Decisions made about silage harvest can greatly influence the nutritional quality of the feed, and consequently, animal performance for the following 12 months.

Plant maturity at harvest, moisture content, speed of harvest, chop length, silage distribution and compaction are all pre-ensiling factors that require close attention.

“Monitoring crop maturity and moisture content closely is critical because corn must be ensiled at the proper maturity and moisture content to ensure maximum energy density and the most efficient fermentation for preservation,” says Wes Kezar, area manager for Pioneer, Boise, Idaho.

If silage is ensiled too wet, there is a good chance the crop was harvested too early, losing valuable energy in the resulting silage. There may also be excessive losses due to run off. On the other hand, harvesting corn silage when it is too dry leaves a crop prone to excessive heating and potential yeast and mold problems.

Timing silage harvest

While kernel milkline is often used as an indicator of whole-plant moisture, university studies have shown there can be tremendous variations among hybrids and years, notes Kezar. “The milkline predicts only 40 to 60 percent of the variation of moisture. Soil moisture conditions, type of hybrids planted, fertility, plant stress, population and other factors also can influence whole-plant moisture.”

Instead, Kezar recommends growers use the milkline or starch line as an indicator to begin testing whole-plant moistures using a microwave or Koster moisture tester.

“Moisture testing, along with monitoring milkline or starch line development, is the most accurate way to determine whole-plant moisture,” says Kezar.

“As the plant matures past optimum values, field losses cut dry matter yields and less moisture may make compaction and fermentation more difficult,” says Kezar.

Cutting height

As a rule of thumb, as cutting height increases, forage yields decline and quality increases. This is because lower quality, high neutral detergent fiber (NDF) material is left in the field, says Gene Gengelbach, field nutritionist for Pioneer, Archold, Ohio. University and Pioneer studies show that as cutting height is increased from four to 18-20 inches above the soil, yields are reduced by 12 to 15 percent. However, digestible energy increases as cutting height increases.

“When yield and quality are factored together to determine the potential milk or meat produced, the tradeoff of yield and quality can be measured,” says Gengelbach. “Research shows the breakeven point between yield and quality is at a cutting height of about 8 to 12 inches. Depending on the market value of the silage, a grower can choose to emphasize quality or yield by raising or lowering the corn-cutting height.”

“Employing best management practices throughout the silage harvest process is important because once the feed value of corn silage is lost, it cannot be replaced,” concludes Kezar. Follow these practices to ensure high-quality silage.

  1. Ensile silage as quickly as possible to minimize exposure to air and reduce the opportunity for spoilage.

  2. Sharpen and properly adjust chopping knives to ensure a clean chop and prevent shredding, which can cause seepage.

  3. Apply a quality, research-proven silage inoculant to help enhance the preservation and nutritional quality of silage, improve fiber digestibility, reduce protein degradation and extend aerobic stability at feeding. Kezar recommends producers choose a reputable bacterial inoculant that has received ISO 9000 certification for quality control standards.

  4. Correctly pack silage bunkers using the heaviest wheeled tractor possible.

  5. Properly seal with plastic to protect silage from air and rain.