Although many factors are involved in final silage quality, there are best management practices that will set you up for success. These apply to all ensiled forages but there are nuances to consider based on crop type, or more appropriately crop characteristics. Making high quality silage always starts before you plant your silage crop. Start with the right forage choices based on your livestock feed requirements and the limitations of your soils, climate, equipment and management.
Timing your silage harvest is critical. Set forage quality targets and learn what that looks like in the field in terms of crop growth stage or maturity. Know whether these quality targets fit your context, and be prepared to adapt or compromise due to weather, equipment, and so on. Dry matter targets are the other component of ideal harvest timing. Have a dedicated person to monitor crop dry matter in the field, and confirm this number with truck weights and dry matter at the pit. The target typically quoted is 65% moisture or 35% dry matter. 2-3 points wetter is often preferred, especially for corn. For annual crops like barley or corn, which are often harvested during grain-fill, there is a trade-off between starch content and dry matter. If we try to push starch levels too far, we risk a dry forage that will be difficult to pack, ensile slowly and incompletely, and lead to mould and yeast challenges. In addition, the extra starch we accumulate by harvesting late will have reduced digestibility and may go right through our animals. For perennial or immature crops, the goal is to have even dry-down and as little time as possible to wilting. Ideally, the plants should lose moisture through photosynthesis rather than evaporation, as this will maintain sugar levels in the forage and result in higher energy forage. This type of dry-down can only be accomplished through a combination of laying the crop down over 80% or more of the ground surface to maximize sun exposure, and not crimping the forage. “Haylage in a day” is ideal, but is only possible with the right equipment and management practices. It is better to err on the dry side if your alfalfa or grass silage has lost its sugar content in the swath.
Adjust your chop length or “theoretical length of cut” based on the dry matter of the silage. There are published benchmarks for ideal chop length based on packing and livestock requirements. When the forage gets too dry, however, it needs to be cut shorter to achieve the same packing density and to minimize porosity, which means more fuel and time per ton of silage. Another cost of harvesting too dry. When the forage is actually too wet but the harvest must go on, a longer chop length will help reduce bunker drainage or effluent to some extent. Corn silage that is at ideal moisture or drier should also always be kernel-processed. Over-mature cereal silages can also benefit from kernel processing, but kernel-processors are not typically designed for cereals and this can be difficult to achieve in practice. Silage inoculant options keep expanding as new bacterial strains are developed. When dealing with a high-sugar or starch crop like corn or barley silage that is harvested at ideal moisture, a basic fermentation enhancing or oxygen-scavenging inoculant is all you need to achieve a well-ensiled forage. These easily-fermented forages are also the most likely to see heating or spoilage issues on the face after the bunker is opened. If feed-out will be slow or during warm summer weather, or if the silage is on the dry side, an L. buchneri bacterial strain will be cost-effective. If dealing with high-protein, low energy alfalfa swaths that are on the wet side, a clostridial inhibiting inoculant will be the best choice. This is a good example of how a recommended practice of silage inoculation is nuanced by forage characteristics or harvest conditions, which are connected to the crop species.
Ensure that you have enough packing weight to keep up with incoming silage. The commonly used “1:800” rule of thumb, which means you need at least 800 lbs of packing equipment for every ton/hour entering the pit, is a good starting point. This means that if you’re hauling 10-ton truck loads and you’re doing ten loads per hour, you have 100 tons coming in per hour, and you need at least 80,000 lbs of tractor packing at all times. Remember that tractor tires are often designed for flotation rather than compression, so never pack more than 3-4 inches at a time. If using a tracked tractor or your silage is too dry, even thinner layers will be necessary. You can’t catch up later by packing extra at the end. That air is trapped inside. For end ramps of a bunker or all sides of a pile, target a 1:3 slope. Any steeper and you are no longer packing downwards and cannot achieve the density necessary to prevent spoilage. Finally, if building a pile, do some quick math and don’t build your pile too wide. Make sure you can remove six inches or more from your silage face every day in winter, and twelve inches in summer. Seal the pile to prevent oxygen from entering and composting your silage. Two layers of plastic is better than one. Using a true oxygen-barrier film will result in the least dry matter loss and surface spoilage. Weigh down the plastic across the entire surface and especially fully seal all edges; if air gets in between, you’re defeating the purpose of the plastic.
– Kenneth Van Driesten, MSc, CCA (Forage Specialist) and Mark Cameron, PhD (Vice President of Sales and Nutrition), More Than Just Feed