A cow enjoying some silage
What factors affect the rate of silage feed-out?
The rate of silage feed-out determines the time the silage at and near the feeding face is exposed to air. It also determines the extent of aerobic spoilage losses.
A German study investigated the effects of rate of feed-out and silage porosity on the loss of nutrients from silages of varying susceptibility to aerobic spoilage (see Figure 10.1).
Dry Matter losses and losses in nutritive value (the loss in net energy for lactation, MJ/kg DM in this case) were combined to calculate the total loss in nutrients (%) due to aerobic spoilage.
Nutrient losses calculated in this way were 40-70% higher than the Dry Matter (DM) losses. Both temperature and nutrient losses increased as air penetration increased and when feed-out rate was slower.
Where significant heating of the silage occurs, DM and quality losses can be high (see Figures 10.1 and 10.2).
In both European and American studies, DM losses of up to 3.5-4.0% per day have been observed. Studies on dairy farms in the United States have confirmed that losses are higher when feed-out rate is slow.
With good silage management during filling and removal, a feed-out rate of at least 15 cm/day will usually minimise aerobic spoilage losses in bunkers and pits.
However, a rate of at least 30 cm/day is recommended with unstable silages, such as maize. This may need to be increased during warmer weather. This higher rate is certainly justified by the results in Figure 10.1.
The surface area of the feeding face required to achieve the target feed-out rate can be calculated from the quantity of silage fed per day and the density of silage in the bunker or pit. For baled silage stored in stacks, producer experience indicates that the removal of one layer of bales from the feeding face over two days will usually minimise aerobic spoilage.
