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Producing quality silage

Producing quality silage for livestock is a combination of good management, having the right starting material and a bit of luck when it comes to the weather.  The key to producing ‘quality’ silage is based on:

  1. The time it is cut.  There needs to be equilibrium between quantity and quality.  A large dairy client in Warrnambool producing a lot of silage suggests that the optimal time to cut is ~3000kg DM/Ha.  In this scenario, you will reduce quantity but improve quality.  You will need to monitor pasture growth and endeavour to cut before the plant begins to ‘run up.’

    Source: Dairy Australia - Top Fodder: Successful Silage manual (2003)
      Early Mid Late
    Days from first cut - 9 17
    Digestibility (%) 71.3 67.2 64.2
    Intake (kg DM/day) 7.2 7.0 6.7
    LW gain (kg/day) 0.92 0.78 0.6
    Yield (t/Ha) 12.9 12.8 13.5

     
  2. The speed at which you can wilt the pasture to the desired DM content without suffering quality or dry matter losses.  In a pit silage scenario, aim for 30-35% DM for long chopped and 30-40% DM for precision chopped silage.  If the product is too wet it can result in loss of nutrients and effluent production.  If the product is too dry, it can cause heating and mould growth as the anaerobic conditions are reduced.

    Source: Dairy Australia - Top Fodder: Successful Silage manual (2003)
    Growth Stage ME (MJ/kg DM) CP (% DM) Yield (t DM/ha)
    Early (vegetative) 10 – 11 15 – 25 1.5 – 3.0
    Mid (head emergence) 9.5 – 11 12 – 22 2.5 – 4.0
    Late (flowering) 8.5 – 10 10 – 20 2.5 – 5.0


    The quality of silage can be assessed by its smell. The following are characteristics of product quality, listed from the least to the most desirable:

    1. Musty/mouldy/composty = poor compaction
    2. Tobacco/caramel/burnt sugar = heat damaged
    3. Vinegar = poor fermentation
      1. Common with low DM and low sugar silages
    4. Sweet/fruity = > % yeasts present, high ethanol levels
    5. Slightly sweet = heavily wilted low fermentation
    6. Mild/acidic/yoghurt = normal
  3. The type of plant material you start with is important.  Unimproved or native grass will flower earlier than improved perennials.  As plants mature, they lose quality and fibre content increases.
    1. Too stalky.  Increases fibre and reduces compaction causing incorrect fermentation
    2. Animal intake is reduced compared to pasture silage
    3. Quality of cereal silage is very much dependant on the number of grain heads.  Usually cereal silages are lower in both energy and protein compared to pasture silage.

      quality of silageSource: Adapted from Bell (2000)

       
  4. Weather effects. Rain is bad news and washes WSC’s from the wilted pasture.  This reduces the amount of substrate available for fermentation bacteria to do their job, ultimately resulting in a lower quality end product.

To ensure you’ll meet all requirements, aim for the following:

Target:
> 12% CP for pasture silage (to satisfy stock requirements)
> 18% CP for legume silage (vetch/clover/lucerne)
> 9.5 ME for pasture silage

Dr Steve Cotton is an agricultural consultant working with Livestock Logic, and specialising in drench and vaccination programs for sheep and cattle, nutritional programs for livestock and manager of the Feed and Worm Logic laboratory.

Livestock Logic offers clients evidence based research, knowledge and experience in all aspects of animal and pasture management, specialising in feed testing, nutrition, veterinary advice and diagnostics.  With Australia's largest worm egg counting laboratory and drench resistance testing facility, livestock health and productivity is our focus."

Read more about Steve and Livestock Logic at http://www.livestocklogic.com.au/steve-cotton/
Dr Steve Cotton B.Ag Sci (Hons), PhD. Livestock Logic, Livestock Logic, Hamilton, Vic. E: s.cotton@livestocklogic.com.au