Silage Fermentation Process

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Silage Fermentation Process

• Aerobic (First stage)
• - Plant respiration
• 602 C6H12O6 ? 6CO2 6H2O heat
• -Plant enzymes, yeast, and molds are active
  raising temperature
• -Air forced out by forage settling
• -O2 replaced by CO2 (anaerobic conditions
  formed)
• -4 to 5 hours
• -Temperature rise stops, 90-100oF desired

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• Anaerobic (Second stage)
• Anaerobic and faculative anaerobes function, two
  phases
• Acetic acid, decreases pH to about 5
• Lactic acid, major phase, last longest
• Bacteria require CHOs for fermentation process
  and desire 80 to 95F temperature

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• Bacteria convert CHOs to lactic acid and other
  acids
• C6H12O6 ? 2(C3H6O3)
• 673 cal ? 652 cal (3.1 loss)
• Want sufficient acids to
• Lower silage pH (lt4 desirable)
• Develops desirable color and odor
• Stops growth of other bacteria
• Hydrolysis of hemicellulose
• Last for about 10 to 20 days - constant

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• Undesirable fermentation (too much O2 present)
• Aerobic bacteria (clostridia, coliforms, and
  yeast) use up CHOs
• Produce butyric acid
• 2(C3H6O3) ? C4H8O2 2H2 2CO2
• 652 cal ? 524 cal (128 or 19.6 loss)
• Therefore, pH doesnt drop low enough
• Putrefactive anaerobes work on proteins
• NH3, volatile fatty acids, H2S, and amino acids
  released

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• Losses in dry matter in making silage
• Respiration, 1 to 3
• Fermentation losses, 5 to 10
• Seepage losses, 5 to 7 common
• Surface losses, 2 to 4 with plastic covers
• Air pockets
• Weathering of surfaces after opening

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• Heat damage
• Temperature should not exceed 100F
• Low-moisture silage (haylage)
• Maillard product formation or tobacco-brown
  silages (carmelization)
• Protein digestibility decreases, ADFN or ADIN
• Cold fermentation, lt75F
• 75 to 80 moisture silages (direct-cut legumes)
• High butyric acid formation common

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Factors influencing silage process and quality,
(Bolsen, 1985)

• Biological Crop Characteristics
• Hybrid -Plant structure
• DM content -Stage of maturity
• WSC content -Weather
• Buffering capacity
• Effective harvest time

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Factors influencing silage process and quality,
(Bolsen, 1985)

• Biological-Epiphytic Microflora
• Substrate
• Weather
• Additives

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Factors influencing silage process and quality,
(Bolsen, 1985)

• Management and Know-how
• Improving suitability
• Field Wilting
• Additives
• Mechanical treatment

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• Storage conditions
• Silo construction
• Rate of filling
• Compaction and density
• Sealing method
• Oxygen access
• Temperature and insulation
• Mechanical treatment

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Major Controllable Factors That Affect Silage
Quality

• Moisture Probably the most important
• 60 to 72 ideal storage facility dependent
• Too wet causes
• Seepage
• Undesirable clostridial activity and high butyric
  acid
• High fermentation losses
• Intake and animal performance losses

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• Too dry
• Problems eliminating air
• Problem achieving sufficient pH
• Aerobic deterioration is high

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Control moisture in silage by

• Maturity, recommended
• Corn fully dented
• Alfalfa Recommended stage for each harvest for
  prime hay
• Perennial grasses late boot to early heading
• Sorghum soft-dough kernels
• Small grains boot (high energy and protein/lb)
• Soft dough (Max. yield digestible nutrients/acre)
• Dry matter additions
• Adding water
• Wilting to desired moisture

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• O2 exclusion
• Chopping length ¼ to ½ inch
• Filling rate, packing, and sealing
• Storage structure 10 to 25

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• Chemical composition of material ensiled (i.e.,
  CHO content)
• Ideal crop
• Adequate fermentable CHO
• Low buffering capacity
• Physical structure suitable for compacting
• Several-day harvest period
• Controlled by
• Crop maturity
• CHO additions
• Crop selection
• Most crops adequate

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Silage Additives, Preservatives, and/or
Conditioners

• To be effective, additives must affect major
  controllable factors.
• Additives classified by
• Stimulate fermentation
• Nutritive feed stuffs (grains, urea (10
  lb/ton), limestone, etc.)
• Nonnutritive enzyme, bacterial, and yeast
  cultures
• Lactic acid
• Survival of Phase I?

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• Prevent fermentation
• Nutritive salt, propionic acid, formic acid
• Nonnutritive mineral and organic acids, acid
  salts (CA formate, NaNo3), antibiotics and other
  mold inhibitors, formaldehyde

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• National Feed Ingredients Association
• Preservatives antibiotics, sterilants,
  formaldehyde
• Direct acidification additives formic acid
• Added feed stuffs Ca, NPN
• Fermentation aids enzymes and bacterial
  inoculants

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Summary of inoculant studies

• 67 improved silage fermentation
• ? Lactic/acetic ratio
• ? pH
• ? NH3
• 60 ? dry matter recovery (2-3)
• 40 ? milk production
• 25 ? dry matter intake and ADG

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• When significant
• DM intake ? 11
• ADG ? 11
• Milk production ? 5
• Feed efficiency ? 9

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• Do additives or preservative work?
• Inadequate testing but consider following
• Nutrient additives may be effective, but risk
  loss with spoilage
• Preservatives (i.e., chemicals) will not
  substitute for proper air exclusion and moisture
  control
• Preservatives generally do NOT produce nutrients
  in silage, only retain what was present
• Cost high relative to silage value
  (15-20/ton)
• If preservative cost 2/ton, need 10 to 15
  improvement to pay cost
• Summary NO SUBSTITUTE FOR GOOD MANAGEMENT