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Principles of Silage Fermentation and Management
L. E. Chase and T. R. OvertonDept. of Animal Science
Cornell University
What is Silage?
“The feedstuff resulting from the anaerobic preservation of moist forage or other feeds by the formation and/or addition of acids”
Dr. M. E. McCullough
Forage Goals
Table 1. Characteristics of quality silageType of Silage
Alfalfa Grass Corn Neutral Detergent Fiber, % 39-43 48-55 40-45
Dry matter, % Bunker 34-40 28-38 30-35Upright (stave)34-42 34-45 32-38Bag 34-45 30-40 32-38
Odor Little or none at a distance; slightly sharp, pleasant up closeLactic acid Wet (< 35% DM) 6-8%, Wilted (>40% DM) 3-4%Acetic acid < 1-2%; ratio of at least 3:1 lactic:aceticButyric acid < .1%Total VFA < 10%
Particle length 8-15% of TMR on coarse screenIron < 200 ppm
Silage Fermentation (Dr. Limin Kung, Jr.)
sugarslactic acid
pH
Days of Ensiling
Common Measurements of Fermentation End Products
Item CommentsDM (+) can dictate type, speed, and
extent of fermentationpH (+) measures strength of acid in
sample Ammonia (–) indicator of excessive
protein degradation
Common Measurements of Fermentation End Products
Item Comments
Lactic acid (+) strongest acid
(–) weak antifungal
Acetic acid (+) very antifungal
Butyric acid (–) a weak acid
Propionic acid (+) very antifungal
Microbes Good bugs
Lactic acid bacteria
heterofermentative
homofermentative
Bad bugs Fungi
yeasts molds
Enterobacteria
Clostridia
Silage Fermentation Phases
Nitrogen Compounds in Fresh Forage and Silage
01020304050607080
% of total-
N
Prot-N NPN-N Amino-
N
NH4-N
N fraction
Fresh
Silage
Oshima et.al.,1979
Silage DM and NPN
0
20
40
60
80
100
% of Total
N
14.7 31.8 46.3 64.7
DM, %
NPN
NH4-N
Muck, 1987
Excess Oxygen Has Negative Effects on the Ensiling Process slower fermentation excess protein breakdown growth of undesirable aerobic
organisms excess heating (silo and feed bunk) more nutrient and DM loss (10-
25%)
How Dry Matter Content Affects Fermentation
DM%< 30% Too Wet 35 - 45% > 55% Too Dry
run off poor packing, airclostridial growth slow fermentationprotein degradation molding/heatingexcessive fermentation heat damaged proteinDM and energy losses DM and energy losses
Dr. Limin Kung, Jr.
Figure 2. The Effect of DM on Corn Silage Fermentations
0.00
2.00
4.00
6.00
8.00
10.00
12.00
<26 26-28 28-30 30-32 32-34 34-36 36-38 38-40 >40
Dry Matter
% o
f DM
pH
Lactic
Acetic
Total VFA
Cumberland Valley Analytical Services
Figure 1. The effect of DM on legume silage fermentations
0.00
2.00
4.00
6.00
8.00
10.00
12.00
<24 24-28 28-32 32-36 36-40 40-44 44-48 48-52 >52
DM Range
% o
f D
M
NH3 Nitrogen as % DMpHLacticAceticButyricTotal VFA
Cumberland Valley Analytical Services
Aerobic Deterioration
Occurs primarily in feedout periodSignals are heating and spoilageInitiated by yeasts and molds which
oxidize the preservation acidsEquals energy loss and potential DMI
depression
Clostridial Silage
Spore forming bacteriaAre normally anaerobicLow DM levels ( <30% ) increase riskpH is usually > 5High ammonia & butyric levelsDepresses dry matter intake
What Steps Are Needed?
Start = Forage standing in field
End = Forage consumed by the cow
What do we need to manage?
Silage Triangle
Sugar
Bacteria Acids
H20
Health effects of a fermentation gone awry
1200 cow NY dairy
Decreasing milk production
Increasing metabolic disorders
Alfalfa 1st 99Cows Inconsistent…Milk 66 lbs
%ADF 39.9NDF 46.6CP 20.4
DM 26.5pH 5.7NH3 -N, 33 % of total NLactic .8Acetic 3.5Butyric 4.4Total VFA 10.1
Alfalfa 3rd 99BAR72 lbs%394420.2
344.712
5.51.5<.017.4 NY Dairy 12-99
7 days
Key Points
Harvest at correct moisture & maturity
Fill FAST !!Pack, pack, pack, pack, etc.Seal with a coverConsider a bacterial inoculantFeedout = tight, straight faceFeed fast to minimize reheating
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