(1) Dry matter loss
Storage losses vary with the type of silo; the species, stage of maturity and moisture content of the ensiled crop; and the efficiency of excluding air and water from the silage. Some loss of dry matter always takes place whenever a crop is ensiled, even with the best storage structures and the highest level of management. This feed loss is made up of the following:
Surface Spoilage - Unless sealed in some way from air and moisture, the exposed surface of silage will rot after being placed in a silo due to the growth of molds and bacteria. As well, if silage that is exposed to the air is not removed fast enough during the feed out period, spoilage may occur here also. This material has a greatly reduced feed value.
Ensiling Losses - During the ensiling process, dry matter is consumed to form various organic acids, gases (particularly carbon dioxide) and heat. The latter two escape unseen from the silage mass. The amount of air incorporated within the silage at the time of filling, as well as that which is subsequently allowed to enter, affect the nature and duration of the ensiling action and thus the extent of dry matter loss, particularly in gaseous form.
Seepage Losses - This type of loss is caused by the squeezing out of excess liquid (mostly cell sap) due to the pressure of the overlying silage mass. For each moisture level there is a maximum pressure beyond which seepage will occur. Thus seepage losses increase with higher moisture levels and greater' depths of silage.
One of the major variables involved with storage losses is the level of management applied to any storage structure. Following the basic principles of good silage making, for example, good air exclusion from the silage, control of the moisture level at time of ensiling, etc, will in itself greatly reduce total storage losses.
Losses as influenced by the type of storage structure are difficult to assess due to the many other factors which also affect losses. However, a number of research projects have been carried out (principally in the U.S.A.) to determine these figures. A review of reports on these projects indicates that using sound structures with good management, average total dry matter losses arc approximately 5% for oxygen-limiting silos, 10% for conventional open-top silos and 15% for horizontal silos. Unfortunately, these projects were carried out with small to medium-sized silos. Larger structures, particularly horizontal silos, should have somewhat less loss, especially if the depth is increased above the 8 ft. commonly used in the experiments.