Two-thirds of farms make baled silage each year, and on many cattle farms in particular it is the silage-making system of choice.

These baled silages span a wide spectrum of quality, ranging from top grade feed with a nutritive value similar to grazed grass through to low grade feed incapable of meeting an animal’s maintenance requirements. In many cases, the cost of producing excellent or bad quality baled silage is the same, but the rewards are considerably greater with the good quality feed.

Although crop yield is always important, it is less influential in determining the feed cost of baled silage compared to pit silage since contractor harvesting costs are per bale rather than per hectare.

SILAGE QUALITY

Baled silages of excellent nutritive value will have high intakes by cattle or sheep, and will be efficiently converted to meat and milk.

These excellent bales of silage will be:

Whereas chop length is not directly important with cattle, shorter silage particle length can be beneficial with sheep.

HIGH DIGESTIBILITY

The baled silage on each farm should contribute appropriately to the specific energy needs of the cattle or sheep being produced.

Thus, high silage digestibility (eg 73+% digestibility) is required for animals that are expected to reach a high rate of performance while consuming silage, whereas a more moderate digestibility (65-67%) is appropriate for dry spring-calving beef cows, store cattle, etc.

In contrast, silages of less than 64% digestibility are rarely appropriate in commercial farming systems. Major factors determining the digestibility of baled silage are:

Sward type: The planned production of highly digestible baled silage is more easily achieved with perennial ryegrass swards. In contrast, moderate digestibility baled silage can be made with virtually any sward.

Previous management: The main requirement here if producing highly digestible baled silage is to avoid the presence of dead vegetation at the base of the grass crop.

Experiments at Grange found that such accumulations of dead vegetation reduced overall digestibility by about seven percentage units. Grazing swards down to a 5cm stubble height in autumn or in early spring avoids this problem.

Grass growth stage at harvest:

High digestibility depends on mowing the crop while it is still dominated by leaves and young stem – ie before seed-heads emerge fully. In the same context, paddocks or fields identified as surplus to requirements within a rotational grazing system can also produce baled silage of excellent digestibility.

Losses: Slow or intermittent wilting (eg due to prolonged, heavy rain on partially wilted grass), poor preservation or imperfect sealing of the bales will reduce the potential digestibility of the baled silage.

GOOD PRESERVATION

All baled silage needs to be well preserved. This means it must be stored in an air-free environment and must be appropriately fermented. Factors that influence the preservation of baled silage include:

Sward type: Ryegrass-dominant swards are inherently much easier to preserve as baled silage compared to grass swards dominated by non-ryegrass species. This is because ryegrasses have a much higher content of sugar which is needed to fuel the preservation process. Quick and adequate wilting can largely overcome this potential limitation with non-ryegrass swards.

Fertilizer and slurry/manure:

The effective rate of nitrogen application can be up to 125kg N/ha for a first-cut, and this should be applied at least six weeks prior to mowing. Excess nitrogen or too short a duration between its application and mowing can greatly reduce the sugar content of the grass, thereby making it more difficult to preserve as baled silage. Where slurry is applied in spring, it should only be applied to a short stubble so as to avoid any carryover of contamination with the harvested crop.

Weather: Obviously, drier, sunnier weather is ideal for making silage.

Grass growth stage at harvest: Leafier grass usually has less sugars than very stemmy grass, making it more difficult to preserve.

Therefore, successful wilting is particularly essential when making baled silage with leafy grass.

Wilting: Wilting is a routine part of aiding the preservation of baled silage, and important guidelines here are –

(a) Don’t mow the crop until after the dew has evaporated — this will remove about 2.5 tonnes water per hectare (1 tonne per acre), (b) Solar radiation is the main factor that then wilts mown grass, so the more grass surface that is exposed to direct sunshine during wilting the better.

Thus, whereas tedding is the ideal solution, placing the mown grass in wide rather than narrow windrows (eg 67 rather than 50% ground cover) will result in more effective wilting (Table 1).

Air-free storage of the bale: This is the single most important step, and is dealt with below.

MOULD/YEAST-FREE

All baled silage needs to be free of visible growth of mould/yeast. This means that the air-free seal that is needed to permit good preservation must be fully maintained through to feed-out.

Important steps to achieve air-free conditions include:

*This article was first published on 30 April 2011.