Producing quality silage
As silage season commences it is important to consider the key requirements for producing quality silage. Mark Treacy tells us more.
Grass growth stage will have a large effect on silage DMD so target cutting date at the correct growth stage for the quality of silage you are trying to produce. Where high quality silage suitable for milking cows and finishing cattle is targeted (74%+ DMD) leafy grass with no seed head will be required. As the seed head begins to emerge grass quality, and hence potential silage quality, will decline due to the increasing levels of fibre in the grass. A drop of 0.5 DMD can be expected for every day cutting is delayed after heading date. Where crops are lodged quality will deteriorate at a more rapid rate. Silage with a DMD of less than 68% DMD is poor quality and should be avoided if possible.
There are 3 key factors in the successful preservation of grass silage:
- Grass sugar levels
- Anaerobic Conditions
- Buffering Capacity
Adequate grass sugar is required to feed the acid producing bacteria. This can be measured using a refractometer, with 3% or higher considered sufficient. Where sugar levels are below 3% options such as delaying cutting until later in the day, wilting, or adding molasses should be considered.
Anaerobic conditions are vital as the desired lactic acid producing bacteria require these conditions. Where anaerobic conditions are not achieved undesirable bacteria will instead be encouraged. The creation of anaerobic conditions can be achieved by properly rolling the silage pit both during and immediately after filling, by paying attention to detail with covering, and by checking and retightening the pit covers again a few days after cutting as the pit settles.
Buffering capacity is affected by the nitrogen levels in the grass. High nitrogen grass has a higher buffering capacity and it is therefore more difficult to reduce the pH to sufficient levels for good preservation. However the importance of nitrogen levels in the grass is often overstated and where adequate sugar levels are present grass can be successfully preserved with in excess of 600 ppm of nitrate. Wilting of these crops will reduce the effects of the high N levels.