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