Feed-out of grass silage
How soon after ensiling can silage be fed?
Ideally clamps should be left closed for at least four weeks although, if desperate, it can be fed within a few days even though the fermentation will not have stabilised by then. By opening the silo before the silage has settled properly, it also runs the risk of increased aerobic losses as the face will not be tight, allowing air to penetrate deep into the clamp. This is especially important with higher % dry matter forages that are not so well compacted initially.
If it is known in advance that a clamp is going to have to be opened early, rather than risk the main clamp, it would be better to make a small separate clamp or some bales.
How important is clamp management at feed-out?
Having produced high-quality silage it is vital that feeding-out procedure is managed effectively. Otherwise, high losses and reduced animal performance may result from aerobic spoilage (heating and moulding).
Unfortunately, the best-preserved silages are the most susceptible to aerobic spoilage because several of the products of a poor fermentation (acetic acid, butyric acid, ammonia) are inhibitory to the yeasts that initiate spoilage.
Tips for clamp management at feed-out:
- Have as narrow a face as possible
- Avoid overhangs
- Keep the sheet off the open face
- Maintain a tidy face (e.g. use a block cutter, shear grab or de-facer)
- Keep the face straight
- Clear up fallen silage regularly
- Discard mouldy silage
- With high % dry matter silage and/or during hot weather, move across the face faster by taking shallower bites with the shear grab
- It is generally recommended that clamps are crossed in 4 to 5 days in winter and 3 days in summer
What is the best way to remove silage from the clamp?
It is vitally important to prevent air penetrating the face to any depth. A block cutter is the best option as it causes minimum disturbance and leaves a neat, tight face. A shear grab is also effective but there is more face disturbance which leads to loose silage falling down. This should be picked up and fed immediately.
Another alternative is a silage de-facer. Whichever method is used, blades should be kept sharp. The worst option would be a bucket on a fore-end loader lifting the face, leaving a loose, cracked face and a lot of fallen silage.
Dry matter losses at feed-out vary tremendously, e.g. over a four-day period they could be as little as 1% with a well-compacted, well-sealed silo with an undisturbed face or as high as 15% where compaction and sealing have been poor and the face has been loosened.
How quickly should the silage face be moved back?
Move the face back at least 1 metre per week in cold weather and 2 metres per week in warm weather, especially with silages over 30% dry matter.
Should the silage sheet be pulled down over the face at night?
No. This is a very bad idea as it will create a warm, humid area behind the sheet, encouraging yeast and mould growth.
Always keep the sheet rolled back off the face but weigh the front edge down to prevent air getting under the sheet. During periods of very heavy rain it can be pulled down temporarily to prevent rain soaking into the face.
How is silage quality judged?
The quality of silage can be judged in a number of different ways, all of which are vitally important for maximum animal performance:
Nutritional value – characterised by measurements like metabolisable energy (ME), crude protein, digestibility (‘D’ value) – factors that are influenced mainly by the quality of the initial crop, but some of which can also be better preserved by use of an additive, although it is important to check the additive has proof of this.
Fermentation quality – characterised by measurements like pH value, ammonia-N, lactic acid content, volatile fatty acid content. Good silages are characterised by a suitable pH of 3.8 - 4.5 depending on the % dry matter; a low ammonia-N (NH3 - N) of less than 10% total N; and a high ratio of lactic acid to volatile fatty acids of a minimum of 3:1 or higher.
Keeping quality – this refers both to the stability of the initial fermentation, i.e. whether it is at risk of undergoing a clostridial secondary fermentation during storage, and to the susceptibility of the silage to aerobic spoilage on exposure to air. If the final pH is low enough for the % dry matter of the silage there should be little change in the fermentation parameters during storage. Unfortunately, the better the outcome of the fermentation, the more at risk the silage is to aerobic spoilage as lactic acid will not inhibit the yeasts and moulds that cause it.