AMES, Iowa – With the limited hay crops in some areas this summer, beef producers may want to consider harvesting corn silage to supplement the cow herd this winter. Corn silage can be a very cost effective feedstuff for cow herds, but proper harvesting, storing and feeding is critical to maintain silage quality and feed value.
Hugo Ramirez Ramirez, Iowa State University dairy specialist, shared his top five priorities for making quality silage at the 2018 Iowa-Wisconsin Silage conference.
1. Harvest at the right moisture content. During the fermentation process, sugar in the chopped corn is converted into lactic acid by bacteria, but the silage needs to be at 35% dry matter (or 65% moisture) to ensure it packs tight enough to become anaerobic so the bacteria can do their job. A ballpark indicator of whole plant moisture is the milkline on the kernel; harvesting at 2/3 to 3/4 milk line is a common practice to capture more energy as starch in the kernel. A better way to determine whole plant moisture is to actually chop up a few stalks and test it for moisture, either with a tester designed for this purpose or by using a microwave and kitchen scale. See instructions for testing silage moisture from ISU Extension and Outreach. A general rule of thumb is that corn plants will dry about 0.5% points each day.
2. Chop length and kernel processing. Good timely fermentation requires an anaerobic environment where the bacteria have access to the sugars and starch in the chopped corn plant. Particle size (and moisture) has a big impact on packing density and oxygen exclusion. When a kernel processor is used, particle size should be about 3/4”, and when a processor is not used the particles should be 1/4” to 1/2” in length. Kernel processing opens up the corn kernel, which results in increased feed quality by allowing better energy utilization by the cow.
3. Inoculants. Bacteria are naturally occurring, but not all bacteria produce lactic acid to assist in the fermentation process. Adding a lactic acid-producing bacteria (LAB) to the chopped corn increases the "good" bacteria and speeds the fermentation process, resulting in less spoilage and higher feed quality. Inoculants are simply inactive, live LAB which are activated when rehydrated, and because they are live bacteria, do not use chlorinated water to rehydrate the inoculant.
4. Packing. Packing to remove oxygen from the pile is critical since the bacteria require an anaerobic environment to ferment the forage. Density (pounds of forage per cubic foot) is used to measure the success of packing silage. Density is influenced by crop, chop length, dry matter, type of structure, delivery rate, packing weight and time. The target density for a bunker silo is 40-45 pounds of fresh forage or 14-16 pounds of dry matter per cubic foot. Density also has an impact on spoilage during feedout, since a less-dense pile allows for more oxygen to enter the pile. A Wisconsin study showed that silage density of 16 pounds of dry matter per cubic foot had a 15% loss, where 10 pounds of dry matter per cubic foot lost 20% of dry matter. A tool to help calculate the number of tractors needed to achieve adequate density based on silage moisture and delivery rate is available from the University of Wisconsin.
5. Sealing and covering. Covering and sealing a silage pile may be the most important factor to ensure good fermentation and an anaerobic environment. A plastic cover specifically designed for use on silage piles that is at least 4-mil thick should be used. These special plastics are designed to resist tears and block ultraviolet light. Some plastics are even designed with high oxygen impermeability. Some plastic covers incorporate one layer of oxygen barrier film with a second layer of UV barrier, or producers can utilize an oxygen-limiting film next to the silage and a black/white UV plastic on top of it. Weight is needed on top of the plastic cover to hold the cover down and prevent air infiltration. Most producers use either old tires or tire sidewalls, and ideally the tires should touch each other, covering the entire pile.
In addition to focusing on silage quality, safety around silage harvest, storage and use also need to be pointed out. One safety concern is silo gases, especially in upright silos, though they can also be a concern in bags or bunkers. The fermentation process produces nitrogen dioxide, which converts to nitric acid when contacting moisture in the lung. At low levels, nitrogen dioxide causes a burning sensation in the nose, throat and chest, while at high levels it causes death within seconds. Fermentation also produces carbon dioxide, which is odorless, colorless and heavier than air so it settles in low spots. It displaces oxygen and can cause death from asphyxiation (lack of oxygen.) The biggest risk from silo gases is in the first two to three weeks after filling. Bleach-like odors or yellowish-brown fumes at the silo base are indicators of nitrogen dioxide. It is recommended to stay clear of the silo for at least three weeks, then run the silo blower for 15 to 20 minutes with the door closest to the top of the silo open, before entering the silo. Do not enter the silo during or after filling for at least three weeks, and keep children and visitors away from the silo area during the danger period. If you must enter a silo during the three-week danger period or even when opening the silo, wear an approved, self-contained breathing apparatus and ventilate the silo for 20 minutes before entering. You should also be attached with a lifeline to someone outside the silo.
Safety risks around bunkers also include machinery accidents during filling and avalanches during feedout. Extra caution should be used by pack tractors, especially when operating above the solid side walls of the bunker to prevent rollover accidents. Trucks delivering forage should unload at the base of the ramp and not operate above the sidewalls of the bunker. When feedout starts, falls when uncovering bunkers or taking feed samples, avalanche of the pile or collapsing silage could happen. Take feed samples from the loader bucket after moving a safe distance away from the bunker face. Try to stay a distance of at least three times the height of the pile away from the face. Always remove silage from the top of the pile first to prevent undercuts which may collapse.
More information on safety can be found at www.silagesafety.org. ISU Extension and Outreach beef and dairy specialists can also assist producers with silage production and feeding.