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due to low pH the anaerobic bacteria also die and are therefore no longer active, and the silage remains stable.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
Total amounts of acid is key to silage intake
acidity affects palatability
– if acids are > 130 (150) g/kg DM, intake starts to
decrease
– if this is > 250 g/kg DM, cows stop eating
Lactic acid in silage should be between (how many g per kg DM)
Lactic acid content 30…100/150 g/kg in DM
must constitute 65…70% of total acid amount in silage
What is the strongest acid in silage
Lactic acid is the strongest acid in silage and due to this it is closely related to pH.
must constitute 65…70% of total acid amount
Lactic acid content indicates whether
the microbial processes in silage have ended meaning it shows how stable the silage is
Lactic acid is a feed source for
other microbes in the silage, like clostridia & top-growing yeasts
Lactic acid is converted in the rumen by microbes to
propionate
how do clostridia affect silgae pH
clostridia are anaerobes that start to shift pH up while silage is still closed
can lead to spoilage
how do top-growing yeasts affect silage pH
top-growing yeasts are aerobes that start to shift pH up, when silage is opened
can lead to spoilage
Acetic acid content in silage should be between (how many g per kg DM)
Acetic acid content <20…30 g/kg in DM so quite low.
Typically, a high acetate content decreases the
silage palatability.
Propionic acid content in silage should be between (how many g per kg DM)
Propionic acid content <1 g/kg in DM.
content is usually very low, except in very wet
silages (DM <20%)
in silage, Propionic acid is produced by
propionic acid bacteria, whose competitiveness is very low in silages.
does not cause problems for animal health or
rumen digestion but decreases feed palatability
Butyric acid content in silage should be between (how many g per kg DM)
Butyric acid content 0…0,5 g/kg in DM
High butyric acid content in silage indicates? (3)
–shows an undesirable fermentation in silage
–more than 5 g/kg in the DM, indicates that
this is caused by the fermentation of clostridia
–associated with a high ammonia-N content,
whhich is a consequence of intensive proteolysis
silage containing plenty of butyric acid is
generally low in energy, and easily digestible carbohydrates are degraded
Good silage does not contain butyric acid but if
there is, the content must remain below 0.5 g/kg.
How does butyric acid get into silage and what does it indicate?
Produced by anaerobic clostridia “ clostridial fermentation” (called also butyric acid bacteria) -> get into the silage during ensiling of contaminated grasses.
the presence of butyric acid indicates that undesirable fermentation occured
Clostridia form spores to lie dormant, can reawaken in the anaerobic silage environment.
How do clostridia get into the ensiling material? (2)
Main sources are soil and manure.
Lactic acid bacteria outcompete
clostridia
Clostridia can be divided into:
– saccharolytic clostridia or sugar and lactic acid-
consuming bacteria
– proteolytic clostridia or plant proteins (AAs)-
consuming bacteria
saccharolytic clostridia consume lactic acid and produce
consume sugar or two lactic acids to form butyric acid + 2CO2 + 2H2O
proteolytic clostridia consume plant proteins/amino acids and produce
▪ form amines, ammonia, acetate, propionate etc.
▪ biogenic amines and acids formed reduce palatability! not good.
Characteristics of butyric acid-(clostridia) rich silage (7)
– dark, wet and slimy
– rancid odour
– poor palatability
– pH > 5.0
– ammonia-nitrogentotalying >15%
– high butyric acid content
– dry matter content < 30%
Zearalenone & deoxynivalenol are both?
mycotoxins
What can we do if the silage already contains butyric acid? (3)
replace (don’t feed in times of peak lactation)
dilute (feed in assocciation with appropriate-acid-content feed)
or remove from feeding completely
Problems which can appear when feeding butyrate-rich silage (4)
- Decreases feed intake (higher content of NH3-nitrogen and biogenic amines)
- Increases risk of alimentary (secondary)
ketosis - Increases risk of diseases caused by clostridia
- Milk contamination with spore-forming clostridia
Ammonia-nitrogen portion of total nitrogen content of silage should be
< 7%
Where does ammonia come from in silage?
a product of protein hydrolysis
forms about 20% of total protein hydrolysis products
biogenic amines are
are protein degradation products, resulting
from the decarboxylation of AAs by clostridia so due to spoilage
they are bad metabolites that can be found in silage
they have an unpleasant odour, toxic compounds which may end up in the milk
consequences of biogenic amines in silage
reduced palatabililty, inhibit rumen contractions
cause metabolic diseases (laminitis), fertility
problems, and also mortality
cows convert butyric acid to what in the rumen
to the ketone body d beta-hydroxybutyrate
too much butyric acid can cause what metabolic disorder in cattle
how much acid causes subclinical an dclinical ketosis?
alimentary ketosis (so secondary ketosis)
– subclinical ketosis, if + 50… 100g of butyrate per day
– clinical ketosis, if + 200g of butyrate per day
most common species of clostridium found in silage
C. perfringens type A
can cause Jejunal haemorrhagic syndrome,
abomasum ulcers, gas gangrene, sudden death
why can concentrates NOT contribute to over 60% of the diet of cattle?
risk of rumen acidosis
Cost-effectiveness threshold is also significantly
lower.
Which material is the most difficult to ensile?
A. Red clover
B. Maize
C. Grass
D. Mix of lucerne and grass (50:50)
A. Red clover
because of its high buffering capacity
Which microorganisms should dominate during the ensiling process?
A. Butyric acid bacteria or clostridia
B. Acetic acid bacteria
C. Lactic acid bacteria
D. Yeasts
C. Lactic acid bacteria
How does higher dry matter content of ensiled
material affect the ensiling process?
A. Increases buffering capacity and sugar content
B. Increases buffering capacity and decreases sugar content
C. Decreases buffering capacity and sugar content
D. Decreases buffering capacity and increases sugar content
D. Decreases buffering capacity and increases sugar content
higher dry matter affects the ensiling process positively by lowering buffering capacity?
drying increases the nutrients such as water soluble sugars
Which acid produced during fermentation affects
silage acidity (pH) the most?
A. Butyric acid
B. Propionic acid
C. Lactic acid
D. Acidic acid
C. Lactic acid
