Water damaged feed
How does weather damage affect silage production?
Cloudy skies, cool temperatures, high humidity, no breeze, heavy dews and rainfall typify poor wilting conditions.
They lead to significant increases in field losses (see Figure 6.12) and increased growth of undesirable moulds, bacteria and yeasts in the swath before harvest. A large proportion of the Water Soluble Carbohydrate (WSC) content may also be lost during respiration. If ensiled at low Dry Matter content, as a salvage operation, this loss of fermentable substrate may result in a poor fermentation and unpalatable silage.
As well as slowing wilting rate, rainfall can also cause direct losses of DM and nutrients due to leaching, leaf shatter and increased mechanical losses if additional tedding/raking operations are required.
The ryegrass was tedded to increase drying rate, and the total number of tedding operations increased with deteriorating weather conditions.
The losses would have included direct losses due to rainfall, increased respiration loss and mechanical loss, but did not take into account the likely decline in energy content (ME) of the remaining Dry Matter. These studies showed that the length of the wilting period more than doubled and total Dry Matter losses rose 25% when there was only a small amount of rain on one day.
Significant rainfall, where rain fell on more than one day, led to a more than four-fold increase in the length of wilting period, and DM losses doubled.
Table 6.8 shows the effect of rainfall over 24 hours and crop maturity on DM losses in lucerne/red clover hay. Leaf loss, and leaching and respiration losses, rose substantially from no rain to 63 mm rain. The losses were highest in the less mature crops (bud stage) due to their higher proportions of soluble nutrients.
The same trends are likely with raindamaged lucerne silage, although the extent of losses are likely to be less. Mown forage lying in a narrow swath absorbs less moisture than material in wide swaths. However, the wide swaths are quicker to dry out after the rain stops.
Although not always practical, if rain is imminent, the mown material should be windrowed to reduce moisture uptake. The windrows should be spread out after the rain stops to increase the rate of drying. Crops which have been conditioned or tedded soon after mowing will re-absorb more moisture after rainfall than an unconditioned swath.
The tedding and conditioning operations aim to maximise the drying rate to reduce Dry Matter and quality losses, and to greatly reduce the time the crop is at risk or exposed to rainfall before harvest.
However, there will be occasions when the tedded and conditioned forage will be rain affected, increasing DM and quality losses.
