Harvesting for Maize Silage
To achieve the best nutritional results maize should be harvested at the optimum dry matter ( DM ) content of 30-33%. To determine whether the crop is at the correct stage for harvesting, a visual assessment of the ‘ Milk Line ’ can be made. The ‘ Milk Line ’ distinguishes between the hard, yellow starch part of the grain and the soft, white, ( milky ) starch part. As the grain matures, the milk line descends towards the centre of the cob and the proportion of hard, yellow starch increases. To achieve 30-33% DM maize silage, it is recommended to harvest when the milk line is halfway down the grain.
If the crop is harvested when the milk line is only ¼ of the way down, estimated silage DM will be 28-30%. Below 30% DM; Lactobacillus bacteria must generate higher levels of lactic acid to stabilise the silage, to achieve this they must consume more sugars which results in a nutritionally poorer and more acidic silage.
Furthermore, Clostridia bacteria prefer these wetter environments and instead of lactic they produce butyric acid; this is a weaker acid which prevents silage stabilisation enhancing the risk of silage deterioration and DM losses. Harvesting with a milk line ¾ of the way down will produce a DM silage of over 35%. Clamp consolidation is burdened when maize is harvested above 33% DM which will facilitate oxygen contamination causing silage deterioration and DM losses. Furthermore, the higher proportion of hard, yellow starch will reduce its digestibility and may pass directly through the animal.
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