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HARVESTED FORAGES Silage. pp. 253-260. 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.
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HARVESTED FORAGESSilage pp. 253-260
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
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
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 • Homofermentativelactic 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
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
MAKING HIGH QUALITY SILAGE • Harvest at appropriate maturity and moisture • Set chop length • 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 rumenthan fresh crop or hay • Higher carotene content than hay