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Guide 20
Tom Ryan
Teagasc farm buildings specialist
Silage waste occurs throughout the whole process of silage making from harvesting to ensiling, covering and right through to
feed out. Some farms produce quality, well preserved silage with virtually no visible waste year in year out, while others make
silage which is hit or miss, with a lot of visible waste on top and at the sides. What di erentiates those that have consistently
very little waste from the others is attention to detail
The yield and quality of harvested grass can be quite di erent
from the potential yield and quality. This can be due to several
factors including: rough areas at gaps and around headlands;
soft spots in the field needing drainage; obstacles left lying
around; low yields due to poor fertility and lime shortage;
inaccurate fertiliser spreading; predominance of old grasses
and weeds in need of reseeding; and harvesting losses in the
pickup process.
These problems generally take time and expense to sort
out. The aim should be to wilt, if possible, by cutting with a
conditioner mower and spreading out the grass as much as
possible followed by tedding out the swaths before raking into
windrows before pick-up. Weather permitting, this approach
should ensure that the grass dry matter (DM) is between 27-
32 per cent within 12-24 hours of cutting, thereby eliminating
e uent while concentrating sugars in the grass and aiding
good preservation.
Nowadays, the work rate of modern silage harvesting
equipment is such that upwards of 40 hectares (ha) per day
is easily achieved. Fast filling of silage pits is good; the only
drawback is that the spreading, levelling and consolidating of
grass isn't given enough time. This is more critical in silage pits
being filled with wilted material. It is important to spread out
wilted grass in thin layers and compact it thoroughly.
Cutting too low reduces silage quality. Grass digestibility is
lower in the stems than in the leaves, so anything that increases
the proportion of stem in the ensiled material lowers the
average digestibility. When the load of grass is tipped out in
the yard the colour and the feel of the material gives a good
indication of the ratio of stem to leaf. The extra yield from
cutting lower is small and it comes at the cost of diluting the
quality of the silage.
Older and stemmy crops have lower digestibility. Crops that are
growing for eight to nine weeks will have a dirty butt, a lot of
dead material and very few leaves lower down. As the sward
gets older, the leaves move up the plant. Snails and worms bring
soil into the butt. Cutting too low and ensiling this material will
lower quality and make good preservation di cult. Getting the
cutting height right in crops with six or seven weeks' growth is
much more straightforward than in older or lodged crops. With
lodged crops, the lie of the grass will a ect the cutting operation.
Try to strike a balance. There is probably no other solution than
to adjust down the machine a bit with lodged crops.
Good preservation
Good preservation occurs when lactic acid bacteria, present
on the grass crop, ferments the available sugars to lactic acid.
This lowers the pH which preserves the feed value of the
stored silage. High available sugars and air-free conditions
are necessary for good preservation. Ideal conditions for high
sugars are ryegrass swards, dry sunny weather, cool nights and
mowing in the afternoon.
If air is present, the preservation process will be slow and
ine cient resulting in high DM losses. Air can be present due
to insu cient consolidation, delayed covering or poor sealing.
This often results in poorer preservation in the top third of the
pit and surface waste at the top and sides. There can also be
heating and spoilage on the face at feed out.
Rapid filling, good consolidation and an e ective air-tight
sealing will generally result in a very fast and e cient
Minimising silage waste
Silage pit: heavy tyres on the shoulders are prevented from slipping by tyres tied
with ropes to eliminate air pockets and for extra protection on top. Gravel bags
along the floor at the butt of the pit would have made it perfect. Check all tyres for
damage. Any tyres with bare, rusty wires should be discarded. If these wires break
o and mix with silage the consequences will be dire.