Forage being harvested
Dry Matter Intake
Dry Matter (DM) intake was found to be higher for silages that achieved the target DM content for ensiling more quickly (see Figure 6.6). Producers should aim for a wilting period of less than 48 hours. Where wilting is extended, the intake of wilted silage will not differ greatly from the unwilted silage.
An extended wilt will increase loss of forage quality (ME) and could cause total ME intake to be reduced for wilted compared to unwilted silages.
A survey of 140 dairy farms in western Victoria (summarised in the box below) found that the average time taken to wilt was 3-6 days and the average DM content of the forage at ensiling was 45.5%. The length of wilt was longer for baled systems compared with chopped silage in order to achieve a higher DM content.
These results highlight that the majority of producers in this survey may be overwilting and that wilting period is much too long. These producers are likely to be suffering production losses.
Final Dry Matter content
As a general rule, for forages within the recommended Dry Matter (DM) range, DM intake increases with DM content. At high DM contents (>55%), additional field losses may reduce the silage ME content. As a result, there may be no further increase or even a relative decline in DM intake (see Figure 6.7).
If wilting is ineffective and there is little increase in DM content, intake will be very similar or less than that of unwilted silage produced from the same forage.
Silage fermentation quality
Where the unwilted silages were poorly preserved, as indicated by a high ammonia-N content, or where the unwilted silage contained significant amounts of acetic acid, the increase in intake due to wilting was greater. Temperate grasses contain more Water Soluble Carbohydrate (WSC) than legumes or legume-dominant crops and pastures, or tropical species.
The increase in intake due to improved silage fermentation quality is likely to be greater with low WSC content forage.
A rapid wilting rate is necessary to maximise the potential benefits of wilting. A number of management strategies and mechanical processes are available to increase wilting rate. They can be used independently or in combination.
