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Corn silage, feeding management, cash-flow effects

Virginia Ishler, Rob Goodling Jr., Timothy Beck and Heather Weeks for Progressive Dairyman Published on 05 February 2016
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Editor’s note: This is the first part of a three-part series. To read the second part of this three-part series, go to (Corn silage, feeding management and economic effects).

When discussing dairy cow diets, corn silage is widely considered the more consistent forage compared to alfalfa or grass silages.



Consultants and producers presume that corn silage quality will vary little over the course of a year from harvest through feeding. The Penn State Extension Dairy Team worked with more than 50 farms the last three years to test this assumption and how best management practices for cropping and feeding affect cash surplus.

With the severe market volatility farms across Pennsylvania and the U.S. have faced in recent years, gaining a better understanding of how forage quality impacts a dairy farm’s breakeven is important.

This is Part 1 of a three-part series highlighting the lessons learned and will focus on forage quality, especially practices related to corn silage management. Parts 2 and 3 of the series will delve into dairy production effects and the economic implications of these best management practices.

Dairy farms in the Northeast often produce the majority of the forage crops needed for their operations. Depending on their land base, some dairies produce corn grain and soybeans to offset purchased feed costs.

Corn silage is the predominant forage harvested and fed to lactating cows. The 2014 State Agricultural Overview for Pennsylvania shows 410,000 acres were planted for corn silage, producing 8.2 million tons, compared to haylage grown on 450,000 acres, producing 2.8 million tons.


Assuming these farms are on limited land base, producing and feeding forage of consistent quality and quantity is paramount. High-corn silage rations have been prominent in the hundreds of herds the extension dairy team has worked with in evaluating cash-flow plans or income over feed cost analyses for the past five years.

In the last three years, more than 60 farms participated in a research project that involved collecting information on cropping and feeding management practices and completing a cash-flow statement for the respective years. However, over the time period, some farms did drop out, while others were added.

Results from the Penn State Extension Dairy Team’s project for 2013-2015 show opportunities exist to improve decision-making on seed hybrid selection and cropping practices. Both quantity and quality of home-raised forage heavily influence animal performance and cash surplus. The results from this project are applicable to farms of all sizes.

For the 2013 harvest year, Pennsylvania had a very favorable growing season with ample rainfall. Producers harvested large quantities of corn silage. However, the extreme height of the plants impacted quality, especially neutral detergent fiber digestibility (NDFD-30 hour). Farms were grouped based on their fiber digestibility.

The operations with the lowest NDFD-30 (47 percent of NDF average) corn silage fed the highest amount on a dry matter basis, utilized the most small-grain silage and adjusted rations to achieve the highest cash surplus per cow.

Farms with the highest fiber digestibility silage (58 percent of NDF average) had the lowest cash surplus per cow. They fed the lowest rate of corn silage and were the heaviest alfalfa silage feeders. This result runs counter to controlled research trials or popular press articles suggesting highly digestible corn silage is the main requirement to achieve a positive milk production response.


However, this initial observation is only one piece of the puzzle and may not reflect the big picture. The key element missing in many studies is the impact cropping and feeding practices have on financial performance.

The nutritionists working with lower-digestibility corn silage compensated appropriately and maintained a higher feeding rate, providing ample energy to the cows. These producers experienced the highest cash surplus but have the opportunity to gain even more financial success with higher fiber digestibility.

While the lowest cash surplus herds harvested high-quality forage, either because of limited resources (land base or poor yields) or unfamiliarity with the higher corn silage feeding system, they did not feed higher corn silage rations. Based on the farms in this project, operations that fed more than 18 pounds of corn silage dry matter and incorporated small-grain silage into their feeding programs appeared to show a financial advantage.

Fiber digestibility alone is not the only measure to consider when assessing corn silage quality. The starch level and variation in starch digestibility heavily influence how animals perform and can affect purchased grain requirements. Over two years of sampling, the starch on a dry matter basis in corn silage ranged from 20 to 44 percent.

The low-starch silage required additional cereal grains or concentrates to compensate for the low energy value. The higher-starch corn silage allowed a heavier forage feeding level and required less purchased grain.

Work at the University of Wisconsin on vitreousness of starch in corn has highlighted the differences among corn silage hybrids. One of the objectives of the project was to evaluate starch digestibility over time on the participating Pennsylvania farms. Corn silage was sampled in the fall and spring and tested for seven-hour starch digestibility by Cumberland Valley Analytical Lab. The expected result was an increase in starch digestibility over time.

In the first year of the project, the starch digestibility changes were: thirty-three percent remained the same from fall to spring, 40 percent increased, and 26 percent decreased. One possible reason for this unexpected discrepancy compared to controlled research was the number of corn hybrids used on the farms – ranging from five to 13 on a single farm.

The majority of the hybrids planted did not have quality parameter data available. This unpredicted variation in corn silage quality would require the nutritionist to closely monitor forage quality and make appropriate adjustments to maintain animal performance. Failure to make timely adjustments could have negative implications on the farm’s profitability.

Year two of the project captured greater detail on the hybrids and storage structures. Initial analyses indicated farms with the same single hybrid and same structure saw the expected increase in starch digestibility from fall to spring (Table 1).

7-hour starch digestibility

Farms with blended samples of more than one hybrid in the same structure had less of an increase and some decrease in starch digestibility. Finally, farms that changed hybrid and/or structure had a more varied change in starch digestibility.

Farms in Group 1 had higher changes in starch digestibility compared to farms in either Groups 2 or 3 combined. These results indicate the benefits from more highly digestible hybrids can be lost when hybrids are mixed in the storage structure.

Based on these observations, dairy producers and nutritionists should carefully consider the impact unexpected corn silage quality variations or inability to identify the hybrid in the storage structure can have on animal performance and farm profitability. In the next article, we will look at how dairy production practices used on the farms impacted their productivity.  PD

Rob Goodling, Jr., Timothy Beck and Heather Weeks are also with the Penn State Extension Dairy Team.

Virginia Ishler
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