Forage harvester with additive applicator
What are nutrient additives?
Nutrient additives are substances which, when added to the forage at ensiling, improve the silage’ s nutritive value. Most additives in this category play a dual role.
For example:
- Molasses can be used as a fermentation stimulant, but also provides energy and can be expected to increase the ME content of the silage.
- Non-protein nitrogen (e.g. urea) is added to low crude protein crops, such as maize, but also has a role in reducing aerobic spoilage .
- Grain can be added at the time of ensiling to increase silage ME level and also as an absorbent to reduce silage effluent losses in low DM silages.
Grain
Cereal grains are sometimes used as silage additives. Their main role is to improve the ME content of silages and provide a premixed ration, which some producers see as a benefit. Grain can also play a valuable role as an absorbent when ensiling low Dry Matter (DM) silages.
It is advisable to roll the grain before mixing it with the forage at the time of ensiling (see Table 7.22) to avoid any reduction in grain digestibility, which can result when animals consume whole grain.
To minimise potential spoilage of grain during the ensiling process, it would be prudent to avoid placing grain where losses may occur – near the surface, sides or bottom of the silo.
With higher DM silages (>30%), if the only objective is to increase ME content, adding grain at the time of ensiling may not be the best strategy. Rolled grain could be added to the silage at the time of feeding, avoiding the risk of in-silo losses.
Adding grain at ensiling can have other advantages. It can raise the DM content when added to wet forages, reducing the risk of a poor fermentation and reducing effluent losses (see Table 7.22). The improvement in the silage fermentation is predominantly due to the increase in DM content, as grain contains only a small proportion of Water Soluble Carbohydrate (WSC) and most Lactic Acid Bacteria (LAB) have a limited capacity to ferment starch.
In the study in Table 7.22, adding grain at the time of ensiling significantly reduced effluent and total in-silo DM losses and improved cattle production when compared to adding an equivalent amount of grain at the time of feeding.
An alternative strategy is to add formic acid at ensiling to improve the silage fermentation, and then add grain at the time of feeding. However, this would be a more expensive strategy than adding the equivalent amount of barley at ensiling, and would not reduce effluent losses.
Minerals
Minerals are added to forage at the time of ensiling to improve the mineral content, such as the addition of limestone (a calcium source) (at a rate of 5-10 kg/t fresh crop) to maize. Addition of magnesium when ensiling pastures in areas with a high incidence of grass tetany in cattle is another possibility.
Because addition of minerals may increase buffering capacity, it is advisable to avoid adding minerals to low-WSC, low-DM forages.
