| |
|
|
|
| |
|
|
|
MAKING OF
SILAGE
|
Silage is the feedstuff resulting from the
preservation of green forage crops by
acidification. The first phase is the
aerobic phase, which occurs in the presence
of oxygen (air). The oxygen that is present
in the forage, as it is placed into storage,
is consumed by the plant material through
the process of respiration. Under aerobic
conditions, plant enzymes and microorganisms
consume oxygen and burn up plant
water-soluble carbohydrates (sugars),
producing carbon dioxide and heat. The first
phase should be as brief as possible to
maintain the quality of the silage.
Excessive aerobic fermentation reduces the
energy content of the silage and may cause
heat damage to proteins.
The second anaerobic phase begins when
available oxygen is used up by respiration
and aerobic bacteria cease to function.
Anaerobic bacteria begin to multiply and the
fermentation process begins. The
lactobacilli produce lactic acid from the
fermented plant material which lowers the pH
of the silage. Fermentation completely
ceases after three to four weeks when the pH
becomes so low that all microbial growth is
inhibited.
The ensiling and storage system's main
functions are to exclude air during the
ensiling process and to prevent air from
entering the silage during storage.
Limiting air present in the silage will
enhance feed quality and reduce spoilage.
|
|
|
SILO TYPES
|
Horizontal Silos
There are two types of horizontal silos -
below ground level (i.e., pit or trench) and
above ground (i.e. bunker and stack). The
main advantage of horizontal silos is their
low capital cost and suitability to feeding
livestock in widely separated pens.
Trench silos
Are usually dug into a slope with the
"downhill" end open for drainage and access.
Bunker silos
are used in flat areas unsuitable for trench
silos. Above-ground walls are constructed
using concrete, earth or wood and braced
with timbers or concrete buttresses.
The correct height and width to make a silo
depends on daily silage usage based on the
removal of a minimum of 10 cm (4 in.) per
day from the silage face. Removing less
silage leads to spoilage or freezing
problems. The silo should be as high as
possible to minimize silo width, thereby
minimizing surface spoilage. Increased
silage height aids in packing.
• Silo Length depends on the total silage
needed annually.
• Capacities are dependent on average
densities of silage. Silage density
increases with increasing moisture content,
shorter cut length packed silage depth and
amount of packing.
|
DETERMINING MOISTURE CONTENT OF FORAGE
|
|
a) Using a Microwave Oven
1. Cut a representative cross-section of
forage from the windrow.
2. Cut into 0.6 cm (1/4 in.) pieces.
3. Weigh 100 grams of material and place on
a paper plate or bag.
4. Spread sample out evenly and place in
microwave over on high heat for three to
four minutes.
5. Weigh sample and record weight.
6. Stir sample and place in microwave oven
on high heat for one minute. Reweigh and
record weight.
7. Repeat step six until weight loss is less
than one gram. This is the dry weight.
Calculation: wet wt. grams - dry wt. grams
/100 = percent moisture
b) by Hand
Method |
|
Forage squeezed in hand |
Moisture % |
|
Water easily squeezed out and material
holds shape |
80+ |
|
Water can just be squeezed out and
material holds shape |
75-80 |
|
Little or no water can be squeezed out
but material holds shape |
70-75 |
|
No water can be squeezed out and
material falls apart slowly |
60-70 |
|
No water can be squeezed out and
material falls apart rapidly |
60 or less |
|
|
|
|
 |
|
|
SILAGE ADDITIVES
|
There are three categories of Silage
additives
I. Stimulants of fermentation (microbial
inoculants, enzymes, fermentable
substrates),
II. Inhibitors of fermentation (acids, other
preservatives), and
III. Nutrient additives (ammonia and urea).
|
|
STIMULANTS OF FERMENTATION
|
a) LAB: Natural populations of lactic
acid bacteria (LAB) on plant material are
often low in number and heterofermentative .
The concept of adding a microbial inoculant
to silage was to add fast growing
homofermentative lactic acid bacteria (hoLAB)
in order to dominate the fermentation
resulting in a higher quality silage. The
organism's from microbial inoculants must be
present in sufficient numbers to effectively
dominate the fermentation. Thus the most
commonly recommended inoculation rate
supplies 100,000 (or 1 x 105) organisms per
gm of wet forage. Most microbial inoculants
are available in powder or granular form.
Use a metered liquid sprayer to evenly
disperse the inoculant's on the forage.
Unused liquids should be discarded after a
period of 24 to 48 h because bacterial
numbers begin to decline. Application to
forage at the chopper is highly recommended
in order to maximize the time that
microorganisms have in contact with
fermentable substrates. Inoculants applied
in a liquid may be more advantageous since
bacteria are added with their own moisture
to help speed up fermentation. Storage is an
important aspect of a high quality
inoculant's that contains live
microorganisms. Inoculants should be kept in
cool dry areas away from direct sunlight.
Moisture, oxygen and sunlight will decrease
stability of inoculants. Opened bags of
inoculants should be used as soon as
possible.
Recently, Lactobacillus buchneri, a
heterolactic bacteria capable of producing
lactic and acetic acid, has been included as
an inoculant's for improving the aerobic
stability of silages. Aerobic stability was
markedly enhanced and improved with
increasing inoculation rate.
b) ENZYME ADDITIVES: A variety of
enzymes, particularly those that digest
plant fiber and starch have used as silages
additives. Silage additives may contain
single enzyme complexes, combinations of
enzyme complexes and combinations of enzyme
complexes and LAB. Plant fiber-digesting
enzymes (celluloses and hemicellulases) are
the most widely used enzyme additives.
There are two primary reasons for adding
fiber-digesting enzymes to silage. First
these enzymes could partially digest the
plant cell walls (cellulose and
hemicellulose) yielding soluble sugars which
could be fermented by LAB to lower the
silage pH. This would stimulate silage
fermentation and improve fermentation
quality by increasing the rate and extent of
decline in pH, increasing the concentration
of lactic acid, improving the lactic acid:
acetic acid ratio (which is indicative of
greater efficiency of fermentation), and
hence reduce DM losses. A faster decline in
pH would also limit degradation and
diminution of forage proteins and reduce
ammonia production. Second, partial
digestion of the plant cell wall may improve
the rate and/or extent of digestibility. In
order for the first event to take place the
rate of cellulose hydrolysis must coincide.
MOLASSES. Molasses has been used as a
fermentation stimulant. Molasses is a
by-product of the sugar-cane and sugar-beet
industries and contains 79% soluble
carbohydrates; 45 to 50%, of which sucrose
is the main component. Molasses provides a
relatively cheap source of fermentable
carbohydrate for lactic acid bacteria and
has been applied at a rate of 40-80 lb per
ton of fresh forage. |
|
|
INHIBITORS OF FERMENTATION
|
|
PROP IONIC ACID: prop ionic acid has
the greatest antimycotic activity. The
antimycotic effect of prop ionic acid is
enhanced as pH declines, making it an ideal
candidate for improving the aerobic
stability of corn silage where pH is low.
Aerobic stability was improved when large
amounts of prop ionic acid (1 to 2% of the
DM) were added to silage, but the high
percentage of acid often restricted
fermentation in these cases. Prop ionic acid
is difficult to handle because it is
corrosive. Hence the acid salts, e.g.,
calcium, sodium and ammonium propionate have
been used |
|
|
NUTRIENT ADDITIVES
|
a) AMMONIA : additions resulted in a)
addition of an economical source of crude
protein b) prolonged bunk life during
feeding (c) less molding and heating during
ensiling; and d) decreased protein
degradation in the silo .
b) UREA : has been added to corn silage as
an economical source of crude protein. A
beneficial effect of urea on improved bunk
life and decrease in proteolysis has not
been totally substantiated.
Ammonia reduces plant proteolysis. Although
fermentation is generally stimulated by
ammonia, the ensiling processes is prolonged
because of ammonia buffering effect
resulting in greater total acid production
and inconsistent effects on DM recovery.
Ammonia can be added at the chopper, blower,
bagger or bunk. In addition, molasses and
minerals can be added in these solutions.
Application of anhydrous ammonia should be
at approximately 1 kg of N per 100 kg of
forage DM This will increase crude protein
from about 8 to 12.5% on a dry matter basis.
Anhydrous ammonia should not be added.
Water- ammonia mixes or molasses-ammonia
mixes should be used. Silage additives can
be useful tools to improve silage quality
and animal performance, however, they are
not replacements for good management
practices. Care should be taken when
choosing a silage additive.
|
SAFETY IN SILAGE STORAGE
|
When nitrates are degraded in the ensiling
process, nitrogen oxides are formed as
products of microbial metabolism. The N02
which results when nitrogen monoxide
contacts air is often called "silo gas" and
is highly toxic to man and animals when
present in concentrations greater than 10 to
25 ppm. Always assume that both C02, and
N02, are present in a tower silo and if
exposure is not fatal, respiratory tract
damage can occur. Relapses are common after
apparent recovery.
Since N02 is heavier than air, the brown gas
is sometimes clearly visible inside silos or
around silo openings. Most of the N02 is
evolved from the silage in the first week of
fermentation, with production peaking at two
to three days after ensiling. Production of
N02 essentially stops after the material has
been in the silo for more than 10 days. .
|
|
|
FERMENTATION
|
Fermentation in the silo can be a very
uncontrolled process leading to less than
optimal preservation of nutrients. Silage
additives have been used to improve the
ensiling process. Silage fermentation
can be divided into 4 phases.
1) The first phase is characterized by the
presence of oxygen after forage is chopped
and packed in the silo. Plant respiration
continues for several hours (and perhaps
days if silage is poorly packed) and plant
enzymes (e.g., proteases) are active until
oxygen is used up. excess oxygen can lead to
unwanted protein breakdown and excessive
heating and growth of yeasts and molds that
are undesirable. Oxygen must be eliminated
by quick packing, even distribution of
forage, chopping to a correct length for
optimal fermentation.
2) The second phase of silage under
anaerobic conditions is dominated by
microbial activity. Fermentation is
controlled primarily by: a) type of
microorganisms that dominate the
fermentation, b) available substrate (waster
soluble carbohydrates) for microbial growth,
and c) moisture content of the crop. During
this phase, lactic acid producing bacteria
(LAB) should utilize water soluble
carbohydrates to produce lactic acid; the
primary acid responsible for decreasing the
pH in silage. Undesirable fermentations from
microorganisms such as Enterobacteria and
Clostridia can dominate if the pH does not
drop rapidly.
3) In third phase lack of oxygen prevents
the growth of yeast and molds and low pH
prevents the growth of most bacteria. Silage
can be kept for prolonged periods of time if
these conditions prevail.
4) Fourth stage is, feed out and exposure to
air. Airtight silos and removal of
sufficient silage during feed-out can
prevent aerobic spoilage.
|
|
|
Amounts of Common Fermentation End Products
in Silages.
|
|
|
| |
Alfalfa Silage |
Corn Silage |
|
Item |
30 - 35% DM |
35 - 40% DM |
|
PH |
4.3-4.5 |
3.7 -4.2 |
|
Lactic acid |
% 7 - 8 |
4 - 7 |
|
Acetic acid |
% 2-3 |
1-3 |
|
Propionic acid |
% <0.5 |
<0.1 |
|
Butyric acid |
% <0.5 |
0 |
|
Ethanol |
% 0.5 - 1.0 |
1-3 |
|
Ammonia-N% of |
10-15 |
5 - 7 |
CP
|
|
|
Good Quality Silage
|
Sheep Eating Silage
|
Dr. V. ASHOK KUMAR,
Email. drvakadah@gmail.com |
 |
|
|
|
|
|
|
