Silage hybrids continue to be adapted for a wider geographic range and varying agronomic conditions. Thus, silage is being counted on in more backgrounding and specialty feeding operations.

Many of those producers are turning to the economy of open pits or bunkers to make and store silage. Under those conditions, the basic rule of ensiling becomes increasingly critical — keep the air out.

Silage quality may be more important in backgrounding rations than in finishing rations, says Mike Harkness, Scott City, KS. He's owner of Harkness Cattle & Land — a cattle enterprise that includes cattle backgrounding and finishing.

“There's a higher percentage of silage in the backgrounding ration,” says Harkness. “And it's just good feeding practice to give those young and growing cattle the best feed you have.”

Whether it's his own crop or corn purchased locally, Harkness says there's no substitute for a good chop and proper packing to keep the air out, especially when putting silage up in a bunker. He likes a ¼-in. cut and packs with his heaviest-wheeled tractor.

Harkness also uses a Lactobacillus plantarum-based inoculant and likes to ensure an airtight environment by covering his silage pile with plastic when at all possible.

Often, producers do an excellent job producing a high-quality corn plant only to suffer significant quality losses in storage or feedout, says Bill Mahanna, Johnston, IA. He's a Pioneer Hi-Bred ruminant nutritionist and a leading silage expert.

“Consistency is the name of the game in silage production. That means doing everything you can to make every bite taste and smell the same,” explains Mahanna. “Proper moisture helps when it comes to packing silage and helping exclude oxygen from the bunker.”

Silage hybrids should not dry down too rapidly in the fall, says Mahanna. This ability to “stay green” is an important silage trait because it also prevents too rapid a reduction in whole plant moisture, providing a wider window for harvesting the crop.

Relying on visual assessment of maturity for harvest can result in a crop being much drier than observations would suggest. Overly dry silage is more difficult to compact, and fermentation will be less desirable.

The Milkline Method

The best method to assess maturity is to chop some silage and use a moisture tester. Another indicator of whole plant moisture is to monitor the kernel milkline, he says.

Mahanna suggests walking 10-15 rows into the cornfield and snapping several ears in half.

“As the kernels dry from the top towards the tip, you'll see a line dividing the milky endosperm from the hard starchy endosperm,” he says.

When the kernels reach early-dent stage, the milkline is about ⅓ the way down toward the tip and the plant's moisture level is about 72%. “This is the ideal time to begin chopping for ensiling in a pit or bunker silo,” he advises.

At the well-dented stage, the milkline is about ½ way toward the kernel's tip, and the whole-plant moisture is about 65%. This is the ideal stage to begin chopping for ensiling in an upright silo.

The milkline eventually disappears and a black layer of cells will be visible at the kernel's tip. Waiting until this stage to harvest will result in silage less than 60% moisture — too dry for proper compaction and fermentation.

“The key is to eliminate oxygen as soon as possible after the silage is placed in the bunker,” adds Mahanna. “Be sure your packing capacity can keep up with how fast the silage comes to the pit.”

Forage experts point out that a hard frost will stop maturity, and moisture levels will even out across all maturities.

“Once frost hits, everything left in the field will be ready to chop at the same time,” says J.W. Schroeder, North Dakota State University Extension dairy specialist.

Keeping Up With The Cutters

A good pack is so important to Jay Hasbrouk, Ault, CO, that he switched from a six-row to a four-row chopper to reduce harvest speed. Hasbrouk backgrounds and finishes 5,000 calves and 60,000 lambs/year. As owner of Double J Farms and Feeding Inc., he puts up 17,000 tons of silage/year.

“The biggest challenge is keeping up with the silage cutters,” he says. “It's easy for the choppers to get ahead of the packers.”

Reducing cutting volume makes everybody slow down and do a better job of making silage, he says.

“Patience is the key — and everybody tends to start a little early anyway. But you want to wait and cut the corn at the right stage of maturity.”

Hasbrouk produces beef for Laura's Lean Beef and Coleman Natural Products, as well as his own brand — Double J Signature Cuts. To get as much “natural-based” nutritional boost as possible, Hasbrouk also uses a Lactobacillus plantarum inoculant available from Ecosyl Products Inc.

“It's perfect for starting calves. We get good fermentation and don't see the spoilage or sourness we might otherwise see,” he says. “It's just one more step in producing consistent silage. And it stays fresh whether it's a year old or more.”

Juan Reyes, Wheatland, WY, puts up about 20,000 tons of silage/year for his backgrounding and finishing feedlot. He makes silage from grain corn and feeds it all before the next crop is harvested. He says the extra cost of inoculant doesn't fit his program.

“Maybe if I carried some silage over it would be a different story,” Reyes says. “For the cost of adding inoculant, though, I can go out and buy quite a lot more silage if I need it.”

He maintains that a good pack and a fine chop do wonders for a silage crop.

A significant number of maturity studies on corn silage digestibility have been conducted. Most suggest that increasing grain content of the forage during grain fill will eventually be negated by the increasing cell wall content (and reduced digestibility) in the stover portion of the plant.

The general conclusion is that while grain content is important for energy density, increasing maturity beyond the _ milkline stage may result in corn silage with reduced energy content.

Storage Matters

Whatever the storage facility though, quality losses are primarily attributed to respiration, effluent and aerobic deterioration.

Joe Harrison, Puyallup, WA, recommends layering the corn forage into a bunker silo at depths of 6 in. or less and packing to a rate of 2-3 minutes/ton. The Washington State University (WSU) forage nutritionist says this can be done when forage delivery is in the range of 40 tons/hour. Greater delivery rates require larger tractors or multiple packing tractors, he adds.

Harrison suggests producers cover their bunkers with plastic (preferably white) held down with tires. Check the plastic regularly to ensure it's well sealed.

“Bunker silos are an inexpensive and convenient way to make, store and use silage,” says Schroeder. “Use hybrid maturity information, planting dates and moisture levels to plan a harvest sequence that will put the driest silage in first and finish with the wettest.”

For unavoidably wet corn silage, adding a drier feedstuff may be an option.

“In some regions, it's common for grain, beet pulp, grain screening pellets or alfalfa cubes to be layered into bunkers of wet corn silage,” he says. “Adding these drier feeds holds moisture and prevents effluent, as well as changing the feeding quality of the silage.”

Barley can reduce fiber and increase crude protein and digestibility of the mix. The addition of 10-15% barley (200-300 lbs./ton) reduced the overall moisture content to levels suitable for ensiling in WSU studies. Fermentation acids and pH are generally not affected by adding barley to the silage.

Schroeder cautions that adding absorbents can be inconvenient, and if the grain is moldy it can contaminate the silage. “Also, if an absorbent is added, that level of concentrate must be fed for as long as the silage lasts,” he says.

For the best feed out, it's best not to “buck” into the silage mass when removing silage as this allows channels for the entry of air back into the silage mass. “The face of the pile must be managed carefully or the quality of the silage will be inconsistent,” concludes Schroeder.

Respiration Checklist

Whether it occurs during wilting or after storage, silage respiration involves the oxidation of sugars by plant cells or aerobic microflora, producing carbon dioxide, water and heat. Excessive respiration can severely degrade dry matter and nutrients in fermented corn silage, says Bill Mahanna, a Pioneer Hi-Bred ruminant nutritionist. His checklist for minimizing respiration losses includes:

  • Control moisture content. A 65-72% moisture level for bunker silos allows superior packing and thus the exclusion of more oxygen in the silage.

  • Chop corn silage at a length to allow compaction. Most recommendations indicate ¼- to ⅜-in. length of cut. Chopping finer than ¼-in. may increase effluent losses.

  • Fill and build the face of the bunker quickly to reduce exposure to oxygen. Slow filling or delays increase respiration loss and could encourage surface deterioration or deterioration in the feed bunk when the forage is re-exposed to air.

  • Pack the silage densely.

  • Prevent air penetration into the storage structure. Air leaks in upright silos, holes in bags, and bunkers or piles uncovered with plastic/tires encourage respiration losses.

Find publications and software-based tools for silage storage at www.uwex.edu/ces/crops/uwforage/storage.htm. Look for the spreadsheets entitled “Bunker Silo Density Calculator” and “Bunker Silo Sizing Spreadsheet.”