Tips on how to make direct-cut vacuum silage

by Allan Nation

TULSA, Oklahoma: Research in the United Kingdom has found that direct-cut, un-wilted silage preserves much more of the healthful Omega-3 fatty acids than hay or wilted silage. As a result, this system is gaining in popularity with grass finished beef producers.

Direct cutting uses a flail-type chopper unit to cut the grass at relatively long lengths. This long length is better than fine chopping as it allows the animal to regurgitate the silage for rumination. Also, the less damage there is to the grass the less nutrient loss there is from effluent weeping.

Fine chopping is only necessary when upright storage structures are used. With silage stacks, the longer the cut the better.

High rpm flail choppers such as the Alpha-Ag Lacerator blow the cut grass into a following wagon or a truck alongside without the use of augers, which can damage the forage.

Approximately one tractor horsepower is required for each width of cutting face with this unit. For example, a six-foot-wide unit (72 inches) would require at least a 72-horsepower tractor.

Direct-cut silage is a one-pass operation whereas wilted silage requires at least two passes and two separate pieces of machinery - a mower and a chopper. This saves both time and fuel and requires less machinery investment.

For maximum quality, grass silage should be cut at the exact same stage of growth and height where it would be grazed for a high average daily gain. Too much grass silage is cut when it is too mature for high animal performance to maximize tonnage.

Silage cut in the afternoon is higher in sugar content than that cut in the morning and will produce better animal gains.

While some say silage can be cut in the rain, this is not advised. A light shower in the middle of a cutting may not hurt but do not try to cut silage in a pouring rain storm.

The cut grass is unloaded at the site where the silage stack will be built. No side walls or hard-surfaced floor is needed with this method as there is no need for tractor packing to exclude air. It can be built directly upon the ground.


The size of the silage stack will be determined by the size of the plastic sheeting used. There are plastic sheets available that are as large as 50 feet by 200 feet and as small as 24 feet by 100 feet.

However, the 40 x 100 size is probably the most popular. This is the equivalent of 40 to 50 large 1500-round bales and can easily be made in a day.

Making and sealing a stack on the same day minimizes wilting and subsequent Omega-3 loss.

The Europeans believe that multiple small stacks also lessen the risk of silage loss from an accidental plastic puncture.

Some have found shaping the pile with a front-end loader useful in making a smooth surface that will prevent the holding of rainwater puddles on the stack that turns to ice in winter. However, running over the cut material is not only unnecessary but will cause damage to the grass material and promote weepage.

The best site for a silage stack is where there is a slight incline for drainage. Also, building the stack close to where it will be harvested saves time and fuel.


A perforated pipe is centered in the site area. When the stack is about half done, lay a 10-inch piece of 4-inch sewer pipe on the ground so that the pipe extends from the center of the stack to the edge. Unload or push the next load of silage on top of the pipe. The stack is then completed.

White plastic is then pulled over the stack. White plastic is preferred to keep the silage stack cooler. Black plastic can result in extremely hot temperatures that can caramelize the plant sugars and lower its feed value.

Sand, dirt, ag lime or sandbags are then placed around the edges of the plastic to help create a seal. Then a small vacuum pump is connected to the pipe which was laid in the stack earlier and the air is removed from the silage stack.

After a few minutes of vacuuming, the pump is turned off and the extraction pipe is sealed. The silage is then allowed to ferment until it is used. Unlike hay which will lose quality over time because it is always exposed to the air, a vacuumed stack that stays airtight can be stored indefinitely without nutrient loss.

In New Zealand, sealed silage stacks intended for long-term storage are covered with a foot or more of dirt, and grass is planted on them. This helps prevent animal and rodent damage to the stack's plastic covering.


Once the silage stack has been opened the entire face should be removed each day to prevent spoilage. However, the stack does not have to be resealed as long as the use is continuous.

A silage grab or slice will help prevent deterioration as it is designed to leave a smooth silage face with long-cut material.

A New Zealand-designed, multi-purpose, transport-feedout wagon is available from Alpha-Ag in Illinois that is designed specifically to be used with grass silage.

An alternative is to stretch an electric wire across the silage face and let the animals feed directly. Solid fiberglass posts are best used for this. The rate of silage feeding can be controlled by periodically tapping the posts farther into the silage face.

If direct-feeding is to be used, the silage stack should not be built taller than four feet.

If self-feeding is used in winter, it is best to build the stack on a concrete slab otherwise it will become quite boggy at the silage face. This is particularly true during the early spring freeze-thaw period.

In areas where the ground freezes in winter, direct feeding at the silage face works well when the ground is frozen solid. No problems with the stack face freezing solid have been reported with such continuous direct-feeding although some have reported a "crunchy" texture.

Orienting the stack in a North/West, South/East direction and feeding from the southeast end will head off potential problems. Adding a little salt to the cut material will also help with face freezing.

In Argentina, direct face feeding is most often used in the late summer and early fall while waiting for winter annuals to be ready for grazing. Under such dry-season conditions, there is very little problem with bogging.

One problem with direct face feeding is that it concentrates the animals' manure in a small area. To get a more even distribution of manure, feeding the silage from a feedout wagon on the pasture under an electric wire has largely replaced direct feeding in most of the world.

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