DES MOINES, Iowa — Growing conditions determine fiber digestibility, and the right combination of weather conditions make for an optimum silage crop, say experts at Pioneer Hi-Bred, a DuPont business.
While temperatures and moisture levels over the course of the growing season will set the stage, producers can actively take steps to preserve silage quality once the silage is harvested through good management, resulting in better feeding material for livestock.
Heat, temperature and light are key factors in determining fiber digestibility. In 2010, much of the U.S. saw higher temperatures with low to average rainfall. This combination was optimum for neutral detergent fiber. Cool and wet conditions lower NDF digestibility.
“Many corn producers struggled with getting crops in the ground this year due to wet weather conditions,” says Kevin Putnam, Pioneer dairy specialist. “No matter the conditions, good bunker management along with preserving forages on both the front and backend of fermentation is key to boosting the bottom line.”
Many factors play into nutritive losses — mainly improper harvest techniques and overall bunker management (ensiling and feedout). Harvest techniques, like crop maturity, dry matter and chop length, have profound effects on packing density and fermentation.
Knowing individual field conditions and hybrid maturities helps growers pick the appropriate harvest date. Experts recommend walking fields to examine crop maturity levels as harvest nears, helping determine if crops are on target for the expected harvest date. Under normal conditions, the tasseling date can serve as another way to check harvest timing.
Harvest is typically six to 10 days away when the crop is about 3 to 5 percent wetter than optimal. Outside factors such as weather and field location can affect the rate of maturity and ideal moisture levels for harvesting forage. Additional harvest timing and chopping tips can be found in the Pioneer nutritional sciences library at www.pioneer.com.
From there, all factors for preserving quality depend on keeping oxygen out of the forage mass. This is done in three ways, through packing density, covering the bunk/pile and practicing proper feedout management, i.e., defacers.
“As a general rule of thumb, experts suggest producers strive for an average packing density of 15 pounds of dry matter per cubic foot or better,” Putnam says.
Putnam recommends producers get that number closer to 17 dry matter pounds if possible to improve efficiencies.
“By increasing dry matter density by another 2 pounds, producers potentially save another 1.5 percent dry matter from oxygen penetration,” Putnam adds. “Dry matter loss is not fiber; it’s carbohydrates like sugar, so figuring the cost of the loss requires a producer to calculate the cost of replacing that 1.5 percent with an energy source such as cornmeal.”
Putnam suggests following the proper packing guidelines. He says layers spread 6 inches or less across the bunk is optimum. He also suggests using the rule of 800 when packing. Putnam says to multiply the number of tons coming in each hour by 800. That represents the total pounds of tractor-weight for packing.
“If you’re bringing in 100 tons per hour, that means using 80,000 pounds of tractor for packing per hour.”
After filling silos, producers should invest in plastic to cover the forage. They can secure the cover with a weight system. Some producers use tires to secure plastic covers. Other technologies are available for weighting and covering bunkers, such as gravel bags and oxygen barrier liners.
Producers can use plastic to line bunkers, reducing losses along sidewalls. They also can wrap the plastic over, doubling protection on top. If producers choose no cover, the top 3 feet of the forage pile essentially is the cover.
“Leaving a bunker uncovered causes silage to lose up to 45 percent of its nutritive value in the top 3 feet. This is especially important with drive-over piles,” Putnam says.
For those looking to estimate shrink losses or improve dry matter recovery, Putnam suggests a straightforward calculation.
“An easy guide is with 1,000 tons of silage in a bunker and shrink reduced by 5 percent, you save 50 tons,” Porter says. “Corn silage is worth roughly $45 per ton, depending on area. A producer can save $2,250 on 1,000 tons.”
If a producer uses Putnam’s system to replace energy source losses with cornmeal, the system is slightly more complicated,” Putnam says. “Fifty tons of corn silage at 34 percent dry matter is 17 dry matter tons. If cornmeal is 86 percent dry matter, this means you need 19.76 tons of cornmeal to replace the lost dry matter. If cornmeal cost is $280 per ton, then saving 5 percent dry matter could save the producer $5,532.80.”
Monitoring bunker management Putnam says producers need to keep the silage face clean to protect silage quality. Removing forage from the bunker with facing equipment minimizes the amount of fractures or oxygen penetration compared to gouging with a front-end loader.
“Data shows an average bunker silo loses 15 percent of its dry matter mass during storage and feedout,” Putnam says. “Not all of that can be managed. There is always going to be some loss from fermentation. However, with good packing, a quality inoculant, appropriate bunker covering and use of a defacer, losses can be limited to 10 percent or less.”
Pioneer experts use an infrared camera to show the variation of heating throughout the face of a bunker. Increased heat levels result in energy losses. Inoculation Lactobacillus buchneri is a form of management to reduce losses. Inoculants containing L. buchneri help increase bunklife and protect silage from heating and spoilage by microorganisms.
“Infrared cameras show the value of inoculants,” Putnam says. “Quality inoculants maintain or retain most of the forage quality from the field to the bunker. L. buchneri inoculants extend and maintain the quality from the bunker through feedout.”
Pioneer offers inoculants containing a unique strain of L. buchneri. This strain has the ability to convert some lactic acid into acetic acid and propionic acid, which are highly effective in improving aerobic stability of silage. Studies show Pioneer brand inoculants containing L. buchneri inoculants reduce aerobic dry matter losses, making it an excellent tool to protect quality and help producers get the most feed value from their silage.