Cereals provide tremendous flexibility for silage makers – they can be sown in autumn or spring and can be harvested at a range of growth stages from boot stage (before seed head emergence) to ‘cheesy dough’ stage (when the cereal grain has the consistency of soft cheese). Cereals have the potential to be ensiled into nutritious palatable silage which gives good stock performance. Sadly, all too much of the cereal silage I see falls short of this potential due to errors which could easily be avoided. Below are some areas to focus on for making high performance cereal silage.
Crop selection and timing of harvest
Oats are more commonly cut at the boot stage, and sometimes at the ‘milky dough’ stage. Barley, wheat and triticale are usually grown to harvest at the ‘cheesy dough’ stage but all three can be harvested at the boot stage. At the cheesy dough stage, barley dries down fastest so it only has a narrow window between ‘not quite ready’ and ‘too dry’ (in dry conditions this can be just a few days). Triticale has the widest harvest window and can be a better option where there is less control of time of harvest. Cutting at the boot stage will give a higher protein silage with energy coming from digestibility of the leaf, and cutting at the ‘cheesy dough’ stage produces a lower protein silage but with good energy coming from starch and more physically effective fibre.Cutting after seed head emergence but before grain fill gives a lower energy silage, as the fibre in the straw is less digestible than the leaf and there has not yet been sugar and starch accumulated in the grain. Select a cereal type that fits with the planned crop rotation, and results in a silage with the desired nutrient profile.
This should be a carefully thought through process to ensure the most appropriate product is selected. Cereal silage cut at the boot stage usually has a lower dry matter (DM) % and high protein content, requiring more acid production During fermentation, so an inoculant that ensures a fast efficient fermentation is likely to be most beneficial. Cereals cut at the cheesy dough stage usually naturally ferment quickly, as they have a higher DM%, high starch and low protein content. However, high starch silage is more prone to heating at feed out due to yeast and mould growth, so an inoculant that improves silage stability at feed out is likely to be a better choice. Only consider additives from reputable companies that are supported by sound research.
Cereal silage cut at the boot stage usually needs to be wilted before ensiling, and as long as it isn’t over-wilted it should be relatively easy to compact. When cereal plants get to the cheesy dough stage, the plant should be dry enough to direct cut – the target is 38% DM. At this growth stage plants can be drying fast and a crop can go from ‘not quite ready’ to ‘too dry’ in a matter of days, so vigilance is crucial. Once the crop is over 40% DM standing, it can be hard to compact – chopping shorter and packing in thin layers will help. When baling cereals at the cheesy dough stage, it is best to err on the early side and use knives in the baler to help with compaction. Poorly compacted bales are more likely to go mouldy.
As cheesy dough cereal silage is prone to aerobic spoilage (such as caused by yeasts and moulds when air is present), it is important to seal it well to keep the air out once good compaction has been achieved. This means covering straight away, sealing the edges really well and using touching tyres (unless you are using a new sealing system with gravel bags). Some oxygen barriers have been shown to reduce aerobic spoilage losses in the top metre which is particularly beneficial for cereal silage – but make sure to ask to see the research as not all ‘oxygen barriers’ have the same sealing effect. For bales, use at least 6 layers of quality wrap and move wrapped bales either within a day or after they have fermented, to avoid ‘popping’ bales when they are lifted and damaging the integrity of the wrap. Bales should be stored on a suitable free-draining site, stacked no more than 2 high and not jammed up hard against each other.
Whole crop cereal silage is often referred to as a ‘rat magnet’ as it is so attractive to rats and mice. Baiting needs to be done early, before the rats and mice are established in the silage. It also helps to spray out the ground around the silage so there is no cover for rodents, particularly along the sides of tubes and ag bags. Birds are also attracted to whole crop cereal silage, they pick out the grains from the exposed silage face and leave the straw. Nets can be used to keep birds off the face.
Once stacks and pits are opened up and the silage face is exposed to air, yeasts and moulds can start to grow, resulting in nutrient loss and risk of mycotoxins. To minimise losses, the removal rate should ensure the face goes back at least 30cm per day. Making a narrower, longer stack can help achieve this for lower stock numbers. A block cutter is ideal for keeping the silage face smooth with minimal air penetration. If a bucket is used, chip down and then scoop up all the loose silage rather than pushing the bucket up into the silage face which helps air penetrate further in. Try to minimise the time between when the silage is removed from the silage face and when it is consumed by the stock. In situations where it is hard to achieve all the above, or where the silage is still heating, seriously consider using an inoculant which inhibits mould and yeast growth at feed out.