If you are planning to build new silage storage there are several things to consider in addition to spoilage losses. Losses for a particular type of silage storage structure can vary widely depending on how well the silage crop and the storage structure are managed. Because the storage structure must fit into a whole system for making, storage and livestock feeding system, the existing facilities may influence your choice.
To answer your question directly, Dr. Brain Holmes at the University of Wisconsin-Madison has an article on silo losses and loss reduction. This publication includes a table (Table 1) that summarizes the various types of losses from different types of storage structures. This publication can be found at http://www.uwex.edu/ces/crops/uwforage/prevent-silage-storage7.PDF. If you do not have access to the Internet, your local extension office should be able to help you get a copy. This article was written with dairy in mind but much of the information is applicable to a beef cattle operation too.
Dr. Holmes has another useful publication that discusses all the factors to consider before making a decision about a new storage structure. It is called “Deciding on A Silage Storage Type” and it is available on-line at: http://www.uwex.edu/ces/crops/uwforage/DecidingSilo.pdf
The overall cost of a storage system is of critical importance. Focus on the cost per ton of usable silage coming out of storage. This accounts for the investment you make in the structure, the cost of filling and feeding out, and the losses that occur during ensiling and feeding. There is a Microsoft Excel© spreadsheet available at:
http://www.uwex.edu/ces/crops/uwforage/storage.htm called
"Cost of Forage Storage Spreadsheet" and it is accompanied by a "Documentation" file. This spreadsheet helps analyze the investment and yearly operating costs for various types of forage storage structures but you will need to collect the cost information on the structures you are interested in and the other specific costs to be considered. Evaluating the economics takes some work and effort but you will live with your decisions for a long time, so it is worth it.
