By Karen Stewart, SAC Consulting, nutritionist

Forage and feed planning for the winter may not be at the forefront of your mind during the busy summer months, but a little time spent planning now could save lot of hassle and lost revenue later in the season. Predicting what the winter holds is anyone’s guess, but what you can do now is estimate supply and demand of feed to make the most of what you have on farm.

Why start your forage and feed planning now?

1. Peace of mind that you have enough and knowing roughly what your costs for the winter will be

2. Early detection of shortfalls allows for effective action to be taken in plenty time

3. Reduces the risk of sudden diet changes at critical times i.e. coming up to calving

4. Make the most of what you have on the farm – minimising bought in feed and additional costs

Analysing your silage/hay is the best place to start, as well as doing a stock take of the forage available on the farm – whether it’s pit silage, hay/silage bales, or a combination of both. As well as energy and protein, dry matter (DM) content of forages is particularly important for working out rations.

For example, to show the importance of dry matter, take two bales of silage both weighing 750kg and both the same quality, except the dry matter of one is 25% and the other is 45%. If we assume a dry suckler cow eats 10kg of dry matter a day then the first bale would feed 18 cows and the second bale would feed 33 cows. That’s a big difference.

The same theory also applies for energy – 10kg of dry matter of a 9ME silage is 90MJ energy supplied, and 10kg of dry matter of an 11ME silage is 110MJ supplied, the latter being too much for an already fit suckler cow which will gain weight – around 0.5kg/day.

For growing and finishing stock, use the best quality forage available on the farm to reduce bought in concentrates. If your silage is not as good as you had hoped, then ration planning to make up the energy gap with other feeds will ensure cattle still meet specifications and avoid keeping them longer than expected.

Example: keeping weaned calves over the winter to sell store in the spring:

If your silage is poorer than you’d hoped, and this is not taken into account, then you may only get 0.7kg gain on a ration that is normally fed. Over 150 days this could reduce the sale weight by 45kg – around £100/head less at current market prices. This could be easily solved by feeding an extra 1.5kg of barley at a cost of around £30/head over the course of 150 days.

On the other hand, if this season’s silage crop is better than you think, there are savings to me made on bought-in feed.

Estimating quantity of silage on farm

How to measure a silage pit – Silage (t) = length x width x height x density

Length, width and height of the pit are measured in metres and assume the ramp is half the pit height and add this on. Density is dependent on the DM of the forage and can be worked out using this formula: Density (t/m3) = 6.5/DM(%) + 0.4.

Table 1 below shows an example of this:-

DM% Grass silage density (FW t/m3)

20 0.73

25 0.66

30 0.62

Table 1

Example Silage pit calculation

A pit of 30 x 15 x 2.5m with silage a DM of 25%

Density = 6.5/25+0.4=0.66t/m3

Silage(t fresh weight) = 30 x 15 x 2.5 x 0.66 =743t

Silage DM(t) = 743t x 25/100 =186t

Silage Bales

Weigh a few representative bales (they will probably between 500-750kg per bale depending on size, density and dry matter).

No. of bales x weight of bale x dry matter/100 = tonnes DM

A percentage allowance should also be made for spoilage (the bits that will not be eaten).

The graph below shows the range in dry matter (DM) of the silages that we have had into the laboratory so far, the range is 150g/kgDM (15%DM) to 700g/kgDM (70%DM).

* The ‘Forage and Feed Planning Factsheet’ is a helpful resource providing guidance on carrying out a step-by-step forage and feed budget for your farm. This can be found on the Farm Advisory Service website using the following link:

It is well worth a couple of hours spent on a dreich day. If you need a hand, contact your local SAC office.