Livestock production: The secret to making good silage

Question: I would like to learn how to make silage to feed my animals. Can you help, please?

Making silage requires a lot of labour and attention, but if it is tackled with care, a short period of hard work can prove to be worthwhile all year long.

Silage can be defined simply as the product formed through the controlled fermentation of a crop that has a relatively high moisture content.

Although this cannot improve the nutritional value of the crop, it’s still the best method of preserving forage. At present silage is the main roughage component of most dairy rations.

The purpose of this article is to take a brief look at the some of the most important factors that can influence the quality of the end product:
The correct cutting stage. Oats, the most popular silage crop in, for instance, the Western Cape in South Africa, must be harvested during the milk stage. Harvesting too late can have a negative effect on the digestibility of the final product.

Wilting is important to ensure that the material is ensiled at the correct moisture content. Making silage from too wet material is detrimental as it creates a favourable environment for the growth of bacteria, mainly clostridia, but also enterobacteria.

Clostridia forms butyric acid which makes the silage unpalatable and can thus have a negative effect on feed intake. Ideally, oat silage should be harvested at 30% dry matter.

The average dry matter content of oats at the correct cutting stage is normally slightly lower (approximately 25% dry matter). This can be increased by leaving the harvested material in the field for a couple of hours (maximum 48 hours) to wilt.

If the material is left to wilt for too long, some nutrients, especially water-soluble carbohydrates and proteins which are broken down, can be lost. Making silage from material that is too dry is also undesirable as it makes good compaction more difficult and prevents quick fermentation.

The importance of good compaction of silage cannot be overemphasised. It is necessary to remove as much of the oxygen trapped in the material as possible. As long as oxygen is available, it will stimulate the activity of microbes like clostridia and enterobacteria, which produce unfavourable products, destroy nutrients and cause material to decay.

Fungi, which occur naturally in soil and on plants, grow in the presence of oxygen. They produce mycotoxins which can be very harmful to livestock.

Lactic acid bacteria, on the other hand, are anaerobic organisms and function in the absence of oxygen. These bacteria ferment water-soluble carbohydrates to make lactic acid, the most important preservative of silage, as it decreases the pH of the silage.

Inoculants can be used effectively to promote the formation of lactic acid for improved preservation of the silage. Inoculants contain one or more types of bacteria which speed up the process of fermentation and decrease pH rapidly to below pH = 4.

Some inoculants also contain bacteria that can lengthen the “lifetime” of the silage. Such inoculants should be considered if the face of the bunker is exposed to air for long periods or if silage is taken out frequently and left in a heap from where it is used.

The correct application of the inoculant is very important. If it is not applied correctly or at the correct dosage, it may not be effective. The best way of applying an inoculant is by fixing an applicator onto the harvester. Always ensure that the applicator is calibrated correctly. Though it is common practice to apply inoculant by hand, it is certainly not recommended or effective.

Sealing the silage bunker is another very important factor in ensuring good-quality forage at the end of the day. It keeps oxygen out of the preserved material and prevents the activity of harmful aerobic micro-organisms. Well-sealed silage can be kept for a number of years, depending on the type of silage and the type of packing.


  • Silage can be used within a few weeks.
  • The overall management of the silage bunker is very important.
  • Exposure to oxygen and water must be limited as far as possible.
  • The dimensions of the bunker must be planned according to the size and requirements of the operation.
  • A minimum of 20 cm of silage must be fed out per day and only enough silage for one feeding should be taken out at a time.
  • The silage must be taken off as evenly as possible to prevent cracks in the face of the bunker. Air is able to penetrate through these cracks and spoil the rest of the silage.


  • The chopping length of the silage material is important.
  • It is more difficult to compact silage effectively if it is cut too long.
  • Silage that has a shorter particle length is also known to improve feed intake.
  • Good compaction can be achieved by making the tractor doing the job as heavy as possible. The heavier the tractor and the narrower the wheels, the better.
  • Material spread out in thin layers can be compacted more efficiently than if it is dumped in a heap.
  • Allow enough time for good compaction.
  • Remember that it is always important to limit the surface area that is in contact with air.
  • For this reason it is preferable to “wedge” material in a bunker silo rather than packing it in long, flat layers.


  • Good drainage is important to prevent nutrients, especially water-soluble ones, from being lost.
  • Water should not be able to run into the bunker and water that does get into the bunker should be able to drain out.
  • If silage is made with the right dry matter content, very little – if any – water should run out of the bunker.
  • A thick layer of sand or dry manure placed on top of the plastic works better than tyres to seal silage bunkers.
  • If tyres are used, make sure there are enough.
  • Placing salt, at 3 kg per square metre, underneath the plastic also works well.

By following these guidelines, you should be able to enjoy the advantages of good-quality silage.

Also read:
Trace elements for ruminants
How to supplement trace elements correctly
Overcome nutrient deficiencies in goats and sheep

  • This article was written by Jeanne Griffiths and first appeared in Farming SA.

share this