Animal nutrition - silage Flashcards by Laura Westman

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)

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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)

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Aerobic phase of ensiling involves (2)

A. intracellular respiration (associated with plant enzyme activity)

B. activity of aerobic bacteria

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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.

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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%)

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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

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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

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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.

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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

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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.

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Day 1 of ensiling

Intracellular respiration forms forms CO2, H2O and heat

pH 6.0
T 21’ C

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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

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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

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Days 4-7 of ensiling

only the lactic acid proceeds
Temperature in silage begins to fall

pH 4.4
T 25’C

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Days 8-21 of ensiling

Lactic acid productions continues
Silage pH decreases and becomes stable

pH 4.2
T 22’C

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Days 21+ of ensiling

Bacterial activity stops
Silage is stable until opening

pH 4.0
T 21’C

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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.

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Ensilage enhancing additives (3)

Biological additives (inoculants)
Energy-rich additives (molasses, whey, etc.) (promote fermentation of natural bacteria)
Chemical additives (acids, salts)

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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

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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

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appropriate pH of silage

depending on the DM 4.1…4.7

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buffering capacity in regard to silage refers to

a plant’s resistance to pH changes

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High silage pH indicates

restricted fermentation, which causes unwanted fermentation

this refers to spoilage

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leguminous (clover, lucerne) silage pH is ?
compared to grass silage

leguminous silage pH is higher compare to grass silage

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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

Animal nutrition - silage Flashcards

(60 cards)