HARVESTED FORAGES
Silage
pp. 267-274
ENSILING
• What is ensiling?
– Storing a forage or grain crop at a
relatively high moisture concentration in
anerobic conditions to have it undergo
fermentation to lactic acid.
– Lactic acid will preserve silage as long as
the silage isn’t exposed to oxygen
WHY ENSILE?
ENSILING
• Goals
– Decrease pH of ensiled crop to <4
– Increase lactic acid concentration of ensiled crop
to >4% of DM
• Requires anerobic conditions
• Avoid
– Molding and heating of crop
• Occurs if forage is exposed to oxygen
• Forage DM% > 60%
– Butyric acid production, protein degradation, and
seepage from silage
• Forage DM% < 30%
– Dependent of forage species
APPROPRIATE MATURITY AND DM
PERCENTAGE FOR ENSILING
Desired for ensiling
Crop
Maturity
DM%
Whole plant
corn
50% milk line stage
on grain
30-40%
Grain or forage
sorghum
Medium dough
stage of grain
30-40%
Small grains
Late boot stage
35-45%
Grasses
Boot stage
40-50%
Requires
wilting
Legumes
Late bud stage
40-50%
Requires
wilting
THE ENSILING PROCESS
THE ENSILING PROCESS
• Aerobic phase
– Organisms
• Plant enzymes
• Aerobic bacteria and yeasts
– Nutrient Metabolism
• Sugars oxidized to CO2
– Changes in forage
• O2 is consumed and CO2 produced
• Temperature increases to 115oF
• Sugars decreased
– Length of change
• Desire < 24 hours
• Extended by:
– Too dry
– Long chop length
– Slow filling
– Poor packing
– No cover
• In extended, results in:
– Excessive heating
» Increased ADIN
• Heterofermentative phase
– Organisms
• Heterofermentative lactic acid bacteria
– Nutrient Metabolism
• Sugars fermented to acetic acid, lactic acid, and CO2
– Changes in forage
• Increased concentration of acetic acid and lactic acid
• pH decreased to 5.0
• Sugars decreased
– Length of change
• Desire < 1 week
• Extended by:
– Forage being too wet
– If pH never drops to 5
» Causes
• Forage too wet
• Inadequate sugars
» Results
• Clostridium bacteria growth
• Butyric acid production
• Protein degradation to NH3 and other forms of
NPN
• Homofermentative phase
– Organisms
• Homofermentative lactic acid bacteria
– Nutrient Metabolism
• Sugars fermented to lactic acid
– Changes in forage
• Increased concentration of lactic acid
– 6 to 8% of DM
• pH decreased to 3.8 to 4.2
• Sugars decreased
– Length of change
• Desire < 2 weeks
• Storage phase
– If not exposed to oxygen
• Forage well-preserved with little change in composition
– If exposed to oxygen
• Growth of aerobic bacteria and mold
– Results in heating, nutrient loss, and decreased
palatability
• Growth of listeria bacteria
– Results in listeriosis
» Encephalitis
» Metritis and abortion
• Feedout phase
– Exposes silage to oxygen
– Growth of aerobic bacteria and molds
– Results:
• Heating
• Loss of lactic acid
• Nutrient loss
– Losses minimized by adequate feedout rate
• Match diameter of tower silos or width of bunker silos to
herd size
Season
Silo type
Winter
Summer
Inches removed/day
Tower
2
4
Bunker
4
6
SILO TYPES
• Tower
– 30 to 50% DM
– Easy to pack
• Good for hay crop or corn silage
– Minimal exposed surface
– Expensive
• Bunker or trench
– 30 to 40% DM
– Difficult to pack
• Not desirable for hay crop silage
– Requires polyethylene cover
– Considerable surface area at feeding
– Less expensive than towers
• Silo bags
–
–
–
–
–
–
30 to 50% DM
Easy to pack
Minimal exposed surface
Versatile
Bags subject to punctures and tears
Relatively low capital investment
• Big bale silage
– 40 to 60% DM
– Advantages
• Inexpensive
• Allows small amounts of forage ensiled
• Transportable
• No specialized equipment beyond wrapper
– Limitations
•
•
•
•
•
Some large balers can not bale high moisture forage
Long forage more difficult to ensile than chopped forage
Bales are heavy
Plastic wrap subject to puncture and tears
Disposal of plastic
DM LOSSES FROM DIFFERENT SILO
TYPES
Silo types
Concrete
tower
Bunker
Bag
Round bale
DM losses, %
Respiration
4
4
4
4
Harvesting
2
2
2
4
Storage
9
15
7
18
Feedout
2
4
4
4
Total
17
25
17
30
PROPERTIES OF HIGH QUALITY SILAGE
Silage pH
3.6 – 4.2
Lactic acid
4-8% of DM
Acetic acid
<2%
Butyric acid
<0.1%
Nitrogen fractions
Ammonia nitrogen
<5% of total N
ADIN
<12% of total N
Microbial assay
Total aerobic bacteria
<100,000 cfu/gm silage
Molds
<100,000 cfu/gm silage
MAKING HIGH QUALITY SILAGE
• Harvest at appropriate maturity and moisture
• Set chop length
Crop
Length of chop
Hay crop
¼”
Unprocessed corn
silage
3/8 to ½”
Processed corn silage
(Kernel processor)
¾”
• Fill silo as rapidly as possible
• Pack, pack and pack some more
• Cover silos immediately
– 6-mil plastic
– Weight on bunker silos
• Feedout
– Adequate rate
– Maintain clean face
SILAGE ADDITIVES
• Water
– Added if forage moisture is inadequate
– Requires 5 gallons/ton to change DM by 1%
• Bacterial inoculants
– Lactobacilli
– Add a minimum of 100,000 cfu/gm fresh forage
– Useful to:
• Improve lactic acid production if forage is harvested at
excessive moisture concentration
• Prevent aerobic damage at feedout or in feed bunk
• Enzymes
– Cellulases, hemicellulases, amylases, pectinases
– Increase sugars to improve lactic acid production
– No consistent improvement
• NPN sources
– Used with corn, sorghum, and cereal silages
– Types
• Anhydrous ammonia at 5 to 10 lb/ton fresh forage
• Urea at 10 to 20 lb/ton fresh forage
– Advantages
• Increases crude protein content
• Increases aerobic stability at feedout
• Acids
– Propionic or formic acid
• Application: 10 to 20 lb/ton fresh forage
– Applied to forage that is either too wet or too dry
• Formic acid causes a rapid decrease in pH if too wet
• Propionic acid inhibits mold growth in too dry
• Sugar sources
– Molasses, whey, or grain
– Added to crops with low concentration of soluble sugars
• Grasses and legumes
– Increases lactic acid concentration
– Loss of energy from the source
NUTRITIONAL VALUE OF HIGH QUALITY
SILAGE
• Lower feed consumption than fresh crop or hay
• Lower NDF, but comparable ADF to fresh crop or hay
• Comparable net energy concentration to fresh crop
or hay
• Comparable crude protein concentration to fresh
crop, but greater than hay
• Greater proportion of crude protein will be
degradable in the rumen than fresh crop or hay
• Higher carotene content than hay