Warm maize silage upon opening - what are the causes?

The first maize silages maize silages were opened over the last few days. The silages have been, on occasion, considerably warmer compared to previous years. Two different causes come into question for such heat. As well as reheating reheating it is possible that it could be "storage heat". AGRAVIS expert Dr. Sabine Rahn explains how this heat arises.

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In order to distinguish between both causes, a simple test can be used: simply measure the temperature from the core to the edge of the clamp. If the silage on the edge is cooler than in the core, then this is storage heat. If reheating problems are the cause, then the temperature rises at the edge of the silage.

How does "storage heat" occur?

The term "storage heat" describes that the silage was already warm or became warm during the start of ensilaging or during storage. Two causes are most likely here:

  • Temperature during harvesting
    If, for example, ensilaging is done on a hot day, then the maize also has this temperature when in the clamp. When there, it only cools very slowly. Upon opening the silage, temperatures of 20° to 25° C are not uncommon. If silage management was in order then silage cools quickly at the opened cut surface.
  • Breathing processes at beginning of ensilage
    During storage, air can also access the silage. Depending on how well work was carried out (packing) or how quickly air was excluded (covering) then this phase may last a longer or shorter period of time. Micro-organisms such as yeast and fungi are mainly responsible for the changes taking place, alongside the still living plant cells. If sufficient oxygen is available, they are active and reproduce. This creates heat. Usually, the air that is also stored is used up within a few hours and does not cause any problems. The longer this phase lasts, the more heat is released. In addition, the yeasts and fungi reproduce at a very high rate. This also applies to ensilage of maize plants that have been damaged due to dryness and become straw. As the material is very dry, this also means that more air enters the clamp. If these silages are now opened, then they are often considerably warmer than "normal" maize silages. Such maize silages must be frequently monitored with regard to temperature developments as there is a strong propensity for such reheating to take place. During ensilage itself, silage does not become noticeably warmer. At most, a rise in temperature of between 3 and 5° C is expected.

Further information regarding the topic can be found here here.

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