Filling a silo

Written by Maurice Rangoma.

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When filling a silo additives may be added to increase the starch and sugar for microbes to act on and therefore produce the required acids. This is especially important if legumes compose a large part of the plant material to be ensiled.

Walls and floor should be covered with polythene sheet, then the top to control air flow. Later when continuing filling, the top polythene is removed, filling follows, and then covering again with polythene paper. This process is repeated until the silo is full. A layer of soil is applied on the top when filling is complete. Compression is done after each filling.

Young plants have high content. This reduces temperature therefore decreasing fermentation. Filling should therefore be done faster. Mature plants have more DM hence temperatures are raised and may cause excessive heating. Immature plants or water can be added to stop excessive heat.

To ensure satisfactory fermentation the crop should be chopped into small pieces. Large pieces make compaction difficult and air pockets leads to aerobic respiration, heat releases and overheating. The resulting silage is of poor quality.

Loading of silo should be progressive so that when the end is reached the material for ensiling is leveled off to give a uniform finish. The exposed slope should be covered with polythene sheet during breaks in filling and at night to ensure as little air as possible is in the ensiled mass.


Adequate compression is necessary to restrict loss of carbohydrates by respiration while leaving sufficient air in the mass to allow aerobic bacteria to convert carbohydrates to various organic acids. These organic compounds are lactic acids, acetic acids, propionic acid and butyric acids. Lactic acid is the most important. Presence of butyric acid indicates secondary fermentation therefore low quality silage.

Inadequate compression as with stemmy material leads to excessive respiration and overheating. This is accompanied by high losses of DM, reduction of digestibility of proteins and loss of carotene. Over compression on the other hand as is experienced when succulent herbage material is ensiled leads to overheating. The result is a foul smelling product unpalatable to livestock.

Good silage is made over temperature range between 10 and 38oC, the optimum being 32oC. Chopping of forage or crushing stemmy coarse plant material assists in compression. Materials with high moisture content should be wilted before ensiling. When ensiling young plant material with low level of carbohydrates, additives should be added. These additives ensure that lactic acid bacteria dominate other microbes in the silage making. Additives influence the type of fermentation hence the nutritive value of the resulting silage.

Additives used in silage making


These stimulates production of lactic acid and are exemplified by molasses. sucrose, potatoes and cereals

Inhibitors of microbial activities

They inhibit microbial growth partially or completely e.g. sodium hydroxide, carbon dioxide, sulphur dioxide, citric acid, acetic acid, formic acid and formaldehyde.

Inhibitors of aerobic deterioration of silage on exposure to air

Is exemplified by propionic acid. Improves nutritive value of silage e.g. urea, ammonia, cereals, molasses, sucrose and potatoes.

The most common additive is molasses added 3 – 4% by weight and diluted with equal amount of water and applied as spray.