PROTECTING AND SUPPLEMENTING CORN SILAGE IN BUNKER SILOS WITH SALT-STARCH COVERINGS. Nathan A. Pyatt and Dr. Larry L. Berger

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1 PROTECTING AND SUPPLEMENTING CORN SILAGE IN BUNKER SILOS WITH SALT-STARCH COVERINGS Nathan A. Pyatt and Dr. Larry L. Berger INTRODUCTION Whole plant corn silage (Zea mays L.) continues to be a major forage and energy source in the North American cattle industry (12). In 2000, roughly 7.5% of the US corn acreage was harvest as silage, totaling just less than 2.4 million hectares (20). Feed quality characteristics are dependent on a number of environmental and managerial factors, such as climate, harvesting DM content, maturity, mechanical processing, fermentation efficiency, storage system, storage length, fill and feed out rates, surface area exposure, additives used, etc. Among these factors, Bolsen et al. (4) recognized the degree of anaerobiosis, or oxygen exclusion as the leading concern. Nutrient losses are often worse than DM losses indicate, as aerobic bacteria metabolize WSC. Ruppel et al. (17) reported DM losses ranging from 3-28%, but noted as high as 70% loss of digestible carbohydrate and up to 50% of soluble protein. Most producers don't understand that 2.5-cm of black forage may have been 5 to 8-cm of green high-quality feed when placed into storage (10). This represents a 50-65% loss in DM. Horizontal bunkers are economically attractive (25-50% of upright silo cost) and advantageous for storage of large amounts of ensiled feed, quick filling capacity with conventional equipment, and less energy for feed removal. However, bunker silos are prone to incur greater storage losses (15-30% DM loss) without proper management. Many producers leave bunkers uncovered because of the belief that awkward plastic, tires, and labor intense covering aren't worth the savings in spoilage. Even so, covering bunker silos with plastic, while vastly better than uncovered, is not 100% effective in reducing aerobic spoilage. Producers have sought less time consuming and more efficient alternatives. Other covering research such as sawdust, soil, limestone, candy, molasses, nutri-shield, small grain sod, manure solids, small grain straw, or corn fodder, has shown little to no benefit over uncovered silage (9, 10, 15). Producers would prefer to feed these alternative covers, rather than dispose of the plastic covering. Several sprayon products have been developed and tested, but to date nothing has emerged as a successful product. The objective of this research was to evaluate the effectiveness and durability of an edible saltstarch covering in supplementing and protecting corn silage in bunker silos from weather damage and spoilage. MATERIALS AND METHODS Storage Trial On August 30 and 31, 2000, whole-plant corn (two-thirds ML and 39.99% DM) was chopped and packed to equal densities (215-kg of DM/m 3 ) into six side-by-side 3.66-m long x 1.83-m wide x 1.83-m deep bunker silos. Equal volumes ( kg DM) of pre-ensiled whole-plant corn were weighed into each bunker using a feed wagon, leveled and packed with a single

2 wheeled (rubber tire) garden tractor and lawn roller at the Beef Unit of the University of Illinois located in Urbana, Illinois. Two bunker silos (replicates) of each treatment were designed with plywood walls (surrounded by large round bales of corn stalks for support) and lined with 6-mil polyethylene plastic to break the silage to soil contact and minimize spoilage. Bunker silos faced open to the south, with a gentle slope. The silos were used to evaluate one of three storage alternatives, including an edible salt-starch mixture, which was tested for structural integrity, water shedding, and nutrient preservation potential. Treatments evaluated were covered with plastic (TARP); covered with a salt-starch matrix (SSM); and uncovered (CON). Application of Covering The plastic covering for the TARP treatment was secured into place with wooden posts and a thin layer of chopped forage in order to maintain an anaerobic seal for fermentation. The salt-starch mixture was pre-determined based on laboratory evaluation for freeze-thaw endurance and previous storage results for LRB. Ingredient composition for SSM is presented in Table 1. Application and mixing equipment used for amending the salt-starch covering included a small industrial mortar mixer, propane grill, and torch. Dry ingredients and oil were mixed in a (paddle) mortar mixer to form a uniform blend. Water was heated to boiling temperature and slowly added to the mixer until the desired consistency was achieved. The salt-starch mixture becomes gelatinized with the addition of the boiling water, creating a bread dough consistency. Covering was applied manually to both replicate bunker silos with a cement trowel, to ensure an even application, good adhesion to the silage surface, and a smooth finish. Salt-starch cover was applied at a rate of approximately 36-kg/m 2 (wet weight) or a surface thickness of 1.3 to 1.9-cm. SSM covering was allowed to cure for 3 days. The salt-starch covering was then sealed with a thin layer of paraffin wax, melted and applied with a paint roller. Weekly observations of covering effectiveness and durability were recorded. Local climate data, including daily precipitation and temperature range, was obtained from the University of Illinois Department of Atmospheric Sciences, at Feeding Trial Forty-eight Angus heifer calves ranging from 262 to 390-kg were randomly allotted by weight on December 1, 2000, to one of 12 slotted floor pens of four head each. Heifers were weighed on two consecutive days at the initiation of the feeding trial. Each pen was randomly assigned a bunker silo treatment. Each bunker silo was fed to two pens of heifers. Heifers were fed ad libitum levels of corn silage. Silage was top-dressed with a dry grower/finisher supplement formulated to meet protein, vitamin and mineral requirements for growing heifer calves. Composition of the grower/finisher supplement can be found in Table 2. Heifers had been fed similar high roughage diet prior to the feeding trial. Treated bunker silos remained in storage for 92 days (August 31, 2000 December 1, 2000). All spoilage was separated based on physical appraisal, weighed and discarded. Spoilage separation was performed every two days prior to collection of fed silage. Plastic was removed as needed for the TARP treatment to expose silage for feeding. SSM cover was removed as needed and

3 weighed to evaluate effectiveness and separate any spoilage present. Fed silage was weighed into daily feed increments two days at a time. The first day was directly fed to each pen, while the second day's ration was stored in a sealed barrel overnight. Treatment cover was discarded through the first 20 days of the feeding trial. Heifers were fed the SSM covering during the last 6 days of the feeding trial at a fixed rate (0.91-kg As- Fed/head/d) to evaluate the palatability of the salt-starch covering in a TMR diet. Observations on acceptability of the covering were recorded daily throughout the feeding trial. Pens were terminated from the trial once corn silage from each bunker silo was consumed. Heifers were weighed on consecutive days at the termination of the trial to determine final weight and calculate performance parameters for treatment comparison. Sampling Technique and Analysis A wooden frame, measuring x 30.5-cm, was utilized to evaluate the amount of spoilage under a fixed area. The frame was randomly placed within each bunker silo prior to feeding, and spoilage within this area was removed and weighed for treatment comparison. During the feeding phase, a 929-cm 3 section was removed from the silo face, collected and weighed to estimate silage mass density. Grab samples for all four silage wagonloads were utilized to establish pre-ensiled whole-plant corn nutritive value. Three random grab samples of silage to be fed were collected from each bunker silo. Grab samples of spoiled silage, corresponding to frame spoilage comparisons, were collected from each bunker silo. Prior to feeding, grab samples of the SSM treatment from each bunker silo were collected to determine the nutritional value of the covering. All pre-ensiled, fed and spoiled corn silage, and covering samples were dried in a 55 o C oven, and ground in a Wiley mill to pass a 1-mm screen. Pre-ensiled, fed silage and covering samples were analyzed for DM, OM, Ash, NDF, ADF (8) and Kjeldahl N (1, 3). Spoiled silage samples were analyzed for DM, OM, Ash, NDF, and ADF (8). A small portion of the third fed silage sample was used to determine ph. Statistical Analysis Least squares means for the storage trial and laboratory analysis parameters were analyzed using the GLM procedure of SAS (19) with bunker silo as the experimental unit. The model statement for analyzing the storage trial data contained starting weight, fed silage, silage recovery (%), spoiled silage, percent spoiled, other losses and animal days/bunker as dependent variables, and treatment as the independent variable. The model statement for analyzing the chemical composition data for the fed silage contained DM, OM, NDF, ADF, and CP as dependent variables, and treatment as the independent variable. The model statement for analyzing the chemical composition data for the spoiled silage contained DM and OM as dependent variables, and treatment as the independent variable.

4 Heifer performance data was analyzed using the PROC MIXED procedure of SAS (19). The model statement contained the dependent variables of starting weight, final weight, days on feed, gain, average daily gain, dry matter intake, and gain to feed ratio, and treatment as the independent variable. Bunker silo was modeled as a random effect. Frame comparison of spoiled silage was analyzed using repeated measures in the PROC MIXED procedure of SAS (19). The model statement contained frame spoilage as dependent variables, and treatment as the independent variable, while each observation served as a repeated measure in time. RESULTS AND DISCUSSION Storage Trial The corn silage remained in storage for 92 days. Precipitation during the storage period totaled 27.5-cm. Weekly observations of SSM did not indicate any sudden or gradual erosion, as seen with the LRB treated with SSM coverings. The gentle slope of the silo face was more conducive for maintaining treatment covering, than the perpendicular sides of a LRB. The SSM covering exhibited good sealing properties for corn silage bunker silos. Initial ensiling DM for the whole-plant corn was 39.99%. Recommendations for DM at ensiling for bunker silos range from 30-40% DM. However, wetter silages are preferred to achieve a greater packing density. Ishler et al. (13) reported a recommended ensiling DM between 30-35% DM for alfalfa silage stored in bunker silos. In this trial, DM content at ensiling may have restricted final mass density (215-kg DM/m 3 ). Measured density values for experimental bunker silos ranged from 185 to 235-kg DM/m 3. Minimum recommended packing density is 225-kg DM/m 3 (17). Fed silage samples met the recommended range of 3.8 to 4.5 for stable ph. Treatment comparisons were not statistically compared for ph, as the focus of our project was not on fermentation characteristics, but rather covering effectiveness. However, salt content of the experimental covering did not negatively affect fermentation characteristics. This is in agreement with previous research stating that salt had no effect on hay crop silage fermentation, ph, VFA production, seepage, mold, or bacterial activity (6, 7, 18, 21, 22). Treatment comparisons of silage recovery and spoilage volume are reported in Table 3. No significant differences were detected in initial silage volume packed into treatment bunker silos. At the initiation of the feeding trial, an un-quantified portion of spoiled silage was removed from the bottom of the slope of each bunker silo. Each bunker silo face was removed evenly to ensure equal starting points for each replicate. Silage was removed from the slope until edible silage was visible. Edible silage volume and percent recovery were significantly different (P<0.05) between storage treatments. Silage volume and percent recovery for bunker silos treated with the SSM covering ( kg, 77.67%) were significantly greater than unprotected ( kg, 44.80%) bunker silos. Silage recovery for TARP bunker silos ( kg, 56.46%) fell intermediate to SSM and CON treatments.

5 Spoiled silage volume and percent spoiled was significantly different (P<0.05) between storage treatments. Spoiled silage volume and percent for bunker silos treated with the SSM covering (48.21-kg, 3.07%) were significantly less than unprotected ( kg, 16.95%) and tarped ( kg, 21.90%) bunker silo treatments. Previous research has indicated covering bunker silos with tarpaulin/plastic reduces spoilage 12-28% DM when compared to unprotected silage (5, 11, 14, 16). However in this trial, imperfections in plastic seal and bunker wall leaks were believed to be the cause of excessive spoilage and oxygen penetration in tarped bunkers. Silage losses for plastic covered bunkers were greater due in part to the large surface area to volume ratio associated with small bunker silos. Losses due to fermentation and bottom slope removal were also considered as a percent of original whole-plant corn ensiled. Fermentation losses were significantly different (P<0.05) between storage treatments. The resulting number of animal days fed per bunker silo was significantly different (P<0.05) across treatments. The SSM covering had a greater edible silage recovery rate, resulting in 212 days of feed, while TARP (152-d) and CON (140-d) bunker silos resulted in a significantly less days of feed. Frame comparisons of spoiled silage within a fixed area were reported in Table 4. Spoilage measurements were significantly different (P<0.0002) between treatments. The SSM covering (1.23-kg) yielded less spoilage when compared to both tarped (16.43-kg) and unprotected (14.31-kg) treatments. Again, previous research has indicated covering bunker silos with tarpaulin/plastic reduces spoilage when compared to unprotected silage (5, 11, 14, 16). However in this trial, imperfections in plastic seal and bunker wall leaks were believed to be the cause of excessive spoilage and oxygen penetration in tarped bunkers. Composition analysis for pre-ensiled, fed, and spoiled silage samples was reported in Table 5. Among fed silage samples, significant differences (P<0.05) were detected between treatments for DM, OM and ash values. Final DM of fed silage was significantly lower for unprotected (31.13% DM) silage, when compared to SSM (36.82%) and TARP (41.02%) silage treatment. This trial is in agreement with previous work that tarped bunker silos have greater final DM than uncovered silage (5, 11, 14, 16). The SSM fed silage samples were significantly lower in OM (84.89%) and higher for ash content (15.11%) when compared to TARP (93.97%, 6.03%) and CON (94.09%, 5.91%) samples. The difference in ash content of the SSM treatment from pre-ensiled composition (15.11% vs. 5.83%) may be due to some leaching of covering ingredient into the silage mass. However, we feel the sample average is not representative of the SSM ash content. Upon examination of each individual sample date for SSM fed silage, it becomes obvious that the ratio of covering to silage relative to sampling location becomes influential. Sample #1 was taken on December 1, near the bottom of the bunker slope, where covering to silage ratio was highest. The ash composition for this sample date was 26.32%. The remaining samples were taken when the covering to silage ratio was lower, resulting in an average ash composition of 9.51%. This leads us to believe that in commercial bunker silos, with a relatively low covering to silage mass ratio, salt leaching would not negatively affect silage OM recovery.

6 No significant differences were found between treatments for NDF, ADF, or CP composition for fed silage samples. However numerically, NDF and ADF concentrations were lowest for the SSM covering treatment, 53.34% and 28.94% respectively, followed by TARP and CON treatments. The data agrees with previous research that uncovered bunker silos incur a greater increase in NDF and ADF percentages during storage (5, 11, 14, 16). Spoiled silage samples were not significantly different for DM content between treatments. However, OM and Ash content of spoiled silage samples were found to be significantly different. The SSM spoiled silage was significantly lower in OM (81.72%) and higher in Ash (18.28%) content when compared to TARP and CON samples. Again, the difference in OM and Ash content of the SSM treatment from pre-ensiled composition (18.28% vs. 5.83%) was likely due to leaching of covering ingredient into the silage mass. Spoiled silage was generally located directly beneath the SSM covering and along bunker silo walls. The difference between SSM spoiled and fed silage composition is likely related to the rate and extent (depth) of leaching of the covering ingredients. Feeding Trial Results from the feeding trial are displayed in Table 6. Starting and final heifer weights were not significantly different (P>0.05) between treatments. Total gain was significantly higher (P<0.05) for heifers consuming SSM covered silage, while TARP and CON were similar. Differences in total gain can be attributed to the number of days on feed. Heifers fed silage from bunker silos protected with the SSM covering spent a significantly greater number of days on feed, 26.5 days, when compared to TARP (19.0-d) and CON (17.5-d) treatments. Overall ADG was not significantly different between treatments. Total DMI was significantly greater for the SSM treatment ( kg), followed by TARP ( kg) and CON ( kg). Overall feed efficiency, calculated as gain to feed, was significantly different between storage treatments. Heifers fed silage from the unprotected control (0.1991) had significantly greater gain:feed ratios over the SSM treatment (0.1667), while TARP was intermediate at Observations for feed efficiency over short periods of time are highly influenced by environment, diet DM, water consumption, and gut fill. Since the SSM heifers were fed longer and under changing environmental conditions, factors other than energy density of the silage may have affected feed efficiency. The SSM is not believed to dilute dietary energy in protected corn silage. Feeding of the SSM covering in a TMR ration yielded positive results. While only a small amount of covering was fed for a short period, separation of orts found only a small amount of covering refusal. On average animals appeared to consume approximately 90.71% of the covering offered. Growing heifers of this weight (330-kg) require 7.72-g/d of salt. Experimental heifers would need to consume 35.1-g/d of the covering to meet their salt requirement. On average, heifers consumed kg of the covering each day with a total of g of salt. In a commercial setting with larger bunker silos, the proportion of SSM to silage would be much lower than the designated amount that was fed to the heifers. Our reasoning for feeding the covering at this level was to evaluate covering acceptability in a TMR diet. The SSM covering did provide adequate amounts of salt to meet the growing heifer's requirement.

7 IMPLICATIONS Results indicate that salt-starch covering provided a significant improvement in nutrient recovery as an alternative covering on bunker silos filled with corn silage. The salt-starch covering exhibited excellent sealing properties, having greater DM recovery and less spoilage when compared to controls. Corn silage quality recovery was evaluated utilizing RFV calculations for fed silage samples. Uncovered bunker silos had the lowest recovery in terms of RFV at 104.4, while plastic covered silos yielded silage valued at 110.8, a 6.4 unit advantage. Bunker silos treated with the salt-starch covering averaged a RFV of 115.7, an additional 5.0 unit advantage above plastic coverings. Heifers fed the salt-starch covering in a TMR diet consumed approximately 90.71% (as fed) of the covering offered. The edible salt-starch covering exhibited excellent potential as an alternative storage covering for corn silage stored in bunker silos.

8 Tables Table 1. Ingredient Composition of the Salt-Starch Covering (Wet Weight basis) Ingredient SSM Water 50.0% Salt 22.0% Flour 22.0% Vegetable Oil 4.0% Potassium Bitartrate 2.0% Table 2. Ingredient Composition of Grower/Finisher Supplement Ingredient % Dry Matter Basis Soybean Meal (48%) 40.25% Dicalcium Phosphate 2.50% Lime 5.00% Salt 0.60% Dairy TM 2.40% Molasses 5.00% Urea 5.00% Monensin % Corn 39.06% Table 3. Treatment Comparison of Corn Silage Ensiled in Bunker Silos Storage Treatment TARP 1 SSM 2 CON 3 SEM DM Basis Starting weight., kg Silage recovered, kg ab a b Silage recovered, % ab a b 5.01 Spoiled silage, kg b a b Spoiled silage, % b 3.07 a b 2.33 Other losses *, % ab a b 3.87 Animal days/bunker 152 b 212 a 140 b Plastic tarpaulin 2 Salt-starch matrix 3 Uncovered a,b Means within a row with different superscripts differ (P<0.05) * Other losses include fermentation losses and bunker face removal (at opening).

9 Table 4. Treatment Comparison of Spoilage in a Fixed Area (DM Basis) Covering n Spoilage, kg Plastic covered b SSM a Uncovered b SEM a,b Means within a column with different superscripts differ (P<0.01) 1 Salt-starch matrix Table 5. Treatment Comparisons of Chemical Composition in Corn Silage Fractions (DM Basis) Analysis Pre- Ensiled Fed Silage Spoiled Silage TARP 1 SSM 2 CON 3 SEM TARP 1 SSM 2 CON 3 SEM DM 4, % a a b OM 5, % a b a a b a 2.62 Ash, % a b 5.91 a b a b 2.62 NDF 6, % ADF 7, % CP 8, % Plastic tarpaulin 2 Salt-starch matrix 3 Uncovered 4 Dry Matter 5 Organic Matter 6 Neutral Detergent Fiber 7 Acid Detergent Fiber 8 Crude Protein a,b Means within a row for each sample time with different superscripts differ (P<0.05)

10 Table 6. Heifer Performance on Corn Silage Ensiled with Different Storage Methods Storage Treatment TARP 1 SSM 2 CON 3 SEM Starting wt., kg Final wt., kg Gain, kg b a b 1.48 Days on feed 19.0 b 26.5 a 17.5 b 0.88 ADG 4, kg/d Total DM Intake, kg b a b 9.39 Gain:Feed ab b a a,b Means within a row with different superscripts differ (P<0.05) 1 Plastic tarpaulin 2 Salt-starch matrix 3 Uncovered 4 Average Daily Gain LITERATURE CITED 1. AOAC, Official methods of analysis. (14 th Ed.). Association of Analytical Chemists. Arlington, VA. 2. Archibald, J.G Studies in the chemistry of grass silage. J. Agric. Res. 72: Bradstreet, R.B The Kjeldahl method for organic nitrogen. Acad. Press, New York. 4. Bolsen, K.K., B.E. Brent, M.K. Siefers, M.E. Uriarte, T.E. Schmidt, and R.V. Pope Silage management: important practices often overlooked. 7/3/ Bolsen, K.K., J.T. Dickerson, B.E. Brent, R.N. Sonon, JR., B.S. Dalke, C. Lin, and J.E. Boyer, JR Rate and extent of top spoilage losses in horizontal silos. J. Dairy Sci. 76: Erickson, P.S. 06July2001. Personal communication. University of New Hampshire. 7. Goering, H.K., and C.H. Gordon Chemical aids to preservation of high moisture feeds. J. Dairy Sci. 56: Goering, H.K., and P.J. Van Soest Forage fiber analysis. USDA Handbook No Agric. Res. Serv. Washington, D.C.

11 9. Holmes, B.J You can't judge a bunker silo by its cover. 7/17/ Holmes, B.J. No date. Bunker silo cover alternatives. 7/17/ Holmes, B.J., and R.E. Muck Preventing silage storage losses. 7/17/ Johnson, L., J.H. Harrison, C. Hunt, K. Shinners, C.G. Doggett, and D. Sapienza Nutritive value of corn silage as affected by maturity and mechanical processing: a contemporary review. J. Dairy Sci. 82: Isler, V.A., A.J. Heinrichs, D.R. Buckmaster, R.S. Adams, and R.E. Graves Harvesting and utilizing silage. Ext. Circ. No The Pennsylvania State Unvi., University Park. 14. McGuffey, R.K., and M.J. Owens Effect of covering and dry matter at ensiling on preservation of alfalfa in bunker silos. J. Anim. Sci. 49: Minson, D.J., and R.J. Lancaster The efficiency of six methods of covering silage. New Zealand J. of Agric. Res. 16. Oelberg, T.J., A.K. Clark, R. K. McGuffey, and D. J. Schingoethe Evaluation of covering, dry matter, and preservative at ensiling of alfalfa in bunker silos. J. Dairy Sci. 66: Ruppel, K.A., R.E. Pitt, L.E. Chase, and D.M. Galton Bunker silo management and its relationship to forage preservation. J. Dairy Sci. 78: Shockey, W.L., and D.C. Borger Effect of salt on fermentation of alfalfa. 2. Treatment with sodium chloride, clostridium butyricum, and lactic acid bacteria. J. Dairy Sci. 74: SAS SAS/STAT User's Guide (Version 6.2 Ed.). SAS Inst. Inc, Cary, NC. 20. USDA website /19/ Wilson, J.K Changes occurring in silage as effected by salt. J. Am. Soc. Agron. 40: Woolford, M.K Antimicrobial effects of mineral acids, organic acids, salts and sterilizing agents in relation to their potential as silage additives. J. Br. Grassl. Soc. 33:131. Submitted 2/20/03.