Silage quality vs quantity during drought

Drought conditions force tough decisions on silage making. With reduced growth, farmers face a dilemma: wait for more bulk and risk poor feed quality or cut early and risk not having enough forage. Explore how drought affects grass and how to strike a balance between yield and feed value.

During dry conditions, grass plants become stressed. Growth slows down as plants conserve moisture, and less energy goes into leafy biomass production.

Key effects to be aware of:

• Lower yields due to reduced tillering and sward height, especially in rye-grass-dominant leys
• Higher dry matter (DM), with grass often reaching over 35% DM while still short
• Reduced digestibility (D-value) as older leaves dominate when cutting is delayed
• Water-soluble carbohydrate (WSC) levels may be high, but fermentation can still be limited if protein or moisture is lacking

In practice, waiting for more bulk may result in poorer-quality silage, with lower energy and protein content. This is a particular risk for milking cows or youngstock.

In a dry year, it’s usually better to prioritise quality over yield, especially for priority stock groups:

• Cut earlier to capture energy-rich leaf while it’s still digestible
• Don’t be fooled by short swards; DM may already be high, and grass may be ‘burning off’ rather than growing
• Watch for seed heads, as their appearance signals a rapid decline in quality

Use a rising plate meter or quadrat cuts to assess yield and act decisively.

Not all fields respond the same way to drought. Tailor your strategy to field type and species mix.

Fields suited to early cutting include newer leys with good rye-grass content, where WSC levels are usually higher.

Swards with visible seed heads should also be prioritised as quality will decline quickly.

Fields with even regrowth tend to cut and wilt more reliably, even if the yield is low.

In contrast, some fields are better delayed or grazed. These include drought-hardy mixes such as cocksfoot, timothy, or deep-rooted herbs like chicory and plantain.

Patchy or scorched areas may need time to recover or could be rested and grazed later.

Cutting early means less silage in the clamp. But with better quality, you may need to feed less per head, balancing the shortfall.

Actions to take:

• Recalculate forage demand based on new cutting date and estimated yield
• Test silage early, around six weeks after ensiling, to analyse DM, metabolisable energy (ME), protein and intake potential
• Use a mix of forage types, such as second cut, straw, whole crop or purchased feeds if needed
• Explore fast-growing alternatives, such as stubble turnips, forage rape, westerwolds or hybrid rye-grasses for late summer feed

Grass is already dry, so avoid over-wilting. Aim for around 28–32% DM. Tedding within 4 hours of mowing can help, especially in low humidity.

Use homofermentative inoculants to improve fermentation in dry, low-sugar or low-protein crops.

Molasses or acid-based products may help if there’s a risk of poor fermentation.

Raise cutting height to 6–8 cm to reduce contamination and encourage quicker regrowth if moisture returns.

Prioritise high-quality drought silage for:

• Lactating dairy cows – especially high-yielding groups
• Finishing lambs or youngstock – where daily liveweight gain is key
• Ewes in late pregnancy or early lactation – when energy demands peak

Lower-quality silage, such as wetter second cuts or stemmier grass, can be given to dry cows, store cattle or ewes mid-gestation, provided mineral and protein balance is maintained.