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 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 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 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 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, 1991. Heterofermentative Lactobacillus brevis Lactobacillus buchneri Lactobacillus fermentum 4. Stable Phase when ph reaches 3.8-5.0, 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 TABLE 2. PATHWAYS IN SILAGE FERMENTATION Pathway Lactic acid bacteria Recovery, % Dry Matter Energy Homofermentative 1 Glucose 2 Lactic acid 100 99 Heterofermentative 1 Glucose 1 lactic acid + ` Ethanol + 1 CO 2 76 98 3 Fructose 1 Lactic acid + 2 Mannitol + 1 Acetic acid + 1 CO 2 95 99 Enterobacteria 1 Glucose 1 Acetate + Ethanol + 2 CO2 + H2 + 2 H2O 95 83 Yeasts 1 Glucose 2 Ethanol + 2 CO 2 52 99 Clostridia 2 Lactic acid 1 Butyric acid + 2 CO 2 + 2H 2 49 81 SOURCE: McDonald et al., 1973; McDonald et al., 1991 Taken from Buxton et al., 2003. Silage Science and Technology. ASA. 6. Feedout Phase The largest loss of DM and nutritional value can occur as aerobic microbes consume
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 Fig. 4. Optimum DM content for good silage-making. Source: Pitt, R.E. 1990. 2. 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 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 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 c. Provide sufficient LAB - addition of inoculants of LAB, Muck and Bolsen, 1991. 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 151 101.5 140 106.2 110 103.0 46 100.0 36 100.4 18 102.2 11 108.0 Avg 103.0 8 97.8 7 100.7 6 99.6 4 98.5 1 1 SOURCE: Satter et al. (1988). Taken from Muck and Bolsen, 1991. Avg 100.0 98.5 99.2 d. Minimized protein solubility
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., 1990. 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 - 0.1 0.05 0.3 0.6 1.6 During filling, % per day During storage, % per month 0.8 0.5 1 1.2 1.5 Feed-out, % 1.5 1.5 1.5 1.5 2 Fermentation, % 2 1 3 3 2 Effluent, % 0.2 0.0 0.5 0.5 0.0 TOTAL, % 9 6 13 15 16 * 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 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., 2003. Silage capacity Alfalfa silage, at moisture Corn silage, at moisture ------------Tons wet basis------------ 40 50 60 70 55 60 65 70 32 40 52 75 43 49 56 67 57 71 94 136 77 88 101 120 63 78 103 148 84 96 110 130 81 101 134 193 110 124 143 168 90 113 149 215 122 139 159 187 109 137 181 261 148 167 191 224 135 169 224 323 182 206 235 275 147 185 245 354 200 225 258 300 142 178 236 339 191 216 247 288 176 221 293 421 237 266 304 353 211 264 351 504 283 317 361 419 224 281 372 533 298 335 381 442 268 337 446 639 357 399 453 524 314 394 522 746 415 464 526 607 338 423 559 796 442 494 560 647 407 511 674 956 529 590 667 767 479 600 790 1118 616 685 773 888 551 690 908 1281 704 782 880 1009 796 993 1297 1813 989 1164 1343 1480 920 1146 1494 2079 1129 1341 1547 1706 1046 1301 1692 2346 1270 1520 1754 1934 1173 1457 1891 2614 1411 1701 1962 2165
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------------ 40 50 60 70 55 60 65 70 49 61 80 115 65 74 84 99 63 79 105 151 85 96 110 128 68 85 112 161 91 102 117 137 89 112 148 212 119 134 152 177 100 125 166 238 133 149 170 197 120 150 198 283 158 177 202 234 150 188 248 354 196 220 249 287 166 207 274 389 216 241 273 314 155 195 256 365 203 227 258 299 195 245 322 456 252 281 318 367 236 296 389 549 302 336 379 435 247 308 405 572 315 351 396 456 300 374 490 688 377 419 471 540 354 441 576 806 439 487 547 625 368 459 600 842 461 512 577 662 449 558 727 1013 551 611 686 784 532 660 857 1187 642 710 795 907 616 764 988 1361 734 809 905 1031 867 1070 1379 1892 1033 1269 1459 1606 1007 1240 1590 2169 1202 1472 1690 1860 1150 1411 1830 2447 1374 1678 1923 2116 1294 1584 2017 2726 1549 1886 2159 2374 b. Bunkers silos Minimize dry matter loss Capacity and density prediction DM density (kg m -3 ) = (136.3 + 0.042P)(0.818 + 0.0446H) 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 ) http://www.uwex.edu/ces/crops/uwforage/storage.htm Bunker Silo Density Calculator, excel file updated 4-28-05, SOURCE: Muck and Holmes, 2000.
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., 2003. Sealing treatment Dept DM Alfalfa OM DM Corn OM DM Sorghum OM Cm Bunker silos Uncovered 25 78.8 81.0 80.4 84.5 77.0 81.9 50 23.4 25.5 29.4 29.9 53.2 56.0 75 14.6 14.9 19.2 22.0 20.0 24.2 Polyethylene 25 7.2 7.9 22.5 22.9 21.3 24.8 Seal 50 1.6 1.9 9.1 9.8 6.7 10.0 75 5.7 8.9 12.3 12.8 6.7 8.5 Pilot-scale silos Uncovered Polyethylene Seal 0-33 33-67 67-100 0-33 33-67 67-100 66.1 75.1 40.9 50.9 35.7 46.9 7.7 18.0 7.7 18.1 8.5 18.9 64.3 68.5 37.9 42.3 16.6 21.1 14.6 19.4 13.0 17.5 13.9 18.7 62.3 63.4 34.2 36.0 7.3 8.5 13.5 14.2 7.9 8.5 5.4 6.0 2. Stack silage
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 TABLE 11. Amount of plastic required to cover different silage storage systems, Savoie and Jofriet, in Buxton et al., 2003. 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 15.6 150.73 8 diax85 L+13 -closure 12.5 200 4.4 13 HX30 WX79 L+20 cl 6.2 200 2.4 Plastic per Unit forage Round bale Round bale Round bale Individual wrap 9.4 4x25 8.7 Horizontal wrap 9.4 4x25 5.1 Horizontal wrap 9.4 100 6.1 File: D: AITS/Chapters/Regular/SilagePreservation 11-05.doc 11-4-2005