Silage quality impact on production

A typical dairy farm in Western Australia will import a significant quantity of grain to ensure that the genetic potential for milk can be realised from high genetic merit Friesians/Holsteins.

While grains can generally be more predictable in terms of the energy and protein content, apart from lupins, this is not the case for conserved pasture silage.

The quality of the forage and fodder can also affect the profitability of feeding as well as the levels of imported grain needed to maintain milk production.

The importance of silage quality

Data from Top Fodder’s Successful Silage manual indicates a huge variation of between 5.2 per cent and 25.1 per cent crude protein across 321 grass silage feed tests.

Similarly, energy content varied from 6.7-11.1 MJ ME/kg DM and DM digestibility varied from 48.0 per cent to 76.7 per cent.

If these variations are not factored in the ration formulation, there is not only the potential reduction in milk production but the possible lower financial returns on feed.

A generalised assessment of the impact on silage quality in the WA dairy industry shows that the effect of feeding silage at 9.5 MJ ME/kg DM versus 11 MJ ME/kg DM on milk production can be around 14 per cent if no changes were made to the ration.

This assessment has not factored in the truth that poor quality silage is less digestible than good quality silage on a DM basis and this will have a negative effect on the daily dry matter intake which will further impact milk production.

Factors affecting silage quality

Figure 12.1 in the Successful Silage manual shows the factors affecting silage quality starting with the quality of the parent material.

The 2021/22 season in WA saw good rainfalls into November for most dairy regions.

The positive benefit of a longer grazing period was offset to some degree by the lateness of harvesting of the parent material for silage.

The plants were more mature in their heading stage which comes with a higher lignin content and reduced quality and digestibility.

If nothing is done to compensate for this reduced quality in the ration, then milk production will be affected.

The likely scenario is to offset poor-quality silage by feeding more grain. The cost of this extra grain will affect the bottom line.

General considerations

• Firstly, the Successful Silage manual recommends feed testing the parent material prior to cutting to have an early indication of what effect this might have on the ration and decisions made early to prepare for this.

• Secondly, it is important to test the silage at the end of the fermentation period for a more accurate picture of quality so that the necessary adjustments can be made to the ration.

• The practice of sorting the silage according to quality (the ‘ABC’ approach) so that early lactation cows can be preferentially fed is also a sound recommendation.

For further information, visit Farm Hub.

By Rob La Grange, Western Dairy