Silage Preservation. 1. Fresh forage contains [ ] moisture. 2. "juice" contains soluble protein and soluble sugars

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1 Presentation by Neal Martin Silage Preservation A. Preservation Expectations From the moment the crop is cut until it is delivered to the animal, biological and mechanical processes take place that decrease quantity and nutritional quality of feed. 1. Preservation goal: conserve the digestible fiber, protein, and energy in the forage and maintain protein in form that can be effectively utilized by the ruminant. 2. Preservation involves: restricting the actions of bacteria, yeasts, molds, and plant enzymes, as well as browning reactions. B. Silage Preservation 1. Fresh forage contains [ ] moisture 2. "juice" contains soluble protein and soluble sugars a. Provides medium b. Provides activity 3. Moisture influences microorganisms and processes, Figure 1. a. Yeasts and molds are microbes that degrade forage in the presence of oxygen b. Lactic acid bacteria (LAB) and clostridia grow without oxygen-lab are beneficial; but clostridia are detrimental c. Plant proteases are enzymes which solubilize plant proteins d. Browning reaction is a chemical reaction associated with high temperatures

2 2 4. Fundamental strategy in Preservation of Silage In silage-making, the forage is stored in oxygen-free (anaerobic) conditions which stimulate growth of LAB and prevent the growth of molds and many yeasts. Bacterial growth without O 2 is called.

3 3 C. Dry matter losses in harvest and storage 1. Hay 2. Silage Fig. 2. Dry matter losses during harvest and storage as dependent on forage moisture content at harvest.

4 4 D. Principles of Ensiling 1. Aerobic Phase O 2 trapped in the air spaces of silage mass is consumed by plant respiration and aerobic microbes respiration process is a. Loss of dry matter b. plant contents are sugar; preservation and nutritional value c. prolonged actions allow yeasts and molds to grow d. heat produced increases temperature 2. Lag Phase Plant cell membranes break down allowing the cell juices to become a growth medium 3. Fermentation Phase The anaerobic LAB begin to grow and multiply rapidly, increasing their numbers to approximately a. Homofermentative LAB (species in four genera - Table 1) produce only lactic acid from fermenting glucose nd other 6-carbon sugars b. Heterofermentative LAB produce ethanol or acetic acid plus CO 2 and lactic acid c. Natural bacteria a mixture

5 5 TABLE 1. LACTIC ACID BACTERIAL IN SILAGE Homofermentative Lactobacillus plantarum Lactobacillus casei Pediococcus cerevisiae Streptococcus faecalis Streptoccus lactis Streptococcus faecium SOURCE: McDonald (1981). Taken from Muck and Bolsen, Heterofermentative Lactobacillus brevis Lactobacillus buchneri Lactobacillus fermentum 4. Stable Phase when ph reaches , the bacteria die out, and the silage 5. Detrimental Processes a. Plant Enzymes breakdown proteins to soluble non-protein nitrogen (NPN) b. Enterobacteria and Listeria (aerobic or anaerobic conditions) form early in ensiling. They produce LA, acetic acid and ethanol. Listeria bacteria cause listeriosis, disease dangerous to both humans and animals. c. Clostridia (anaerobic condition) grow late in ensiling (ph of 7.0) forming LA and free amino acids, this fermentation looses 50% of DM and 20% of energy. Table 2.

6 6 TABLE 2. PATHWAYS IN SILAGE FERMENTATION Pathway Lactic acid bacteria Recovery, % Dry Matter Energy Homofermentative 1 Glucose 2 Lactic acid Heterofermentative 1 Glucose 1 lactic acid + ` Ethanol + 1 CO Fructose 1 Lactic acid + 2 Mannitol + 1 Acetic acid + 1 CO Enterobacteria 1 Glucose 1 Acetate + Ethanol + 2 CO2 + H2 + 2 H2O Yeasts 1 Glucose 2 Ethanol + 2 CO Clostridia 2 Lactic acid 1 Butyric acid + 2 CO 2 + 2H SOURCE: McDonald et al., 1973; McDonald et al., 1991 Taken from Buxton et al., Silage Science and Technology. ASA. 6. Feedout Phase The largest loss of DM and nutritional value can occur as aerobic microbes consume

7 7 E. Silage Management 1. Dry Matter Losses must be minimized a. Unavoidable field, plant respiration, and primary fermentation b. Avoidable effluent, secondary fermentation and aerobic deterioration

8 8 Fig. 4. Optimum DM content for good silage-making. Source: Pitt, R.E Good Silage Making Practices a. Enhance rapid drying in the field. b. Chop haycrop silage at 3/8 inch theoretical length of cut (TLC), corn silage at 1/4 inch. c. Ensile at 30% - 50% DM content.

9 9 d. Fill silo quickly e. Compact forage tightly f. Seal silo carefully g. Leave silo closed for at least two weeks h. Use effective silo designs 3. Challenges for making good alfalfa silage a. Minimum respiration losses TABLE 3. MANAGEMENT PRACTICES TO MINIMIZE RESPIRATION LOSSES IN SILAGE Tower Silo Bunker Silo Long Bag Big Round Bales Chop at correct TLC a. Chop at correct TLC a. Chop at correct TLC a. -- Fill rapidly. Fill rapidly. Fill rapidly. -- Top off with 1 or more ft. of wet forage. Compress forage with tractor during filling. Set filling machine for high compaction. Bale tightly. Cover top with plastic. Cover with plastic, seal ends and sides carefully. Seal ends carefully. Wrap or seal carefully. Treat concrete with sealant. Seal cracks in wall, repair holes in plastic cover. Repair damaged bags. Repair damaged bags. a TLC = theoretical length of cut. Chop haycrop silage at 3/8 inch TLC, corn silage at 1/4 inch TLC. SOURCE: Pit, R.E., 1990.

10 10 b. Lactic acid fermentation requires: 1) sufficient plant sugars 2) lactic acid bacteria on forage 3) anaerobic conditions 4) proper dry matter content 5) harvest with sufficient sugars Table 4. FACTORS AFFECTING SUGAR CONTENT OF HAYCROP FORAGE BEFORE FERMENTATION Factor Solar radiation on day of cutting. Effect Sunny periods promote the deposition of sugar in the growing plant. Hour of cutting. Length of wilting period. Rain damage in field. Rate of silo filling. Compaction of forage. Sealing of silo. Sugar levels are higher late in the day, lowest in the morning. However, early mowing is recommended to reduce wilting time. Plant respiration during drying depletes sugars. Rain on mowed forage leaches out sugars and increases respiration. Delays in attainments of anaerobic conditions extend respiration, decrease sugars. Good compaction shortens the aerobic phase, leaves more sugars for fermentation. Good sealing keeps out oxygen, limits sugar loss through respiration. SOURCE: Pitt, R.E., 1990.

11 11 c. Provide sufficient LAB - addition of inoculants of LAB, Muck and Bolsen, at least the natural population. 1) improved fermentation with alfalfa in 84% of studies 2) reduced ammonia - nitrogen levels in 60% of studies 3) improved DM recovery 74% of studies 4) improved beef and dairy cattle performance 20% - 40% of studies, Table 5. TABLE 5. RESPONSES IN MILK PRODUCTION FOR INOCULATED VS. CONTROL ALFALFA SILAGES Ratio of LAB, inoculant Milk production response, to natural population inoculated as a % of control Avg SOURCE: Satter et al. (1988). Taken from Muck and Bolsen, Avg d. Minimized protein solubility

12 12 TABLE 6. FACTORS AFFECTING PROTEIN SOLUBILIZATION IN SILAGE Factor Effect Crop Species Leguminous protein, especially that of alfalfa, is more rapidly solubilized in the silo. Silage temperature Solubilization rate doubles with a 20 F increase in temperature. DM Content Solubilization is fastest in direct-cut forage (20% DM content); the rate is reduced by 60% at 50% DM content. ph Solubilization is fastest at ph 6; the rate is decreased by 85% at ph 4. Time in silo Proteases lose their activity after 1-2 weeks in the silo. Most solubilization occurs in the first few days of ensiling. SOURCE: Pitt, R.E., F. Silage Storage 1. Silos TABLE 7. TYPICAL LOSSES IN SILOS PER UNIT TIME OR ACCUMULATED* Tower silo Source of dry matter loss 1 Top- Unloading Bottom- Unloading Bunker Stack silo Round Bale silage Aerobic During filling, % per day During storage, % per month Feed-out, % Fermentation, % Effluent, % TOTAL, % * Total losses are estimated on the following management practices: 5 days for filling except for round vales silage(2 days), 6 month average storage period and 48-hour feed-out period SOURCE: Savoie and Jofriet in Buxton et al., 2003 a. Tower Silos

13 13 1) Top unloading TABLE 8. Estimated concrete tower silo capacities, wet basis, for alfalfa and corn silage as a function of moisture, adapted from Jofriet & Daynard, 1988 in Buxton et al., Silage capacity Alfalfa silage, at moisture Corn silage, at moisture Tons wet basis

14 14 2) Button unloading Table 9. Estimated steel tower silo capacities, wet basis, for alfalfa and corn silage as a function of moisture level, Jofriet & Daynard, 1988 in Buxton et al., 2003 Silage capacity Alfalfa silage, at moisture Corn silage, at moisture Tons wet basis b. Bunkers silos Minimize dry matter loss Capacity and density prediction DM density (kg m -3 ) = ( P)( H) Where: P = W/L square root of TD W = average packing tractor weight (kg) L = initial layer thickness (cm) T = packing time (h t -1 as fed) D = dry matter concentration (g kg 1 ) Bunker Silo Density Calculator, excel file updated , SOURCE: Muck and Holmes, 2000.

15 15 Covers TABLE 10. Dry matter and organic matter losses in the top 3.3 feet in bunker and pilot-scale silos, Bolsen, et al., 1993 in Buxton et al., Sealing treatment Dept DM Alfalfa OM DM Corn OM DM Sorghum OM Cm Bunker silos Uncovered Polyethylene Seal Pilot-scale silos Uncovered Polyethylene Seal Stack silage

16 16 3. Bagged silage Dry matter loss can be excessive Porosity increases across face leading to excessive spoilage Operator skill influences density achieved DM loss Density lower for wetter hay crop silages Good management necessary to achieve low DM loss 4. Big Bale silage Use optimum layers of plastic Patch holes Bale between 45 and 65 % moisture Do NOT delay rapping

17 17 TABLE 11. Amount of plastic required to cover different silage storage systems, Savoie and Jofriet, in Buxton et al., Storage System Bunker silo Bag silage Stack silo Plastic Required to Cover Storage Systems Dimensions, Type wrap Silage density Plastic thickness lb ft-³ um lb T-¹ 10 HX30 WX85 L diax85 L+13 -closure HX30 WX79 L+20 cl Plastic per Unit forage Round bale Round bale Round bale Individual wrap 9.4 4x Horizontal wrap 9.4 4x Horizontal wrap File: D: AITS/Chapters/Regular/SilagePreservation doc