Wilting is the process where moisture evaporates from the mown forage to increase DM content to the desired level for harvesting.
To minimise losses (DM and quality) the mown material must be wilted as quickly as possible to the target DM content . Ideally, wilting should take no longer than 48 hours.
The longer the wilting period needed to achieve the target DM content, the more extensive the DM and quality losses due to continued plant respiration and microbial (bacterial and mould) attack. The risk of rain will also increase.
Wilting beyond the target DM content also results in higher quality and DM losses due mainly to leaf loss before and during harvest
Weather conditions directly affecting wilting rate.
Warm days with low humidity and extensive periods of solar radiation (sunlight), accompanied by wind, result in the fastest rates.
During cool, overcast weather, when the humidity is high, wilting rates are slowest because of low evaporation rates. Weather conditions also affect loss of forage DM and quality during the wilting period.
Wilted silages are usually more palatable and result in greater animal intakes than unwilted silages produced from the same forage. However, whether or not animal production is improved will depend on the length of time taken to wilt the forage
The effect of wilting on animal production
In a number of overseas studies, the effects of wilting on animal production have been variable. There have been no similar studies in Australia.
A large number of studies in Europe have compared unwilted and wilted silages produced from the same crop. Most silages studied were produced from perennial ryegrass pastures, although some contained other grasses or white clover.
These results suggest that the benefits of wilting were inconsistent, and it did not guarantee any improvement in liveweight gain or milk production.
However, it was found that achieving animal production benefits from wilting, as indicated by increased intake, depended on three main factors – wilting rate, final DM content and silage fermentation quality.