Feed Preservation Techniques

Silage

The normal process of making silage depends on the transformation of soluble carbohydrates in the plant (or which are added to the silage) into lactic acid so that the pH of the silage drops to approximately 3.8 to 4.2. Well-made silage has a lactic acid content of approximately 8 to 12% of dry matter.

Silage at a pH of 4 is stable and can be preserved indefinitely as long as the anaerobic conditions in the silo are maintained. If rain enters the silage or if the lactic acid concentration is too low, then a secondary clostridium-type fermentation ensues where lactic acid is converted into butyric acid. Silage in which this spoilage has occurred has a pH higher than 5 and has a bad taste and smell.

Because this second type of fermentation can only take place in the presence of moisture, it is often recommended to wilt the plant material before ensiling and in this way reduce the moisture content of the plant material to between 65 and 70%.

If the plant material, which is to be ensiled, does not contain enough carbohydrates (for example, if lucerne is to be ensiled versus the more common maize silage), then external carbohydrates can be added.

This can be done by adding 2 to 3 percent molasses to the mixture and mixing well (20 to 30 kg of molasses per ton of silage) or by adding 45 to 55kg of maize meal to the mixture and mixing well. The well-made silage smells of fresh apples.

Any moisture-rich material can be ensiled if adequate carbohydrates are available. Also, the material must be chopped fine enough to allow effective compaction to ensure that anaerobic circumstances are maintained in the silo.

Materials as diverse as the leaves and trunks of banana trees, a mixture of oranges and cabbage, cosmos flowers, sugar cane tops, citrus pruning, and mango pruning have been successfully ensiled during research aimed at small scale farming at the Animal Nutrition and Products Institute of the Agricultural Research Council at Irene.

Drying

Plant material should be cut several times during the growing season. The quality of the hay is directly dependent on the stage of maturity of the plant when harvested: the younger the plant the higher the final hay quality will be. However, it must be remembered that younger plants are higher in moisture and thus that the drying process will take longer. Drying takes place on hot, sunny days, and ideally with a light breeze. The hay rows should be turned on the land several times to allow the hay to dry on all sides. When the hay is completely dry it can be raked and baled. Hay should be stored out of direct sunlight and away from moisture and pests such as birds and rodents.