What is silage?

The silage-making process (ensiling) is very old.  It is basically a form of “pickling” something to preserve it.  It was used by the Greeks and Romans and became popular on farms in the late 19th Century.  But you needed a pit or silo, and a lot of labour to feed it out, which meant it was not popular on small farms. With the invention of the baler and plastic wrapping, its popularity has changed dramatically so lifestyle farmers can take advantage of the benefits of silage as a supplementary feed for stock.

Good things about silage

  • You don’t need a hay barn – the wrapped bales or long sausage bag can stand out in the paddock.
  • You can leave the bales where they are going to be fed.
  • The end product is near the original pasture.  You should only lose about 20% of the nutrients in the silage-making process.
  • The high-protein green leaf is maintained.
  • It is a very cost-effective conservation.
  • Now that it’s baled, you can buy and sell it.

Poor things about silage

  • It smells, and some people (and their neighbours) don’t appreciate this.
  • You must ensure good fermentation when making.
  • It’s difficult to cart and feed out without proper equipment.
  • The effluent from silage is an environmental hazard and is lethal to wildlife in waterways, as it eats up oxygen.
  • Silage wrap is now an environmental hazard – it needs to be put in an approved landfill and not burnt or buried on the farm.
  • You can lose up to 30% of the original nutrients if made poorly.
  • Holes in the plastic (even pin holes) can let in air and allow moulds to ruin large areas. Rats love silage bales and so do stock!

What happens in a good silage-making process?

  • You ensile a good quality crop at the right stage.
  • When it is baled or put in a pit, bacterial fermentation starts.
  • This should be in anaerobic conditions – ie. no air. So you must make sure that in a pit the silage is consolidated by rolling all the time it is being filled. With wrapped bales, this is less of a concern as baling consolidates the grass and it is sealed immediately after baling.
  • This allows Lactobacilli and Streptococci present on the plant leaves to feed off the 3-3.5% sugars present. These are the good bacteria that we want. The silage smells sweet and like vinegar (lactic acid).
  • They produce lactic acid, which pickles the crop and prevents undesirable bacteria from growing by causing a rapid rise in acidity (pH).
  • Once at pH of 3.8-4.3, there is stability and the silage is safe.

What happens when things go wrong?

  • There is no consolidation so you get an aerobic fermentation (air gets in).
  • The bacteria form a butyric acid fermentation which really stinks! You will smell ammonia and see moulds.
  • After a while, in the stack or bale, it will look more like tobacco, and is of very little feed value. In fact, the stock probably won’t eat it. The protein has been cooked like a boiled egg and is useless.
  • The bales will shrink to half their original size – a good sign of trouble.

Fermentation guide – smell and texture check

  • Good
    • Yellow or brown-green
    • Sweet acid smell
    • Firm texture
  • Overheated
    • Dark brown-black
    • Burnt caramel- tobacco smell
    • Dry, disintegrated texture
  • Butyric
    • Olive green
    • Evil putrid smell
    • Soft and slimy
  • Mouldy
    • Dark brown with white mould
    • Musty smell
    • Dry, easily broken texture
  • Putrid/rotted
    • Green/black
    • Putrid smell
    • Wet slimy

Making good silage – Key points

  • Select a good rapidly-growing crop high in ryegrass and clover.
  • Cut it at a maximum of 10-15% seed head emergence.
  • Don’t try to ensile short and lush spring pasture.
  • Cut when dry on a sunny day, - not in the rain.
  • Have it cut and conditioned to spread it about to get rapid wilting.
  • Rapid wilting for 12-24 hours to 25-30% Dry Matter will leave good sugar concentrations in the crop.
  • It will also increase Dry Matter and improve feeding value.
  • Get rapid air exclusion in the pit. Seal the pit rapidly.
  • In a pit keep the temperature down below 30C by rolling to stop the plants from respiring and using up their food stores.  Use a pinch bar to make a hole and drop a thermometer (on a string) down the hole to check the temperature.
  • Wrap bales soon after baling and transport them with care to avoid puncturing the wrap.
  • You can add inoculants to encourage the right sort of bacteria fermentation, but in most cases in New Zealand, they are not essential with grass silage.  Discuss this with your silage contractor.