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Production of quality silage

Prepared by Lesley Irvine, Tasmanian Institute of Agriculture 

The quality of silage made will determine animal intakes and their growth or production response. In general, it costs just as much to make a tonne of good quality silage as it does to make  poor quality silage. There are a number of steps in the silage making process where you can make a big difference in the quality of the end product.

Stage of growth
Whether it is pasture or a crop, there is a ‘right' time to cut that will maximise the quality of silage. With pasture, this is when the seed heads first start to appear. At this stage, the metabolisable energy of the pasture should still be around 10 megajoules (MJ) per kilogram of dry-matter (DM). Leaving the pasture for longer before cutting, will result in a greater quantity of silage but the quality of that silage will not have the same growth response in stock as the higher quality product. Forage quality will usually decline by 0.25-0.6 MJ ME/kg DM per week of delay in silage harvest.

Wilting

Forage must be wilted before ensiling to ensure good silage fermentation and to eliminate effluent losses. There are two aims with wilting. The first is to wilt the silage to the correct dry-matter, the second is to do this as quickly as possible. The target dry-matter content can vary for different crops but in general it is 30-40% for forage harvested silage (stored in a pit or stack) and 35-50% dry-matter for baled
silage.

To get a fast wilt:

  • start cutting of a morning as soon as the dew lifts
  • follow the mower as soon as possible (within ½ - 1hour) with a tedder.

The aim should be to ensile silage within 24-48 hours of cutting. The longer it takes to wilt a silage, the greater the dry-matter and quality losses there will be. The dry-matter of a forage can be tested in the field by the hand squeeze method or it can be dried in a microwave (always include mug of water in the microwave with the sample to stop it from catching on fire).

Storage
Bunkers, pits and stacks

  • Evenly spread each load to less than 30 cm thick and make sure it is well compacted to reduce the amount of air that is trapped.
  • Roll slowly to allow the tractor weight to compress the silage.
  • If the forage is too dry and difficult to compact, alternate with loads of freshly cut or partially wilted forage.
  • Filling of each storage unit should be completed within 3 days. Cover the silage at the end of each day's filling to reduce quality losses.
  • Seal the silage as soon as filling and compaction is completed using plastic specifically manufactured for silage making.
  • Overlap any joins by 50 cm and seal them with silage tape. Alternatively, overlap by 1 metre and lay tyres or sandbags along the joins.
  • Bury the edges of the plastic in the ground to prevent air from entering.
  • Weigh the plastic down well, usually done with tyres and/or soil.
  • Check for and repair any holes in the plastic with silage tape.
     

Bales (individually wrapped)

  • Wrap the bales as soon as possible after baling (within 2 hours).
  • Bales must be tight and of even shape otherwise the plastic does not fit well and air will be trapped in with the bale.
  • Wrap bales using the 2+2 system, with 50% overlap, ensuring there is a minimum covering of four layers of plastic over the entire bale. Having less than 4 layers over the entire surface of the bale will let air enter and result in mould growth.
  • Store round bales on the flat surface - the flat surface has the thickest layer of plastic and it is best to have this exposed to the sun and will also reduce damage from sticks and grubs on the ground.
  • Check for and repair any holes in the plastic with silage tape.