Silage and hay are preserved feeds that come in handy for dairy cows during periods of scarcity of green forage. The process of making silage involves fermentation under anaerobic conditions. It prevents fresh fodder from decomposing and allows it to keep its nutrient quality. It requires sufficient soluble carbohydrates (sugars) for organic acid production. Adding molasses to the fodder is recommended since it is rich in sugar, which enables the bacteria to produce the organic acids immediately. The more molasses you add, the faster the acidification and preservation process will occur.
Why feed your cows on silage?
Silage ensures high milk production and healthy dairy animals, especially during dry seasons. It is palatable, laxative, digestible, nutritious and requires less floor area for storage than hay.
Silage is produced through use of pits or trenches, towers and sacks for small quantities. However, pits are mostly used to prepare silage for large dairy units. The silage pit should be located at a place safe from rodents, away from direct sunlight and with higher elevation or slightly sloppy to avoid rain water entering into the facility. The ideal materials used in silage making should have a moisture content of 60 to 70 per cent or dry matter in the range of 30 to 35 per cent (tested by taking a small bundle of the fodder and wringing with two hands and if no moisture comes out, it is ready to ensile) and a pH below 4.2 for wet forage and below 4.8 for wilted forage. In rainy periods when the fodder is too wet, containing more than 70 per cent water, it is advisable to wilt it in the sun first.
Crops such as maize, sorghum, oats, pearl millet, and napier grass are very suitable for ensiling (preserve green fodder). They contain fermentable carbohydrates (sugar) necessary for bacteria to produce sufficient organic acid that acts as a preservative. Though leguminous fodders can also be used, they are rich in proteins and low in sugars making them a bit difficult to ensile. Harvesting maize or sorghum for making silage is ideal when their seeds are soft but not milky when squeezed open. Napier grass, on the other hand, needs to be about a metre high while legumes should have young pods, which are not dry.
Apart from molasses, other additives like common salt, formic acid, lime or urea can also be used to enable good fermentation process. To start, prepare the pit and then place a big polythene sheet on the floor and walls. Cover about a metre of walls so that the forage does not come into contact with soil. Chop the fresh forage to lengths of about one inch using either a panga or a chaff cutter. Prepare the first layer by emptying the chopped materials into the plastic lined pit to approximately 15cm high, and spread evenly.
Then dilute molasses with water at a ratio of about 1:2 and sprinkle evenly over the forage layer using a garden water sprayer. Compact the layer by trampling on it using clean boots to force out as much air as possible. This will prevent fungi growth and spoilage. Repeat this process of adding bags of chopped forage, diluted molasses while compacting to expel maximum air out of the material until the pit gets filled in a doom shape. After the final filling and compacting, wrap the polythene sheet around the silage and cover the top of the heap with a second sheet to prevent water from running into the silage. Finally cover the heap with a thick layer of soil of at least 2ft giving special attention to the edges first as you come towards the middle to keep the air out and to prevent damage of the polythene by rain, birds and rodents. With good sheeting and enough soil on it, the silage can be kept for more than one year.
Opening the silage pit
It takes about 30 to 40 days for the silage to mature and be ready for feeding. Never open the whole silage pit at once. Only one end of the narrow side should be opened a bit. Remove enough material for each day’s feeding and cover again. This way air is prevented from entering the silage. However, once the pit is opened, use the silage as quickly as possible.
Silage can be classified as good quality depending on its physical characteristics like taste, smell, and colour but more precisely by measuring the pH in the pit. A pH of 3.5 to 4.2 indicates excellent fresh acidic/sweetish silage, 4.2 to 4.5 for good acidic, 4.5 to 5.0 fair less acidic and above 5.0 for poor pungent/rancid smelling silage. Good silage should be light greenish or greenish brown or golden in colour. It should have a pleasant smell like that of vinegar, and acidic in taste, and should not contain mould. Black indicates poor silage. Overheated silage has the smell of burnt sugar and dry in texture. Badly fermented silage has offensive taste, strong smell, slimy soft texture when rubbed from the fibre or leaf.
Feeding cows with silage
A dairy cow is fed depending on the body weight or generally be given about 6kg to 15kg of silage per day. It is advisable not to feed silage immediately before or during milking especially when the quality is poor as the milk can easily take the smell of the feeds. During these times, a cow can be fed fresh grass, hay, legumes and concentrates. After feeding silage, the bunks and corners of the feeding troughs should be cleaned immediately to prevent contamination.