 |
|
|
|
|
What are the recommendations for filling and packing a bunker silo? How should bunker silos be covered? What about fermentation and feed out from bunker silos? What about bunker silo safety?
|
Managing Forage in Bunker Silos by Craig Saxe, Juneau County Agriculture AgentMaximizing livestock production is dependent upon, producing and storing quality forage. Once the crop has been harvested, loss of quality may occur simply because steps were not taken to correctly manage the forage during filling and storage. The purpose of this fact sheet is to review bunker silo recommendations that help to maintain a high quality forage product. Harvest Considerations Forage should be harvested at the correct degree of maturity to assure desired feed quality and proper sugar content for good fermentation. Also, to reduce the risk of weather related losses, a crop should be chopped and stored within three days of cutting. Optimal relative feed value (RFV) is achieved when alfalfa is cut at or near 170 RFV based on scissor clip or PEAQ measurements. Chop alfalfa at 3/8-inch theoretical length of cut (TLC) with 15-20% of the particles exceeding 1.5 inches long. When corn silage is harvested at the preferred maturity of 1/3 to 1/2 kernel milk line and a whole plant moisture of 65-70% the recommended TLC is 3/8 inch (0.375") without a processor or 1/2 to 3/4 inch (0.50-0.75") with a processor. A good rule of thumb is to chop forages, particularly a hay crop, as long as possible and still be able to pack to a desired density. The preferred corn silage moisture range for bunkers is 65-70%. For hay silage the preferred moisture is 60-65%. Seepage of forage juice can occur if forage is harvested at moisture contents above 70%. This juice carries away a high concentration of soluble nutrients, which represents a significant loss of valuable feed. What are the recommendations for filling and packing a bunker silo? Rapid silo filling (within 3 days) increases the uniformity of forage moisture and quality in the silo, and reduces exposure of the forage to precipitation and air during filling. Rapid silo filling is accomplished by having sufficient harvest, transport and silo filling equipment capacity and adequate labor to operate the equipment. Bottlenecks to rapid filling should be identified and eliminated. When sizing storage consider selecting several small units rather than one large unit so you can fill each one quickly and reduce exposure of forage to the elements. The recommended procedure for filling a bunker silo is to spread the forage in thin layers (less then 6 inches) on the sloped filling face (in a wedge shape). Drive over each layer multiple times with one or more heavy tractors to eliminate air and ensure good packing. This "progressive wedge" technique of filling continually covers previous layers of forage, thus reducing exposure to air. The amount of time spent compacting the silage directly affects fermentation. Running a tractor across the surface multiple times leads to better fermentation than when forage is only leveled off with minimal compaction. In most cases this means continuously running one or more packing tractors between loads. A suggested rule of thumb is to allow 5 minutes of packing time per ton of wet forage. Where this is not possible, several heavy tractors may be needed to achieve adequate packing density. How should bunker silos be covered? Once filling is complete, immediately cover the bunker silo with an air-excluding material. Plastic films have proven to be the most effective covers when properly installed. It is estimated that covering a bunker silo with plastic can return eight dollars for every dollar spent due to reduced losses and increased animal productivity. The sooner a bunker cover is installed, the less time forage is exposed to aerobic conditions or precipitation. Once the rear portion of the forage mass is placed and packed, the plastic cover should be installed. If precipitation is expected, rolling the plastic over the surface should also protect the sloped filling face. Plastic bunker cover should be 4 to 6-millimeter thick. The thicker 6-milimeter plastic is easier to handle, more resistant to tears, and more resistant to oxygen diffusion. Plastic must be held tightly to the silage surface and sealed at the edges. When tires are used to weigh the plastic down, they should touch each other to provide a uniform weight and to prevent plastic billowing in the wind. Loose soil or sand bags have been used to give a tight seal at the edges of the plastic. Shape the top surface of forage to shed water from the plastic cover. It is important to prevent runoff from flowing between the silage and bunker walls. This can be done by forming flow channels several feet from the walls and sloping toward the back of the bunker. If punctures occur in the plastic use specially designed tape to repair the plastic. Inspect the plastic cover weekly and repair holes as needed. What about fermentation and feed out from bunker silos? The fermentation phase lasts 14-21 days. During this time, the forage varies in quality from day-to-day. Since cows perform best when presented uniform quality forage, avoid feeding silage during the fermentation period. The removal rate (inches removed from the silage face per day) can influence loss during the feed-out period. Removal rates should not be lower than 6 inches per day in the summer and 4 inches per day in the winter. Maintaining adequate removal rates are especially critical with hay crop silages, high moisture corn and drier silages. When designing storage a good recommendation is to plan to remove at least twice the minimum recommended removal rate. This requires a design that has a smaller face area and longer bunker length. Many methods of silage removal are used on farms. Perhaps the most common method is the bucket loader. The preferred method of silage removal is to slice the silage from the top, and allow it to fall to the floor. Another method is to undercut the silage several inches up from the floor and then slice the balance of the face into the crevice. Whatever removal practice is used, the silage face should remain tight and smooth. Avoid methods that result in dislodging the silage face. Creating gouges, cracks and potholes results in air penetration deep into the silage mass and leads to increased spoilage. Only the amount of silage that will be fed in a short period should be uncovered at one time. Losses can occur due to air penetration at the exposed face and top and from loose silage lying on the floor between feedings. Plastic can be pulled back from the silage top or cut off each day. At no time should more than three days worth of silage be exposed. What about bunker silo safety? Safety is an issue in all phases of silage storage. During the fermentation process, silo gases are released that can cause death. It is important to avoid working in the confined spaces around the bunker silo immediately after filling. During feedout, loader operation must be such that neither the surface stability nor the structural stability of the equipment is comprised. Avoid silage overhangs that occur as a result of equipment that is undersized for the structure. A person walking out on top of an overhang can be seriously injured if the overhang collapses. Also be careful of crust formation that occurs due to spoilage. Serious injury can occur if the silage collapses on someone working underneath it. |
|
