Phases of Silage making

Silage is a form of feed that is fermented under airtight conditions in the presence of anaerobic bacteria that converts all the soluble sugar into Organic acids.
It takes about 25-30 days (without inoculants). The ideal pH of silage ranges between 3.75-4.25. 
It enhances the flavor, and digestibility and can be preserved for a very long time. That’s why it is also named an animal’s pickle.

The moisture content in silage is 65-75%. In case of Hay, moisture should be less than 15%.

Silage making
Silage compressing

Phases of silage making

There are four phases of silage-making:

  1. Aerobic phase 
  2. Anaerobic phase 
  3. Stable phase 
  4. Feedout/Deterioration phase

1). Aerobic phase

This phase starts immediately after putting the crop in a silo/bunker.

In this stage, Enterobacteria is present which consumes sugar and converts it into CO2 and H2O and releases heat. While the plant leaves consume Oxygen and produce heat and water because of respiration. which ultimately raises the temperature. If excess heat is generated, then it may lead to protein deterioration which affects the nutrient availability and digestibility.

C6H12O6  + 6O2 ———→    6CO2 + 6H2O + HEAT 

It continues until all the Oxygen is eliminated and the anaerobic condition is maintained. Its duration is about 24 Hours.

2. Anaerobic phase (fermentation phase)

This phase starts right after the formation of an anaerobic environment. In this phase, the bacteria start to act and convert the sugar into acetic acid. In this stage, the pH goes down to 5.5. 

It has further 2 Steps 

(i). Acetic acid production 

Firstly, the acetic acid-producing bacteria comes and starts to produce acetic acid which as a result decreases the pH to about 5.0-5.5 and makes an environment for the growth of LAB. Acetic acid also acts as a preservative and increases aerobic stability. It lasts about only 24-72 hours (about 3 days). 

(ii). Lactic acid production 

Now, Lactic acid-producing bacteria come and start to produce Lactic acid. It is the main organic acid in silage It lasts about 21 Days.  

3. Stable phase

After 21 Days the silage process is completed, and all the bacterial action ceases and an acidic environment is formed. It lasts until the silage is opened

4. Feed out phase

Once the silage is opened it should be used immediately according to its aerobic stability otherwise it starts to deteriorate. Poor handling and compromise on anaerobic conditions lead to the growth of mold, yeasts, and even maggots. 

Silage making process end
Silage after opened

Aerobic Stability:

The length of time that silage remains cool and doesn’t spoil after it is exposed to air.

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Age of Silage
0-2 Days
2-3 days
3-21 days
21 days to onward
Until opened
Activity
Cellular Respiration, Heat, Water, and CO2 production
Acetic acid production
Lactic acid production
Bacterial activity stops and preserves
Content
Temp changes
69-72 F
80-84 F
70 F
70 F
84 F
PH changes
6.5-6.0
6.0-5.0
5.0-4.0
4.0
4.0-7.0
Produced
Heat, Water and CO2
Acetic acid, Heat
Lactic acid
Content
Mold, Yeast, and maggots activity.

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