Bunker Management Boosts the Bottom Line

By Kevin Putnam, DuPont Pioneer Dairy Specialist

Preservation of forage nutrients - on both the front and back end of fermentation - along with good management can improve an operation's bottom line.

Management during harvest, storage and feedout affects nutrient losses. During harvest, factors such as crop maturity, dry matter and chop length have major effects on packing density and fermentation. Knowing individual field conditions and hybrid maturities helps producers target a harvest date and field-by-field schedule. Walking fields as the target harvest date nears allows growers to check crop maturity and pinpoint harvest timing.

The whole process of preserving nutrients starts at harvest: Making sure the crop is harvested at optimal maturity or dry matter will have a positive effect on the rest of the process. Be aware that weather, field location and other factors can affect maturity rates and moisture levels during this period.

During the ensiling process, success depends on keeping oxygen out of the forage mass. Packing density, bunker or pile covering and proper feedout management are the big three when it comes to limiting oxygen access.

Packers can’t be slackers

Experts suggest an average packing density of 15 pounds or more of dry matter per cubic foot or better. Achieving 17 pounds and above can improve efficiencies. Increasing dry matter density by just 2 pounds can save another 1.5% dry matter from oxygen penetration. These losses are in the form of carbohydrates like sugar: The value of losses is equal to the cost of replacing that 1.5% with an energy source such as corn meal.

Follow proper packing guidelines. Spread layers of 6 inches or less across the bunk. Use 800 pounds of packing equipment weight per ton of forage entering the bunker each hour. If you deliver 100 tons per hour you need 80,000 pounds of tractor for packing the pile.

Covering your assets

Protect the bunker or pile with an effective covering. Many producers use tires to secure covers. Other technologies are available: gravel bags, oxygen barrier liners, etc. Lining bunkers can limit 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 face clean

During feedout a majority of the dry matter loss can happen. Producers can protect silage quality by keeping the silage face clean. Use facing equipment to remove forage from the bunker. This minimizes fractures or oxygen penetration versus gouging with a front-end loader.

An average bunker silo loses 18% to 20% of its dry matter mass during storage and feedout. Good packing, a quality inoculant, appropriate bunker covering and use of a defacer can limit these losses to 15% or less.

Replacing the lost nutrients can be even more expensive. The true way to calculate the economic effect is to compare to the cost of energy (corn meal) to replace that loss, because what's lost during fermentation is the energy and not the fiber portion. For example, 50 tons of corn silage at 34% dry matter equals 17 dry matter tons lost. If corn meal is 86% dry matter, a producer will need 19.76 tons of corn meal to replace lost dry matter. With corn meal at $280 per ton, preserving that 5% dry matter could save the producer $5,532.80.

Inoculants offer value

Inoculation can reduce losses. Inoculants containing Lactobacillus buchneri bacterial strains help prolong bunklife and protect silage from heating and spoilage. Quality inoculants help limit microorganism growth that results in heating. Pioneer offers inoculants containing unique strains of L. buchneri that convert some lactic acid into acetic acid and propionic acid, which improve aerobic stability. Studies show Pioneer® brand inoculants containing L. buchneri strains reduce aerobic dry matter losses, helping producers protect quality and get more feed value from their silage.

Pioneer offers a wide range of inoculant products with proprietary L. buchneri strains to increase aerobic stability and improve the quality of silage. Among these products are 11CFT and 11C33 for corn silage, 11AFT for alfalfa, 11G22 and 11GFT for grass or cereal silage and 11B91 high-moisture corn, earlage or snaplage. Check with your DuPont pioneer forage expert or Pioneer sales representative for more information.

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