Silage Advice

Harvesting grass silage

How short should grass be chopped for silage?

Chopping makes it easier to compact grass in the clamp, which is especially important for more fibrous crops and crops of higher dry matters (DMs), in order to reduce losses from heating. Chopping also releases sugars for fermentation. However, it is important not to overdo it.

The move to higher %DM grass, as well as feeding more maize and wholecrop cereals in dairy rations, has led to concerns about low butterfats due to there being insufficient effective fibre in the diet.

In general, chop length should be adjusted to %DM.

Example chop lengths for grass according to % dry matter



Chop Length (cm)





effective fibre



slippage, effluent


Where grass is cut younger and leafier (e.g. in a multi-cut system) a longer chop length may be needed in order to prevent slippage in the clamp (see multi-cut section). For example, for young and leafy material at 32% DM, consider a chop length of 3-5cm. If it is 28-30% DM consider a 5cm chop length minimum. If it is below 28% DM then consider increasing even further e.g. up to 10cm for grass at 22% DM.