Calculating Silage Stocks

The quantity of silage within a clamp can be estimated by multiplying the volume of the silage in the clamp by the approximate density of the silage.

The volume of the clamp can be calculated as: Length x Breadth x Height. If a ramp is there, halve it, and measure the length as one distance where the silage is the same height, plus half the distance of the ramp. (Basically turning half of the ramp upside down, and stacking it on top of the other half, to make a square for measurement purposes.)

Grass Silage Quality, kgs per cubic metre

Multiply pit length x pit width x pit height x kgs per cubic metre as per table ÷ 1000 = TONNES IN PIT approx.

If you wish to know the total Dry matter available you should multiply the cubic metres available by the following factors dependant on the dry matter of the silage.

Dry Matter % **

• 20 multiply by 0.77 = total tonne of dry matter
• 25 multiply by 0.68 = total tonne of dry matter
• 30 multiply by 0.60 = total tonne of dry matter

The silage density will vary according to dry matter, chop length, crop type, compaction, but grass silage will generally fall in to a range of 600 - 700 Kgs per Cu Metre, maize silage probably 700 to 850 Kgs per Cu Metre. (these values converted to decimals are 0.6,0.7,0.7, 0.85)

The overall quantity of silage can then be divided by the number of cows and number of days remaining in winter, or longer if buffer feeding us required, to determine the maximum quantity that can be fed per head per day. When doing this calculation, be sure to allow for any quantities of silage required for feeding any animals outside of the milking herd, e.g. heifers, dry cow etc.

** You need 1¾ tonnes of Dry Matter per milking cow for a 180 day winter. You need 1 tonne of Dry matter per dry cow for a 180 day winter (Plus Youngstock and / or Beef animals)

If this table and equations are as clear as mud, please ring one of our agents to assist you in working out you own individual stocks available.