Animal nutrition - silage Flashcards
2 Fundamentals of the preparation of a stable
silage are
–removal of atmospheric oxygen (anaerobic environment)
–lactic fermentation resulting in lactic acid (an acidic environment)
Biological principles of ensiling (4)
- Aerobic phase (enzyme & bacterial activity)
- Anaerobic phase (glycolysis -> use of water soluble sugars by anaerobic LAB)
- Stable phase
- Feed out phase (secondary aerobic fermentation starts after opening the silo)
- Aerobic phase of ensiling involves (2)
A. intracellular respiration (associated with plant enzyme activity)
B. activity of aerobic bacteria
The intracellular respsiration in the aerobic phase of ensiling is
the process of oxidative decomposition (burning) of plant organic matter and ATP production
- Dead plant cells do not use ATP and this becomes heat.
factors affecting Intracellular respiration (5)
- Temperature (enzymes are active at +30…+50’C, but will be
destroyed at +70…+80’C) - Presence of oxygen -> precondition
- Presence of carbon dioxide (high concentration stops respiration)
- Concentration of hydrogen ions (pH) (high concentration (low pH) stops respiration)
- Silage dry matter content (plants stops respiration when the dry matter content is 50…60%)
The Aerobic phase of ensiling lasts until (2)
the oxygen runs out, or environmental pH drops low enough that the aerobic bacteria are not able to survive it
In the Anaerobic phase of ensiling, Anaerobic lactic acid bacteria start
producing lactic acid (or other) via glycolysis by hydrolyzing sugars
substrate - dependent on the type of bacteria
which type of bacteria produce lactic acid?
how efficient are they?
homofermentative bacteria
▪ they produce two moles lactic acid from one mole glucose or from one mole fructose
- Homofermentative bacteria are more efficient compared to heterofermentative bacteria.
what type of bacteria produce acids other than lactic?
how efficient are they?
heterofermentative bacteria can produce other acids in addition to lactic acid, such as
acetic acid
▪ they produce only one mole lactic acid from one mole glucose or from three moles
fructose
- Stable phase of ensiling
As a consequence of hermetical closure of silo/silage…?
hermetical = Completely sealed, especially against the escape or entry of air.
due to low pH the anaerobic bacteria also die and are therefore no longer active, and the silage remains stable.
- This silage can be preserved for years.
Day 1 of ensiling
Intracellular respiration forms forms CO2, H2O and heat
pH 6.0
T 21’ C
Day 2 of ensiling
Beginning of fermentation
Formation of acetic acid
Intracellular respiration begins to stop and heat production decreases
pH 5.0
T 27…32’C
Day 3 of ensiling
lactic acid formation begins
Acetic acid production continues
Intracellular respiration begins to stop and heat production decreases
pH 4.7
T 27…32’C
Days 4-7 of ensiling
only the lactic acid proceeds
Temperature in silage begins to fall
pH 4.4
T 25’C
Days 8-21 of ensiling
Lactic acid productions continues
Silage pH decreases and becomes stable
pH 4.2
T 22’C
Days 21+ of ensiling
Bacterial activity stops
Silage is stable until opening
pH 4.0
T 21’C
- Feed out phase – secondary fermentation refers to?
After opening the silo the silage surface comes into contact with oxygen.
Due to this, aerobic bacteria (and top-growing yeasts) start to act and utilise the silage
lactic acid and residual sugars for life processes.
pH starts to rise, this activates the growth of other aerobic microbes, and due to this,
silage heats up and spoils.
This can also cause the spoilage of mixed feed.
Ensilage enhancing additives (3)
- Biological additives (inoculants)
- Energy-rich additives (molasses, whey, etc.) (promote fermentation of natural bacteria)
- Chemical additives (acids, salts)
name some ensilage enhancing biological additives and what they do
- Biological additives (inoculants):
– homofermentative bacteria
– heterofermentative bacteria
▪ these bacteria can start and/or end the fermentation
▪ may use together with fibre-degrading enzymes
Silage fermentation quality indicators (7)
pH
lactic acid content
acetic acid content
proprionic acid conent
butyric acid content
Ammonia nitrogen content of total nitrogen
Biogenic amines
appropriate pH of silage
depending on the DM 4.1…4.7
buffering capacity in regard to silage refers to
a plant’s resistance to pH changes
High silage pH indicates
restricted fermentation, which causes unwanted fermentation
this refers to spoilage
leguminous (clover, lucerne) silage pH is ?
compared to grass silage
leguminous silage pH is higher compare to grass silage