Bagged Silage vs. Silage Bunkers & Piles
Making silage is an effective way for many producers to best use the resources available to their operation. However, for some, spoilage and shrink can result in significant loss that can greatly increase the cost of silage fed and impact animal performance. Bagging of silage offers flexibility for operations of all sizes to produce silage while potentially reducing spoilage and shrink loss. The intent of this article is to create familiarity with the concept of bagging silage, describe the process, and outline some of the key advantages and disadvantages to this method of silage production.
How Does Silage Bagging Work?
In the bagging system, silage is packed into oxygen and light impermeable plastic sleeves for the ensiling process and long-term storage. The target moisture content for forage going into a bag is 30-40% DM, which is the same range for making silage in a bunker or pile. Silage bags come in many diameters and lengths to suit the needs of different operations; 8 ft in diameter and 150 ft long is a common small bag size. While density of silage impacts the capacity of a bag, this size will hold between 100-150 tons (as-fed). Bags that are 10 ft diameter and 300 ft long are also commonly used and will hold between 350 to 450 tons (as-fed). The Silage Bag Capacity Guide from the University of Wisconsin can help you determine potential capacity of various sizes (bag diameter and length) and packing densities.
Packing silage into the bags may be accomplished via pull-type or self-propelled baggers. For operations that plan to bag silage themselves, the pull-type is more affordable. Used models can be found for $20,000 to $40,000. Self-propelled silage baggers are typically owned by custom silage bagging operations or operations that make a lot of silage, since they are often 10 times the cost of pull-type baggers.
In the bagging process, silage is unloaded from a standard silage trailer onto a belt conveyor that carries it into the rotor of the bagger. From there, it is mechanically packed into the bag. Cables along each side of the bag run from the bagger to a backstop to allow for control of packing density. The bagger is moved forward by the operator as the bag fills and the desired density is achieved. Many video examples are available on the internet. When ready for use, silage is fed out of the bag in the same way it is fed from a traditional bunker silo.
What are the Advantages?
The primary advantage of bagging silage is that it reduces exposure to oxygen. This effectively eliminates the uncovered period between packing and covering the pile/bunker with plastic that occurs in a traditional system. In general, this period can result in about 5 to 7% loss (of the total amount of silage produced). For those who don’t have the labor to cover a bunker or pile, this can be an even bigger saving, with losses from surface spoilage ranging from 10 to 20% of the total silage. Those that use piles will see the biggest losses because they have more surface area exposed, and thus a greater advantage in switching to bagging. Beyond the shrink loss (disappearance of silage DM), the spoiled silage layer that remains when silage is not covered is about 22% lower in digestibility than unspoiled silage and appears to negatively affect the rumen environment. The Kansas State University study Effect of Level of Surface Spoiled Silage on the Nutritive Value of Corn Silage-Based Rations (2000) and UNL Beef Systems Specialist Dr. Mary Drewnoski’s Silage Guidelines Market Journal interview (2017) explain that feeding spoiled silage impacts rumen environment and digestibility of other feeds. Proper use of silage bags can help prevent feeding spoiled silage and the resulting disruption of rumen function.
The other major advantage of bags is the small feed-out face, which minimizes feed-out spoilage. For many cow-calf operations and smaller backgrounding operations, the reduction in feed-out losses can be quite large upon converting their systems from silage bunker/piles to silage bags. When well-managed, feed-out losses in bunkers can be 3% or less. To achieve this, however, at least 5 inches need to be removed from the entire face each day in the winter and 8 inches in the summer. If removal rates are less, even with proper removal technique (keeping the face tight), a loss of 10% of the silage or more, depending on outside temperature, can occur. These estimates don’t account for the loss of feeding value for the silage that remains.
What are the Disadvantages?
One of the chief concerns of silage bags is that, while they are impervious to oxygen and light, bags can be damaged. Holes and punctures must be sealed quickly and properly to avoid spoilage. Many bags come with repair kits, and specially designed vinyl repair tapes are widely available– duct tape is unfortunately not acceptable for repairs since it is oxygen permeable. It takes skill and practice to successfully pack a smooth, dense bag, which places significant responsibility on the silage bagger operator to carefully monitor rate of filling. Some companies have created bags with lines that appear when stretched which allow for a quick visual estimate of fill to make this task easier.
Another less obvious complication is the disposal of used silage bags. You can check with your local waste disposal service, landfill, or Natural Resources District to inquire about recycling opportunities like this one in the Lower Republican District. Additionally, in Nebraska, Delta Plastics offers free pickup of used bags provided they are rolled tightly and surpass 40,000 lb. (20 tons) of plastic. It is preferred that the bags are loaded in a box van. Delta Plastics designated pickup locations in the state include Scottsbluff, Bridgeport, Minden, Gibbon, Chapman, and York. Contact Delta Plastics at (800) 277-9172 or firstname.lastname@example.org for more information.
Bagging silage can reduce spoilage/shrink loss, especially for those that do not cover their silage bunkers or piles with plastic.
Switching to bags can reduce feed-out losses and improve the feed value of silage. This is especially true for those that do not remove 5 to 8 inches of silage off the face of the bunker or pile each day when feeding.
Want to Learn More About Silage Management?
For more information on bagging silage, the University of Wisconsin-Madison Team Forage website is a great resource. The article Managing Forage in Silo Bags provides a lot of practical tips and recommendations to get the most out of bagging silage.
For general information on silage management, including how to reduce losses when using bunkers and piles, check out the proceedings and videos from the 2018 Silage for Beef Cattle Conference.
Interviews with the authors of BeefWatch newsletter articles become available throughout the month of publication and are accessible at https://go.unl.edu/podcast.