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close this bookUtilization and Construction of Pit Silos (Peace Corps, 1976, 41 p.)
View the document(introduction...)
View the documentEnsilage hay and pasture crops
View the documentHarvesting silage crops
View the documentHandy silage preservative guide
View the documentCharacteristics of high quality hay
View the documentStorage of forage
View the documentCorn or sorghum silage vs. grass silage
View the documentPit silos
View the documentProject ensilage - Interim report
View the documentProject ensilage - Termination report

Harvesting silage crops


Most grasses should be cut after the heads have emerged but before the plants have started to bloom. Dalays in harvesting beyond the early heading stage in grasses decreases palatability and digestibility of the forage. Each day's delay decreases digestibility about 0.5 percent, which in turn results in a decline in production of the animal fed silage from too nature a grass.

If the percentage of water in the silage is too high, an undesirable type of fermentation often occurs. The losses of nutrients are increased, and strong-smelling butyric acid is formed, instead of lactic and acetic acid. If the forage is too dry, it is apt to mold.

Harvesting silage crops can be classified as "direct cutting," where the forego is ensiled directly after being field cut, or "wilting," where the forage is partially field dried so that it contains 60-70 percent of moisture when stored.

In wilting forages, one to two hours on a good drying day may be sufficient to wilt the crop to the desired moisture level. You can estimate moisture content by a squeeze test. Squeeze a handful of the chopped forage into a ball and hold it 20 to 30 seconds, then quickly release your grip. The condition of the ball shows About how much moisture it contains. Following is a guide for estimating moisture content:



Ball holds shape, considerable free juice

over 75%

Ball holds shape, little free juice

70 - 75%

Ball falls apart, no free juice

60 - 70%

Ball falls apart readily

below 60%

Another means of quickly judging the degree of wilting achieved, is visual. If the leaves become dry and curled, the wilting may have proceeded too far. The crop will have wilted sufficiently when the leaves and stems become limp, or, the stems can be readily twisted in two and the broken ends will have a dark, moist, but not excessively juicy appearance.

Wilting has the advantage of not only reducing the nutrient loss from leaching due to excess water, but also increases the amount of sugar per pound of forage.

Wilting, as compared to direct cut silage has the disadvantage, that excluding air from wilted silage in the silo is more difficult. The lighter, wilted silage will not pack as tightly in the silo. For this reason, if the wilting process is followed, the last few layers of silage put in the silo, should not be left to wilt. In this way, additional weight will be placed on the top of the silage, which pushing down, will help to force out any air within the silo.

Wilted silage made without preservatives usually has an acidity within the PH range of 4.0 to 5.0, depending on the crop.

It should be kept inmind, that in a dry season or with rather mature crops, the forage need not be wilted.



From test pit silos made in Chad, 1971-72, the following analysis of a silage sample was made. The grass used was roetebella exalta, with no additives:

Dry matter

35.2 percent

Total Digestible nutrients

45 - 50 percent


5.6 percent


1.5 percent


35.0 percent


14.5 percent

Non protein

50.0 percent



Balancing a ration involves finding a combination of feeds that will supply the required nutrients for an animal of a given weight. For example, the daily requirements of an 800 pound yearling finishing steer are:

Dry matter

19.8 Ibs.

Digestible protein


Total Digestible nutrients







.45 mg.

To maintain weight, a beef cow needs about 2 pounds of dry matter daily per 100 pounds of live weight.



Often times, the fermentation of high moisture forego is unpredictable and for this reason, preservatives are sometimes added. additives should do at least one of these things to be of help:

- Provide fermentable carbohydrates (60 to 100 pounds - 7 gallons - of molasses per ton increases the auger content) so that enough acid forms during fermentation to preserve silage properly.

- Furnish additional Acids directly to increase acid conditions. (liquid P202 can be used in amounts of 9 Ibs. of 68 percent phosphoric acid per ton).

- Directly or indirectly reduce the amount of oxygen present.

- Absorb some seepage that might otherwise be lost.

When the crop is wilted, less of the preservatives are needed, because at that moisture level the fermentation process is slowed down, less undesirable fermentation is produced, and the losses (except of carotene) are usually small.

Additives which can be used with grass silage:

- Mixing in green corn or sorghum
- Molasses or whey
- Cereal grains
- Acids such as phosphoric
- Treat with sulphur dioxide gas
- Use sodium bisulphite - 81 Ibs or powder per ton.