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The 'invisible' loss in silage making is a hidden cost. Usually, people only feed 75% of the crop Dry Matter (DM) that has been filled into a bunker silo and thus 25% is lost. Studies & research comparing DM losses in silo/round bales
A comprehensive Swedish study reports that 23% of DM is lost on average out of 91 bunker silos examined in the experiment (Seibst, 1991), 17% of which was non-visible in-silo loss and 6% was spoiled and discarded silage. The 'invisible' in-silo losses resulted higher for wet crops (21% at 15% DM) and lower for drier crops (14% at 30% DM). Other studies confirm the amount of losses (Savoie & Jofriet, 2002) reporting 13% in-silo loss of DM in bunker silos. In the round bale system, DM loss is generally much lower. During the last 10 years of ensiling studies at the Department of Animal Nutrition and Management, in the Swedish University of Agricultural Sciences in Uppsala, we normally record a 2-4% loss of DM in our round bale experiments. Every bale is weighed and sampled before and after the storage period and is subject to different experiments using various bale film qualities and number of film layers. The crop DM has varied from 35-70%. Bales are always carefully protected under nets to avoid damages to the film by birds, rodents, cats and other animals. This makes the amount of discarded silage non-existent. The fundamental condition in silage making is that no oxygen enters the silo. Under real farm conditions it is of course very difficult to accomplish a complete air-tightness of the silo, particularly in the case of large silos, where it is impossible to have suitable sized silage sheets that can cover the entire silo. In addition, when the bunker silo is opened for feeding, it normally stays open until it is emptied, which can be up to a month later. These circumstances may explain that DM losses are so big in bunker silos. Round bales provide a better oxygen barrier when properly handled
There are various reasons why we observe much lower loss in the round bales. First of all, the crop (grass and red clover/grass) is pre-wilted to a higher DM content in this system (40-50% recommended), where at this level of DM substantially less fermentation occurs. Secondly, the wrapped bale acts as a mini-silo but much better sealed than the bunker silo. Finally, losses during the aerobic exposure after opening the bale do not exist as the round bale is fed the same day it is opened, while with the bunker silo is remains open and exposed to oxygen during a month or so. Altogether these may be the reasons as to why the wrapped round bale system seems to give at least 10% lower DM losses than other silage systems. This is an important factor to take into account when comparing the economy of different systems. However, it has to be stressed that the good results of wrapped bale silage requires careful handling of the bales. Any small holes from birds or rough handling will change the picture completely. 30% of the bale content is within the first 10 cm inside the film cover. A punctured film layer will easily destroy large quantities of the silage, thus the importance of using high quality films and of applying a minimum of 6 layers to your bales. Rolf Spörndly, Researcher at the Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Uppsala |
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