Master Class Wrap

22 March 2011

More grass silage is wasted with big bale than clamp. True or false?

You might think the former, however remember the adage ‘never assume’, says Volac’s Jeannie Everington.

For starters, there are so many variables to forage making that no grass silage crop is ever ensiled and eaten with 100% efficiency. However research into the nutritional value of silage indicates that when properly made, with the right materials and correctly stored, bale silage can be of the same or better quality, with fewer nutrient losses than clamp.

For example, trials at IGER compared dry matter (DM) losses from grass for both clamp and big bale silage and found greater losses from the clamp. See Figure 1 for results.

Figure 1: Dry matter loss comparison

Source: IGER

Measurement of true losses of DM and nutrients during ensilage is extremely difficult.  Main losses are in the field: mechanical, biochemical (due to respiration and other enzymatic processes) and leaching; fermentation, effluent and oxidation losses occur during storage and aerobic spoilage can contribute significantly to DM losses once the bale or clamp is opened.

Ultimately, the nutritional value of your big bale silage will depend on the quality of grass harvested and the losses that occur during the fermentation and storage process.

The following 10 point Master Class big bale guide will enable you to maximise each bale’s value.

1.Harness as much grass potential as possible: growth can vary from 66 to 113 kg DM/ha/day during May alone.

2.Cut at the optimum time, before grasses reach 50% ear emergence when D-values, protein and sugar levels are high.

3.Wilt for 24 hours to 25% to 50%DM.

4.  Present the swaths well and use net wrap to make even and compact bales.

5.Use a good quality film to ensure that nutrients will be fully protected in the bale. New pre-stretched bale wrap gives a more effective air-tight seal which encourages enhanced silage fermentation.

6.Wrap round bales with at least four layers of high quality film.

7.For silage greater than 40%DM, wrap with minimum of six layers of high quality film. Note this recommendation is also for all square bales, heavy chopped bales and those for livestock sensitive to mould – horses, sheep and pregnant animals.

8.Traditionally, black wrap is used however green and white are proven to keep bales cooler and promote better fermentation, reducing spoilage and improving silage quality.

9.Wrap at the stack to reduce potential bale damage. Bales wrapped in the field should be carted and stacked in their final position using purpose built handlers within two hours of baling.

10.Good storage of bales is essential, away from trees, exposed areas and water courses on a level, well drained base free from any sharp stones. Stack round bales a maximum of three layers highbut keep to a single layer if they are of low DM material. Patch any bale damage at the earliest to avoid spoilage.

Remember, for every 1000 bales at 30% DM, each 1% DM fermentation loss is equivalent to 1.5t DM, and the cost of replacing that with concentrate at £200/tonne works out at £300, a figure that rapidly escalates to £2,100 if big bale losses average 7% DM.

Making top quality big bale silage will significantly reduce grass silage dry matter losses this season reducing the feed bill later on.

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