Planning for Silage Making 2025

24 April 2025

Planning for winter feeding starts now, and with that in mind it’s important to know what your target is. You should already have an idea of the what the quality will be before the silage is actually analysed. Consider what stock you have on farm and target the quality of your silage for what you have. This article will go through some of the methods you can use to ensure you’re in a good position come winter.

Know what quality silage best suits your stock

High quality silage (>11 MJ of ME kg/DM and >12% DM crude protein), is best suited to growing/finishing stock, pregnant ewes, heifers calving at 2 years old and autumn calvers. While a bulkier, lower quality silage tends to suit dry suckler cows in good condition.

Table 1: Cutting stage for quality of silage

Silage quality (energy)	Grass ear emergence	Suitable stock
9.5MJ/kgDM	75%	Fit dry suckler cows
10.5MJ/kgDM	50%	Growing stock, autumn calving cows, pregnant ewes
11.5MJ/kgDM	25%	Growing stock, finishing stock, pregnant ewes

For youngstock and ewes pregnant with multiples:

Set your cutting date

Once you know the quality of silage you are aiming for, the next consideration should be timings. For high producing animals you want to aim for high digestible, high protein silage to maximise performance from forage and reduce bought- in feeds.

Digestibility is correlated to amount of live leaf on the grass, as you can see as the plant matures the proportion of stem and dead material increases, reducing the digestibility.

Image 1 below shows how the composition of fresh grass changes over time.

Consequences of delaying cutting by 1 week:

Digestibility decreases by 3.5% (0.5 unit/day from when grass starts to push up flowering stems)
Metabolisable energy (ME) reduces by 0.6 MJ/kg DM
Dry matter yield increases by around 10%

Image 1: Effect of maturity on grass composition

silage - effect of maturity on grass composition

When nitrogen is applied affects the optimal date for cutting silage. If fertiliser is applied too close to the cutting date, then problems can occur in the fermentation process, leading to poor quality silage.

The target level for grass at cutting is below 0.1% (1000 mg/kg fresh weight) nitrate-N.

One method to estimate when all nitrogen has been utilised by the crop, is to work out the nitrogen uptake per day from the date of application. Table 2 assumes an N uptake of 2.5kg/ha (2 units/acre) per day from the date of application. This is assuming active uptake, therefore a safety of + 7 days could be applied if conditions are unfavourable.

Table 2: Level of N kg/ha in the soil:

N rate kg N/ha	Weeks after N application
	1	2	3	4	5	6	7
60	42.5	25	7.5	0
80	62.5	45	27.5	10	0
100	82.5	65	47.5	30	12.5	0
120	102.5	85	67.5	50	32.5	15	0

From the table you can see at an application rate of 60 kg N/ha all the nitrogen is utilised by 4 weeks post application. In comparison with a dressing of 120 kg N/ha all the nitrogen is utilised by 7 weeks post application (assuming optimal conditions).

Another way to ensure nitrate-N levels of the grass is below the target level of 0.1% is by using test strips for nitrates, these can be purchased online and the test performed on farm or by sending grass samples to a lab for analysis.

Mary Young, Ruminant Nutritionist, SAC Consulting, mary.young@sac.co.uk