Growing Beef Newsletter
August 2025, Volume 16, Issue 2
Planning for corn silage with safety and efficiency in mind
Aimee Wertz-Lutz, IBC director, and Beth Reynolds, IBC program specialist
Although the heat of summer is upon us and corn growing season is in full swing, it is time to begin planning for feed resources to carry us through winter. Corn silage is a versatile, cost-effective resource that can be used to feed multiple cattle groups. When considering corn silage as an option, it is important to consider tonnage needed, harvest and storage plan, safety, and pricing.
Developing a silage budget. Estimating how much silage will be needed is important to prevent a shortage at critical feeding times or wasteful excess at the end of a feeding period. Developing a silage budget that includes intended animal groups and how much and how long groups will be fed gives an estimate of how many tons of silage need to be harvested. It is important to include shrink in this estimate because different storage methods result in varying amounts of waste. Once a silage budget is established, the number of harvested acres needed can be predicted by using an estimated 20-25 ton as-is corn silage per acre yield.
Storage planning. The method of storage and capacity of a silo also should be planned ahead of harvest. Method of storage impacts the nutritional value and preservation of corn silage. Upright silos result in the least amount of silage loss (5-6% loss of silage DM). However, they are expensive to maintain. Horizontal bunker or trench silos are less expensive to maintain but result in a little more waste (10-15% estimated DM loss). Temporary silos such as silage bags or piles have the highest variable loss, which can be as little as 7% DM with well-managed bags but as much as 25% DM loss with poor management. Horizontal silos often are the optimum balance of structure cost relative to the amount of product waste. Packing green chop in horizontal silos as it is harvested pushes out oxygen and helps ensure a good ensiling environment. Packing as silage is loaded also lessens the amount of loose shifting material that, along with silo sloping, can result in tractor rollovers. Slopes intended for driving should not be steeper than a 1-foot rise over a 4-foot run.
Silo design and capacity. Horizontal silo sides that slant inward at the bottom allow for some gravitational force and help establish a well-packed base, reducing spoilage. Mounding the top center of a horizontal silo allows precipitation to drain away from the surface, and creating a sloped base around the silo allows precipitation to drain away from the base. Horizontal bunker capacity should be based on silage budget so that daily usage from the face of the silo keeps ahead of spoilage. The amount of silage removed from the height x width x 8-12” depth should be an amount that can be fed to the fewest number of animals within a 24-hour period to minimize silage spoilage and waste. A deeper cut can be taken from the surface during periods of high silage feeding. Surface spoilage will vary with season, and is greater during hot summer months. The height of the horizontal silo should not exceed the height of the unloading equipment. Silage avalanches, where overhead silage collapses as underneath material is removed, are a safety issue for the feeder. While the top of a horizontal bunker will crust over, that crust is a costly waste and can contribute to disease. Covering the bunker with a water and tear-resistant plastic covering that is weighted down will lessen waste and disease risk. The cost of wasted silage can often justify the expense of purchasing a covering. If the upper spoiled crust is included in the feed, there is a risk of bacteria such as C. botulinum or L. monocytogenes infecting cattle. These pathogenic bacteria are associated with a disease commonly referred to as silage poisoning, which can be fatal to both cattle and humans.
Nutritional variation. Nutritional value of silage can vary widely depending on how well-eared the silage is, the maturity of the silage at harvest, and the degree of stress the corn has experienced during the growing season. It is recommended that nutrient analysis be done on corn silage at harvest and periodically during the feeding year to determine if significant changes in nutrient composition or moisture have occurred. Storage and harvest methods can impact the ensiling process, which takes green chop packed into oxygen-limited storage through anaerobic microbial fermentation, which in turn produces acid, lowering the pH of the material over a 21-day period and preserving it. In addition to preserving the material, the microbial fermentation also consumes nitrates, which can be high in stressed corn, and may metabolize some mycotoxins, which can exist on stressed corn as well.
Harvest. As corn matures, there is a trade-off between accumulated starch and fodder digestibility. Harvesting silage to balance starch accumulation and digestibility is key to the nutritional value of silage. At harvest, maturity (dent-black layer stage; 50-70% moisture), chop length (1/2” to 3/4”), and chop height (4” to 6” above ground) are recommended to balance nutritional value and storage quality. Silage chopped before the dent stage can have a lower energy content since the grain is not fully developed, whereas silage that gets too mature can become drier, compromising fodder digestibility and becoming more difficult to pack. Corn silage chopped at a finer chop will pack tighter, but may result in digestive issues. It is recommended that corn silage that has gone through drought or early frost be chopped at a height of 12” as nitrates and mycotoxins generally accumulate below this point. The Penn State Shaker box can be used as a tool to assess silage quality. It is recommended that with 50% of the silage remaining in the top two boxes, there will be sufficient effective fiber while still packing well.
Safety. Tractor rollovers, silage avalanches, and pathogenic bacterial infection with poor storage conditions have already been addressed as safety concerns with silage. Additionally, silo gases released during the ensiling process are also a concern. Silo gases can be toxic to livestock and humans. The greatest threat from silo gases is within the first 3 weeks post-harvest as microbial fermentation occurs, and the concern is greater with upright silos than horizontal silos because of differences in ventilation.
Estimating silage price. There are numerous ways to estimate a price for corn silage to be used in ration formulation. Production cost records is one way. Another way is to estimate a price based on the opportunity cost of corn. An acre of corn can be chopped for silage or harvested as grain, but not both. Because corn grain is sold as a commodity, the value of an acre can be calculated based on expected corn grain yield and value of the grain at sale. Dividing the value of this acre by the tons of silage produced by that acre will provide an estimated price per as-is ton for the silage. For example, if an acre can yield 225 bu at $4/bu, that acre is worth $900 if sold as grain. If instead that acre is chopped as silage and yields 25 tons per acre silage, $900/25 tons gives a silage value of $36 per as-is ton. A quick rough estimate is to multiply the current value of corn ($/bu) by 8X or 10X to yield a silage value per as-is ton. This method yields a value of $32 to $40 per as-is ton if corn is $4/bu.
Summary. Corn silage is a versatile resource that can be used to winter breeding stock and grow feeder cattle. Numerous factors, including harvest and storage, go into making well-preserved corn silage with good nutritional value. Beginning with a silage usage budget and a plan for harvest and storage will lessen the risk of short-fall or overage, as well as result in consistent nutrient quality. As with all agricultural practices, it is important to be aware of the potential pitfalls and approach the practice of silage making with safety in mind.
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