While rainfall has arrived in the east and south east there are still major challenges facing many farmers in building grass supplies and coping with a winter forage deficit.

There is a perception that there is surplus forage in the west and northern half of the country but speaking with farmers at the joint Milford Mart and Teagasc suckler event last week in Donegal this may not be the case. Many farmers estimate that forage supplies may be aligned with requirements.

It is worth all farmers, irrespective of location, completing a forage budget to gauge supplies. The earlier that this is completed then the more time that is available to put plans in place.

Table 1 details a worksheet for calculating the volume of silage required by different stock. The calculations are based on a tonne of pit silage at 25% dry matter. Tables 2 and 3 are useful to calculate the volume of hay and straw available.

A dry suckler cow will eat about 13kg to 15kg hay (@85% DM), rising to 16kg to 19kg for lactating cows. Weanlings weighing around 300kg will eat 7kg to 8kg of freshweight hay with heavier cattle similar to cows unless supplemented heavily with concentrates.

Silage supply

To calculate the volume of feed in a pit multiply the length by the breath by the average height. This will give you a volume in m3. This needs to be diverted to tonnes os silage.

Where the dry matter is 25% then multiply by 0.68. If silage is very wet, say 18%, then multiply by 0.81 and for 20% DM multiply by 0.77 to get the volume of silage in tonnes.

To convert the volume of silage in a typical round bale to pit silage then the calculation is typically the weight of the bale multiplied by 0.9. This can be reduced to 0.8 for silage at less than 30% dry matter and 0.65 for silage aftergrass or silage of a low dry matter.

Stretching supplies

As a general rule, 1kg concentrates can replace 5kg to 7kg silage depending on the feed value. For this to work there has to be an ability to restrict feed as offering concentrates along with silage will not replace silage – it will just increase intake.

Cattle fed on high concentrate diets typically require 10% to 12% of their diet as a fibre source which translates to about 1kg to 1.5kg straw or hay daily.