Corn Silage Management Tips

Recognize the Starch Contribution In Corn Silage

Corn silage can be thought of as grass with high-moisture corn attached to the plant. Keeping this perspective helps focus on the key traits that need to be analyzed when feeding new-crop silage. This perspective also helps focus on selecting next years' silage hybrids. As grain yield potential of newer elite corn hybrids improve, it is not surprising that silages are increasing in quantity of starch. It is not uncommon to find 35 percent starch in Midwestern corn silage samples. If the crop is high cut (e.g. 18 inches vs. traditional 6-8 inches), it is not uncommon to find starch in the low-to-mid 40 percent range. Given the variability in grain yield from both genetics and subsequent growing conditions and management, it is critical corn silage be analyzed for starch content. Nutritionist can then use tools such as the University of Wisconsin MILK2006 spreadsheet ( that incorporates starch content along with NDF digestibility (%NDF, 48 hr) and other nutrients to calculate net energy of lactation (NE-L), milk per ton and milk per acre.

Monitor Degree of Processing

The use of on-chopper roller mills to process corn silage affects the variation of the rate and extent of corn silage starch digestion. To simply say silage was processed is not enough. What is needed is information on the roller mill setting (e.g. typically 1-3 mm depending upon kernel maturity) and objective quantification of the extent of subsequent kernel damage. A standard degree of kernel processing laboratory procedure is commercially available at Dairyland, Dairy - 1 and Cumberland Valley Laboratories to help quantify the degree of kernel damage. However, because this analysis is not a field test, producers still need to discuss processing goals with their nutritionist and custom cutter (if outsourcing chopping).

One way to evaluate harvested silage samples for degree of kernel processing is to collect silage in a 32-ounce cup. Spread the silage on the ground and count the whole or half kernels. Finding two whole kernels or fewer per sample tells you the chop length is ideal; two to four whole or half kernels is adequate. Greater than five requires chopper roller mill and feed roll speed adjustments to achieve desired degree of processed kernels. It is important to monitor each chopper several times per day to ensure processing consistency across fields and hybrids.

When Kernel Hardness is a Concern

Some growers have expressed concern about the texture or vitreousness of corn kernels in silage. The most recent work on vitreousness comes from the University of Wisconsin and supports that silage, harvested wetter than about 35 percent DM, exhibits very little difference in starch digestibility attributable to kernel texture or vitreousness. Specifically, ruminal starch availability showed a decline only after the blacklayer stage of maturity.

Can Corn Silage Have Too Much Starch?

This thought process suggests that grain can always be added to corn silage and one should not sacrifice fiber digestibility to obtain high grain yields. This assumes that high grain yield and high fiber digestibility are mutually exclusive traits. But research shows they are not. Several researchers have shown no relationship between grain content and stover digestibility. Conclusions from the four-year UW corn silage consortium shows that while evaluating forage potential of hybrids might require separate testing programs, grain yield need not be sacrificed when developing hybrids with high dry matter yields and improved nutritive value.

This notion that corn silage can have too much grain seems to also conflict with commonly held guidelines for the amount of starch dairy cows can safely handle in the ration. To put this in perspective, consider an extreme example of 70 lbs. of 30 percent DM corn silage containing 50 percent starch (highly unlikely, even with high-chop corn) consumed per cow, per day. This would only contribute 10.5 lbs. of daily starch intake. If cows are consuming only 50 lbs of dry matter intake, the total ration starch level from the corn silage in this extreme example would only be 21 percent starch. This is well within the acceptable guidelines of most nutritionists. By maximizing starch from corn silage, you can significantly reduce ration costs from supplemental starch without having to sacrifice reduced fiber digestibility.

Weather Has Large Impact On Stover Digestibility

It is clear that reduced stover (cell wall) digestibility can "handcuff" a nutritionist. Variability in corn digestibility impacts both the energy value and intake potential of the silage. However, when it comes to selecting corn silage genetics to plant, the fact is that there are minimal genetic differences between (non-BMR) hybrids for NDF digestibility. The huge variation in NDFD observed by nutritionists is more a function of planting population, growing environment, harvest maturity and fermentation efficiency. Growers should certainly consider fiber digestibility when selecting hybrids to grow, but the selection process should give priority to agronomic traits, grain yield (starch content) and silage tonnage.

The influence of growing conditions, especially moisture seems to be a major source of the nutritional variability seen within hybrids across years and locations. Early research suggests that cool, dry years are best for corn silage quality and that slight moisture stress might stimulate seed (grain) production. Cool temperatures, especially at night, may inhibit secondary cell wall development. These studies suggest that accumulated growing degree days after silking may be most important in affecting corn silage nutritive value because of the impact on grain yield.

The specific timing of environmental stress during the development of the corn plant appears important. A cooperative research study with DuPont Pioneer and Dr. Dave Mertens of the US Dairy Forage Research Center, analyzed unfermented whole plant corn samples from various genetics grown in multiple locations. Each location was geo-referenced to allow for weather station data to be included in the analysis. Findings revealed that weather prior to silking, affects corn plant height, yield and fiber quality. Weather after silking exerts more impact on corn grain yield, neutral detergent solubles:NDF ratio, and total dry matter digestibility (Mertens, 2002).

Corn Silage Management Checklist

  1. Foster communications between the dairy producer, nutritionist, growers, and custom choppers because the dairy has to live with these decisions for an entire feeding year,
  2. Select hybrids with proven (and similar) nutrient profiles backed by adequate yield and nutritional data,
  3. Minimize number of hybrids to improve consistency (without compromising agronomic risk),
  4. At harvest, focus on harvest timing (chop individual plants, shred in a chipper-shredder and analyze with a Koster™ or microwave for whole plant moistures), degree of kernel processing, and bunker/pile compaction (especially the tails of piles),
  5. Consider segregating silage (by quality and livestock group),
  6. Inoculate silage with a research-proven Sila-Bac® brand inoculant product to improve both feed value and consistency.
  7. Monitor kernel processing on the way into the silo and quantify with lab test during feed-out, and
  8. Frequently monitor feed delivery and check TMR for sorting and effective fiber levels.

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