DARD Management Notes: Dairying

This silo is full but how much silage is in it?
This silo is full but how much silage is in it?
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Calculate your forage requirements: Estimate the tonnage of silage available on your farm and compare this with the likely winter demand.

To calculate the volume of silage multiply the length of the silo by the width by the height. The volume of silage in the silo photographed below is calculated by multiplying 38 m (length) by 10m (width) by 3m (height). This equals 1140 cubic metres of silage. Use the conversion factors in Table 1 to convert the volume of silage to tonnes.

Table 1: Conversion factors to convert silage volume to tonnes of silage

Table 1: Conversion factors to convert silage volume to tonnes of silage

Table 1: Conversion factors to convert silage volume to tonnes of silage

For our example, assuming the dry matter (DM) of the silage is 25 per cent multiply the volume by 0.68. This equals 775 tonnes of fresh silage (1140 cubic metres x 0.68).

Table 2: Estimated monthly feed requirement of stock eating 25 per cent dry matter silage

Use the silage requirement figures in Table 2 to estimate the demand for silage.

Table 2: Estimated monthly feed requirement of stock eating 25 per cent dry matter silage

Table 2: Estimated monthly feed requirement of stock eating 25 per cent dry matter silage

Multiply the number of each type of stock by the number of months to be fed by the monthly silage requirement. For example 80 cows in milk fed for seven months require 784 tonnes (80 cows x seven months x 1.4 tonnes per month).

Get your silage tested

At low milk price efficiency is critical. Get your silage analysed so you know its potential feed value (M+). This allows you to make decisions on the level of concentrates needed. Table 3 shows the difference in concentrate needed to feed a cow in early lactation with average and good quality silages.

Table 3: Feed requirement for 32 kg of milk

Table 3: Feed requirement for 32 kg of milk

Table 3: Feed requirement for 32 kg of milk

For a wagon mix of silage and concentrates each kilogramme of concentrate in the mix adds approximately 2.25 kg of milk to the silage M+ figure giving a combined M+ for the ration.

I like feeding cows to yield. Try to produce close to the silage M+ and top up the additional required for the cows yield. Each kilogramme of milk over the silage or ration M+ figure requires 0.45 kg of additional concentrate. Cows should be grouped for feeding. My preference is:

Group 1 - highest yielding/early lactation group (cows giving more than 28 kg milk or less than 150 days in milk.)

Group 2 - lowest yielding/late lactation group (cows giving less than 28 kg milk or more than 150 days in milk).

Set the amount of concentrates fed per cow in the wagon to suit the lowest yielding cow in the group. The lowest yielding group does not always require blend in the wagon if parlour feeding is also taking place on the farm. Good quality (M+12) silage and up to 7.0 kg daily of parlour feed allows cows with yields of 28 kg of milk to be managed satisfactorily without extra concentrate in the wagon. The same silage requires 7.0 kg of concentrates in the wagon to support a base production of 28 kg in the high yield group with cows yielding more than 28 kg of milk being topped up in the milking parlour. As heifers eat 25 per cent less than mature cows top up from 21 kg.

Move cows between groups as their yield declines. Cows more than 150 days in milk no longer producing 28 kg of milk must be moved to the low yield group. At this stage they may receive a greater proportion of their concentrate in the parlour than before, but it is important that cows in late lactation are not over fed, in order to maximize efficiency this winter.

Check the calibration of all concentrate feeders is correct. Also the filling and mixing of concentrates in the feeder wagon requires an experienced operator working on a consistent basis to avoid feeding unplanned concentrates. A monthly audit of concentrate fed against expected feed level will give you a running guide on their accuracy.

For further information contact your local CAFRE Development Adviser.