By Kevin Putnam, Pioneer Dairy Specialist
While growing conditions determine fiber digestibility, producers can take steps to preserve silage quality after harvest, resulting in better feed for livestock. Preserving forages on both the front and back end of fermentation is key to boosting the bottom line.
Many factors play into nutritive losses at and after harvest. Most important are harvest techniques and overall bunker management (ensiling and feedout). Crop maturity, dry matter at harvest and chop length can affect packing density and fermentation. Knowing field conditions and hybrid maturities helps growers pick the appropriate harvest date. Walk fields and check crop maturity. Harvest is typically 6 to 10 days away when the crop is about 3 to 5 percent wetter than optimal.
After harvest, preserving forage quality depends on keeping out oxygen. The keys are packing density, covering the bunk/pile and feedout management.
Experts suggest an average packing density of 15 pounds or better of dry matter per cubic foot. A density of 17 dry matter pounds potentially saves another 1.5 percent dry matter from oxygen penetration. Dry matter loss diminishes carbohydrates like sugar, which must be replaced by an energy source such as cornmeal.
Follow proper packing guidelines: Spreading layers 6 inches or less across the bunk is optimum. Use the rule of 800: Multiply the number of tons coming in each hour by 800 to get the total pounds of tractor-weight for packing.
After filling silos, use plastic to cover the forage. Some producers use tires to secure plastic covers, while others weigh down plastic with gravel bags or use oxygen barrier liners. Using plastic to line bunkers reduces losses along sidewalls.
Leaving a bunker uncovered can cause the loss of up to 45% of the “nutritive value” in the top 3 feet. A simplistic view of the value of implementing management practices that could reduce shrink losses by 5% in an entire 1,000-ton bunker with an “as fed” value of $45/ton would be $2,250 (1000 tons * 5% = 50 tons *$45 = $2,250).
However, silage dry matter (DM) losses consist of almost exclusively lost sugars, and when sugar is reduced, fiber is actually concentrated. To correctly value shrink loss from a “nutritive” perspective, you have to calculate the value of the lost sugars. The fact that starch and sugar have very similar nutritive value, it is common to express the nutritive loss in terms of pounds of corn grain (cornmeal). The math gets a little confusing now because you have to adjust all the values to a DM basis. If corn grain contains about 70% starch (on a 100% DM basis) then in a 56 lb bushel of corn (at 84.5% DM), you have 33.1 lbs of 100% starch DM (56 lbs * 85.5% DM = 47.3 lbs DM in a bushel * 70% starch = 33.1 lbs of starch). Our 50 tons of lost “as fed” silage in a 1,000 ton bunker (35% DM) equates to 17.5 tons of lost DM (50 * 35% = 17.5). The 17.5 tons of silage “starch equivalent” loss divided by 33.1 lbs of 100% starch in every wet bushel of corn equates to needing 1057 bushels of corn grain to replace the loss in the silage (17.5 tons * 2000 = 35,000 lbs lost DM / 33.1 lbs starch in a bu = 1057 bu).
If a bushel of corn is worth $3.50, then the nutritive value of reducing DM shrink by 5% would be approximately $3700.00 (1057 bu * $3.50 = $3700.90). Taking this savings over the entire 1000 ton bunker, you save $3.70 in every ton of silage if you can implement management strategies (inoculation, better compaction, improved face management) which reduce shrink by 5%.
Keep the silage face clean to protect silage quality. Remove forage with equipment that minimizes fractures and oxygen penetration. Don't gouge the face with a front-end loader.
Data shows an average bunker silo loses 15 percent of its dry matter mass during storage and feedout. Good packing, a quality inoculant, appropriate bunker covering and using a defacer can lower losses to 10 percent or less.
DuPont Pioneer experts use an infrared camera to show the variation of heating throughout the bunker face. Increased heat levels indicate loss of valuable energy.
Inoculants help reduce these losses, and inoculants containing Lactobacillus buchneri help increase bunklife while protecting silage from heating and spoilage by microorganisms. Studies show Pioneer® brand inoculants containing L. buchneri bacteria reduce aerobic dry matter losses, making it an excellent tool to protect quality and maintain feed value in the silage.
Pioneer offers a wide range of inoculant products containing a combination of proprietary L. buchneri strains to increase aerobic stability and improve the quality of silage. Products include 11CFT and 11C33 for corn silage, 11AFT for alfalfa, 11G22 and 11GFT for grass or cereal silage and 11B91 for high moisture corn, earlage or snaplage. Pioneer also offers a variety of application technologies designed to work with all major brands of forage harvesting equipment.