Producing silage allows farmers and ranchers to preserve feed and forage for their livestock to supplement or replace grazing when conditions are unfavorable, whether that’s due to season, drought, or other causes. Silage has an advantage over hay and other dried feed because its high moisture content preserves more energy and more nutrients from the forage. Moreover, the acidic, anaerobic conditions of properly stored silage inhibits the growth of molds and bacteria which spoil feed and can cause serious illness in livestock.
Silage can be an excellent, cost-effective response to the need to supplement livestock feed, but it requires careful management from harvest, through fermentation, to storage and feedout in order to produce a reliably high quality product. In this article, we’ll discuss some challenges inherent in the practice, review several clamping options with their pros and cons, and finally we’ll cover the challenges of feeding out.
In each of the four basic stages of silage making, there are important factors which affect silage quality: some can be controlled, some cannot. For example, ambient temperature affects all stages of silage production, including moisture content. In particularly hot or dry seasons, crop yield and nutritive value can diminish, while some warm season grasses may lean more toward undesirable fermentation types. Finally, warm temperatures during feedout can accelerate aerobic deterioration.
Farmers can mitigate some of the challenges of silage making by carefully selecting forage species and monitoring their maturity and moisture concentration at harvest. Harvest techniques, chopping strategies, and the speed and method of ensiling are particularly important factors when managing both aerobic and anaerobic stages of fermentation. Many farmers choose to inoculate silage in order to regulate bacterial activity for optimal fermentation. Finally, careful management of the feed-out stage preserves the quality of the silage and reduces risk of spoilage and mold growth.
Filling and Compaction
From the time it is cut to the point where the silo is sealed, forage is exposed to oxygen and losses in the nutritive value of the crop is heaviest. To minimize those losses, it’s critical to minimize the time spent in this stage. Harvesting when moisture content is optimal means less time spent in the field as the forage wilts. Once the crop has reached the target DM, it should be immediately collected, compacted, and sealed to eliminate as much oxygen as possible from the container. Speed and careful compaction are critical in this step, since too much oxygen in the ensiled forage will delay anaerobic fermentation and could lead to poor quality silage as well as aerobic instability at feedout.
The compaction process requires a strategic approach. It’s not realistically possible to compact more than about 6 inches of chopped forage at a time, so layers should be evenly spread across the clamp to this maximum depth and compacted thoroughly before the next layer is added. This can be challenging when trailers arrive too quickly and in the rush to ensile it, proper compaction is sacrificed. It’s better to adjust your harvest and wilting schedule than settle for inadequate compaction - poor quality or rapidly spoiling silage raises costs considerably in the long run.
During compaction, pay particular attention to the edges of the clamp, which are more difficult to consolidate. Overfilling bunkers should also be avoided, since density drops once the forage reaches above the walls.
Sealing the Clamp
Once the silo has been filled and the material compressed to the desired density, it should be sealed to prevent exposure to air (oxygen). Any exposure to oxygen while ensiled can compromise anaerobic fermentation and decrease aerobic stability. All sides of the clamp should be covered, preferably with a single sheet sized to match the dimensions of your clamp.
Always put as much weight on top of the clamp as possible. The weight on top keeps the material compacted, particularly at the top, where it’s most likely to relax.
Covering the Clamp
Horizontal silos (bunker, trench or stack) are particularly vulnerable to degradation and spoilage caused by air and moisture entering the silo. These intrusions can affect the fermentation process as well as the quality of silage during storage and feeding, such as problems with mold, excessive DM, and nutrient losses. This damage can be much more extensive than expected. In fact, some studies have found a DM loss of 30% or more in the top 3 feet in uncovered bunkers. Depending on the dimensions of the silo, the value of that lost or degraded silage could be eight times the cost of properly covering the pile, including the expected labor costs involved in placing and weighting the cover.
In practice, polyethylene covers are preferred for their durability. Reinforced polyethylene includes a woven scrim layer that provides exceptional resistance to tears and punctures. BTL’s ArmorCover product is available in 9 mil and 12 mil thicknesses with a white side and a black side. Keep in mind that mils are not mm, and in fact 9 mil is equivalent to approximately 1/100th of an inch. This very thin, flexible material makes the cover extremely durable, lightweight and easy to deploy and can even tolerate foot traffic (which should be kept to a minimum!)
Silo covers should protect from the possibility of seepage from effluent or rain that has drained through the pile. Leachate from silage is extremely damaging to the environment, with a BOD (biological oxygen demand) that can be hundreds of times stronger than raw domestic sewage. Proper management of silage seepage is a critical part of silo management.
Ideally, your silo cover should have a white side and a black side. The white side should face out to reflect heat in order to protect the silage from overheating, which can damage proteins. It also minimizes exposure to UV rays, which can degrade the cover over time. The black side should face inward to the silage and creates a fully opaque barrier to prevent the growth of oxygen-producing algae.
