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Reduce costly silage shrink losses

PD Editor Karen Lee Published on 19 March 2013
“With today’s high costs, forage best management practices are required for dairymen,” Troy Brown with Cargill said at the Midwest Forage Symposium in Wisconsin Dells, Wisconsin, earlier this year.

Brown went on to outline the cost, cause and cures for silage shrink.

“Cost of shrink today is very significant,” he said.

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Dairy producers know this and many of them have installed scales and adopted a system of weighing forages in and out, but it is important to know the difference between forage shrink and dry matter shrink.

In an example, Brown said a producer can weigh all forage delivered and packed in the bunker and all forage fed to the animals. With these numbers he can calculate a weight loss of 5.25 percent, which is considered acceptable. But is that forage shrink or dry matter shrink?

He shared the work of Brian Holmes with the University of Wisconsin Extension that used 65 percent moisture corn silage. At 100 pounds of as-fed feed, he derived 35 pounds of dry matter. A 5.25 percent shrink loss on the 100 pounds of feed would be a 5.25-pound loss of feed.

Considering there is very little moisture difference in the as-fed feed, there is little to no loss of water. This means the 5.25-pound feed loss is all dry matter.

To calculate the dry matter loss, he took 5.25 pounds divided by 35 pounds dry matter to get a 15 percent dry matter loss.

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A conservative estimate of $50 per ton corn silage at 32 percent dry matter would equate the cost of that feed to $156.25 per ton of dry matter.

At 10 percent dry matter shrink that cost rises to $171.87 per ton dry matter, 20 percent shrink would be $187.50 per ton and 30 percent shrink would be $203.13 per ton.

“Reducing corn silage shrink 5 percent is worth $3.78 per ton when the energy and dry matter are replaced with $6 per bushel corn,” he said, adding, “You always have to factor your dry matter in.”

Shrink can come in many forms including delayed harvest, mechanical, forage moisture, wind, transfer to storage facility, filling storage facility, fermentation, surface management, wind, birds and rodents.

The list continues with bunker seepage, poor facility design, feed refusals, hot feed, spoilage, mixing error and scale inaccuracy.

Brown cited another study by Holmes, this time in collaboration with Richard Muck of the U.S. Dairy Forage Research Center, that showed type of storage doesn’t always impact shrink.

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“You can do as good of a job with piles and bunkers as you can with bags,” he said.

One way to identify storage and feed-out challenges is to monitor temperature.

There are two types of silage heat, he said, physiological heating and microbial heating.

Physiological heating is the heat produced by plant respiration during ensiling.

In normal fermentation temperatures are typically between 90 degrees F and 110 degrees F, which allows the bacteria to flourish. Much of this heat remains trapped in the silage.

Don’t be alarmed if you see condensation on a cold day, Brown said.

If the feed begins heating beyond five to 15 degrees above the ambient temperature it was harvested at, it could signal some challenges.

Microbial heating is the secondary heating that occurs after air has been reintroduced to the fermented silage.

“If you have a secondary heating problem, you have an air problem,” Brown said. “With microbial heating, feed temperatures will drop as you dig into the silage where there is less air penetration.”

This undesirable heating is caused by yeast and mold. It is common in corn silage and high-moisture corn and typically brought in from the field during harvest.

It can also be found in grasses and legume silages, especially when harvested at less than 50 percent moisture.

More than 90 percent of the yeast population consumes lactic acid, which raises the pH and creates an environment conducive to mold growth.

Common causes and areas where heating occurs are when silage is faced for an extended period of time, uneven or jagged cuts on the silage face, along sidewalls or other areas where poor packing has occurred and the top and sides of silage bags where dry matter densities are low.

To reduce the incidence of heating, Brown recommended managing forage to prevent air penetration and treat forages with the correct additive specific to the situation.

There are some inexpensive tools to measure heat, including data loggers, infrared thermometer guns, compost thermometers and indoor/outdoor digital thermometers.

More expensive thermal imaging cameras are becoming more prevalent in diagnosing heating challenges in stored forages.

Heating challenges go beyond feed losses to impact milk production.

A 30-degree temperature rise burns up 13 Mcal of energy, depending on forage moisture. That represents a minimum of 40 pounds of milk per ton.

“The longer the high temps remain, the greater the impact,” Brown said.

Palatability issues also occur from heating, which reduce the intake of forages that are already lower in nutrients, he added.

Brown offered four steps to achieve single-digit shrink.

“If you go home and just start to incorporate some of these management practices, I can assure you’ll be a more profitable dairy,” he said.

1. Achieve a low silage porosity sore or a high silage dry matter density score
Bunkers or piles should be packed tightly. Silage should be spread in six-inch layers or less, decreasing in thickness as elevation increases.

The thumb rule is to apply 800 pounds of packing weigh for every ton per hour delivered to the bunk.

Since it’s not practical to slow down harvest, Brown recommended adding weight with more tractors or bigger tractors, filling the bunker or pile to a greater depth and/or focusing on improving packing procedure.

“The most important person in this process is that guy in the pack tractor,” he said. “He doesn’t have to be best employee in your operation, but he has to be the most engaged.”

2. Provide an effective seal
When covered properly, the improvement of feed quality provides an $8 return on investment for every $1 spent on covering.

Brown encouraged the use of two sheets of plastic, including thin, non-permeable plastics and covering sidewalls.

3. Apply a high quality inoculant
Inoculants produce more lactic acid, which results in faster, more efficient fermentation. This improves dry matter recovery 2 to 6 percent. Improved forage quality can also improve animal performance, he said.

However, inoculants cannot fix all of the problems in a poorly managed forage system, he cautioned.

4. Manage the exposed forage during feed-out
To minimize dry matter losses after opening the silo, Brown suggested using facing equipment, sizing the bunker properly to remove at least 12 inches per day and to feed the silage within 24 hours of removing it from the silo.

In closing, Brown’s standard bunker best management practices are to treat with a high-quality, crop-specific inoculant, incorporate proper packing procedures, cover it with plastic and manage the exposed feed. PD

00_lee_karen

Karen Lee
Editor
Progressive Dairyman magazine

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