Growing Silage Corn in China

Advantages of Silage Corn for feeding Livestock

An important reason why silage corn is beneficial for feeding livestock is the high starch con-tent in comparison to grass. The starch is contained in the cob and has a very high digestibility (more than 90%). Because of this, silage corn is an excellent energy supplier in dairy cow feeding. While the cob delivers starch, the stalk and leaves of the corn mainly deliver fiber. This fiber can be divided into different fractions and is important for rumination. Overall silage corn is characterized by a good taste, a high energy concentration and a high yield compared to other fodder crops as e.g. grass silage.

Evaluation of Silage Corn Varieties

The assessment of silage corn is more complex than grain corn and takes different parame-ters into account. A first key reference point is the energy yield measured in Gigajoules Net Energy / Lactation per hectare (GJ NEI/ha). It expresses how much energy out of the harvest of one hectare can be used by the cow for milk production.

A second parameter is the energy density (MJ NEI/kg DM). It describes the energy content of one kilogram of dry matter and is measured in Megajoules Net Energy Lactation.

A third criterion is the starch yield which measured in metric tons per hectare (t/ha).

These three yield parameters are influenced by the proportion between cob and vegetative parts of the corn plant. Now, which is the right silage corn variety? It depends on the circum-stances of each individual farm. Criteria that need to be factored in are the dietary composi-tion of grass and corn, the availability of land as well as the cost of land. Inner Mongolian Farmers in general are feeding a lot of grass to their cows. In comparison to corn silage, grass silage has zero starch and normally a lower energy content but a higher protein content. Con-sequently, farmers can improve the feeding value by adding corn silage. Under these circum-stances it is recommended to grow a variety where the cob takes on a high proportion of the corn plant as whole (more than 50%). Because of the high grain proportion, the corn silage of this variety has a high starch and energy content. So, this corn silage can compensate the lack of starch.

In contrast to this, farmers facing a shortage of land should grow a variety with a high energy yield per hectare. For these farmers, a high milk production per hectare is the most important factor when choosing a corn variety.

The optimal point of time for Harvest

A key issue for successfully growing silage corn is the right harvest point of time. Whereas the optimal harvest time for grain corn is mainly determined by the moisture content of the grain, for silage corn the optimal harvest point of time is between 30% and 36% dry matter content of the corn plant as a whole, but not later than black layer stage (ca. 35 % water con-tent in the grains). Depending on the variety and weather conditions, the optimal harvest time is often reached before black layer stage - normally between 40-50 % water content in the grains. At black layer stage, the incorporation of starch in the cob is finished. For this reason, it is not recommended waiting with the harvest beyond this point of time as it will only lead to quality losses.

If harvest is too late, the vegetative parts of the plant will turn brown leading to deterioration in digestibility of the silage. The energy content of the silage will decrease.
Furthermore, the preparation of the silo will become more difficult because of the high dry matter content of the silage. Besides that, the sugar content in the corn plants decreases. However, sugar is very important for the development of lactic acid, which is required for the ensiling process. Therefore, too late harvest times can hamper the success of the ensiling process leading to quality losses.

On the other hand, harvesting too early will bear server risks as well. In general, the dry mat-ter content of the silage will be too low. Due to this, the decrease in pH-value will not take place as fast as normal because of the high water content in the silage. A fast decrease in pH-value is very important to hamper the occurrence of harmful yeasts and fungi during the ensiling process. Therefore, low dry matter contents also have negative quality consequences for the quality.

Conservations and Storage

The key target for a good silage management is the conservation of the harvest. Particularly, dirt and mud are a source for contaminations with undesirable microorganisms. They are mostly prevalent on the lower parts of the stalk. Therefore, the harvest should take place dur-ing good weather.

The silo filling needs to be done quickly, paying attention to an even distribution of the silage. Corn Silage needs to be compacted in a right way with a storage density of min. 250 kg dry matter/m3. This is an essential prerequisite for adequate fermentations processes. The opti-mal value increases with an increasing dry matter content. As it is more difficult to get a good compaction when dry matter content increases, a shorter chopping length should be chosen. The following recommendations apply:

• In general: 4 – 10 mm
• If dry matter content is < 34 %: 8 – 10 mm
• If dry matter content is > 34%: 4- 8 mm

To get high quality silage, it is also important that all kernels are cracked. Many uncracked kernels reduce the digestibility and energy content of the silage.

After filing, the silo needs to be covered with foils that are usually weighted by sacks or tires.

The occurrence of air pockets needs to be avoided. When opening the silo farmers need to prevent excessive air suction in order to maintain the quality of the silo.

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