop planners to stop for shaker box or other testing.

“Stopping to check the quality of the chop only takes a few minutes and is worth the time to know the equipment is working properly and the chop is what the client wants for their cows,” Matt says.

Lawrence says that there several methods for screening samples in the field to make equipment adjustments on-the-fly. However, only lab testing can provide an exact score of the chopper’s efficiency.

“We like to participate in Cornell field research and frequently test equipment for brand manufacturers to see first-hand how different application and processes might advance our understanding and make our services more efficient for our client and our business,” Scott says.

Pay attention to chopper efficiency

Some of the impetus for this research was prompted by a study in 2014 by Larry Chase, Cornell University animal science professor. Chase’s research found that out of 1,131 corn silage samples, 42% were inadequately processed.

As part of this new work, Lawrence conducted a small survey of corn silage growers in the Northeast U.S. to get an industry snapshot on the use of kernel processing technology. Here are some highlights:

  • 17% of those surveyed are not using a kernel processing unit

  • 14% reported using a shredlage unit, all on self-propelled harvesters

  • 42% of processing units were an aftermarket addition to harvester

  • 90% reported adjusting roller speed differential of processing unit

  • 50% reported modifications to belt and pulley system

  • 53% tracked roller wear by acres harvested

  • 94% reported sending fermented samples at feeding for lab testing

  • 76% reported sending fresh samples for lab analysis

A series of four factsheets prepared by Lawrence and Ph.D. candidate Allison Kerwin are available at The research team continues to collect and evaluate data, including economic data, on the return-on-investment in kernel processing technology for silage management.

For more information, contact Lawrence at [email protected].

Dunn writes from her farm in Mannsville, N.Y.

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Corn Silage
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